Skip to main content

Full text of "To see the unseen : a history of planetary radar astronomy"

See other formats 


Skf 

'  • 


A  History  of  Planetary  Radar  Astrononr 


Andrew  J.  Butrica 


To  See 

the 
Unseen 


A  History  of 
Planetary  Radar  Astronomy 


The  past  50  years  have  brought  forward  a  unique  capa- 
bility to  research  and  expand  scientific  knowledge  of 
the  Solar  System  through  the  use  of  radar  to  conduct 
planetary  astronomy.  This  technology  involves  the  aim- 
ing of  a  carefully  controlled  radio  signal  at  a  planet  (or 
some  other  Solar  System  target,  such  as  a  planetary 
satellite,  an  asteroid,  or  a  ring  system),  detecting  its 
echo,  and  analyzing  the  information  that  the  echo  car- 
ries. 

This  capability  has  contributed  to  the  scientific  knowl- 
edge of  the  Solar  System  in  two  fundamental  ways. 
Most  directly,  planetary  radars  can  produce  images  of 
target  surfaces  otherwise  hidden  from  sight  and  can 
furnish  other  kinds  of  information  about  target  surface 
features.  Radar  also  can  provide  highly  accurate  mea- 
surements of  a  target's  rotational  and  orbital  motions. 
Such  measurements  are  obviously  invaluable  for  the 
navigation  of  Solar  System  exploratory  spacecraft,  a 
principal  activity  of  NASA  since  its  inception  in  1958. 

Andrew  J.  Butrica  has  written  a  comprehensive  and 
illuminating  history  of  this  little-understood  but  sur- 
prisingly significant  scientific  activity.  Quite  rigorous 
and  systematic  in  its  methodology,  To  See  the  Unseen 
explores  the  development  of  the  radar  astronomy  spe- 
cialty in  the  larger  community  of  scientists. 

More  than  just  discussing  the  development  of  this 
field,  however,  Butrica  uses  planetary  radar  astronomy 
as  a  vehicle  for  understanding  larger  issues  relative  to 
the  planning  and  execution  of  "big  science"  by  the 
Federal  government.  His  application  of  the  "social 
construction  of  science"  and  Kuhnian  paradigms  to 
planetary  radar  astronomy  is  a  most  welcome  and 
sophisticated  means  of  making  sense  of  the  field's 
historical  development. 

Andrew  J.  Butrica  received  his  Ph.D.  in  the  history  of 
science  and  technology  at  Iowa  State  University.  He  is 
a  research  historian  in  Franklin  Park,  New  Jersey,  spe- 
cializing in  the  history  of  science.  In  1990,  Praeger 
Publishers  issued  his  Out  of  Thin  Air:  A  History  of  Air 
Products  and  Chemicals,  Inc.,  1940-1990. 

About  the  cover:  "Big  Dish  Antenna"  painting  by  Paul  Arlt. 
Courtesy  of  the  NASA  Art  Program,  no.  74-HC467. 


WITHDRAWN 


w  (>"Wir  librafl 
AUG  2  9 1996 

U  tf  W^«  i  «  "A    VVM* 


PI 


The  past 
bility  to 
the  Solai 
planetar 
ing  of  a « 
some  ot 
satellite, 
echo,  an 
ries. 

This  cap 
edge  of 
Most  db 
target  si 
furnish 
features 
suremei 
Such  m 
navigati 
principi 

Andrew 
illuminj 
prisingi 
and  sys 
explore 
cialty  ir 

More  t 
field,  h 
as  a  vel 
the  pla 
Federa 
constrv 
planeta 
sophist 
historic 

Andrev 
science 
a  resea 
cializir 
Publisl 
Produc 

About  < 
Courier 


TO  SEE  THE  UNSEEN 


NASASP-4218 


TO  SEE  THE  UNSEEN 


A  History  of  Planetary  Radar  Astronomy 


by  Andrew  J.  Butrica 


The  NASA  History  Series 


National  Aeronautics  and  Space  Administration 

NASA  History  Office 

Washington,  D.C.  1996 


Library  of  Congress  Cataloguing-in-Publication  Data 

To  See  the  Unseen:  A  History  of  Planetary  Radar  Astronomy  /  Andrew  J.  Butrica 
p.  cm.— (The  NASA  history  series)  (NASA  SP:  4218) 

Includes  bibliographical  references  and  indexes. 

1.  Planetology — United  States.  2.  Planets — Exploration.  3.  Radar  in 
Astronomy.       I.  Title.  II.  Series.  III.  Series:  NASASP:  4218. 
QB602.9.B87  1996  95-35890 

523.2'028-dc20  CIP 


For  sale  by  the  U.S.  Government  Printing  Office 

Superintendent  of  Documents,  Mail  Stop:  SSOP,  Washington,  DC  20402-9328 
ISBN  0-16-048578-9 


To  my  dear  friends  and  former  colleagues  at  the  Center  for  Research  in 

History  of  Science  and  Technology:  Bernadette  Bensaude-Vincent, 

Christine  Blondel,  Paulo  Brenni,  Yves  Cohen,  Jean-Marc  Drouin, 

Irina  and  Dmitry  Gouzevitch,  Anna  Guagnini,  Andreas  Kahlow, 

Stephan  Lindner,  Michael  Osborne,  Anne  Rasmussen, 

Mari  Williams,  Anna  Pusztai, 

and  above  all  Robert  Fox. 


Contents 

Acknowledgments iii 

Introduction vii 

Chapter  One:  A  Meteoric  Start 1 

Chapter  Two:  Fickle  Venus 27 

Chapter  Three:  Sturm  und  Drang 55 

Chapter  Four:  Little  Science/Big  Science 87 

Chapter  Five:  Normal  Science 117 

Chapter  Six:  Pioneering  on  Venus  and  Mars 149 

Chapter  Seven:  Magellan 177 

Chapter  Eight:  The  Outer  Limits 205 

Chapter  Nine:  One  Step  Beyond 225 

Conclusion:  W(h)ither  Planetary  Radar  Astronomy? 259 

Planetary  Radar  Astronomy  Publications 267 

A  Note  on  Sources 269 

Interviews 271 

Technical  Essay:  Planetary  Radar  Astronomy 275 

Abbreviations 287 

Index 289 

About  the  Author 297 

The  NASA  History  Series 299 


From  Locksley  Hall 


For  I  dipt  into  the  future, 

far  as  human  eye  could  see, 

Saw  the  Vision  of  the  world, 

and  all  the  wonder  that  would  be; 

Saw  the  heavens  Jill  with  commerce, 

argosies  of  magic  sails, 
Pilots  of  the  purple  twilight, 

dropping  down  with  costly  bales; 

Heard  the  heavens  fill  with  shouting, 

and  there  rained  a  ghastly  dew 

From  the  nations'  airy  navies 

grappling  in  the  central  blue; 

Far  along  the  world-wide  whisper 

of  the  south-wind  rushing  warm, 

With  the  standards  of  the  peoples 

plunging  through  the  thunder-storm; 

Till  the  war-drum  throbbed  no  longer, 

and  the  battle-flags  were  furled 

In  the  Parliament  of  man, 

the  Federation  of  the  world. 

There  the  common  sense  of  most 

shall  hold  a  fretful  realm  in  awe, 

And  the  kindly  earth  shall  slumber, 
lapt  in  universal  law. 

So  I  triumphed  ere  my  passion 

sweeping  through  me  left  me  dry, 
Left  me  with  the  palsied  heart, 

and  left  me  with  the  jaundiced  eye; 

Eye,  to  which  all  order  festers, 

all  things  here  are  out  of  joint: 

Science  moves,  but  slowly  slowly, 

creeping  on  from  point  to  point: 

Alfred  Baron  Tennyson 
(1842) 


Acknowledgments 

Let  me  begin  with  a  confession  and  some  explanations.  Before  beginning  this  project,  I 
knew  nothing  about  planetary  radar  astronomy.  I  quickly  realized  that  I  was  not  alone.  I 
discovered,  too,  that  most  people  confuse  radar  astronomy  and  radio  astronomy.  The 
usual  distinction  made  between  the  two  is  that  radar  astronomy  is  an  "active"  and  radio 
astronomy  a  "passive"  form  of  investigation.  The  differentiation  goes  much  deeper,  how- 
ever; they  represent  two  disparate  forms  of  scientific  research. 

Radio  astronomy  is  more  akin  to  the  methods  of  natural  history,  in  which  observation  and 
classification  constitute  the  principal  methods  of  acquiring  knowledge.  Radio 
astronomers  search  the  cosmos  for  signals  that  they  then  examine,  analyze,  and  classify. 
Radar  astronomy,  on  the  other  hand,  is  more  like  a  laboratory  science.  Experimental 
conditions  are  controlled;  the  radar  astronomer  determines  the  parameters  (such  as  fre- 
quency, time,  amplitude,  phase,  and  polarization)  of  the  transmitted  signals. 

The  control  of  experimental  parameters  was  only  one  of  many  aspects  of  planetary  radar 
astronomy  that  captivated  my  interest,  and  I  gradually  came  to  find  the  subject  and  its 
practitioners  irresistibly  fascinating.  I  hope  I  have  imparted  at  least  a  fraction  of  that 
fascination.  Without  the  planetary  radar  astronomers,  writing  this  book  would  have  been  a 
far  less  enjoyable  task.  They  were  affable,  stimulating,  cooperative,  knowledgeable,  and 
insightful. 

The  traditional  planetary  radar  chronology  begins  with  the  earliest  successful  attempts  to 
bounce  radar  signals  off  the  Moon,  then  proceeds  to  the  detection  of  Venus.  I  have 
deviated  from  tradition  by  insisting  that  the  field  started  in  the  1940s  and  1950s  with  the 
determination  by  radar  that  meteors  are  part  of  the  solar  system.  Meteor,  auroral,  solar, 
lunar,  and  Earth  radar  research,  as  well  as  radar  studies  of  planetary  ionospheres  and 
atmospheres  and  the  cislunar  and  interplanetary  media  are  specializations  in  themselves, 
so  were  not  included  in  this  history  of  planetary  radar  astronomy  in  any  comprehensive 
fashion.  What  has  defined  radar  astronomy  as  a  scientific  activity  has  changed  over  time, 
and  the  nature  of  that  change  is  part  of  the  story  told  here. 

This  history  was  researched  and  written  entirely  under  a  contract  with  the  California 
Institute  of  Technology  (Caltech)  and  the  Jet  Propulsion  Laboratory  (JPL),  as  a  subcon- 
tract with  the  National  Aeronautics  and  Space  Administration  (NASA) .  This  history  would 
not  have  come  into  existence  without  the  entrepreneurial  energies  of  JPL's  Nicholas  A. 
Renzetti,  who  promoted  the  project  and  found  the  money  to  make  it  happen.  It  is  also  to 
his  credit  that  he  found  additional  support  for  a  research  trip  to  England  and  for  atten- 
dance at  a  conference  in  Flagstaff,  as  well  as  for  the  transcription  of  additional  interviews. 
As  JPL  technical  manager,  he  administered  all  technical  aspects  of  the  contract.  I  hope 
this  work  meets  and  exceeds  his  expectations.  During  my  frequent  and  sometimes 
extended  visits  to  JPL,  Nick  provided  secretarial,  telephone,  photocopying  and  other 
supplies  and  services,  as  well  as  a  professional  environment  in  which  to  work.  I  also  want 
to  thank  the  JPL  secretarial  personnel,  especially  Dee  Worthington,  Letty  Rivas,  and  Judy 
Hoeptner,  as  well  as  Penny  McDaniel  of  the  JPL  Photo  Lab,  who  was  so  resourceful  in 
finding  pictures. 


iii 


Teresa  L.  Alfery,  JPL  contract  negotiator,  deserves  more  than  a  few  words  of  thanks. 
Working  out  the  contract  details  could  have  been  an  insufferable  experience,  were  it  not 
for  her.  Moreover,  she  continued  her  cordial  and  capable  performance  through  several 
contract  modifications. 

The  contract  also  came  under  the  purview  of  the  NASA  History  Office,  which  provided  the 
author  office  supplies  and  services  during  visits  there.  More  importantly,  Chief  Historian 
Roger  D.  Launius  offered  encouragement  and  support  in  a  manner  that  was  both  profes- 
sional and  congenial.  It  was  a  pleasure  to  work  with  Roger.  This  history  owes  not  inconse- 
quential debt  to  him  and  the  staff  of  the  History  Office,  especially  Lee  Saegesser,  archivist, 
who  lent  his  extensive  and  unique  knowledge  of  the  NASA  History  Office  holdings. 

I  also  want  to  acknowledge  certain  individuals  who  helped  along  the  way.  Before  this  pro- 
ject even  began,  Joseph  N.  Tatarewicz  afforded  it  a  rich  documentary  source  at  the  NASA 
History  Office  by  rescuing  the  papers  of  William  Brunk,  which  hold  a  wealth  of  informa- 
tion on  the  Arecibo  Observatory  and  other  areas  relevant  to  planetary  astronomy  at 
NASA.  Joe  also  was  a  valuable  source  of  facts  and  wisdom  on  the  history  of  the  space  pro- 
gram and  an  invaluable  guide  to  the  planetary  geological  community. 

This  history  also  owes  a  debt  to  Craig  B.  Waff.  His  extensive  collection  of  photocopied 
materials  greatly  facilitated  my  research,  as  did  his  manuscript  histories  of  the  Deep  Space 
Network  and  Project  Galileo.  Craig  generously  offered  a  place  to  stay  during  my  first 
visits  to  California  and  was  my  JPL  tour  guide. 

The  staff  of  the  JPL  Archives  deserves  an  exceptional  word  of  appreciation.  They  do  not 
know  the  word  "impossible"  and  helped  facilitate  my  research  in  a  manner  that  was  always 
affable  and  competent.  In  particular,  I  want  to  acknowledge  the  director,  Michael  Q. 
Hooks,  for  assembling  a  superb  team,  John  F.  Bluth,  for  his  command  of  the  JPL  oral  his- 
tory collection  and  our  informative  talks  about  JPL  history,  and  Julie  M.  Reiz,  for  her  help 
in  expediting  access  to  certain  collections. 

I  also  wish  to  thank  those  librarians,  archivists,  historians,  and  others  who  expedited  my 
research  in,  or  who  provided  access  to,  special  documentary  collections:  Helen  Samuels 
and  Elizabeth  Andrews,  MIT  Institute  Archives  and  Special  Collections;  Mary  Murphy, 
Lincoln  Laboratory  Library  Archives;  Ruth  Liebowitz,  Phillips  Laboratory;  Richard 
Bingham,  Historical  Archives,  U.S.  Army  Communications-Electronics  Command,  Ft. 
Monmouth,  NJ;  Richard  P.  Ingalls  and  Alan  E.  E.  Rogers,  NEROC,  Haystack  Observatory; 
George  Mazuzan,  NSF  Historian's  File,  Office  of  Legislation  and  Public  Affairs,  National 
Science  Foundation;  Eugene  Bartell,  administrative  director,  National  Astronomy  and 
Ionosphere  Center,  Cornell  University;  Jane  Holmquist,  Astrophysics  and  Astronomy 
Library,  Princeton  University;  and  August  Molnar,  president  of  the  American  Hungarian 
Foundation. 

In  addition,  I  want  to  acknowledge  those  individuals  who  made  available  materials  in  their 
possession:  Julia  Bay,  Bryan  J.  Butler,  Donald  B.  Campbell,  Von  R.  Eshleman,  Thomas 
Gold,  Paul  E.  Green,  Jr.,  Raymond  F.  Jurgens,  Sir  Bernard  Lovell,  Steven  J.  Ostro,  Gordon 
H.  Pettengill,  Nicholas  A.  Renzetti,  Martin  A.  Slade,  and  William  B.  Smith.  Credit  also 
goes  to  those  individuals  who  reviewed  part  or  all  of  this  manuscript:  Louis  Brown,  Ronald 
E.  Doel,  George  S.  Downs,  John  V.  Evans,  Robert  Ferris,  Richard  M.  Goldstein,  Paul  E. 
Green,  Jr.,  Roger  D.  Launius,  Sir  Bernard  Lovell,  Steven  J.  Ostro,  Gordon  H.  Pettengill, 


IV 


Robert  Price,  Alan  E.  E.  Rogers,  Irwin  I.  Shapiro,  Richard  A.  Simpson,  Martin  A.  Slade, 
and  Joseph  N.  Tatarewicz. 

There  are  numerous  people  at  NASA  involved  in  the  mechanics  of  publishing  who 
helped  in  myriad  ways  in  the  preparation  of  this  history.  J.D.  Hunley,  of  the  NASA  History 
Office,  edited  and  critiqued  the  text  before  he  departed  to  take  over  the  History 
Program  at  the  Dryden  Flight  Research  Center;  and  his  replacement,  Stephen  J.  Garber, 
helped  in  the  final  proofing  of  the  work.  Nadine  Andreassen  of  the  NASA  History  Office 
performed  editorial  and  proofreading  work  on  the  project;  and  the  staffs  of  the  NASA 
Headquarters  Library,  the  Scientific  and  Technical  Information  Program,  and  the  NASA 
Document  Services  Center  provided  assistance  in  locating  and  preparing  for  publication 
the  documentary  materials  in  this  work.  The  NASA  Headquarters  Printing  and  Design 
Office  developed  the  layout  and  handled  printing.  Specifically,  we  wish  to  acknowledge 
the  work  of  Jane  E.  Penn,  Patricia  Lutkenhouse  Talbert,  Kimberly  Jenkins,  Lillian  Gipson 
and  James  Chi  for  their  design  and  editorial  work.  In  addition,  Michael  Crnkovic,  Craig 
A.  Larsen,  and  Larry  J.  Washington  saw  the  book  through  the  publication  process. 

Finally,  I  want  to  recognize  the  friendship  of  fellow  cat  lover  Joel  Harris,  the  cordial  and 
entertaining  SETI  evening  spent  at  the  Griffith  Observatory  with  Mike  Klein,  Judy 
Hoeptner,  and  company  (without  forgetting  the  Renaissance  Festival!),  the  stimulating 
conversations  with  Adrienne  Harris,  and  the  friendly  folk  dancers  of  Pasadena,  as  well  as 
the  contra  dancers  of  Highland  Park  and  Franklin  Park,  and  Ghislaine,  the  most  impor- 
tant one  of  all  in  many  ways. 


Introduction 

Planetary  radar  astronomy  has  not  attracted  the  same  level  of  public  attention  as,  say,  the 
Apollo  or  shuttle  programs.  In  fact,  few  individuals  outside  those  scientific  communities 
concerned  with  planetary  studies  are  aware  of  its  existence  as  an  ongoing  scientific 
endeavor.  Yet,  planetary  radar  has  contributed  fundamentally  and  significantly  to  our 
knowledge  of  the  solar  system. 

As  early  as  the  1940s,  radar  revealed  that  meteors  are  part  of  the  solar  system.  After  the 
first  detections  of  Venus  in  1961,  radar  astronomers  refined  the  value  of  the  astronomical 
unit,  the  basic  yardstick  for  measuring  the  solar  system,  which  the  International 
Astronomical  Union  adopted  in  1964,  and  they  discovered  the  rotational  rate  and  direc- 
tion of  Venus  for  the  first  time.  Next,  radar  astronomers  determined  the  correct  orbital 
period  of  Mercury  and  calculated  an  accurate  value  for  the  radius  of  Venus,  a  measure- 
ment that  Soviet  and  American  spacecraft  had  failed  to  make  reliably.  Surprisingly,  radar 
studies  of  Saturn  revealed  that  its  rings  were  not  swarms  of  minute  particles,  but  rather 
consisted  of  icy  chunks  several  centimeters  or  more  in  diameter.  Planetary  radar  also  pro- 
vided further  proof  of  Albert  Einstein's  theory  of  General  Relativity,  as  well  as  the  "dirty 
snowball"  theory  of  comets.  The  only  images  of  Venus'  surface  available  to  researchers  are 
those  made  from  radar  observations.  The  ability  of  planetary  radar  astronomy  to  charac- 
terize the  surfaces  of  distant  bodies  has  advanced  our  general  knowledge  of  the  topogra- 
phy and  geology  of  the  terrestrial  planets,  the  Galilean  moons  of  Jupiter,  and  the  aster- 
oids. The  Viking  project  staff  utilized  radar  data  to  select  potential  landing  sites  on  Mars. 
More  recently,  radar  revealed  the  surprising  presence  of  ice  on  Mercury  and  furnished 
the  first  three-dimensional  images  of  an  asteroid. 

Again,  these  achievements  seldom  have  attracted  the  attention  of  the  media.  The  initial 
American  radar  detections  of  the  Moon  in  1946  and  of  Venus  in  1961  attracted  notice  in 
daily  newspapers,  weekly  news  magazines,  news  reels,  and  cartoons.  Only  in  recent  years 
have  the  accomplishments  of  radar  astronomy  returned  to  the  front-page  of  the  news.  The 
images  of  Venus  sent  back  by  Magellan  received  full  media  coverage,  and  images  of  the 
asteroid  Toutatis  appeared  on  the  front-page  of  the  New  York  Times. 

Planetary  radar  astronomy  has  shared  its  anonymity  with  other  applications  of  radar  to 
space  research.  The  NASA  radar-equipped  SEASAT  satellite  provided  unprecedented 
images  of  Earth's  oceans;  European,  Canadian,  and  Japanese  satellites,  as  well  as  a  num- 
ber of  space  shuttles,  have  imaged  Earth  with  radar.  The  radars  of  NASA's  Deep  Space 
Network  also  have  played  a  major  role  in  tracking  space  launches  and  spacecraft  on  route 
to  planets  as  distant  as  Saturn  and  Neptune.  Among  the  more  down-to-Earth,  visible  and 
even  pervasive  applications  of  radar  are  those  for  air  traffic  control  and  navigation,  the 
surveillance  of  automobile  traffic  speeds,  and  the  imaging  of  weather  patterns  reported 
daily  on  television  and  radio. 

Planetary  radar  astronomy  is  part  of  the  great  wave  of  progress  in  solid-state  and  digital 
electronics  that  has  marked  the  second  half  of  the  twentieth  century.  For  instance,  the  ear- 
liest planetary  radar  experiment  marked  the  first  use  of  a  maser  (a  solid-state  microwave 
amplifying  device)  outside  the  laboratory.  Although  radio  astronomy  has  long  claimed  the 
first  maser  application  for  itself,  namely  in  April  1958  by  Columbia  University  and  the 
Naval  Research  Laboratory,  two  months  earlier,  MIT's  Lincoln  Laboratory  used  a  maser 
in  its  first  attempt  to  bounce  radar  waves  off  Venus.  The  same  radar  experiment  also  saw 


vii 


one  of  the  first  uses  of  a  digital  tape  recorder,  as  well  as  the  incorporation  of  a  digital  com- 
puter and  other  digital  data  processing  equipment  into  a  civilian  radar  system. 

The  origins  of  this  solid-state  and  digital  electronics  progress,  as  well  as  of  planetary  radar 
astronomy,  are  rooted  in  electronic  research  and  development  that  started  as  early  as  the 
1930s.  The  first  radar  astronomy  experiments,  which  were  carried  out  on  meteors  and  the 
Moon  in  the  1940s,  relied  on  equipment  designed  and  built  for  military  defense  during 
World  War  II  and  were  based  on  research  conducted  during  the  1930s. 

Planetary  radar  astronomy,  and  so  too  radar  itself,  had  its  origins  in  Big  Science.  British 
war  preparations  during  the  1930s  concentrated  large  amounts  of  scientific,  technologi- 
cal, financial,  and  human  resources  into  a  single  effort.  Part  of  that  effort  was  a  massive 
radar  research  and  development  program  that  produced  an  impressive  range  of  defensive 
and  offensive  radars.  In  a  secret  mission  known  only  at  the  highest  levels  of  government, 
Britain  gave  the  United  States  one  of  the  key  devices  born  of  that  large-scale  radar  effort, 
the  magnetron.  In  turn,  the  magnetron  formed  the  technological  base  for  an  American 
radar  research  and  development  effort  on  a  scale  equal  to  that  of  the  Manhattan  Project, 
which  historians  traditionally  have  recognized  as  the  beginning  of  Big  Science. 

The  history  of  planetary  radar  astronomy  in  the  United  States  is  the  history  of  Big  Science. 
Without  Big  Science,  planetary  radar  astronomy  would  be  impossible  and  unthinkable. 
That  is  one  of  the  main  contentions  of  this  book.  The  radar  astronomy  experiments  of  the 
1940s  and  1950s,  as  well  as  much  of  pre-war  radar  development,  were  intimately  linked  to 
ionospheric  research,  which  was  then  undergoing  a  rapid  publication  rate  typical  of  Big 
Science. 

Also,  the  evolutions  of  planetary  radar  and  radio  astronomy  converged.  The  search  for 
research  instruments  free  of  military  constraints  brought  planetary  radar  astronomers 
closer  to  radio  astronomy  during  the  1960s,  a  time  when  radio  astronomy  was  undergoing 
a  rapid  growth  that  transformed  it  into  Big  Science.  Planetary  radar  and  radio  astronomy 
shared  instruments  and  a  common  interest  in  electronic  hardware  and  techniques, 
though  ironically  the  instrumentation  needs  of  the  two  communities  ultimately  provided 
little  basis  for  cohabitation. 

In  the  end,  military  Big  Science  was  far  more  important  than  either  radio  astronomy  or 
ionospheric  science.  Planetary  radar  astronomy  emerged  in  the  late  1950s  thanks  to  Cold 
War  defense  research  that  furnished  the  essential  instruments  of  planetary  radar  experi- 
mentation. The  vulnerability  of  the  United  States  to  aircraft  and  ICBM  attacks  with 
nuclear  explosives  necessitated  the  creation  of  a  network  of  ever  more  powerful  and 
sensitive  defensive  radars.  What  President  Dwight  D.  Eisenhower  called  the  military- 
industrial  complex,  and  what  historian  Stuart  Leslie  calls  the  military-industrial-academic 
complex,1  provided  the  radar  instrument  for  the  first  attempts  at  Venus.  The  military- 
industrial  or  military-industrial-academic  complex  served  as  the  social  matrix  which  nur- 
tured military  and  other  Big  Science  research.  Planetary  radar  astronomy  eventually 
found  itself  part  of  a  different,  though  at  times  interlocking,  complex  centered  on  the 
civilian  enterprise  to  explore  space,  that  is,  what  one  might  call  the  NASA-industrial- 
academic  complex. 


1.        Stuart  W.  Leslie,  The  Cold  War  and  American  Science:  The  Mititary-Industrial-Academic  Complex  at  MIT 
and  Stanford  (New  York:  Columbia  University  Press,  1993). 


Vlll 


The  emergence  of  space  as  Big  Science  under  the  financial  and  institutional  aegis  of 
NASA,  and  the  design  and  construction  of  a  worldwide  network  of  antennas  to  track 
launches  and  communicate  with  spacecraft,  furnished  instruments  for  planetary  radar 
research  as  early  as  1961.  Within  a  decade,  NASA  became  the  de  facto  underwriter  of  all 
planetary  radar  astronomy.  Data  on  the  nature  of  planetary  surface  features  and  precise 
reckoning  of  both  the  astronomical  unit  and  planetary  orbits  were  highly  valuable  to  an 
institution  whose  primary  goal  was  (and  whose  budgetary  bulk  paid  for)  the  designing, 
building,  and  launching  of  vessels  for  the  exploration  of  the  solar  system.  Association  with 
NASA  Big  Science  enhanced  the  tendency  of  radar  astronomers  to  emphasize  the  utility 
of  their  research  and  promoted  mission-oriented,  as  opposed  to  basic,  research. 

The  history  of  planetary  radar  astronomy  is  intrinsically  interesting  and  forms  the  frame- 
work of  this  book.  It  also  says  something  about  Big  Science.  Defining  Big  Science,  or  even 
Little  Science,  is  not  easy  though.  After  all,  how  true  are  the  images  of  the  Little  Scientist 
as  "the  lone,  long-haired  genius,  moldering  in  an  attic  or  basement  workshop,  despised  by 
society  as  a  nonconformist,  existing  in  a  state  of  near  poverty,  motivated  by  the  flame 
burning  within  him,"  and  the  Big  Scientist  as  "honored  in  Washington,  sought  after  by  all 
the  research  corporations  of  the  'Boston  ring  road,'  part  of  an  elite  intellectual  brother- 
hood of  co-workers,  arbiters  of  political  as  well  as  technological  destiny"?2 

Since  the  publication  in  1963  of  Derek  J.  De  Solla  Price's  ground-breaking  Little  Science, 
Big  Science,  historians  have  attempted  to  define  Big  Science.3  Their  considerable  efforts 
have  clarified  the  meaning  of  the  term,  though  without  producing  a  universally  authori- 
tative definition.  If  large-scale  expensive  research  instruments  are  the  measure,  then  one 
might  count  the  island  observatory  of  Tycho  Brahe  in  the  sixteenth  century,  or  the  giant 
electrical  machines  built  in  eighteenth-century  Holland.  If  Big  Science  is  a  large  grouping 
of  investigators  from  several  disciplines  working  together  on  a  common  project,  then  the 
gathering  of  mathematicians,  chemists,  and  physicists  at  Thomas  Edison's  West  Orange 
laboratory  was  Big  Science.  A  long-term  research  project,  such  as  the  quest  for  an  AIDS 
cure,  or  one  that  entails  elaborate  organization,  such  as  the  Manhattan  Project,  might  be 
termed  Big  Science  too. 

Defining  Big  Science  is  the  intellectual  equivalent  of  trying  to  nail  Jell-O  to  the  wall.  For 
the  purposes  of  this  book,  we  shall  call  Big  Science  the  large-scale  organization  of  science 
and  scientists,  underwritten  by  an  imposing  pledge  of  (usually)  public  funds  and  centered 
around  a  complex  scientific  instrument.  In  his  search  to  understand  Big  Science,  Derek 
Price  decided  to  "turn  the  tools  of  science  on  itself,"  charting  the  historical  growth  of  sci- 
ence by  means  of  a  variety  of  statistical  indicators  obtained  from  the  Institute  for  Scientific 
Information  in  Philadelphia.  Price  concluded  that  scientific  activity  (as  measured  by  the 
amount  of  literature  published)  has  grown  exponentially  over  the  last  three  hundred 
years,  doubling  in  size  about  every  fifteen  years.4  We  also  shall  define  a  rapid  growth  in 
scientific  literature  greater  than  the  Price  rate  (doubling  every  fifteen  years)  as  indicating 


2.  Derek  J.  DeSolla  Price,  Little  Science,  Big  Science...  and  Beyond  (New  York:  Columbia  University  Press, 
1986),  p.  2. 

3.  Price,  Little  Science,  Big  Science...  and  Beyond,  p.  15.- 

4.  Price,  Little  Science,  Big  Science  (New  York:  Columbia  University  Press,  1963).  This  discussion  of  Big 
Science  draws  on  Peter  Galison  and  Bruce  Hevly,  eds.,  Big  Science:  The  Growth  of  Large-Scale  Research  (Stanford: 
Stanford  University  Press,  1992);  James  H.  Capshaw  and  Karen  A.  Rader,  "Big  Science:  Price  to  the  Present," 
Osiris,  ser.  2,  vol.  7  (1992):  3-25;  and  Joel  Genuth,  "Microwave  Radar,  the  Atomic  Bomb,  and  the  Background  to 
U.S.  Research  Priorities  in  World  War  II,"  Science,  Technology,  and  Human  Values  13  (1988):  276-289. 


an  emerging  Big  Science  field.  Whatever  it  is,  Big  Science  has  become  the  dominant  form 
of  contemporary  American  science.  Moreover,  because  of  its  scale  and  scope,  the  conduct 
of  Big  Science  necessarily  intrudes  into  many  areas  of  society,  and  in  turn,  society,  through 
political,  economic,  and  other  activity,  shapes  the  conduct  of  Big  Science. 

The  interdependency  of  institutional  factors,  funding  patterns,  science,  technology,  and 
techniques  found  in  Big  Science  has  been  the  subject  of  extensive  study  by  historians  and 
sociologists  of  science  and  technology.  Scholars  traditionally  have  concerned  themselves 
with  both  science  and  technology  and  their  interactions.  Such  studies  came  to  be  termed 
"internalist,"  meaning  that  they  dealt  solely  with  the  inner  workings  of  science  and  tech- 
nology. In  contrast  stood  the  so-called  "externalist"  approaches,  which  emphasized  the 
social,  economic,  political,  and  other  factors  neglected  by  the  "internalists." 

Starting  around  1980,  sociologists  of  science,  such  as  Michel  Gallon,  developed  new 
approaches,  which  were  introduced  into  the  history  of  technology  by  Thomas  P.  Hughes. 
These  new  approaches  came  to  be  called  generically  the  "social  construction  of  technol- 
ogy." The  "technosocial  networks"  of  Gallon  and  the  "systems"  of  Hughes  consider  the 
"internalist"  and  "externalist"  aspects  of  technology  as  constituting  a  single  continuum  or 
"seamless  web".  Inventors,  scientists,  instruments,  financing,  institutions,  politics,  laws, 
and  so  forth  are  all  equally  part  of  the  "technosocial  network"  or  "system".5 

The  chief  advantage  of  replacing  the  "internalist"  and  "externalist"  dualism  with  the  uni- 
tarian  approach  of  the  social  construction  school  is  the  more  sophisticated  and  certainly 
more  complex  view  of  the  scientific,  technical,  economic,  political,  institutional,  legal,  and 
other  aspects  of  Big  Science  that  it  offers.  Moreover,  by  stressing  that  all  components  of  a 
technosocial  network  are  equal  and  necessary,  the  social  construction  approach  dissuades 
us  from  emphasizing  any  one  factor,  "internal"  or  "external",  over  all  others. 

The  social  construction  approach  is  useful  for  creating  a  taxonomy  of  the  factors  that 
shape  Big  Science.  Nonetheless,  although  they  served  as  a  guiding  principle  in  the  writ- 
ing of  this  book,  social  construction  case  studies  do  not  go  far  enough;  they  fail  to  address 
the  question  that  is,  after  chronicling  the  achievements  of  radar  astronomy,  central  to  this 
book — namely  the  conduct  of  Little  Science  in  the  context  of  Big  Science.  Furthermore, 
in  all  the  discussions  of  Big  Science,  with  few  exceptions,  the  symbiotic  relationship 
between  Big  Science  and  Little  Science  has  been  overlooked.  This  relationship  is 
especially  relevant  to  the  organization  of  science  within  NASA  space  missions.  The  scien- 
tists who  conduct  experiments  from  those  spacecraft  typify  Little  Science:  they  work 
individually  or  in  small  collaborative  groups,  often  with  graduate  assistants,  and  have 
relatively  small  budgets  and  limited  laboratory  equipment.  Participation  in  NASA  space- 
craft missions  induces  these  Little  Scientists  to  function  as  part  of  a  Big  Science  endeavor. 
The  scientists  are  organized  into  both  working  groups  around  a  single  scientific 
instrument  and  disciplinary  groups.  They  participate  in  the  design  of  experiments  and  in 


5.  For  a  discussion  of  this  evolution,  see  John  M.  Staudenmaier,  "Recent  Trends  in  the  History  of 
Technology,"  The  American  Historical  Review  95  (1990):  715-725,  as  well  as  Hughes,  The  Seamless  Web: 
Technology,  Science,  Etcetera,  Etcetera,"  Social  Studies  of  Science  16  (1986):  281-292.  The  primary  social  con- 
struction works  are  Wiebe  E.  Bijker,  Hughes,  and  Trevor  Pinch,  eds.,  The  Social  Construction  of  Technological 
Systems:  New  Directions  in  the  Sociology  and  History  of  Technology  (Cambridge:  MIT  Press,  1987),  and  Bijker  and  John 
Law,  eds.,  Shaping  Technology/Building  Society:  Studies  in  Sociotechnical  Change  (Cambridge:  MIT  Press,  1992). 


the  decisions  to  drop  or  modify  certain  experiments,  as  well  as  in  the  design  of  the  instru- 
ments themselves.  The  overall  scale  of  operation  and  budget  is  beyond  that  normally 
encountered  by  Little  Scientists. 

One  noteworthy  exception  to  the  lack  of  literature  dealing  with  the  relationship  between 
Big  Science  and  Little  Science  is  historian  John  Krige's  study  of  British  nuclear  physics 
research  in  the  period  immediately  following  World  War  II.  The  Labor  Government  of 
Clement  Attlee  set  out  to  equip  the  universities  of  Birmingham,  Glasgow,  Liverpool, 
Cambridge,  and  Oxford  with  particle  accelerators  for  conducting  high-energy  nuclear 
physics  research.  The  accelerator  program  involved  the  kinds  of  large-scale  budgets  and 
instruments  that  typify  Big  Science;  however,  research  was  conducted  in  a  manner  more 
typical  of  Little  Science.  Large  multidisciplinary  teams,  in  which  physicists  and  engineers 
rubbed  shoulders,  did  not  form;  rather  the  physicists  remained  individual  academic 
researchers.6 

Krige's  case  of  "Big  Equipment  but  not  Big  Science"  finds  its  parallel  in  planetary  radar 
astronomy.  Big  Science  was  the  sine  qua  non  of  planetary  radar  astronomy,  but  planetary 
radar  astronomy  was  not  Big  Science.  It  was,  and  remains,  Little  Science  in  terms  of 
manpower,  instruments,  budget,  and  publications.  Planetary  radar  astronomy  took  root 
within  the  interstices  of  Big  Science,  but  rather  than  expand  over  time,  it  actually  shrank. 

The  field  attained  its  largest  size,  in  terms  of  personnel,  instruments,  and  publications, 
during  the  1960s.  Although  one  can  count  five  active  instruments  between  1961  and  1964, 
the  greatest  number  to  ever  carry  out  planetary  radar  experiments,  only  three  subse- 
quently sustained  active  research  programs.  That  number  fell  to  two  instruments  after 
1975.  For  much  of  the  period  between  1978  and  1986,  only  one  instrument,  indeed  the 
only  instrument  to  have  an  established  and  secure  planetary  radar  astronomy  research 
program,  the  Arecibo  Observatory,  was  steadily  active. 

The  number  of  active  planetary  radar  astronomers  has  declined  since  the  1960s  too.  As  a 
group,  they  tend  not  to  reproduce  as  easily  or  as  abundantly  as  other  scientists,  and  many 
practitioners  in  the  long  run  find  something  else  to  do.  Two  paths — artifacts  of  the  field's 
evolution — lead  to  a  career  in  planetary  radar  astronomy.  Many  follow  the  traditional 
university  path — doctoral  research  on  a  planetary  radar  topic,  followed  by  a  research 
position  that  permits  them  to  perform  planetary  radar  experiments.  Of  the  current  prac- 
titioners, the  most  recent  Ph.D.  was  granted  in  1994,  the  second  most  recent  in  1978.  The 
path  more  followed:  practitioners  were  hired  to  conduct  planetary  radar  experiments. 

The  declining  instrument  and  manpower  numbers  are  reflected  in  the  planetary  radar 
astronomy  publication  record  (see  Appendix:  Planetary  Radar  Astronomy  Publications) . 
Price  has  shown  that  science  publications  have  doubled  about  every  fifteen  years  over  the 
last  three  centuries.  The  planetary  radar  publication  curve  differs  markedly  from  that  nor- 
mal growth  pattern,  suggesting  a  ceiling  condition  that  has  limited  growth.  The  nature  of 
that  ceiling  condition,  as  well  as  the  causal  factors  for  the  declining  size  of  the  planetary 
radar  enterprise,  are  part  of  the  story  of  how  planetary  radar  Little  Science  has  been  con- 
ducted within  the  framework  of  American  Big  Science.  The  association  of  planetary  radar 


6.  John  Krige,  The  Installation  of  High-Energy  Accelerators  in  Britain  after  the  War:  Big  Equipment 
but  not  'Big  Science,'"  in  Michelangelo  De  Maria,  Mario  Grilli,  and  Fabio  Sebastiani,  eds.,  The  Restructuring  of 
Physical  Sciences  in  Europe  and  the  United  States,  1945-1960  (Teaneck,  NJ:  World  Scientific,  1989),  pp.  488-501. 


Xi 


Little  Science  with  NASA  Big  Science  ultimately  affected  the  conduct  of  planetary  radar 
astronomy.  Radar  astronomers  always  had  argued  the  utility  of  their  efforts  for  space 
research;  NASA  mission-oriented  support  of  planetary  radar  astronomy  only  reinforced 
that  utilitarian  inclination.  As  the  story  unfolds,  other  factors  that  shaped  and  amplified 
the  utilitarian  tendency  of  radar  astronomers  will  rise  to  the  surface. 

Its  relationship  with  NASA  Big  Science  also  transformed  planetary  radar  astronomy  from 
an  exclusively  ground-based  scientific  activity  to  one  that  was  conducted  in  space  as  well. 
During  the  1960s,  planetary  radar  astronomers  distinguished  their  ground-based  research 
from  that  conducted  from  spacecraft,  which  they  characterized  as  space  exploration  as 
opposed  to  astronomy.  Starting  in  the  following  decade,  when  NASA  became  its  sole 
underwriter,  planetary  radar  astronomy  began  to  engage  the  planetary  geology  commu- 
nity largely  through  its  ability  to  image  and  otherwise  characterize  planetary  surfaces. 
NASA  funded  specific  radar  imaging  projects.  At  the  same  time,  NASA  began  planning 
two  missions  to  Venus,  Pioneer  Venus  and  Magellan,  in  order  to  capture  in  radar  images 
the  features  of  that  planet's  surface.  Its  opaque  atmosphere  keeps  Venus's  surface  hidden 
from  sight  and  bars  exploration  with  optical  methods. 

Pioneer  Venus  and  Magellan  ultimately  had  a  profound  impact  on  the  practice  of  plane- 
tary radar  astronomy.  In  addition  to  enlarging  the  community  of  scientists  using  radar 
imagery  and  other  data  to  encompass  both  geologists  and  astronomers,  those  two  NASA 
missions  erased  the  turf  boundary  between  space  exploration  and  ground-based  plane- 
tary radar  astronomy.  Although  Magellan  in  particular  also  gave  radar  astronomers  a  taste 
of  Big  Science,  planetary  radar  astronomy  did  not  permanently  shift  from  Little  to  Big 
Science.  Radar  imaging  from  a  spacecraft  had  limited  prospects.  Ultimately,  the  greatest 
consequence  of  Magellan  for  planetary  radar  astronomy  was  that  it  effectively  ended 
ground-based  radar  observations  of  Venus,  the  chief  object  of  radar  research. 

The  plan  of  this  book  is  to  relate  the  history  of  planetary  radar  astronomy  from  its  origins 
in  radar  to  the  present  day  and  secondarily  to  bring  to  light  that  history  as  a  case  of  "Big 
Equipment  but  not  Big  Science".  Chapter  One  sketches  the  emergence  of  radar  astrono- 
my as  an  ongoing  scientific  activity  at  Jodrell  Bank,  where  radar  research  revealed  that 
meteors  were  part  of  the  solar  system.  The  chief  Big  Science  driving  early  radar  astrono- 
my experiments  was  ionospheric  research.  Chapter  Two  links  the  Cold  War  and  the  Space 
Race  to  the  first  radar  experiments  attempted  on  planetary  targets,  while  recounting  the 
initial  achievements  of  planetary  radar,  namely,  the  refinement  of  the  astronomical  unit 
and  the  rotational  rate  and  direction  of  Venus. 

Chapter  Three  discusses  early  attempts  to  organize  radar  astronomy  and  the  efforts  at 
MIT's  Lincoln  Laboratory,  in  conjunction  with  Harvard  radio  astronomers,  to  acquire 
antenna  time  unfettered  by  military  priorities.  Here,  the  chief  Big  Science  influencing  the 
development  of  planetary  radar  astronomy  was  radio  astronomy.  Chapter  Four  spotlights 
the  evolution  of  planetary  radar  astronomy  at  the  Jet  Propulsion  Laboratory,  a  NASA 
facility,  at  Cornell  University's  Arecibo  Observatory,  and  at  Jodrell  Bank.  A  congeries  of 
funding  from  the  military,  the  National  Science  Foundation,  and  finally  NASA  marked 
that  evolution,  which  culminated  in  planetary  radar  astronomy  finding  a  single  Big 
Science  patron,  NASA. 

Chapter  Five  analyzes  planetary  radar  astronomy  as  a  science  using  the  theoretical  frame- 
work provided  by  philosopher  of  science  Thomas  Kuhn.  Chapter  Six  explores  the  shift  in 


xii 


planetary  radar  astronomy  beginning  in  the  1970s  that  resulted  from  its  financial  and 
institutional  relationship  with  NASA  Big  Science.  This  shift  saw  the  field  1)  transform 
from  an  exclusively  ground-based  scientific  activity  to  one  conducted  in  space,  as  well  as 
on  Earth,  and  2)  capture  the  interest  of  planetary  scientists  from  both  the  astronomy  and 
geology  communities.  Chapter  Seven  relates  how  the  Magellan  mission  was  the  culmina- 
tion of  this  evolution.  Chapters  Eight  and  Nine  discuss  the  research  carried  out  at  ground- 
based  facilities  by  this  transformed  planetary  radar  astronomy,  as  well  as  the  upgrading  of 
the  Arecibo  and  Goldstone  radars. 

The  conclusion  serves  a  dual  purpose.  It  responds  to  the  concern  for  the  future  of  plan- 
etary radar  astronomy  expressed  by  many  of  the  practitioners  interviewed  for  this  book, 
as  well  as  to  the  author's  wish  to  provide  a  slice  of  applied  history  that  might  be  of  value 
to  both  radar  astronomers  and  policy  makers.  The  conclusipn  also  appraises  planetary 
radar  as  a  case  of  "Big  Equipment  but  not  Big  Science".  It  considers  the  factors  that  have 
limited  the  size  of  planetary  radar,  its  utilitarian  nature,  and  its  dependency  on  large-scale 
technological  enterprises. 

A  technical  essay  appended  to  this  book  provides  an  overview  of  planetary  radar  tech- 
niques, especially  range-Doppler  mapping,  for  the  general  reader.  Furthermore,  the  text 
itself  explains  certain,  though  not  all,  technical  aspects  of  radar  astronomy.  The  author 
assumed  that  the  reader  would  have  a  familiarity  with  general  technical  and  scientific  ter- 
minology or  would  have  access  to  a  scientific  dictionary  or  encyclopedia.  For  those  read- 
ers seeking  additional,  and  especially  more  technically-oriented,  information  on  plane- 
tary radar  astronomy,  the  technical  essay  includes  a  list  of  articles  on  the  topic  written  by 
radar  practitioners. 


Chapter  One 

A  Meteoric  Start 


During  the  1940s,  investigators  in  the  United  States  and  Hungary  bounced  radar 
waves  off  the  Moon  for  the  first  time,  while  others  made  the  first  systematic  radar  studies 
of  meteors.  These  experiments  constituted  the  initial  exploration  of  the  solar  system  with 
radar.  In  order  to  understand  the  beginnings  of  radar  astronomy,  we  first  must  examine 
the  origins  of  radar  in  radio,  the  decisive  role  of  ionospheric  research,  and  the  rapid 
development  of  radar  technology  triggered  by  World  War  II. 

As  early  as  20  June  1922,  in  an  address  to  a  joint  meeting  of  the  Institute  of  Electrical 
Engineers  and  the  Institute  of  Radio  Engineers  in  New  York,  the  radio  pioneer  Guglielmo 
Marconi  suggested  using  radio  waves  to  detect  ships:1 

As  was  first  shown  by  Hertz,  electric  waves  can  be  completely  reflected  by  conduct- 
ing bodies.  In  some  of  my  tests  I  have  noticed  the  effects  of  reflection  and  deflection  of  these 
waves  by  metallic  objects  miles  away. 

It  seems  to  me  that  it  should  be  possible  to  design  apparatus  by  means  of  which  a  ship 
could  radiate  or  project  a  divergent  beam  of  these  rays  in  any  desired  direction,  which  rays, 
if  coming  across  a  metallic  object,  such  as  another  steamer  or  ship,  would  be  reflected  back 
to  a  receiver  screened  from  the  local  transmitter  on  the  sending  ship,  and  thereby  immedi- 
ately reveal  the  presence  and  bearing  of  the  other  ship  in  fog  or  thick  weather. 

One  further  advantage  of  such  an  arrangement  would  be  it  would  have  the  ability 
to  give  warning  of  the  presence  and  bearing  of  ships,  even  should  these  ships  be  unpro- 
vided with  any  kind  of  radio. 

By  the  time  Germany  invaded  Poland  in  September  1939  and  World  War  II  was 
underway,  radio  detection,  location,  and  ranging  technologies  and  techniques  were  avail- 
able in  Japan,  France,  Italy,  Germany,  England,  Hungary,  Russia,  Holland,  Canada,  and 
the  United  States.  Radar  was  not  so  much  an  invention,  springing  from  the  laboratory 
bench  to  the  factory  floor,  but  an  ongoing  adaptation  and  refinement  of  radio  technolo- 
gy. The  apparent  emergence  of  radar  in  Japan,  Europe,  and  North  America  more  or  less 
at  the  same  time  was  less  a  case  of  simultaneous  invention  than  a  consequence  of  the  glob- 
al nature  of  radio  research.2 

Although  radar  is  identified  overwhelmingly  with  World  War  II,  historian  Sean  S. 
Swords  has  argued  that  the  rise  of  high-performance  and  long-range  aircraft  in  the  late 
1930s  would  have  promoted  the  design  of  advanced  radio  navigational  aids,  including 
radar,  even  without  a  war.3  More  decisively,  however,  ionospheric  research  propelled  radar 
development  in  the  1920s  and  1930s.  As  historian  Henry  Guerlac  has  pointed  out,  "Radar 
was  developed  by  men  who  were  familiar  with  the  ionospheric  work.  It  was  a  relatively 
straightforward  adaptation  for  military  purposes  of  a  widely-known  scientific  technique, 


1.  Guglielmo  Marconi,  "Radio  Telegraphy,"  Proceedings  of  the  Institute  of  Radio  Engineers  10  (1922):  237. 

2.  Charles  Susskind,  "Who  Invented  Radar?"  Endeavour^  (1985) :  92-96;  Henry  E.  Guerlac,  The  Radio 
Background  of  Radar, "  Journal  of  the  Franklin  Institute  250  (1950):  284-308. 

3.  Swords,  A  Technical  History  of  the  Beginnings  of  Radar  (London:  Peter  Peregrinus  Press,  1986), 
pp.  270-271. 


TO  SEE  THE  UNSEEN 


which  explains  why  this  adaptation — the  development  of  radar — took  place  simultane- 
ously in  several  different  countries."4 

The  prominence  of  ionospheric  research  in  the  history  of  radar  and  later  of  radar 
astronomy  cannot  be  ignored.  Out  of  ionospheric  research  came  the  essential  technology 
for  the  beginnings  of  military  radar  in  Britain,  as  well  as  its  first  radar  researchers  and 
research  institutions.  After  the  war,  as  we  shall  see,  ionospheric  research  also  drove  the 
emergence  of  radar  astronomy. 

Chain  Home 

Despite  its  scientific  origins,  radar  made  its  mark  and  was  baptized  during  World  War 
II  as  an  integral  and  necessary  instrument  of  offensive  and  defensive  warfare.  Located  on 
land,  at  sea,  and  in  the  air,  radars  detected  enemy  targets  and  determined  their  position 
and  range  for  artillery  and  aircraft  in  direct  enemy  encounters  on  the  battlefield.  Other 
radars  identified  aircraft  to  ground  bases  as  friend  or  foe,  while  others  provided  naviga- 
tional assistance  and  coastal  defense.  World  War  II  was  the  first  electronic  war,  and  radar 
was  its  prime  agent.5 

In  1940,  nowhere  did  radar  research  achieve  the  same  advanced  state  as  in  Britain.  The 
British  lead  initially  resulted  from  a  decision  to  design  and  build  a  radar  system  for  coastal 
defense,  while  subsequent  research  led  to  the  invention  of  the  cavity  magnetron,  which 
placed  Britain  in  the  forefront  of  microwave  radar.  The  impetus  to  achieve  that  lead  in  radar 
came  from  a  realization  that  the  island  nation  was  no  longer  safe  from  enemy  invasion. 

For  centuries,  Britain's  insularity  and  navy  protected  it  from  invasion.  The  advent  of 
long-range  airplanes  that  routinely  outperformed  their  wooden  predecessors  spelled  the 
end  of  that  protection.  Existing  aircraft  warning  methods  were  ineffectual.  That  Britain 
was  virtually  defenseless  against  an  air  assault  became  clear  during  the  summer  air  exer- 
cises of  1934.  In  simulated  night  attacks  on  London  and  Coventry,  both  the  Air  Ministry 
and  the  Houses  of  Parliament  were  successfully  "destroyed,"  while  few  "enemy"  bombers 
were  intercepted.6 

International  politics  also  had  reached  a  critical  point.  The  Geneva  Disarmament 
Conference  had  collapsed,  and  Germany  was  rearming  in  defiance  of  the  Treaty  of 
Versailles.  Under  attack  from  Winston  Churchill  and  the  Tory  opposition,  the  British  gov- 
ernment abandoned  its  disarmament  policy  and  initiated  a  five-year  expansion  of  the 
Royal  Air  Force.  Simultaneously,  the  Air  Ministry  Director  of  Scientific  Research,  Henry 
Egerton  Wimperis,  created  a  committee  to  study  air  defense  methods. 

Just  before  the  Committee  for  the  Scientific  Survey  of  Air  Defence  first  met  on  28 
January  1935,  Wimperis  contacted  fellow  Radio  Research  Board  member  Robert  (later 
Sir)  Watson-Watt.  Watson-Watt,  who  oversaw  the  Radio  Research  Station  at  Slough,  was  a 
scientist  with  twenty  years  of  experience  as  a  government  researcher.  Ionospheric  research 
had  been  a  principal  component  of  Radio  Research  Station  studies,  and  Watson-Watt  fos- 
tered the  development  there  of  a  pulse-height  technique.7 


4.  Guerlac,  "Radio  Background,"  p.  304. 

5.  Alfred  Price,  Instruments  of  Darkness:  The  History  of  Electronic  Warfare,  2d.  ed.  (London:  MacDonald 
and  Jane's,  1977);  Tony  Devereux,  Messenger  Gods  of  Battle,  Radio,  Radar,  Sonar:  The  Story  of  Electronics  in  War 
(Washington:  Brassey's,  1991);  David  E.  Fisher,  A  Race  on  the  Edge  of  Time:  Radar — the  Decisive  Weapon  of  World  War 
II  (New  York:  McGraw-Hill,  1988). 

6.  H.  Montgomery  Hyde,  British  Air  Policy  Between  the  Wars,  1918-1939  (London:  Heinemann,  1976), 
p.  322.  See  also  Malcolm  Smith,  British  Air  Strategy  Between  the  Wan  (Oxford,  Clarendon  Press,  1984). 

7.  Swords,  p.  84;  Edward  G.  Bowen,  Radar  Days  (Bristol:  Adam  Hilger,  1987),  pp.  4-5,  7  and  10;  Robert 
Watson-Watt,   The  Pulse  of  Radar:  The  Autobiography  of  Sir  Robert  Watson-Watt  (New  York:  Dial  Press,   1959), 
pp.  29-38,  51,  69,  101,  109-110,  113;  A.P.  Rowe,  One  Story  of  Radar  (Cambridge:  Cambridge  University  Press, 
1948),  pp.  6-7;  Reg  Batt,  The  Radar  Army:  Winning  the  War  of  the  Airwaves  (London:  Robert  Hale,  1991), 
pp.  21-22.  The  Radio  Research  Board  was  under  the  Department  of  Scientific  and  Industrial  Research,  created 
in  1916. 


A  METEORIC  START 


The  pulse-height  technique  was  to  send  short  pulses  of  radio  energy  toward  the 
ionosphere  and  to  measure  the  time  taken  for  them  to  return  to  Earth.  The  elapsed  trav- 
el time  of  the  radio  waves  gave  the  apparent  height  of  the  ionosphere.  Merle  A.  Tuve,  then 
of  Johns  Hopkins  University,  and  Gregory  Breit  of  the  Carnegie  Institution's  Department 
of  Terrestrial  Magnetism  in  Washington,  first  developed  the  technique  in  the  1920s  and 
undertook  ionospheric  research  in  collaboration  with  the  Naval  Research  Laboratory  and 
the  Radio  Corporation  of  America.8 

In  response  to  the  wartime  situation,  Wimperis  asked  Watson-Watt  to  determine  the 
practicality  of  using  radio  waves  as  a  "death  ray."  Rather  than  address  the  proposed  "death 
ray,"  Watson-Watt's  memorandum  reply  drew  upon  his  experience  in  ionospheric 
research.  Years  later,  Watson-Watt  contended,  "I  regard  this  Memorandum  on  the 
'Detection  and  Location  of  Aircraft  by  Radio  Methods'  as  marking  the  birth  of  radar  and 
as  being  in  fact  the  invention  of  radar."9  Biographer  Ronald  William  Clark  has  termed  the 
memorandum  "the  political  birth  of  radar."  Nonetheless,  Watson-Watt's  memorandum 
was  really  less  an  invention  than  a  proposal  for  a  new  radar  application. 

The  memorandum  outlined  how  a  radar  system  could  be  put  together  and  made  to 
detect  and  locate  enemy  aircraft.  The  model  for  that  radar  system  was  the  same  pulse- 
height  technique  Watson-Watt  had  used  at  Slough.  Prior  to  the  memorandum  in  its  final 
form  going  before  the  Committee,  Wimperis  had  arranged  for  a  test  of  Watson-Watt's  idea 
that  airplanes  could  reflect  significant  amounts  of  radio  energy,  using  a  BBC  transmitter 
at  Daventry.  "Thus  was  the  constricting  'red  tape'  of  official  niceties  slashed  by  Harry 
Wimperis,  before  the  Committee  for  the  Scientific  Survey  of  Air  Defence  had  so  much  as 
met,"  Watson-Watt  later  recounted.  The  success  of  the  Daventry  test  shortly  led  to  the 
authorization  of  funding  (£12,300  for  the  first  year)  and  the  creation  of  a  small  research 
and  development  project  at  Orford  Ness  and  Bawdsey  Manor  that  drew  upon  the  exper- 
tise of  the  Slough  Radio  Research  Station. 

From  then  onwards,  guided  largely  by  Robert  Watson-Watt,  the  foundation  of  the 
British  radar  effort,  the  early  warning  Chain  Home,  materialized.  The  Chain  Home  began 
in  December  1935,  with  Treasury  approval  for  a  set  of  five  stations  to  patrol  the  air 
approaches  to  the  Thames  estuary.  Before  the  end  of  1936,  and  long  before  the  first  test 
of  the  Thames  stations  in  the  autumn  of  1937,  plans  were  made  to  expand  it  into  a 
network  of  nineteen  stations  along  the  entire  east  coast;  later,  an  additional  six  stations 
were  built  to  cover  the  south  coast. 


Born  Robert  Alexander  Watson  Watt  in  1892,  he  changed  his  surname  to  "Watson-Watt"  when  knighted 
in  1942.  See  the  popularly-written  biography  of  Watson-Watt,  John  Rowland,  The  Radar  Man:  The  Story  of  Sir  Robert 
Watson-Watt  (London:  Lutterworth  Press,  1963),  or  Watson-Watt,  Three  Steps  to  Victory  (London:  Odhams  Press 
Ltd.,  1957).  An  account  of  Watson-Watt's  research  at  Slough  is  given  in  Watson-Watt,  John  F.  Herd,  and  L.H. 
Bainbridge-Bell,  The  Cathode  Ray  Tube  in  Radio  Research  (London:  His  Majesty's  Stationery  Office,  1933). 

8.  By  "apparent  height  of  the  ionosphere,"  I  mean  what  ionosphericists  call  virtual  height.  Since  the 
ionosphere  slows  radio  waves  before  being  refracted  back  to  Earth,  the  delay  is  not  a  true  measure  of  height. 
The  Tuve-Breit  method  preceded  that  of  Watson-Watt  and  was  a  true  send-receive  technique,  while  that  of 
Watson-Watt  was  a  receive-only  technique. 

Tuve  "Early  Days  of  Pulse  Radio  at  the  Carnegie  Institution, "  Journal  of  Atmospheric  and  Terrestrial  Physics  36 
(1974):  2079-2083;  Oswald  G.  Villard,  Jr.,  "The  Ionospheric  Sounder  and  its  Place  in  the  History  of  Radio 
Science,"  Radio  Science  11  (1976):  847-860;  Guerlac,  "Radio  Background,"  pp.  284-308;  David  H.  DeVorkin, 
Science  With  a  Vengeance:  How  the  Military  Created  the  U.S.  Space  Sciences  after  World  War  II  (New  York:  Springer-Verlag, 
1992),  pp.  12,  301  and  316;  C.  Stewart  Gillmor,  Threshold  to  Space:  Early  Studies  of  the  Ionosphere,"  in  Paul 
A.  Hanle  and  Von  Del  Chamberlin,  eds.,  Space  Science  Comes  of  Age:  Perspectives  in  the  History  of  the  Space  Sciences 
(Washington:  National  Air  and  Space  Museum,  Smithsonian  Institution,  1981),  pp.  102-104;  JA.  Ratcliffe, 
"Experimental  Methods  of  Ionospheric  Investigation,  1925-1955,"  Journal  of  Atmospheric  and  Terrestrial  Physics  36 
(1974):  2095-2103;  Tuve  and  Breit,  "Note  on  a  Radio  Method  of  Estimating  the  Height  of  the  Conducting 
Layer,"  Terrestrial  Magnetism  and  Atmospheric  Electricity  30  (1925):  15-16;  Breit  and  Tuve,  "A  Radio  Method  of 
Estimating  the  Height  of  the  Conducting  Layer,"  Nature  116  (1925):  357;  and  Breit  and  Tuve,  "A  Test  of  the 
Existence  of  the  Conducting  Layer,"  Physical  Review  2d  ser.,  vol.  28  (1926):  554-575;  special  issue  of  Journal  of 
Atmospheric  and  Terrestrial  Physics  36  (1974):  2069-2319,  is  devoted  to  the  history  of  ionospheric  research. 

9.  Watson-Watt,  Three  Steps,  p.  83;  Ronald  William  Clark,  Tizard  (London:  Methuen,  1965),  pp.  105-127. 


TO  SEE  THE  UNSEEN 


The  Chain  Home  played  a  crucial  role  in  the  Battle  of  Britain,  which  began  in  July 
1940.  The  final  turning  point  was  on  15  September,  when  the  Luftwaffe  suffered  a  record 
number  of  planes  lost  in  a  single  day.  Never  again  did  Germany  attempt  a  massive  daylight 
raid  over  Britain.  However,  if  radar  won  the  day,  it  lost  the  night.  Nighttime  air  raids 
showed  a  desperate  need  for  radar  improvements. 


The  Magnetron 


In  order  to  wage  combat  at  night,  fighters  needed  the  equivalent  of  night  vision — 
their  own  on-board  radar,  but  the  prevailing  technology  was  inadequate.  Radars  operating 
at  low  wavelengths,  around  1 .5  meters  (200  MHz) ,  cast  a  beam  that  radiated  both  straight 
ahead  and  downwards.  The  radio  energy  reflected  from  the  Earth  was  so  much  greater 
than  that  of  the  enemy  aircraft  echoes  that  the  echoes  were  lost  at  distances  greater  than 
the  altitude  of  the  aircraft.  At  low  altitudes,  such  as  those  used  in  bombing  raids  or  in  air- 
to-air  combat,  the  lack  of  radar  vision  was  grave.  Microwave  radars,  operating  at  wave- 
lengths of  a  few  centimeters,  could  cast  a  narrower  beam  and  provide  enough  resolution 
to  locate  enemy  aircraft.10 

Although  several  countries  had  been  ahead  of  Britain  in  microwave  radar  technolo- 
gy before  the  war  began,  Britain  leaped  ahead  in  February  1940,  with  the  invention  of  the 
cavity  magnetron  by  Henry  A.  H.  Boot  and  John  T.  Randall  at  the  University  of 
Birmingham.11  Klystrons  were  large  vacuum  tubes  used  to  generate  microwave  power,  but 
they  did  not  operate  adequately  at  microwave  frequencies.  The  time  required  for  elec- 
trons to  flow  through  a  klystron  was  too  long  to  keep  up  with  the  frequency  of  the  exter- 
nal oscillating  circuit.  The  cavity  magnetron  resolved  that  problem  and  made  possible  the 
microwave  radars  of  World  War  II.  As  Sean  Swords  asserted,  'The  emergence  of  the 
resonant-cavity  magnetron  was  a  turning  point  in  radar  history."12  The  cavity  magnetron 
launched  a  line  of  microwave  research  and  development  that  has  persisted  to  this  day. 

The  cavity  magnetron  had  no  technological  equivalent  in  the  United  States,  when 
the  Tizard  Mission  arrived  in  late  1940  with  one  of  the  first  ten  magnetrons  constructed. 
The  Tizard  Mission,  known  formally  as  the  British  Technical  and  Scientific  Mission,  had 
been  arranged  at  the  highest  levels  of  government  to  exchange  technical  information 
between  Britain  and  the  United  States.  Its  head  and  organizer,  Henry  Tizard,  was  a  promi- 
nent physics  professor  and  a  former  member  of  the  committee  that  had  approved  Watson- 
Watt's  radar  project.  As  James  P.  Baxter  wrote  just  after  the  war's  end  with  a  heavy  hand- 
ful of  hyperbole,  though  not  without  some  truth:  "When  the  members  of  the  Tizard 
Mission  brought  one  [magnetron]  to  America  in  1940,  they  carried  the  most  valuable 
cargo  ever  brought  to  our  shores.  It  sparked  the  whole  development  of  microwave  radar 
and  constituted  the  most  important  item  in  reverse  Lease-Lend."13 


10.  Swords,  pp.  84-85;  Bowen,  pp.  6,  21,  26  and  28;  Batt,  pp.  10,  21-22,  69  and  77;  Rowe,  pp.  8  and  76; 
R.  Hanbury  Brown,  Boffin:  A  Personal  Story  of  the  Early  Days  of  Radar,  Radio  Astronomy,  and  Quantum  Optics  (Bristol: 
Adam  Hilger,  1991),  pp.  7-8;  P.S.  Hall  and  R.G.  Lee,  "Introduction  to  Radar,"  in  P.S.  Hall,  T.K.  Garland-Collins, 
R.S.  Picton,  and  R.G.  Lee,  eds.,  Radar  (London:  Brassey's,  1991),  pp.  6-7;  Watson-Watt,  Pulse,  pp.  55-59,  64-65, 
75,  1 13-1 15  and  427-434;  Watson-Watt,  Three  Steps,  pp.  83  and  470-474;  Bowen,  The  Development  of  Airborne 
Radar  in  Great  Britain,   1935-1945,"  in  Russel  W.  Burns,  ed.,  Radar  Development  to  1945  (London:  Peter 
Peregrinus  Press,  1988),  pp.  177-188.  For  a  description  of  the  technology,  see  B.T.  Neale,  "CH— the  First 
Operational  Radar,"  in  Burns,  pp.  132-150. 

11.  Boot  and  Randall,  "Historical  Notes  on  the  Cavity  Magnetron,"  IEEE  Transactions  on  Electron  Devices 
ED-23  (1976):  724-729;  R.W.  Burns,  "The  Background  to  the  Development  of  the  Cavity  Magnetron,"  in  Burns, 
pp. 259-283. 

12.  Swords,  p.  xi. 

13.  Baxter,  Scientists  Against  Time  (Boston:  Little,  Brown  and  Company,  1946),  p.  142;  Swords,  pp.  120, 
259,  and  266;  Clark,  especially  pp.  248-271. 


A  METEORIC  START 


In  late  September  1940,  Dr.  Edward  G.  Bowen,  the  radar  scientist  on  the  Tizard 
Mission,  showed  a  magnetron  to  members  of  the  National  Defense  Research  Committee 
(NDRC),  which  President  Roosevelt  had  just  created  on  27  June  1940.  One  of  the  first  acts 
of  the  NDRC,  which  later  became  the  Office  of  Scientific  Research  and  Development,  was 
to  establish  a  Microwave  Committee,  whose  stated  purpose  was  "to  organize  and  consoli- 
date research,  invention,  and  development  as  to  obtain  the  most  effective  military 
application  of  microwaves  in  the  minimum  time."14 

A  few  weeks  after  the  magnetron  demonstration,  the  NDRC  decided  to  create  the 
Radiation  Laboratory  at  MIT.  While  the  MIT  Radiation  Laboratory  accounted  for  nearly 
80  percent  of  the  NDRC  Microwave  Division's  contracts,  an  additional  136  contracts  for 
radar  research,  development,  and  prototype  work  were  let  out  to  sixteen  colleges  and 
universities,  two  private  research  institutions,  and  the  major  radio  industrial  concerns, 
with  Western  Electric  taking  the  largest  share.  The  MIT  Radiation  Laboratory  personnel 
skyrocketed  from  thirty  physicists,  three  guards,  two  stock  clerks,  and  a  secretary  for  the 
first  year  to  a  peak  employment  level  of  3,897  (1,189  of  whom  were  staff)  on  1  August 
1945.  The  most  far-reaching  early  achievement,  accomplished  in  the  spring  of  1941,  was 
the  creation  of  a  new  generation  of  radar  equipment  based  on  a  magnetron  operating  at 
3  cm.  Experimental  work  in  the  one  cm  range  led  to  numerous  improvements  in  radars 
at  10  and  3  cm.15 

Meanwhile,  research  and  development  of  radars  of  longer  wavelengths  were  carried 
out  by  the  Navy  and  the  Army  Signal  Corps,  both  of  which  had  had  active  ongoing  radar 
programs  since  the  1930s.  The  Navy  started  its  research  program  at  the  Naval  Research 
Laboratory  (NRL)  before  that  of  the  Signal  Corps,  but  radar  experimenters  after  the  war 
used  Signal  Corps  equipment,  especially  the  SCR-270,  mainly  because  of  its  wide  avail- 
ability. A  mobile  SCR-270,  placed  on  Oahu  as  part  of  the  Army's  Aircraft  Warning  System, 
spotted  incoming  Japanese  airplanes  nearly  50  minutes  before  they  bombed  United  States 
installations  at  Pearl  Harbor  on  7  December  1941.  The  warning  was  ignored,  because  an 
officer  mistook  the  radar  echoes  for  an  expected  flight  of  B-l7s.16 

Historians  view  the  large-scale  collection  of  technical  and  financial  resources  and 
manpower  at  the  MIT  Radiation  Laboratory  engaged  in  a  concerted  effort  to  research 
and  develop  new  radar  components  and  systems,  along  with  the  Manhattan  Project,  as 


14.  Guerlac,  Radar  in  World  War  II,  The  History  of  Modern  Physics,  1800-1950,  vol.  8  (New  York: 
Tomash  Publishers  for  the  American  Institute  of  Physics,  1987),  vol.  1,  p.  249;  Swords,  pp.  90  and  119;  Batt,  pp. 
79-80;  Bowen,  pp.  159-162:  Watson  Watt,  Pulse,  pp.  228-229  and  257;  Watson-Watt,  Three  Steps,  293. 

In  addition  to  Tizard  and  Bowen,  the  Mission  team  consisted  of  Prof.  J.D.  Cockcroft,  Col.  F.C.  Wallace, 
Army,  Capt.  H.W.  Faulkner,  Navy,  Capt.  F.L.  Pearce,  Royal  Air  Force,  WE.  Woodward  Nutt,  Ministry  of  Aircraft 
Production,  Mission  Secretary,  Prof.  R.H.  Fowler,  liaison  officer  for  Canada  and  the  United  States  of  the 
Department  of  Scientific  and  Industrial  Research,  and  Col.  H.F.G.  Letson,  Canadian  military  attache  in 
Washington. 

15.  Guerlac,  Radar  in  World  War  II,  1:258-259,  261,  266  and  507-508,  and  2:648  and  668.  See  also  the 
personal  reminiscences  of  Ernest  C.  Pollard,  Radiation:  One  Story  of  the  MIT  Radiation  Laboratory  (Durham:  The 
Woodburn  Press,  1982).  Interviews  (though  not  all  are  transcribed)  of  some  Radiation  Laboratory  participants 
are  available  at  the  IEEE  Center  for  the  History  of  Electrical  Engineering  (CHEE),  Rutgers  University.  CHEE, 
Sources  in  Electrical  History  2:  Oral  History  Collections  in  U.S.  Repositories  (New  York:  IEEE,  1992) ,  pp.  6-7.  The  British 
also  developed  magnetrons  and  radar  equipment  operating  at  microwave  frequencies  concurrently  with  the  MIT 
Radiation  Laboratory  effort. 

16.  Guerlac,  Radar  in  World  War  II,  1:247-248  and  117-119.  For  die  Navy,  see  LA.  Hyland,  "A  Personal 
Reminiscence:  The  Beginnings  of  Radar,  1930-1934,"  in  Burns,  pp.  29-33;  Robert  Morris  Page,  The  Origin  of 
Radar  (Garden  City,  NY:  Anchor  Books,  Doubleday  &  Company,  1962);  Page,  "Early  History  of  Radar  in  die  U.S. 
Navy,"  in  Burns,  pp.  35-44;  David  Kite  Allison,  New  Eye  for  the  Navy:  The  Origin  of  Radar  at  the  Naval  Research 
Laboratory  (Washington:  Naval  Research  Laboratory,  1981);  Guerlac,  Radar  in  World  War  II,  1:59-92;  Albert  Hoyt 
Taylor,  The  Pint  Twenty-five  Yean  of  the  Naval  Research  Laboratory  (Washington:  Navy  Department,  1948) .  On  die 
Signal  Corps,  see  Guerlac,  Radarin  World  War  II,  1:93-121;  Harry  M.  Davis,  History  of  the  Signal  Corps  Development 
of  U.S.  Army  Radar  Equipment  (Washington:  Historical  Section  Field  Office,  Office  of  the  Chief  Signal  Officer, 
1945);  Arthur  L.  Vieweger,  "Radar  in  die  Signal  Corps,"  IRE  Transactions  on  Military  Electronics  MIL-4  (1960): 
555-561. 


TO  SEE  THE  UNSEEN 


signalling  the  emergence  of  Big  Science.  Ultimately,  from  out  of  the  concentration  of 
personnel,  expertise,  materiel,  and  financial  resources  at  the  successor  of  the  Radiation 
Laboratory,  Lincoln  Laboratory,  arose  the  first  attempts  to  detect  the  planet  Venus  with 
radar.  The  Radiation  Laboratory  Big  Science  venture,  however,  did  not  contribute  imme- 
diately to  the  rise  of  radar  astronomy. 

The  radar  and  digital  technology  used  in  those  attempts  on  Venus  was  not  available 
at  the  end  of  World  War  II,  when  the  first  lunar  and  meteor  radar  experiments  were 
conducted.  Moreover,  the  microwave  radars  issued  from  Radiation  Laboratory  research 
were  far  too  weak  for  planetary  or  lunar  work  and  operated  at  frequencies  too  high  to  be 
useful  in  meteor  studies.  Outside  the  Radiation  Laboratory,  though,  U.S.  Army  Signal 
Corps  and  Navy  researchers  had  created  radars,  like  the  SCR-270,  that  were  more  power- 
ful and  operated  at  lower  frequencies,  in  research  and  development  programs  that  were 
less  concentrated  and  conducted  on  a  smaller  scale  than  the  Radiation  Laboratory  effort. 

Wartime  production  created  an  incredible  excess  of  such  radar  equipment.  The  end 
of  fighting  turned  it  into  war  surplus  to  be  auctioned  off,  given  away,  or  buried  as  waste. 
World  War  II  also  begot  a  large  pool  of  scientists  and  engineers  with  radar  expertise  who 
sought  peacetime  scientific  and  technical  careers  at  war's  end.  That  pool  of  expertise, 
when  combined  with  the  cornucopia  of  high-power,  low-frequency  radar  equipment  and 
a  pinch  of  curiosity,  gave  rise  to  radar  astronomy. 

A  catalyst  crucial  to  that  rise  was  ionospheric  research.  In  the  decade  and  a  half 
following  World  War  II,  ionospheric  research  underwent  the  kind  of  swift  growth  that  is 
typical  of  Big  Science.  The  ionospheric  journal  literature  doubled  every  2.9  years  from 
1926  to  1938,  before  stagnating  during  the  war;  but  between  1947  and  1960,  the  literature 
doubled  every  5.8  years,  a  rate  several  times  faster  than  the  growth  rate  of  scientific  liter- 
ature as  a  whole.17  Interest  in  ionospheric  phenomena,  as  expressed  in  the  rapidly 
growing  research  literature,  motivated  many  of  the  first  radar  astronomy  experiments 
undertaken  on  targets  beyond  the  Earth's  atmosphere. 


Project  Diana 


Typical  was  the  first  successful  radar  experiment  aimed  at  the  Moon.  That  experi- 
ment was  performed  with  Signal  Corps  equipment  at  the  Corps'  Evans  Signal  Laboratory, 
near  Belmar,  New  Jersey,  under  the  direction  of  John  H.  DeWitt,  Jr.,  Laboratory  Director. 
DeWitt  was  born  in  Nashville  and  attended  Vanderbilt  University  Engineering  School  for 
two  years.  Vanderbilt  did  not  offer  a  program  in  electrical  engineering,  so  DeWitt 
dropped  out  in  order  to  satisfy  his  interest  in  broadcasting  and  amateur  radio.  In  1929, 
after  building  Nashville's  first  broadcasting  station,  DeWitt  joined  the  Bell  Telephone 
Laboratories  technical  staff  in  New  York  City,  where  he  designed  radio  broadcasting  trans- 
mitters. He  returned  to  Nashville  in  1932  to  become  Chief  Engineer  of  radio  station  WSM. 
Intrigued  by  Karl  Jansky's  discovery  of  "cosmic  noise,"  DeWitt  built  a  radio  telescope  and 
searched  for  radio  signals  from  the  Milky  Way. 

In  1940,  DeWitt  attempted  to  bounce  radio  signals  off  the  Moon  in  order  to  study 
the  Earth's  atmosphere.  He  wrote  in  his  notebook:  "It  occurred  to  me  that  it  might  be 
possible  to  reflect  ultrashort  waves  from  the  moon.  If  this  could  be  done  it  would  open  up 
wide  possibilities  for  the  study  of  the  upper  atmosphere.  So  far  as  I  know  no  one  has  ever 


17.  Gillmor,  "Geospace  and  its  Uses:  The  Restructuring  of  Ionospheric  Physics  Following  World  War  II," 
in  DeMaria,  Grilli,  and  Sebastiani,  pp.  75-84,  especially  pp.  78-79. 

18.  DeWitt  notebook,  21  May  1940,  and  DeWitt  biographical  sketch,  HL  Diana  46  (04),  HAUSACEC. 
There  is  a  rich  literature  on  Jansky's  discovery.  A  good  place  to  start  is  Woodruff  T.  Sullivan  III,  "Karl  Jansky  and 
the  Discovery  of  Extraterrestrial  Radio  Waves,"  in  Sullivan,  ed.,  The  Early  Years  of  Radio  Astronomy:  Reflections  Fifty 
Years  after  Jansky's  Discovery  (New  York:  Cambridge  University  Press,  1984),  pp.  3-42. 


A  METEORIC  START 


sent  waves  off  the  earth  and  measured  their  return  through  the  entire  atmosphere  of  the 
earth."18 

On  the  night  of  20  May  1940,  using  the  receiver  and  80-watt  transmitter  configured 
for  radio  station  WSM,  DeWitt  tried  to  reflect  138-MHz  (2-meter)  radio  waves  off  the 
Moon,  but  he  failed  because  of  insufficient  receiver  sensitivity.  After  joining  the  staff  of 
Bell  Telephone  Laboratories  in  Whippany,  New  Jersey,  in  1942,  where  he  worked  exclu- 
sively on  the  design  of  a  radar  antenna  for  the  Navy,  DeWitt  was  commissioned  in  the 
Signal  Corps  and  was  assigned  to  serve  as  Executive  Officer,  later  as  Director,  of  Evans 
Signal  Laboratory. 

On  10  August  1945,  the  day  after  the  United  States  unleashed  a  second  atomic  bomb 
on  Japan,  military  hostilities  between  the  two  countries  ceased.  DeWitt  was  not  demobi- 
lized immediately,  and  he  began  to  plan  his  pet  project,  the  reflection  of  radio  waves  off 
the  Moon.  He  dubbed  the  scheme  Project  Diana  after  the  Roman  mythological  goddess 
of  the  Moon,  partly  because  "the  Greek  [sic]  mythology  books  said  that  she  had  never 
been  cracked." 

In  September  1945,  DeWitt  assembled  his  team:  Dr.  Harold  D.  Webb,  Herbert  P. 
Kauffman,  E.  King  Stodola,  and  Jack  Mofenson.  Dr.  Walter  S.  McAfee,  in  the  Laboratory's 
Theoretical  Studies  Group,  calculated  the  reflectivity  coefficient  of  the  Moon.  Members 
of  the  Antenna  and  Mechanical  Design  Group,  Research  Section,  and  other  Laboratory 
groups  contributed  too. 

No  attempt  was  made  to  design  major  components  specifically  for  the  experiment. 
The  selection  of  the  receiver,  transmitter,  and  antenna  was  made  from  equipment  already 
on  hand,  including  a  special  crystal-controlled  receiver  and  transmitter  designed  for  the 
Signal  Corps  by  radio  pioneer  Edwin  H.  Armstrong.  Crystal  control  provided  frequency 
stability,  and  the  apparatus  provided  the  power  and  bandwidth  needed.  The  relative  veloc- 
ities of  the  Earth  and  the  Moon  caused  the  return  signal  to  differ  from  the  transmitted 
signal  by  as  much  as  300  Hz,  a  phenomenon  known  as  Doppler  shift.  The  narrow-band 
receiver  permitted  tuning  to  the  exact  radio  frequency  of  the  returning  echo.  As  DeWitt 
later  recalled:  "We  realized  that  the  moon  echoes  would  be  very  weak  so  we  had  to  use  a 
very  narrow  receiver  bandwidth  to  reduce  thermal  noise  to  tolerable  levels. ...We  had  to 
tune  the  receiver  each  time  for  a  slightly  different  frequency  from  that  sent  out  because 
of  the  Doppler  shift  due  to  the  earth's  rotation  and  the  radial  velocity  of  the  moon  at  the 
time."19 

The  echoes  were  received  both  visually,  on  a  nine-inch  cathode-ray  tube,  and  acousti- 
cally, as  a  180-Hz  beep.  The  aerial  was  a  pair  of  "bedspring"  antennas  from  an  SCR-271  sta- 
tionary radar  positioned  side  by  side  to  form  a  32-dipole  array  antenna  and  mounted  on 
a  30-meter  (100-ft)  tower.  The  antenna  had  only  azimuth  control;  it  had  not  been  practi- 
cal to  secure  a  better  mechanism.  Hence,  experiments  were  limited  to  the  rising  and  set- 
ting of  the  Moon. 


19.  DeWitt  to  Trevor  Clark,  18  December  1977,  HL  Diana  46  (04) ;  "Background  Information  on  DeWitt 
Observatory"  and  "U.S.  Army  Electronics  Research  and  Development  Laboratory,  Fort  Monmouth,  New  Jersey," 
March  1963,  HL  Diana  46  (26) ,  HAUSACEC.  For  published  full  descriptions  of  the  equipment  and  experiments, 
see  DeWitt  and  E.  King  Stodola,  "Detection  of  Radio  Signals  Reflected  from  the  Moon,"  Proceedings  of  the  Institute 
of  Radio  Engineers  37  (1949):  229-242;  Jack  Mofenson,  "Radar  Echoes  from  the  Moon,"  Electronics  19  (1946): 
92-98;  and  Herbert  Kauffman,  "A  DX  Record:  To  the  Moon  and  Back,"  QST30  (1946):  65-68. 


TO  SEE  THE  UNSEEN 


Figure  1 

The  "bedspring"  mast  antenna,  U.S.  Army  Signal  Corps,  Ft.  Monmouth,  New  Jersey,  used  by  Lt.  Col.  John  H.  DeWiU,Jr,  to 
bounce  radar  echoes  off  the  Moon  on  10  January  1946.  Two  antennas  from  SCR-271  stationary  radars  were  positioned  side 
by  side  to  form  a  32-dipole  array  aerial  and  were  mounted  on  a  100-fi  (3frmeter)  tower.  (Courtesy  of  the  U.S.  Army 
Communications-Electronics  Museum,  Ft.  Monmouth,  New  Jersey.) 


A  METEORIC  START 


The  Signal  Corps  tried  several  times,  but  without  success.  'The  equipment  was  very 
haywire,"  recalled  DeWitt.  Finally,  at  moonrise,  11:48  A.M.,  on  10  January  1946,  they 
aimed  the  antenna  at  the  horizon  and  began  transmitting.  Ironically,  DeWitt  was  not  pre- 
sent: "I  was  over  in  Belmar  having  lunch  and  picking  up  some  items  like  cigarettes  at  the 
drug  store  (stopped  smoking  1952  thank  God)."20  The  first  signals  were  detected  at  11:58 
A.M.,  and  the  experiment  was  concluded  at  12:09  P.M.,  when  the  Moon  moved  out  of  the 
radar's  range.  The  radio  waves  had  taken  about  2.5  seconds  to  travel  from  New  Jersey  to 
the  Moon  and  back,  a  distance  of  over  800,000  km.  The  experiment  was  repeated  daily 
over  the  next  three  days  and  on  eight  more  days  later  that  month. 

The  War  Department  withheld  announcement  of  the  success  until  the  night  of 
24  January  1946.  By  then,  a  press  release  explained,  "the  Signal  Corps  was  certain  beyond 
doubt  that  the  experiment  was  successful  and  that  the  results  achieved  were  pain-staking- 
ly  [sic]  verified."21 

As  DeWitt  recounted  years  later:  "We  had  trouble  with  General  Van  Deusen  our  head 
of  R&D  in  Washington.  When  my  C.O.  Col.  Victor  Conrad  told  him  about  it  over  the  tele- 
phone the  General  did  not  want  the  story  released  until  it  was  confirmed  by  outsiders  for 
fear  it  would  embarrass  the  Sigfnal].  C[orps]."  Two  outsiders  from  the  Radiation 
Laboratory,  George  E.  Valley,  Jr.  and  Donald  G.  Fink,  arrived  and,  with  Gen.  Van  Deusen, 
observed  a  moonrise  test  of  the  system  carried  out  under  the  direction  of  King  Stodola. 
Nothing  happened.  DeWitt  explained:  "You  can  imagine  that  at  this  point  I  was  dying. 
Shortly,  a  big  truck  passed  by  on  the  road  next  to  the  equipment  and  immediately  the 
echoes  popped  up.  I  will  always  believe  that  one  of  the  crystals  was  not  oscillating  until  it 
was  shaken  up  or  there  was  a  loose  connection  which  fixed  itself.  Everyone  cheered 
except  the  General  who  tried  to  look  pleased."22 

Although  he  had  had  other  motives  for  undertaking  Project  Diana,  DeWitt  had 
received  a  directive  from  the  Chief  Signal  Officer,  the  head  of  the  Signal  Corps,  to  devel- 
op radars  capable  of  detecting  missiles  coming  from  the  Soviet  Union.  No  missiles  were 
available  for  tests,  so  the  Moon  experiment  stood  in  their  place.  Several  years  later,  the 
Signal  Corps  erected  a  new  50-ft  (15-meter)  Diana  antenna  and  108-MHz  transmitter  for 
ionospheric  research.  It  carried  out  further  lunar  echo  studies  and  participated  in  the 
tracking  of  Apollo  launches.23 

The  news  also  hit  the  popular  press.  The  implications  of  the  Signal  Corps  experi- 
ment were  grasped  by  the  War  Department,  although  Newsweek  cynically  cast  doubt  on  the 
War  Department's  predictions  by  calling  them  worthy  of  Jules  Verne.  Among  those  War 
Department  predictions  were  the  accurate  topographical  mapping  of  the  Moon  and  plan- 
ets, measurement  and  analysis  of  the  ionosphere,  and  radio  control  from  Earth  of  "space 
ships"  and  'jet  or  rocket-controlled  missiles,  circling  the  Earth  above  the  stratosphere." 
Time  reported  that  Diana  might  provide  a  test  of  Albert  Einstein's  Theory  of  Relativity.  In 
contrast  to  the  typically  up-beat  mood  of  Life,  both  news  magazines  were  skeptical,  and 


20.  DeWitt  replies  to  Clark  questions,  HL  Diana  46  (04) ,  HAUSACEC. 

21 .  HL  Radar  46  (07) ,  HAUSACEC;  Harold  D.  Webb,  "Project  Diana:  Army  Radar  Contacts  the  Moon," 
Sky  and  Telescope  5  (1946):  3-6. 

22.  DeWitt  to  Clark,  18  December  1977,  HL  Diana  46  (04),  HAUSACEC;  Guerlac,  Radar  in  World  War 
II,  1:380  and  382,  2:702. 

23.  DeWitt,  telephone  conversation,  14  June  1993;  Materials  in  folders  HL  Diana  46  (25),  HL  Diana  46 
(28),  and  HL  Diana  46  (33),  USASEL  Research  &  Development  Summary  vol.  5,  no.  3  (10  February  1958):  58,  in 
"Signal  Corps  Engineering  Laboratory Journal/R&D  Summary,"  and  Mimmouth  Message,  7  November  1963,  n.p., 
in  "Biographical  Files,"  "Daniels,  Fred  Bryan,"  HAUSACEC;  Daniels,  "Radar  Determination  of  the  Scattering 
Properties  of  the  Moon,"  Nature  187  (1960):  399;  and  idem.,  "A  Theory  of  Radar  Reflection  from  the  Moon  and 
Planets,"  Journal  of  Geophysical  Research  66  (1961):  1781-1788. 


1 0  TO  SEE  THE  UNSEEN 


rightly  so;  yet  all  of  the  predictions  made  by  the  War  Department,  including  the  relativity 
test,  have  come  true  in  the  manner  of  a  Jules  Verne  novel.24 

Zoltan  Bay 

Less  than  a  month  after  DeWitt's  initial  experiment,  a  radar  in  Hungary  replicated 
his  results.  The  Hungarian  apparatus  differed  from  that  of  DeWitt  in  one  key  respect;  it 
utilized  a  procedure,  called  integration,  that  was  essential  to  the  first  attempt  to  bounce 
radar  waves  off  Venus  and  that  later  became  a  standard  planetary  radar  technique.  The 
procedure's  inventor  was  Hungarian  physicist  Zoltan  Bay. 

Bay  graduated  with  highest  honors  from  Budapest  University  with  a  Ph.D.  in  physics 
in  1926.  Like  many  Hungarian  physicists  before  him,  Bay  spent  several  years  in  Berlin  on 
scholarships,  doing  research  at  both  the  prestigious  Physikalisch-Technische-Reichanstalt 
and  the  Physikalisch-Chemisches-Institut  of  the  University  of  Berlin.  The  results  of  his 
research  tour  of  Berlin  earned  Bay  the  Chair  of  Theoretical  Physics  at  the  University  of 
Szeged  (Hungary),  where  he  taught  and  conducted  research  on  high  intensity  gas  dis- 
charges. 

Bay  left  the  University  of  Szeged  when  the  United  Incandescent  Lamps  and  Electric 
Company  (Tungsram)  invited  him  to  head  its  industrial  research  laboratory  in  Budapest. 
Tungsram  was  the  third  largest  manufacturer  of  incandescent  lamps,  radio  tubes,  and 
radio  receivers  in  Europe  and  supplied  a  fifth  of  all  radio  tubes.  As  laboratory  head, 
Zoltan  Bay  oversaw  the  improvement  of  high-intensity  gas  discharge  lamps,  fluorescent 
lamps,  radio  tubes,  radio  receiver  circuitry,  and  decimeter  radio  wave  techniques.25 

Although  Hungary  sought  to  stay  out  of  the  war  through  diplomatic  maneuvering, 
the  threat  of  a  German  invasion  remained  real.  In  the  fall  of  1942,  the  Hungarian  Minister 
of  Defense  asked  Bay  to  organize  an  early-warning  system.  He  achieved  that  goal,  though 
the  Germans  occupied  Hungary  anyway.  In  March  1944,  Bay  recommended  using  the 
radar  for  scientific  experimentation,  including  the  detection  of  radar  waves  bounced  off 
the  Moon.  The  scientific  interest  in  the  experiment  arose  from  the  opportunity  to  test  the 
theoretical  notion  that  short  wavelength  radio  waves  could  pass  through  the  ionosphere 
without  considerable  absorption  or  reflection.  Bay's  calculations,  however,  showed  that 
the  equipment  would  be  incapable  of  detecting  the  signals,  since  they  would  be  signifi- 
cantly below  the  receiver's  noise  level. 

The  critical  difference  between  the  American  and  Hungarian  apparatus  was  fre- 
quency stability,  which  DeWitt  achieved  through  crystal  control  in  both  the  transmitter 
and  receiver.  Without  frequency  stability,  Bay  had  to  find  a  means  of  accommodating  the 
frequency  drifts  of  the  transmitter  and  receiver  and  the  resulting  inferior  signal-to-noise 
ratio.  He  chose  to  boost  the  signal-to-noise  ratio.  His  solution  was  both  ingenious  and  far- 
reaching  in  its  impact. 

Bay  devised  a  process  he  called  cumulation,  which  is  known  today  as  integration.  His 
integrating  device  consisted  of  ten  coulometers,  in  which  electric  currents  broke  down  a 
watery  solution  and  released  hydrogen  gas.  The  amount  of  gas  released  was  directly 
proportional  to  the  quantity  of  electric  current.  The  coulometers  were  connected  to  the 
output  of  the  radar  receiver  through  a  rotating  switch.  The  radar  echoes  were  expected 


24.  "Diana,"  Time  Vol.  47,  no.  5  (4  February  1946):  84;  "Radar  Bounces  Echo  off  the  Moon  to  Throw 
Light  on  Lunar  Riddle,"  Newsweek  vol.  27,  no.  5  (4  February  1946):  76-77;  "Man  Reaches  Moon  with  Radar,"  Life 
vol.  20,  no.  5  (4  February  1946):  30. 

25.  Zoltan  Bay,  Life  is  Stronger,  trans.  Margaret  Blakey  Hajdu  (Budapest:  Puski  Publisher,  1991),  pp.  5 
and  17-18;  Francis  S.  Wagner,  Zoltan  Bay,  Atomic  Physicist:  A  Pioneer  of  Spaa  Research  (Budapest:  Akademiai  Kiado, 
1985),  pp.  23-27,  29,  31-32;  Wagner,  Fifty  Years  in  the  Laboratory:  A  Survey  of  the  Research  Activities  of  Physicist  Zoltan 
Bay  (Center  Square,  PA:  Alpha  Publications,  1977),  p.  1. 


A  METEORIC  START 


11 


to  return  from  the  Moon  in  less  than  three  seconds,  so  the  rotating  switch  made  a  sweep 
of  the  ten  coulometers  every  three  seconds.  The  release  of  hydrogen  gas  left  a  record  of 
both  the  echo  signal  and  the  receiver  noise.  As  the  number  of  signal  echoes  and  sweeps 
of  the  coulometers  added  up,  the  signal-to-noise  ratio  improved.  By  increasing  the  total 
number  of  signal  echoes,  Bay  believed  that  any  signal  could  be  raised  above  noise  level 
and  made  observable,  regardless  of  its  amplitude  and  the  value  of  the  signal-to-noise 
ratio.26  Because  the  signal  echoes  have  a  more-or-less  fixed  structure,  and  the  noise  varies 
from  pulse  to  pulse,  echoes  add  up  faster  than  noise. 

Despite  the  conceptual  breakthrough  of  the  coulometer  integrator,  the  construction 
and  testing  of  the  apparatus  remained  to  be  carried  out.  The  menace  of  air  raids  drove 
the  Tungsram  research  laboratory  into  the  countryside  in  the  fall  of  1944.  The  subsequent 
siege  of  Budapest  twice  interrupted  the  work  of  Bay  and  his  team  until  March  1945.  The 
Ministry  of  Defense  furnished  Bay  with  war  surplus  parts  for  a  2.5-meter  (120-MHz)  radar 

manufactured  by  the 
Standard  Electrical  Co.,  a 
Hungarian  subsidiary  of  ITT. 
Work  was  again  interrupted 
when  the  laboratory  was  dis- 
mantled and  all  equipment, 
including  that  for  the  lunar 
radar  experiment,  was  carried 
off  to  the  Soviet  Union.  For  a 
third  time,  construction  of 
entirely  new  equipment  start- 
ed in  the  workshops  of  the 
Tungsram  Research  Laboratory, 
beginning  August  1945  and 
ending  January  1946. 

Electrical  disturbances 
in  the  Tungsram  plant  were 
so  great  that  measurements 
and  tuning  had  to  be  done  in 
the  late  afternoon  or  at  night. 
The  experiments  were  carried 
out  on  6  February  and  8  May 
1946  at  night  by  a  pair  of 
researchers.  Without  the 
handicap  of  operating  in  a 
war  zone,  Bay  probably  would 
have  beaten  the  Signal  Corps 
to  the  Moon,  although  he 
could  not  have  been  aware  of 
DeWitt's  experiment.  More 

Figure  2  .  .    l        ,  ,  , 

Antenna  built  and  used  by  Zoltdn  Bay  to  bounce  radar  echoes  off  the  Moon  in  mportantly,  though,  he 
February  and  May  1946.  (Courtesy  of  Mrs.  Julia  Bay)  invented  the  technique  of 


26.      Bay,  "Reflection  of  Microwaves  from  the  Moon,"  Hungarica  Acta  Physica  1  (1947):  1-6;  Bay,  Life  is 
Stronger,  pp.  20  &  29;  Wagner,  Zoltdn,  pp.  39-40;  Wagner,  Fifty  Years,  pp.  1-2. 


1 2  TO  SEE  THE  UNSEEN 


long-time  integration  generally  used  in  radar  astronomy.  As  the  American  radio 
astronomers  Alex  G.  Smith  and  Thomas  D.  Carr  wrote  some  years  later:  'The  additional 
tremendous  increase  in  sensitivity  necessary  to  obtain  radar  echoes  from  Venus  has  been 
attained  largely  through  the  use  of  long-time  integration  techniques  for  detecting  peri- 
odic signals  that  are  far  below  the  background  noise  level.  The  unique  method  devised  by 
Bay  in  his  pioneer  lunar  radar  investigations  is  an  example  of  such  a  technique."27 

Both  Zoltan  Bay  and  John  DeWitt  had  fired  shots  heard  round  the  world,  but  there 
was  no  revolution,  although  others  either  proposed  or  attempted  lunar  radar  experiments 
in  the  years  immediately  following  World  War  II.  Each  man  engaged  in  other  projects 
shortly  after  completing  his  experiment.  Bay  left  Hungary  for  the  United  States,  where  he 
taught  at  George  Washington  University  and  worked  for  the  National  Bureau  of 
Standards,  while  DeWitt  re-entered  radio  broadcasting  and  pursued  his  interest  in  astron- 
omy.28 

As  an  ongoing  scientific  activity,  radar  astronomy  did  not  begin  with  the  spectacular 
and  singular  experiments  of  DeWitt  and  Bay,  but  with  an  interest  in  meteors  shared  by 
researchers  in  Britain,  Canada,  and  the  United  States.  Big  Science,  that  is,  ionospheric 
physics  and  secure  military  communications,  largely  motivated  that  research.  Moreover, 
just  as  the  availability  of  captured  V-2  parts  made  possible  rocket-based  ionospheric 
research  after  the  war,29  so  war-surplus  radars  facilitated  the  emergence  of  radar  astrono- 
my. Like  the  exploration  of  the  ionosphere  with  rockets,  radar  astronomy  was  driven  by 
the  availability  of  technology. 

Meteors  and  Auroras 

Radar  meteor  studies,  like  much  of  radar  history,  grew  out  of  ionospheric  research. 
In  the  1930s,  ionospheric  researchers  became  interested  in  meteors  when  it  was  hypothe- 
sized that  the  trail  of  electrons  and  ions  left  behind  by  falling  meteors  caused  fluctuations 
in  the  density  of  the  ionosphere.30  Edward  Appleton  and  others  with  the  Radio  Research 
Board  of  the  British  Department  of  Scientific  and  Industrial  Research,  the  same  organi- 
zation with  which  Watson-Watt  had  been  associated,  used  war-surplus  radar  furnished  by 


27.  Smith  and  Carr,  Radio  Exploration  of  the  Planetary  System  (New  York:  D.  Van  Nostrand,  1964) ,  p.  123; 
Bay,  "Reflection,"  pp.  2,  7-15  and  18-19;  P.  Vajda  andJA.  White,  Thirtieth  Anniversary  of  Zoltan  Bay's  Pioneer 
Lunar  Radar  Investigations  and  Modern  Radar  Astronomy,"  Acta  Physica  Academiae  Scientiarum  Hungaricae  40 
(1976):  65-70;  Wagner,  Zoltan,  pp.  40-41.  Bay,  Life  is  Stronger,  pp.  103-124,  describes  the  looting  and  dismantling 
of  the  Tungsram  works  by  armed  agents  of  the  Soviet  Union. 

28.  DeWitt,  telephone  conversation,  14  June  1993;  DeWitt  biographical  sketch,  HL  Diana  46  (04), 
HAUSACEC;  Wagner,  Zoltan,  p.  49;  Wagner,  Fifty  Years,  p.  2. 

Among  the  others  were  Thomas  Gold,  Von  Eshleman,  and  A.C.  Bernard  Lovell.  Gold,  retired  Cornell 
University  professor  of  astronomy,  claims  to  have  proposed  a  lunar  radar  experiment  to  the  British  Admiralty 
during  World  War  II;  Eshleman,  Stanford  University  professor  of  electrical  engineering,  unsuccessfully  attempt- 
ed a  lunar  radar  experiment  aboard  the  U.S.S.  Missouri  in  1946,  while  returning  from  the  war;  and  Lovell  pro- 
posed a  lunar  bounce  experiment  in  a  paper  of  May  1946.  Gold  14  December  1993,  Eshleman  9  May  1994,  and 
Lovell,  "Astronomer  by  Chance"  manuscript,  February  1988,  Lovell  materials,  p.  183. 

Even  earlier,  during  the  1920s,  the  Navy  unsuccessfully  attempted  to  bounce  a  32-KHz,  500-watt  radio  sig- 
nal off  the  Moon.  A.  Hoyt  Taylor,  Radio  Reminiscences:  A  Half  Century  (Washington:  NRL,  1948) ,  p.  133. 1  am  grate- 
ful to  Louis  Brown  for  pointing  out  this  reference. 

29.  See  DeVorkin,  passim. 

30.  A.M.  Skellett,  The  Effect  of  Meteors  on  Radio  Transmission  through  the  Kennelly-Heaviside  Layer," 
Physical  Review  37  (1931):  1668;  Skellett,  The  Ionizing  Effect  of  Meteors,"  Proceedings  of  the  Institute  of  Radio 
Engineers  23  (1935):  132-149.  Skellett  was  a  part-time  graduate  student  in  astronomy  at  Princeton  University  and 
an  employee  of  Bell  Telephone  Laboratories,  New  York  City.  The  research  described  in  this  article  came  out  of 
a  study  of  the  American  Telegraph  and  Telephone  Company  transatlantic  short-wave  telephone  circuits  in 
1930-1932,  and  how  they  were  affected  by  meteor  ionization.  DeVorkin,  p.  275. 


A  METEORIC  START  1 3 


the  Air  Ministry  to  study  meteors  immediately  after  World  War  II.  They  concluded  that 
meteors  caused  abnormal  bursts  of  ionization  as  they  passed  through  the  ionosphere.31 

During  the  war,  the  military  had  investigated  meteor  trails  with  radar.  When  the 
Germans  started  bombarding  London  with  V2  rockets,  the  Army's  gun-laying  radars  were 
hastily  pressed  into  service  to  detect  the  radar  reflections  from  the  rockets  during  their 
flight  in  order  to  give  some  warning  of  their  arrival.  In  many  cases  alarms  were  sounded, 
but  no  rockets  were  aloft.  James  S.  Hey,  a  physicist  with  the  Operational  Research  Group, 
was  charged  with  investigating  these  mistaken  sightings.  He  believed  that  the  false  echoes 
probably  originated  in  the  ionosphere  and  might  be  associated  with  meteors. 

Hey  began  studying  the  impact  of  meteors  on  the  ionosphere  in  October  1944,  using 
Army  radar  equipment  at  several  locations  until  the  end  of  the  war.  The  Operational 
Research  Group,  Hey,  G.  S.  Stewart  (electrical  engineer),  S.  J.  Parsons  (electrical  and 
mechanical  engineer),  and  J.  W.  Phillips  (mathematician),  found  a  correlation  between 
visual  sightings  and  radar  echoes  during  the  Giacobinid  meteor  shower  of  October  1946. 
Moreover,  by  using  an  improved  photographic  technique  that  better  captured  the  echoes 
on  the  radar  screen,  they  were  able  to  determine  the  velocity  of  the  meteors. 

Neither  Hey  nor  Appleton  pursued  their  radar  investigations  of  meteors.  During  the 
war,  Hey  had  detected  radio  emissions  from  the  Sun  and  the  first  discrete  source  of  radio 
emission  outside  the  solar  system  in  the  direction  of  Cygnus.  He  left  the  Operational 
Research  Group  for  the  Royal  Radar  Establishment  at  Malvern,  where  he  and  his  col- 
leagues carried  on  research  in  radio  astronomy.  Appleton,  by  1946  a  Nobel  Laureate  and 
Secretary  of  the  Department  of  Scientific  and  Industrial  Research,  also  became  thor- 
oughly involved  in  the  development  of  radio  astronomy  and  became  a  member  of  the 
Radio  Astronomy  Committee  of  the  Royal  Astronomical  Society  in  1949.32 

Radar  astronomy,  however,  did  gain  a  foothold  in  Britain  at  the  University  of 
Manchester  under  A.  C.  (later  Sir)  Bernard  Lovell,  director  of  the  University's  Jodrell 
Bank  Experimental  Station.  During  the  war,  Lovell  had  been  one  of  many  scientists  work- 
ing on  microwave  radar.33  His  superior,  the  head  of  the  Physics  Department,  was  Patrick 
M.  S.  Blackett,  a  member  of  the  Committee  for  the  Scientific  Survey  of  Air  Defence  that 
approved  Watson-Watt's  radar  memorandum.  With  the  help  of  Hey  and  Parsons,  Lovell 
borrowed  some  Army  radar  equipment.  Finding  too  much  interference  in  Manchester,  he 
moved  to  the  University's  botanical  research  gardens,  which  became  the  Jodrell  Bank 
Experimental  Station.  Lovell  equipped  the  station  with  complete  war-surplus  radar  sys- 
tems, such  as  a  4.2-meter  gun-laying  radar  and  a  mobile  Park  Royal  radar.  He  purchased 
at  rock-bottom  prices  or  borrowed  the  radars  from  the  Air  Ministry,  Army,  and  Navy, 
which  were  discarding  the  equipment  down  mine  shafts. 


31.  Appleton  and  R.  Naismith,  "The  Radio  Detection  of  Meteor  Trails  and  Allied  Phenomena," 
Proceeding  of  the  Physical  Society  59  (1947):  461-473;  James  S.  Hey  and  G.S.  Stewart,  "Radar  Observations  of 
Meteors,"  Proceedings  of  the  Physical  Society  59  (1947):  858;  Lovell,  Meteor  Astronomy  (Oxford:  Clarendon  Press, 
1954),  pp.  23-24. 

32.  Hey,  The  Evolution  of  Radio  Astronomy  (New  York:  Science  History  Publications,  1973) ,  pp.  19-23  and 
33-34;  Lovell,  The  Story  of  Jodrell  Bank  (London:  Oxford  University  Press,  1968),  p.  5;  Hey,  Stewart,  and  SJ. 
Parsons,  "Radar  Observations  of  the  Giacobinid  Meteor  Shower,"  Monthly  Notices  of  the  Royal  Astronomical  Society 
107  (1947):  176-183;  Hey  and  Stewart,  "Radar  Observations  of  Meteors,"  Proceedings  of  the  Physical  Society  59 
(1947):  858-860  and  881-882;  Hey,  The  Radio  Universe  (New  York:  Pergamon  Press,  1971),  pp.  131-134;  Lovell, 
Meteor  Astronomy,  pp.  28-29  and  50-52;  Peter  Robertson,  Beyond  Southern  Skies:  Radio  Astronomy  and  the  Parkes 
Telescope  (New  York:  Cambridge  University  Press,   1992),  p.  39;  Dudley  Saward,  Bernard  Lovell,  a  Biography 
(London:  Robert  Hale,  1984),  pp.  142-145;  David  O.  Edge  and  Michael  J.  Mulkay,  Astronomy  Transformed:  The 
Emergence  of  Radio  Astronomy  in  Britain  (New  York:  Wiley,  1976),  pp.  12-14.  For  a  brief  historical  overview  of  the 
Royal  Radar  Establishment,  see  Ernest  H.  Pulley,  "History  of  the  RSRE,"  RSRE  Research  Review  9  (1985):  165-174; 
and  D.H.  Tomin,  "The  RSRE:  A  Brief  History  from  Earliest  Times  to  Present  Day,"  lEEReviewM  (1988) :  403-407. 
This  major  applied  sciene  institution  deserves  a  more  rigorously  researched  history. 

33.  See  Lovell,  Echoes  of  War:  The  Story  of  //^S  Radar  (Bristol:  Adam  Hilger,  1991).  Lovell's  wartime 
records  are  stored  at  the  Imperial  War  Museum,  Lambeth  Road,  London. 


14 


TO  SEE  THE  UNSEEN 


Figure  3 

Thejodrell  Bank  staff  1951  in  front  of  the  4.2-meter  searchlight  aerial  used  in  some  meteor  radar  experiments.  Sir  Bernard 
Lavell  is  in  the  center  front.  (Courtesy  of  the  Director  of  the  Nuffteld  Radio  Astronomy  Laboratories,  Jodrell  Bank.) 

Originally,  Lovell  wanted  to  undertake  research  on  cosmic  rays,  which  had  been 
Blackett's  interest,  too.  One  of  the  primary  research  objectives  of  the  Jodrell  Bank  facility, 
as  well  as  one  of  the  fundamental  reasons  for  its  founding,  was  cosmic  ray  research.  Indeed, 
the  interest  in  cosmic  ray  research  also  lay  behind  the  design  and  construction  of  the 
76-meter  (250-ft)  Jodrell  Bank  telescope.  The  search  for  cosmic  rays  never  succeeded,  how- 
ever; Blackett  and  Lovell  had  introduced  a  significant  error  into  their  initial  calculations. 

Fortuitously,  though,  in  the  course  of  looking  for  cosmic  rays,  Lovell  came  to  realize 
that  they  were  receiving  echoes  from  meteor  ionization  trails,  and  his  small  group  of 
Jodrell  Bank  investigators  began  to  concentrate  on  this  more  fertile  line  of  research. 
Nicolai  Herlofson,  a  Norwegian  meteorologist  who  had  recently  joined  the  Department 
of  Physics,  put  Lovell  in  contact  with  the  director  of  the  Meteor  Section  of  the  British 
Astronomical  Association,  J.  P.  Manning  Prentice,  a  lawyer  and  amateur  astronomer  with 
a  passion  for  meteors.  Also  joining  the  Jodrell  Bank  team  was  John  A.  Clegg,  a  physics 
teacher  whom  Lovell  had  known  during  the  war.  Clegg  was  a  doctoral  candidate  at  the 
University  of  Manchester  and  an  expert  in  antenna  design.  He  remained  at  Jodrell  Bank 
until  1951  and  eventually  landed  a  position  teaching  physics  in  Nigeria.  Clegg  converted 
an  Army  searchlight  into  a  radar  antenna  for  studying  meteors.34 


34.  Lovell  11  January  1994;  Lovell,  Jodrell  Bank,  pp.  5-8,  10;  Lovell,  Meteor  Astronomy,  pp.  55-63;  Edge 
and  Mulkay,  pp.  15-16;  Saward,  pp.  129-131;  R.H.  Brown  and  Lovell,  "Large  Radio  Telescopes  and  their  Use  in 
Radio  Astronomy,"  Vistas  in  Astronomy  1  (1955):  542-560;  Blackett  and  Lovell,  "Radio  Echoes  and  Cosmic  Ray 
Showers,"  Proceedings  of  the  Royal  Society  of  London  ser.  A,  vol.  177  (1941):  183-186;  and  Lovell,  "The  Blackett- 
Eckersley-Lovell  Correspondence  of  World  War  II  and  the  Origin  of  Jodrell  Bank,"  Notes  and  Records  of  the  Royal 
Society  of  London  47  ( 1993) :  1 19-131.  For  documents  relating  to  equipment  on  loan  from  the  Ministry  of  Aviation, 
the  War  Office,  the  Royal  Radar  Establishment,  the  Admiralty,  and  the  Air  Ministry  as  late  as  the  1960s,  see 
10/51,  "Accounts,  "JBA. 


A  METEORIC  START  15 


The  small  group  of  professional  and  amateur  scientists  began  radar  observations  of 
the  Perseid  meteor  showers  in  late  July  and  August  1946.  When  Prentice  spotted  a  mete- 
or, he  shouted.  His  sightings  usually,  though  not  always,  correlated  with  an  echo  on  the 
radar  screen.  Lovell  thought  that  the  radar  echoes  that  did  not  correlate  with  Prentice's 
sightings  might  have  been  ionization  trails  created  by  cosmic  ray  showers.  He  did  not 
believe,  initially,  that  the  radar  might  be  detecting  meteors  too  small  to  be  seen  by  the 
human  eye. 

The  next  opportunity  for  a  radar  study  of  meteors  came  on  the  night  of  9  October 
1946,  when  the  Earth  crossed  the  orbit  of  the  Giacobini-Zinner  comet.  Astronomers  antic- 
ipated a  spectacular  meteor  shower.  A  motion  picture  camera  captured  the  radar  echoes 
on  film.  The  shower  peaked  around  3  A.M.;  a  radar  echo  rate  of  nearly  a  thousand  mete- 
ors per  hour  was  recorded.  Lovell  recalled  that  "the  spectacle  was  memorable.  It  was  like 
a  great  array  of  rockets  coming  towards  one."35 

The  dramatic  correlation  of  the  echo  rate  with  the  meteors  visible  in  the  sky  finally 
convinced  Lovell  and  everyone  else  that  the  radar  echoes  came  from  meteor  ionization 
trails,  although  it  was  equally  obvious  that  many  peculiarities  needed  to  be  investigated. 
The  Jodrell  Bank  researchers  learned  that  the  best  results  were  obtained  when  the  aerial 
was  positioned  at  a  right  angle  to  the  radiant,  the  point  in  the  sky  from  which  meteor 
showers  appear  to  emanate.  When  the  aerial  was  pointed  at  the  radiant,  the  echoes  on  the 
cathode-ray  tube  disappeared  almost  completely.36 

Next  joining  the  Jodrell  Bank  meteor  group,  in  December  1946,  was  a  doctoral 
student  from  New  Zealand,  Clifton  D.  Ellyett,  followed  in  January  1947  by  a  Cambridge 
graduate,  John  G.  Davies.  Nicolai  Herlofson  developed  a  model  of  meteor  trail  ionization 
that  Davies  and  Ellyett  used  to  calculate  meteor  velocities  based  on  the  diffraction  pattern 
produced  during  the  formation  of  meteor  trails.  Clegg  devised  a  radar  technique  for 
determining  their  radiant.37 

At  this  point,  the  Jodrell  Bank  investigators  had  powerful  radar  techniques  for  study- 
ing meteors  that  were  unavailable  elsewhere,  particularly  the  ability  to  detect  and  study 
previously  unknown  and  unobservable  daytime  meteor  showers.  Lovell  and  his  colleagues 
now  became  aware  of  the  dispute  over  the  nature  of  meteors  and  decided  to  attempt  its 
resolution  with  these  techniques.38 

Astronomers  specializing  in  meteors  were  concerned  with  the  nature  of  sporadic 
meteors.  One  type  of  meteor  enters  the  atmosphere  from  what  appears  to  be  a  single 
point,  the  radiant.  Most  meteors,  however,  are  not  part  of  a  shower,  but  appear  to  arrive 
irregularly  from  all  directions  and  are  called  sporadic  meteors.  Most  astronomers  believed 
that  sporadic  meteors  came  from  interstellar  space;  others  argued  that  they  were  part  of 
the  solar  system. 

The  debate  could  be  resolved  by  determining  the  paths  of  sporadic  meteors.  If  they 
followed  parabolic  or  elliptical  paths,  they  orbited  the  Sun;  if  their  orbit  were  hyperbolic, 
they  had  an  interstellar  origin.  The  paths  of  sporadic  meteors  could  be  determined  by  an 
accurate  measurement  of  both  their  velocities  and  radiants,  but  optical  means  were  insuf- 
ficiently precise  to  give  unambiguous  results.  Fred  L.  Whipple,  future  director  of  the 


35.  Lovell  1 1  January  1994;  Lovell,  Jodrell  Bank,  pp.  7-8,  10. 

36.  Lovell  1 1  January  1994;  Lovell,/odre//  Bank,  pp.  8-10;  Lovell,  Clegg,  and  Congreve  J.  Banwell,  "Radio 
Echo  Observations  of  the  Giacobinid  Meteors  1946,"  Monthly  Notices  of  the  Royal  Astronomical  Society  107  (1947): 
164-175.  Banwell  was  a  New  Zealand  veteran  of  the  Telecommunications  Research  Establishment  wartime  radar 
effort  and  an  expert  on  receiver  electronics. 

37.  Saward,  p.  137;  Herlofson,  The  Theory  of  Meteor  Ionization,"  Reports  on  Progress  in  Physics  11 
( 1946-47) :  444-454;  Ellyett  and  Davies,  "Velocity  of  Meteors  Measured  by  Diffraction  of  Radio  Waves  from  Trails 
during  Formation,"  Nature  161  (1948):  596-597;  Clegg,  "Determination  of  Meteor  Radiants  by  Observation  of 
Radio  Echoes  from  Meteor  Trails,"  Philosophical  Magazine  ser.  7,  vol.  39  ( 1948) :  577-594;  Davies  and  Lovell,  "Radio 
Echo  Studies  of  Meteors,"  Vistas  in  Astronomy  1  (1955):  585-598,  provides  a  summary  of  meteor  research  at  Jodrell 
Bank. 

38.  IJQ\C\\,  JodreU  Bank,  p.  12;  Lovell,  Meteor  Astronomy,  pp.  358-383. 


1 6  TO  SEE  THE  UNSEEN 


Harvard  College  Observatory,  a  leading  center  of  United  States  meteor  research,  attempt- 
ed state-of-the-art  optical  studies  of  meteors  with  the  Super  Schmidt  camera,  but  the  first 
one  was  not  operational  until  May  1951,  at  Las  Cruces,  New  Mexico.39 

Radar  astronomers  thus  attempted  to  accomplish  what  optical  methods  had  failed  to 
achieve.  Such  has  been  the  pattern  of  radar  astronomy  to  the  present.  Between  1948  and 
1950,  Lovell,  Davies,  and  Mary  Almond,  a  doctoral  student,  undertook  a  long  series  of  spo- 
radic meteor  velocity  measurements.  They  found  no  evidence  for  a  significant  hyperbolic 
velocity  component;  that  is,  there  was  no  evidence  for  sporadic  meteors  coming  from 
interstellar  space.  They  then  extended  their  work  to  fainter  and  smaller  meteors  with  sim- 
ilar results. 

The  Jodrell  Bank  radar  meteor  studies  determined  unambiguously  that  meteors 
form  part  of  the  solar  system.  As  Whipple  declared  in  1955,  "We  may  now  accept  as  proven 
the  fact  that  bodies  moving  in  hyperbolic  orbits  about  the  sun  play  no  important  role  in 
producing  meteoric  phenomena  brighter  than  about  the  8th  effective  magnitude."40 
Astronomers  describe  the  brightness  of  a  body  in  terms  of  magnitude;  the  larger  the  mag- 
nitude, the  fainter  the  body. 

The  highly  convincing  evidence  of  the  Jodrell  Bank  scientists  was  corroborated  by 
Canadian  radar  research  carried  out  by  researchers  of  the  Radio  and  Electrical 
Engineering  Division  of  the  National  Research  Council  under  Donald  W.  R.  McKinley. 
McKinley  had  joined  the  Council's  Radio  Section  (later  Branch)  before  World  War  II  and, 
like  Lovell,  had  participated  actively  in  wartime  radar  work. 

McKinley  conducted  his  meteor  research  with  radars  built  around  Ottawa  in  1947 
and  1948  as  part  of  various  National  Research  Council  laboratories,  such  as  the  Flight 
Research  Center  at  Arnprior  Airport.  Earle  L.  R.  Webb,  Radio  and  Electrical  Engineering 
Division  of  the  National  Research  Council,  supervised  the  design,  construction,  and  oper- 
ation of  the  radar  equipment.  From  as  early  as  the  summer  of  1947,  the  Canadian  radar 
studies  were  undertaken  jointly  with  Peter  M.  Millman  of  the  Dominion  Observatory. 
They  coordinated  spectrographic,  photographic,  radar,  and  visual  observations.  The 
National  Research  Council  investigators  employed  the  Jodrell  Bank  technique  to  deter- 
mine meteor  velocities,  a  benefit  of  following  in  the  footsteps  of  the  British.41 

Their  first  radar  observations  took  place  during  the  Perseid  shower  of  August  1947, 
as  the  first  radar  station  reached  completion.  Later  studies  collected  data  from  the 
Geminid  shower  of  December  1947  and  the  Lyrid  shower  of  April  1948,  with  more  radar 
stations  brought  into  play  as  they  became  available.  Following  the  success  of  Jodrell  Bank, 


39.  Ron   Doel,   "Unpacking  a  Myth:   Interdisciplinary  Research   and   the  Growth   of  Solar  System 
Astronomy,  1920-1958,"  Ph.D.  diss.  Princeton  University,  1990,  pp.  33-35,  42-44  and  108-111;  DeVorkin,  pp.  96, 
273,  278  and  293;  Luigi  G.  Jacchia  and  Whipple,  The  Harvard  Photographic  Meteor  Programme,"  Vistas  in 
Astronomy  2  (1956):  982-994;  Whipple,  "Meteors  and  the  Earth's  Upper  Atmosphere,"  Reviews  of  Modern  Physics 
15  (1943):  246-264;  Whipple,  "The  Baker  Super-Schmidt  Meteor  Cameras,"  The  Astronomical  Journal  56  (1951): 
144-145,  states  that  the  first  such  camera  was  installed  in  New  Mexico  in  May  1951.  Determining  the  origin  of 
meteors  was  not  the  primary  interest  of  Harvard  research. 

40.  Whipple,  "Some  Problems  of  Meteor  Astronomy,"  in  H.  C.  Van  de  Hulst,  ed.,  Radio  Astronomy 
(Cambridge:  Cambridge  University  Press,  1957),  p.  376;  Almond,  Davies,  and  Lovell,  "The  Velocity  Distribution 
of  Sporadic  Meteors,"  Monthly  Notices  of  the  Royal  Astronomical  Society  III  (1951):  585-608;  112  (1952):  21-39;  113 
(1953):  411-427.  The  meteor  studies  at  Jodrell  Bank  were  continued  into  later  years.  See,  for  instance,  I.  C. 
Browne  and  T.  R.  Kaiser,  "The  Radio  Echo  from  the  Head  of  Meteor  Trails,"/0urn«/  of  Atmospheric  and  Terrestrial 
Physics  4  (1953):  1-4. 

41.  W.  E.  Knowles  Middleton,  Radar  Development  in  Canada:  The  Radio  Branch  of  the  National  Research 
Council  of  Canada,   1939-1946  (Waterloo,  Ontario:  Wilfred  Laurier  University  Press,  1981),  pp.  18,  25,  27, 
106-109;  Millman  and  McKinley,   "A  Note  on  Four  Complex  Meteor  Radar  Echoes,"  Journal  of  the  Royal 
Astronomical  Society  of  Canada  42  (1948):  122;  McKinley  and  Millman,  "A  Phenomenological  Theory  of  Radar 
Echoes  from  Meteors,"  Proceedings  of  the  Institute  of  Radio  Engineers  37  (1949):  364-375;  McKinley  and  Millman, 
"Determination  of  the  Elements  of  Meteor  Paths  from  Radar  Observations,"  Canadian  Journal  of  Research  A27 
(1949):  53-67;  McKinley,  "Deceleration  and  Ionizing  Efficiency  of  Radar  Meteors,  "Journal  of  Applied  Physics  22 
(1951):  203;  McKinley,  Meteor  Science  and  Engineering  (New  York:  McGraw-Hill,  1961),  p.  20;  Lovell,  Meteor 
Astronomy,  pp.  52-55. 


A  METEORIC  START  17 


McKinley's  group  initiated  their  own  study  of  sporadic  meteors.  By  1951,  with  data  on 
10,933  sporadic  meteors,  McKinley's  group  reached  the  same  conclusion  as  their  British 
colleagues:  meteors  were  part  of  the  solar  system.  Soon,  radar  techniques  became  an  inte- 
gral part  of  Canadian  meteor  research  with  the  establishment  in  1957  of  the  National 
Research  Council  Springhill  Meteor  Observatory  outside  Ottawa.  The  Observatory  con- 
centrated on  scientific  meteor  research  with  radar,  visual,  photographic,  and  spectro- 
scopic  methods.42 

These  meteor  studies  at  Jodrell  Bank  and  the  National  Research  Council,  and  only 
at  those  institutions,  arose  from  the  union  of  radar  and  astronomy;  they  were  the  begin- 
nings of  radar  astronomy.  Radar  studies  of  meteors  were  not  limited  to  Jodrell  Bank  and 
the  National  Research  Council,  however.  With  support  from  the  National  Bureau  of 
Standards,  in  1957  Harvard  College  Observatory  initiated  a  radar  meteor  project  under 
the  direction  of  Fred  Whipple.  Furthermore,  radar  continues  today  as  an  integral  and  vital 
part  of  worldwide  meteor  research.  Its  forte  is  the  ability  to  determine  orbits  better  than 
any  other  technique.  In  the  last  five  years,  a  number  of  recently  built  radars  have  studied 
meteors  in  Britain  (MST  Radar,  Aberytswyth,  Wales),  New  Zealand  (AMOR,  Meteor  Orbit 
Radar,  Christchurch),  and  Japan  (MU  Radar,  Shigaraki),  not  to  mention  earlier  work  in 
Czechoslovakia  and  Sweden.43 

Unlike  the  Jodrell  Bank  and  National  Research  Council  cases,  the  radar  meteor  stud- 
ies started  in  the  United  States  in  the  early  1950s  were  driven  by  civilian  scientists  doing 
ionospheric  and  communications  research  and  by  the  military's  desire  for  jam-proof^ 
point-to-point  secure  communications.  While  various  military  laboratories  undertook 
their  own  research  programs,  most  of  the  civilian  U.S.  radar  meteor  research  was  carried 
out  at  Stanford  University  and  the  National  Bureau  of  Standards,  where  investigators  fruit- 
fully cross-fertilized  ionospheric  and  military  communications  research.  The  Stanford 
case  is  worth  examining  not  only  for  its  later  connections  to  radar  astronomy,  but  also  for 
its  pioneering  radar  study  of  the  Sun  that  arose  out  of  an  interest  in  ionospheric  and  radio 
propagation  research. 

In  contrast  to  the  Stanford  work,  many  radar  meteor  experiments  carried  out  in  the 
United  States  in  the  1940s  were  unique  events.  As  early  as  August  and  November  1944,  for 
instance,  workers  in  the  Federal  Communications  Commission  Engineering  Department 
associated  visual  observations  of  meteors  and  radio  bursts.  In  January  1946,  Oliver  Perry 
Ferrell  of  the  Signal  Corps  reported  using  a  Signal  Corps  SCR-270B  radar  to  detect  mete- 
or ionization  trails.44  The  major  radar  meteor  event  in  the  United  States  and  elsewhere, 


42.  Millman,  McKinley,  and  M.  S.  Burland,  "Combined  Radar,  Photographic,  and  Visual  Observations 
of  the  1947  Perseid  Meteor  Shower,"  Nature  161  (1948):  278-280;  McKinley  and  Millman,  "Determination  of  the 
Elements,"  p.  54;  Millman  and  McKinley,  "A  Note,"  pp.  121-130;  McKinley,  "Meteor  Velocities  Determined  by 
Radio  Observations,"  The  Astrophysics  Journal  US  (1951):  225-267;  F.  R.  Park,  "An  Observatory  for  the  Study  of 
Meteors,"  Engineering Journal 41  (1958):  68-70. 

43.  Whipple,   "Recent  Harvard-Smithsonian  Meteoric  Results,"  Transactions  of  the  IAU  10  (1960): 
345-350;  Jack  W.  Baggaley  and  Andrew  D.  Taylor,  "Radar  Meteor  Orbital  Structure  of  Southern  Hemisphere 
Cometary  Dust  Streams,"  pp.  33-36  in  Alan  W.  Harris  and  Edward  Bowell,  eds.,  Asteroids,  Comets,  Meteors  1991 
(Houston:  Lunar  and  Planetary  Institute,  1992) ;  Baggaley,  Duncan  I.  Steel,  and  Taylor,  "A  Southern  Hemisphere 
Radar  Meteor  Orbit  Survey,"  pp.  37-40  in  ibidem;  William  Jones  and  S.  P.  Kingsley,  "Observations  of  Meteors  by 
MST  Radar,"  pp.  281-284  in  ibidem;  Jun-ichi  Wattanabe,  Tsuko  Nakamura,  T.  Tsuda,  M.  Tsutsumi,  A.  Miyashita, 
and  M.  Yoshikawa,  "Meteor  Mapping  with  MU  Radar,"  pp.  625-627  in  ibidem.  The  MST  Radar  and  the  AMOR 
were  newly  commissioned  in  1990.  The  MU  Radar  is  intended  primarily  for  atmospheric  research. 

For  the  meteor  radar  research  in  Sweden  and  Czechoslovakia,  see  B.  A.  Lindblad  and  M.  Simek, 
"Structure  and  Activity  of  Perseid  Meteor  Stream  from  Radar  Observations,  1956-1978,"  pp.  431-434  in  Claes- 
Ingva  Lagerkvist  and  Hans  Rickman,  eds.,  Asteroids,  Comets,  Meteors  (Uppsala:  Uppsala  University,  1983);  A. 
Hajduk  and  G.  Cevolani,  "Variations  in  Radar  Reflections  from  Meteor  Trains  and  Physical  Properties  of 
Meteoroids,"  pp.  527-530  in  Lagerkvist,  H.  Rickman,  Lindblad,  and  M.  Lindgren,  Asteroids,  Comets,  Meteors  III 
(Uppsala:  Uppsala  University,  1989);  Simek  and  Lindblad,  The  Activity  Curve  of  the  Perseid  Meteor  Stream  as 
Determined  from  Short  Duration  Meteor  Radar  Echoes,"  pp.  567-570  in  ibidem. 

44.  Ferrell,  "Meteoric  Impact  Ionization  Observed  on  Radar  Oscilloscopes,"  Physical  Review  2d  sen,  vol. 
69  (1946):  32-33;  Lovell,  Meteor  Astronomy,  p.  28. 


1 8  TO  SEE  THE  UNSEEN 


however,  was  the  spectacular  meteor  shower  associated  with  the  Giacobini-Zinner  comet. 

On  the  night  of  9  October  1946,  21  Army  radars  were  aimed  toward  the  sky  in  order 
to  observe  any  unusual  phenomena.  The  Signal  Corps  organized  the  experiment,  which 
fit  nicely  with  their  mission  of  developing  missile  detection  and  ranging  capabilities.  The 
equipment  was  operated  by  volunteer  crews  of  the  Army  ground  forces,  the  Army  Air 
Forces,  and  the  Signal  Corps  located  across  the  country  in  Idaho,  New  Mexico,  Texas,  and 
New  Jersey.  For  mainly  meteorological  reasons,  only  the  Signal  Corps  SCR-270  radar  suc- 
cessfully detected  meteor  ionization  trails.  No  attempt  was  made  to  correlate  visual  obser- 
vations and  radar  echoes.  A  Princeton  University  undergraduate,  Francis  B.  Shaffer,  who 
had  received  radar  training  in  the  Navy,  analyzed  photographs  of  the  radar  screen  echoes 
at  the  Signal  Corps  laboratory  in  Belmar,  New  Jersey. 

This  was  the  first  attempt  to  utilize  microwave  radars  to  detect  astronomical  objects. 
The  equipment  operated  at  1,200  MHz  (25  cm),  3,000  MHz  (10  cm),  and  10,000  MHz  (3 
cm) ,  frequencies  in  the  L,  S,  and  X  radar  bands  that  radar  astronomy  later  used.  "On  the 
basis  of  this  night's  experiments,"  the  Signal  Corps  experimenters  decided,  "we  cannot 
conclude  that  microwave  radars  do  not  detect  meteor-formed  ion  clouds."45 

In  contrast  to  the  Signal  Corps  experiment,  radar  meteor  studies  formed  part  of 
ongoing  research  at  the  National  Bureau  of  Standards.  Organized  from  the  Bureau's 
Radio  Section  in  May  1946  and  located  at  Sterling,  Virginia,  the  Central  Radio 
Propagation  Laboratory  (CRPL)  division  had  three  laboratories,  one  of  which  concerned 
itself  exclusively  with  ionospheric  research  and  radio  propagation  and  was  especially  inter- 
ested in  the  impact  of  meteors  on  the  ionosphere.  In  October  1946,  Victor  C.  Pineo  and 
others  associated  with  the  CRPL  used  a  borrowed  SCR-270-D  Signal  Corps  radar  to 
observe  the  Giacobinid  meteor  shower.  Over  the  next  five  years,  Pineo  continued  research 
on  the  effects  of  meteors  on  the  ionosphere,  using  a  standard  ionospheric  research  instru- 
ment called  an  ionosonde  and  publishing  his  results  in  Science. 

Pineo's  interest  was  in  ionospheric  physics,  not  astronomy.  Underwriting  his 
research  at  the  Ionospheric  Research  Section  of  the  National  Bureau  of  Standards  was  the 
Air  Force  Cambridge  Research  Center  (known  later  as  the  Cambridge  Research 
Laboratories  and  today  as  Phillips  Laboratory) .  His  meteor  work  did  not  contribute  to 
knowledge  about  the  origin  of  meteors,  as  such  work  had  in  Britain  and  Canada,  but  it 
supported  efforts  to  create  secure  military  communications  using  meteor  ionization 
trails.46  Also,  it  related  to  similar  research  being  carried  out  concurrently  at  Stanford 
University. 

The  1946  CRPL  experiment,  in  fact,  had  been  suggested  by  Robert  A.  Helliwell  of 
the  Stanford  Radio  Propagation  Laboratory  (SRPL) .  Frederick  E.  Terman,  who  had  head- 
ed the  Harvard  Radio  Research  Laboratory  and  its  radar  counter  measures  research  dur- 
ing the  war,  "virtually  organized  radio  and  electronic  engineering  on  the  West  Coast"  as 


45.  Signal  Corps  Engineering  Laboratories,  "Postwar  Research  and  Development  Program  of  the  Signal 
Corps  Engineering  Laboratories,  1945,"  (Signal  Corps,  1945),  "Postwar  R&D  Program,"  HL  R&D,  HAUSACEC; 
John  Q.  Stewart,  Michael  Ference,  John  J.  Slattery,  Harold  A.  Zahl,  "Radar  Observations  of  the  Draconids,"  Sky 
and  Telescope  6  (March  1947) :  35.  They  reported  their  earlier  results  in  a  paper,  "Radar  Observations  of  the 
Giacobinid  Meteors,"  read  before  the  December  1946  meeting  of  the  American  Astronomical  Society  in  Boston. 
HL  Diana  46  (26),  HAUSACEC. 

46.  Wilbert  F.  Snyder  and  Charles  L.  Bragaw,  Achievement  in  Radio:  Seventy  Yean  of  Radio  Science, 
Technology,  Standards,  and  Measurement  at  the  National  Bureau  of  Standards  (Boulder:  National  Bureau  of  Standards, 
1986),  pp.  461-465;  Ross  Bateman,  A.  G.  McNish,  and  Pineo,  "Radar  Observations  during  Meteor  Showers,  9 
October  1946,"  Science  104  (1946):  434-435;  Pineo,  "Relation  of  Sporadic  E  Reflection  and  Meteoric  Ionization," 
Science  110   (1949):  280-283;  Pineo,   "A  Comparison  of  Meteor  Activity  with  Occurrence  of  Sporadic-E 
Reflections,"  Science  112  (1950):  5051;  Pineo  and  T.  H.  Gautier,  "The  Wave-Frequency  Dependence  of  the 
Duration  of  Radar-Type  Echoes  from  Meteor  Trails,"  Science  114  (1951):  460-462.  Other  articles  by  Pineo  on  his 
ionospheric  research  can  be  found  in  Laurence  A.  Manning,  Bibliography  of  the  Ionosphere:  An  Annotated  Survey 
through  I960  (Stanford:  Stanford  University  Press,  1962),  pp.  421-423. 


A  METEORIC  START  19 


Stanford  Dean  of  Engineering,  according  to  historian  C.  Stewart  Gillmor.  Terman  nego- 
tiated a  contract  with  the  three  military  services  for  the  funding  of  a  broad  range  of 
research,  including  the  SRPL's  long-standing  ionospheric  research  program.47 

Helliwell,  whose  career  was  built  on  ionospheric  research,  was  joined  at  the  SRPL  by 
Oswald  G.  Villard,  Jr.  Villard  had  earned  his  engineering  degree  during  the  war  for  the 
design  of  an  ionosphere  sounder.  As  an  amateur  radio  operator  in  Cambridge, 
Massachusetts,  he  had  noted  the  interference  caused  by  meteor  ionizations  at  shortwave 
frequencies  called  Doppler  whistles.48 

In  October  1946,  during  the  Giacobinid  meteor  shower,  Helliwell,  Villard,  Laurence 
A.  Manning,  and  W.  E.  Evans,  Jr.,  detected  meteor  ion  trails  by  listening  for  Doppler  whis- 
tles with  radios  operating  at  15  MHz  (20  meters)  and  29  MHz  (10  meters).  Manning  then 
developed  a  method  of  measuring  meteor  velocities  using  the  Doppler  frequency  shift  of 
a  continuous-wave  signal  reflected  from  the  ionization  trail.  Manning,  Villard,  and  Allen 
M.  Peterson  then  applied  Manning's  technique  to  a  continuous-wave  radio  study  of  the 
Perseid  meteor  shower  in  August  1948.  The  initial  Stanford  technique  was  significantly 
different  from  that  developed  at  Jodrell  Bank;  it  relied  on  continuous-wave  radio,  rather 
than  pulsed  radar,  echoes.49 

One  of  those  conducting  meteor  studies  at  Stanford  was  Von  R.  Eshleman,  a  gradu- 
ate student  in  electrical  engineering  who  worked  under  both  Manning  and  Villard.  While 
serving  in  the  Navy  during  World  War  II,  Eshleman  had  studied,  then  taught,  radar  at  the 
Navy's  radar  electronics  school  in  Washington,  DC.  In  1946,  while  returning  from  the  war 
on  the  U.S.S.  Missouri,  Eshleman  unsuccessfully  attempted  to  bounce  radar  waves  off  the 
Moon  using  the  ship's  radar.  Support  for  his  graduate  research  at  Stanford  came  through 
contracts  between  the  University  and  both  the  Office  of  Naval  Research  and  the  Air  Force. 

Eshleman 's  dissertation  considered  the  theory  of  detecting  meteor  ionization  trails 
and  its  application  in  actual  experiments.  Unlike  the  British  and  Canadian  meteor  stud- 
ies, the  primary  research  interest  of  Eshleman,  Manning,  Villard,  and  the  other  Stanford 
investigators  was  information  about  the  winds  and  turbulence  in  the  upper  atmosphere. 
Their  investigations  of  meteor  velocities,  the  length  of  ionized  meteor  trails,  and  the  fad- 
ing and  polarization  of  meteor  echoes  were  part  of  that  larger  research  interest,  while 
Eshleman 's  dissertation  was  an  integral  part  of  the  meteor  research  program. 

Eshleman  also  considered  the  use  of  meteor  ionization  trails  for  secure  military  com- 
munications. His  dissertation  did  not  explicitly  state  that  application,  which  he  took  up 
after  completing  the  thesis.  The  Air  Force  supported  the  Stanford  meteor  research  main- 
ly to  use  meteor  ionization  trails  for  secure,  point-to-point  communications.  The  Stanford 
meteor  research  thus  served  a  variety  of  scientific  and  military  purposes  simultaneously.50 


47.  Gillmor,  "Federal  Funding  and  Knowledge  Growth  in  Ionospheric  Physics,  1945-1981,"  Social  Studies 
of  Science  16  (1986):  124. 

48.  Oswald  G.  Villard,  Jr.,  "Listening  in  on  the  Stars,"  QST  30  (January,  1946):  59-60,  120  and  122; 
Helliwell,  Whistlers  and  Related  Ionospheric  Phenomena  (Stanford:  Stanford  University  Press,  1965),  pp.  11-23; 
Leslie,  p.  58;  Gillmor,  "Federal  Funding,"  p.  129. 

49.  Manning,  Helliwell,  Villard,  and  Evans,  "On  the  Detection  of  Meteors  by  Radio,"  Physical  Review  70 
( 1946) :  767-768;  Manning,  "The  Theory  of  the  Radio  Detection  of  Meteors,"7ourna/  of  Applied  Physics  19  ( 1948) : 
689-699:  Manning,  Villard,  and  Peterson,  "Radio  Doppler  Investigation  of  Meteoric  Heights  and  Velocities," 
Journal  of  Applied  Physics  20  ( 1949) :  475-479;  Von  R.  Eshleman,  "The  Effect  of  Radar  Wavelength  on  Meteor  Echo 
Rate,"  Transactions  of  the  Institute  of  Radio  Engineers  1  (1953):  37-42.  DeVorkin,  pp.  287-288,  points  out  that,  when 
given  an  opportunity  to  make  radio  observations  in  coordination  with  rocket  flights,  Stanford  declined. 

50.  Eshleman  9  May  1994;  Eshleman,  The  Mechanism  of  Radio  Reflections  from  Meteoric  Ionization," 
Ph.D.  diss.,  Stanford  University,  1952;  Eshleman,  The  Mechanism  of  Radio  Reflections  from  Meteoric  Ionization, 
Technical  Report  no.  49  (Stanford:  Stanford  Electronics  Research  Laboratory,  15  July  1952),  pp.  ii-iii  and  3; 
Manning,  "Meteoric  Radio  Echoes,"  Transactions  of  the  Institute  of  Radio  Engineers  2  (1954):  82-90;  Manning  and 
Eshleman,  "Meteors  in  the  Ionosphere,"  Proceedings  of  the  Institute  of  Radio  Engineers  47  (1959):  186-199. 


20  TO  SEE  THE  UNSEEN 


The  meteor  research  carried  out  at  Stanford  had  nontrivial  consequences. 
Eshleman's  dissertation  has  continued  to  provide  the  theoretical  foundation  of  modern 
meteor  burst  communications,  a  communication  mode  that  promises  to  function  even 
after  a  nuclear  holocaust  has  rendered  useless  all  normal  wireless  communications.  The 
pioneering  work  at  Stanford,  the  National  Bureau  of  Standards,  and  the  Air  Force 
Cambridge  Research  Laboratories  received  new  attention  in  the  1980s,  when  the  Space 
Defense  Initiative  ("Star  Wars")  revitalized  interest  in  using  meteor  ionization  trails  for 
classified  communications.  Non-military  applications  of  meteor  burst  communications 
also  have  arisen  in  recent  years.51 

Early  meteor  burst  communications  research  was  not  limited  to  Stanford  and  the 
National  Bureau  of  Standards.  American  military  funding  of  early  meteor  burst  commu- 
nications research  extended  beyond  its  shores  to  Britain.  Historians  of  Jodrell  Bank  radio 
astronomy  and  meteor  radar  research  stated  that  radio  astronomy  had  surpassed  meteor 
studies  at  the  observatory  by  1955.  However,  that  meteor  work  persisted  until  1964 
through  a  contract  with  the  U.S.  Air  Force,  though  as  a  cover  for  classified  military 
research.52 

Auroras  provided  additional  radar  targets  in  the  1950s.  A  major  initiator  of  radar 
auroral  studies  was  Jodrell  Bank.  As  early  as  August  1947,  while  conducting  meteor 
research,  the  Jodrell  Bank  scientists  Lovell,  Clegg,  and  Ellyett  received  echoes  from  an 
aurora  display.  Arnold  Aspinall  and  G.  S.  Hawkins  then  continued  the  radar  auroral  stud- 
ies at  Jodrell  Bank  in  collaboration  with  W.  B.  Housman,  Director  of  the  Aurora  Section 
of  the  British  Astronomy  Association,  and  the  aurora  observers  of  that  Section.  In  Canada, 
McKinley  and  Millman  also  observed  an  aurora  during  their  meteor  research  in  April 
1948.S3 

The  problem  with  bouncing  radar  waves  off  an  aurora  was  determining  the  reflect- 
ing point.  Researchers  in  the  University  of  Saskatchewan  Physics  Department  (B.  W. 
Currie,  P.  A.  Forsyth,  and  F.  E.  Vawter)  initiated  a  systematic  study  of  auroral  radar  reflec- 
tions in  1948,  with  funding  from  the  Defense  Research  Board  of  Canada.  Radar  equip- 
ment was  lent  by  the  U.S.  Air  Force  Cambridge  Research  Center  and  modified  by  the 
Radio  and  Electrical  Engineering  Division  of  the  National  Research  Council.  Forsyth  had 
completed  a  dissertation  on  auroras  at  McGill  University  and  was  an  employee  of  the 
Defense  Research  Board's  Telecommunications  Establishment  on  loan  to  die  University 
of  Saskatchewan  for  the  project.  The  Saskatchewan  researchers  discovered  that  the  echoes 
bounced  off  small,  intensely  ionized  regions  in  the  aurora.54 

Other  aurora  researchers,  especially  in  Sweden  and  Norway,  took  up  radar  studies. 
In  Sweden,  Gotha  Hellgren  and  Johan  Meos  of  the  Chalmers  University  of  Technology 


51.  Robert  Desourdis,  telephone  conversation,  22  September  1994;  Donald  Spector,  telephone  conver- 
sation, 22  September  1994;  Donald  L.  Schilling,  ed.,  Meteor  Burst  Communications:  Theory  and  Practice  (New  York: 
Wiley,  1993);  Jacob  Z.  Schanker,  Meteor  Bunt  Communications  (Boston:  Artech  House,  1990).  For  a  civilian  use  of 
meteor  burst  communications,  see  Henry  S.  Santeford,  Meteor  Burst  Communication  System:  Alaska  Winter  Field  Test 
Program  (Silver  Spring,  MD:  U.S.  Dept.  of  Commerce,  National  Oceanic  and  Atmospheric  Administration, 
National  Weather  Service,  Office  of  Hydrology,  1976). 

52.  Lovell  11  January  1994;  7  and  8/55,  "Accounts, "JBA;  Lovell,  "Astronomer  by  Chance,"  typed  man- 
uscript, February  1988,  p.  376,  Lovell  materials;  Lovell,  Jodrell  Bank,  p.  157;  G.  Nigel  Gilbert,  "The  Development 
of  Science  and  Scientific  Knowledge:  The  Case  of  Radar  Meteor  Research,"  in  Gerard  Lemaine,  Roy  Macleod, 
Michael  Mulkay,  and  Peter  Weingart,  eds.,  Perspectives  on  the  Emergence  of  Scientific  Disciplines  (Chicago:  Aldine, 
1976),  p.  191;  Edge  and  Mulkay,  pp.  330-331. 

53.  Lovell,  Clegg,  and  Ellyett,  "Radio  Echoes  from  the  Aurora  Borealis,"  Nature  160  ( 1947) :  372;  Aspinall 
and  Hawkins,  "Radio  Echo  Reflections  from  the  Aurora  Eorealia,"  Journal  of  the  British  Astronomical  Association  60 
(1950):  130-135;  various  materials  in  File  Group  "International  Geophysical  Year,"  Box  1,  File  4,  JBA;  McKinley 
and  Millman,  "Long  Duration  Echoes  from  Aurora,  Meteors,  and  Ionospheric  Back-Scatter,"  Canadian  Journal  of 
PhysicsBl  (1953):  171-181. 

54.  Currie,  Forsyth,  and  Vawter,  "Radio  Reflections  from  Aurora,"  Journal  of  Geophysical  Research  58 
(1953):  179-200. 


A  METEORIC  START  21 


Research  Laboratory  of  Electronics  in  Gothenburg  decided  to  conduct  radar  studies  of 
auroras  as  part  of  their  ionospheric  research  program.  Beginning  in  May  1951,  the  Radio 
Wave  Propagation  Laboratory  of  the  Kiruna  Geophysical  Observatory  undertook  round- 
the-clock  observations  of  auroras  with  a  30.3-MHz  (10-meter)  radar.  In  Norway,  Leiv 
Harang,  who  had  observed  radar  echoes  from  an  aurora  as  early  as  1940,  and  B. 
Landmark  observed  auroras  with  radars  lent  by  the  Norwegian  Defense  Research 
Establishment  and  installed  at  Oslo  (Kjeller)  and  Tromso,  where  a  permanent  center  for 
radar  investigation  of  auroras  was  created  later.55 

These  and  subsequent  radar  investigations  changed  the  way  scientists  studied  auro- 
ras, which  had  been  almost  entirely  by  visual  means  up  to  about  1950.  Permanent  auroral 
observatories  located  at  high  latitudes,  such  as  those  at  Oslo  and  Tromso  in  Norway,  at 
Kiruna  in  Sweden,  and  at  Saskatoon  in  Saskatchewan,  integrated  radar  into  a  spectrum  of 
research  instruments  that  included  spectroscopy,  photography,  balloons,  and  sounding 
rockets.  The  International  Geophysical  Year,  1957-1958,  was  appropriately  timed  to  fur- 
ther radar  auroral  research;  it  coincided  with  extremely  high  sunspot  and  auroral  activity, 
such  as  the  displays  visible  from  Mexico  in  September  1957  and  the  "Great  Red  Aurora" 
of  10  February  1958.  Among  those  participating  in  the  radar  aurora  and  meteor  studies 
associated  with  the  International  Geophysical  Year  activities  were  three  Jodrell  Bank  stu- 
dents and  staff  who  joined  the  Royal  Society  expedition  to  Halley  Bay,  Antarctica.56 


To  the  Moon  Again 


The  auroral  and  meteor  radar  studies  carried  out  in  the  wake  of  the  lunar  radar 
experiments  of  DeWitt  and  Bay  were,  in  essence,  ionospheric  studies.  While  the  causes  of 
auroras  and  meteor  ionization  trails  arise  outside  the  Earth's  atmosphere,  the  phenome- 
na themselves  are  essentially  ionospheric.  At  Jodrell  Bank,  meteor  and  auroral  studies  pro- 
vided the  initial  impetus,  but  certainly  not  the  sustaining  force,  for  the  creation  of  an 
ongoing  radar  astronomy  program.  That  sustaining  force  came  from  lunar  studies. 
However,  like  so  much  of  early  radar  astronomy,  those  lunar  studies  were  never  far  from 
ionospheric  research.  Indeed,  the  trailblazing  efforts  of  DeWitt  and  Bay  opened  up  new 
vistas  of  ionospheric  and  communications  research  using  radar  echoes  from  the  Moon. 

Historically,  scientists  had  been  limited  to  the  underside  and  lower  portion  of  the 
ionosphere.  The  discovery  of  "cosmic  noise"  by  Bell  Telephone  researcher  Karl  Jansky  in 
1932  suggested  that  higher  frequencies  could  penetrate  the  ionosphere.  The  experiments 
of  DeWitt  and  Bay  suggested  radar  as  a  means  of  penetrating  the  lower  regions  of  the 
ionosphere.  DeWitt,  moreover,  had  observed  unexpected  fluctuations  in  signal  strength 
that  lasted  several  minutes,  which  he  attributed  to  anomalous  ionospheric  refraction.57 
His  observations  invited  further  investigation  of  the  question. 

The  search  for  a  better  explanation  of  those  fluctuations  was  taken  up  by  a  group  of 
ionosphericists  in  the  Division  of  Radiophysics  of  the  Australian  Council  for  Scientific  and 
Industrial  Research:  Frank  J.  Kerr,  C.  Alex  Shain,  and  Charles  S.  Higgins.  In  1946,  Kerr 
and  Shain  explored  the  possibility  of  obtaining  radar  echoes  from  meteors,  following  the 


55.  Hellgren  and  Meos,  "Localization  of  Aurorae  with  10m  High  Power  Radar  Technique,  using  a 
Rotating  Antenna,"  Tellus  3  (1952):  249-261;  Harang  and  Landmark,  "Radio  Echoes  Observed  during  Aurorae 
and  Geomagnetic  Storms  using  35  and  74  Mc/s  Waves  Simultaneously,"  Journal  of  Atmospheric  and  Terrestrial 
Physics  4  (1954):  322-338;  ibidem  Nature  171  (1953):  1017-1018;  Harang  and  J.  Troim,  "Studies  of  Auroral 
Echoes,"  Planetary  and  Space  Science*)  (1961):  33-45  and  105-108. 

56.  Jean  Van  Bladel,  Les  applications  du  radar  «  I'astronomie  et  a  la  meteorologie  (Paris:  Gauthier-VHlars, 
1955),  pp.  78-80;  Neil  Bone,  The  Aurora:  Sun-Earth  Interactions  (New  York:  Ellis  Horwood,  1991),  pp.  36,  45-49; 
Alistair  Vallance  Jones,  Aurora  (Boston:  D.  Reidel  Publishing  Company,  1974),  pp.  9,  11  and  27;  Lovell, 
"Astronomer  by  Chance,"  manuscript,  February  1988,  p.  201,  Lovell  materials. 

57.  DeWitt  and  Stodola,  p.  239. 


22  TO  SEE  THE  UNSEEN 


example  of  Lovell  in  Britain,  but  Project  Diana  turned  their  attention  toward  the  Moon. 
In  order  to  study  the  fluctuations  in  signal  strength  that  DeWitt  had  observed,  Kerr,  Shain, 
and  Higgins  put  together  a  rather  singular  experiment. 

For  a  transmitter,  they  used  the  20-MHz  (15-meter)  Radio  Australia  station,  located 
in  Shepparton,  Victoria,  when  it  was  not  in  use  for  regular  programming  to  the  United 
States  and  Canada.  The  receiver  was  located  at  the  Radiophysics  Laboratory,  Hornsby, 
New  South  Wales,  a  distance  of  600  km  from  the  transmitter.  Use  of  this  unique  system  was 
limited  to  days  when  three  conditions  could  be  met  all  at  the  same  time:  the  Moon  was 
passing  through  the  station's  antenna  beams;  the  transmitter  was  available;  and  atmos- 
pheric conditions  were  favorable.  In  short,  the  system  was  workable  about  twenty  days  a 
year.58 

Kerr,  Shain,  and  Higgins  obtained  lunar  echoes  on  thirteen  out  of  fifteen  attempts. 
The  amplitude  of  the  echoes  fluctuated  considerably  over  the  entire  run  of  tests  as  well  as 
within  a  single  test.  Researchers  at  ITT's  Federal  Telecommunications  Laboratories  in 
New  York  City  accounted  for  the  fluctuations  observed  by  DeWitt  by  positing  the  existence 
of  smooth  spots  that  served  as  "bounce  points"  for  the  reflected  energy.  Another  possibil- 
ity they  imagined  was  the  existence  of  an  ionosphere  around  the  Moon.59  The  Australians 
disagreed  with  the  explanations  offered  by  DeWitt  and  the  ITT  researchers,  but  they  were 
initially  cautious:  "It  cannot  yet  be  said  whether  the  reductions  in  intensity  and  the  long- 
period  variations  are  due  to  ionospheric,  lunar  or  inter-planetary  causes."60 

During  a  visit  to  the  United  States  in  1948,  J.  L.  Pawsey,  a  radio  astronomy  enthusiast 
also  with  the  Council  for  Scientific  and  Industrial  Research's  Division  of  Radiophysics, 
arranged  a  cooperative  experiment  with  the  Americans.  A  number  of  U.S.  organizations 
with  an  interest  in  radio,  the  National  Bureau  of  Standards  CRPL,  the  Radio  Corporation 
of  America  (Riverhead,  New  York),  and  the  University  of  Illinois  (Urbana),  attempted  to 
receive  Moon  echoes  simultaneously  from  Australia,  beginning  30  July  1948.  Ross 
Bateman  (CRPL)  acted  as  American  coordinator.  The  experiment  was  not  a  great  success. 
The  times  of  the  tests  (limited  by  transmitter  availability)  were  all  in  the  middle  of  the  day 
at  the  receiving  points.  Echoes  were  received  in  America  on  two  occasions,  1  August  and 
28  October,  and  only  for  short  periods  in  each  case. 

Meanwhile,  Kerr  and  Shain  continued  to  study  lunar  echo  fading  with  the  Radio 
Australia  transmitter.  Based  on  thirty  experiments  (with  echoes  received  in  twenty-four  of 
them)  conducted  over  a  year,  they  now  distinguished  rapid  and  slow  fading.  Kerr  and 
Shain  proposed  that  each  type  of  fading  had  a  different  cause.  Rapid  fading  resulted  from 
the  Moon's  libration,  a  slow  wobbling  motion  of  the  Moon.  Irregular  movement  in  the 
ionosphere,  they  originally  suggested,  caused  the  slower  fading.61  Everyone  agreed  that 
the  rapid  fading  of  lunar  radar  echoes  originated  in  the  lunar  libration,  but  the  cause  of 
slow  fading  was  not  so  obvious. 

The  problem  of  slow  fading  was  taken  up  at  Jodrell  Bank  by  William  A.  S.  Murray  and 
J.  K.  Hargreaves,  who  sought  an  explanation  in  the  ionosphere.  Although  Lovell  had  pro- 
posed undertaking  lunar  radar  observations  as  early  as  1946,  the  first  worthwhile  results 
were  not  obtained  until  the  fall  of  1953.  Hargreaves  and  Murray  photographed  and  ana- 
lyzed some  50,000  lunar  radar  echoes  at  the  Jodrell  Bank  radar  telescope  in  October  and 
November  1953  to  determine  the  origin  of  slow  fading. 


58.  Kerr,  Shain,  and  Higgins,  "Moon  Echoes  and  Penetration  of  the  Ionosphere,"  Nature  163  (1949): 
310;  Kerr  and  Shain,  "Moon  Echoes  and  Transmission  through  the  Ionosphere,"  ftoceedings  oftheIRE39  (1951): 
230;  Kerr,  "Early  Days  in  Radio  and  Radar  Astronomy  in  Australia,"  pp.  136-137  in  Sullivan.  Kerr  and  Shain,  pp. 
230-232,  contains  a  better  description  of  the  system.  See  also  Kerr,  "Radio  Superrefraction  in  the  Coastal 
Regions  of  Australia,"  Australian  Journal  of  Scientific  Research,  sen  A,  vol.  1  (1948):  443-463. 

59.  D.  D.  Grieg,  S.  Metzger,  and  R.  Waer,  "Considerations  of  Moon-Relay  Communication,"  Proceedings 
of  the  IRE  36  (1 948):  660. 

60.  Kerr,  Shain,  and  Higgins,  p.  311. 

61.  Kerr  and  Shain,  pp.  230-242. 


A  METEORIC  START  23 


With  rare  exceptions,  nighttime  runs  showed  a  steady  signal  amplitude,  while  day- 
time runs,  especially  those  within  a  few  hours  of  sunrise,  were  marked  by  severe  fading. 
The  high  correlation  between  fading  and  solar  activity  strongly  suggested  an  ionospheric 
origin.  However,  Hargreaves  and  Murray  believed  that  irregularities  in  the  ionosphere 
could  not  account  for  slow  fading  over  periods  lasting  up  to  an  hour.  They  suggested 
instead  that  slow  fading  resulted  from  Faraday  rotation,  in  which  the  plane  of  polarization 
of  the  radio  waves  rotated,  as  they  passed  through  the  ionosphere  in  the  presence  of  the 
Earth's  magnetic  field. 

Hargreaves  and  Murray  carried  out  a  series  of  experiments  to  test  their  hypothesis  in 
March  1954.  The  transmitter  had  a  horizontally  polarized  antenna,  while  the  primary  feed 
of  the  receiving  antenna  consisted  of  two  dipoles  mounted  at  right  angles.  They  switched 
the  receiver  at  short  intervals  between  the  vertical  and  horizontal  feeds  so  that  echoes 
would  be  received  in  both  planes  of  polarization,  a  technique  that  is  a  standard  planetary 
radar  practice  today. 

As  the  plane  of  polarization  of  the  radar  waves  rotated  in  the  ionosphere,  stronger 
echo  amplitudes  were  received  by  the  vertical  feed  than  by  the  horizontal  feed.  If  no 
Faraday  rotation  had  taken  place,  both  the  transmitted  and  received  planes  of  polariza- 
tion would  be  the  same,  that  is,  horizontal.  But  Faraday  rotation  of  the  plane  of  polariza- 
tion in  the  ionosphere  had  rotated  the  plane  of  polarization  so  that  the  vertical  feed 
received  more  echo  power  than  the  horizontal  feed.  The  results  confirmed  that  slow 
fading  was  caused,  at  least  in  part,  by  a  change  in  the  plane  of  polarization  of  the  received 
lunar  echo.62 

Murray  and  Hargreaves  soon  took  positions  elsewhere,  yet  Jodrell  Bank  continued  to 
feature  radar  astronomy  through  the  persistence  of  Bernard  Lovell.  Lovell  became  entan- 
gled in  administrative  affairs  and  the  construction  of  a  giant  radio  telescope,  while  John 
V.  Evans,  a  research  student  of  Lovell,  took  over  the  radar  astronomy  program.  Evans  had 
a  B.Sc.  in  physics  and  had  had  an  interest  in  electronics  engineering  since  childhood.  He 
chose  the  University  of  Manchester  Physics  Department  for  his  doctoral  degree,  because 
the  department,  through  Lovell,  oversaw  the  Jodrell  Bank  facility.  The  facility's  heavy 
involvement  in  radio  and  radar  astronomy,  when  Evans  arrived  there  on  his  bicycle  in  the 
summer  of  1954,  assured  Evans  that  his  interest  in  electronics  engineering  would  be  sated. 

With  the  approval  and  full  support  of  Lovell,  Evans  renewed  the  studies  of  lunar 
radar  echoes,  but  first  he  rebuilt  the  lunar  radar  equipment.  It  was  a  "poor  instrument," 
Evans  later  recalled,  "and  barely  got  echoes  from  the  Moon."  After  he  increased  the  power 
output  from  1  to  10  kilowatts  and  improved  the  sensitivity  of  the  receiver  by  rebuilding  the 
front  end,  Evans  took  the  lunar  studies  in  a  new  direction.  Unlike  the  majority  of  Jodrell 
Bank  research,  Evans's  lunar  work  was  underwritten  through  a  contract  with  the  U.S.  Air 
Force,  which  was  interested  in  using  the  Moon  as  part  of  a  long-distance  communications 
system. 

With  his  improved  radar  apparatus,  Evans  discovered  that  the  Moon  overall  was  a  rel- 
atively smooth  reflector  of  radar  waves  at  the  wavelength  he  used  (120  MHz;  2.5  meters). 
Later,  from  the  way  that  the  Moon  appeared  to  scatter  back  radar  waves,  Evans  speculat- 
ed that  the  lunar  surface  was  covered  with  small,  round  objects  such  as  rocks  and  stones. 
Hargreaves  proposed  that  radar  observations  at  shorter  wavelengths  should  be  able  to  give 
interesting  statistical  information  about  the  features  of  the  lunar  surface.63  That  idea  was 


62.  Murray  and  Hargreaves,  "Lunar  Radio  Echoes  and  the  Faraday  Effect  in  the  Ionosphere,"  Nature  173 
(1954):  944-945;  Browne,  Evans,  Hargreaves,  and  Murray,  p.  901;  1/17  "Correspondence  Series  7,"JBA;  Lovell, 
"Astronomer  by  Chance,"  p.  183. 

63.  Evans  9  September  1993;  Hargreaves,  "Radio  Observations  of  the  Lunar  Surface,"  Proceedings  of  the 
Physical  Society  73  (1959):  536-537;  Evans,  "Research  on  Moon  Echo  Phenomena,"  Technical  (Final)  Report,  1 
May  1956,  and  earlier  reports  in  1/4  "Correspondence  Series  2,"JBA. 


24  TO  SEE  THE  UNSEEN 


the  starting  point  for  the  creation  of  planetary  radar  techniques  that  would  reveal  the  sur- 
face characteristics  of  planets  and  other  moons. 

Experimenters  prior  to  Evans  had  assumed  that  the  Moon  reflected  radar  waves  from 
the  whole  of  its  illuminated  surface,  like  light  waves.  They  debated  whether  the  power 
returned  to  the  Earth  was  reflected  from  the  entire  visible  disk  or  from  a  smaller  region. 
The  question  was  important  to  radar  astronomers  at  Jodrell  Bank  as  well  as  to  military  and 
civilian  researchers  developing  Moon-relay  communications. 

In  March  1957,  Evans  obtained  a  series  of  lunar  radar  echoes.  He  photographed 
both  the  transmitted  pulses  and  their  echoes  so  that  he  could  make  a  direct  comparison 
between  the  two.  Evans  also  made  range  measurements  of  the  echoes  at  the  same  time.  In 
each  case,  the  range  of  the  observed  echo  was  consistent  with  that  of  the  front  edge  of  the 
Moon.  The  echoes  came  not  from  the  entire  visible  disk  but  from  a  smaller  portion  of  the 
lunar  surface,  that  closest  to  the  Earth  and  known  as  the  subradar  point.64  This  discovery 
became  fundamental  to  radar  astronomy  research. 

Because  radar  waves  reflected  off  only  the  foremost  edge  of  the  Moon,  Evans  and 
John  H.  Thomson  (a  radio  astronomer  who  had  transferred  from  Cambridge  in  1959) 
undertook  a  series  of  experiments  on  the  use  of  the  Moon  as  a  passive  communication 
relay.  Although  initial  results  were  "not  intelligible,"  because  FM  and  AM  broadcasts  tend- 
ed to  fade,  Lovell  bounced  Evans'  "hello"  off  the  Moon  with  a  Jodrell  Bank  transmitter 
and  receiver  during  his  BBC  Reith  Lecture  of  1958.  Several  years  later,  in  collaboration 
with  the  Pye  firm,  a  leading  British  manufacturer  of  electronic  equipment  headquartered 
in  Cambridge,  and  with  underwriting  from  the  U.S.  Air  Force,  a  Pye  transmitter  at  Jodrell 
Bank  was  used  to  send  speech  and  music  via  the  Moon  to  the  Sagamore  Hill  Radio 
Astronomy  Observatory  of  the  Air  Force  Cambridge  Research  Center,  at  Hamilton, 
Massachusetts.  The  U.S.  Air  Force  thus  obtained  a  successful  lunar  bounce  communica- 
tion experiment  at  Jodrell  Bank  for  a  far  smaller  sum  than  that  spent  by  the  Naval 
Research  Laboratory.65 

The  Moon  Bounce 

The  lunar  communication  studies  at  Jodrell  Bank  illustrate  that  astronomy  was  not 
behind  all  radar  studies  of  the  Moon.  Much  of  the  lunar  radar  work,  especially  in  the 
United  States,  was  performed  to  test  long-distance  communication  systems  in  which  the 
Moon  would  serve  as  a  relay.  Thus,  the  experiments  of  DeWitt  and  Bay  may  be  said  to  have 
begun  the  era  of  satellite  communications.  Research  on  Moon-relay  communications  sys- 
tems by  both  military  and  civilian  laboratories  eventually  drew  those  institutions  into  the 
early  organizational  activities  of  radar  astronomers.  After  all,  both  communication 
research  and  radar  astronomy  shared  an  interest  in  the  behavior  of  radio  waves  at  the 
lunar  surface.  Hence,  a  brief  look  at  that  research  would  be  informative. 

Before  the  advent  of  satellites,  wireless  communication  over  long  distances  was 
achieved  by  reflecting  radio  waves  off  the  ionosphere.  As  transmission  frequency 
increased,  the  ionosphere  was  penetrated.  Long-distance  wireless  communication  at  high 
frequencies  had  to  depend  on  a  network  of  relays,  which  were  expensive  and  technically 
complex.  Using  the  Moon  as  a  relay  appeared  to  be  a  low-cost  alternative.66 


64.  Evans  9  September  1993;  Evans,  The  Scattering  of  Radio  Waves  by  the  Moon,"  Proceedings  of  the 
Physical  Society  B70  (1957):  1105-1112. 

65.  Evans  9  September  1993;  Edge  and  Mulkay,  p.  298;  Materials  in  1/4  "Correspondence  Series  2,"  and 
2/53  "Accounts,  "JBA.  With  NASA  funding,  Jodrell  Bank  later  participated  in  the  Echo  balloon  project. 

66.  Harold  Sobol,   "Microwave   Communications:  An   Historical   Perspective,"  IEEE  Transactions  on 
Microwave  Theory  and  Techniques  MTT-32  (1984):  1170-1181. 


A  METEORIC  START  25 


Reacting  to  the  successes  of  DeWitt  and  Bay,  researchers  at  the  ITT  Federal 
Telecommunications  Laboratories,  Inc.,  New  York  City,  planned  a  lunar  relay  telecom- 
munication system  operating  at  UHF  frequencies  (around  50  MHz;  6  meters)  to  provide 
radio  telephone  communications  between  New  York  and  Paris.  If  such  a  system  could  be 
made  to  work,  it  would  provide  ITT  with  a  means  to  compete  with  transatlantic  cable  car- 
riers dominated  by  rival  AT&T.  What  the  Federal  Telecommunications  Laboratories  had 
imagined,  the  Collins  Radio  Company,  Cedar  Rapids,  Iowa,  and  the  National  Bureau  of 
Standards  CRPL,  accomplished. 

On  28  October  and  8  November  1951,  Peter  G.  Sulzer  and  G.  Franklin  Montgomery, 
CRPL,  and  Irvin  H.  Gerks,  Collins  Radio,  sent  a  continuous-wave  418-MHz  (72-cm)  radio 
signal  from  Cedar  Rapids  to  Sterling,  Virginia,  via  the  Moon.  On  8  November,  a  slowly 
hand-keyed  telegraph  message  was  sent  over  the  circuit  several  times.  The  message  was  the 
same  sent  by  Samuel  Morse  over  the  first  U.S.  public  telegraph  line:  "What  hath  God 
wrought?"67 

Unbeknownst  to  the  CRPL/Collins  team,  the  first  use  of  the  Moon  as  a  relay  in  a 
communication  circuit  was  achieved  only  a  few  days  earlier  by  military  researchers  at  the 
Naval  Research  Laboratory  (NRL) .  The  Navy  was  interested  in  satellite  communications, 
and  the  Moon  offered  itself  as  a  free  (if  distant  and  rough)  satellite  in  the  years  before  an 
artificial  satellite  could  be  launched.  In  order  to  undertake  lunar  communication  studies, 
the  NRL  built  what  was  then  the  world's  largest  parabolic  antenna  in  the  summer  of  1951. 
The  dish  covered  over  an  entire  acre  (67  by  80  meters;  220  by  263  ft)  and  had  been  cut 
into  the  earth  by  road-building  machinery  at  Stump  Neck,  Maryland.  The  one-megawatt 
transmitter  operated  at  198  MHz  (1.5  meters).  The  NRL  first  used  the  Moon  as  a  relay  in 
a  radio  communication  circuit  on  21  October  1951.  After  sending  the  first  voice  trans- 
mission via  the  Moon  on  24  July  1954,  the  NRL  demonstrated  transcontinental  satellite 
teleprinter  communication  from  Washington,  DC,  to  San  Diego,  CA,  at  301  MHz  (1 
meter)  on  29  November  1955  and  transoceanic  satellite  communication,  from 
Washington,  DC,  to  Wahiawa,  Oahu,  Hawaii,  on  23  January  1956.68 

Later  in  1956,  the  NRL's  Radio  Astronomy  Branch  started  a  radar  program  under 
Benjamin  S.  Yaplee  to  determine  the  feasibility  of  bouncing  microwaves  off  the  Moon  and 
to  accurately  measure  both  the  Moon's  radius  and  the  distances  to  different  reflecting 
areas  during  the  lunar  libration  cycle.  Aside  from  the  scientific  value  of  that  research,  the 
information  would  help  the  Navy  to  determine  relative  positions  on  the  Earth's  surface. 
The  first  NRL  radar  contact  with  the  Moon  at  a  microwave  frequency  took  place  at  2860 
MHz  (10-cm)  and  was  accomplished  with  the  Branch's  15-meter  (50-ft)  radio  telescope.69 

Although  interest  in  bouncing  radio  and  radar  waves  off  the  Moon  drew  military  and 
civilian  researchers  to  early  radar  astronomy  conferences,  lunar  communication  schemes 
failed  to  provide  either  a  theoretical  or  a  funding  framework  within  which  radar  astrono- 
my could  develop.  The  rapidly  growing  field  of  ionospheric  research,  on  the  other  hand, 
provided  both  theoretical  and  financial  support  for  radar  experiments  on  meteors  and 
the  Moon.  Despite  the  remarkable  variety  of  radar  experiments  carried  out  in  the  years 
following  World  War  II,  radar  achieved  a  wider  and  more  permanent  place  in  ionospher- 
ic research  (especially  meteors  and  auroras)  than  in  astronomy. 


67.  Grieg,   Metzger,   and  Waer,   pp.   652-663;    "Via   the   Moon:   Relay  Station   to  Transoceanic 
Communication,"  Newsweek  27  (1 1  February  1946):  64;  Sulzer,  Montgomery,  and  Gerks,  "An  U-H-F  Moon  Relay," 
Proceedings  of  the  IKE  40  ( 1952) :  361 .  A  few  years  later,  three  amateur  radio  operators,  "hams"  who  enjoyed  detect- 
ing long-distance  transmissions  (DXing),  succeeded  in  bouncing  144-Mhz  radio  waves  off  the  Moon,  on  23  and 
27  January  1953.  E.  P.  T,  "Lunar  DX  on  144  Me!"  QST37  (1953):  11-12  and  116. 

68.  Gebhard,  pp.  115-116;  James  H.  Trexler,  "Lunar  Radio  Echoes,"  Proceedings  of  the  IRE  46  (1958): 
286-288. 

69.  NRL,  "The  Space  Science  Division  and  E.  O.  Hulburt  Center  for  Space  Research,  Program  Review," 
1968,  NRLHRC;  Yaplee,  R.  H.  Bruton,  K.  J.  Craig,  and  Nancy  G.  Roman,  "Radar  Echoes  from  the  Moon  at  a 
Wavelength  of  10  cm,"  Proceedings  oftheIRE46  (1958):  293-297;  Gebhard,  p.  118. 


26  TO  SEE  THE  UNSEEN 


All  that  changed  with  the  start  of  the  U.S./U.S.S.R.  Space  Race  and  the  announce- 
ment of  the  first  planetary  radar  experiment  in  1958.  That  experiment  was  made  possible 
by  the  rivalries  of  the  Cold  War,  which  fostered  a  concentration  of  expertise  and  financial, 
personnel,  and  material  resources  that  paralleled,  and  in  many  ways  exceeded,  that  of 
World  War  II.  The  new  Big  Science  of  the  Cold  War  and  the  Space  Race,  often  indistin- 
guishable from  each  other,  gave  rise  to  the  radar  astronomy  of  planets. 

The  Sputnik  and  Lunik  missions  were  not  just  surprising  demonstrations  of  Soviet 
achievements  in  science  and  technology.  Those  probes  had  been  propelled  off  the  Earth 
by  ICBMs,  and  an  ICBM  capable  of  putting  a  dog  in  Earth-orbit  or  sending  a  probe  to  the 
Moon  was  equally  capable  of  delivering  a  nuclear  bomb  from  Moscow  to  New  York  City. 
Behind  the  Space  Race  lay  the  specter  of  the  Cold  War  and  World  War  III,  or  to  para- 
phrase Clausewitz,  the  Space  Race  was  the  Cold  War  by  other  means.  Just  as  the  vulnera- 
bility of  Britain  to  air  attacks  had  led  to  the  creation  of  the  Chain  Home  radar  warning 
network,  the  defenselessness  of  the  United  States  against  aircraft  and  ICBM  attacks  with 
nuclear  bombs  and  warheads  led  to  the  creation  of  a  network  of  defensive  radars.  The 
development  of  that  network  in  turn  provided  the  instrument  with  which  planetary  radar 
astronomy,  driven  by  the  availability  of  technology,  would  begin  in  the  United  States. 


Chapter  Two 

Fickle  Venus 


In  1958,  MIT's  Lincoln  Laboratory  announced  that  it  had  bounced  radar  waves  off 
Venus.  That  apparent  success  was  followed  by  another,  but  in  England,  during  Venus'  next 
inferior  conjunction.  In  September  1959,  investigators  at  Jodrell  Bank  announced  that 
they  had  validated  the  1958  results,  yet  Lincoln  Laboratory  failed  to  duplicate  them.  All 
uncertainty  was  swept  aside,  when  the  Jet  Propulsion  Laboratory  (JPL)  obtained  the  first 
unambiguous  detection  of  echoes  from  Venus  in  1961. 

As  we  saw  in  the  case  of  radar  studies  of  meteors  and  the  Moon  in  the  1940s  and 
1950s,  planetary  radar  astronomy  was  driven  by  technology.  The  availability  of  military 
apparatus  made  possible  the  rise  of  radar  astronomy  in  Britain  in  the  1940s.  Just  as  the 
threat  of  airborne  invasion  gave  rise  to  the  Chain  Home  radar,  the  Cold  War  and  its  sci- 
entific counterpart,  the  Space  Race,  demanded  the  creation  of  a  new  generation  of  defen- 
sive radars,  and  those  radars  made  possible  the  first  planetary  radar  experiments.  Even 
British  and  Soviet  planetary  radar  astronomy  were  not  free  of  the  sway  of  military  and 
space  efforts.  Thus,  the  Big  Science  efforts  brought  into  being  by  the  Cold  War  and  the 
Space  Race  provided  the  material  resources  necessary  for  the  emergence  of  planetary 
radar  astronomy. 

The  initial  radar  detections  of  Venus  signaled  a  benchmark  in  radar  capacity  that 
separated  a  new  generation  of  radars  from  their  predecessors.  High-speed  digital  com- 
puters linked  to  more  powerful  transmitters  and  more  sensitive  receivers  utilizing  state-of- 
the-art  masers  and  parametric  amplifiers  provided  the  new  capacity.  As  we  saw  in  Chapter 
One,  initial  radar  astronomy  targets  were  either  ionospheric  phenomena,  like  meteors 
and  auroras,  or  the  Moon,  whose  mean  distance  from  Earth  is  about  384,000  kilometers. 
The  new  radars  reached  beyond  the  Moon  to  Venus,  about  42  million  kilometers  distant 
at  its  closest  approach  to  Earth. 

Radar  detections  of  the  planets,  while  sterling  technical  achievements,  were  inca- 
pable of  demonstrating  the  value  of  planetary  radar  as  an  ongoing  scientific  activity.  As 
radar  astronomy  already  had  achieved  with  meteor  studies,  planetary  radar  became  a  sci- 
entific activity  by  solving  problems  left  unsolved  or  unsatisfactorily  solved  by  optical 
means. 

As  they  made  their  first  detections  of  Venus,  planetary  radar  astronomers  found  and 
solved  two  such  problems.  One  was  the  rotation  of  Venus,  the  determination  of  which  was 
prevented  by  the  planet's  optically  impenetrable  atmosphere.  The  other  problem  was  the 
astronomical  unit,  the  mean  radius  of  the  Earth's  orbit  around  the  Sun.  Astronomers 
express  the  distances  of  the  planets  from  the  Sun  in  terms  of  the  astronomical  unit,  but 
agreement  on  its  exact  value  was  lacking.  Radar  observations  of  Venus  provided  an  exact 
value,  which  the  International  Astronomical  Union  adopted,  and  revealed  the  planet's 
retrograde  rotation. 

While  the  astronomical  unit  and  the  rotation  of  Venus  interested  astronomers,  they 
also  held  potential  benefit  for  the  nascent  space  program.  In  many  respects,  the  problems 
solved  by  the  first  planetary  radar  experiments  needed  solutions  because  of  the  Space 
Race.  By  February  1958,  when  Lincoln  Laboratory  first  tried  to  bounce  radar  waves  off 
Venus,  Sputnik  1  and  the  Earth-orbiting  dog  Laika  were  yesterday's  news.  The  Space  Race 
was  hot,  and  so  was  the  competition  between  the  United  States  and  the  Soviet  Union. 


27 


28  TO  SEE  THE  UNSEEN 


Planetary  radar  astronomy  rode  the  cresting  waves  of  Big  Science  (the  Space  Race)  and 
the  Cold  War  well  into  the  1970s. 

From  the  Rad  Lab  to  Millstone  Hill 

Scientists  and  engineers  at  MIT's  Lincoln  Laboratory  attempted  to  reach  Venus  by 
radar  in  1958,  because  they  had  access  to  a  radar  of  unprecedented  capability.  The  radar 
existed  because  MIT,  as  it  had  since  the  days  of  the  Radiation  Laboratory,  conducted  mil- 
itary electronics  research.  Lincoln  Laboratory  did  not  emerge  directly  from  the  Radiation 
Laboratory  but  through  its  direct  descendant,  the  Research  Laboratory  of  Electronics 
(RLE). 

The  RLE,  a  joint  laboratory  of  the  Physics  and  Electrical  Engineering  Departments, 
continued  much  of  the  fundamental  electronic  research  of  the  Radiation  Laboratory.  The 
Signal  Corps,  Air  Force,  and  the  Office  of  Naval  Research  jointly  funded  the  new  labora- 
tory, with  the  Signal  Corps  overseeing  the  arrangement.  Former  Radiation  Laboratory 
employees  filled  research  positions  at  the  RLE,  which  occupied  a  temporary  structure  on 
the  MIT  campus  erected  earlier  for  the  Radiation  Laboratory.  The  two  leaders  of  the 
Lincoln  Laboratory  Venus  radar  experiment,  Robert  Price  and  Paul  E.  Green,  Jr.,  were 
both  student  employees  of  the  RLE.  Price  also  had  an  Industrial  Fellowship  in  Electronics 
from  Sperry.  Among  the  other  early  RLE  fellowship  sponsors  were  the  General  Radio 
Company,  RCA,  ITT,  and  the  Socony-Vacuum  Oil  Company. 

In  September  1949,  the  Soviet  Union  detonated  its  first  nuclear  bomb;  within 
months  civil  war  exploded  in  Korea.  The  need  for  a  United  States  air  defense  capable  of 
coping  with  a  nuclear  attack  was  urgent.  Project  Charles,  a  group  of  military  and  civilian 
experts,  studied  the  problems  of  air  defense.  Its  findings  led  directly  to  the  creation  of 
Lincoln  Laboratory  in  the  Autumn  of  195 1.1 

MIT  was,  in  the  words  of  Hoyt  S.  Vandenberg,  U.S.  Air  Force  chief  of  staff,  "unique- 
ly qualified  to  serve  as  contractor  to  the  Air  Force  for  the  establishment  of  the  proposed 
[Lincoln]  laboratory.  Its  experience  in  managing  the  Radiation  Laboratory  of  World  War 
II,  the  participation  in  the  work  of  ADSEC  [Air  Defense  Systems  Engineering  Committee] 
by  Professor  [George  E.]  Valley  and  other  members  of  the  MIT  staff,  its  proximity  to 
AFCRL  [Air  Force  Cambridge  Research  Laboratories] ,  and  its  demonstrated  competence 
in  this  sort  of  activity  have  convinced  us  that  we  should  be  fortunate  to  secure  the  services 
of  MIT  in  the  present  connection."2 

Lincoln  Laboratory  was  to  design  and  develop  what  became  known  as  SAGE  (Semi- 
Automatic  Ground  Environment),  a  digital,  integrated  computerized  North-American 
network  of  air  defense.  SAGE  involved  a  diversity  of  applied  research  in  digital  computing 
and  data  processing,  long-range  radar,  and  digital  communications.  The  Army,  Navy,  and 
Air  Force  jointly  underwrote  Lincoln  Laboratory  through  an  Air  Force  prime  contract. 
The  Air  Force  provided  nearly  90  percent  of  the  funding.  In  1954,  Lincoln  Laboratory 
moved  out  of  its  Radiation  Laboratory  buildings  on  the  MIT  campus  and  into  a  newly  con- 
structed facility  at  Hanscom  Field,  in  Lexington,  Massachusetts,  next  to  the  Air  Force 
Cambridge  Research  Center. 


1.  "President's  Report  Issue,"  MIT  Bulletin  vol.  82,  no.  1  (1946):  133-136;  ibid.,  vol.  83,  no.  1  (1947): 
154-157;  ibid.,  vol.  86,  no.  1   (1950):  209;  "Government  Supported  Research  at  MIT:  An  Historical  Survey 
Beginning  with  World  War  II:  The  Origins  of  the  Instrumentation  and  Lincoln  Laboratories,"  May  1969,  typed 
manuscript,  pp.  15-19  and  30-31,  MITA;  George  E.  Valley,  Jr.,  rough  draft,  untitled  four  page  manuscript,  13 
October  1953,  6/135/AC  4,  and  MIT  Review  Panel  on  Special  Laboratories,  "Final  Report,"  pp.  132-133,  MITA. 
James  R.  Killian,  Jr.,  The  Education  of  a  College  President:  A  Memoir  (Cambridge:  The  MIT  Press,  1985),  pp.  71-76, 
recounts  the  founding  of  Lincoln  Laboratory,  too. 

2.  Vandenberg  to  James  R.  Killian,  Jr.,  15  December  1950,  3/136/AC  4,  MITA.  A  portion  of  the  quote 
also  appears  in  Killian,  p.  71. 


FICKLE  VENUS  29 


Lincoln  Laboratory  quickly  began  work  on  the  Distant  Early  Warning  (DEW)  Line 
in  the  arctic  region  of  North  America.  The  first  experimental  DEW-line  radar  units  were 
in  place  near  Barter  Island,  Alaska,  by  the  end  of  1953.  The  radar  antennas  were  enclosed 
by  a  special  structure  called  a  radome,  which  protected  them  from  arctic  winds  and  cold. 

Intercontinental  Ballistic  Missiles  (ICBMs)  challenged  the  DEW  Line  and  the  North 
American  coordinated  defense  network,  which  had  been  designed  to  warn  against  air- 
plane attacks.  ICBMs  could  carry  nuclear  warheads  above  the  ionosphere,  higher  than  any 
pilot  could  fly;  existing  warning  radars  were  useless.  In  order  to  detect  and  track  ICBMs, 
radars  would  have  to  recognize  targets  smaller  than  airplanes  at  altitudes  several  hundred 
kilometers  above  the  Earth  and  at  ranges  of  several  thousand  kilometers.  The  new  radars 
would  have  to  distinguish  between  targets  and  auroras,  meteors,  and  other  ionospheric 
disturbances,  which  experience  already  had  shown  were  capable  of  crippling  military 
communications  and  radars.3 

In  1954,  Lincoln  Laboratory  began  initial  studies  of  Anti-InterContinental  Ballistic 
Missile  (AICBM)  systems  and  the  creation  of  the  Ballistic  Missile  Early  Warning  System 
(BMEWS).  By  the  spring  of  1956,  the  construction  of  an  experimental  prototype  BMEWS 
radar  was  underway.  Its  location,  atop  Millstone  Hill  in  Westford,  Massachusetts,  was  well 
away  from  air  routes  and  television  transmitters  and  close  to  MIT  and  Lincoln  Laboratory. 
The  Air  Force  owned  and  financed  the  radar,  while  Lincoln  Laboratory  managed  it  under 
Air  Force  contract  through  the  adjacent  Air  Force  Cambridge  Research  Center. 

Herbert  G.  Weiss  was  in  charge  of  designing  and  building  Millstone.  After  graduat- 
ing from  MIT  in  1936  with  a  BS  in  electrical  engineering,  Weiss  conducted  microwave 
research  for  the  Civil  Aviation  Authority  in  Indianapolis  and  worked  in  the  MIT  Radiation 
Laboratory.  After  the  war,  Weiss  worked  at  Los  Alamos,  then  at  Raytheon,  before  return- 
ing to  MIT  to  work  on  the  DEW  radars. 

Millstone  embodied  a  new  generation  of  radars  capable  of  detecting  smaller  objects 
at  farther  ranges.  Thanks  to  specially  designed,  3-meter-tall  (11-feet-tall)  klystron  tubes, 
Millstone  was  intended  to  have  an  unprecedented  amount  of  peak  transmitting  power, 
1.25  megawatts  from  each  klystron  (2.5  megawatts  total).  Its  frequency  was  440  MHz  (68 
cm) .  The  antenna,  a  steerable  parabolic  dish  26  meters  (84-feet)  from  rim  to  rim,  stood 
on  a  27-meter-high  (88-foot-high)  tower  of  concrete  and  steel.  Millstone  began  operating 
in  October  1957,  just  in  time  to  skin  track  the  first  Sputnik. 


3.  Valley;  "Final  Report,"  pp.  133-137;  "Government  Supported,"  p.  33;  C.  L.  Strong,  Information 
Department,  Western  Electric  Company,  press  release,  1  October  1953,  6/135/AC  4,  MITA;  Carl  F.  J.  Overhage 
to  LL  Gen.  Roscoe  C.  Wilson,  15  October  1959,  and  brochure,  "Haystack  Family  Day,  10  October  1964," 
1/24/AC  134,  MITA;  F.  W.  Loomis  to  Killian,  17  April  1952,  4/135/AC  4,  MITA;  various  documents  in 
2/136/AC  4  and  7/135/AC  4,  MITA;  Overhage,  "Reaching  into  Space  with  Radar,"  paper  read  at  MIT  Club  of 
Rochester,  25  February  1960,  pp.  6-7, 1 .1.1  A.  For  a  popular  introduction  to  the  DEW  Line,  see  Richard  Morenus, 
Dew  Line:  Distant  Early  Warning,  The  Miracle  of  America 's  First  Line  of  Defense  (New  York:  Rand  McNally,  1957) . 


30 


TO  SEE  THE  UNSEEN 


Figure  4 

The  Lincoln  Laboratory  Millstone  Hill  Radar  Observatory,  ca.  1958.  (Courtesy  of  MIT  Lincoln  Laboratory,  Lexington, 
Massachusetts,  photo  no.  P489-128.) 

Millstone  furnished  valuable  scientific  and  technological  information  to  the  military, 
while  advancing  ionospheric  and  lunar  radar  research.  In  addition  to  testing  and  evaluat- 
ing new  defense  radar  techniques  and  components,  its  scientific  missions  included  mea- 
suring the  ionosphere  and  its  influence  on  radar  signals  (such  as  Faraday  rotation), 
observing  satellites  and  missiles,  and  performing  radar  studies  of  auroras,  meteors,  and 
the  Moon,  all  of  which  were  potential  sources  of  false  alarm  for  BMEWS  radars.4 

The  Lunchtime  Conversazione 

The  idea  of  using  the  Millstone  Hill  radar  to  bounce  signals  off  Venus  arose  during 
one  of  the  customary  lunchtime  discussions  between  Bob  Price  and  Paul  Green.  As  MIT 
doctoral  students  and  later  as  Lincoln  Laboratory  engineers,  Price  and  Green  worked 
closely  together  under  Wilbur  B.  Davenport,  Jr.,  their  laboratory  supervisor  and  disserta- 
tion director.  They  worked  on  different  aspects  of  NOMAC  (NOise  Modulation  And 
Correlation),  a  high-frequency  communication  system  (known  by  the  Army  Signal  Corps 
production  name  F9C)  that  used  pseudonoise  sequences,  and  on  Rake,  a  receiver  that 


4.  Weiss  29  September  1993;  "Final  Report,"  pp.  136  and  138;  Overhage,  "Reaching  into  Space,"  p.  2; 
Overhage  to  Wilson,  30  June  1961,  1/24/AC  134,  MITA;  Allen  S.  Richmond,  "Background  Information  on 
Millstone  Hill  Radar  of  MIT  Lincoln  Laboratory,"  5  November  1958,  typed  manuscript,  LLLA;  Weiss,  Space  Radar 
Trackers  and  Radar  Astronomy  Systems,  J A- 1740-22  (Lexington:  Lincoln  Laboratory,  June  1961),  pp.  21-23,  29,  44 
and  64;  Price,  "The  Venus  Radar  Experiment,"  in  E.  D.  Johann,  ed.,  Data  Handling  Seminar,  Aachen,  Germany, 
September  21,  1959  (London:  Pergamon  Press,  1960),  p.  81;  Price,  P.  Green,  Thomas  J.  Goblick,  Jr.,  Robert  H. 
Kingston,  Leon  G.  Kraft,  Jr.,  Gordon  H.  Pettengill,  Roland  Silver,  William  B.  Smith,  "Radar  Echoes  from  Venus," 
Science  129  (1959):  753;  "Missile  Radar  Probes  Arctic,"  Electronics  30  (1957):  19;  Pettengill  28  September  1993. 


FICKLE  VENUS  31 


solved  NOMAC  multipath  propagation  problems.  Later,  what  Lincoln  Laboratory  called 
NOMAC  came  to  be  called  spread  spectrum. 

Their  work  was  vital  to  maintaining  military  communications  in  the  face  of  enemy 
jamming.  One  of  their  units  went  to  Berlin  in  1959  in  anticipation  of  a  blockade  to  pro- 
vide essential  communications  in  case  of  jamming.  The  Soviet  Union  already  had  demon- 
strated its  jamming  expertise  against  the  Voice  of  America.  Conceivably,  all  NATO  com- 
munications could  be  jammed  in  time  of  war.  The  Lincoln  Laboratory  anti-jamming  pro- 
ject was  a  direct  response  to  that  threat.5 

Radio  astronomy,  which  influenced  the  rise  of  planetary  radar  astronomy  during  the 
1960s,  played  a  small  role  in  the  Lincoln  Laboratory  Venus  experiment.  Price  actually  had 
worked  at  the  University  of  Sydney  under  radio  astronomer  Gordon  Stanley  and  met  such 
pioneers  as  Pawsey,  Taffy  Bowen,  Paul  Wild,  Bernie  Mills,  and  Chris  Christiansen.  A 
recently  published  book  on  radio  astronomy  by  the  Australian  scientists  J.  L.  Pawsey  and 
Ronald  N.  Bracewell  was  the  subject  of  lunch  conversation  between  Green  and  Price  in 
the  Lincoln  Laboratory  cafeteria.  The  chapter  on  radar  astronomy  predicted  that  one  day 
man  would  bounce  radar  waves  off  the  planets.  But  radio  astronomy  did  not  give  rise  to 
the  decision  to  attempt  a  radar  detection  of  Venus.6 

What  did  trigger  the  decision  was  the  completion  of  the  Millstone  facility.  Green  and 
Price  wondered  if  it  was  powerful  enough  to  bounce  radar  signals  off  Venus.  Gordon 
Pettengill,  a  junior  member  of  the  team,  joined  the  lunchtime  discussions.  Trained  in 
physics  at  MIT  and  an  alumnus  of  Los  Alamos,  Pettengill  had  an  office  at  Millstone.  After 
making  calculations  on  a  paper  napkin,  though,  they  estimated  that  Millstone  did  not 
have  enough  detectability  for  the  experiment,  even  if  one  assumed  that  Venus  was  per- 
fectly reflective. 

The  lunchtime  conversazione  went  nowhere,  until  Robert  H.  Kingston,  who  had  a 
joint  MIT  and  Lincoln  Laboratory  appointment,  joined  the  discussions.  Kingston  had  just 
built  a  maser.  "Within  an  hour,"  Green  recalled,  "we  had  the  whole  damn  thing  mapped 
out."7  The  maser  gave  the  radar  receiver  the  sensitivity  necessary  to  carry  out  the  experi- 
ment. 

The  maser,  an  acronym  for  Microwave  Amplification  by  Stimulated  Emission  of 
Radiation,  was  a  new  type  of  solid-state  microwave  amplifying  device  vaunted  by  one 
author  as  "the  greatest  single  technological  step  in  radio  physics  for  many  years,  with  the 
possible  exception  of  the  transistor,  comparable  say  with  the  development  of  the  cavity 
magnetron  during  the  Second  World  War."  The  maser  was  at  the  heart  of  the  low-noise 
microwave  amplifiers  used  in  radio  astronomy.  The  first  radio-astronomy  maser 
application,  a  joint  effort  by  Columbia  University  and  the  Naval  Research  Laboratory, 
occurred  in  April  1958.  The  first  use  of  a  maser  in  radar  astronomy,  however,  preceded 
that  application  by  two  months,  in  February  1958,  at  Millstone.  While  most  masers 


5.  William  W.  Ward,  "The  NOMAC  and  Rake  Systems,"  The  Lincoln  Laboratory  Journal  vol.  5,  no.  3 
(1992):  351-365;  Green  20  September  1993;  Price  27  September  1993.  Green  and  Price  acknowledged  each 
other  in  their  dissertations.  Green,  "Correlation  Detection  using  Stored  Signals"  D.Sc.  diss.,  MIT,  1953,  and 
Price,  "Statistical  Theory  Applied  to  Communication  through  Multipath  Disturbances,"  D.Sc.  diss.,  MIT,  1953. 

A  history  of  the  subject,  R.  A.  Scholtz,  The  Origins  of  Spread-Spectrum  Communications,"  IEEE 
Transactions  on  Communications  COM-30  (1982):  822-854,  is  reproduced  in  Marvin  K.  Simon,  Jim  K.  Omura, 
Scholtz,  and  Barry  K.  Levitt,  eds.,  Spread  Spectrum  Communications  (Rockville,  Md.:  Computer  Science  Press,  Inc., 
1985),  Volume  1,  Chapter  2,  "The  Historical  Origins  of  Spread-Spectrum  Communications,"  pp.  39-134.  Price, 
"Further  Notes  and  Anecdotes  on  Spread-Spectrum  Origins,"  IEEE  Transactions  on  Communications  COM-31 
(January  1983):  85-97,  provides  an  absorbing  anecdotal  sequel  to  Scholtz. 

6.  Pawsey  and  Bracewell,  Radio  Astronomy  (Oxford:  Clarendon  Press,  1955) ;  Green  20  September  1993; 
Price  27  September  1993. 

7.  Green  20  September  1993;  Pettengill  28  September  1993.  For  a  description  of  the  maser,  see 
Kingston,  A  VHP  Solid  State  Maser,  Group  Report  M35-79  (Lexington:  Lincoln  Laboratory,  1957);  and  Kingston, 
A  UHF  Solid  State  Maser,  Group  Report  M35-84A  (Lexington:  Lincoln  Laboratory,  1958). 


32  TO  SEE  THE  UNSEEN 


functioned  above  1,000  MHz,  Kingston's  operated  in  the  UHF  region,  around  440  MHz, 
and  reduced  overall  system  noise  temperature  to  an  impressive  170  K.8 

Despite  the  maser's  low  noise  level,  Price  and  Green  knew  that  they  would  have  to 
raise  the  level  of  the  Venus  echoes  above  that  of  the  noise.  Their  NOMAC  antijamming 
work  had  prepared  them  for  this  problem.  They  chose  to  integrate  the  return  pulses  over 
time,  as  Zoltan  Bay  had  done  in  1946.  In  theory,  the  signals  buried  in  the  noise  reinforced 
each  other  through  addition,  while  the  noise  averaged  out  by  reason  of  its  random 
nature.9 

A  digital  computer,  as  well  as  additional  digital  data  processing  equipment,  linked  to 
the  Millstone  radar  system  performed  the  integration  and  analysis  of  the  Venusian  echoes. 
An  analog-to-digital  converter,  initially  developed  for  ionospheric  research  by  William  B. 
Smith,  digitized  information  on  each  radar  echo.  That  information  simultaneously  was 
recorded  on  magnetic  tape  and  fed  to  a  solid-state  digital  computer.  The  experiment  was 
innovative  in  digital-signal  processing  and  marked  one  of  the  earliest  uses  of  digital  tape 
recorders.10 

Venus  or  Bust 

Kingston's  maser  was  installed  at  Millstone  Hill  just  in  time  for  the  inferior  conjunc- 
tion of  Venus.  However,  a  klystron  failure  left  only  265  kilowatts  of  transmitter  power  avail- 
able for  the  experiment.  On  10  and  12  February  1958,  the  radar  was  pointed  to  detect 
Venus,  then  some  45  million  kilometers  (28  million  miles)  away.  The  radar  signals  took 
about  five  minutes  to  travel  the  round-trip  distance.  In  contrast,  John  DeWitt's  signals 
went  to  the  Moon  and  back  to  Fort  Monmouth,  NJ,  in  only  about  2.5  seconds. 

Of  the  five  runs  made,  only  four  of  the  digital  recordings  had  few  enough  tape  blem- 
ishes that  they  could  be  easily  edited  and  run  through  the  computer.  Two  of  the  four  runs, 
one  from  each  day,  showed  no  evidence  of  radar  returns.  The  others  had  one  peak  each. 
Price  recalled,  "When  we  saw  the  peaks,  we  felt  very  blessed."11  It  was  not  absolutely  clear, 
however,  that  the  two  peaks  were  really  echoes. 

Green  explained:  "We  looked  into  our  soul  about  whether  we  dared  to  go  public  with 
this  news.  Bob  was  the  only  guy  who  really  stayed  with  it  to  the  end.  He  had  convinced 
himself  that  he  had  seen  it,  and  he  had  convinced  me  that  he  had  seen  it.  Management 
asked  us  to  have  a  consultant  look  at  our  results,  and  we  did."  Thomas  Gold  of  Cornell 
University  looked  at  the  peaks  and  said  "Yes,  I  think  you  should  publish  this."  Green  and 
Price  then  published  their  findings  in  the  20  March  1959  issue  of  Science,  the  journal  of 


8.  J.  V.  Jelley,  The  Potentialities  and  Present  Status  of  Masers  and  Parametric  Amplifiers  in  Radio 
Astronomy,"  Proceedings  of  the  IEEE  51  (1963):  31  and  36,  esp.  30;  J.  W.  Meyer,  The  Solid  State  Maser— Principles, 
Applications,  and  Potential,  Technical  Report  ESD-TR-68-261  (Lexington:  Lincoln  Laboratory,  1960),  pp.  14-16; 
J.  A.  Giordmaine,  L.  E.  Alsop,  C.  H.  Mayer,  and  C.  H.  Townes,  "A  Maser  Amplifier  for  Radio  Astronomy  at  X- 
band,"  Proceedings  of  the  IRE  47  (1959):  1062-1070;  Pettengill  and  Price,  "Radar  Echoes  from  Venus  and  a  New 
Determination  of  the  Solar  Parallax,"  Planetary  and  Space  Science  5  (1961):  73.  For  Townes  and  the  invention  of 
the  maser,  see  Paul  Forman,  "Inventing  the  Maser  in  Postwar  America,"  Osiris  ser.  2,  vol.  7  (1992):  105-134. 

9.  Price,  p.  70;  Price  et  al,  p.  751.  Later,  Price  acknowledged  the  pioneering  integration  work  of  Zoltan 
Bay  in  1946.  Price,  p.  73.  Kerr,  "On  the  Possibility  of  Obtaining  Radar  Echoes  from  the  Sun  and  Planets," 
Proceedings  of  the  IRE  40  (1952):  660-666,  specifically  recommended  long-period  integration  for  radar  observa- 
tion of  Venus. 

10.  Smith  graduated  MIT  in  1955  with  a  master's  degree  in  electrical  engineering  and  worked  with  Price 
and  Green  on  the  F9C  in  Davenport's  group.  Smith  29  September  1993;  Green  20  September  1993;  Price 
27  September  1993;  Price,  p.  72;  Price  et  al,  p.  751;  Scholtz,  p.  838;  Weiss,  Space  Radar  Trackers,  pp.  53,  59,  61  and 
63-64;  "Biographical  data,  MIT  Lincoln  Laboratory,"  18  March  1959,  LLLA. 

11.  Price  27  September  1993;  Weiss,  Space  Radar  Trackers,  pp.  29  and  44;  Price,  pp.  71  and  76;  Price  et 
al,  p.  751. 


FICKLE  VENUS  33 


the  American  Association  for  the  Advancement  of  Science,  13  months  after  their 
observations  in  February  1958.12 

By  then,  despite  the  unsuccessful  Lunik  I  Moon  shot,  the  Soviet  Union  had  achieved 
a  number  of  successful  satellite  launches.  The  United  States  space  effort  still  was  marked 
by  repeated  failures.  All  of  the  four  Pioneer  Moon  launches  of  1958  ended  in  failure. 
There  was  a  desperate  need  for  good  news;  the  Lincoln  Laboratory  publicity  department 
gave  the  Venus  radar  experiment  full  treatment.  In  addition  to  a  press  conference,  Green 
and  Price  quickly  found  themselves  on  national  television  and  on  the  front  page  of  the 
New  York  Times.  President  Eisenhower  sent  a  special  congratulatory  telegram  calling  the 
experiment  a  "notable  achievement  in  our  peaceful  ventures  into  outer  space."13 

Once  Price  and  Green  accepted  the  validity  of  the  two  peaks,  the  next  step  was  to 
determine  the  distance  the  radar  waves  travelled  to  Venus  and  to  calculate  a  value  for  the 
astronomical  unit.  They  estimated  a  value  of  149,467,000  kilometers  and  concluded, 
moreover,  that  it  did  not  differ  enough  from  those  found  in  the  astronomical  literature  to 
warrant  a  re-evaluation  of  the  astronomical  unit.14 

The  Lincoln  Laboratory  1958  Venus  experiment  launched  planetary  radar  astrono- 
my; Millstone  Hill  was  the  prototype  planetary  radar.  Its  digital  electronics,  recording  of 
data  on  magnetic  tape  for  subsequent  analysis,  use  of  a  maser  (or  other  low-noise 
microwave  amplifier)  and  a  digital  computer,  and  long-period  integration  all  became  stan- 
dard equipment  and  practice.  As  with  any  experiment,  scientists  must  be  able  to  duplicate 
results.  The  next  inferior  conjunction  provided  an  opportunity  for  scientists  at  Jodrell 
Bank  to  attempt  Venus,  too. 

Jodrell  Bank  had  a  new,  76-meter  (250-ft)  radio  telescope,  the  largest  of  its  type  in 
the  world.  Although  planned  as  early  as  1951,  the  telescope  did  not  detect  its  first  radio 
waves  until  1957  as  a  consequence  of  a  long,  nightmarish  struggle  with  financial  and  con- 
struction difficulties.  The  civilian  Department  of  Scientific  and  Industrial  Research  and 
the  Nuffield  Foundation  underwrote  its  design  and  construction.  Success  in  detecting 
Soviet  and  American  rocket  launches  brought  visits  from  Prince  Philip  and  Princess 
Margaret  and  fame.  Fame  in  turn  brought  solvency  and  a  name  (the  Nuffield  Radio 
Astronomy  Laboratories,  Jodrell  Bank) . 

Although  the  design  and  construction  of  the  large  dish  was  unquestionably  an  enter- 
prise carried  out  with  civilian  funding,  radar  research  at  Jodrell  Bank  owed  a  debt  to  the 
United  States  armed  forces;  however,  that  military  research  was  limited  to  meteor  studies 
carried  out  with  the  smaller  antennas,  not  the  76-meter  (250-ft)  dish.  The  U.S.  Air  Force 
and  the  Office  of  Naval  Research  supplied  additional  money  for  tracking  rocket  launch- 
es, while  the  European  Office  of  the  U.S.  Air  Force  Research  and  Development  Command 
(EOARDC)  funded  general  electronics  research  at  a  modest  level.  During  the  Cuban  mis- 
sile crisis,  the  76-meter  (250-ft)  radio  telescope  served  to  detect  missiles  that  might  be 
launched  from  the  Soviet  Union.  From  intelligence  sources,  the  locations  of  such  missiles 
directed  against  London  were  known,  and  the  telescope  was  aimed  accordingly.  No  U.S. 
equipment  or  funding  were  engaged  in  this  effort,  though.15 


12.  Green  20  September  1993;  Gold  14  December  1993;  Price  et  al,  pp.  751-753. 

13.  Green  20  September  1993;  Price  27  September  1993;  Pettengill  28  September  1993;  Overhage  to 
Wilson,  24  March  1959,  1/24/AC  134,  MITA;  "Venus  is  Reached  by  Radar  Signals,"  New  York  Times,  vol.  108  (20 
March  1959),  pp.  1  and  11. 

14.  For  their  calculation  of  the  astronomical  unit,  see  Pettengill  and  Price,  "Radar  Echoes  from  Venus 
and  a  New  Determination  of  the  Solar  Parallax,"  Planetary  and  Space  Science  5  (1961):  71-74. 

15.  Lovell,  11  January  1994;  Lo\e\\,JodreU  Bank,  passim,  but  especially  pp.  220-222,  224,  242,  225.  On 
the  Foundation,  see  Ronald  William  Clark,  A  Biography  of  the  Nuffield  Foundation  (London:  Longman,  1972). 
Created  in  1962,  EOARDC  was  essentially  a  military  operation  headquartered  in  Brussels.  It  underwrote  a  wide 
range  of  European  scientific  research,  though  more  money  went  into  electronics  research  than  any  other  field. 
Howard  J.  Lewis,  "How  our  Air  Force  Supports  Basic  Research  in  Europe,"  Science  131  (1960):  15-20.  From 


34 


TO  SEE  THE  UNSEEN 


Figure  5 

TheJodreU  Bank  250-foot  (76-meter)  telescope  in  June  1961.  The  control  room  is  partially  visible  bottom  left.  The  1962  and 
1964Jodrell  Bank  Venus  radar  experiments  were  carried  out  using  a  U.S.-supplied  continuous-wave  radar  mounted  on  this 
telescope.  (Courtesy  of  the  Director  of  the  Nuffield  Radio  Astronomy  Laboratories,  Jodrell  Bank.) 

Preparation  for  the  1959  Venus  experiment  began  in  1957,  as  the  dish  was  reaching 
completion.  The  telescope,  however,  was  not  yet  ready  for  radar  work.  John  Evans  recog- 
nized that  its  transmitter  power  and  operating  frequency  would  have  to  be  raised  in  order 
to  achieve  critical  extra  gain  for  the  Venus  experiment.  The  100-MHz  (3-meter),  10-kilo- 
watt  Moon  radar  was  not  powerful  enough.  The  University  of  Manchester  Physics 
Department  had  developed  a  400-MHz  (75-cm),  100-kilowatt  klystron.  "It  was  a  real 
kludge,"  Evans  later  recalled,  "because  it  was  basically  a  Physics  Department  experiment. 
It  was  continuously  pumped;  it  sat  on  top  of  vacuum  pumps,  which  required  liquid  nitro- 
gen for  cooling."16 

Lovell  had  the  General  Electric  Company  of  Britain  supply  a  modulator  for  the  kly- 
stron. Evans  was  responsible  for  designing  and  building  the  rest  of  the  equipment.  As  the 
1958  Venus  inferior  conjunction  approached,  "we  simply  were  not  ready,  and  Lovell  was 
quite  upset,"  Evans  explained.  Out  of  desperation,  Evans  employed  the  100-MHz  Moon 
radar  enhanced  with  a  computer  integration  scheme,  but  the  equipment  failed  to  detect 
echoes.  When  Lincoln  Laboratory  announced  its  success,  Evans  recalled,  "We  shrugged 
and  felt  we  were  beaten  to  the  punch." 

The  1958  Jodrell  Bank  failure  put  all  that  much  more  pressure  on  Evans  to  produce 
results  during  the  next  inferior  conjunction  of  September  1959.  The  transmitter  was  more 


August  1957,  when  Jodrell  Bank  began  preliminary  calibration  measurements  to  August  1970,  the  telescope 
gathered  results  for  68,538  hours.  Of  those,  4,877  hours  (7.1%  of  operational  time)  represented  "miscellaneous 
use."  Of  that  "miscellaneous  use,"  2,498  hours  (3.6%  of  operational  time)  were  directly  concerned  with  the  space 
programs  of  the  United  States  and  the  Soviet  Union.  Lovell,  Out  of  the  Zenith:  Jodrell  Bank,  1 957-1 970  (New  York: 
Harper  &  Row,  1973) ,  p.  2. 

16.      Evans  9  September  1993. 


FICKLE  VENUS  35 


or  less  ready.  The  klystron  was  mounted  in  one  of  the  telescope  towers.  "It  was  a  royal 
pain,"  Evans  remembered,  "because  we  had  to  take  liquid  nitrogen  up  the  elevator  and 
then  a  vertical  ladder  to  get  to  this  darn  thing."  As  if  that  were  not  enough,  a  water  pump 
burned  up,  and  the  connectors  on  the  coaxial  cable  carrying  power  to  the  dish  burned 
out  every  ten  or  fifteen  minutes.  While  still  struggling  with  the  connector  problem,  Evans 
made  several  runs  on  Venus. 

Evans  was  a  junior  scientist,  having  just  received  his  Ph.D.  in  1957.  He  felt  he  was 
under  great  pressure  to  produce  positive  results.  Lovell  was  anxious  to  know  if  they  had 
found  an  echo;  the  Duke  of  Edinburgh  was  about  to  visit.  Evans  looked  at  his  data,  taken 
from  the  first  few  minutes  of  each  run,  when  he  thought  the  apparatus  was  working.  He 
had  what  looked  like  a  return,  but  it  could  have  been  noise.  Evans  decided,  "Well,  I  think 
we  have  an  echo."  The  Venus  detection  was  announced  in  the  31  October  1959  issue  of 
Nature.  The  Duke  of  Edinburgh  visited  Jodrell  Bank  on  11  November  1959;  he  received 
an  explanation  and  a  demonstration  of  the  technique,  using  the  Moon  as  a  target. 

Despite  the  patchwork  equipment,  the  50-kilowatt,  408-MHz  (74-cm)  radar  obtained 
a  total  of  58  and  three  quarters  hours  of  useful  operating  data,  before  Venus  passed 
beyond  its  range.  As  expected,  none  of  the  echoes  were  stronger  than  the  receiver  noise 
level;  integration  techniques  increased  the  strength  of  the  echoes.17  The  Jodrell  Bank  sig- 
nal processing  equipment  was  rather  limited  in  its  ability  to  search.  Without  accurate 
range  or  Doppler  correction  information,  Evans  had  to  make  assumptions;  he  chose  the 
Lincoln  Laboratory  1958  published  value.  Not  surprisingly,  the  value  Jodrell  Bank  derived 
for  the  astronomical  unit  agreed  with  that  determined  at  Lincoln  Laboratory.  The  Jodrell 
Bank  confirmation  of  the  Lincoln  Laboratory  results  placed  them  on  solid  scientific 
ground,  that  is,  until  Lincoln  Laboratory  repeated  the  experiment 

Fickle  Venus 

Bob  Price  and  his  fellow  Lincoln  Laboratory  investigators  were  highly  optimistic 
about  verifying  their  1958  results.  Millstone  now  had  a  peak  transmitter  power  of  500  kilo- 
watts, almost  twice  the  1958  level.  In  addition  to  using  a  higher  pulse  repetition  rate, 
which  improved  signal  detectability,  Price's  team  replaced  the  maser  with  a  parametric 
amplifier.  Like  the  maser,  the  parametric  amplifier  was  a  solid-state  microwave  amplifier. 
Parametric  amplifiers  were  simpler,  smaller,  cheaper,  and  lighter  than  masers,  and  they 
did  not  require  cryogenic  fluids  to  keep  them  cool.  Although  masers  generally  were  less 
noisy,  the  Millstone  parametric  amplifier  was,  Pettengill  and  Price  reported,  "gratifyingly 
stable  and  reliable  in  its  operation."18 

Over  a  four-week  period  around  the  inferior  conjunction  of  Venus,  the  Lincoln 
Laboratory  team  made  two  types  of  radar  observations.  On  66  runs,  they  recorded  the 
echoes  digitally  for  subsequent  computer  processing,  as  they  had  done  in  1958.  The  sec- 
ond approach,  used  on  117  runs,  involved  initial  analog  processing  in  a  series  of  elec- 
tronic circuits,  followed  by  digitization  and  integration  in  real  time  by  the  site's  comput- 
er. It  was  their  first  attempt  at  a  real-time  planetary  detection  by  radar.  Of  all  the  runs,  only 
one  displayed  a  peak  sufficiently  above  the  noise  level  to  be  statistically  significant.  When 
subjected  to  detailed  analysis,  though,  the  peak  turned  out  to  be  only  noise.  Price  and 


17.  Evans  9  September  1993;  Jodrell  Bank,  Moon  and  Venus  Radar  Passive  Satellite  Observations:  Technical 
(Final)  Report,   October  1958-December  1960,  AFCRL  Report  1129  (Macclesfield:  Nuffield  Radio  Astronomy 
Laboratories,  1961),  p.  22;  Evans  and  G.  N.  Taylor,  "Radio  Echo  Observations  of  Venus,"  Nature  184  (1959): 
1358-1359;  Lovell,  Out  of  the  Zenith,  p.  193.  The  noise  figure  was  4.6  db.  The  frequency  of  the  lunar  radar  was 
lowered  from  120  MHz  to  100  MHz,  when  it  was  found  to  interfere  with  operations  at  nearby  Manchester 
Airport. 

18.  Pettengill  and  Price,  p.  73. 


36  TO  SEE  THE  UNSEEN 


Pettengill  concluded  that  "none  of  the  individual  runs  show  strong  evidence  of  Venus 
echoes."19 

Jodrell  Bank  had  corroborated  the  1958  results;  yet  with  an  improved  radar,  Lincoln 
Laboratory  could  not  confirm  them.  The  disparity  between  the  results  was  perplexing — 
and  bothersome.  "It  is  difficult  to  explain  the  disparity  between  the  results  obtained  at  the 
two  Venus  conjunctions.  Our  current  feeling,"  wrote  Green  and  Pettengill,  "is  that  the 
planet's  reflectivity  may  be  highly  variable  with  time,  and  that  the  two  successes  in  1958 
were  observations  made  on  very  favorable  occasions."20 

At  the  Jet  Propulsion  Laboratory  (JPL),  the  Lincoln  Laboratory  and  Jodrell  Bank 
experiments  were  viewed  with  disbelief.  As  an  internal  report  stated  in  1961,  "It  is  not 
known  at  the  present  time  with  certainty  that  a  radio  signal  has  ever  been  reflected  from 
the  surface  of  Venus  and  successfully  detected."21  JPL  investigators  intended  to  obtain  the 
first  unambiguous  detection  of  radar  echoes  from  the  Venusian  surface. 

The  Jet  Propulsion  Laboratory 

JPL  began  modestly  in  Pasadena,  California,  in  1936  as  the  Guggenheim 
Aeronautical  Laboratory,  California  Institute  of  Technology  (GALCIT) ,  rocket  project, 
led  by  Hungarian-born  professor  Theodore  von  Karman  and  financed  by  Harry 
Guggenheim.  Starting  in  1940,  with  backing  from  the  Army  Air  Corps,  the  GALCIT  group 
turned  into  a  vital  rocket  research,  development,  and  testing  facility.  A  1944  contract 
signed  by  GALCIT,  the  Army  Air  Force,  and  the  California  Institute  of  Technology 
(Caltech)  transformed  it  into  a  large  permanent  laboratory  called  the  Jet  Propulsion 
Laboratory,  whose  major  responsibility  was  research,  development,  and  testing  of  missile 
technology,  including  the  country's  first  tactical  nuclear  missiles,  the  Corporal  and 
Sergeant,  for  the  Army. 

JPL  electronics  arose  out  of  the  need  for  missile  guidance  and  tracking  systems. 
William  Pickering,  a  Caltech  electrical  engineering  professor  with  a  Ph.D.  in  physics, 
became  the  director  of  JPL  in  1954  and  remained  in  that  position  until  1976.  His  special- 
ization was  electronics,  not  propulsion.  Under  Pickering's  aegis,  electronics  grew  in 
prominence  at  JPL  and  came  to  the  forefront  in  1958,  when  JPL  became  a  NASA  labora- 
tory and  started  work  on  a  worldwide,  civilian  satellite  communications  network  known 
today  as  the  Deep  Space  Network  (DSN)  ,22 

The  communications  network,  known  originally  as  the  Deep  Space  Instrumentation 
Facility  (DSIF),  was  the  home  of  planetary  radar  at  JPL.  The  three  leaders  of  the  Venus 
radar  experiment  were  engineers  involved  in  its  design,  Eberhardt  Rechtin,  Robertson 
Stevens,  and  Walter  K.  Victor.  Rechtin,  the  architect  of  the  DSIF,  had  a  Ph.D.  in  electrical 
engineering  from  Caltech.  He  also  was  an  inventor,  with  Richard  Jaffe  (also  at  JPL),  of 
CODORAC  (COded  DOppler,  Ranging,  And  Command),  a  radio  communication  system 


19.  Pettengill  and  Price,  p.  73;  Green  and  Pettengill,  "Exploring  the  Solar  System  by  Radar,"  Sky  and 
Telescope  20  (1960):  12-13;  Jelley,  pp.  30  and  35.  During  the  1959  Lincoln  Laboratory  Venus  experiment,  over 
150  runs  were  made,  yet  no  echoes  as  strong  as  those  of  1958  were  observed.  Overall  system  noise  temperature 
rose  from  170  Kelvins  in  1958  to  185  Kelvins  with  the  parametric  amplifier.  For  a  discussion  of  parametric  ampli- 
fiers,  see   Karl  Heinz   Locherer,   Parametric  Electronics:  An  Introduction  (New  York:   Springer-Verlag,   1981), 
pp.  276-286. 

20.  Green  and  Pettengill,  p.  13. 

21.  JPL,  Research  Summary  No.  36-7,  Volume  1,  for  the  period  December  1,  1960  to  February  1,  1961  (Pasadena: 
JPL,  1961),  pp.  68  and  70. 

22.  "Jet"  was  a  broader  term  than  rocket  and  avoided  any  stigma  still  attached  to  that  word.  Clayton  R. 
Koppes,yPL  and  the  American  Space  Program:  A  History  of  the  Jet  Propulsion  Laboratory  (New  Haven:  Yale  University 
Press,  1982),  pp.  ix,  4-5,  10-17,  20,  38,  45  and  65. 


FICKLE  VENUS 


37 


that  detected  and  tracked  narrow  band  signals  in  the  presence  of  wideband  noise. 
CODORAC,  whose  electronics  in  many  ways  resembled  Lincoln  Laboratory's  NOMAC, 
became  the  basis  for  much  of  the  DSIF's  electronics.  Bob  Stevens  had  an  M.S.  in  electri- 
cal engineering  from  the  University  of  California  at  Berkeley,  and  Walt  Victor,  who  assist- 
ed Rechtin  in  developing  CODORAC,  had  a  B.S.  in  mechanical  engineering  from  the 
University  of  Texas. 

JPL  located  its  share  of  the  DSIF  antennas  in  the  Mojave  Desert,  about  160  kilometers 
from  JPL,  on  the  Fort  Irwin  firing  range  near  Goldstone  Dry  Lake,  where  GALCIT  earlier 
had  tested  Army  rockets.23  The  two  antennas  on  which  JPL  investigators  performed  their 
Venus  experiment  in  1961  were  artifacts  of  the  funding  and  research  agendas  of  both  the 
military  and  NASA.  The  first  was  a  26-meter-diameter  (85-feet-diameter)  dish  named  the 
HA-DEC  antenna,  because  its  axes  were  arranged  to  measure  angles  in  terms  of  local  hour 
angle  (HA)  and  declination  (DEC).  JPL  installed  it  at  Goldstone  during  the  second  half  of 
1958  to  track  and  receive  telemetry  from  the  military's  Pioneer  probes.24 


Figure  6 

JPL  Goldstone  26-meter  HA-DEC  antenna  erected  in  late  1958  to  track  and  receive  telemetry  from  the  military's  Pioneer  probes. 
It  was  used  with  the  26-meter  AZ-EL  antenna  to  detect  radar  echoes  from  Venus  in  1961.  (Courtesy  of  Jet  Propulsion 
Laboratory,  photo  no.  333-5968 AC.) 


23.  Rechtin,  telephone  conversation  with  author,  13  September  1993;  Stevens  14  September  1993; 
Nicholas  A.  Renzetti,  ed.,  A  History  of  the  Deep  Space  Network  from  Inception  to  January  1,  1969,  vol.  1,  Technical 
Report  32-1533  (Pasadena:  JPL,  1  September  1971),  pp.  6-7  and  11;  William  R.  Corliss,  A  History  of  the  Deep  Space 
Network,  CR-151915  (Washington:  NASA,  1976),  pp.  3-4  and  16;  Craig  B.  Waff,  The  Road  to  the  Deep  Space 
Network,"  IEEE  Spectrum  (April  1993):  53;  Scholtz,  pp.  841-843;  additional  background  material  supplied  from 
oral  history  collection,  JPLA. 

24.  Dish  diameters  have  been  expressed  in  meters  only  recendy.  Initially,  they  were  measured  in  feet. 
For  the  sake  of  consistency,  diameters  are  given  in  both  feet  and  meters  diroughout  the  text.  Victor,  "General 
System  Description,"  p.  6  in  Victor,  Stevens,  and  Solomon  W.  Golomb,  eds.,  Radar  Exploration  of  Venus:  Goldstone 
Observatory  Report  for  March-May  1961,  Technical  Report  No.  32-132  (Pasadena:  JPL,  1961);  Corliss,  Deep  Space 
Network,  pp.  16-17  and  20-25. 


38 


TO  SEE  THE  UNSEEN 


JPL  erected  the  second  antenna  for  Project  Echo.  Echo,  a  large  balloon  in  Earth 
orbit,  tested  the  feasibility  of  long-range  satellite  communications.  As  such,  it  was  heir  to 
the  lunar-repeater  communication  tests  discussed  in  Chapter  One.  Originally  funded  by 
NASA's  predecessor,  the  National  Advisory  Committee  for  Aeronautics  (NACA) ,  and  the 
Defense  Department's  space  research  organization,  the  Advanced  Research  Projects 
Agency  (ARPA) ,  Project  Echo  became  a  JPL,  NASA,  and  Bell  Telephone  Laboratories 
undertaking  in  an  agreement  signed  in  January  1959. 

The  Echo  experiments  used  the  existing  HA-DEC  antenna  to  receive  as  part  of  a 
satellite  circuit  running  from  east  to  west.  The  west-to-east  circuit,  however,  required  the 
construction  of  an  antenna  capable  of  transmitting.  Therefore,  JPL  installed  a  second  26- 
meter-diameter  (85-feet-diameter)  dish  at  Goldstone  about  a  year  after  the  HA-DEC 
antenna  for  Project  Echo.  The  axes  of  the  second  antenna  measured  angles  in  terms  of 
azimuth  (AZ)  and  elevation  (EL) ;  hence,  it  was  referred  to  as  the  AZ-EL  antenna.25 


Figure  7 

Jet  Propulsion  Laboratory  Goldstone  26-meter  AZ-EL  antenna  built  far  Project  Echo  and  used  with  the  26-meter  HA-DEC 
antenna  to  detect  echoes  from  Venus  in  1961.  (Courtesy  of  Jet  Propulsion  Laboratory,  photo  no.  332-168.) 


25.  Victor,  "General  System  Description,"  in  Victor,  Stevens,  and  Golomb,  p.  6;  Corliss,  Deep  Space 
Network,  pp.  25-27;  Donald  C.  Elder,  III,  "Out  From  Behind  the  Eight  Ball:  Echo  I  and  the  Emergence  of  the 
American  Space  Program,  1957-1960,"  Ph.D.  diss.,  University  of  California  at  San  Diego,  1989,  passim.  For  a  his- 
tory of  ARPA,  see  Richard  J.  Barber  Associates,  Inc.,  The  Advanced  Research  Projects  Agency,  1958-1974 
(Washington,  D.C.:  National  Technical  Information  Service,  1975).  For  the  story  of  JPL  and  Project  Echo,  see 
Stevens  and  Victor,  eds.,  The  Goldstone  Station  Communications  and  Tracking  System  for  Project  Echo,  Technical  Report 
32-59  (Pasadena:  JPL,  1960);  Victor  and  Stevens,  "The  Role  of  the  Jet  Propulsion  Laboratory  in  Project  Echo," 
IRE  Transactions  on  Space  Electronics  and  Telemetry  SET-7  (1961):  20-28. 


FICKLE  VENUS  39 


By  August  1960,  as  Goldstone  prepared  to  participate  in  Project  Echo,  the  Lincoln 
Laboratory  and  Jodrell  Bank  Venus  experiments  already  had  taken  place.  Solomon 
Golomb,  assistant  chief  of  the  Communications  System  Research  Section  under  Walt 
Victor,  asked  his  employee,  Richard  Goldstein,  to  design  a  space  experiment  to  feed  the 
rivalry  between  Eb  Rechtin,  JPL  program  director  for  the  DSIF,  and  Al  Hibbs,  who  was  in 
charge  of  space  science  at  JPL.  Goldstein  suggested  the  Venus  radar  experiment.  Victor, 
JPL  project  engineer  for  the  Echo  program  and  recently  promoted  to  chief  of  the 
Communications  System  Research  Section,  and  Bob  Stevens,  head  of  the  Communica- 
tions Elements  Research  Section,  became  the  project  managers.26 

Rechtin,  Victor,  and  Stevens  organized  the  Venus  experiment  as  a  drill  of  the  DSIF 
and  its  technical  staff.  The  functional,  organizational,  and  budgetary  status  of  planetary 
radar  astronomy  as  a  test  of  the  DSIF  originated  in  their  conception  of  the  1961  Venus 
experiment  and  defined  planetary  radar  at  JPL  for  over  two  decades.  At  the  time,  the  lab- 
oratory was  preparing  for  the  first  Mariner  missions.  Consequently,  as  Rechtin  pointed 
out,  JPL  had  "a  particular  interest  in  an  accurate  determination  of  the  distance  to  Venus 
in  order  that  we  might  guide  our  space  probes  to  that  target."27 

The  NASA  Office  of  Space  Science  approved  the  Mariner  1  and  2  missions  in  July 
1960.  Goldstone  was  to  provide  communications  with  them.  The  task  would  be  more  chal- 
lenging than  communicating  with  a  Ranger  Moon  probe.  While  a  Ranger  mission 
required  three  days,  the  Mariner  missions  would  involve  months  of  round-the-clock,  high- 
level  technical  performance.  In  June  1960,  even  before  final  approval  of  the  Mariner 
probes,  Rechtin  proposed  the  radar  experiment  to  NASA,  emphasizing  not  its  scientific 
value,  but  the  "practical,  purely  project  point  of  view."28 

In  order  to  perform  the  Venus  experiment,  JPL  had  to  modify  the  Echo  equipment. 
Venus  was  a  much  farther  object  than  the  Earth-orbiting  Echo  balloon,  and  both  differed 
radically  as  radar  targets.  Victor  and  Stevens,  moreover,  wanted  to  avoid  long-term  inte- 
gration and  after-the-fact  data  reduction  and  analysis,  that  is,  the  Lincoln  Laboratory  and 
Jodrell  Bank  approach.  Instead,  JPL  attempted  a  real-time  radar  detection  of  Venus. 

The  JPL  antennas  were  unlike  those  of  Lincoln  Laboratory  and  Jodrell  Bank  in  many 
ways.  They  operated  in  tandem,  the  AZ-EL  transmitting  and  the  HA-DEC  receiving.  This 
bistatic  mode,  as  it  is  called,  offered  advantages  over  the  Millstone  and  Jodrell  Bank  mono- 
static  mode,  in  which  a  single  instrument  both  sent  and  received.  Monostatic  radars  have 
to  stop  transmitting  half  the  time  in  order  to  receive,  while  bistatic  radars  can  operate  con- 
tinuously, gathering  twice  the  data  in  the  same  period  of  time.  The  Goldstone  radars  also 
operated  at  a  higher  frequency  (S-band  v.  UHF)  and  sent  a  continuous  wave,  whereas  the 
Lincoln  Laboratory  and  Jodrell  Bank  radars  transmitted  discrete  pulses. 

JPL  also  boosted  the  transmitting  power  and  receiver  sensitivity  of  the  two  radars. 
The  normal  output  of  the  AZ-EL  transmitter  klystron  tube  was  10  kilowatts  at  2388  MHz 
(12.6  cm),  but  engineers  coaxed  a  nominal  average  power  output  of  13  kilowatts  out  of  it. 


26.  Golomb,  The  First  Touch  of  Venus,"  paper  presented  at  the  Symposium  Celebrating  the  Thirtieth 
Anniversary  of  Planetary  Radar  Astronomy,  Pasadena,  October  1991,  Renzetti  materials;  Goldstein  7  April  1993; 
Goldstein  14  September  1993;  Goldstein  19  September  1991;  Stevens  14  September  1993;  biographical  materi- 
al and  JPL  Press  Release,  23  May  1961,  3-15,  Historical  File,  JPLA. 

27.  Rechtin,  "Informal  Remarks  on  the  Venus  Radar  Experiment,"  in  Armin  J.  Deutsch  and  Wolfgang 
B.  Klemperer,  eds.,  Space  Age  Astronomy  (New  York:  Academic  Press,  1962),  p.  365;  Golomb,  "Introduction,"  in 
Victor,  Stevens,  and  Golomb,  pp.   1-2;  Rechtin,  telephone  conversation,   13  September   1993;  Goldstein 
19  September  1991. 

28.  Golomb,  "Introduction,"  p.  1;  JPL,  Research  Summary  No.  36-7,  p.  70;  Rechtin,  telephone  conversa- 
tion, 13  September  1993;  Waff,  "A  History  of  the  Deep  Space  Network,"  manuscript  furnished  to  author, 
ch.  6,  pp.  22  and  24.  Because  the  manuscript  is  not  paginated  sequentially,  both  chapter  and  page  references  are 
provided. 


40  TO  SEE  THE  UNSEEN 


Raising  the  sensitivity  of  the  HA-DEC  receiver  was  a  daunting  challenge;  the  total  receiv- 
er system  noise  temperature  on  Project  Echo  had  been  1570  K!29 

The  technical  solution  was  a  maser  and  a  parametric  amplifier  in  tandem  on  the  HA- 
DEC  antenna.  Charles  T.  Stelzried  and  Takoshi  Sato  created  a  2388-MHz  maser  specifi- 
cally for  the  Venus  radar  experiment  and  suitable  for  Goldstone's  tough  desert  ambient 
temperatures  (from  -12°  to  43°C;  10°  to  110°F)  and  climate  (rain,  dust,  and  snow).  The 
maser  and  2388-MHz  parametric  amplifier  combined  gave  an  overall  average  system  noise 
temperature  of  about  64  K  during  the  two  months  of  the  Venus  experiment,  considerably 
lower  than  the  best  achieved  at  Millstone  in  1958  (170  K).  As  Victor  and  Stevens  pro- 
claimed, 'This  is  believed  to  be  the  most  sensitive  operational  receiving  system  in  the 
world.  "30 

"No  Echo,  No  Thesis" 

Besides  testing  the  personnel  and  materiel  of  the  Goldstone  facility,  the  JPL  Venus 
experiment  also  was  the  doctoral  thesis  topic  of  two  employees  in  Walt  Victor's  section, 
Duane  Muhleman  and  Richard  Goldstein.  Muhleman  graduated  from  the  University  of 
Toledo  with  a  BS  in  physics  in  1953,  then  worked  two  years  at  the  NACA  Edwards  Air  Force 
Base  High-Speed  Flight  Station  as  an  aeronautical  research  engineer,  before  joining  JPL. 
As  part  of  his  duties  at  JPL,  Muhleman  tested  the  Venus  radar  system  and  its  components 
during  January,  February,  and  March  1961,  using  the  Moon  as  a  target.  For  the  Venus 
experiment,  Muhleman  contributed  an  instrument  to  measure  Doppler  spreading.31 

Goldstein  was  a  Caltech  graduate  student  in  electrical  engineering.  His  task  on  the 
Venus  radar  experiment  was  to  build  a  spectrum  measuring  instrument.  It  recorded  what 
the  spectrum  looked  like  during  reception  of  an  echo  and  what  it  looked  like  when  the 
receiver  saw  only  noise.  JPL  hired  his  brother,  Samuel  Goldstein,  a  JPL  alumnus  and  radio 
astronomer  at  Harvard  College  Observatory,  as  a  consultant  on  the  Venus  experiment; 
Samuel  also  helped  his  brother  with  some  of  the  radio  techniques. 

Dick  Goldstein  wanted  to  use  the  Venus  radar  experiment  as  his  thesis  topic  at 
Caltech,  but  his  advisor,  Hardy  Martel,  was  highly  skeptical.  The  inability  of  Lincoln 
Laboratory  to  detect  Venus  was  widely  known.  Although  he  thought  the  task  indisputably 
impossible,  Martel  finally  agreed  to  accept  the  topic,  but  with  a  firm  admonition:  "No 
echo,  no  thesis."32 


29.  Rechtin,  p.  366;  Victor,  "General  System  Description,"  pp.  6-7;  Stevens  and  Victor,  "Summary  and 
Conclusions,"  p.  95;  Victor  and  Stevens,  "The  1961  JPL  Venus  Radar  Experiment,"  IRE  Transactions  on  Space 
Electronics  and  Telemetry  SET-8  (1962):  85-90;  Charles  T.  Stelzried,  "System  Capability  and  Critical  Components: 
System  Temperature  Results,"  in  Victor,  Stevens,  and  Golomb,  pp.  28-29.  For  a  general  description  of  the  radar 
system,  see  M.  H.  Brockman,  Leonard  R.  Mailing,  and  H.  R.  Buchanan,  "Venus  Radar  Experiment,"  in  JPL, 
Research  Summary  No.  36-8,  Volume  1,  for  the  period  February  1,  1961  to  April  1,  1961  (Pasadena:  JPL,  1961), 
pp.  65-73;  Victor  and  Stevens,  "Exploration  of  Venus  by  Radar,"  Science  134  (1961):  46.  The  Jodrell  Bank  trans- 
mitter had  a  peak  power  of  50  kilowatts;  Millstone's  peak  power  was  265  kilowatts  in  1958  and  500  kilowatts  in 
1959.  However,  comparing  the  peak  power  ratings  of  pulse  and  continuous-wave  radars  is  the  electronic  equiva- 
lent of  comparing  apples  and  oranges.  One  must  compare  their  average  power  outputs. 

30.  Stevens  and  Victor,  "Summary  and  Conclusions,"  p.  95;  Sato,  "System  Capability  and  Critical 
Components:  Maser  Amplifier,"  in  Victor,  Stevens,  and  Golomb,  p.  17;  Stelzried,  "System  Capability  and  Critical 
Components:  System  Temperature  Results,"  pp.  28-29;  H.  R.  Buchanan,   "System  Capability  and  Critical 
Components:  Parametric  Amplifier,"  in  Victor,  Stevens,  and  Golomb,  pp.  22-25;  Walter  H.  Higa,  A  Maser  System 
for  Radar  Astronomy,  Technical  Report  32-103   (Pasadena:  JPL,   1961);  Higa,   "A  Maser  System  for  Radar 
Astronomy,"  in  K.  Endresen,  Low  Noise  Electronics  (New  York:  Pergamon  Press,  1962),  pp.  296-304. 

31.  Muhleman  8  April  1993;  Muhleman  19  May  1994;  Muhleman  27  May  1994;  Goldstein  19  September 
1991;  Stevens  14  September  1993;  Golomb,  "Introduction,"  p.  3;  Stevens,  "Additional  Experiments:  Resume,"  in 
Victor,  Stevens,  and  Golomb,  p.  70.  Muhleman 's  dissertation  was  "Radar  Investigations  of  Venus,"  Ph.D.  diss., 
Harvard  University,  1963. 

32.  Goldstein  7  April  1993;  Goldstein  19  September  1991;  Goldstein  14  September  1993. 


FICKLE  VENUS  41 


On  10  March  1961,  a  month  before  inferior  conjunction,  the  Goldstone  radars  were 
pointed  at  Venus.  The  first  signals  completed  the  round-trip  of  113  million  kilometers  in 
about  six  and  a  half  minutes.  During  the  68  seconds  of  electronic  signal  integration  time, 
1  of  7  recording  styluses  on  Goldstein's  instrument  deviated  significantly  from  its  zero 
level  and  remained  at  the  new  level. 

To  verify  that  the  deflection  came  from  Venus  and  was  not  leakage  from  the  trans- 
mitter or  an  instability  in  the  receiver,  the  transmitter  antenna  was  deliberately  allowed  to 
drift  off  target.  Six  and  a  half  minutes  later,  the  recording  stylus  on  Goldstein's  instrument 
returned  to  its  zero  setting.  The  experiment  was  immediately  repeated  with  the  same 
result.  JPL  had  achieved  the  first  real-time  detection  of  a  radar  signal  from  Venus.  And 
Dick  Goldstein  had  his  dissertation  topic.33 

On  16  March,  Eb  Rechtin  telexed  Paul  Green:  "HAVE  BEEN  OBTAINING  REAL 
TIME  RADAR  REFLECTED  SIGNALS  FROM  VENUS  SINCE  MARCH  10  USING  10  KW 
CW  AT  2388  MC  AT  A  SYSTEM  TEMPERATURE  OF  55  DEGREES."  The  following  day, 
Green,  John  Evans  (then  at  Lincoln  Laboratory),  Pettengill,  and  Price  telexed  back: 
"HEARTIEST  CONGRATULATIONS  ON  YOUR  SUCCESS  WITH  THE  FICKLE  LADY. 
MILLSTONE  IS  ON  WITH  THE  USUAL  MODE  OF  OPERATION  BUT  HAS  HAD  NO 
SUCH  LUCK  AS  YET.  PRESENT  PARAMETERS  2.4  MEGAWATTS  PEAK  FOR  2  MIL- 
LISECONDS EVERY  33  MILLISECONDS  190  DEGREES  KELVIN. "3* 

Following  the  initial  contact,  JPL  conducted  additional  radar  experiments  almost 
daily  from  10  March  to  10  May  1961,  collecting  238  hours  of  recorded  radar  data  about 
Venus.35  No  previous  Venus  radar  experiment,  nor  any  others  carried  out  in  1961, 
collected  as  many  hours  of  data  as  the  JPL  experiment. 

The  JPL  experiment  succeeded,  because  it  did  not  depend  on  knowing  the  range  to 
Venus,  specifically;  it  did  not  depend  on  prior  knowledge  of  the  precise  value  of  the  astro- 
nomical unit.  On  the  other  hand,  Lincoln  Laboratory,  as  well  as  Jodrell  Bank,  had  based 
its  experiment  on  an  assumed,  yet  commonly  accepted,  value  for  the  astronomical  unit, 
and,  consequently,  for  the  distance  between  Earth  and  Venus  during  inferior  conjunction. 

"We  Were  Wrong." 

The  results  obtained  by  Lincoln  and  other  laboratories  in  1961  agreed  with  those 
obtained  by  JPL.  That  agreement  led  Gordon  Pettengill  to  discern  the  error  of  the  1958 
Lincoln  Laboratory  observations.  "In  view  of  the  generally  excellent  agreement  among 
the  various  observations  made  at  several  wavelengths  [in  1961],"  Pettengill  and  his  col- 
leagues concluded,  "it  seems  likely  that  the  results  reported  from  observations  of  the  1958 
inferior  conjunction  are  in  error,  although  no  explanation  has  been  found."36 

Green  recalled:  "It  was  sort  of  devastating,  when  the  next  conjunction  of  Venus  came 
around,  and  we  learned  that  we  were  wrong.  We  had  the  wrong  value  of  the  astronomical 
unit.  It  wasn't  over  here;  it  was  way  over  there  someplace.  In  fact,  it  wasn't  even  easy  to  go 
back  and  look  at  the  original  data  and  conclude  that  it  was  really  over  there.  The  original 


33.  JPL  Press  Release,   23  May   1961,   3-15,   Historical  File,  JPLA;  Mailing  and  Golomb,    "Radar 
Measurements  of  the  Planet  Venus,"  Journal  of  the  British  Institution  of  Radio  Engineers  22  (1961):  298;  Victor  and 
Stevens,  The  1961  JPL  Venus  Radar  Experiment,"  IRE  Transactions  on  Space  Electronics  and  Telemetry  SET-8  ( 1962) : 
90-91.  Goldstein's  dissertation  was  "Radar  Exploration  of  Venus,"  Ph.D.  diss.,  California  Institute  of  Technology, 

34.  3-15,  Historical  File,  JPLA. 

35.  Victor  and  Stevens,  "1961  JPL  Venus  Radar  Experiment,"  p.  91. 

36.  Pettengill,  Briscoe,  Evans,  Gehrels,  Hyde,  Kraft,  Price,  and  Smith,  "A  Radar  Investigation  of  Venus," 
The  Astronomical  Journal  67  (1962):  186. 


42  TO  SEE  THE  UNSEEN 


data  just  had  turned  out  to  be  too  noisy.. ..It  was  a  chastening  experience  for  us."37  Price 
remembered  someone  entering  his  office  with  "a  rather  long  look  on  his  face"  and  saying, 
"Bob,  I  think  we've  been  found  to  be  wrong."  It  was  an  embarrassing  moment. 

Price  re-examined  the  Lincoln  Laboratory  1958  tapes.  "I  wanted  to  be  sure  that  we 
hadn't  detected  it.  I  really  mean  that.  I  wanted  to  make  sure  that  we  had  a  negative  result 
and  that  by  accident  we  didn't  have  two  wrongs  making  a  right,  that  is,  false  processing  of 
the  1958  data  led  to  a  false  result,  so  the  proper  processing  of  the  1958  data  would  agree 
with  JPL.  I  wanted  to  prove  that  that  was  not  the  case.  So  I  went  back  and  found  the  peaks, 
just  as  I  had  done  before.  I  made  a  meticulous  measurement  of  their  position,  which  is  the 
whole  thing  that  the  false  echo  hinged  on.  I  developed  with  magnetic  powder  over  and 
over  again  those  tapes,  and  I  inspected  them  until  my  eyes  were  sore.  I  reran  the  Fortran 
programs  and  checked  all  the  programs,  because  you  could  create  a  timing  error  in  the 
program." 

The  experience  reminded  Price  of  his  work  in  Australia.  Every  day,  his  group  had 
made  ink-pen  recordings  of  the  radio  sky  over  the  antenna,  usually  recording  only  ran- 
dom lines,  but  a  peak  appeared  on  two  successive  days.  Did  the  peak  mean  a  detection  of 
deuterium?  They  decided  that  it  was  a  fluke  and  published  their  negative  results.  "If  we 
had  behaved  the  same  way  at  Millstone,"  Price  reflected,  "we  might  have  saved  ourselves 
some  embarrassment.  But  that  is  hindsight."  The  two  Venus  pulses  arrived  2.2  millisec- 
onds apart.  "We  just  turned  our  back  on  it,"  Price  admitted,  "did  a  little  wishful  thinking, 
and  said,  'That's  the  same  pulse.'...!  just  pulled  them  together,  ignored  the  2.2-millisec- 
ond  difference,  and  sat  one  on  top  of  the  other."38 

Whatever  the  cause  of  the  1958  false  readings,  JPL  was  unquestionably  the  first  to 
detect  radar  waves  reflected  off  Venus.  The  literature  contains  two  earlier,  but  after-the- 
fact  detections.  Only  months  after  acknowledging  JPL's  priority,  Lincoln  Laboratory 
found  on  their  data  tapes  a  detection  of  Venus  on  6  March  1961,  a  few  days  prior  to  that 
of  JPL.  Later,  in  1963,  Lincoln  Laboratory  electrical  engineer  Bill  Smith  re-examined  the 
1959  data  tapes  and  found  that  an  echo  had  been  recorded  on  14  September  1959.39  Such 
after-the-fact  discoveries  are  not  uncommon  in  the  history  of  science,  and  radar 
astronomers  from  both  JPL  and  MIT  thirty  years  later  commemorated  JPL's  uncon tested 
priority  in  detecting  radar  waves  reflected  off  Venus. 

Once  JPL  unambiguously  detected  echoes  from  Venus,  the  key  question  planetary 
radar  astronomers  addressed  was  the  size  of  the  astronomical  unit.  In  order  to  determine 
more  precisely  the  Earth-to-Venus  distance,  JPL  ran  ranging  experiments  between  18 
April  and  5  May  1961.  In  the  July  1961  issue  of  Science,  Victor  and  Stevens  announced  a 
preliminary  value  for  the  astronomical  unit  of  149,599,000  kilometers  with  an  accuracy  of 
±  1500  kilometers.40  That  value  was  over  100,000  kilometers  larger  than  the  false  radar 
value  determined  by  Lincoln  Laboratory  in  1958  and  confirmed  by  Jodrell  Bank  in  1959, 
149,467,000  kilometers.  Values  obtained  from  preliminary  analyses  of  radar  data  at 
Lincoln  Laboratory  and  elsewhere  in  1961  agreed  closely  with  that  of  JPL  (Table  1). 

When  Lincoln  Laboratory  undertook  its  1961  Venus  radar  experiment,  Gordon 
Pettengill,  joined  by  John  Evans,  took  over  Bob  Price's  leadership  role.  Evans  had  left 
Jodrell  Bank  for  Lincoln  Laboratory  during  the  previous  summer,  after  being  courted  by 
the  National  Bureau  of  Standards  and  Stanford.  At  Jodrell  Bank,  Evans  had  had  one 


37.  Green  20  September  1993. 

38.  Price  27  September  1993. 

39.  Smith  29  September  1993;  Smith,  "Radar  Observations  of  Venus,  1961  and  1959,"  The  Astronomical 
Journal  68  (1963):  17;  Pettengill  et  al,  "A  Radar  Investigation  of  Venus,"  p.  183. 

40.  Rechtin,  p.  367;  Victor,  "General  System  Description,"  p.  7;  Victor  and  Stevens,  "1961  JPL  Venus 
Radar  Experiment,"  p.  88;  Victor  and  Stevens,  "Exploration  of  Venus  by  Radar,"  p.  46. 


FICKLE  VENUS 


43 


Table  1 

Radar  Values  for  the  Astronomical  Unit,  1961-1964 

Error  of 

Value  of 

Measurement 

Astronomical  Unit 

(in  kilometers) 

(in  kilometers) 

Optical  Values 

Spencer  Jones 

±17,000 

149,675,000 

Eugene  Rabe 

±10,000 

149,530,000 

1961  Conjunction 

Jet  Propulsion  Laboratory 

July  1961  (1) 

±1,500 

149,599,000 

August  1961  (2) 

±500 

149,598,500 

Muhleman  (3) 

±250 

149,598,845 

Lincoln  Laboratory 

May  1961  (4) 

±1,500 

149,597,700 

Corrected  value  (5) 

±400 

149,597,850 

Jodrell  Bank  (6) 

±5,000 

149,601,000 

RCA/Flower  and  Cook  Observatory  (7) 

±200 

149,596,000 

Soviet  Union 

Pravda  value  (8) 

±130,OOOP 

149,457,000 

November  1961  (9) 

±3,300 

149,598,000 

Revised  Value  (10) 

±2,000 

149,599,300 

Space  Technology  Laboratories  (11) 

±13,700 

149,544,360 

1962  Conjunction 

Jodrell  Bank  (12) 

±900 

149,596,600 

Soviet  Union  (13) 

±270 

149,597,900 

Jet  Propulsion  Laboratory  Muhleman  (14) 

±670 

149,598,900 

1964  Conjunction 

Lincoln  Laboratory  (15) 

±100 

149,598,000 

Jet  Propulsion  Laboratory  (16) 

±100 

149,598,000 

Soviet  Union  (17) 

±400 

149,598,000 

IAU  Value 

149,600,000 

Sources 

1.        W.K.  Victor  and   R.   Stevens,   "Exploration   of  Venus  by  Radar,"   Science  134   (July   1961):   46-48. 

2.        D.O.  Muhleman,  D.B.  Holdridge,  and  N.  Block,  "Determination  of  the  Astronomical  Unit  from  Velocity,  Ranee, 
and  Integrated  Velocity  Data,  and  the  Venus-Earth  Ephemeris,"  pp.  83-92  in  W.K.  Victor,  R.  Stevens,  and  S.W.  Golomb,  eds., 

Raiitir  Exploration  of  Venus:  Goldstar*  Observatory  Report  jar  March-May  1961,  Technical  Report  32-132  (Pasadena:  Jet  Propulsion 

Laboratory,  1  August  1961). 

3.       D.O.  Muhleman,  D.B.  Holdridge,  and  N.  Block,  The  Astronomical  Unit  Determined  by  Radar  Reflections  from 
Venus,"  The  Astronomical  Joumal67  (1962):  191-203. 

4.       Staff,  Millstone  Radar  Observatory.  Lincoln  Laboratory,  'The  Scale  of  the  Solar  System,"  Nature  190  (13  May  1961): 

5.       G.H.  Pettengill,  H.W.  Briscoe,  J.V.  Evans,  E.  Gehrels,  G.M.  Hyde,  L.G.  Kraft,  R.  Price,  and  W.B.  Smith,  "A  Radar 

Investigation  of  Venus,"  The  Astronomical  foumal&l  (1962):  181-190. 

6.       J.H.  Thomson,  J.E.B.  Ponsonby,  G.N.  Taylor,  and  R.S.  Roger,  "A  New  Determination  of  the  Solar  Parallax  by  Means 
of  Radar  Echoes  from  Venus,"  Mi/urel90  (1961):  519-520. 

7.       I.  Maron,  G.  Luchak,  and  W.  Bliustein,  "Radar  Observation  of  Venus,"  Science  134  (1961):  1419-1421. 

8.        VA.  Kotelnikov,  "Radar  Contact  with  Venus,"  Journal  of  the  British  Institution  of  Radio  Engineers  22  (  1961  )  :  293-295. 
9.        VA.  Kotelnikov,  V.M.  Dubrovin,  VA.  Morozov,  G.M.  Petrov,  O.N.  Rzhiga,  Z.G.  Trunova,  and  A.M.  Shakhovoskoy, 

"Results  of  Radar  Contact  with  Venus  in  1961,"  Radio  Engineering  and  Electronics  Physics  11  (November  1961):  1722-1733. 
10.     Vj\.  Kotelnikov,  B  A.  Dubmskiy,  M.D.  Kislik,  and  D.M.  Tsvetkov,  "Refinement  of  the  Astronomical  Unit  on  the  Basis 
of  the   Results   of  Radar  Observations  of  the   Planet  Venus   in    1961,"   NASA  TT   F-8532,   October    1963. 

11.     J.B.  McGuire,  E.R.  Spangler,  and  L.  Wong,  "The  Size  of  the  Solar  System,"  Scientific  American  vol.  204,  no.  4  (1961  ): 

64-72. 

12.     J.E.B.  Ponsonby,  I.  H.  Thomson,  and  K.S.  Imrie,  "Radar  Observations  of  Venus  and  a  Determination  of  the 

Astronomical  Unit,"  Monthly  Notices  of  the  Royal  Astronomical  Society  128  (1964):  1-17. 
13.      V.A.  Kotelnikov,  V.M.  Dubrovin,  VA.  Dubinskii,  M.D.  Kislik,  B.I.  Kusnctsov,  I.V.  Lishin.  VA.  Morosov,  G.M.  Petrov, 

O.N.  Rzhiga,  GA.  Sytsko,  and  A.M.  Shakhovskoi,  "Radar  Observations  of  Venus  in  the  Soviet  Union  in  1962,"  Soviet  Physia- 

DoUady  8  (1964):  642-645. 

14.      D.O.  Muhleman,  Relationship  Between  the  system  of  Astrcmomical  Constants  and  the  Radar  determinations  of  the  Astronomical 
Unit,  Technical  Report  32-477  (Pasadena:  Jet  Propulsion  Laboratory,  15  January  1964). 

15.     J.C.  Pecker,  ed..  Proceedings  of  the  Twelfth  General  Assembly  (New  York:  Academic  Press,  1966),  p.  602. 

16.     J.C.  Pecker,  ed.,  Proceedings  of  the  Twelfth  General  Assembly  (New  York:  Academic  Press,  1966),  p.  603. 

17.      VA.  Kotelnikov,  Yu.  N.  Alcksandrov,  L.V.  Apraksin,  V.M.  Dubrovin,  M.D.  Kislik,  B.I.  Kuznclsov,  G.M.  Petrov.  O.N. 

Rzhiga,  A.V.  Franlsesson.  and  A.M.  Shakhovskoi,  "Radar  Observations  of  Venus  in  the  Soviet  Union  in  1964,"  Soviet  Phyaa- 

DoUady  10  (1966):  578-580. 

44  TO  SEE  THE  UNSEEN 


technical  assistant;  but  at  Lincoln  Laboratory,  as  Bernard  Lovell  pointed  out,  he  had  "an 
army  of  engineers  and  technicians  together  with  a  transmitter  vastly  superior  to  the  one 
at  Jodrell  Bank." 

Evans'  departure  from  Jodrell  Bank  could  not  have  come  at  a  worse  time,  hi  the 
opinion  of  Lovell.  "For  me  it  was  the  beginning  of  a  distressing  series  of  losses  of  the  bril- 
liant young  men  who  had  been  with  me  throughout  the  crisis  of  the  telescope  and  whose 
devotion  and  skill  had  been  a  determining  factor  in  the  immediate  success  of  the  instru- 
ment. But  who  could  expect  a  young  man  to  resist  a  lavish  red  carpet  reception  and  an 
offer  of  a  salary  many  times  greater  than  any  sum  which  we  could  possibly  offer  him?"41 

During  the  1961  Venus  experiment,  the  Millstone  Hill  radar  ran  at  peak  transmitting 
power,  2.5  megawatts.  The  increased  transmitter  power  overcame  the  higher  overall 
receiver  noise  temperature  (240  K)  to  make  the  telescope  a  far  more  capable  instrument. 
Pettengill  and  his  colleagues  aimed  their  radar  at  Venus  on  6  March  1961,  again  using  a 
technique  to  provide  real-time  detection.  No  echoes  appeared  until  24  March. 
Preliminary  analysis  yielded  a  value  for  the  astronomical  unit  of  149,597,700  ±  1,500  kilo- 
meters in  May  1961.42  That  agreed  closely  with  JPL's  preliminary  value,  149,599,000  kilo- 
meters. Despite  considerable  obstacles,  and  chastened  by  their  1959  false  detection, 
Jodrell  Bank  investigators  also  found  a  value  for  the  astronomical  unit  that  agreed  with  the 
JPL  value. 

In  1959,  John  H.  Thomson  took  over  the  planetary  radar  program,  and  in  the 
autumn  of  1960,  Lovell  added  John  E.  B.  Ponsonby,  who  had  come  to  Jodrell  Bank  to  work 
on  a  doctorate  after  graduating  in  electrical  engineering  from  Imperial  College,  London. 
Ponsonby  had  experience  in  meteor  radar  through  his  high  school  teacher  and  one-time 
member  of  the  Jodrell  Bank  group,  Ian  C.  Browne.43 

Working  from  notes  and  memoranda  left  by  Evans,  the  new  team,  which  included  G. 
N.  Taylor  and  R.  S.  Roger,  put  together  a  radar  system  that  "yielded  a  clear-cut  and  deci- 
sive answer  after  only  a  few  5  minute  integration  periods."44  The  first  thing  they  did,  how- 
ever, was  to  abandon  the  atrocious  klystron.  With  most  of  the  problems  that  plagued  the 
1959  experiment  overcome,  with  a  more  sensitive  receiver,  and  with  peak  power  output 
boosted  from  50  to  60  kilowatts,  the  76-meter  (250-ft)  Jodrell  Bank  telescope  detected 
Venus  beginning  8  April  1961,  a  few  weeks  after  both  JPL  and  Lincoln  Laboratory  had 
started  their  experiments,  and  ending  25  April  1961. 

Jodrell  Bank  calculated  a  value  for  the  astronomical  unit,  149,600,000  ±  5000  kilo- 
meters,45 close  to  the  preliminary  values  of  JPL  (149,599,000  kilometers)  and  Lincoln 


41 .  Lovell,  Out  of  the  Zenith,  pp.  192  and  195;  Evans  9  September  1993;  Green  20  September  1993;  Smith 
29  September  1993;  Pettengill  28  September  1993. 

42.  The  Staff,  Millstone  Radar  Observatory,  Lincoln  Laboratory,  The  Scale  of  the  Solar  System,"  Nature 
190  (1961):  592;  Pettengill  et  al,  "A  Radar  Investigation  of  Venus,"  pp.  182-183;  Pettengill  and  Price,  p.  73; 
Pettengill,  "Radar  Measurements  of  Venus,"  in  Wolfgang  Priester,  ed.,  Space  Research  III,  Proceedings  of  the  Third 
International  Space  Science  Symposium  (New  York:  Interscience  Publishers  Division,  John  Wiley  and  Sons,  1963) ,  p. 
874;  Overhage  to  Wilson,  22  May  1961,  1/24/AC  134,  MITA. 

43.  Ponsonby  1 1  January  1994;  I.  C.  Browne  and  T.  R.  Kaiser,  The  Radio  Echo  from  the  Head  of  Meteor 
Trails, "  Journal  of  Atmospheric  and  Terrestrial  Physics  4  (1953):  1—4. 

44.  Evans  9  September  1993;  Lovell,  Out  of  the  Zenith,  pp.  198-199;  Thomson,  Ponsonby,  Taylor,  and 
Roger,  "A  New  Determination  of  the  Solar  Parallax  by  Means  of  Radar  Echoes  from  Venus,"  Nature  190  (1961): 
519-520.  The  Jodrell  Bank  experiment  was  funded  by  Air  Force  contract  no.  AF61(052)-172.  John  Evans,  then 
of  Lincoln  Laboratory,  privately  had  communicated  the  laboratory's  results  to  Thomson  at  Jodrell  Bank. 

45.  I  have  calculated  this  value  from  the  information  provided  in  Thomson,  Ponsonby,  Taylor,  and 
Roger,  pp.  519-520.  While  the  authors  concern  themselves  with  the  solar  parallax,  they  also  provide  a  figure  for 
the  light-time  of  the  astronomical  unit,  499,011  ±0.017  seconds,  which  represents  the  time  taken  by  radar  waves 
to  travel  the  distance  of  one  astronomical  unit,  and  another  for  the  speed  of  light,  299,792.5  kilometers  per  sec- 
ond, which  is  the  same  as  the  speed  of  electromagnetic  waves.  By  multiplying  the  two  figures,  I  obtained  a  prod- 
uct of  149,599,750  kilometers. 

The  first  published  value  of  the  astronomical  unit  I  have  found  was  in  the  comments  given  by  Thomson 
following  a  presentation  by  Mailing  and  Golomb  at  a  convention  in  Oxford  that  took  place  5-8  July  1961.  The 
date  of  publication  was  October  1961.  Mailing  and  Golomb,  p.  302. 


FICKLE  VENUS  45 


Laboratory  (149,597,700  kilometers),  but  with  a  far  greater  possible  error  of  measure- 
ment. Similar  results  came  from  an  unexpected  source.  RCA's  Missile  and  Surface  Radar 
Division  in  Moorestown,  New  Jersey,  carried  out  its  first  and  last  planetary  radar  experi- 
ment in  1961.  The  Division  performed  radar  research  for  the  Army  Signal  Corps  and  the 
Navy,  and  in  1960,  the  Division  performed  solar  radio  experiments  using  a  missile-track- 
ing radar.  On  their  Venus  radar  experiment,  RCA  investigators  collaborated  with  the 
Flower  and  Cook  Observatory  of  the  University  of  Pennsylvania.  Between  12  March  and  8 
April  1961,  RCA  tracked  Venus  with  a  BMEWS  experimental  radar  in  order  to  measure 
the  astronomical  unit.  In  over  six  hours  of  transmitted  signals,  they  found  only  four  peaks 
from  which  they  calculated  a  value  for  the  astronomical  unit  of  149,596,000  ±  200  kilo- 
meters,46 only  3,000  kilometers  less  than  the  JPL  value.  Not  all  Venus  radar  results  agreed 
with  those  of  JPL,  however. 

In  the  Soviet  Union,  planetary  radar  was  fundamental  to  the  space  program.  One  of 
the  main  objectives  of  the  Crimean  Venus  experiment  was  to  calculate  a  more  precise 
value  for  the  astronomical  unit  for  use  in  launching  planetary  probes.  The  calculation  of 
the  orbit  of  the  Mars-1  probe,  in  November  1962,  utilized  a  radar-based  value  for  the  astro- 
nomical unit.  The  Institute  of  Radio  Engineering  and  Electronics  (IREE)  of  the  U.S.S.R. 
Academy  of  Sciences,  in  association  with  other  unnamed  (but  presumably  military  and 
intelligence)  organizations  and  under  the  direction  of  Vladimir  A.  Kotelnikov,  of  the 
Soviet  Academy  of  Sciences,  designed  and  built  planetary  radar  equipment  that  was 
installed  at  the  Long-Distance  Space  Communication  Center,  located  near  Yevpatoriya  in 
the  Crimea.  The  IREE  installation  had  nothing  to  do  with  the  radar  work  carried  out  in 
the  Soviet  Union  in  1946  on  meteors  or  between  1954  and  1957  on  the  Moon. 

The  IREE  planetary  radar  was  a  monostatic  pulse  700-MHz  (43-cm)  system.  For  the 
receiver,  the  IREE  expressly  designed  both  a  parametric  and  a  paramagnetic  amplifier, 
another  form  of  solid-state,  low-noise  microwave  amplifier.  The  noise  temperature  of  the 
entire  receiver  (without  antenna)  was  claimed  to  be  20  ±  10  K.  The  antenna  was  an  array 
of  eight  16-meter  dishes,  unlike  any  design  ever  used  in  the  United  States  or  Britain  for 
planetary  radar  astronomy.47 

Kotelnikov  and  his  colleagues  observed  Venus  between  18  and  26  April  1961.  Their 
preliminary  analysis  of  the  data  yielded  an  estimate  of  the  astronomical  unit,  149,457,000 
kilometers,  which  appeared  in  the  newspapers  Pravda  and  Izvestiia  on  12  May  1961.  Over 
100,000  kilometers  less  than  the  JPL  and  other  values,  the  Soviet  astronomical  unit  mea- 
surement was  so  incredibly  incongruous,  that  Solomon  Golomb  told  a  conference  of 
astronomers,  "we  should  congratulate  our  Russian  colleagues  on  the  discovery  of  a  new 


46.  W.  O.  Mehuron,  "Passive  Radar  Measurements  at  C-Band  using  the  Sun  as  a  Noise  Source,"  The 
Microwave  Journal  5  (April,  1962):  87-94;  David  K.  Barton,  "The  Future  of  Pulse  Radar  for  Missile  and  Space 
Range  Instrumentation,"  IRE  Transactions  on  Military  Electronics  MIL-5,  no.  4  (October,  1961):  330-351;  Irving 
Maron,  George  Luchak,  and  William  Blitzstein,  "Radar  Observation  of  Venus,"  Science  134  (1961):  1419-1420. 

47.  B.  I.  Kuznetsov  and  I.  V.  Lishin,  "Radar  Investigations  of  the  Solar  System  Planets,"  in  Air  Force 
Systems  Command,  Radio  Seventy  Years  (Wright-Patterson  AFB,  Ohio:  Air  Force  Systems  Command,  1967), 
pp.  187-188,  190  and  201;  Vladimir  A.  Kotelnikov,  "Radar  Contact  with  Venus,  "Journal  of  the  British  Institution  of 
Radio  Engineers  22  (1961):  293;  Kotelnikov,  L.  V.  Apraksin,  V.  O.  Voytov,  M.  G.  Golubtsov,  V.  M.  Dubrovin,  N.  M. 
Zaytsev,  E.  B.  Korenberg,  V.  P.  Minashin,  V.  A.  Morozov,  N.  I.  Nikitskiy,  G.  M.  Petrov,  O.  N.  Rzhiga,  and  A.  M. 
Shakhovskoy,  "Radar  System  Employed  during  Radar  Contact  with  Venus  in   1961,"  Rndio  Engineering  and 
Electronic  Physics  II  (1962):  1715-1716.  For  abrief  history  of  the  IREE,  see  Y.V.  Gulyaev,  "40  Years  of  the  Institute 
of  Radioengineering  and  Electronics  of  the  Russian  Academy  of  Sciences,"  Radiotekhnika  Elektronika  vol.  38,  no. 
10  (October  1993):  1729-1733.  Soviet  investigators  performed  radar  studies  of  meteors  in  1946  and  of  the  Moon 
in  1954-1957,  according  to  A.  E.  Solomonovich,  "The  First  Steps  of  Soviet  Radio  Astronomy,"  pp.  284-285  in 
Sullivan.  Although  radar  astronomers  recently  have  used  the  arrayed  dishes  of  the  Very  Large  Array  in  bistatic 
experiments,  dish  arrays  have  not  been  used  as  transmitting  antennas. 


46  TO  SEE  THE  UNSEEN 


planet.  It  surely  wasn't  Venus!"  Retrospectively,  Kotelnikov  explained  that  "random  real- 
izations of  noise  were  taken  for  reflected  signals."48 

The  cause  of  the  Soviet  error  might  have  been  rooted  in  Cold  War  competition, 
which  placed  Soviet  scientists  under  great  pressure  to  produce  results  quickly  for  political 
reasons.  The  Pravda  and  hvestiia  announcements  appeared  on  12  May  1961,  six  days  after 
the  Jodrell  Bank,  but  before  the  Lincoln  Laboratory,  announcements.  If  published 
sources  had  guided  Kotelnikov  and  his  colleagues,  they  would  have  been  the  erroneous 
Lincoln  Laboratory  and  Jodrell  Bank  results  of  1958  and  1959,  with  which  the  hvestiia 
value  agreed  closely  (within  10,000  kilometers). 

The  Cold  War  prevented  communication  and  cooperation  among  planetary  radar 
investigators.  The  Space  Race  in  1961  was  still  an  extension  of  the  Cold  War;  informal 
communications  did  not  exist.  Lincoln  Laboratory  did  secret  military  research;  JPL  was  a 
sensitive  space  research  center  with  connections  to  ARPA,  a  military  research  agency. 
Jodrell  Bank  did  not  yet  have  ties  with  their  Soviet  counterparts.  While  Lincoln 
Laboratory,  JPL,  and  Jodrell  Bank  personnel  exchanged  data,  such  informal  links  with 
Soviet  scientists  did  not  and  could  not  exist. 

Kotelnikov  and  his  associates  at  the  IREE,  after  realizing  their  error,  turned  their 
attention  to  a  complete  analysis  of  the  raw  radar  data  recorded  on  magnetic  tape  with  the 
help  of  a  special  analyzer.  Their  new  value,  149,598,000  ±  3300  kilometers,  agreed  closely 
with  those  of  the  United  States  and  Britain.49  Although  the  Soviet  and  British  errors  of 
measurement  were  greater  than  those  of  the  American  laboratories,  they  were  far  less 
than  the  values  obtained  by  optical  methods.  The  accuracy  of  the  radar  over  the  optical 
method  and  the  general  agreement  among  the  preliminary  results  obtained  in  the  United 
States,  Britain,  and  the  Soviet  Union  were  the  basis  for  a  re-evaluation  of  the  astronomi- 
cal unit  by  the  International  Astronomical  Union  (IAU) . 

Redefining  the  Astronomical  Unit 

The  re-evaluation  of  the  astronomical  unit  was  part  of  a  general  movement  within 
the  IAU  to  reform  the  entire  system  of  astronomical  constants  conventionally  used  to  com- 
pute ephemerides.  On  21  August  1961,  shortly  after  JPL,  Lincoln  Laboratory,  and  Jodrell 
Bank  announced  their  first  estimations  of  the  astronomical  unit,  the  IAU  executive  com- 
mittee decided  to  organize  a  symposium  on  the  system  of  astronomical  constants.  That  sys- 
tem rested  upon  observations  made  in  the  nineteenth  century  and  values  adopted  at 
international  conferences  held  in  Paris  in  1896  and  191 1.50 

By  1950,  two  competing  optical  methods  provided  more  accurate  values  for  the  astro- 
nomical unit.  Harold  Spencer  Jones,  Astronomer  Royal  of  Great  Britain  from  1933  to 
1955,  used  a  trigonometric  approach  based  on  the  triangulation  of  Eros.  The  orbit  of  the 


48.  Kotelnikov  et  al,  "Radar  System,"  pp.  1715  and  1721;  Kotelnikov,  "Radar  Contact,"  p.  294;  Mailing 
and  Golomb,  p.  300;  Kotelnikov,  "Radar  Observations  of  the  Planet  Venus  in  the  Soviet  Union  in  April,  1961," 
typed  manuscript,  27  February  1963,  anonymous  translation  of  a  technical  report  of  the  Soviet  Institute  of  Radio 
Engineering  and  Electronics,  DTIC  report  number  AD-401137,  pp.  41-42,  Renzetti  materials.  The  Soviet  publi- 
cation venue  and  aberrant  astronomical  unit  value  raise  serious  doubts  about  the  veracity  of  their  announce- 
ment. 

49.  Kotelnikov  et  al,  "Radar  System,"  p.   1721;  Kuznetsov  and  Lishin,  p.   188;  Kotelnikov,   "Radar 
Observations,"  p.  2;  Kotelnikov,  Dubrovin,  Morozov,  Petrov,  Rzhiga,  Z.  G.  Trunova,  and  Shakhovoskoy,  "Results 
of  Radar  Contact  with  Venus  in  1961,"  Radio  Engineering  and  Electronics  Physics  11  (1962):  1722  and  1725.  For  a 
discussion  of  the  integration  technique,  see  V.  I.  Bunimovich  and  Morozov,  "Small-Signal  Reception  by  the 
Method  of  Binary  Integration,"  ibid.,  pp.  1734-1740. 

50.  Jean  Kovalevsky,  ed.,  The  System  of  Astronomical  Constants  (Paris:  Gauthier-Villars  and  Cie.,  1965),  p. 
1;  Walter  Fricke,  "Arguments  in  Favor  of  the  Revision  of  the  Conventional  System  of  Astronomical  Constants," 
in  J.  C.  Pecker,  ed.,  Proceedings  of  the  Twelfth  General  Assembly  (New  York:  Academic  Press,  1966),  p.  604. 


FICKLE  VENUS  47 


asteroid,  discovered  in  1898  by  Berlin  astronomer  Gustav  Witt,  approaches  Earth  at  regu- 
lar intervals.  As  president  of  the  IAU  Solar  Parallax  Commission,  Spencer  Jones  oversaw 
a  worldwide  operation  to  record  photographic  observations  of  Eros  during  its  closest 
approach  to  Earth  in  1930  and  1931.  Through  a  complicated  analysis  of  nearly  3,000  pho- 
tographs, Spencer  Jones  estimated  the  astronomical  unit  to  be  149,675,000  ±  17,000  kilo- 
meters. Eugene  Rabe,  an  astronomer  at  the  Cincinnati  Observatory,  applied  the  so-called 
dynamic  method  to  observations  of  Eros  between  1926  and  1945.  He  took  into  account 
the  gravitational  effects  of  the  Earth,  Mars,  Mercury,  and  Venus  on  the  orbit  of  Eros,  and 
arrived  at  a  value  of  149,530,000  ±  10,000  kilometers.51 

In  addition,  investigators  at  the  Space  Technology  Laboratories  (STL),  a  wholly- 
owned  subsidiary  of  Ramo-Wooldridge  (later  TRW) ,  computed  a  value  from  data  acquired 
during  the  Pioneer  5  mission.  In  figuring  the  probe's  trajectory,  STL  chose  Rabe's  value 
over  that  of  Lincoln  Laboratory  in  1958.  Not  surprisingly,  STL  found  a  value  for  the  astro- 
nomical unit,  149,544,360  ±  13,700  kilometers,  in  agreement  with  Rabe,  but  with  a  greater 
error  of  measurement.  The  STL  value  hardly  challenged  the  more  accurate  ground-based 
radar  measurements.  Its  "published  accuracy,"  Walter  Fricke,  astronomer  and  professor  at 
the  Heidelberg  Astronomisches  Rechen-Institut,  judged,  "does  not  yet  indicate  any  advan- 
tage over  the  traditional  methods."52  The  Pioneer  5  value  did  not  play  any  part  in  the 
lAU's  revision  of  the  astronomical  unit. 

The  organizing  committee  of  the  IAU  symposium  on  astronomical  constants 
brought  together  astronomers  from  the  United  States  and  Europe  who  were  responsible 
for  drawing  up  the  ephemerides.  COSPAR  (the  Committee  on  Space  Research)  named  an 
ad  hoc  committee  to  participate  in  the  symposium,  and  additional  astronomers  from  the 
United  States,  Britain,  France,  West  Germany,  Portugal,  the  Soviet  Union,  and  South 
Africa  took  part.  The  members  of  the  organizing  committee  included  Eb  Rechtin,  theJPL 
manager  of  the  DSIF;  Dirk  Brouwer,  director  of  the  Yale  Observatory;  and  Gerald  M. 
Clemence,  scientific  director  of  the  U.S.  Naval  Observatory  in  Washington.  Both  Brouwer 
and  Clemence  had  helped  JPL  with  the  Venus  radar  experiment  ephemerides.  Among  the 
additional  astronomers  participating  in  organizing  committee  activities  were  two  radar 
astronomers,  Dewey  Muhleman  and  Irwin  I.  Shapiro.53 

Soon  after  the  1961  Venus  experiment,  Muhleman  left  JPL  for  the  Harvard 
Astronomy  Department.  There,  under  Fred  Whipple,  A.  Edward  Lilley,  and  William  Liller, 
he  completed  a  doctoral  dissertation  based  on  Venus  radar  data  collected  at  Goldstone  in 
June  1963.  After  returning  to  JPL,  Muhleman  took  a  teaching  position  in  the  Cornell 
Astronomy  Department  in  1965.  Shapiro  had  a  Ph.D.  in  physics  from  Harvard  and  had 
worked  on  the  detection  of  objects  with  radar  in  a  clutter  environment  and  on  ballistic 
missile  defense  systems,  before  joining  the  team  conducting  radar  experiments  on  Venus 
as  the  "guru"  who  calculated  the  ephemerides  for  Lincoln  Laboratory  planetary  radar 
research.54 


51.  Spencer  Jones,  The  Solar  Parallax  and  the  Mass  of  the  Moon  from  Observations  of  Eros  at  the 
Opposition  of  1931,"  Memoirs  of  the  Royal  Astronomical  Society  66  (1938-1941):  11-66;  Rabe,  "Derivation  of 
Fundamental  Astronomical  Constants  from  the  Observations  of  Eros  during  1926-1945,"  The  Astronomical  Journal 
55  (1950):  112-126;  Fricke,  "Inaugural  Address  Delivered  at  the  lAU-Symposium  No.  21,"  in  Kovalevsky, 
pp.  12-13. 

52.  Fricke,  "Inaugural  Address,"  p.  13;  James  B.  McGuire,  Eugene  R.  Spangler,  and  Lem  Wong,  The 
Size  of  the  Solar  System,"  Scientific  American  vol.  204,  no.  4  (1961):  64-72.  The  value  given  in  the  article  is 
92,925,100  ±8,500  miles,  which  I  have  converted  into  kilometers  for  consistency. 

53.  Rechtin,  p.  368;  Muhleman,  D.  Holdridge,  and  N.  Block,  "Determination  of  the  Astronomical  Unit 
from  Velocity,  Range  and  Integrated  Velocity  Data,  and  the  Venus-Earth  Ephemeris,"  in  Victor,  Stevens,  and 
Golomb,  pp.  83-92.  Kovalevsky,  p.  1,  provides  a  list  of  their  names. 

54.  Muhleman  8  April  1993;  Muhleman  19  May  1994;  Shapiro  30  September  1993;  Evans  9  September 
1993. 


48  TO  SEE  THE  UNSEEN 


The  IAU  symposium  took  place  at  the  Paris  Observatory  between  27  and  31  May 
1963.  By  then,  Lincoln  Laboratory  and  JPL  had  refined  the  accuracy  of  their  calculations 
even  further,  to  ±  400  and  ±  250  kilometers  respectively.  In  his  inaugural  address,  Walter 
Fricke  lauded  the  accuracy  and  general  agreement  of  the  radar  measurements.  As  far  as 
Fricke  and  other  symposium  participants  were  concerned,  the  real  debate  was  between 
the  radar  and  dynamic  methods.  Spencer  Jones'  trigonometric  method  contained  too 
many  inherent  sources  of  systematic  error.  In  an  attempt  to  reconcile  the  dynamic  and 
radar  methods,  Brian  G.  Marsden,  an  astronomer  at  the  Yale  University  Observatory,  con- 
cluded in  favor  of  the  radar  measurements.  Rabe  defended  his  method  in  person,  argu- 
ing that  the  radar  observations  were  inconsistent  with  the  observed  orbit  of  Eros  and  with 
gravitational  theory.55 

Muhleman  and  Shapiro  supported  the  radar  method  and  explained  the  basis  on 
which  JPL  and  Lincoln  Laboratory  had  obtained  their  results.  Additional  support  for  the 
radar  method  came  from  Britain.  D.  H.  Sadler,  Superintendent  of  H.  M.  Nautical  Almanac 
Office  at  the  Royal  Greenwich  Observatory,  read  a  paper  on  the  results  of  the  Jodrell  Bank 
1962  Venus  experiment. 

Lest  it  appear  that  there  was  unanimous  approval  of  the  radar  method,  COSPAR 
raised  the  question  of  the  discrepancy  between  the  radar  observations  of  1958  and  1959 
and  those  of  1961.  Both  Muhleman  and  Shapiro  insisted  that  a  discussion  of  the  1958 
data,  which  they  both  labelled  "manifestly  wrong,"  would  be  too  difficult  and  serve  no  pur- 
pose. They  explained  that  the  1958  technology  was  highly  inadequate  and  stressed  the 
harmonious  agreement  among  the  1961  measurements.56 

The  participants  unanimously  adopted  Resolution  Six,  which  recommended  that  the 
astronomical  constants  be  studied  by  both  existing  and  new  methods,  so  that  the  results 
might  be  compared.  The  IAU  Executive  Committee  then  translated  Resolution  Six  into 
Resolution  Four,  which  recommended  that  a  working  group  study  the  system  of  astro- 
nomical constants,  including  the  astronomical  unit  expressed  in  meters.  Next,  the  IAU 
Executive  Committee  named  the  Working  Group  on  astronomical  constants:  Dirk 
Brouwer,  Jean  Kovalevsky  (Bureau  of  Longitudes,  Paris),  Walter  Fricke  (chairman), 
Aleksandr  A.  Mikhailov  (director  of  the  Pulkovo  Observatory,  Soviet  Union) ,  and  George 
A.  Wilkins  (Royal  Observatory  of  Greenwich;  Secretary).  The  Working  Group  sent  a  cir- 
cular letter  and  copies  of  the  Paris  resolutions  to  all  persons,  some  80  in  number,  who 
were  thought  to  be  likely  to  be  able  to  help  the  Group  or  who  might  be  affected  by  the 
introduction  of  new  constants.  The  Working  Group  met  in  January  1964,  at  the  Royal 
Greenwich  Observatory,  Herstmonceux  Castle,  and  drew  up  a  list  of  constants,  including 
the  astronomical  unit,  for  consideration  by  the  IAU  general  assembly,  which  met  in 
Hamburg  later  that  year.57 

The  Working  Group  met  again  during  the  Hamburg  meeting  on  27  August. 
Muhleman  and  Pettengill,  who  read  Shapiro's  paper  in  his  place,  reviewed  the  latest  radar 
determinations  of  the  astronomical  unit  by  JPL  and  Lincoln  Laboratory  from  new  obser- 
vations made  in  1964.  Pettengill  reported  that  preliminary  analysis  of  the  new  data  con- 
firmed a  value  of  149,598,000  kilometers,  while  Muhleman  disclosed  the  JPL  value  of 


55.  Kovalevsky,  p.  3;  Fricke,  "Inaugural  Address,"  pp.  12-13;  Fricke,  "Arguments  in  Favor  of  the  Revision 
of  the  Conventional  System  of  Astronomical  Constants,"  in  Pecker,  p.  606;  Marsden,  "An  Attempt  to  Reconcile 
the  Dynamical  and  Radar  Determinations  of  the  Astronomical  Unit,"  in  Kovalevsky,  pp.  225-236;  Rabe,  "On  the 
compatibility  of  the  Recent  Solar  Parallax  Results  from  Radar  Echoes  of  Venus  with  the  Motion  of  Eros,"  in 
Kovalevsky,  pp.  219-223. 

56.  Shapiro,   "Radar  Determination  of  the  Astronomical  Unit,"  in  Kovalevsky,  pp.   177-215,  and 
Muhleman,  "Relationship  between  the  System  of  Astronomical  Constants  and  the  Radar  Determinations  of  the 
Astronomical  Unit,"  in  ibid.,  pp.  153-175;  Kovalevsky,  pp.  298  and  311. 

57.  Kovalevsky,  pp.  314  and  323;  "Joint  Discussion  on  the  Report  of  the  Working  Group  on  the  IAU 
System  of  Astronomical  Constants,"  in  Pecker,  p.  600. 


FICKLE  VENUS  49 


149,598,500  kilometers.  The  error  of  measurement  reported  by  both  laboratories,  ±  100 
kilometers,  was  the  smallest  yet.58 

Walter  Fricke,  chair  of  the  Working  Group,  had  misgivings  about  the  radar  method: 
"One  could  argue  that  the  radar  results  are  still  too  fresh  to  deserve  full  confidence.  My 
personal  distrust  of  them  in  so  far  as  it  originates  in  their  newness  has  a  counterpart  in  my 
distrust  of  the  dynamical  [Rabe]  result  obtained  from  the  discussion  of  the  observations 
of  Eros."59 

Without  any  discussion  of  the  dynamic  method,  however,  the  Working  Group  rec- 
ommended adoption  of  a  value  expressed  in  meters  and  based  on  radar  observations.  The 
IAU  general  assembly  then  adopted  the  recommended  value,  149,600  X  106  meters 
(149,600,000  kilometers).60  It  was  now  a  matter  of  incorporating  the  new  value  into  the 
various  national  almanacs  and  ephemerides. 

The  Rotation  of  Venus 

The  establishment  of  a  highly  accurate  value  for  the  astronomical  unit  and  its  adop- 
tion by  the  IAU  was  but  one  way  that  planetary  radar  demonstrated  its  value  as  a  problem- 
solving  scientific  activity.  The  distance  from  Earth  to  Venus  as  measured  by  JPL  radar  also 
proved  essential  in  keeping  the  1962  Mariner  2  Venus  probe  on  target.  Early  in  its  flight, 
Mariner  2  went  off  course.  The  Pioneer  and  Echo  antennas  sent  midcourse  commands, 
and  a  34-minute  maneuver  put  Mariner  2  on  course.  Had  Rabe's  value  for  the  astronom- 
ical unit  been  used  in  place  of  the  radar  value,  Mariner  2  would  have  passed  Venus  with- 
out acquiring  any  useful  data.61 

Valuable  insight  into  the  rotation  of  Venus  further  demonstrated  the  problem-solv- 
ing scientific  merit  of  planetary  radar.  Optical  and  spectrographic  methods  failed  to 
reveal  the  planet's  period  or  direction  of  rotation,  because  Venus'  thick,  opaque  cloud 
layer  hid  all  evidence  of  its  motion.  Astronomers  could  only  infer  and  imagine.  Radar 
waves,  on  the  other  hand,  were  quite  capable  of  penetrating  the  Venusian  atmosphere;  yet 
determining  the  planet's  rotation  by  radar  was  still  not  easy.  The  key  was  methodical  and 
meticulous  attention  to  the  shape  of  the  echo  spectra.  Although  JPL,  Lincoln  Laboratory, 
Jodrell  Bank,  and  the  Soviet  Yevpatoriya  facility  calculated  rotational  rates  for  Venus,  only 
JPL  and  Lincoln  Laboratory  found  its  "locked"  orbit  and  retrograde  motion.62 

Evans  and  Taylor  at  Jodrell  Bank  published  the  first  estimate  of  the  planet's  rota- 
tional period,  about  20  days,  using  their  erroneous  1959  data.  In  1964,  John  Thomson 
reckoned  a  slow  rotational  rate,  "probably"  somewhere  between  225  days  and  a  similar  ret- 
rograde period.  After  seeming  to  be  on  the  brink  of  discovery,  Thomson  pulled  back,  con- 
cluding, "Future  observations  of  the  change  of  spectral  width  with  time  should  enable  the 
rotation  rate  and  rotation  axis  to  be  determined."  "Retrograde  rotation,"  he  held,  was 
"physically  unlikely."63 


58.  "Joint  Discussion,"  pp.   591,   599  and  602-603;   Shapiro,   "Radar  Determinations,"  in   Pecker, 
pp.  615-623. 

59.  "Joint  Discussion,"  p.  606. 

60.  Ibid.,  p.  606;  "Report  to  the  Executive  Committee  of  the  Working  Group  on  the  System  of 
Astronomical  Constants,"  in  Pecker,  p.  594. 

61.  Renzetti  17  April  1992;  Renzetti,  A  History,  pp.  20  and  31;  Renzetti,  Tracking  and  Data  Acquisition 
Support  for  the  Mariner  Venus  1962  Mission,  Technical  Memorandum  33-212  (Pasadena:  JPL,  1  July  1965),  pp.  9, 
17  and  75-76. 

62.  RCA  did  not  hesitate  a  guess  on  the  rotation  rate  or  direction.  Maron,  Luchak,  and  Blitzstein,  pp. 
1419-1421. 

63.  Evans  and  Taylor,  p.  1359;  Ponsonby,  Thomson,  and  Imrie,  "Radar  Observations  of  Venus  and  a 
Determination  of  the  Astronomical  Unit,"  Monthly  Notices  of  the  Royal  Astronomical  Society  128  (1964):  14-16. 


50  TO  SEE  THE  UNSEEN 


As  close  as  Jodrell  Bank  came  to  discovering  Venus'  retrograde  motion,  the  Soviets 
were  that  far  away.  Looking  at  frequency  shifts  in  their  1961  data,  Kotelnikov's  group  per- 
sistently estimated  the  planet's  rotational  period  as  11  days,  if  not  9  or  10  days.  They 
entirely  missed  the  planet's  retrograde  motion.  The  Soviet  error  arose  from  their  finding 
that  the  spectrum  had  a  wide  base,  at  least  400  hertz  wide,  indicating  rapid  motion.  All 
British  and  United  States  workers  agreed  that  the  spectrum  was  far  narrower.  Lincoln 
Laboratory,  for  example,  found  a  narrow  spectrum  of  only  0.6  hertz.  After  their  1962 
radar  study  of  Venus,  Kotelnikov  and  his  colleagues  re-evaluated  their  data  and  conclud- 
ed a  retrograde  rotational  period  of  200  to  300  days.64 

By  then,  though,  JPL  and  Lincoln  Laboratory  already  had  discovered  Venus'  retro- 
grade motion.  Finding  it  was  not  easy.  Along  the  way,  both  laboratories  concluded  that  the 
Venusian  day  was  as  long  as  its  year,  about  225  days.  Venus  was  "locked"  in  its  orbit,  turn- 
ing one  face  always  toward  the  Earth  at  the  moment  of  inferior  conjunction.  However, 
these  initial  reports  failed  to  note  the  planet's  retrograde  motion.65 

The  investigators  who  found  it  did  not  follow  the  same  path  of  discovery.  Just  as  the 
availability  of  technology  had  made  planetary  radar  astronomy  possible,  the  limits  of  that 
technology  shaped  the  paths  of  discovery.  JPL  harvested  the  benefits  of  a  powerful,  low- 
noise  continuous-wave  radar  in  their  1962  and  1964  Venus  experiment,  while  Lincoln 
Laboratory  reaped  the  rewards  of  their  computer  and  signal  processing  skills. 

The  Goldstone  radar  permitted  Roland  L.  Carpenter  to  find  the  retrograde  motion 
of  Venus  in  a  rather  novel  fashion.  Carpenter  actually  had  a  BA  in  psychology  from 
California  State  University  at  Los  Angeles,  but  he  had  been  interested  in  astronomy  since 
childhood,  and  he  had  worked  at  Griffith  Observatory  as  a  guide.  Finding  very  little  work 
available  in  psychology,  Carpenter  found  a  job  at  Collins  Radio  as  an  electrician  thanks  to 
his  friend,  astronomer  George  Abell  (known  for  Abell's  clusters  of  galaxies),  who  had  a 
summer  job  there.  Carpenter  gradually  worked  his  way  up  to  electronics  engineer,  simply 
through  his  work  experience  at  Collins  Radio.  Then,  when  JPL  began  hiring  people  with 
experience  in  radio  communications  for  the  Deep  Space  Network,  Carpenter  jumped  at 
the  opportunity.  Carpenter  worked  with  Dewey  Muhleman  in  Walt  Victor's  group  and 
took  advantage  of  JPL's  employee  benefits  program  by  pursuing  an  advanced  degree  in 
astronomy  at  UCLA,  while  working  full-time  at  JPL.  His  doctoral  dissertation,  'The  Study 
of  Venus  by  CW  Radar,"  written  under  Lawrence  Aller  and  completed  in  1966,  used  data 
from  the  1964  JPL  Venus  radar  experiment.66  By  then,  however,  Carpenter  already  had 
published  his  discovery  of  the  retrograde  rotation  of  Venus.67 


64.  Kuznetsov  and  Lishin,  pp.  199-201;  Kotelnikov,  "Radar  Contact  with  Venus,  "Journal  of  the  British 
Institution  of  Radio  Engineers  22  (1961):  295;  Kotelnikov  et  al,  "Results  of  Radar  Contact,"  p.  1732;  Kotelnikov, 
Dubrovin,  M.  D.  Kislik,  Korenberg,  Minashin,  Morozov,  Nikitskiy,  Petrov,  Rzhiga,  and  Shakhovskoy,  "Radar 
Observations  of  the  Planet  Venus,"  Soviet  Physics— Doklady  7  (1963):  728-731;  Kotelnikov,  Dubrovin,  V.  A. 
Dubinskii,   Kislik,    Kusnetsov,   Lishin,    Morozov,   Petrov,   Rzhiga,   G.   A.   Sytsko,    and   Shakhovskoy,    "Radar 
Observations  of  Venus  in  the  Soviet  Union  in  1962,"  Soviet  Physics— Doklady  8  (1964):  644;  Smith,  p.  15.  Rzhiga, 
"Radar  Observations  of  Venus  in  the  Soviet  Union  in  1962,"  in  M.  Florkin  and  A.  Dollfus,  eds.  Life  Sciences  and 
Space  Research  II  (New  York:  Interscience  Publishers,  1964),  pp.  178-189,  states  300  days  but  still  misses  the  ret- 
rograde motion. 

65.  Pettengill  et  al,  "A  Radar  Investigation  of  Venus,"  pp.  189-190;  Pettengill,  "Radar  Measurement  of 
Venus,"  in  Priester,  pp.  880-883.  The  range  given  was  between  115  and  500  days,  that  is,  225  (+275,  -110)  days. 
The  first  JPL  external  announcement  of  that  finding  was  made  in  a  paper  read  by  Solomon  Golomb  and 
Leonard  R.  Mailing  at  a  convention  on  radio  techniques  and  space  research  held  at  Oxford  in  July  1961.  Mailing 
and  Golomb,  pp.  297-303.  The  paper  was  not  published  until  October  1961  and  was  preceded  in  print  by  the 
internal  report,  Victor  and  Stevens,  "Summary  and  Conclusions,"  pp.  94-95.  See  also  Victor  and  Stevens, 
"Exploration   of  Venus  by  Radar,"   pp.   46-47;   Muhleman,   "Early  Results  of  the    1961  JPL  Venus  Radar 
Experiment,"   The  Astronomical  Journal  66   (1961):   292;  Victor  and  Stevens,   "The    1961  JPL  Venus  Radar 
Experiment,"  p.  94. 

66.  Carpenter,  telephone  conversation,  14  September  1993. 

67.  Carpenter,  "An  Analysis  of  the  Narrow-Band  Spectra  of  Venus,"  in  JPL  Research  Summary  No.  36-14  for 
the  Period  February  1,  1962  to  April  1,  1962  (Pasadena:  JPL,  1  May  1962),  pp.  56-59. 


FICKLE  VENUS 


51 


His  first  announcement  of  the  planet's  retrograde  motion  appeared  in  a  JPL  inter- 
nal report  dated  1  May  1962  and  was  based  on  the  1961  Venus  experiment.  Carpenter  sug- 
gested a  retrograde  rotational  period  of  about  150  days,  but  backed  off  from  insisting  on 
his  discovery.  "Unfortunately,"  Carpenter  concluded,  "a  definitive  answer  cannot  be  given 
for  the  rotation  period  of  Venus  based  on  the  present  data." 

Carpenter  hesitated  until  he  had  the  results  of  the  Goldstone  1962  Venus  experi- 
ment. Between  1  October  and  17  December  1962,  when  Venus  was  closest  to  Earth, 
Goldstone  made  nearly  daily  radar  observations  of  the  planet  with  a  13-kilowatt  continu- 
ous-wave transmitter  operating  at  2388  MHz  (12.6  cm).  Equipped  with  a  maser  and  a  para- 
metric amplifier,  the  system's  total  noise  temperature  was  only  40  K,  better  than  the  64  K 
achieved  in  1961. 68 

The  Goldstone  radar  was  sufficiently  powerful  and  sensitive  that  a  large  feature  on 
the  planet's  surface  showed  up  as  an  irregularity  or  "detail"  on  the  power  spectrum.  The 
surface  feature  scattered  back  to  the  radar  antenna  more  energy  than  the  surrounding 
area.  Normally,  most  spectral  irregularities  resulted  from  random  fluctuations  produced 
by  noise.  The  power  and  sensitivity  of  the  Goldstone  radar  made  all  the  difference. 

"On  close  examination,"  Carpenter  wrote,  "one  irregularity  was  found  to  persist  from 
day  to  day  and  to  change  its  position  slowly.. ..The  relative  permanence  of  the  detail  strong- 
ly suggests  that  it  was  caused  by  an  actual  physiographic  feature  on  the  surface  of  Venus 
and  that  its  motion  was  the  result  of  the  planet's  rotation.  The  true  nature  of  the  feature 
can  only  be  guessed  at;  however,  it  is  not  unreasonable  to  assume  that  it  is  a  particularly 
rough  region  of  rather  large  extent." 


j 

C                  ""° 

1     2 

V    '  1WO 

2 

V  '- 

§ 

i 

2 

1                                 n;0(U 

„___../ 

—     -Taj 

/ 

I                                     IVtVU 

'RtOUtNC 

T,  en 

FigureS 

Lower  portion  of  the.  spectra  obtained  by  Roland  Carpenter 
during  the  week  prior  to  the  1 962  conjunction  of  Venus. 
Note  the  persistent  detail  on  the  left  side  of  each  spectrum. 
Carpenter  followed  that  detail  to  determine  the  retrograde 
motion  of  Venus.  (Courtesy  of  Jet  Propulsion  Laboratory.) 


68.  Carpenter,  telephone  conversation,  14  September  1993;  Goldstein  and  Carpenter,  "Rotation  of 
Venus:  Period  Estimated  from  Radar  Measurements,"  Science  139  (1963):  910;  Carpenter,  "Study  of  Venus  by  CW 
Radar,"  The  Astronomical  Journal  69  (1964):  2.  Details  of  the  1962  JPL  Venus  radar  experiment  are  given  in 
Goldstein,  Stevens,  and  Victor,  eds.,  Radar  Exploration  of  Venus:  Goldstone  Observatory  Report  for  October-December 
1962,  Technical  Report  32-396  (Pasadena:  JPL,  1  March  1965). 


52  TO  SEE  THE  UNSEEN 


Carpenter  then  followed  the  movement  of  this  "detail"  in  order  to  deduce  the  plan- 
et's rotational  period.  He  calculated  that  Venus  had  either  a  forward  period  of  about  1200 
days  or  a  retrograde  period  of  230  days  from  one  conjunction  to  the  other.  Next,  he  mea- 
sured the  bandwidth  of  the  lower  portion  of  the  spectra;  their  widths  were  incompatible 
with  a  1200-day  forward  rotation.  The  base  bandwidth  measurements,  however,  did 
"strongly  suggest  that  the  sidereal  rotation  period  of  Venus  is  not  synchronous,  but  rather 
250  ±  40  days  retrograde."69 

Millstone  lacked  the  power  and  sensitivity  of  Goldstone.  The  discovery  of  Venus' 
retrograde  motion  at  Lincoln  Laboratory  by  William  B.  Smith  relied  instead  on  his 
computer  and  signal  analyzing  skills.  Although  Smith  preceded  Carpenter  in  announcing 
the  retrograde  motion  of  Venus  in  a  publication,  he  did  not  achieve  recognition  as  its 
discoverer. 

Smith  looked  at  the  spectral  bandwidths  of  radar  returns  on  11  separate  days 
between  2  April  and  8  June  1961.  Like  Carpenter,  he  failed  to  verify  a  synchronous  rota- 
tion; however,  Smith  came  to  realize  that  the  way  the  signal  bandwidth  changed  over  time 
could  be  explained  only  by  retrograde  motion.  He  wrote  up  his  findings  and  submitted 
them  to  his  supervisor,  Paul  Green,  for  approval.  Smith  wanted  to  feature  the  planet's  ret- 
rograde motion  in  his  paper,  but  Green  remembered  an  earlier  episode,  when  "we  had 
been  badly  burned."  That  was  the  embarrassment  of  1958. 

Green  hesitated.  Uranus  was  the  only  planet  then  known  to  have  a  retrograde  peri- 
od, "but  that  one  is  way  the  hell  out,  and  who  would  have  thought  that  the  next  planet  to 
the  Earth  would  have  had  that  kind  of  anomalous  behavior?"  Green  admitted,  "I  guess  I 
was  working  more  on  psychological  factors  than  on  anything  else.  So  I  had  Bill  tone  it 
down."  The  published  article's  abstract  read:  'The  (relatively  weak)  result  implies  a  very 
slow  or  possibly  retrograde  rotation  of  the  planet."  The  article  itself  contained  no  state- 
ment of  the  planet's  retrograde  motion.70 

The  watered  down  version  made  all  the  difference.  Carpenter  published  his  explicit 
and  unequivocal  results  jointly  with  fellow  JPL  radar  astronomer  Dick  Goldstein  in  the 
8  March  1963  issue  of  Science,  while  the  February  1963  issue  of  The  Astronomical  Journal 
carried  Smith's  suggestive  abstract.71 

Green  regretted  his  decision.  "Bill  Smith  is  the  man  who  discovered  that  Venus  has 
retrograde  spin,  and  he  should  go  down  in  the  history  books.  Due  to  me  he  didn't, 
because  his  paper  didn't  feature  it  the  way  it  should  have.  If  I  hadn't  sat  on  it,  it  would 
have  featured  it,  but  as  it  came  out,  it  didn't.  The  people  that  look  at  the  fine  print  real- 
ize that  he  had  that  message,  that  that  was  what  his  data  showed,  but  it  didn't  make  the 
big  splash  and  give  him  the  career  achievement  that  he  deserved."72  Fellow  Lincoln 
Laboratory  radar  astronomer  Irwin  Shapiro  concurred:  "I  felt  he  [Smith]  got  a  raw  deal, 
because  he  made  a  major  discovery  for  which  he  never  got  credit."73 

The  detection  of  Venus,  the  measurement  of  the  size  of  the  astronomical  unit,  and 
the  determination  of  the  rotational  period  and  direction  of  Venus  formed  the  foundation 
on  which  planetary  radar  astronomy  was  laid.  Planetary  radar  advanced  by  solving  prob- 
lems left  unresolved  or  at  best  unsatisfactorily  resolved  by  optical  methods.  Deliberately  or 
not,  the  problems  solved  supported  the  NASA  mission  to  explore  the  solar  system.  Driving 
the  new  scientific  activity  was  the  availability  of  a  new  generation  of  radars  built  for  mili- 
tary defense  (at  Lincoln  Laboratory)  and  for  space  exploration  (at  JPL).  The  limits  of  that 
technology  shaped  the  paths  of  discovery. 


69.  Carpenter,   "Study  of  Venus  by  CW  Radar,"  pp.  4-6;  Carpenter,  telephone  conversation,   14 
September  1993. 

70.  Green  20  September  1993;  Smith  29  September  1993;  Smith,  pp.  15-21. 

71.  Goldstein  and  Carpenter,  pp.  910-911;  Smith,  pp.  15-21.  Internal  evidence  indicates  that  Science 
received  the  paper  on  15  January  1963. 

72.  Green  20  September  1993. 

73.  Shapiro  30  September  1993. 


FICKLE  VENUS  53 


Without  technology  and  without  funding,  planetary  radar  astronomy  was  impossible. 
The  emergence  of  planetary  radar  coincided  with  the  creation  of  a  national,  civilian  space 
agency,  NASA,  a  national,  civilian  agency  to  fund  scientific  research,  the  National  Science 
Foundation  (NSF) ,  and  a  national,  military  space  research  agency,  ARPA.  It  also  paralleled 
the  rise  of  American  radio  astronomy  and  the  age  of  the  Big  Dish.  Standing  at  the  inter- 
section of  civilian  and  military  research  into  space,  the  ionosphere,  the  Moon,  and  the 
Sun,  planetary  radar  offered  much  to  potential  patrons.  It  was  a  wonderful  and  unique 
time  to  organize  a  new  scientific  activity. 


Chapter  Three 

Sturm  und  Drang 


The  period  between  1958  and  1964  saw  the  explosive  growth  of  planetary  radar 
astronomy  in  terms  of  the  number  of  active  facilities  and  investigators.  Investigators  in 
three  countries  (the  United  States,  Britain,  and  the  Soviet  Union)  attempted  to  detect 
Venus  in  1961,  and  three  facilities  in  the  United  States  alone  (Lincoln  Laboratory,  JPL, 
and  RCA)  succeeded.  During  the  1962  conjunction,  the  Jicamarca  Radar  Observatory,  a 
National  Bureau  of  Standards  ionospheric  facility  in  Peru,  made  radar  observations  of 
Venus  at  50  MHz  (6  meters) .  At  the  same  time,  the  Lincoln  Laboratory  solar  radar  facili- 
ty at  El  Campo,  Texas,  completed  in  the  summer  of  1960,  observed  Venus  at  38  MHz  (8 
meters).1  Thus,  by  1964,  five  American  facilities  had  performed  radar  experiments  on 
Venus. 

The  creation  of  radar  astronomy  courses,  a  textbook,  and  a  conference  dedicated 
solely  to  radar  astronomy  also  signalled  the  emergence  of  a  new  and  rapidly  growing 
scientific  field.  As  it  had  in  carrying  out  planetary  radar  experiments,  Lincoln  Laboratory 
took  the  lead  in  shaping  the  new  field.  In  addition  to  organizing  radar  astronomy  cours- 
es and  a  textbook,  Lincoln  Laboratory  sponsored  the  first,  and  only,  radar  astronomy 
conference  and  undertook,  in  association  with  the  Cambridge  astronomical  community, 
a  campaign  to  design  and  build  a  new  radar  research  instrument. 

MIT  routinely  offered  summer  courses  and  asked  Lincoln  Laboratory  to  propose 
some.  As  John  Evans  explained,  "Radar  astronomy  was  in  vogue,  we  were  just  entering  the 
Space  Age,  and  Sputnik  had  been  launched."  So  Lincoln  Laboratory  agreed  to  run  a  sum- 
mer school  in  radar  astronomy  beginning  in  August  1960.  In  all,  about  twenty  people  gave 
lectures.  Evans  talked  about  lunar  radar  astronomy.  Jack  Harrington,  head  of  the  Radio 
Physics  Division  of  Lincoln  Laboratory  and  in  charge  of  the  summer  course,  promised  lec- 
turers that  the  talks  would  be  organized  into  a  book.  As  it  turned  out,  Evans  recalled,  "the 
lecture  notes  weren't  that  good.  We  were  all  asked  to  rewrite  them."2 

In  August  1961,  Harrington  and  Evans  ran  the  radar  astronomy  summer  course 
again.  The  topics  and  lecturers  were  somewhat  different;  the  course  of  15  lectures  lasted 
only  one  week.  Among  the  lecturers  were  Paul  Green,  Bob  Kingston  (who  had  designed 
the  maser  for  the  1958  Venus  experiment),  Gordon  Pettengill,  Bob  Price,  Herb  Weiss 
(who  had  built  Millstone),  and  Victor  Pineo  (formerly  of  the  National  Bureau  of 
Standards) .  Von  Eshleman  (Stanford) ,  a  guest  lecturer,  discussed  solar  radar  experiments. 
The  week  ended  with  a  two-hour  tour  of  the  Millstone  Hill  Radar  Observatory  led  by 
Pettengill,  Pineo,  and  Evans  "to  observe  firsthand  a  modern  space  radar  facility  and  to  wit- 
ness a  representative  experiment  in  radar  astronomy."3 


1.  W.  K.  Klemperer,  G.  R.  Ochs,  and  Kenneth  L.  Bowles,  "Radar  Echoes  from  Venus  at  50  Me/sec,"  The 
Astronomical  Journal  69  (1964):  22-28;  Overhage  to  Lt.  Gen.  James  Ferguson,  28  March  1963,  MITA;  Jesse  C. 
James,  Richard  P.  Ingalls,  and  Louis  P.  Rainville,  "Radar  Echoes  from  Venus  at  38  Me/sec,"  The  Astronomical 
Journal  72  (1967):  1047-1050. 

2.  Evans  9  September  1993.  MITA  does  not  have  a  copy  of  the  1960  summer  course  lecture  notes. 

3.  Brochure,  MIT,  Radar  Astronomy:  Summer  Session  1961  August  14-18  (Cambridge:  MIT,  1961),  LLLA; 
MIT,  Radar  Astronomy:  Summer  Session  MIT,  August  14-18,  1961,  Lectures  1-15,  3  vols.  (Cambridge:  MIT,  1961), 
MITA. 

55 


56  TO  SEE  THE  UNSEEN 


The  radar  astronomy  summer  course  was  not  given  again,  "largely  because  the  peo- 
ple concerned  have  been  occupied  with  other  commitments,"  Evans  later  wrote.4  Price 
and  Green  were  no  longer  involved  in  radar  astronomy,  and  Pettengill  had  left  Lincoln 
Laboratory.  Harrington  himself  became  Director  of  the  MIT  Center  for  Space  Research, 
which  he  founded  with  funding  from  NASA  in  1963. 

At  the  end  of  the  1961  summer  course,  the  lecture  notes  were  assembled  into  a  three- 
volume  tome.  Yet,  as  Evans  explained,  "We  didn't  have  a  good  set  of  course  notes  that 
would  constitute  a  book."5  Paul  Green  became  irritated  with  the  lack  of  progress  on  the 
project,  announced  that  he  would  no  longer  contribute  any  material  to  the  book,  and 
nominated  Evans  to  take  over  the  project  from  Harrington.  Evans  found  himself  in  an 
awkward  situation;  Harrington  was  his  boss.  Fortunately,  Wilbur  B.  Davenport,  Jr.,  one  of 
the  Assistant  Directors  of  Lincoln  Laboratory,  had  an  interest  in  radar  astronomy  and 
pressured  Harrington  to  get  the  book  done  quickly. 

Evans  recalled:  "So  my  arm  got  twisted  very  hard  by  Davenport.  I  really  didn't  want 
to  do  it.  I  was  quite  busy,  and  I  didn't  want  to  take  over  Jack's  project,  so  I  resisted.  I  even- 
tually capitulated  after  enough  pressure  on  the  condition  that  a)  I  had  somebody  to  help 
me,  and  b)  I  had  a  secretary  assigned  to  do  typing  and  nothing  else,  because  part  of  the 
problem  was  just  getting  material  out  of  rough  draft  form  and  into  typed  form.  They 
agreed  to  both  of  those  conditions."  Tor  Hagfors,  a  graduate  of  Scandinavian  technical 
schools  and  the  Stanford  University  electrical  engineering  program,  edited  the  book  with 
Evans. 

Next,  the  project  met  difficulty  at  the  publisher.  The  McGraw-Hill  editor  who  had 
been  handling  the  project  left,  but  no  one  at  Lincoln  Laboratory  knew.  'The  manuscript 
sat  in  his  drawer  for  almost  two  years,"  Evans  related.  "Meanwhile,  we  were  thinking  that 
the  manuscript  was  going  through  proofing  and  so  on.  Finally,  we  got  a  letter  from  some 
guy  who  had  inherited  this  desk  and  found  this  manuscript.  He  got  it  printed  fairly  quick- 
ly, but  in  sort  of  photo-offset  form  rather  than  nice  copy.  At  least  it  came  out,  belatedly." 

Once  McGraw-Hill  published  Radar  Astronomy  in  1968,  radar  astronomy  had  a  text- 
book, parts  of  which  are  still  used  to  teach  radar  astronomy.  Nonetheless,  neither  MIT  nor 
Lincoln  Laboratory  (which  is  not  a  teaching  institution)  offered  a  course  in  radar  astron- 
omy until  1970.6  Although  the  Evans-Hagfors  textbook  and  the  MIT  summer  course  might 
have  served  to  train  a  generation  of  radar  astronomers,  they  did  not.  Planetary  radar 
astronomy  was  the  child  of  a  research  center  (Lincoln  Laboratory) ,  not  an  educational 
institution  (MIT) .  As  a  result,  Lincoln  Laboratory  radar  astronomers  did  not  reproduce 
themselves  in  a  traditional  academic  fashion  through  graduate  education,  but  through 
employment. 

Three  radar  astronomers  came  to  Lincoln  Laboratory  during  the  1960s  through 
employment:  Stanley  H.  Zisk,  Richard  P.  Ingalls,  and  Alan  E.  E.  Rogers.  Zisk,  who  created 
lunar  radar  images  for  NASA  in  support  of  the  Apollo  program,  and  Haystack  Associate 
Director  Dick  Ingalls,  who  had  been  a  Lincoln  Laboratory  employee  since  1953,  both  had 
degrees  in  electrical  engineering.  Alan  Rogers,  born  in  Salisbury,  Rhodesia  (now 
Zimbabwe),  earned  a  Ph.D.  in  electrical  engineering  from  MIT  in  1967,  and  was  trained 
in  radio  astronomy,  before  carrying  out  radar  astronomy  experiments.7 

As  far  as  defining  the  field  of  radar  astronomy,  and  particularly  in  terms  of  defining 
actual  and  potential  patrons,  the  most  important  step  taken  by  Lincoln  Laboratory  was 


4.  Evans  and  Tor  Hagfors,  eds.,  Radar  Astronomy  (New  York:  McGraw-Hill  Book  Company,  1968) ,  p.  viii. 

5.  Evans  9  September  1993. 

6.  Campbell  9  December  1993;  E-mail,  Pettengill  to  author,  29  September  1994;  Rogers  5  May  1994. 

7.  Pettengill  28  September  1993;  Rogers  5  May  1994;  NEROC,  "Technical  Proposal:  Radar  Studies  of 
the  Moon  (Topography),"  12  November  1971,  SEBRING. 


STURM  UND  DRANG  57 


the  organization  of  a  conference  on  radar  astronomy.  Never  again  did  another  such  con- 
ference take  place,  mainly  because  radar  astronomers  located  themselves  within  existing 
professional  organizations.  Moreover,  the  small  number  of  radar  astronomers  never  justi- 
fied the  creation  of  a  separate  society  or  journal. 

The  conference  underscored  the  Big  Science  environment  in  which  radar  astrono- 
my was  evolving.  Only  a  few  attempts  at  Venus  had  been  made  by  Lincoln  Laboratory  and 
Jodrell  Bank  when  the  conference  convened;  lunar,  meteor,  and  ionospheric  radar  stud- 
ies were  well  established.  Those  radar  studies  were  part  of  growing  civilian  and  military 
programs  in  ionospheric  and  communication  research.  More  importantly  for  planetary 
radar,  a  new  civilian  space  agency,  NASA,  had  been  created  only  the  year  before.  Its  cre- 
ation, and  the  prospect  of  participating  in  space  research,  eventually  shaped  the  new  field 
of  planetary  radar  astronomy  more  than  any  other  Big  Science  patron. 

The  Conference  on  Radar  Astronomy 

The  National  Academy  of  Sciences,  through  its  Space  Science  Board,  underwrote 
the  radar  astronomy  conference.  Established  in  1958,  the  Space  Science  Board  main- 
tained liaisons  with  the  National  Science  Foundation,  NASA,  ARPA,  the  Office  of  the 
Science  Advisor  to  the  President,  and  other  federal  agencies  participating  in  the  country's 
space  program.  The  Space  Science  Board  solicited  the  opinions  of  scientists  through  dis- 
cussions and  summer  studies  and  recommended  space  programs  to  federal  agencies.8 

Bruno  B.  Rossi,  a  member  of  the  Space  Science  Board  and  a  leading  MIT  physics 
professor,  organized  the  radar  astronomy  conference.  Rossi  had  undertaken  experimen- 
tal research  on  cosmic  rays  in  the  1930s,  before  working  at  Los  Alamos  Laboratory  during 
World  War  II.  He  joined  MIT  in  1946.  In  1958,  coincidentally  with  the  creation  of  NASA, 
Rossi  began  to  consider  the  potential  value  of  direct  measurement  of  the  ionized  inter- 
planetary gas  by  space  probes.9 

Thomas  Gold,  recently  hired  to  head  Cornell's  Center  for  Radiophysics  and  Space 
Research,  the  parent  organization  for  its  radio  and  radar  telescope,  and  MIT's  Philip 
Morrison,  both  members  of  the  Space  Science  Board,  assisted  Rossi  in  organizing  the  con- 
ference; however,  the  brunt  of  the  actual  work  fell  on  Rossi's  shoulders.  He  reserved  MIT's 
Endicott  House  in  Dedham,  Massachusetts,  for  15  and  16  October  1959.  Endicott  House 
had  a  dining  area,  meeting  rooms,  large  gardens,  and  accommodations  for  8  people;  the 
remainder  were  lodged  at  a  nearby  hotel. 

Rossi  saw  the  conference  as  a  small  group  meeting  to  develop  concrete  recommen- 
dations for  consideration  by  the  Space  Science  Board  at  its  October  meeting.  The  origi- 
nal conference  title,  "Reflections  and  Scattering  of  Radar  Signals  Beyond  Several  Earth 
Radii,"  by  definition  excluded  ionospheric  radar.  However,  the  revised  name, 
"Conference  on  Radar  Astronomy,"  was  less  unwieldy  and  did  not  appear  to  exclude  those 
interested  in  ionospheric  research.10 

Holding  a  different  vision  of  the  conference  was  Stanford  professor  of  electrical  engi- 
neering Von  R.  Eshleman.  Seeking  to  exploit  the  creation  of  NASA,  Eshleman  proposed 
radar  studies  of  planetary  ionospheres  and  atmospheres  from  spacecraft.  Such  studies 
were  a  logical  extension  of  Stanford's  ionospheric  radio  and  radar  work  of  the  1950s, 
which  included  a  pioneering  solar  radar  experiment. 


8.  Space  Science  Board,  Proposal  for  Continuation  of  Contract  NSR  09012-903,  28  October  1965, 
"NAS-SSB,  1965,"  NHO;  Joseph  N.  Tatarewicz,  Space,  Technology,  and  Planetary  Astronomy  (Bloomington:  Indiana 
University  Press,  1990) ,  p.  38. 

9.  Rossi  biographical  information,  MITA;  "President's  Report  Issue,"  MIT  Bulletin  vol.  82,  no.  1  (1946): 
137-138. 

10.  "Conference  on  Radar  Astronomy  Program,"  n.d.,  and  George  A.  Derbyshire,  Memorandum  for  the 
Record,  29  May  1959,  "ORG,  NAS,  1959  October  Space  Science  Bd.,  Conferences  Radar  Astronomy,  Dedham," 
NAS.  Hereafter,  Conference  Program  and  Derbyshire  Memorandum,  29  May  1959,  respectively. 


58  TO  SEE  THE  UNSEEN 


In  1959,  contemporary  with  the  first  radar  attempts  at  Venus,  Eshleman  and  Philip 
B.  Gallagher  of  Stanford,  with  Lt.  Col.  Robert  C.  Barthle  of  the  U.S.  Army  Signal  Corps,  a 
Stanford  graduate  student,  attempted  to  bounce  radar  waves  off  the  solar  corona.  The  Air 
Force  Cambridge  Research  Center  (AFCRC)  underwrote  the  Stanford  experiment,  and 
the  Office  of  Naval  Research  funded  the  46-meter  (150-ft)  dish  antenna  constructed  for 
ionospheric  research  under  the  direction  of  Oswald  Villard.  Although  Eshleman  claimed 
success,  a  comparison  of  his  results  with  those  obtained  shortly  afterward  by  the  El  Campo 
solar  radar  cast  serious  doubt  about  their  validity,  which  some  radar  astronomers  contin- 
ue to  express.11 

As  planning  for  the  radar  conference  was  underway,  Eshleman  was  preparing  the 
solar  radar  experiment  and  was  on  the  point  of  campaigning  NASA  to  underwrite  studies 
of  planetary  ionospheres  from  spacecraft.  It  was  a  pivotal  moment  for  calling  attention  to 
the  Stanford  radar  work.  Eshleman  saw  the  conference  as  a  Stanford  opportunity.  In  a  let- 
ter to  Rossi,  he  claimed  that  Stanford  already  "had  begun  to  plan  some  kind  of  a  meeting 
to  bring  together  all  who  are  active  in  this  field.  However  these  plans  had  [sic]  not  pro- 
gressed very  far."  He  proposed  a  larger  conference  with  Stanford  and  the  Stanford 
Research  Institute  (SRI)  "as  co-hosts."  If  the  AFCRC  were  invited  to  co-sponsor  the  con- 
ference, Eshleman  suggested,  part  of  the  travel  expenses  for  foreign  visitors  might  be  cov- 
ered. Conference  papers  could  be  published  as  a  group  in  the  Proceedings  of  the  Institute 
of  Radio  Engineers.12 

The  conference,  however,  was  solely  an  MIT  affair  sponsored  only  by  the  National 
Academy  of  Sciences.  The  spectrum  of  United  States  civilian  and  military  scientific  radar 
research  facilities  was  represented:  MIT  and  Lincoln  Laboratory,  Stanford  and  SRI, 
Cornell  University,  the  NRL,  and  the  National  Bureau  of  Standards  CRPL.  In  addition, 
radio  astronomers  were  invited  from  Harvard  University,  Yale  University,  the  University  of 
Michigan,  and  the  National  Radio  Astronomy  Observatory  (NRAO),  Green  Bank,  West 
Virginia,  the  country's  major  radio  astronomy  center.  ARPA  and  the  AFCRC  represented 
the  military. 

In  addition  to  representatives  of  the  Space  Science  Board,  Rossi  invited  the  National 
Science  Foundation  program  director  for  astronomy  and  NASA  Space  Science  chief 
Homer  E.  Newell,  Jr.  Unable  to  attend,  Newell  recommended  Nancy  G.  Roman  in  his 
place:  "Although  we  have  no  program  which  directly  involves  radar  astronomy,  Dr.  Roman 
will  be  happy  to  discuss  those  aspects  of  our  Astronomy  and  Astrophysics  Programs  which 
are  related  to  this  field.  I  am  sure  that  the  results  of  the  discussion  will  be  valuable  in  our 
program  planning."13  Roman  was  a  felicitous  choice;  she  had  carried  out  lunar  radar  stud- 
ies at  the  NRL.14 


11.  Eshleman,  telephone  conversation,  26 January  1993;  Eshleman  9  May  1994;  Eshleman,  Barthle,  and 
Gallagher,  "Radar  Echoes  from  the  Sun,"  Science  134  (1960):  329-332;  Eshleman  and  Allen  M.  Peterson,  "Radar 
Astronomy,"  Snentifec  American  203  (August,  1960):  50-51;  Barthle,  The  Detection  of  Radar  Echoes  from  the  Sun, 
Scientific  Report  9  (Stanford:  RLSEL,  24  August  1960);  Pettengill  28  September  1993. 

The  possibility  of  obtaining  radar  echoes  from  the  solar  corona  had  been  suggested  earlier  by  the 
Australian  ionosphericist  Frank  Kerr  in  1952  and  by  the  Ukrainians  F.  G.  Bass  and  S.  I.  Braude  in  1957.  Kerr, 
"On  the  Possibility  of  Obtaining  Radar  Echoes  from  the  Sun  and  Planets,"  pp.  660-666;  Bass  and  Braude,  "[On 
the  Question  of  Reflecting  Radar  Signals  from  the  Sun] ,"  Ukrains  "ky  Fizychny  Zhurnal  [Ukrainian  Journal  of  Physics] 
2  (1957):  149-164. 

12.  Eshleman  to  Rossi,  13  May  1959,  "ORG,  NAS,  1959  October  Space  Science  Bd.,  Conferences  Radar 
Astronomy,  Dedham,"  NAS. 

13.  "Preliminary  List  of  Invitees;"  "Draft  Recommendations  of  the  Conference  on  Radar  Astronomy," 
Appendix  A,  "List  of  Participants;"  Newell  to  Rossi,  18  June  1959;  Derbyshire  Memorandum,  29  May  1959;  and 
Derbyshire,  Memorandum  for  the  Record,  2  June   1959,   "ORG,  NAS,   1959  October  Space  Science  Bd., 
Conferences  Radar  Astronomy,  Dedham,"  NAS. 

14.  For  Roman's  lunar  radar  work  at  the  NRL,  see,  for  example,  Yaplee,  Roman,  Craig,  and  T.  F. 
Scanlan,  "A  Lunar  Radar  Study  at  10-cm  Wavelength,"  in  Bracewell,  ed.,  Paris  Symposium  on  Radio  Astronomy 
(Stanford:  Stanford  University  Press,  1959),  pp.  19-28,  and  Ch.  1,  note  69. 


STURM  UNO  DRANG  59 


Invitations  to  foreign  radio  and  radar  investigators  went  to  Jodrell  Bank,  the  Royal 
Radar  Establishment  (Malvern,  England),  the  Division  of  Radiophysics  of  the  Australian 
Commonwealth  Scientific  and  Industrial  Research  Organization  (CSIRO),  the  Chalmers 
University  of  Technology  Research  Laboratory  of  Electronics  (Gothenburg,  Sweden),  and 
the  Canadian  Defense  Research  Board  Telecommunications  Establishment.  No  Soviet  sci- 
entists were  invited. 

The  conference  program  highlighted  the  work  of  Lincoln  Laboratory.  After  a  talk  by 
Thomas  Gold  (Cornell)  on  the  scientific  goals  of  radar  astronomy,  Jack  Harrington 
(Lincoln  Laboratory)  explained  certain  experimental  techniques  and  Herb  Weiss 
(Lincoln  Laboratory)  spoke  on  transmitters,  receivers,  and  antennas.  Next  Paul  Green 
(Lincoln  Laboratory)  discussed  signal  detection  and  processing,  and  James  Chisholm 
(Lincoln  Laboratory)  talked  about  electromagnetic  propagation  phenomena.  In  another 
session,  organizations  represented  at  the  conference  described  their  research  programs. 
General  discussion  and  the  formulation  of  recommendations  took  up  the  second  day.15 

These  recommendations  defined  radar  astronomy  as  a  field  especially  useful  to 
NASA  and  the  rapidly  growing  space  effort.  The  arguments  set  forth  appeared  as  attempts 
to  garner  the  patronage  of  the  new  space  agency.  The  first  recommendation,  for  example, 
spoke  directly  to  NASA  and  argued  the  value  of  radar  astronomy  for  planetary  explo- 
ration. Launching  spacecraft  required  precise  measurements  of  interplanetary  distances 
and  knowledge  of  planetary  surface  and  atmospheric  conditions,  all  of  which  radar 
astronomy  was  capable  of  providing.  "The  importance  of  radar  astronomy  to  the  efficient  devel- 
opment of  space  science  must  not  be  underestimated, "  the  recommendation  exhorted. 

Additional  recommendations  urged  the  construction  of  new  radar  astronomy  facili- 
ties operating  at  a  variety  of  frequencies,  as  well  as  the  design  and  construction  of  large 
dish  and  array  antennas,  high-power  high-frequency  transmitters,  and  signal  detection 
and  recording  techniques.  The  construction  of  radar  telescopes,  the  conference  recom- 
mendations argued,  would  be  far  less  expensive  than  building  and  sending  planetary 
probes. 

Conference  recommendations  also  addressed  the  military  and  radio  astronomy. 
Planetary  radar  astronomy  at  Lincoln  Laboratory  would  not  have  existed  without  the  con- 
struction of  the  Millstone  Hill  radar,  which  the  military  funded.  However,  planetary  radar 
experiments  officially  did  not  exist;  military  research  was  the  first  priority.  Radar  astrono- 
my, the  recommendations  pleaded,  needed  facilities  of  its  own,  where  it  would  receive  top 
priority  and  be  "viewed  as  pure  science." 

Conference  recommendations  also  targeted  radio  astronomers.  "Where  large  radio  tele- 
scopes are  being  planned  or  built, "  one  recommendation  proposed,  "serious  consideration  be 
given  from  the  beginning  to  the  incorporation  of  provisions  for  a  high-powered  transmitter,  even  if  a 
transmitter  were  not  actually  installed."  The  recommendation  further  suggested  specifi- 
cally that  a  radar  transmitter  be  installed  on  the  10-GHz  (3-cm)  43-meter  (140-ft)  NRAO 
antenna,  thereby  offering  "an  excellent  opportunity  for  radar  investigations  at  very  high 
frequencies."  While  recognizing  that  the  dissimilar  needs  of  radar  and  radio  astronomers 
often  gave  rise  to  conflict,  one  recommendation  stated,  compromise  could  resolve  them.16 
As  we  shall  see  later,  however,  those  dissimilar  needs  were  beyond  compromise. 

Bruno  Rossi  submitted  the  conference  draft  recommendations  to  the  Space  Science 
Board  at  its  October  1959  meeting.  After  some  editing  and  checking  that  left  the  recom- 


15.  Derbyshire  Memorandum,  2  June  1959;  Conference  Program;  Rossi  to  Derbyshire,  10  June  1959, 
"ORG,  NAS,  1959  October  Space  Science  Bd.,  Conferences  Radar  Astronomy,  Dedham,"  NAS. 

16.  "Draft  Recommendations  of  the  Conference  on  Radar  Astronomy,"  pp.  5—8,  "ORG,  NAS,  1959 
October  Space  Science  Bd.,  Conferences  Radar  Astronomy,  Dedham,"  NAS.  Emphasis  in  original  text. 


60  TO  SEE  THE  UNSEEN 


mendations  unaltered,  the  Space  Science  Board  endorsed  them  for  distribution  to  fund- 
ing agencies  and  other  interested  groups.17  Endicott  House  was  the  last  conference  dedi- 
cated solely  to  radar  astronomy,  though  radar  astronomers  continued  to  meet  under  an 
existing  organizational  umbrella,  one  dedicated  not  to  planetary  science,  since  such  spe- 
cialized organizations  did  not  yet  exist,  but  to  radio  astronomy  and  electrical  engineering. 

L' Union  Radioscientifique  Internationale 

Although  much  of  the  earliest  radar  astronomy  work  grew  out  of  an  interest  in  ionos- 
pheric questions,  ionosphericists  and  planetary  radar  astronomers  soon  went  separate 
ways.  Planetary  radar  astronomers  grew  closer  to  their  colleagues  in  radio  astronomy,  with 
whom  they  shared  techniques  and  technologies,  such  as  antennas  and  low-noise  receivers. 
The  shift  of  planetary  radar  astronomy  from  the  ionospheric  to  the  radio  astronomy  com- 
munity was  manifest  within  the  Union  Radioscientifique  Internationale  (URSI),  which 
quickly  became  the  premier  forum  for  planetary  radar  astronomers.18 

URSI  was  an  international  radio  science  organization  founded  in  France  in  1921  by 
Gustave  Ferric  and  other  French  radio  pioneers.19  Its  big  tent  sheltered  a  range  of  fields, 
including  ionospheric  and  radio  astronomy  science,  united  by  a  common  technical  inter- 
est in  what  might  be  called  radio  science.  Lacking  telescopes  committed  entirely  to  their 
field,  planetary  radar  astronomers  worked  side-by-side  with  radio  astronomers  at  the  same 
observatory.  As  radar  astronomer  Donald  B.  Campbell  has  observed,  There  is  a  tremen- 
dous amount  of  cross-fertilization  between  planetary  radar  and  radio  astronomers  in 
terms  of  techniques  and  equipment."20  These  shared  technical  interests  and  instruments 
brought  planetary  radar  and  radio  astronomers  together  at  URSI  meetings. 

Radio  astronomers  had  had  their  own  commission  within  URSI  since  shortly  after 
World  War  II.  In  1946,  at  its  General  Assembly  meeting  in  Paris,  URSI  created  a  special 
subcommission  on  Radio  Noise  of  Extra-Terrestrial  Origin,  which  became  Commission  5, 
Extra-Terrestrial  Radio  Noise,  when  URSI  revised  its  commission  structure  at  its  1948 
Stockholm  meeting.  On  the  proposal  of  the  U.S.  National  Committee,  Commission  5 
became  the  Commission  on  Radio  Astronomy  two  years  later  at  the  General  Assembly 
meeting  in  Zurich.  Commission  5  concerned  itself  with  radio  astronomy,  as  well  as  obser- 
vations of  meteors  and  the  Moon  "by  radio  techniques,"  meaning  by  radar.  Thus,  for 
example,  at  the  Paris  URSI  symposium  on  radio  astronomy  held  in  July  1958,  a  number 
of  papers  featured  the  latest  lunar  radar  work  by  U.S.  and  British  investigators.21 

The  first  URSI  meeting — at  which  planetary  radar  astronomers  gave  papers — took 
place  in  San  Diego,  California,  between  19  and  21  October  1959,  immediately  following 
the  Endicott  House  Conference  on  Radar  Astronomy.  The  meeting  included  a  first-of-its- 
kind  symposium  on  radar  astronomy.  However,  presenting  the  panel  discussion  was  not 
Commission  5,  but  URSI  Commission  3,  Ionospheric  Radio. 


17.  Memorandum,  E.  R.  Dyer,  Jr.,   to  Participants,  Space  Science  Board  Conference  on  Radar 
Astronomy,  30  October  1959,  and  "Report  and  Recommendations  of  the  Conference  on  Radar  Astronomy," 
"ORG:  NAS,  1959  October  Space  Science  Bd.:  Conferences  Radar  Astronomy:  Dedham,"  NAS. 

18.  Pettengill  29  September  1993. 

19.  URSI  actually  dates  back  to  1913  and  the  creation  of  the  French  Commission  Internationale  de  TSF 
Scientifique.  TSF  (Telegraphic  Sans  Fil)  is  French  for  wireless  radio.  Albert  Levasseur,  De  la  TSF  a  I'electronique: 
Histoire  des  techniques  radioelectriques  (Paris:  ETSF,  1975),  pp.  79  and  87. 

20.  Campbell  9  December  1993. 

21.  Edge  and  Mulkay,  p.  44;  Bracewell,  Paris  Symposium,  passim. 


STURM  UND  DRANG  61 


The  seven  panel  members,  all  of  whom  had  participated  in  the  Endicott  House  con- 
ference, were  practicing  radar  astronomers  at  the  NRL,  Jodrell  Bank,  Stanford,  Lincoln 
Laboratory,  Cornell,  and  the  National  Bureau  of  Standards.  Von  Eshleman  was  the  panel 
moderator.  The  speakers  covered  lunar,  solar,  meteor,  auroral,  and  planetary  radar,  as  well 
as  radar  studies  of  the  exosphere  and  the  interplanetary  medium.  The  symposium  was  of 
some  historical  importance:  Paul  Green  described  planetary  range-Doppler  imaging, 
which  later  became  a  central  planetary  radar  technique.22 

By  the  URSI  Tokyo  meeting  of  September  1963,  planetary  radar  astronomy  had 
moved  to  the  newly  renamed  Commission  5,  Radio  and  Radar  Astronomy.  Twenty  institu- 
tions reported  on  recent  U.S.  developments  in  the  two  fields.  The  meeting  also  brought 
together  individuals  from  related  areas,  such  as  Commission  7,  Radio  Electronics,  where 
investigators  reported  on  parametric  amplifiers,  masers,  and  other  microwave  devices  of 
interest  to  planetary  radar  astronomers.23 

Although  the  electronic  side  of  planetary  radar  astronomy  drove  it  to  attend  URSI 
meetings  and  to  publish  in  such  journals  as  the  Proceedings  of  the  IRE,  the  astronomy  side 
pulled  it  toward  meetings  of  the  International  Astronomical  Union  (IAU)  and  the 
American  Astronomical  Society  (AAS)  and  to  publication  in  astronomy  and  general  sci- 
ence journals,  primarily  The  Astronomical  Journal,  Science,  and  Nature.  These  institutional 
and  publication  forums,  though,  did  not  meet  the  need  for  specialized  discussion  of  plan- 
etary topics. 

Sporadic  workshops  provided  only  limited  forums.  For  example,  the  1962  inferior 
conjunction  of  Venus  furnished  the  occasion  for  a  symposium  on  radar  and  radio  obser- 
vations of  that  planet.  Although  planetary  radio  astronomers  delivered  most  of  the  sym- 
posium papers,  radar  astronomers  Roland  Carpenter,  Dick  Goldstein,  and  Dewey 
Muhleman  described  the  latest  radar  research  on  Venus.24  Aside  from  a  preliminary 
report  by  National  Bureau  of  Standards  ionospheric  researchers  on  their  one-time-only 
radar  attempt  at  Venus,  the  symposium  was  strictly  a  JPL  affair. 

Starting  in  1965,  the  need  for  a  specialized  forum  for  presenting  and  discussing 
radar  research  began  to  be  met  through  a  joint  URSI-IAU  Symposium  on  Planetary 
Atmospheres  and  Surfaces  held  at  Dorado,  Puerto  Rico,  24-27  May  1965.  The  Organizing 
Committee  included  radar  astronomers  John  Evans,  Dewey  Muhleman,  and  Gordon 
Pettengill,  while  Evans  and  Pettengill  chaired  sessions  on  lunar  and  planetary  radar 
astronomy.  The  latter  session  brought  together  practitioners  from  Lincoln  Laboratory, 
JPL,  Cornell's  nearby  observatory  at  Arecibo,  and  the  Soviet  Union.25 

A  conference  on  lunar  and  planetary  science  held  during  the  week  of  13  September 
1965  and  organized  by  Caltech  and  JPL  also  had  its  share  of  planetary  radar  papers. 
Researchers  from  JPL,  Jodrell  Bank,  and  Cornell's  Arecibo  Observatory  spoke  on  Venus, 
while  JPL  and  Arecibo  representatives  read  papers  on  Mars.  Noticeably  absent,  however, 
were  researchers  from  Lincoln  Laboratory,  which  was  still  a  major  planetary  radar 
research  center.26 


22.  Ray  L.  Leadabrand,  "Radar  Astronomy  Symposium  Report,"  Journal  of  Geophysical  Research  65  (April 
1960) :  1 103-1 1 15;  Green  20  September  1993.  P.  Green  to  author,  21  December  1994,  states  that  Green  described 
range-Doppler  mapping  in  his  earlier  talk  at  the  Endicott  House  conference,  but  the  talk  was  not  published. 

23.  "URSI  National  Committee  Report,  XIV  General  Assembly,  Tokyo,  September,  1963:  Commission  5. 
Radio  and  Radar  Astronomy,  "Journal  of  Research  of  the  National  Bureau  of  Standards,  Section  D:  Radio  Science  68D 
(May  1964):  631-653;  "Commission  7.  Radio  Electronics,"  ibid.,  pp.  655-678. 

24.  The  symposium  papers  were  published  in  The  Astronomical  Journal  69  (1964):  1-72.  The  Astronomical 
Journal  is  the  publication  of  the  American  Astronomical  Society. 

25.  William  E.  Gordon,  "Preface,  "Journal  of  Research  of  the  National  Bureau  of  Standards,  Section  D:  Radio 
Science  69D  (July-December  1965):  iii.  This  was  a  special  issue  containing  the  symposium  papers. 

26.  Harrison  Brown,  Gordon  J.  Stanley,  Duane  O.  Muhleman,  and  Guido  Munch,  eds.,  Proceedings  of  the 
Caltech-JPL  Lunar  and  Planetary  Conference  (Pasadena:  Caltech  and  JPL,  15  June  1966). 


62  TO  SEE  THE  UNSEEN 


Planetary  radar  astronomy  is  at  the  convergence  of  science  and  engineering. 
Attendance  of  radar  astronomers  at  both  IAU  and  URSI  meetings  during  the  1960s 
reflected  the  dichotomous  nature  of  radar  astronomy,  perched  between  radio  engineer- 
ing (URSI)  and  astronomical  science  (IAU).  The  dichotomy  arose  from  the  fact  that  radar 
astronomy  is  a  set  of  techniques  (engineering)  used  to  generate  data  whose  interpretation 
yields  answers  to  scientific  questions. 

Just  as  vital  to  the  growth  of  radar  astronomy  as  meetings  and  journals  was  access  to 
instruments,  for  without  them  there  would  be  no  science  to  discuss  or  to  publish.  The  very 
availability  of  radar  instruments  capable  of  detecting  echoes  from  Venus  had  given  rise  to 
planetary  radar  astronomy,  and  the  field  has  remained  a  technology-driven  science  to  the 
present.  However,  radar  astronomers  did  not  seek  their  own  instruments.  In  league  with 
the  Cambridge  astronomical  community,  Lincoln  Laboratory  campaigned  to  design  and 
build  a  large  new  radar  and  radio  astronomy  research  instrument.  It  was  radio 
astronomers,  not  radar  astronomers,  who  performed  the  entrepreneurial  task  of  promot- 
ing the  new  facility  and  who  carried  radar  astronomy  interests  with  it.  The  same  radio 
astronomers  also  urged  opening  to  outside  researchers  the  Haystack  antenna  built  by 
Lincoln  Laboratory  for  military  communications  research. 

During  the  1960s,  radio  astronomy  underwent  the  kind  of  rapid  growth  rate  that  typ- 
ifies Big  Science.  With  fewer  facilities  and  researchers  than  Australia  or  Britain,  the  lead- 
ing countries  in  the  field,  the  United  States  saw  radio  astronomy  balloon  into  Big  Science 
as  funding  requests  and  antenna  construction  proposals  increased  in  size  and  number. 
Radio  astronomy  thus  provided  an  emerging  Big  Science  onto  which  radar  astronomers 
piggybacked  their  search  for  instruments  free  of  military  priorities  and  where  radar 
astronomy,  as  recommended  at  the  Endicptt  House  conference,  would  be  "viewed  as  pure 
science."  The  potential  rewards  of  piggybacking  were  great,  but  the  price  of  pursuing  Big 
Science  patronage  was  equally  great.  In  the  end,  the  effort  proved  troublesome  and  futile. 

Needles  and  a  Haystack 

The  decade  of  the  1960s  was  the  era  of  Big  Science  and  the  Big  Dish  in  radio  astron- 
omy. The  period  of  large  telescope  construction  between  1957,  when  thejodrell  Bank 
76-meter  (250-ft)  telescope  reached  completion,  and  1971,  when  the  100-meter  (328-ft) 
radio  telescope  near  Effelsberg  (about  40  km  from  Bonn)  began  operation,  has  been 
dubbed  "the  age  when  big  was  beautiful"  in  radio  astronomy.27  As  the  first  Venus  experi- 
ment took  place  at  Lincoln  Laboratory  in  1958,  a  host  of  new  radar  research  instruments 
of  unprecedented  size  were  on  the  drawing  board  or  under  construction  thanks  chiefly  to 
the  largesse  of  Cold  War  military  spending  on  scientific  research  and  secondarily  to  the 
National  Bureau  of  Standards  and  NASA. 

The  NRL  was  breaking  ground  on  a  183-meter  (600-ft)  antenna  at  Sugar  Grove,  West 
Virginia.  With  funding  from  ARPA,  Cornell  had  completed  initial  design  studies  of  a 
305-meter  (1,000-ft)  dish.  Lincoln  Laboratory  had  plans  for  a  37-meter  (120-ft)  antenna 
at  Haystack  Hill,  Massachusetts,  as  well  as  a  solar  radar  facility  at  El  Campo,  Texas,  both  of 
which  were  to  be  built  with  defense  funds.28  Stanford  and  SRI  were  soliciting  military 
backing  for  a  244-meter  (800-ft)  antenna.29  In  the  civilian  sector,  the  National  Bureau  of 


27.  Robertson,  pp.  285-291,  has  a  section  called  "When  Big  was  Beautiful." 

28.  The  El  Campo  facility  later  was  transferred  from  Lincoln  Laboratory  to  the  MIT  Center  for  Space 
Research  and  was  funded  by  a  National  Science  Foundation  grant.  MIT,  Radar  Studies  of  the  Sun  and  Venus:  Final 
Report  to  the  National  Science  Foundation  under  Grant  No.  GP-8128  (Cambridge:  MIT,  June  1969) . 

29.  Eshleman  9  May  1994;  Leadabrand  and  Eshleman,  A  Proposal  for  an  800-foot  Radar  Astronomy  Telescope 
(Stanford:  Stanford  Research  Institute,  9  October  1959),  Eshleman  materials. 


STURM  UND  DRANG  63 


Standards  was  building  a  three-station  radar  at  its  Long  Branch  Field  Station,  Illinois,  and 
a  huge  array  antenna  atjicamarca,  Peru,  to  study  the  ionosphere.  NASA's  Jet  Propulsion 
Laboratory  started  designing  a  large  antenna  system  for  its  Deep  Space  Network.  In 
Europe  and  Australia,  additional  large  antennas  were  on  the  drawing  board  or  under  con- 
struction. 

No  less  a  part  of  the  Big  Dish  era  were  the  Haystack  and  CAMROC/NEROC  anten- 
nas. Lincoln  Laboratory  designed  and  built  Haystack  for  military  communications 
research.  Cambridge-area  astronomers,  organized  as  the  Cambridge  Radio  Observatory 
Committee  (CAMROC),  then  as  the  Northeast  Radio  Observatory  Corporation 
(NEROC),  campaigned  to  open  Haystack  to  outside  researchers.  CAMROC/NEROC, 
again  in  collaboration  with  Lincoln  Laboratory,  also  sought  funding  for  the  design  and 
construction  of  a  new  large  radio  and  radar  telescope. 

Designing  and  building  those  big  dishes  was  a  nightmarish  introduction  to  Big 
Science  politics  for  radio  astronomers.  Bernard  Lovell,  the  veteran  planner  and  builder 
of  several  radio  telescopes  atjodrell  Bank,  not  to  mention  one  or  two  never  built,  in  1983 
wrote  to  Ed  Lilley,  the  Harvard  astronomer  who  headed  efforts  to  build  the  new  CAM- 
ROC/NEROC dish  and  to  open  Haystack  to  outside  researchers,  and  asked  him  to  sum- 
marize his  experience.  Lilley  replied  that  the  story  presented  an  "excellent  example  of  the 
mix  of  politics,  power  struggles,  fiscal  problems,  technology  and  dealings  with  Congress, 
and,  ultimately,  defeat  from  a  few  scientific  luminaries,"  and  that  he  would  "need  a  cabin 
overlooking  a  thunderous  sea  to  stimulate  the  mood  to  undertake  writing  a  history  of  the 
CAMROC/NEROC  campaign.'™ 

The  campaign  began  with  the  construction  of  the  Haystack  antenna,  which  replaced 
Millstone  as  the  Lincoln  Laboratory  planetary  radar.  On  12  April  1962,  Millstone  stopped 
operating,  so  that  Lincoln  Laboratory  could  upgrade  it  to  1,320  MHz  (23  cm;  L-band)  and 
increase  overall  system  capability,  as  part  of  the  Space  Surveillance  Techniques  Program. 
Over  the  years,  Lincoln  Laboratory  expanded  the  Millstone  location.  Near  the  Millstone 
planetary  radar  was  the  Lincoln  Laboratory  Communications  Site,  established  in  1957  to 
test  communication  equipment.  Upon  completion  of  the  tests,  the  antennas  were  torn 
down,  and  the  site  given  over  to  construction  of  an  X-band  transmitting  dish  for  use  in 
Project  West  Ford,  commonly  known  as  Project  Needles.  A  similar  X-band  station  was  built 
at  Camp  Parks,  outside  San  Francisco.31 

On  10  May  1963,  Project  Needles  launched  nearly  500  million  hair-like  copper  wires 
into  Earth  orbit,  thereby  forming  a  belt  of  dipole  antennas.  Lincoln  Laboratory  then  sent 
messages  coast  to  coast  via  the  orbiting  copper  needles  between  Camp  Parks  and 
Millstone  at  Westford,  Massachusetts  (hence  the  name  Project  West  Ford).  British  radio 
astronomers,  such  as  Martin  Ryle  and  Lovell,  as  well  as  optical  astronomers,  objected  fer- 
vently to  Project  Needles,  and  the  Council  of  the  Royal  Astronomical  Society  formally 
protested  to  the  U.S.  President's  Science  Advisor.32  Haystack  was  intended  officially  as  a 
state-of-the-art  radar  for  Project  Needles. 


30.  Quoted  in  Lovell,  TheJodreU  Bank  Telescopes  (New  York:  Oxford  University  Press,  1985) ,  pp.  249-250. 
Lovell  has  described  his  experiences  injodrell  Bank  and  TheJodreU  Bank  Telescopes. 

31.  Overhage  to  Ferguson,  21  May  1962;  Overhage  to  Ferguson,  28  December  1962;  Overhage  to 
Roscoe  Wilson,  30  June  1961;  J.  W.  Meyer,  The  Lincoln  Laboratory  General  Research  Program,"  paper  pre- 
sented at  the  Joint  Services  Advisory  Committee  meeting,  19  April  1962,  pp.  5-6;  and  W.  H.  Radford  to  B.  A. 
Schriever,  6  May  1964,  1/24/AC  134,  MITA;  Lincoln  Laboratory,  "Millstone  Hill  Field  Station,"  April  1965, 
LLLA. 

32.  Overhage  to  Ferguson,  26  June  1963,  1/24/AC  134,  MITA;  Overhage  and  Radford,  The  Lincoln 
Laboratory  West  Ford  Program:  An  Historical  Perspective,"  Proceedings  of  the  IEEE  52  (1964):  452-454;  Folder 
"Project  West  Ford  Releases  and  Reports,"  1 .1.1  A.  Much  of  the  Proceedings  of  the  IEEE  52  (1964):  452-606,  deals 
exclusively  with  Project  West  Ford.  For  antagonism  of  radio  astronomers  to  Project  Needles,  see  Lovell, 
Astronomer  by  Chanct,,  pp.  331-334;  Martin  Ryle  and  Lovell,  Interference  to  Radio  Astronomy  from  Belts  of 
Orbiting  Dipoles  (Needles),"  Quarterly  Journal  of the  Royal  Astronomical  Society  3  (1962):  100-108;  D.  E.  Blackwell 
and  R.  Wilson,  "Interference  to  Optical  Astronomy  from  Belts  of  Orbiting  Dipoles  (Needles),"  ibid.,  pp. 
109-117;  and  H.  Bondi,  The  West  Ford  Project,"  ibid.,  p.  99. 


TO  SEE  THE  UNSEEN 


Figure  9 

Preyed  Needles  planned  to  launch  nearly  500  million  hair-like  copper  wires  into  Earth  orbit,  thereby  forming  a  belt  ofdipole 
antennas.  Haystack  Observatory  originally  was  built  as  part  of  Project  West  Ford,  which  was  commonly  known  as  Project 
Needles.  (Courtesy  of  MIT  Lincoln  Laboratory,  Lexington,  Massachusetts,  photo  no.  P20 1-229.) 


STURM  UND  DRANG  65 


Project  Needles  and  the  Haystack  radar  exemplified  the  new  research  directions 
taken  by  Lincoln  Laboratory.  The  Laboratory  had  pioneered  three  major  air  defense  sys- 
tems: the  DEW  Line,  the  SAGE  System,  and  the  Ballistic  Missile  Early  Warning  System. 
With  the  formation  of  the  MITRE  Corporation  in  1958,  Lincoln  Laboratory  divested  itself 
of  manned  bomber  defense  activity  and  engaged  in  new  research  programs  that  addressed 
military  problems  in  ballistic  missile  re-entry  systems  and  ballistic  missile  defense  radars; 
military  satellite  communications;  and  the  detection  of  underground  nuclear  explosions 
(Project  Vela  Uniform).  The  joint  services  and  ARPA  funded  this  work  and  supported 
Lincoln  Laboratory's  program  of  general  research,  which  included  radar  and  radio 
astronomy.33 

Besides  Project  Needles,  additional  applications  proposed  for  Haystack  were  track- 
ing communication  satellites  and  radar  astronomy,  the  former  justified  as  an  adjunct  to 
communications  research.  The  facility's  X-band  operating  frequency  ruled  out  meteor 
studies.  Radio  astronomy  was  also  not  among  the  initial  proposed  uses  but  emerged  later 
in  the  earliest  funding  proposals  submitted  to  the  Air  Force.34 

The  design  of  Haystack  was  an  in-house  Lincoln  Laboratory  effort  for  about  a  year 
and  a  half  before  the  Air  Force  lent  its  financial  support.  The  design  progressed  through 
several  evolutionary  stages.  The  initial  March  1958  design  called  for  a  37-meter-diameter 
(120-ft-diameter)  parabolic  reflector  with  a  Cassegrainian  feed,  low-noise  maser  receivers, 
and  operation  in  the  X-band,  all  characteristics  of  the  earlier  West  Ford  antennas.  The 
price  tag  was  estimated  to  be  about  $5  million,  which  was  too  high  for  Air  Force  approval. 

The  problem  was  to  reduce  the  facility's  cost,  while  designing  a  reflector  that  would 
maintain  the  high  tolerances  required  for  the  short  X-band  wavelength.  Exposure  to  wind 
and  the  Sun  would  warp  the  dish  too  much  to  be  effective  at  X-band.  One  solution  would 
have  been  to  select  a  lower  frequency  range,  say  S-band,  but  participation  in  Project 
Needles  dictated  an  X-band  operating  frequency.  The  solution  was  to  place  the  antenna 
inside  a  radome,  which  not  only  protected  the  antenna  from  the  Sun  and  wind,  but  also 
reduced  the  weight  and  power  needed  to  drive  the  antenna.  The  radome  design  was  sig- 
nificantly cheaper,  too,  lowering  the  estimated  cost  from  $5  million  to  between  $1.5  and 
$2  million.  Adding  the  radome  raised  a  new  design  issue,  however,  because  radomes  had 
never  been  used  before  at  X-band. 

Lincoln  Laboratory  had  developed  a  radome  for  L-band  Millstone-type  radars,  but  it 
could  accommodate  a  dish  no  larger  than  26  meters  (85  ft)  in  diameter.  To  enclose  the 
Haystack  37-meter  (120-ft)  antenna,  Lincoln  Laboratory  engineers  raised  the  radome 
above  ground  level  and  enlarged  it  from  five-eighths  to  nine-tenths  of  a  complete  sphere. 
Electrical  tests  carried  out  in  March  1959  determined  that  a  reduction  in  panel  thickness 
would  permit  the  radome's  use  at  X-band. 

In  November  1959,  Herb  Weiss  became  Haystack  project  engineer.  The  following 
month,  the  Air  Force  committed  financial  support  to  die  project.  Lincoln  Laboratory 
took  bids  on  the  radar's  construction  and  signed  a  contract  with  North  American  Aviation 
(Ohio  Division)  on  1  December  1960.  A  separate  Air  Force  contract  procured  the  radome 
and  base  extension. 

Haystack  was  dedicated  on  8  October  1964,  at  Tyngsboro,  Massachusetts,  about  30 
miles  northwest  of  Boston,  but  only  a  half  mile  up  the  road  from  Millstone.  Haystack  was 
unique  in  its  use  of  special  plug-in  boxes.  Each  box  was  2.4  by  2.4  by  3.7  meters  (8  by  8  by 
12  ft)  and  could  hold  up  to  2  tons  of  equipment.  One  box  contained  a  100-kilowatt 


33.  Lincoln  Laboratory,  The  General  Research  Program,  Report  DOR-533  (Lexington:  Lincoln  Laboratory, 
15  June  1967),  p.  1. 

34.  John  Harrington,   The  Haystack  Hill  Station,  Technical  Memorandum  78   (Lexington:  Lincoln 
Laboratory,  13  October  1959),  pp.  1  and  5-7,  LLLA. 


66 


TO  SEE  THE  UNSEEN 


Figure  10 

Exterior  view  of  the  Haystack  Observatory  in  1964,  when  the  facility  was  dedicated.  There,  MIT  and  Lincoln  Laboratory  radar 
astronomers  imaged  the  Moon  and  Venus  and  conducted  a  test  of  General  Relativity.  At  the  time  of  its  dedication,  Haystack 
was  one  of  only  three  large  antennas  conducting  radar  astronomy  research  on  a  regular  basis.  (Courtesy  of  MIT  Lincoln 
Laboratory,  Lexington,  Massachusetts,  photo  no.  P10.29-783.) 

continuous-wave  X-band  (7,750  MHz;  4  cm)  transmitter,  cryogenic  low-noise  receivers, 
and  associated  microwave  circuits  for  planetary  radar  research.35 

As  Haystack  construction  was  underway,  a  key  meeting  of  Harvard  University 
astronomers,  Donald  Menzel,  director  of  the  Harvard  College  Observatory,  Leo 
Goldberg,  and  Ed  Lilley,  took  place  on  24  May  1963.  They  came  together  in  order  to  seek 
access  to  this  new,  more  sensitive  telescope.  As  a  secondary  objective,  they  sought  to 
design  and  build  a  larger  radio  telescope  in  collaboration  with  Lincoln  Laboratory. 


35.  Overhage  to  Ferguson,  14  November  1962,  Overhage  to  B.  A.  Schriever,  27  January  1964,  and 
brochure,  "Dedication  Haystack  Microwave  Research  Facility,"  1/24/AC  134,  MITA;  Memorandum,  J.  A.  Kessler 
to  Radford,  30  September  1964,  LLLA;  "Millstone  Hill  Field  Station;"  Harrington,  Haystack  Hill,  pp.  2-3;  Weiss 
29  September  1993.  For  a  discussion  of  the  design  and  construction  of  Haystack,  see  Weiss,  "The  Haystack 
Microwave  Research  Facility,"  IEEE  Spectrum  2  (February  1965):  50-69;  Evans,  Ingalls,  and  Pettengill,  The 
Haystack  Planetary  Ranging  Radar,"  in  L.  Efron  and  C.  B.  Solloway,  eds.,  Scientific  Applications  of  Radio  and  Radar 
Tracking  in  the  Space  Program,  Technical  Report  32-1475  (Pasadena:  JPL,  July  1970),  pp.  27-36;  and  Weiss,  W.  R. 
Fanning,  F.  A.  Folino,  and  R.  A.  Muldoon,  "Design  of  the  Haystack  Antenna  and  Radome,"  in  James  W.  Mar  and 
Harold  Liebowitz,  eds.,  Structures  Technology  for  Large  Radio  and  Radar  Telescope  Systems  (Cambridge:  MIT  Press, 
1969),  pp.  151-184. 


STURM  UND  DRANG  67 


Lincoln  Laboratory  radar  and  radio  astronomers  already  enjoyed  relatively  free  access  to 
Haystack,  and  Lincoln  Laboratory  radio  astronomers  often  collaborated  with  their  col- 
leagues at  Harvard  Observatory's  Agassiz  Station,  as  well  as  at  the  NRAO.  The  Agassiz 
Station  had  been  training  graduate  students  in  radio  astronomy  for  about  ten  years  under 
a  National  Science  Foundation  grant. 

Gaining  limited  use  of  Haystack  was  not  difficult.  Lilley  approached  Lincoln 
Laboratory  regarding  use  of  Haystack  in  July  1964.  In  September  1965,  Lincoln 
Laboratory  and  the  Air  Force  reached  a  mutually  agreeable  policy  on  Haystack  as  well  as 
Millstone.  The  Air  Force  encouraged  use  of  the  two  facilities  by  scientists  outside  the 
Department  of  Defense  and  made  Lincoln  Laboratory  responsible  for  scheduling  time. 
Lincoln  Laboratory  had  to  report  all  outside  use  of  Millstone  and  Haystack  to  the  Air 
Force,  which  had  final  approval  on  all  requests.  Finally,  outside  agencies  would  have  to  pay 
an  hourly  fee,  to  be  determined  by  Lincoln  Laboratory,  to  defray  operating  and  upkeep 
costs. 

At  the  same  Harvard  meeting  of  24  May  1963,  Lilley  also  suggested  that  Harvard, 
MIT  (including  Lincoln  Laboratory),  and  the  Smithsonian  Astrophysical  Observatory 
(SAO)  jointly  undertake  a  cooperative,  regional  effort  to  build  a  large  dish  antenna  free 
of  military  limitations  for  radio  astronomy  research.  The  project  sought  to  marry  the 
strength  of  Lincoln  Laboratory  in  radar  astronomy  and  the  thriving  Harvard  program  in 
radio  astronomy. 

The  proposed  large  antenna  also  would  serve  the  interests  of  radar  astronomers. 
Although  Haystack's  greater  power  and  sensitivity  outclassed  Millstone,  Lincoln 
Laboratory  radar  astronomers  realized  that  radars  then  under  construction,  namely 
Cornell's  305-meter  (1,000-ft)  antenna  and  JPL's  64-meter  (210-ft)  Mars  Station,  would 
outperform  Haystack.  Lincoln  Laboratory  radar  astronomers  therefore  sought  a  tele- 
scope with  Arecibo's  sensitivity,  but  operating  at  a  higher  frequency.36 

New  enthusiasm  for  the  construction  of  the  large  telescope  ignited  upon  the  release 
of  the  Whitford  Report,  which  had  endorsed  the  construction  of  large  dish  telescopes  for 
radio  astronomy.  The  Whitford  Report  grew  out  of  Congressional  reaction  to  the  Navy's 
disastrous  attempt  to  build  an  enormous  steerable  dish  antenna  in  West  Virginia. 


Sugar  Grove 


The  specter  that  haunted  all  large  radio  telescope  dish  projects  was  Sugar  Grove.  In 
the  words  of  a  report  of  the  Comptroller  General  of  the  United  States  to  Congress,  'The 
complexity  and  unique  character  of  the  Big  Dish  [Sugar  Grove]  were  underestimated 
from  the  inception  of  the  project."37  As  late  as  1965,  Harvard  astronomer  Ed  Lilley  wrote 
his  colleagues,  "International  radio  scientists  still  regard  the  U.S.  Navy  600  foot 


36.  "Ad  Hoc  Committee  on  Large  Steerable  Antenna,  Report,  SJuly  1963,"  5/1/AC  135,  Memorandum, 
Lilley  to  File,  n.d.,  10/1/AC  135,  Memorandum,  Lilley  to  Sebring  and  Meyer,  28  July  1964,  11/1/AC  135, 
Memorandum,  27  September  1965,  "A  Policy  for  the  Use  of  the  Millstone  Hill  and  Haystack  Facilities  by 
Agencies  outside  the  Department  of  Defense,"  6/1/AC  135,  and  "Ad  Hoc  Committee  on  Large  Steerable 
Antenna,  Report,  SJuly  1963,"  5/1/AC  135,  MITA;  Lincoln  Laboratory,  General  Research  Program,  Report  DOR- 
533,  p.  25;  MIT  Research  Laboratory  of  Electronics,  Annual  Research  Review  and  Twentieth  Anniversary  Program, 
10-12  May  1966,  23  March  1966,  pp.  7-8,  13-14,  NHOB. 

37.  Comptroller  General,  Report  to  the  Congress  of  the  United  States:  Unnecessary  Costs  Incurred  for  the  Naval 
Radio  Research  Station  Project  at  Sugar  Grove,  West  Virginia.  (Washington:  GPO,  April  1964),  p.  7.  For  additional 
background  on  the  Sugar  Grove  dish,  see  Edward  F.  McClain,  Jr.,  The  600-foot  Radio  Telescope,"  Scientific 
American  202  (January  1960):  45-51;  James  Bamford,  The  Puzzle  Palace:  A  Report  on  America's  Secret  Agency  (New 
York:  Penguin,  1983),  pp.  218-221;  and  Daniel  S.  Greenberg,  "Big  Dish:  How  Haste  and  Secrecy  Helped  Navy 
Waste  $63  Million  in  Race  To  Build  Huge  Telescope,"  Science  144  (1964):  1111-1112. 


68  TO  SEE  THE  UNSEEN 


paraboloid  as  a  'radio  telescope'  fiasco,  even  though  the  project  had  minuscule  associa- 
tion with  basic  research."38 

As  early  as  1948,  NRL  scientists  devised  a  plan  for  a  large  steerable  telescope  for 
detecting  and  studying  radio  sources.  By  1956,  the  NRL  had  developed  an  initial  propos- 
al which  called  for  a  reflector  183  meters  (600-ft)  in  diameter  with  accurate  maneuver- 
ability and  precision  positioning  controls.  The  huge  dish  would  be  able  to  turn  a  full  360 
degrees  in  the  horizon  and  tilt  to  any  angle  of  elevation  from  the  zenith  to  the  horizon.  If 
completed,  the  183-meter  steel-and-aluminum  antenna  would  have  stood  taller  than  the 
Washington  Monument,  weighed  about  22,000  tons  (the  weight  of  an  ocean  liner) ,  and 
been  the  largest  movable  land-based  structure  ever  constructed  in  the  world. 

The  Navy  began  breaking  ground  for  the  U.S.  Naval  Radio  Research  Station,  Sugar 
Grove,  West  Virginia,  telescope  in  June  1958.  As  construction  got  underway,  the  price  tag 
rose.  The  initial  cost  estimate  was  $20  million,  but  climbed  to  $52.2  million  in  February 
1957,  when  the  Department  of  Defense  submitted  requests  for  fiscal  1958  military  con- 
struction funds  to  Congress.  Later  in  1957,  coincidental  with  the  launch  of  Sputnik,  the 
Navy  expanded  the  project  concept  and  included  certain  (still)  classified  military  surveil- 
lance tasks.  The  nature  of  those  tasks,  nonetheless,  was  an  open  secret.  The  Navy  planned 
to  listen  to  Soviet  radio  communications  as  they  were  reflected  from  the  Moon,  an  idea 
that  grew  out  of  the  lunar  radar  work  carried  out  by  Benjamin  Yaplee's  group  at  the  NRL. 
Solar,  planetary,  and  ionospheric  radar  experiments  followed. 

These  new  tasks  inflated  the  estimated  price  tag  to  $79  million,  and  the  decision  to 
redesign  and  build  the  telescope  at  the  same  time  further  ballooned  the  estimated  cost  to 
more  than  $200  million  ($300  million  in  some  estimates) ,  which  was  the  total  estimated 
cost  when  the  Department  of  Defense  canceled  the  project  in  July  1962.  The  fatal  deci- 
sion to  design  and  erect  at  the  same  time  was  an  acknowledged  "calculated  risk"  in  order 
to  save  roughly  three  or  four  years  of  construction  time.  The  emerging  new  design  called 
for  an  antenna  that  was  far  too  heavy  for  its  support  structure,  which  was  already  under 
construction.  Further  complicating  the  project  was  an  internal  turf  battle  between  the 
Bureau  of  Yards  and  Docks  and  the  Naval  Research  Laboratory.  By  the  time  the 
Department  of  Defense  canceled  Sugar  Grove,  the  Navy  had  spent  $42,918,914  on  the 
project,  but  with  the  settlement  of  termination  claims  included,  the  secretary  of  defense 
estimated  that  the  total  expenditure  for  the  telescope  amounted  to  between  $63  and  $64 
million. 

An  investigation  by  the  comptroller  general  concluded  that  the  Navy  had  incurred 
unnecessary  costs  in  the  construction  and  cancellation  of  the  big  dish.39  The  Sugar  Grove 
fiasco  raised  serious  questions  about  the  spending  of  military  research  and  development 
dollars.  As  Senator  Hubert  H.  Humphrey  (D-Minn.)  pointed  out  in  August  1962,  Sugar 
Grove  had  "many  of  the  earmarks  of  other  research  and  development  projects  which 
turned  out  to  be  'white  elephants.'"40  The  next  month,  Sugar  Grove  came  under 
Congressional  scrutiny. 


38.  Memorandum,  Lilley,  August  1965,  "Comments  on  a  Regional  Radio  and  Radar  Research  Facility  for 
the  New  England  Area,"  p.  2-1,  Box  7,  UA  V  630.159.10,  PAHU. 

39.  NRL,  Careers  in  Space  Communications  (Washington:  NRL,  n.d.) ,  p.  3,  NRL,  Radio  Astronomy  and  the 
600-foot  Dish  (Washington:  NRL,  n.d.),  n.  p.,  and  The  Big  Dish,"  typed  and  edited  manuscript,  NRLHRC; 
Comptroller  General,  pp.  2-4,  6  &  11.  Early  specifications  for  Sugar  Grove  did  not  include  radar  experiments. 
See,  for  example,  Specifications  for  the  Naval  Radio  Facility,  Sugar  Grove,  W.  Va.  (Washington:  NRL,  December  1957), 
and  Specifications  for  the  U.S.  Naval  Radio  Research  Station  Sugar  Grove,  W.  Va.  (Washington:  NRL,  September  1959), 
NRLHRC.  Later  specifications,  though,  did  indicate  radar  experiments.  P.  Green  to  Robert  Page,  14  April  1960, 
and  other  documents,  Green  materials;  Eshleman,  "Sun  Radar  Experiment,"  in  MIT,  Radar  Astronomy,  vol.  3,  lec- 
ture 15,  p.  10.  Fiscal  irresponsibility  was  not  the  sole  factor  leading  to  the  termination  of  the  Sugar  Grove  pro- 
ject; the  availability  of  satellites  to  perform  its  espionage  functions  was  certainly  another. 

40.  Congressional  Record,  87th  Cong.,  2d  sess.,  1962,  Vol.  108,  pt.  12,  pp.  16175-16178. 


STURM  UND  DRANG  69 


The  Subcommittee  on  Applications  and  Tracking  and  Data  Acquisition  of  the  House 
Committee  on  Science  and  Astronautics  opened  hearings  on  radio  and  radar  astronomy 
in  September  1962.  The  Sugar  Grove  fiasco  motivated  the  hearings,  at  which  radio 
astronomers  defended  their  telescope  projects.  Witnesses  discussed  alternatives  to  large 
dishes,  such  as  arrays,  in  which  a  number  of  small  antennas  electronically  linked  to  each 
other  acted  as  a  single  large  antenna.  Common  to  the  witnesses'  testimony  was  the  asser- 
tion that  the  United  States  lagged  behind  Australia  and  Britain  in  radio  astronomy.41 

American  backwardness  in  radio  astronomy  was  widely  accepted  in  the  1960s  by 
those  involved  in  its  funding.  For  example,  in  a  speech  marking  the  dedication  of  the 
NRAO  43-meter  (140-ft)  radio  telescope  in  1965,  Leland  J.  Haworth,  director  of  the 
National  Science  Foundation,  emphasized  the  Australian,  British,  and  even  Dutch  lead 
over  the  United  States  in  entering  the  field.42  While  this  was  neither  the  first  nor  the  last 
time  that  a  scientific  community  would  use  backwardness  to  argue  for  financial  support, 
Cold  War  competition  was  not  mentioned. 

As  the  federal  agency  underwriting  much  of  the  country's  astronomy  research,  and 
as  the  sponsor  of  the  NRAO,  the  National  Science  Foundation  (NSF)  took  an  avid  inter- 
est in  radio  astronomy  and  its  telescopes.  In  December  1959,  well  before  the 
Congressional  investigation  of  Sugar  Grove,  the  NSF  had  appointed  an  Advisory  Panel  for 
Radio  Telescopes  to  appraise  current  and  future  needs  for  radio  telescopes.  Its  report, 
released  in  1961  before  the  Sugar  Grove  fiasco  was  generally  realized,  did  not  favor  the 
construction  of  large  dish  antennas.  Instead,  the  Panel  endorsed  arrays  using  aperture 
synthesis,  a  new  technique  first  developed  by  Martin  Ryle  in  Britain.  The  endorsement  of 
arrays  led  immediately  to  initial  design  studies  of  the  Very  Large  Array  (VLA) ,  located 
eventually  in  New  Mexico.  The  NSF  Panel  report  had  more  bad  news  for  radar  astronomy 
dishes.  Its  first  resolution  stated  that  antenna  requirements  for  radio  and  radar  astrono- 
my were  so  different,  that  radio  astronomy  antennas  "should  be  primarily  designed  to 
meet  the  needs  of  passive  [radio]  astronomy."43 


The  Whitford  Report 


Radio  astronomers  clamored  for  more  telescopes.  Anyone  interested  in  building  a 
new  radio  and/or  radar  telescope  dish  had  to  take  into  consideration  the  question  of  par- 
abolic dishes  versus  arrays,  which  were  still  quite  experimental  and  untested,  at  least  in  the 
United  States.  The  NSF  was  on  center  stage  as  the  primary  civilian  funding  agency  for 
radio  astronomy,  and  all  design  concepts  and  funding  requests  had  to  deal  with  the 
omnipresent  wake  of  the  Sugar  Grove  disaster.  The  future  of  large  radio  and  radar  dishes 
seemed  precarious. 

Into  this  situation  came  the  Committee  on  Government  Relations  of  the  National 
Academy  of  Sciences.  At  the  suggestion  of  Harvard  astronomer  Leo  Goldberg,  the 
Committee  created  the  Panel  on  Astronomical  Facilities  on  14  October  1963,  in  order  to 
outline  a  planned  approach  to  radio  and  optical  telescope  construction.  Panel  member- 
ship comprised  prominent  optical  and  radio  astronomers;  Albert  E.  Whitford  of  Lick 
Observatory  served  as  chair. 


41 .  U.S.  Congress,  House,  Committee  on  Science  and  Astronautics,  Subcommittee  on  Applications  and 
Tracking  and  Data  Acquisition,  Report  on  Radio  and  Radar  Astronomy,  87th  Cong.,  2d  sess.,  1962. 

42.  "Dedication  of  new  140-foot  radio  telescope  at  the  National  Radio  Astronomy  Observatory,  Green 
Bank,  West  Virginia,"  remarks  by  Dr.  Leland  J.  Haworth,  13  October  1965,  "Speeches,  Leland  I.  Haworth," 
NSFHF. 

43.  Geoffrey  Keller,  "Report  of  the  Advisory  Panel  on  Radio  Telescopes,"  The  Astrophysical Journal  134 
(1961):  927-939. 


70  TO  SEE  THE  UNSEEN 


The  Panel  assembled  radio  astronomers  at  a  meeting  held  in  Washington  on  1  and 
2  November  1963  in  order  to  build  a  consensus.  The  result  of  the  meeting  and  the  Panel's 
deliberations  was  an  ambitious,  10-year  plan  of  optical  and  radio  telescope  construction. 
Nonetheless,  the  result  of  the  Panel's  work,  known  as  the  Whitford  Report,  omitted  radar 
and  solar  astronomy.  Solar  astronomers  protested  the  neglect  in  letter  after  letter.44 

The  Whitford  Report  specifically  rejected  solar  radar  as  too  costly,  but  completely 
neglected  planetary  radar  astronomy.  Radar  astronomers  did  not  protest.  NASA's  internal 
evaluation  of  the  Whitford  Report,  which  Nancy  Roman  prepared  after  consulting  with 
those  NASA  committees  and  subcommittees  responsible  for  developing  the  agency's 
astronomy  program,  advised  NASA  to  continue  its  support  of  radar  astronomy. 
Nonetheless,  she  wrote,  "We  do  not,  at  present,  foresee  NASA  support  for  the  construc- 
tion of  new  radar  facilities,  although  further  experience  with  radar  exploration  of  the 
solar  system  may  modify  this  conclusion."  In  general,  Roman  concluded,  "Support  of 
astronomy  is  the  province  of  the  National  Science  Foundation,"  and  the  program  of  tele- 
scope construction  proposed  by  the  Whitford  Report  was  "within  the  traditional  province 
of  the  National  Science  Foundation  which  should  continue  to  retain  responsibility  for 
them."  Although  Roman  suggested  that  NASA  deep  space  communications  instruments 
"should  incorporate  potential  use  by  radio  astronomers  in  their  design,"45  curiously  she 
did  not  mention  lending  their  use  for  radar  astronomy  experiments. 

Roman's  evaluation  summed  up  what  became,  for  all  practical  purposes,  the  NASA 
position  on  funding  radar  astronomy.  The  construction  of  ground-based  facilities  was  the 
responsibility  of  the  NSF;  NASA  would  fund  mission-oriented  research  at  existing  facili- 
ties. The  NSF  embraced  its  role  as  the  federal  agency  with  primary  responsibility  for 
ground-based  astronomy.  But  full  implementation  of  the  Whitford  Report  construction 
program  required  substantial  increases  in  NSF  spending  on  ground-based  astronomy,  and 
the  Foundation  already  was  the  country's  major  underwriter  of  ground-based  astronomy. 
In  fiscal  1966,  of  the  total  federal  expenditure  of  $46.2  million  for  ground-based  astrono- 
my, the  NSF  share  was  $21.0  million  (46  percent),  compared  with  $9.4  million  (20  per- 
cent) for  NASA,  $8.0  million  (17  percent)  for  the  Air  Force,  $4.5  million  (10  percent)  for 
the  Navy,  and  $3.3  million  (7  percent)  for  ARPA.46 

The  Whitford  Report  proposed  to  spend  $224  million  (about  the  cost  of  Sugar 
Grove)  over  10  years  on  a  number  of  regional  and  national  facilities.  It  endorsed  1)  a  large 
array  as  a  national  facility  under  the  NRAO  (the  VLA);  2)  enlargement  of  Caltech's  Owens 
Valley  Observatory  (another  array);  3)  two  fully-steerable  91-meter  (300-ft)  dishes  as 
regional  facilities;  4)  a  design  study  of  the  largest  possible  steerable  dish;  and  5)  smaller, 
special  purpose  instruments.47 


44.  Material  in  folders  "Committees  &  Boards,  Committee  on  Science  and  Public  Policy,  Panels, 
Astronomical  Facilities,   1963,"  "ADM,  C&B,  COSPUP,  Panels,  Astronomical  Facilities,  Radio  Astronomers, 
Meetings,  Agenda,  Nov,"  "Committees  &  Boards,  Committee  on  Science  and  Public  Policy,  Panels,  Astronomical 
Facilities,  1964,"  and  "Committees  &  Boards,  Committee  on  Science  and  Public  Policy,  Panels,  Astronomical 
Facilities,  Report,  General,  1965,"  NAS;  Gerard  F.  W.  Mulders,  "Astronomy  Section  Annual  Report,"  25  June 
1963,  pp.  1-2,  and  Harold  H.  Lane,  "Astronomy  Section  Annual  Report,"  1  July  1964,  p.  1,  NSFHF;  Panel  on 
Astronomical  Facilities,  Ground-Based  Astronomy:  A  Ten-Year  Program  (Washington:  National  Academy  of  Sciences, 
1964),  p.  57. 

45.  Memorandum,  Roman  to  Associate  Administrator,  Office  of  Space  Science  and  Applications,  16 
March  1965,  "ADM,  C&B,  COSPUP,  Astronomical  Facilities  Rpt  Recommendations,  Assessment  by  NSF,"  NAS. 

46.  Haworth  to  Donald  F.  Hornig,  5  April  1965,  "Committees  &  Boards,  Committee  on  Science  and 
Public  Policy,  Panels,  Astronomical  Facilities,  Report,  Recommendations,  Assessment  by  NSF,   1965,"  NAS; 
"Astronomy  Section  Annual  Report,  1966,"  p.  1,  "MPS  Annual  Reports,"  NSFHF. 

47.  Harold  H.  Lane,  "Astronomy  Section  Annual  Report,"  1  July  1964,  p.  2,  NSFHF;  Ground-Based 
Astronomy,  pp.  50-57.  In  1955,  Caltech  began  building  a  radio  interferometer  consisting  of  two  90-foot  dishes  at 
Owens  Valley,  California,  funded  by  the  U.S.  Office  of  Naval  Research.  Robertson,  pp.  120-121;  Marshall  H. 
Cohen,  "The  Owens  Valley  Radio  Observatory:  Early  Years,"  Engineering  and  Science  57  (1994):  8-23. 


STURM  UND  DRANG  71 


The  Whitford  Report  favored  neither  arrays  nor  dishes,  but  saw  a  need  for  both.  As 
for  large  dishes,  the  Report  recalled  the  Sugar  Grove  fiasco:  "The  design  and  evaluation 
of  these  solutions  are  costly  and  very  time-consuming,  as  has  been  shown  in  the  unsuc- 
cessful attempt  at  Sugar  Grove  to  build  a  600-foot  [183-meter]  paraboloid."  The  Report 
expressed  the  need  for  "a  thorough-going  engineering  study"  to  ensure  the  construction 
of  large  radio  telescopes  and  recommended  spending  $1  million  on  design  studies  for  the 
largest  feasible  steerable  paraboloids  "at  an  early  date."48 


In  Dish/Array 


The  Whitford  Report  understandably  excited  both  Harvard  radio  astronomers  and 
Lincoln  Laboratory  radar  astronomers  with  its  endorsements  of  design  studies  for  large 
steerable  antennas  and  a  regional  91-meter  (300-ft)  dish.  In  order  to  seize  the  opportuni- 
ties created  by  the  Whitford  Report,  Harvard,  MIT,  and  the  SAO  agreed  to  undertake  a 
joint  study  of  a  large  radio  and  radar  telescope,  and  in  August  1965,  the  group  adopted 
the  name  Cambridge  Radio  Observatory  Committee  and  the  acronym  CAMROC.49 

In  October  1965,  when  CAMROC  drew  up  a  research  agenda  for  the  regional  tele- 
scope, planetary  and  lunar  radar  astronomy  were  featured  uses.  As  Ed  Lilley  argued: 
"American  radar  astronomers  have  also  made  major  contributions,  but  in  many  instances 
their  work  has  been  accomplished  by  'borrowing  time'  on  antennas  which  were  mission 
oriented.  In  the  Cambridge  group  there  are  radar  scientists  who  are  keenly  interested  in 
basic  radar  astronomy.  They,  too,  need  an  instrument  as  powerful  and  timely  as  the 
Palomar  200-inch,  where  radar  astronomy  can  flourish  as  a  basic  science  with  transmitters 
and  data  analysis  systems  developed  for  optimum  performance  on  ionospheric,  lunar, 
planetary,  and  solar  problems."50 

On  29  October  1965,  Harvard,  MIT,  Lincoln  Laboratory,  and  the  SAO  signed  a 
Memorandum  of  Agreement,  authorizing  CAMROC  to  solicit  up  to  $2.5  million  to  sup- 
port design  studies  for  the  telescope.  MIT  would  hold,  administer,  and  disburse  the  funds 
and  act  as  CAMROC's  administrative  agent.  CAMROC  funding  was  to  come  from  a  vari- 
ety of  sources,  mostly  federal.  Of  the  estimated  $2.7  million  needed  for  fiscal  1966  and 
1967,  the  NSF,  NASA,  and  the  Smithsonian  Institution  were  to  award  $1.57  million  (58 
percent).  MIT,  Harvard,  and  private  foundations  (Kettering  and  Ford)  would  provide 
additional  funding.51 

The  NASA  money  was  to  come  through  the  Electronics  Research  Center  in 
Cambridge.  Unaware  of  NASA's  evaluation  of  the  Whitford  Report,  CAMROC  submitted 
a  grant  proposal  to  NASA  for  design  studies  of  the  large  steerable  radio  and  radar 
antenna  in  February  1966.  NASA  rejected  the  proposal.  As  William  Brunk,  acting  chief  of 
Planetary  Astronomy,  explained,  "Support  for  a  project  such  as  this  is  within  the  domain 
of  the  National  Science  Foundation  and  it  is  recommended  that  they  be  approached  as  a 
possible  source  of  funding."  NASA  Deputy  Administrator  Robert  C.  Seamans,  Jr., 


48.  Ground-Based  Astronomy,  pp.  56  and  75;  "Assessment  of  the  recommendations  of  the  Whitford 
Report,  entitled  'Ground-Based  Astronomy:  A  Ten-Year  Program,'"  Table  V,  "ADM,  C&B,  COSPUP,  Astronomical 
Facilities  Rpt  Recommendations,  Assessment  by  NSF,"  NAS. 

49.  J.  A.  Stratton  to  S.  Dillon  Ripley,  14  May  1965,  and  Nathan  M.  Pusey  to  Stratton,  2  June  1965, 
5/1 /AC  135,  and  Minutes  of  Meeting,  26  August  1965,  14/1/AC  135,  MITA. 

50.  Lilley,  "Comments,"  p.  2-1,  PAHU. 

51.  Memorandum,  26  October   1965,   "CAMROC  Support  and  Budget,"  and  other  documents  in 
6/1/AC  135  and  12/1/AC  135,  MITA. 


72  TO  SEE  THE  UNSEEN 


repeated  the  message:  'The  type  of  effort  you  proposed  is  clearly  the  responsibility  of  the 
National  Science  Foundation."52 

Despite  the  clear  and  consistent  reply  from  NASA,  Joel  Orlen  of  MIT  and  executive 
officer  of  the  CAMROC  Project  Office  (which  was  in  charge  of  day-to-day  activities)  wrote 
to  Jerome  Wiesner,  MIT  provost,  "I  believe  NASA  should  be  pushed  on  hard  to  reverse  this 
decision."  CAMROC  members  came  to  believe  that  any  argument  made  to  NASA  had  to 
take  into  account  the  risk  of  offending  the  advocates  of  the  JPL  dish  design,  that  is,  the 
64-meter  (210-ft)  Mars  Station. 

Wiesner  wrote  to  Seamans,  requesting  that  NASA  reconsider  the  rejected  proposal; 
he  argued  that  the  technology  would  be  needed  in  the  space  effort.  Seamans  replied  that 
NASA  was  studying  a  variety  of  antenna  designs,  including  arrays,  "Because  we  foresee,  in 
an  active  and  continuing  space  program,  that  our  ground  facilities  will  be  required  to 
support  multiple  simultaneous  flight  missions,  it  may  turn  out  to  be  more  effective  to  rely 
on  a  grouping  of  antenna  systems  that  can  be  arrayed  together  as  needed  but  that  can  also 
operate  independently  for  independent  missions."53 

Seamans'  reply  threw  CAMROC  plans  into  disarray.  From  the  beginning,  the  tele- 
scope was  to  be  a  large  steerable  dish.  But  arrays  were  gaining  popularity  and  were 
considered  a  viable  alternative  to  large  radio  dishes.  The  Whitford  Report  had  endorsed 
both  the  Owens  Valley  array  and  the  VLA.  In  1955,  Caltech  began  building  a  pair  of 
27-meter  (90-ft)  dishes  at  Owens  Valley,  California,  with  money  from  the  Office  of  Naval 
Research;  now  Caltech  proposed  expanding  the  facility.  The  VLA  was  to  consist  of  27 
radio  telescopes  mounted  on  railroad  tracks  in  a  Y  formation  whose  arms  were  each  21 
km  long.  When  completed,  each  telescope  would  have  a  diameter  of  25  meters  (82  ft)  ,54 
Now,  NASA  appeared  interested  in  arrays.  But  were  arrays  effective  in  radar  astronomy? 

Believing  that  the  CAMROC  effort  would  raise  questions  about  the  merits  of  arrays 
versus  dishes,  radar  astronomer  and  CAMROC  member  Gordon  Pettengill  tackled  the 
question  in  a  memorandum  of  9  June  1966.  He  concluded  that  arrays  had  a  number  of 
advantages  over  a  single  large  dish,  including  the  ability  to  deliver  more  power  to  a  target. 
Arrays  stretched  technology  less,  promised  more  reliable  capability,  and  cost  less  to  build. 
If  some  array  elements  were  out  of  service  for  whatever  reason,  the  deficiency  would  hard- 
ly affect  overall  performance.  Moreover,  if  full  array  capability  were  not  needed,  the 
primary  array  could  be  divided  into  several  smaller  arrays  and  assigned  to  different  exper- 
iments. The  major  design  challenge  of  arrays,  Pettengill  pointed  out,  arose  from  proving 
the  practicality  of  phasing  a  number  of  elements  together.  A  minor  drawback  was  the  need 
for  numerous  low-noise  receivers  and  antenna  feeds.55 

Lilley  deflected  the  argument  away  from  the  merits  of  arrays  versus  dishes  by 
emphasizing  the  use  of  the  radome.  The  radome  set  the  design  apart  from  all  other  radio 
and  radar  antenna  proposals  before  the  NSF.  If  the  results  of  the  radome  tests  were  satis- 
factory, Lilley  claimed,  the  CAMROC  studies  would  provide  radio  and  radar  astronomy 
with  a  "breakthrough  in  antenna  technology,"  and  the  CAMROC  position  would  be 
unique.  "Unfortunately,"  he  lamented,  "only  a  small  fraction  of  the  radio  and  radar 


52.  "Proposal  to  the  National  Aeronautics  and  Space  Administration  for  Support  of  Design  Studies  for 
a  Large  Steerable  Antenna  for  Radio  and  Radar  Astronomy,"  February  1966,  55/1/AC  135,  and  "Project  Office 
Report  to  CAMROC,  Number  2,"  30  August  1966,  5/1/AC  135,  MITA;  William  E.  Brunk  to  Director,  Grants  and 
Research  Contracts,  28  July  1966,  NHOB. 

53.  Memorandum,  Joel  Orlen  to  Jerome  Wiesner,  7  September  1966,  Wiesner  to  Robert  C.  Seamans,  Jr., 
3  October  1966,  and  Seamans  to  Wiesner,  15  November  1966,  55/1/AC  135,  MITA. 

54.  For  background  on  the  VLA,  see  David  S.  Heeschen,  The  Very  Large  Array,"  Sky  and  Telescope  49 
(1975):  344-351;  and  A.  R.  Thompson,  R.  G.  Clark,  C.  M.  Wade,  and  P.  J.  Napier,  The  Very  Large  Array," 
Astrophysical  Journal  Supplemental  Series  44  (1980):  151-167.  The  initial  theoretical  development  of  arrays  is  dis- 
cussed in  Bracewell,  "Early  Work  on  Imaging  Theory  in  Radio  Astronomy,"  pp.  167-190  in  Sullivan.  See  also 
PA.G.  Scheuer,  The  Development  of  Aperture  Synthesis  at  Cambridge,"  pp.  249-265  in  ibid. 

55.  Memorandum,  Pettengill  to  CAMROC  Project  Office  File,  9  June  1966,  18/1/AC  135,  MITA. 


STURM  UNO  DRANG  73 


professional  scientists  in  the  United  States  understand  this,  and  it  is  unlikely  that  the 
National  Science  Foundation  administrators  have  a  clear  understanding  of  the  implica- 
tions of  the  CAMROC  studies."56 

Although  later,  in  April  1967,  the  NSF  did  judge  the  telescope's  unique  design 
feature  to  be  its  radome,57  in  the  meantime,  the  ability  of  the  NSF  to  fund  the  CAMROC 
telescope  was  limited.  Lilley  foresaw  "a  dramatic  expansion  of  demand"  for  federal  fund- 
ing, especially  from  the  NSF,  during  the  summer  of  1967  for  large  radio  astronomy  tele- 
scopes.58 Nonetheless,  the  NSF  became  the  largest  underwriter  of  the  CAMROC  design 
studies.  As  of  26  April  1966,  total  CAMROC  funds  amounted  to  $410,000.  The  largest 
share,  $300,000,  came  from  an  NSF  grant,  with  additional  money  from  Harvard 
($25,000),  the  SAO  ($20,000),  MIT  Sloan  Funds  ($40,000),  and  the  MIT  Space  Center 
($25,000) .  An  earlier  attempt  to  raise  money  from  the  Kettering  Foundation  failed.  The 
Foundation  was  shifting  its  funding  away  from  "science"  to  "education,"  and  the  CAMROC 
telescope  was  "marginal  to  their  interests."  The  likelihood  of  Department  of  Defense 
support  was  equally  bleak.59 

In  1966,  the  NSF  again  faced  a  considerable  number  of  large  radio  telescope  pro- 
posals, prompted  this  time  by  the  large-scale  spending  proposed  by  the  Whitford  Report. 
In  addition  to  the  CAMROC,  VLA,  and  Owens  Valley  antennas,  other  projects  included 
"WESTROC,"  a  joint  Caltech,  Stanford,  and  University  of  California  at  Berkeley  telescope. 
WESTROC  was  to  be  a  100-meter  (328-ft),  fully-steerable  S-band  radio  dish  located  at  the 
Owens  Valley  site. 

In  order  to  campaign  for  their  telescope,  CAMROC  held  a  Conference  on  Radomes 
and  Large  Steerable  Antennas  on  17  and  18  June  1966.  Over  70  persons  attended  the  con- 
ference, which  dealt  exclusively  with  the  proposed  CAMROC  dish.  Participants  came  from 
industry  (North  American  Aviation,  Rohr  Corporation,  ESSCO),  the  NSF,  the  NASA 
Electronics  Research  Center,  and  the  NRL,  as  well  as  from  MIT,  Harvard,  the  SAO,  and 
Lincoln  Laboratory.  Lilley  also  suggested  using  political  pressure.60  Ultimately,  CAMROC 
did  apply  political  pressure,  but  not  until  after  employing  other  tactics,  including  the 
expansion  of  CAMROC  into  a  regional  organization. 

NEROC 

At  least  as  early  as  February  1966,  CAMROC  was  considering  ways  of  transforming 
itself  into  a  regional  association.  The  chief  reason  for  the  undertaking  was  to  solicit  funds 
for  the  design,  construction,  and  operation  of  a  regional  radio  and  radar  telescope.  A 
regional  base,  moreover,  would  be  useful  in  competing  for  funds  against  the  Very  Large 
Array  or  WESTROC.61 


56.  Memorandum,  Lilley  to  Edward  M.  Purcell  and  Wiesner,  1  August  1966,  22/1/AC  135,  MITA. 

57.  "Report  of  the  Meeting  of  the  Advisory  Committee  for  Mathematical  and  Physical  Sciences,"  13-14 
April  1967,  p.  6,  NSFHF. 

58.  Memorandum,  Lilley  to  Purcell  and  Wiesner,  1  August  1966,  22/1/AC  135,  MITA. 

59.  CAMROC  Funds,  26  April  1966,  7/1/AC  135,  Orlen  to  Wiesner,  24  November  1965,  6/1/AC  135, 
and  various  documents  in  56/1 /AC  135,  MITA.  NSF  Grant  GP-5832  was  awarded  to  MIT  for  the  project  "Design 
Studies  for  a  Large  Steerable  Antenna  for  Radio  and  Radar  Astronomy."  For  materials  relating  to  the  proposal, 
see  12/1/AC  135  and  57/1/AC  135,  MITA. 

60.  Memorandum,  Lilley  to  Purcell  and  Wiesner,  1  August  1966,  22/1/AC  135,  and  various  documents, 
49/1 /AC  135,  MITA.  The  Institution  of  Electrical  Engineers  (London)  sponsored  a  Conference  on  Large 
Steerable  Aerials  for  Satellite  Communication,  Radio  Astronomy,  and  Radar,  on  6-28  June  1966.  Herb  Weiss, 
William  Fanning,  and  John  Ruze  from  Lincoln  Laboratory  presented  five  papers:  "Antenna  Tolerance  Theory: 
A  Review,"  "Design  Considerations  for  a  Large  Fully  Steerable  Radio  Telescope,"  "Performance  Measurements 
on  the  Haystack  Antenna,"  "Mechanical  Design  of  the  Haystack  Antenna,"  "Performance  and  Design  of  Metal 
Space-Frame  Radomes."  23/1 /AC  135,  MITA. 

61.  Memorandum,  Orlen  to  Wiesner,  8  February  1966,  7/1/AC  135,  MITA.  > 


74  TO  SEE  THE  UNSEEN 


CAMROC  reached  out  to  the  entire  Northeast  to  establish  itself  as  a  regional  orga- 
nization with  regional  interests,  and  with  justifiable  claims  to  funding  for  a  regional  radio 
and  radar  telescope.  One  of  the  first  steps  was  to  choose  a  name,  one  which  expressed  this 
regional  character.  The  new  organization,  called  the  Northeast  Radio  Observatory 
Corporation  (NEROC),  incorporated  in  Delaware  on  26  June  1967.  CAMROC  also  con- 
sidered a  number  of  corporate  arrangements,  including  the  possibility  of  remaining  lim- 
ited to  only  Cambridge  schools.  After  lengthy  discussion  and  analysis,  CAMROC  settled 
on  a  corporate  structure  that  combined  a  "reasonable  regional  image"  with  local  man- 
agement. A  committee  representing  qualified  users  would  determine  scientific  policy, 
while  actual  management  would  remain  in  the  hands  of  the  Cambridge  group.62 

After  a  detailed  study  of  university  astronomy  departments  in  the  six  New  England 
states,  the  five  adjacent  Midatlantic  states  (New  York,  New  Jersey,  Pennsylvania,  Maryland, 
and  Delaware),  and  Washington,  DC,  NEROC  recruited  its  first  members:  Boston 
University,  Brandeis  University,  Brown  University,  Dartmouth  College,  Harvard,  MIT,  the 
Polytechnic  Institute  of  Brooklyn,  the  Smithsonian  Institution,  the  State  University  of  New 
York  at  Buffalo  and  Stony  Brook,  the  University  of  Massachusetts,  the  University  of  New 
Hampshire,  and  Yale.63 

Among  the  universities  declining  the  NEROC  invitation  was  Cornell,  which  in  1967 
managed  the  world's  largest  radio  and  radar  antenna  at  Arecibo,  Puerto  Rico.  Franklin  A. 
Long,  vice  president  for  Research  and  Advanced  Studies  at  Cornell,  replied  to  the  MIT 
invitation  to  join  NEROC  on  27  June  1967.  Cornell  radio  astronomers  supported  the 
NEROC  initiative,  he  explained,  but  they  did  not  feel  the  telescope  deserved  top  priority. 
The  greatest  need  was  for  increased  resolution,  which  the  VLA  promised  to  deliver. 
Moreover,  they  were  "still  uncertain  about  the  relative  advantages  of  a  large  steerable  dish 
in  the  Northeast  as  compared  to  the  same  dish  in  the  Southwest  (or  Southeast)."  Having 
their  own  dish  as  well  as  an  international  agreement  to  use  facilities  overseas,  Cornell  was 
"concerned  as  to  whether  formal  participation  in  NEROC  would  not  carry  the  air  of 
excessive  Cornell  greediness  in  this  field."64 

As  CAMROC  transformed  itself  into  NEROC  in  1967,  the  business  of  securing  addi- 
tional funding  continued.  In  January  1967,  NEROC  won  a  third  NSF  grant  ($675,000)  for 
telescope  design  studies,  bringing  the  amount  of  total  NSF  support  to  $1,115,000. 
Nothing  guaranteed  the  continuation  of  NSF  support,  however;  the  Foundation  was  faced 
with  a  multitude  of  design  and  construction  proposals,  and  its  budget  was  limited.65 

In  April  1967,  the  NSF  Advisory  Committee  for  Mathematical  and  Physical  Sciences 
had  four  radio  astronomy  projects,  including  the  CAMROC  design  study,  under  consid- 
eration with  a  total  price  tag  of  $120  million.  Funding  for  all  four  was  not  available;  the 
Foundation  had  to  establish  which  ones  to  fund.  The  NSF  had  no  general  way  to  budget 
for  major  projects;  usually,  it  treated  requests  for  instrumentation,  design  studies,  or  facil- 
ities as  special  cases.66 


62.  "Outline  of  Organization  and  Management  of  Radio  Observatory,"  20  May  1966;  untitled  docu- 
ment, dated  May  1966;  and  "Alternative  Organizational  Arrangements,"  20  May  1966,  7/1/AC  135;  Agenda, 
CAMROC  meeting  of  15  June  1967,  8/1 /AC  135,  and  documents  in  61/1/AC  135,  66/1/AC  135,  and  67/1/AC 
135,  MITA;  NEROC,  Scientific  Objectives  of  the  Proposed  NEROC  Radio-Radar  Telescope  (Cambridge:  NEROC,  1967), 
p.  1;  Certificate  of  Incorporation,  22  June  1967,  "NEROC,"  LLLA.  The  annotated  agenda  of  the  first  meeting  of 
the  NEROC  Board  of  Trustees,  the  minutes  of  that  meeting,  the  certificate  of  incorporation,  and  the  NEROC 
by-laws  are  in  11/64/AC  118,  MITA. 

63.  Documents  in  8/1 /AC  135  and  65/1/AC  135,  MITA;  Certificate  of  Incorporation,  22  June  1967, 
and  "Qualifications  of  Northeastern  Institutions  for  CAMROC  Membership,"  22  March  1967,  "NEROC,"  LLLA. 

64.  Long  to  Wiesner,  27  June  1967,  and  Wiesner  to  James  A.  Perkins,  16  June  1967,  72/1/AC  135, 
MITA. 

65.  John  T.  Wilson  to  Howard  W.Johnson,  17January  1967,  8/1 /AC  135,  and  Seamans  to  Wiesner,  15 
November  1966,  55/1/AC  135,  MITA. 

66.  "Report  of  the  Meeting  of  the  Advisory  Committee  for  Mathematical  and  Physical  Sciences,"  13-14 
April  1967,  p.  7,  NSFHF. 


STURM  UNO  DRANG  75 


In  order  to  evaluate  the  four  radio  telescope  proposals,  the  NSF  appointed  the  Ad 
Hoc  Advisory  Panel  for  Large  Radio  Astronomy  Facilities,  called  the  Dicke  Panel  after  its 
chair,  Robert  H.  Dicke  of  Princeton  University.  By  June  1967,  when  the  Panel  convened, 
the  NSF  had  five  proposals  to  consider:  the  Owens  Valley  array,  the  VLA,  the  Arecibo 
upgrade,  the  NEROC  antenna,  and  the  WESTROC  dish. 

The  Dicke  Panel  met  in  Washington  between  24  and  28  July  1967  and  listened  to 
technical  presentations  from  members  of  the  proposing  institutions.  NEROC  was  asking 
for  $28  million  over  five  years  for  design  and  construction  of  a  fully-steerable,  radome- 
enclosed,  440-ft  (134-meter)  parabolic  dish  operating  at  6,000  MHz  (5-cm).  Gordon 
Pettengill  wrote  the  NEROC  presentation  section  on  radar  astronomy.  The  NEROC  tele- 
scope was  not  the  only  combined  radio  and  radar  astronomy  facility  looking  for  money. 
Thomas  Gold,  Frank  Drake,  and  Rolf  Dyce  of  Cornell  University  advocated  renovating  the 
Arecibo  dish  so  that  it  could  operate  at  3,000  MHz  (10-cm)  or  higher. 

Although  the  Dicke  Panel  had  focused  on  radio  astronomy,  it  was  not  blind  to  radar 
astronomy.  The  Panel  recognized,  for  example,  that  "the  use  of  radar  techniques  in 
astronomy  has  for  the  first  time  enabled  man  to  establish  direct  contact  with  the  planets 
and  to  set  his  own  experimental  conditions."  In  contrast  to  Pettengill's  memorandum  on 
radar  astronomy  arrays,  the  Dicke  Panel  judged  that  "an  array  cannot  be  used  effectively 
for  spectroscopic  work  or  radar  astronomy... without  introducing  great  complications  in 
the  electronic  system." 

Following  its  deliberations,  the  Dicke  Panel  submitted  its  report  to  the  Director  of 
the  NSF  on  14  August  1967.  The  report  approved  the  Owens  Valley  array,  the  VLA,  and 
the  Arecibo  upgrade.  To  say  the  least,  the  Dicke  Panel  was  impressed,  perhaps  too 
impressed,  by  the  potential  of  the  spherical  Arecibo  dish.  The  Arecibo  "type  of  antenna 
seems  to  show  great  promise  for  the  future  and  should  be  considered  along  with  the  very 
large,  fully  steerable  antenna  for  the  next  step  forward,"  the  Panel  ruled.  It  urged 
appraisals  of  Arecibo's  performance  and  suggested  that  both  the  WESTROC  and  NEROC 
proposals  be  deferred  until  more  was  known  of  the  performance  of  spherical  dishes.67  As 
we  shall  see  in  the  next  chapter,  the  Arecibo  antenna  was  considerably  inefficient. 

The  Dicke  Panel  report  devastated  NEROC  plans,  not  to  mention  planetary  radar 
astronomy  at  Lincoln  Laboratory.  The  only  radar  telescope  available  to  Lincoln 
Laboratory  investigators  was  the  Haystack  antenna.  The  Arecibo  305-meter  (1,000-ft)  dish 
and  JPL's  64-meter  (210-ft)  Mars  Station,  moreover,  already  outclassed  Haystack.  NEROC 
tried  to  salvage  its  antenna  project.  MIT  physics  professor  Bernard  F.  Burke  suggested  that 
NEROC  consider  a  smaller,  101-meter  (330-ft)  dish.  "We  should  not  be  so  beguiled  with 
the  idea  of  being  temporarily  the  master  of  the  world's  biggest  radio  telescope,"  he  wrote, 
"that  we  cannot  accept  an  instrument  that  is  only  one  of  the  biggest."68 

Technical  reports  and  symposia  papers,  though,  continued  to  support  the  feasibility 
and  desirability  of  the  134-meter  (440-ft)  design.  The  International  Symposium  on 
Structures  Technology  for  Large  Radio  and  Radar  Telescope  Systems,  sponsored  by  MIT 
and  the  Office  of  Naval  Research  and  held  at  MIT  on  18-20  October  1967,  saw  participants 
from  the  United  States  and  six  other  countries  discussing  the  latest  designs  for  large 


67.  National  Science  Board,  Approved  Minutes  of  the  Open  Sessions,  meeting  of  8  September  1967,  pp. 
113:14-113:15,  National  Science  Board;  "Draft  of  G.  Pettengill's  material  for  CAMROC  facilities  proposal,"  21 
April  1967,  62/2/AC  135,  and  NEROC,  "A  Large  Radio-Radar  Telescope:  Proposal  for  a  Research  Facility,"  June 
1967,  61/2/AC  135,  MITA;  "Report  of  the  Ad  Hoc  Advisory  Panel  for  Large  Radio  Astronomy  Facilities," 
14  August  1967,  typed  manuscript,  pp.  2-4,  9-10  and  13-14,  NSFL.  The  members  of  the  Dicke  Panel  were  Bart 

J.  Bok,  Stirling  A.  Colgate,  Rudolph  Kompfner,  William  W.  Morgan,  Eugene  N.  Parker,  Merle  A.  Tuve,  Gart 
Westerhout,  and  Robert  H.  Dicke. 

68.  Memorandum,  Burke  to  Lilley,  6  October  1967,  8/2/AC  135,  MITA. 


76  TO  SEE  THE  UNSEEN 


telescopes  in  Europe,  the  100-meter  (328-ft)  Effelsberg  antenna  and  the  proposed  122- 
meter  (400-ft)  dish  at  Jodrell  Bank.69 

Design  studies  for  the  NEROC  radio  and  radar  telescope  continued.  During  an  18- 
month  period  in  1966  and  1967,  an  interim  agreement  between  MIT  and  the  Air  Force 
partially  underwrote  the  studies.  Funding  at  Lincoln  Laboratory  tightened,  however,  and 
Herb  Weiss  learned  that  Lincoln  Laboratory  no  longer  could  pay  for  personnel  doing 
NEROC  studies  after  1  January  1968.  The  design  work  carried  on  thanks  to  modest  sup- 
port from  its  Cambridge  backers.  The  three  original  NEROC  members,  the  SAO,  MIT, 
and  Harvard,  contributed  $121,241,  of  which  MIT  and  Harvard  gave  84  percent.70 

The  NEROC  project  had  relied  on  the  technical  expertise  and  financial  largesse  of 
Lincoln  Laboratory,  plus  a  few  not  inconsequential  NSF  grants  worth  over  $1.6  million.  At 
this  critical  point,  as  Lincoln  Laboratory  "soft"  money  melted  and  the  Dicke  Panel  advised 
deferring  the  NEROC  telescope,  getting  more  time  on  the  Haystack  telescope  became  a 
higher  and  urgent  priority. 

HAYROC 

In  October  1967,  Lincoln  Laboratory  asked  NEROC  if  it  were  interested  in  assuming 
responsibility  for  Haystack.  NEROC  was  interested  and  wanted  to  study  costs  and  use 
management,  but  without  impairing  progress  on  the  design  of  the  134-meter  (440-ft) 
antenna.  As  funding  for  the  big  dish  design  studies  slowed  to  a  trickle  in  1968,  NEROC 
management  of  Haystack  began  to  look  even  more  desirable.  The  matter  was  the  first  item 
of  business  at  NEROC's  25  May  1968  meeting.  After  some  discussion,  NEROC  unani- 
mously voted  to  begin  negotiations  with  Lincoln  Laboratory  and  to  explore  sources  of 
financial  support  to  turn  Haystack  into  a  regional  observatory.71 

Air  Force  support  of  Haystack  paid  for  a  single  "shift,"  meaning  five  eight-hour  days 
a  week.  NEROC  radio  astronomers  wanted  more  observing  hours,  a  second  and,  if  possi- 
ble, a  third  "shift,"  that  is,  additional  increments  of  time  averaging  forty  hours  a  week.  In 
response  to  the  NEROC  interest,  Lincoln  Laboratory  offered  a  large  portion  of  its  current 
Haystack  schedule  to  NEROC  users  at  no  charge,  with  "overtime"  hours  at  minimal  cost 
beginning  January  1969.  In  stages,  NEROC  would  assume  responsibility  for  antenna  man- 
agement and  for  securing  operating  funds,  as  available  observing  time  increased  incre- 
mentally toward  a  maximum  schedule  of  four  and  a  half  shifts  (three  eight-hour  shifts 
each  day  plus  weekends  for  a  total  of  about  2,000  hours  per  year  for  each  shift) .  Lincoln 
Laboratory  still  would  be  an  important  user  of  the  antenna  and  would  continue  to  pro- 
vide substantially  to  the  operating  budget. 

NEROC  established  subcommittees  responsible  for  estimating  costs,  for  drawing  up 
mutually  agreeable  plans  between  Lincoln  Laboratory  and  its  sponsors  and  between 
NEROC  and  its  sponsors,  for  laying  out  a  management  structure,  and  for  pursuing  fund- 
ing. Among  the  funding  sources  explored  were  the  NASA  Electronics  Research  Center 
and  the  state  of  Massachusetts,  both  of  which  encouraged  further  discussions  but  cau- 
tioned that  eventual  support,  if  any,  would  be  in  modest  amounts.  In  addition,  NEROC 


69.  Documents  in  62/1/AC  135,  MITA.  For  the  Jodrell  Bank  440-foot  (134-meter)  MARK  V  telescope, 
see  Lovell,  The  Jodrell  Bank  Telescopes,  Chapters  5-6  and  9-11.  For  the  Effelsberg  telescope,  see  Otto  Hachenberg, 
"The  100-meter  Telescope  of  the  Max  Planck  Institute  for  Radio  Astronomy  in  Bonn,"  Proceedings  of  the  IEEE  61 
(1973):  1288-1295,  also  in  Mar  and  Liebowitz,  pp.  13-27,  which  are  the  proceedings  of  the  International 
Symposium  on  Structures  Technology  for  Large  Radio  and  Radar  Telescope  Systems. 

70.  Weiss  to  Wiesner,  21  September  1967,  18/2/AC  135,  and  documents  in  63/1/AC  135,  MITA.  MIT 
contributed  $72,381,  Harvard  $30,000,  and  the  SAO  $18,860;  NEROC  had  received  $1,615,000  from  the  NSF. 

71.  "Board  of  Trustees:  Second  Meeting  of  the  NEROC  Board  of  Trustees,  10/22/67,"  62/1/AC  135, 
and  "Board  of  Trustees:  Third  Meeting  of  the  NEROC  Board  of  Trustees,  5/25/68,"  63/1/AC  135,  MITA. 


STURM  UND  DRANG  77 


approached  MIT,  Harvard,  the  University  of  Massachusetts,  and  the  Environmental 
Science  Services  Administration  (for  a  very  long  baseline  interferometer  with  their  dish 
at  Boulder) .  The  NSF  was  not  left  out  of  the  search.72 

Meanwhile,  the  NEROC  134-meter  (440-ft)  antenna  project  had  languished.  Now, 
though,  the  Smithsonian  Astrophysical  Observatory  stepped  in.  The  SAO  had  not  con- 
tributed technically  to  the  design  of  the  big  dish,  nor  had  it  contributed  significantly  to  its 
financial  support.  But  the  SAO,  through  its  parent  organization,  the  Smithsonian 
Institution,  could  rally  political  support  and  make  claims  for  the  NEROC/Smithsonian 
telescope  being  a  national,  not  a  regional,  facility. 

The  possibility  of  the  Smithsonian  Institution  obtaining  Congressional  authorization 
for  the  NEROC  telescope  was  first  summarized  in  a  memorandum  to  the  NEROC  Board 
on  3  September  1967.  During  thje  summer  of  1968,  NEROC  and  Smithsonian  Institution 
representatives  discussed  the  possibility  of  the  Smithsonian  Institution  leading  the  drive 
to  obtain  funding  for  the  NEROC  telescope.  The  discussions  led  to  an  understanding, 
which  included  management  of  the  project  during  the  design,  construction,  and  opera- 
tional phases  of  the  facility.73 

As  a  pivotal  preliminary  step,  the  Smithsonian  Institution  organized  a  meeting  of 
radio  and  radar  astronomers  to  marshall  agreement  on  the  need  to  build  the  NEROC  tele- 
scope. If  the  meeting  of  radar  and  radio  scientists  endorsed  the  NEROC  telescope,  then 
the  Smithsonian  Board  of  Regents  would  be  asked  to  approve  the  attempt  to  obtain 
Congressional  authorization  for  it.  The  meeting  took  place  at  the  Museum  of  History  and 
Technology,  as  it  was  then  called,  at  Constitution  Avenue  and  14th  Street,  NW,  on  30 
November  and  1  December  1968.  About  three  dozen  invited  radio  and  radar  astronomers 
and  a  handful  of  NSF  and  NASA  officials  attended,  in  response  to  an  invitation  from  the 
Secretary  of  the  Smithsonian  Institution,  S.  Dillon  Ripley. 

After  Fred  Whipple  (Harvard)  opened  the  meeting  with  a  review  of  the  Smithsonian 
Institution's  "historical  role"  in  astronomy,  John  Findlay  (NRAO)  explained  the  purpose 
and  plan  of  the  meeting  and  pointed  out  that  five  years  after  the  Whitford  Report,  none 
of  the  recommended  facilities  had  been  built.  Talks  and  discussions  covered  the  gamut  of 
telescope  questions,  including  the  Arecibo  spherical  dish  and  the  issue  of  using  arrays  for 
radar  astronomy. 

James  Bradley,  assistant  secretary  of  the  Smithsonian  Institution,  laid  out  the  plan 
that  his  institution  might  follow  and  assuaged  worries  about  staying  on  the  good  side  of 
the  NSF.  MIT's  Edward  M.  Purcell  reviewed  the  basic  design  concept:  a  1 34-meter-diame- 
ter  (440-ft-diameter)  dish,  enclosed  in  a  171-meter  (560-ft)  radome,  the  whole  costing 
about  $35  million.  Whipple  explained  that  the  telescope  would  be  a  national,  not  a 
regional,  facility,  and  assured  the  gathering  that  the  SAO  would  "absolutely  not"  dominate 
the  telescope's  planning  and  policy  committee. 

On  the  last  meeting  day,  Findlay  sought  to  bring  the  participants  together  in  agree- 
ment around  common  issues.  The  formal  "Conclusions  and  Recommendation,"  by  major- 
ity vote  of  the  participants,  declared  that  there  was  "an  urgent  need  for  a  large  filled- 
aperture  radio-radar  telescope  in  the  United  States  to  assist  in  the  solution  of  a  wide  range 


72.  NEROC,  Proposal  to  the  National  Science  Foundation  for  Programs  in  Radio  and  Radar  Astronomy 
at  the  Haystack  Observatory,  8  May  1970,  p.  V.2,  LLLA;  "Board  of  Trustees:  Third  Meeting  of  the  NEROC  Board 
of  Trustees,  5/25/68,"  63/1/AC  135;  "Board  of  Trustees:  Fourth  Meeting  of  the  NEROC  Board  of  Trustees, 
1/18/69,"  64/1/AC  135;  and  NEROC,  Proposal  to  the  National  Science  Foundation,  for  Research  Programs  in 
Radio  Astronomy  Using  the  Haystack  Facility,  for  the  period  1  July  1969  to  30  June  1970,  p.  4,  11/64/AC  118, 
MITA.  The  proposal  can  be  found  in  "Research  Proposals  in  Radio  Astronomy  Using  the  Haystack  Facility, 
7/1/69-6/30/70,"   23/2/AC    135,   and   "Operating   Expenses  for   the   NEROC   Haystack  Observatory, 
7/1/69-6/30/70,"  24/2/AC  135,  MITA. 

73.  Memorandum,  Lilley  to  NEROC  Board  of  Trustees,  21  November  1968,  Box  1,  UA  V  630.159.10, 
PUHA;  Documents  in  64/1/AC  135,  MITA. 


78 


TO  SEE  THE  UNSEEN 


of  important  problems  in  astronomy  and  astrophysics."  The  telescope  was  to  be  operated 
as  a  national  facility  and  located  "primarily  on  the  basis  of  scientific  and  technical  crite- 
ria." The  meeting  resolved  that  the  Smithsonian  Institution  should  submit  a  proposal  to 
the  appropriate  federal  agencies  and  carry  general  responsibility  for  the  funding,  design, 
construction,  and  operation  of  the  telescope.  Finally,  participants  approved  that  the 
"NEROC  design  for  a  134-meter  (440-ft)  telescope  in  a  radome  is  close  in  size  and  gener- 
al specifications  to  a  feasible  optimum  design,"  and  endorsed  it  as  the  basis  for  the  final 
design  of  the  Smithsonian  telescope.74 

The  meeting  was  an  unqualified  success.  James  Bradley  wrote  to  Ripley  after  the 
meeting:  "We  have  succeeded  in  gaining  the  support  of  thirty  astronomers  for  our  leg- 
islative proposal  to  authorize  the  design  and  construction  of  a  large-diameter,  radio-radar 
astronomical  antenna."75  The  conference  was  only  the  first  step  in  preparing  to  go  direct- 
ly to  Congress.  In  the  following  weeks,  the  Smithsonian  Institution  and  NEROC  assembled 
materials  for  the  campaign.  Among  those  materials  was  a  publicity  packet  that  included  a 
photograph  of  a  model  of  the  completed  dish.  Herb  Weiss  estimated  the  cost  of  the  facil- 
ity and  compared  the  costs  presented  in  the  NSF  proposal  of  June  1967  with  projected 
costs  based  on  June  1969  and  June  1970  starting  dates. 


PROPOSED  440-FOOT  VERTICAL  TRUSS  ANTENNA  IN  A  RADOME 


Figure  11 

Artist's  drawing  of  the  proposed  NEROC  440-foot  (134-meter),  rr.dome-enclosed,  fuUy-steerable  antenna.  This  and  other  draw- 
ings and  models  were  prepared  to  raise  funding  for  the  radiwadar  telescope.  Its  radar  was  to  operate  at  5  cm  (6,000  MHz  or 
6  GHz),  which  was  lower  than  Haystack  Observatory's  wavelength  of  3.8  cm  (7,750  MHz).  (Courtesy  of  MIT  Lincoln 
Laboratory,  Lexington,  Massachusetts,  photo  no.  259646-1.) 


74.  James  C.  Bradley,  Charles  A.  Lundquist,  and  Lilley,  draft  letter  to  all  regents,  20  November  1968,  and 
Memorandum,  Lilley  to  NEROC  Board  of  Trustees,  21  November  1968,  Box  1,  UA  V  630.159.10,  PUHA; 
"Minutes,  Radio  and  Radar  Astronomers  Meeting,"  pp.  1-5,  8-9,  11-12,  15-18  and  24,  "List  of  attendees  and 
observers,"  Attachment  1,  and  "Conclusions  and  Recommendations,"  61/137,  SIAUSC,  1959-1972;  J.  W.  Findlay, 
"Summary  of  a  meeting  to  consider  a  large  filled-aperture  radio-radar  telescope,"  1  December  1968,  "SAO  1968," 
217,  SIAOS,  SIA. 

75.  Memorandum,  Bradley  to  Ripley,  16  December  1968,  "SAO  1968,"  217,  SIAOS,  SIA. 


STURM  UNO  DRANG  79 


On  3  January  1969,  STAG  (Smithsonian  Telescope  Advisory  Group),  the  radio 
astronomy  advisory  committee  to  Dillon  Ripley,  met  at  Lincoln  Laboratory  and  reviewed 
detailed  drawings  of  the  design  and  the  latest  cost  estimate.  Meanwhile,  the  Smithsonian 
Institution  Board  of  Regents  approved  requesting  an  initial  $2  million  for  completing  the 
NEROC  design  and  authorized  acquiring  land  for  a  site.  The  next  step  was  to  ask  the 
Bureau  of  the  Budget  (BoB)  for  approval  to  include  the  $2  million  request  in  the 
Smithsonian  Institution  budget  for  fiscal  1970.  On  20  January  1969,  Ripley  submitted  the 
proposed  radio  telescope  legislation  to  the  director  of  the  BoB.76 

Although  the  intention  of  approaching  Congress  directly  was  to  circumvent  the  NSF 
review  process,  the  Smithsonian  Institution  kept  the  Foundation  informed.  Meanwhile,  in 
August  1968,  NEROC  submitted  a  proposal  to  the  Foundation  for  expanded  radio  astron- 
omy research  at  Haystack.  The  purpose  of  the  proposal  was  to  increase  radio  observing 
time  to  three  shifts.  It  also  included  a  three-year  plan  for  shifting  management  and  finan- 
cial responsibility  to  NEROC,  as  well  as  a  suggested  management  structure.  The  Haystack 
Scientific  Advisory  Committee,  consisting  of  MIT  and  Harvard  scientists,  would  assist  the 
observatory  director  in  approving  experiments.  Any  qualified  radio  astronomer  in  the 
United  States  could  request  time.77 

During  what  Haystack  director  Paul  B.  Sebring  characterized  as  "the  long,  silent 
interval  following  the  August  68  submission  of  the  transfer  plan"  on  14  March  1969, 
Lincoln  Laboratory,  MIT,  and  NEROC  concluded  an  interim  agreement  on  the  transfer 
of  Haystack  to  NEROC  and  established  the  Haystack  Observatory  Office  to  evaluate  and 
coordinate  experiment  proposals  and  to  serve  as  a  conduit  for  non-Lincoln  Laboratory 
auxiliary  funds  for  Haystack.78 

The  National  Science  Foundation  turned  the  NEROC  proposal  over  to  the  second 
Dicke  Panel,  which  met  in  June  1969,  nearly  a  year  after  NEROC  submitted  its  proposal. 
The  Panel  recommended  supporting  Haystack  radio  astronomy.  The  blessing  of  the  Dicke 
report  turned  into  a  one-year  NSF  grant  effective  15  September  1969.  The  grant  paid  for 
wages,  computer  time,  and  other  costs  associated  with  adding  two  more  shifts  of  observ- 
ing time.  Under  the  conditions  of  the  grant,  moreover,  the  Haystack  telescope  was  opened 
to  all  qualified  radio  astronomers  in  the  United  States,  subject  to  the  approval  of  the 
Haystack  Scientific  Advisory  Committee.79 

The  orderly  transition  of  Haystack  into  a  civilian  radio  observatory  appeared  on 
track,  until  a  military  auditor  balked  at  the  disparity  between  the  Department  of  Defense 
and  NSF  shares  of  Haystack  support.  The  NSF  had  bought  two-thirds  of  the  observing 
time  for  $200,000,  while  the  Air  Force  paid  about  $1.3  million  for  only  one-third.  The 


76.  Ripley  to  Haworth,  17  March  1969,  9/2/AC  135,  documents  in  10/2/AC  135,  12/2/AC  135,  and 
64/1/AC  135,  MITA.  Members  of  the  Smithsonian  Telescope  Advisory  Group,  18  February  1969:  John  W. 
Findlay,  NRAO,  Green  Bank;  Alan  H.  Barrett,  MIT;  Von  R.  Eshleman,  Stanford;  Richard  M.  Goldstein,  JPL;  Carl 
E.  Heiles,  UC  Berkeley;  John  D.  Krauss,  Ohio  State  University;  Frank  J.  Kerr,  University  of  Maryland;  A.  Edward 
Lilley,  Harvard;  Alan  T.  Moffet,  Caltech;  Gordon  H.  Pettengill,  Arecibo;  Irwin  I.  Shapiro,  MIT;  Harold  F.  Weaver, 
UC  Berkeley;  and  Gart  Westerhout,  University  of  Maryland.  "NEROC  Bd.  of  Trustees  Minutes,"  Box  2,  UA  V 
630.159.10,  PUHA. 

77.  NEROC,  Proposal  to  the  National  Science  Foundation,  for  Research  Programs  in  Radio  Astronomy 
Using  the  Haystack  Facility,  for  the  period  1  July  1969  to  30  June  1970,  pp.  1-2  and  4-5,  11/64/AC  118,  MITA. 
The  proposal  also  can  be  found  in  "Research  Proposals  in  Radio  Astronomy  Using  the  Haystack  Facility, 
7/1/69-6/30/70,"   23/2/AC    135,   and   "Operating   Expenses  for   the   NEROC   Haystack   Observatory, 
7/1/69-6/30/70,"  24/2/AC  135,  MITA.  The  scientific  advisory  committee  consisted  of  Alan  H.  Barrett,  William 
A.  Dent,  A.  Edward  Lilley,  and  Irwin  I.  Shapiro. 

78.  Memorandum,  Sebring  to  M.  U.  Clauser,  21  November  1969,   12/56/AC  118,  and  "Haystack 
Observatory  Office,  Agreement  Establishing  the  H.O.O.,  3/14/69,"  31/2/AC  135,  MITA. 

79.  "Report  of  the  Second  Meeting  of  the  Ad  Hoc  Advisory  Panel  for  Large  Radio  Astronomy  Facilities," 
15  August  1969,  p.  22,  NSFL;  Louis  Levin  to  Wiesner,  12  September  1969,  18/2/AC  135,  MITA;  NEROC, 
Proposal  to  the  National  Science  Foundation  for  Programs  in  Radio  and  Radar  Astronomy  at  the  Haystack 
Observatory,  8  May  1970,  p.  FV.3,  LLLA. 


80  TO  SEE  THE  UNSEEN 


arrangement  conflicted  with  a  Bureau  of  the  Budget  circular,  and  the  auditor  requested 
a  written  release  from  the  Air  Force  before  he  would  pass  on  the  funding  arrangement. 
Brig.  Gen.  R.  A.  Gilbert,  Air  Force  Systems  Command  director  of  laboratories,  refused  to 
sign  a  written  release;  such  a  waiver,  he  judged,  might  commit  the  Air  Force  to  under- 
writing Haystack  through  the  end  of  fiscal  1970,  a  position  he  felt  he  could  not  take.80 

The  Mansfield  Amendment  cut  this  Gordian  knot.  Formally  known  as  Section  203  of 
the  Fiscal  1970  Military  Procurement  Authorization  Act,  the  Mansfield  Amendment  com- 
pelled the  Pentagon  to  demonstrate  the  mission  relevance  of  basic  research  financed 
through  its  budget.  Specifically,  the  Amendment  stated:  "None  of  the  funds  authorized  to 
be  appropriated  by  this  Act  may  be  used  to  carry  out  any  research  project  or  study  unless 
such  project  or  study  has  a  direct  or  apparent  relationship  to  a  specific  military  function 
of  operations."  Sen.  Mike  Mansfield's  goal  had  been  to  rechannel  public  funding  for  sci- 
ence through  civilian  rather  than  military  agencies.81 

The  Air  Force  announced  its  intention  to  terminate  operation  of  Haystack  no  later 
than  1  July  1970.  The  Mansfield  Amendment  was  a  key  factor  in  that  decision.  Although 
the  Air  Force  expressed  its  willingness  to  cooperate  with  the  NSF  in  an  orderly  transfer, 
the  decision  brought  chaos.  With  no  Air  Force  money  after  1  July  1970,  Haystack  was  in  a 
perilous  financial  situation.  Sebring,  as  Haystack  director,  obtained  NSF  consent  to  repro- 
gram  its  grant  funds  to  defray  the  entire  cost  of  Haystack  radio  astronomy  operations.  A 
small  grant  from  the  Cabot  Solar  Energy  Research  Fund  supplemented  the  NSF  money.82 

The  early  withdrawal  of  the  Air  Force  hastened  agreements  on  Haystack  ownership, 
management,  and  finances.  The  Air  Force  transferred  Haystack  to  MIT,  which  already 
owned  the  land.  Haystack  personnel  remained  employees  of  MIT.  The  NEROC  Board  of 
Trustees  appointed  the  observatory  director,  who  reported  to  them  through  the  board 
chair.  NEROC  took  responsibility  for  Haystack  research  and  financing. 

To  continue  support  of  radio  astronomy  after  1  October  1970,  NEROC  submitted  a 
new  proposal  to  the  NSF  in  May  1970.  The  proposal  presented  three  alternative  funding 
levels,  but  the  NSF  awarded  less  than  that  requested  for  a  minimal  program.83 
Subsequently,  the  NSF  annually  renewed  its  support  of  Haystack  radio  astronomy.  The  suc- 
cessful transition  of  Haystack  from  military  to  civilian  funding  and  monitorship  ultimate- 
ly had  an  impact  on  the  NEROC/SAO  effort  to  fund  the  134-meter  (440-ft)  telescope 
through  Congress. 


The  Big  Dish  Bill 


On  28  January  1969,  Senators  Clinton  P.  Anderson  (D-N.M.),  Hugh  Scott  (R-Pa.), 
andj.  W.  Fulbright  (D-Ark.),  all  three  regents  of  the  Smithsonian  Institution,  introduced 
a  bill  in  the  Senate  (S.705)  "to  authorize  the  Smithsonian  Institution  to  acquire  lands  and 
to  design  a  radio-radar  astronomical  telescope  for  the  Smithsonian  Astrophysical 
Observatory  for  the  purpose  of  furthering  scientific  knowledge,  and  for  other  purposes."84 


80.  Brunk,  Memo  to  the  Files,  18  December  1969,  NHOB. 

81.  James  L.  Penick,  Jr.,  Carrol  W.  Pursell,  Jr.,  Morgan  B.  Sherwood,  and  Donald  C.  Swain,  eds.,  The 
Politics  of  American  Science  1939  to  the  Present,  rev.  ed.  (Cambridge:  The  MIT  Press,  1972),  pp.  338-349. 

82.  W.  D.  McElroy  to  Grant  Hansen,  5  May  1970,  18/2/AC  135,  Hurlburt  to  Sebring,  20  May  1970, 
18/2/AC  135,  and  Wiesner  to  Orlen,  16  July  1970,  16/2/AC  135,  MITA;  Hansen  to  Thomas  O.  Paine,  26 
February  1970,  NHOB. 

83.  NEROC,  Proposal  to  the  National  Science  Foundation  for  Programs  in  Radio  and  Radar  Astronomy 
at  the  Haystack  Observatory,  8  May  1970,  p.  IV.  1,  1 .1.1  A;  Wiesner  to  Wilbur  W.  Bolton,  Jr.,  15  October  1970, 
18/2/AC  135,  MITA. 

84.  Documents  in  "Radio-Radar  Telescope  Legislation,  91st  Congress,  7/1/69-12/31/69,"  60,  SIAOS, 
and  "SAO  1968,"  217,  SIAOS,  SIA;  "Congress  Gets  'Big  Dish'  Bill,"  Vol.  9,  No.  4  The  SAO  News  (March  1969): 
1  and  4,  24/1/AC  135,  MITA. 


STURM  UNO  DRANG  81 


A  STAG  meeting  of  2  April  1969  decided  the  site  for  the  NEROC  telescope.  After  set- 
tling upon  a  number  of  site  criteria,  STAG  limited  the  site  candidates  to  the  continental 
United  States,  a  decision,  Fred  Whipple  pointed  out,  which  led  "almost  inexorably  to  a 
final  selection  somewhere  in  the  southern  border  states  from  western  Texas  through  New 
Mexico  and  Arizona  into  California."85 

The  Smithsonian  legislation,  known  popularly  as  the  "Big  Dish"  bill,86  requested  $2 
million  for  the  fiscal  year  ending  30  June  1970.  The  bill  was  read  twice,  then  referred  to 
the  Senate  Committee  on  Rules  and  Administration.  On  17  November  1969,  Morris  K. 
Udall  (D-Arizona)  introduced  the  legislation  in  the  House  (H.  R.  14,837),  where  it  was 
referred  to  the  Committee  on  House  Administration. 

The  Big  Dish  bill  picked  up  approvals  from  NASA  and  the  NSF.  In  February  1969, 
John  Naugle,  NASA  associate  administrator  for  Space  Science  and  Applications,  gave  his 
blessing  to  the  bill:  'The  addition  of  such  a  radio-radar  telescope  as  a  national  facility 
would  satisfy  a  need  for  the  future  of  radio  astronomy  in  the  United  States."87  On  17 
March  1969,  Ripley  asked  LelandJ.  Haworth,  director  of  the  NSF,  for  his  institution's  sup- 
port of  the  Smithsonian  legislation.  The  NSF's  reply  came  in  the  form  of  an  invitation. 
Robert  Fleischer,  head  of  the  NSF  Astronomy  Section,  wrote  that  the  Dicke  Panel  would 
reconvene,  on  9-11  June  1969,  and  invited  NEROC  to  prepare  a  30-minute  presentation 
on  the  current  status  of  its  radome  design.88  If  the  Dicke  Panel  again  deferred  or  reject- 
ed the  NEROC  design  in  favor  of  another  project,  passage  of  the  Smithsonian  Institution 
bill  would  be  jeopardized. 

Two  years  had  passed  since  the  first  Dicke  Panel  met.  "A  need  that  was  then  urgent 
has  now  become  critical,'  the  second  Dicke  Report  declared.  "While  our  country  has 
stood  still,  Great  Britain,  the  Netherlands,  Germany,  and  India  have  started  new,  large 
radio  telescopes  and  several  are  essentially  complete  and  ready  for  operation."  The  Panel 
reaffirmed  the  need  to  upgrade  the  Arecibo  dish  and  supported  the  Owens  Valley  array 
and  the  Very  Large  Array.  As  for  the  NEROC  antenna,  the  second  Dicke  Panel  found  it 
"clear  that  this  instrument  is  not  only  feasible,  but  ready  for  final  design  and  construc- 
tion." The  Panel  recommended  that  "the  final  design  and  construction. ..be  started 
now.. .with  the  utmost  dispatch."  The  Panel  suffered  amnesia,  too;  its  report  claimed  that 
it  had  "highly  recommended  for  continuation"  of  the  NEROC  design  study  two  years  ear- 
lier. In  its  conclusions,  the  second  Dicke  panel  declared:  'The  urgent  need  for  such  a  tele- 
scope is  proven  beyond  doubt.  The  instrument  is  ready  to  go  into  the  construction  phase." 
Whether  funded  through  the  Smithsonian  Institution  or  the  National  Science 
Foundation,  "it  is  evident  that  this  instrument  should  be  operated  as  a  national  facility."89 

The  Dicke  Panel  report  was  released  on  15  August  1969.  Although  Congress  inter- 
preted the  report  as  supporting  the  Big  Dish,  the  Dicke  Panel  recommendations  neither 
changed  the  playing  field  in  Congress  nor  clarified  the  issues.  After  a  two-hour  hearing  on 
10  September  1969,  Rep.  Frank  Thompson,  Jr.,  (D-NJ),  chairman  of  the  Subcommittee  on 
Library  and  Memorials,  deferred  the  Big  Dish  legislation.  He  insisted  on  having  reports 


85.  Whipple  to  Bradley,  3  April  1969,  "Miscellaneous  Correspondence  and  Other  Material,"  Box  1,  UA 
V  630. 159. 10,  PUHA. 

86.  See,  for  instance,  "Biggest  Radio-Radar  Scope  Asked  for  U.S.,"  Washington  Evening  Star,  1  April  1969, 
p.  A15,  in  "Radar  Astronomy,"  NHO. 

87.  John  E.  Naugle  to  Richard  A.  Buddeke,  18  February  1969,  NHOB;   "Radio-Radar  Telescope 
Legislation,  91st  Congress,  7/1/69-12/31/69,"  60,  SIAOS,  SIA;  "SAO  1968,"  217,  SIAOS,  SIA;  "Congress  Gets 
'Big  Dish'  Bill,"  pp.  1  and  4,  24/1/AC  135,  MITA. 

88.  Robert  Fleischer  to  Wiesner,  20  May  1969,  18/2/AC  135,  and  Ripley  to  Haworth,  17  March  1969, 
9/2/AC  135,  MITA. 

89.  "Report  of  the  Second  Meeting  of  the  Ad  Hoc  Advisory  Panel  for  Large  Radio  Astronomy  Facilities," 
15  August  1969,  typed  manuscript,  pp.  1-3  and  15-17,  NSFL.  The  membership  of  the  second  Dicke  Panel  was 
the  same  as  the  first,  with  the  exception  of  Merle  A.  Tuve,  Carnegie  Institution  of  Washington,  who  was  unable 
to  attend. 


82  TO  SEE  THE  UNSEEN 


from  NASA,  the  NSF,  and  the  Department  of  Defense  before  holding  hearings.  After  the 
submission  of  the  reports,  hearings  were  set  for  15  September  1969,90  but  the  question  was 
not  settled  before  the  end  of  the  Congressional  session. 

House  hearings  took  place  on  29  July  1970,  after  Rep.  Thompson  reintroduced  the 
legislation  (H.  R.  13,024)  on  22  July  1970.  The  primary  hurdle  facing  the  bill  was  the  tight 
budget,  although  money  was  available  for  the  war  in  Vietnam.  As  Rep.  Thompson 
quipped:  "Maybe  if  we  could  get  this  [telescope]  in  the  Defense  budget  it  would  be  all 
right,  but  then  I  would  be  against  it."  In  April  1971,  Lilley  and  the  Smithsonian  Institution 
in  fact  did  consider  an  amendment  to  the  Big  Dish  bill  that  would  include  classified  Navy 
research  among  its  duties.91 

During  the  19  July  1970  hearings,  astronomers  argued  that  the  telescope  was  need- 
ed because  the  United  States  was  behind  the  rest  of  the  world  in  radio  astronomy.  At  no 
point,  however,  did  anyone  defend  the  telescope's  radar  research  program.  The  bill  went 
to  the  Subcommittee  on  Library  and  Memorials,  which  unanimously  voted  to  report  the 
bill  to  the  Committee  on  House  Administration  with  the  recommendation  that  it  be 
reported  to  the  Congress  for  enactment  into  law. 

The  BoB  torpedoed  the  Big  Dish  bill,  however,  citing  the  findings  of  a  special  NSF 
review  committee,  which  had  assigned  higher  priority  to  two  other  projects.  The  proposed 
expenditure,  moreover,  was  not  consistent  with  Nixon  Administration  efforts  to  limit  fis- 
cal 1970  funding  to  items  of  the  highest  priority  and  to  avoid  commitments  for  fiscal  1971 
and  beyond.  Among  other  issues,  the  BoB  pointed  out  that  the  bill  raised  basic  questions 
about  the  appropriate  roles  of  the  Smithsonian  Institution  and  the  NSF.92 

The  Big  Dish  bill  returned  to  Congress  in  March  1971.  On  31  March  1971,  Rep. 
Thompson  told  Dillon  Ripley  that  the  bill  would  go  through  the  House  'Vith  no  trouble."93 
The  Greenstein  Panel,  however,  stopped  the  bill.  Ripley  wrote  to  Sen.  Clinton  Anderson  on 
23  June  1971  advising  him  to  postpone  action  on  the  bill.  The  latest  incarnation  of  the 
Dicke  Panel,  chaired  by  Jesse  Greenstein,  Caltech  astronomy  professor,  was  going  to  rec- 
ommend three  facilities:  the  VLA,  a  large  centimeter-wave  antenna,  and  a  large  millimeter- 
wave  antenna.  It  also  was  going  to  recommend  that  the  VLA  be  started  first.  "In  view  of  the 
priorities  to  be  established  by  the  Committee,"  Ripley  wrote,  "it  does  not  seem  wise  to  seek 
authorization  now  for  the  Smithsonian  telescope.  The  three  projects  are  all  of  great  value 
to  radio-radar  astronomy  and  should  not  be  put  into  a  competition  for  limited  Federal 
funds.  If  the  array  project  is  authorized  on  a  reasonable  time-scale,  we  look  forward  to  a 
timely  resumption  of  our  efforts  with  you  on  the  large  Smithsonian  telescope."94 

The  saga  of  the  NEROC  radio-radar  telescope  ended  not  in  Congress,  but  within 
NEROC  itself.  Once  Haystack  was  opened  to  radio  astronomers  from  NEROC  and  other 
institutions,  thanks  to  funding  from  the  NSF,  pressure  to  build  the  NEROC  telescope 
eased.  NEROC  board  members  had  come  to  realize,  too,  that  the  Big  Dish  bill  was  a  lost 


90.  "Radio-Radar  Telescope  Legislation,  91st  Congress,  7/1/69-12/31/69,"  SIAOS,  60,  SIA;  "Statement 
by  Herbert  G.  Weiss  for  Congressional  Subcommittee  Hearings,  October  1969,"  9/2/AC  135,  MITA. 

91.  Transcript  of  Congressional  hearing  of  29  July  1970,  Subcommittee  on  Library  and  Memorials  of 
the  Committee  on  House  Administration,  pp.  381-382  and  393,  "Miscellaneous  Correspondence  and  Other 
Material,"  Box  1,  and  "Miscellaneous  Correspondence  and  Other  Material,"  Box  2,  UA  V  630.159.10,  PUHA. 

92.  Transcript  of  hearing,  pp.  381-382  and  393,  "Miscellaneous  Correspondence  and  Other  Material," 
Box  1;  Memorandum  for  the  record,  James  Bradley,  16  September  1969,  and  James  M.  Frey  to  Frank  Thompson, 
Jr.,  2  September  1969,  "Miscellaneous  Correspondence  and  Other  Material,"  Box  2,  UA  V  630.159.10,  PUHA; 

"SAO    Radio-Radar   Telescope,    1970,"   and   Ripley   to   Lucien   N.   Nedzi,    2  April    1971,   SIAOS,   61,   SIA; 
Memorandum,  Orlen  to  Wiesner,  4  February  1969,  9/2/AC  135,  MITA. 

93.  Ripley  to  Nedzi,  2  April  1971,  "SAO  Radio-Radar  Telescope,  1971,"  61,  SIAOS,  SIA. 

94.  Ripley  to  Anderson,  23 June  1971,  "440' Congress  Suspension,"  Box  1,  UAV630.159.10,  PUHA.  The 
subpanel  for  radio  telescopes  included  David  S.  Heeschen,  NRAO;  Geoffrey  R.  Burbidge,  UC  La  Jolla;  Bernard 
F.  Burke,  MIT;  Frank  Drake,  Cornell;  Gordon  Pettengill,  MIT;  and  Gart  Westerhout,  University  of  Maryland. 


STURM  UND  DRANG  83 


cause.  In  addition,  radio  astronomy  was  changing;  millimeter  frequencies  were  the  newest 
frontier.  So  at  an  ad  hoc  meeting  of  25  April  1972,  Ed  Lilley  and  the  other  NEROC  mem- 
bers voted  to  terminate  the  Big  Dish  project.  Instead,  NEROC  would  concentrate  on  an 
NSF  proposal  to  upgrade  Haystack,  so  that  it  could  operate  at  a  wavelength  of  three 
millimeters.95 

In  retrospect,  Herb  Weiss,  who  voted  at  the  ad  hoc  meeting,  reflected  on  the  demise 
of  the  NEROC  project:  "It's  very  difficult  to  judge  the  absolute  priorities;  it's  a  moving  ter- 
ritory. I  really  felt  that  the  country  made  the  wrong  decision  not  to  pursue  NEROC.  Even 
though  they  might  have  dragged  it  out,  they  might  have  done  something,  but  it's  such 
small  money  and  such  a  great  step  in  the  right  direction,  and  not  the  ultimate.  I  mean  you 
can  go  beyond  that,  but  it'll  take  a  long  time;  you've  got  to  get  new  materials."96 

For  planetary  radar  astronomy,  here  was  a  lesson  in  Big  Science.  The  need  for  the 
NEROC  telescope,  the  decision  to  design  and  build  it,  and  the  entrepreneurial  skills  and 
energy  to  push  the  project  all  came  from  radio  astronomers,  not  radar  astronomers. 
Piggybacking  onto  a  Big  Science  (radio  astronomy)  telescope  helped  to  overcome  many 
obstacles,  but  in  the  end,  the  loss  of  control  that  is  inherent  in  piggybacking  cost  radar 
astronomy  the  telescope.  Also,  the  episode  illustrated  that  ultimately  the  instrument 
needs  of  radio  and  radar  astronomers  can  be  inharmonious. 

Literally,  they  operate  at  different  wavelengths.  Whereas  radio  astronomers  found  a 
wavelength  of  three  millimeters  exciting,  planetary  radar  astronomers  could  not  operate 
at  such  short  wavelengths.  The  generation  of  sufficient  power  to  conduct  radar  experi- 
ments at  millimeter  wavelengths  was,  and  remains,  an  insurmountable  technological 
obstacle. 

The  Nadir  of  Radar 

Three  years  after  NEROC  voted  to  terminate  the  Big  Dish  bill,  all  planetary  radar 
stopped  at  Haystack;  Lincoln  Laboratory  was  out  of  the  planetary  radar  business.  The  last 
Haystack  planetary  radar  transmission  traveled  to  Mercury  on  22  March  1974.97  The  NSF 
supported  radio  astronomy  at  Haystack,  but  planetary  radar  depended  on  mission-orient- 
ed NASA  grants.  Topographical  studies  of  the  Moon  and  Mars  supported  the  Apollo  and 
Viking  missions.  In  an  exceptional  move,  when  the  hasty  departure  of  the  Air  Force  imper- 
iled the  telescope's  finances,  NASA  patched  together  the  required  amount  from  the 
NASA  Planetary  Astronomy,  Viking,  and  Manned  Spacecraft  Center  program  budgets.98 

The  obvious  explanation  for  the  end  of  planetary  radar  at  Haystack  is  that  the 
upgraded  Arecibo  telescope  outclassed  it.  Yet  reality  was  neither  so  obvious  nor  so  simple. 
The  upgraded  Arecibo  radar,  in  fact,  was  not  operational  until  almost  a  year  and  a  half 
after  Haystack  carried  out  its  last  planetary  radar  experiment.  Although  the  upgraded 
Arecibo  telescope  was  far  more  sensitive,  it  could  look  at  a  target  for  only  two  hours  and 
forty  minutes  at  best.  With  an  ability  to  track  targets  for  many  more  hours,  Haystack  could 


95.  Memorandum,  Lilley  to  Bradley,  1  May  1972,  "SAO  Radio-Radar  Telescope,  1971,"  61,  SIAOS,  SIA. 
Those  attending  the  meeting  included:  Alan  Barrett,  MIT;  Bernard  Burke,  MIT;  Irwin  Shapiro,  MIT;  Paul 
Scoring,  Haystack  and  Lincoln  Laboratory;  Edward  Purcell,  Harvard;  Herbert  Weiss,  Lincoln  Laboratory;  and 
Ed  Lilley,  Harvard  and  SAO. 

A  footnote  to  the  NEROC  story:  a  Haystack  upgrade  completed  in  January  1994  made  it  the  premier 
United  States  radio  observatory  at  3  millimeters.  An  NSF  review  of  Haystack  carried  out  in  the  summer  of  1994, 
only  months  after  the  NSF-funded  upgrade,  put  funding  for  Haystack  radio  astronomy  in  jeopardy.  Ramy  A. 
Amaout,  "NSF  Review  Puts  Funding  for  Haystack  in  Jeopardy,"  The  Tech\o\.  114,  no.  18  (5  April  1994):  1  and  9. 

96.  Weiss  29  September  1993. 

97.  Photocopy  of  Haystack  logbook  entry  provided  by  Richard  P.  Ingalls  and  Alan  E.  E.  Rogers. 

98.  Memorandum,  HenryJ.  Smith,  15  December  1969,  and  memorandum,  Brunk  to  Distribution  List, 
10  June  1970,  NHOB. 


84 


TO  SEE  THE  UNSEEN 


compensate  for  its  lack  of  sensitivity  by  increasing  signal  integration  time.  Hardware  alone 
was  not  the  only  reason  for  the  end  of  planetary  radar  at  Haystack. 

Haystack  radar  use,  heavy  at  first,  did  not  stop  suddenly  in  1974,  but  declined  grad- 
ually over  the  years.  In  1970,  radar  accounted  for  about  a  third  of  observing  time,"  far 
more  than  at  Arecibo  or  JPL.  An  optimistic  NEROC  proposal  submitted  to  the  NSF  in 
1971  stated:  "It  is  believed  that,  for  the  next  several  years,  the  Planetary  Radar  instru- 
mentation should  continue  to  occupy  the  Haystack  antenna  for  roughly  40  to  50  percent 
of  the  available  time."100  In  fact,  the  actual  total  antenna  time  (exclusive  of  maintenance 
and  improvements)  for  planetary  radar  observing  fell  from  17  percent  in  1971  to  14  per- 
cent in  1972,  then  to  12  percent  in  1973.101 

Part  of  the  problem  was  intense  competition  among  radio  astronomers  for  telescope 
time.  The  search  for  molecular  spectral  lines  was  frenetic  and  intensely  competitive. 


Figure  12 

The,  Haystack  Observatory  planetary  radar  box.  Technicians  preparing  the  box  for  an  experiment  suggest  the  size  of  the  box.  A 
large  forklift  truck  raised  the  box  into  position  on  the  telescope.  (Courtesy  of  MIT  Lincoln  Laboratory,  Lexington, 
Massachusetts,  photo  no.  PI 0.29-1 785.) 


99.  Sebring  to  Hurlburt,  27  March  1970,  18/2/AC  135,  MITA.  In  March  1970,  for  example,  of  the  290 
hours  scheduled,  90  (31  percent)  were  spent  on  radar  observations. 

100.  "Plan   for  NEROC  Operation   of  the   Haystack  Research   Facility  as   a  National   Radio/Radar 
Observatory,  7/1/71-6/30/73,"  26/2/AC  135,  MITA. 

101.  NEROC,  Semiannual  Rej>ort  of  the  Haystack  Observatory,  15  January  1972,  p.  1;  ibid.,  15  July  1972,  p.  1; 
ibid.,  15  January  1973,  p.  1;  and  ibid.,  15  August  1975,  p.  iii,  MITA.  For  the  12  month  period  January  through 
December  1973,  out  of  5,462.5  hours  of  total  scientific  use,  planetary  radar  accounted  for  658  hours,  or  about 
12  percent.  "Haystack  Notes  June  73-Dec  74,"  SEBRING. 


STURM  UND  DRANG  85 


Although  Haystack  installed  radio  astronomy  equipment  on  the  planetary  radar  box  in 
early  1970  to  increase  observing  time  for  radio  astronomers,  complaints  about  the  box 
continued.  Indeed,  the  planetary  radar  box  could  sit  on  the  antenna  for  months  at  a  time. 
In  the  second  half  of  1972,  for  example,  planetary  radar  work  kept  the  box  on  the  anten- 
na from  13  July  to  24  September  and  from  9  October  to  12  November.102  As  radar 
astronomer  Gordon  Pettengill  reflected,  "It  wasn't  convenient  to  make  a  change  for  a  few 
hours  from  one  box  to  another,  and  that's  what  really  did  it  [Haystack]  in  I  think."103 

Another  factor  was  NASA's  decision  to  not  fund  research  facilities.  As  the  Air  Force 
began  withdrawing  financial  support  from  Haystack,  NASA  seemed  to  be  a  natural  source 
of  at  least  some  operational  funding.  In  his  reply  to  the  Air  Force,  NASA  Deputy 
Administrator  George  M.  Low  explained  that  at  NASA,  "We  consider,  however,  that  with- 
in the  present  budgetary  limitations  and  compared  to  other  ongoing  programs,  the 
research  programs  that  could  be  performed  at  the  Haystack  Facility  have  too  low  a  prior- 
ity to  claim  NASA  support  of  the  overall  operational  cost  of  the  Facility."  If  another  agency 
were  to  provide  general  operational  support,  NASA  would  be  happy  to  underwrite  spe- 
cific, mission-oriented  research,  such  as  the  topographic  studies  of  Mars  and  the  Moon.104 

The  Haystack  radar  transmitter  klystron  tubes,  without  which  planetary  radar  could 
not  be  carried  out,  suffered  from  internal  arcing  on  occasion.  "At  times,"  Haystack 
Associate  Director  Dick  Ingalls  explained,  "it  was  hairy."105  In  1973,  Haystack  asked  NASA 
for  a  replacement  klystron  tube.  NASA  refused,  accepting  the  risk  that  klystron  failure 
meant  the  end  of  planetary  radar  research.106  Of  the  two  NASA  missions  for  which 
Haystack  conducted  planetary  radar  research,  Apollo  and  Viking,  Apollo  was  over  by 
1973.  Once  Haystack  radar  data  ceased  serving  the  needs  of  the  Viking  mission,  NASA  no 
longer  had  any  mission  interest  in  Haystack  planetary  radar  research.107 

Thus,  temperamental  klystrons,  complaints  from  radio  astronomers,  the  end  of 
NASA  mission  funds,  and  NASA's  policy  of  not  funding  facility  operations  all  contributed 
to  bring  Haystack  planetary  radar  to  its  nadir  and  demise.  Despite  that  demise  and  the 
fate  of  the  NEROC  telescope,  planetary  radar  astronomers  at  Lincoln  Laboratory  and 
MIT  were  not  without  an  instrument.  The  future  was  at  the  Arecibo  Observatory. 


102.  Sebring  to  Hurlburt,  27  March  1970,  18/2/AC  135;  NEROC,  Semiannual  Report  of  the  Haystack 
Observatory,  15  August  1975,  p.  iii;  and  ibid.,  15  January  1972,  p.  1,  MITA.  Also,  see  the  references  to  complaints 
by  radio  astronomer  William  A.  Dent  in  Memorandum,  Sebring  to  Haystack  Observatory  Office  Members, 
2  February  1971,  44/2/AC  135,  MITA. 

103.  Pettengill  28  September  1993. 

104.  George  M.  Low  to  Grant  L.  Hansen,  2  April  1970,  NHOB. 

105.  Ingalls  5  May  1994. 

106.  Memorandum,  Brunk  to  Joyce  Cavallini,  25  July  1973,  NHOB. 

107.  Haystack  Observatory,  Final  Progress  Report:  Radar  Studies  of  the  Planets  (Westford:  NEROC,  29  August 
1974).  This  was  for  NASA  grant  NGR-22-174-003. 


Chapter  Four 

Little  Science/Big  Science 

Lincoln  Laboratory  was  not  the  only  center  where  planetary  radar  took  root.  Cornell 
University  had  its  Arecibo  Observatory;  JPL  had  its  Goldstone  facility.  At  each  center, 
radar  astronomy  developed  in  the  shadow  of  military,  space,  radio  astronomy,  and  iono- 
spheric Big  Science.  In  fact,  without  those  Big  Science  activities,  planetary  radar  astrono- 
my would  not  have  had  instruments  to  carry  out  research  and,  in  short,  would  not  have 
existed. 

In  1961,  when  the  first  successful  detections  of  Venus  took  place,  virtually  the  sole 
funder  of  planetary  radar  astronomy  in  the  United  States  was  the  military.  The  one  excep- 
tion was  JPL's  Goldstone  facility,  which  NASA  funded.  Ten  years  later,  the  NSF  took  over 
the  role  of  prime  underwriter  of  the  Arecibo  Observatory  from  ARPA,  and  NASA  agreed 
to  support  a  major  S-band  upgrade  of  the  facility's  radar.  As  a  result,  NASA  became  the 
de  facto  patron  of  planetary  radar  astronomy  at  Arecibo,  Goldstone,  and  Haystack.  NASA 
supported  planetary  radar  at  those  three  centers  through  a  variety  of  financial  arrange- 
ments. Only  at  Arecibo,  however,  did  NASA  formally  agree  to  support  a  planetary  radar 
facility,  as  well  as  the  research  conducted  with  it.  That  agreement,  moreover,  was  an  obvi- 
ous departure  from  its  policy  formulated  in  the  wake  of  the  Whitford  Report. 

The  shift  from  military  to  civilian  sponsorship  at  Arecibo,  just  as  in  the  case  of 
Haystack,  was  not  in  response  to  the  Mansfield  Amendment.  Under  the  Kennedy 
Administration,  the  military,  mainly  the  Office  of  Naval  Research,  already  had  started 
transferring  research  laboratories,  especially  nuclear  physics  facilities,  to  the  NSF.  The 
budgetary  reforms  introduced  under  Defense  Secretary  McNamara,  whose  first  major 
reform  was  to  make  the  DoD's  budget  reflect  the  military  missions  for  which  it  was  respon- 
sible, probably  provided  the  initial  impetus  to  those  transfers.1 

The  emergence  of  NASA  as  the  patron  of  planetary  radar  astronomy  is  obvious  only 
in  hindsight.  Throughout  the  1960s,  NASA  refused  to  fund  radar  construction,  except  for 
the  Deep  Space  Network.  The  NSF  was  the  prime  underwriter  of  astronomy  facilities,  but 
did  not  support  planetary  radar  research.  Consequently,  during  the  1960s,  planetary 
radar  astronomers  depended  on  the  kindness  of  Big  Science,  whether  the  radio 
astronomers  at  Haystack,  or  the  NASA  space  programs  at  Goldstone,  or  ARPA  (the  mili- 
tary sponsor  of  Arecibo) ,  for  its  instruments. 

But  in  1971,  NASA  broke  with  its  established  policy  and  paid  for  S-band  radar 
equipment  and  underwrote  the  research  conducted  with  it  at  Arecibo.  The  result  was  not 
just  a  new  NASA  policy  but  also  the  creation  of  a  permanent  institutional  and  financial 
home  for  planetary  radar  astronomy  that  the  field  lacked  elsewhere.  This  unique 
arrangement  came  about  through  the  complex  politics  of  science  typical  of  Big  Science 
facilities.  Complicating  relations  between  the  Arecibo  Observatory  and  its  parent  organi- 
zation, as  well  as  relations  with  its  funding  agency,  were  turf  battles  between  competing 
Big  Science  fields  (radio  astronomy  and  ionospherics)  and  personality  conflicts. 


1.  Emilio  Q.  Daddario,  "Needs  for  a  National  Policy,"  Physics  Today  22  (1969):  33-38;  James  E.  Hewes, 
Jr.,  From  Root  to  McNamara:  Army  Organization  and  Administration,  1900-1963  (Washington:  U.S.  Army  Center  of 
Military  History,  1975),  pp.  299-315. 

87 


88  TO  SEE  THE  UNSEEN 


The  Arecibo  Ionospheric  Observatory 

Cornell  University's  1,000-ft  (305-meter)  Arecibo  dish  began  as  a  UHF  radar  man- 
aged by  a  civilian  institution,  Cornell  University,  but  funded  by  the  military.  The  (Air 
Force)  Rome  Air  Development  Center  largely  funded  Cornell  ionospheric  research,  and 
the  original  purpose  of  the  Arecibo  telescope  was  to  conduct  ionospheric  research.  The 
Arecibo  facility  started  in  the  mind  of  William  E.  Gordon,  Cornell  professor  of  electrical 
engineering,  who  had  devised  a  new  incoherent  scatter  technique  for  studying  electrons 
in  the  upper  levels  of  the  ionosphere  by  bombarding  them  with  powerful  radar  waves.  He 
worked  on  the  technique  with  Cornell  electrical  engineering  colleagues  Henry  Booker, 
his  dissertation  advisor,  and  Ben  Nichols,  both  of  whom  shared  Gordon's  interest  in  iono- 
spheric research.  A  Cambridge  graduate,  Booker  had  worked  in  the  radio  section  of  the 
Cavendish  Laboratory,  and  during  World  War  II  he  led  the  theoretical  division  of  the 
radar  effort  at  the  Telecommunications  Research  Establishment.2 

In  order  to  apply  his  technique,  Gordon  realized  he  needed  a  powerful  radar,  which 
he  proposed  to  build  with  state-of-the-art  components.  Gordon  also  realized  that  the 
instrument  would  be  costly,  too  costly  to  have  a  single  purpose.  He  proposed,  therefore, 
that  it  also  do  radar  astronomy  experiments.  Henry  Booker  added  radio  astronomy,  a  field 
that  interested  him. 

Funding  for  the  initial  radar  design  studies,  completed  by  Gordon,  Booker,  and 
Nichols  in  December  1958,  came  from  the  military:  the  Office  of  Naval  Research,  the 
Rome  Air  Development  Center,  and  the  Aerial  Reconnaissance  Laboratory,  Wright  Air 
Development  Center,  Wright-Patterson  Air  Force  Base,  Ohio.  The  studies  outlined  the 
radar  parameters:  a  pulse  radar  with  2.5  megawatts  of  peak  power  and  150  kilowatts  aver- 
age power  (essentially  the  Millstone  radar  transmitter),  a  low  noise  temperature,  and  an 
operating  frequency  around  400  MHz  (430  MHz;  70  cm  in  the  final  design).  The  avail- 
ability of  components  and  antenna  technical  limits  largely  determined  the  operating  fre- 
quency. The  antenna  itself  was  to  be  a  parabolic  dish  305  meters  (1000  ft)  in  diameter 
fixed  in  a  zenith-pointing  position  and  fed  from  a  horn  on  a  152-meter  (500  ft)  tower.3 

Concurrent  with  these  design  studies,  Bill  Gordon  sought  funding.  The  budget  of 
the  NSF,  the  agency  of  choice  for  basic  research,  was  not  large  enough  for  the  project,  and 
NASA  was  interested  in  building  spacecraft.  The  National  Bureau  of  Standards  already 
had  built  ionospheric  radars  and  was  building  a  dipole  array  radar  in  Jicamarca,  outside 
Lima,  Peru,  that  incorporated  Gordon's  incoherent  scatter  technique.  Its  director,  Ken 
Bowles,  a  Cornell  graduate,  had  demonstrated  the  feasibility  of  Gordon's  technique  with 
a  Bureau  of  Standards  meteor  radar  in  Illinois. 

Gordon  first  presented  his  project  to  ARPA  in  the  summer  of  1958.  ARPA  was  an 
entirely  new  agency.  Although  Gordon  was  not  aware  of  it  at  the  time,  ARPA's  Defender 
Program  was  an  effort  to  research,  develop,  and  build  a  state-of-the-art  defense  against 


2.  Gordon  28  November  1994;  Benjamin  Nichols,  telephone  conversation,  14  December  1993; 
"Cornell  University  Center  for  Radiophysics  and  Space  Research,"  typed  manuscript,  12  August  1959,  Office  of 
the  Administrative  Director,  NAIC;  Gordon,  "Incoherent  Scattering  of  Radio  Waves  by  Free  Electrons  with 
Applications  to  Space  Exploration  by  Radar,"  Proceedings  of  the  IRE  46  (1958):  1824-1829;  George  Peter,  Evolution 
of  Receivers  and  Feed  Systems  for  the  Arecibo  Observatory  (Ithaca:  NAIC,  1993),  pp.  4-5;  SCEL  Journal Vol.  S-l,  no.  32 
(6  August  1953):  2,  "Signal  Corps  Engineering  Laboratory  Journal/R&D  Summary,"  HAUSACEC;  Gillmor, 
"Federal  Funding,"  p.  126. 

3.  Gordon  28  November  1994;  Benjamin  Nichols,  telephone  conversation,   14  December  1993; 
Gordon,  Booker,  and  Nichols,  Design  Study  of  a  Radar  to  Explore  the  Earth's  Ionosphere  and  Surrounding  Space, 
Research  Report  EE  395  (Ithaca:  Cornell  School  of  Electrical  Engineering,  1  December  1958),  pp.  1  and  10-11; 
Gordon,  Antenna  Beam  Swinging  and  the  Spherical  Reflector,  Research  Report  EE  435  (Ithaca:  Cornell  School  of 
Electrical  Engineering,  1  August  1959),  pp.  1  and  8;  CRSR,  Construction  of  the  Department  of  Defense  Ionospheric 
Research  Facility  -  Final,  Research  Report  RS  55  (Ithaca:  CRSR,  30  November  1963),  p.  2;  Gillmor,  "Federal 
Funding,"  p.  127. 


LITTLE  SCIENCE/BIG  SCIENCE  89 


Soviet  missiles.  Though  some  ARPA  scientists  saw  the  scientific  value  of  Arecibo,  ARPA's 
main  interest  in  the  project  was  as  part  of  the  Defender  Program  to  track  the  ion  trails  cre- 
ated by  missile  exhaust.4 

Gordon  campaigned  in  Washington  for  two  years.  The  Sugar  Grove  dish  was  a  bar- 
rier to  gaining  approval;  reviewers  wanted  to  know  why  he  needed  to  build  the  305-meter 
(1000-ft)  dish,  when  the  Navy  had  a  fully-steerable  antenna  under  construction.  Finally, 
Gordon  met  Ward  Low  of  the  Institute  for  Defense  Analysis  and  an  ARPA  adviser,  and 
ARPA  agreed  to  finance  the  engineering  and  construction  of  the  dish.  The  Air  Force 
Office  of  Scientific  Research  (AFOSR),  through  the  Electronics  Research  Directorate,  Air 
Force  Cambridge  Research  Laboratories  (AFCRL),  Bedford,  Massachusetts,  monitored 
the  contract.  The  AFCRL  now  influenced  the  design  of  the  telescope.  Low  introduced  Bill 
Gordon  to  the  AFCRL  antenna  group,  which  had  been  studying  spherical  reflectors  for 
over  a  decade.  They  redesigned  the  fixed,  zenith-looking  paraboloid  into  a  spherical 
reflector  with  a  movable  antenna  feed  mounted  on  a  suspended  platform.5 

The  antenna  was  larger  than  any  other  attempted  for  radar  or  radio  astronomy,  larg- 
er even  than  the  Sugar  Grove  dish.  The  size  required  an  unprecedented  support  struc- 
ture. Cornell  civil  engineering  professors  proposed  placing  the  dish  in  a  natural  bowl  in 
the  earth.  The  proposal  was  practical  from  an  engineering  perspective  and  cut  costs, 
according  to  preliminary  studies  by  William  McGuire  and  George  Winter,  Cornell  School 
of  Civil  Engineering. 

Topographical,  political,  and  scientific  factors  influenced  the  choice  of  a  site.  In  the 
tropics,  the  planets  would  pass  nearly  overhead  and  into  the  antenna's  cone  of  view.  After 
considering  sites  in  Hawaii,  central  Mexico,  Cuba,  Puerto  Rico,  and  some  smaller 
Caribbean  islands,  the  search  narrowed  to  the  Island  of  Kauai,  the  Matanzas  area  of  Cuba, 
and  northern  Puerto  Rico.  Political  and  import  problems  eliminated  Cuba;  Hawaii  was 
too  far  and  too  remote.  Puerto  Rico  had  a  favorable  location,  political  stability,  and  mini- 
mum distance,  as  well  as  a  karst  topography  full  of  sinkholes  in  which  to  locate  the  giant 
reflector.  After  looking  at  locations  in  Puerto  Rico,  Cornell  chose  a  natural  bowl  in  the 
mountains  south  of  the  city  of  Arecibo.6 

With  feasibility  and  location  established,  ARPA  and  Cornell  signed  a  contract  on  6 
November  1959  in  which  the  University  agreed  to  perform  three  tasks:  1)  conduct  design 
studies  on  a  vertically-directed  ionospheric  radar  probe;  2)  consider  ionospheric  and 
other  scientific  uses  for  the  instrument,  then  propose  a  priority  list  of  the  first  experi- 
ments; and  3)  lay  out  structures  and  buildings  needed  for  the  initial  facility.7 

Meanwhile,  also  in  1959,  Henry  Booker  launched  the  Center  for  Radiophysics  and 
Space  Research  (CRSR),  an  umbrella  organization  for  mainly  astronomy  and  electrical 
engineering  faculty  research,  as  well  as  management  of  the  Arecibo  facility.  Booker  shared 
its  administration  with  fellow  Cambridge  graduate  Thomas  Gold.  Like  Booker,  Gold  had 


4.  Gordon  28  November  1994;  Nichols,  telephone  conversation,  14  December  1993;  Jack  P.  Ruina, 
"Arecibo,"  Electronics  7  April  1961,  n.p.,  article  in  publicity  folder,  Office  of  the  Administrative  Director,  NAIC; 
CRSR,  Ionospheric  Research  Facility,  p.  2;  Herbert  F.  York,  Making  Weapons,  Talking  Peace:  A  Physicist's  Odyssey  from 
Hiroshima  to  Geneva  (New  York:  Basic  Books,  1987),  pp.  142-143;  Gillmor,  "Federal  Funding,"  p.  126. 

5.  Gordon  28  November  1994;  Philip  Blacksmith,  "DODIRF  1000-foot  Spherical  Reflector  Antenna," 
and  Alan  F.  Kay,  A  Line  Source  Feed  for  a  Spherical  Reflector,  Technical  Report  529  (Hanscom  AFB:  AFCRL,  29  May 
1961),  Phillips  Laboratory;  Roy  C.  Spencer,  Carlyle  J.  Sletten,  and  John  E.  Walsh,  "Correction  of  Spherical 
Aberration  by  a  Phased  Line  Source,"  Proceedings  of  the  National  Electronics  Conference  5  (1949):  320-333;  Gillmor, 
"Federal  Funding,"  p.  127. 

6.  Gordon  28  November  1994;  Gordon,  "Arecibo  Ionospheric  Observatory,"  Science  146  (2  October 
1964):  26;  Gordon,  "Arecibo  Ionospheric  Observatory,"  p.  26;  Gordon,  Booker,  and  Nichols,  pp.  12-13;  Donald 

J.  Belcher,  "Site  Locations  for  a  Proposed  Radio  Telescope,"  Appendix  C  in  ibidem;  R.  E.  Mason  and  W. 
McGuire,  The  Fixed  Antenna  for  a  Large  Radio  Telescope:  Feasibility  Study  and  Preliminary  Cost  Estimate," 
Appendix  B  in  ibidem. 

7.  CRSR,  Design  Studies  for  the  Arecibo  Radio  Observatory,  Research  Report  RS  9  (Ithaca:  CRSR,  30  June 
1960),  NAIC,  p.  1. 


90  TO  SEE  THE  UNSEEN 


worked  on  radar  during  World  War  II,  but  at  the  Admiralty  Research  Establishment.  After 
the  war,  Cambridge,  the  Cavendish  Laboratory,  and  the  Royal  Observatory  in  Greenwich, 
Gold  arrived  in  the  United  States  in  1957  and  taught  astronomy  at  Harvard.  Booker 
thought  Gold  ideal  for  running  the  CRSR.8 

The  CRSR  staff,  professors  from  the  astronomy,  electrical  engineering,  and  physics 
departments,  drew  up  a  research  program  for  the  Arecibo  telescope.  Following  ARPA 
guidance,  they  listed  20  experiments  arranged  in  order  of  priority.  The  first  three 
explored  the  ionosphere.  Then  came  proposals  for  planetary,  lunar,  solar,  and  other  radar 
work,  followed  by  three  more  ionospheric  experiments.  The  last  10  were  all  radio  astron- 
omy experiments.  The  first  10,  the  CRSR  staff  concluded,  were  "clearly  within  the  scope 
of  the  ARPA  missions,"  but  the  "relation  of  experiments  11  through  20  [in  radio  astrono- 
my] to  the  ARPA  mission  is  not  so  clear."  ARPA  did  not  appear  interested  in  radio  astron- 
omy. Well  before  the  telescope's  inauguration,  however,  radio  astronomy  had  been 
assigned  a  major  role  in  its  scientific  mission.9 

Cornell  next  began  building  the  Department  of  Defense  Ionospheric  Research 
Facility,  as  the  telescope  was  named  originally.  Construction  of  the  structure,  antenna, 
concrete  towers,  and  electronics  were  let  out  to  over  a  half  dozen  commercial  subcon- 
tractors, while  the  Army  Corps  of  Engineers  supervised  the  construction  and  civil  engi- 
neering. The  raising  of  the  300-ton  feed  platform  from  the  bottom  of  the  bowl,  where  it 
had  been  assembled,  to  its  approximate  final  position  152  meters  (500  ft)  overhead,  was 
an  awe-inspiring  sight.  As  Bob  Price  recalled,  the  raising  of  the  pylons  was  also  "Very 
impressive.. ..They  had  all  these  very  strong  Puerto  Ricans  pulling  at  cables.  It  was  like 
some  1930s  Mexican  mural  painting.  Labor  at  its  best.  All  coordinated  pulling  at  these 
cables,  and  pouring  cement  at  the  same  time,  and  getting  the  right  tension  on  every- 
thing."10 


8.  Gold    14  December    1993;   Nichols,   telephone   conversation,    14  December    1993;   "Center  for 
Radiophysics;"  Annual  Summary  Report,  Center  for  Radiophysics  and  Space  Research,  July  1,  1965— June  30,  1966, 

30  June  1966,  p.  10;  Arecibo  Observatory  Program  Plan,  October  1,  1 970— September  30,  1971,  May  1971,  pp.  62-63, 
AOL. 

9.  CRSR,  Scientific  Experiments  for  the  Arecibo  Radio  Observatory,  Research  Report  RS  5  (Ithaca:  CRSR, 

31  March  1960),  pp.  vii  and  31-33;  AIO,  Research  in  Ionospheric  Physics,  Research  Report  RS  41  (Ithaca:  CRSR,  30 
June  1962),  p.  7. 

10.  Price  27  September  1993;  CRSR,  Construction  of  the  Department  of  Defense  Ionospheric  Research  Facility, 
Research  Report  RS  22  (Ithaca:  CRSR,  30  June  1961),  pp.  1-2;  ibid.,  Research  Report  RS  34  (Ithaca:  CRSR, 
31  December  1961);  ibid.,  Research  Report  RS  40  (Ithaca:  CRSR,  30  June  1962),  pp.  12-15;  ibid.,  Research 
Report  RS  45  (Ithaca:  CRSR,  31  December  1962),  pp.  1  and  11-12;  various  items  in  publicity  binder,  Office  of 
the  Administrative  Director,  NAIC;  Thomas  C.  Kavanagh  and  David  H.  H.  Tung,  "Arecibo  Radar-Radio  Telescope 
Design  and  Construction,  "Journal  of  the  Construction  Division,  Proceedings  of  the  American  Satiety  of  Civil  EngineersQl 
(May  1965):  69-98. 


LITTLE  SCIENCE/BIG  SCIENCE 


91 


Figure  13 

Aerial  view  of  the  Arecibo  Observatory  showing  its  location  in  a  natural  sinkhole  in  the  hills  of  north  central  Puerto  Rico.  The 
antenna  is  so  large  that  its  can  only  be  seen  in  its  entirety  from  above.  (Courtesy  of  National  Astronomy  and  Ionosphere  Center, 
which  is  operated  by  Cornell  University  under  contract  with  the  National  Science  Foundation.) 

After  its  inauguration  on  1  November  1963,  the  Arecibo  Ionospheric  Observatory 
(AIO)  was  not  just  a  Cornell-ARPA  facility;  it  also  became  part  of  an  international  agree- 
ment for  the  exchange  of  faculty  and  graduate  students  between  Cornell  and  the 
University  of  Sydney,  signed  in  September  1964.  The  University  of  Sydney  was  a  major, 
worldwide  center  for  radio  astronomy.  The  agreement  gave  Americans  access  to  some  of 
the  most  advanced  radio  astronomy  instruments  in  the  world,  as  well  as  some  of  the  most 
renowned  researchers.11 

Bill  Gordon  directed  the  observatory  at  Arecibo.  After  meeting  Gordon  Pettengill  at 
Millstone,  Thomas  Gold  "twisted  his  arm"  to  get  Pettengill  to  take  the  position  of  associ- 
ate director.  At  Lincoln  Laboratory,  Pettengill  had  carried  out  radar  astronomy  experi- 
ments, but  more  as  a  hobby.  When  he  arrived  at  Arecibo  in  July  1963,  "A  totally  new  world 
opened  up  down  there.  This  was  a  university-operated  facility.... And  there  was  no  direct 
military  work!"  Pettengill  devoted  his  entire  time  to  planetary  radar  and  achieved  recog- 
nition in  the  field.12 

What  made  the  Arecibo  world  so  different,  apart  from  the  lack  of  "military  work" 
that  was  the  bread  and  butter  of  Lincoln  Laboratory,  was  the  fact  that  planetary  radar 
astronomy  was  an  integral  part  of  the  scientific  agenda.  Arecibo's  university  connection 
would  supply  graduate  student  researchers.  Moreover,  as  associate  director,  Pettengill 
could  hire  people  to  do  planetary  radar.  Thus,  the  earliest  Arecibo  planetary  radar 


11.  CRSR  Summary  Report,  July  I,  1964— -June  30,  1965,  1  July  1965,  CRSR,  p.  5;  Cornell-Sydney  University 
Astronomy  Center,  1965,  p.  4,  AOL;  Gold  and  Harry  Messcl,  "A  New  Joint  American-Australian  Astronomy  Center," 
Nature  204  (1964):  18-20. 

12.  Pettengill  28  September  1993;  Gold  14  December  1993. 


92  TO  SEE  THE  UNSEEN 


astronomer  was  not  trained  in  the  traditional  way,  as  a  graduate  student  in  an  academic 
setting,  but  was  hired  to  do  planetary  radar.  The  first  such  hire  was  Rolf  B.  Dyce. 

Pettengill  first  met  Dyce  years  earlier,  when  Dyce  was  with  the  Rome  Air 
Development  Center,  Griffiss  Air  Force  Base,  in  Rome,  New  York.  Dyce  had  a  B.A.  in 
Physics  and  a  Ph.D.  from  Cornell,  where  he  did  radar  studies  of  auroras.  Dyce  eventually 
landed  a  job  with  the  Stanford  Research  Institute  (SRI)  at  Menlo  Park,  California,  where 
he  worked  on  classified  ionospheric  and  radar  research,  including  auroral,  meteor,  and 
lunar  studies.  Dyce  and  Pettengill  also  toured  Europe  together  and  visited  key  radar 
research  centers,  including  Jodrell  Bank,  the  Dutch  facility  at  Dwingeloo,  the  Chalmers 
Institute  in  Gothenburg,  Sweden,  and  the  Norwegian  Defense  Research  Establishment. 
Pettengill  hired  Dyce  in  January  1964,  just  weeks  after  the  Arecibo  dedication  in 
November  1963.13 

Arecibo  was  different  from  Lincoln  Laboratory  and  Haystack  in  many  other  ways, 
too,  because  of  the  relationships  between  Arecibo  and  Cornell  and  between  Arecibo  and 
Lincoln  Laboratory.  While  MIT  did  not  train  radar  astronomers  to  work  at  Lincoln 
Laboratory,  Cornell  sent  graduate  students  to  Arecibo  to  work  on  doctoral  dissertations 
in  radar  astronomy.  MIT  students  also  carried  out  radar  astronomy  dissertation  research 
at  Arecibo.  As  a  result,  Arecibo  became  a  training  ground  for  future  radar  astronomers. 

Some  of  the  earliest  graduate  student  radar  research  was  done  on  the  Sun  and 
Moon,  not  the  planets.  Vahi  Petrosian,  a  Cornell  graduate  student  working  on  a  masters 
thesis,  attempted  some  solar  radar  work  in  July  and  August  1964.  After  later  attempts  by 
two  other  graduate  students,  solar  echo  experiments  were  abandoned;  the  results  were 
neither  as  good  nor  as  productive  as  those  achieved  by  the  El  Campo  solar  radar.14 

On  the  other  hand,  starting  in  1965,  Arecibo  undertook  a  far  more  vigorous  and  pro- 
ductive program  of  lunar  radar  research  with  supplementary  funding  from  NASA,  which 
hoped  to  use  the  results  to  help  select  Apollo  landing  sites.15  Carrying  out  the  lunar  work 
in  collaboration  with  Dyce  and,  occasionally,  Pettengill  was  Cornell  graduate  student 
Thomas  W.  Thompson.  The  research  formed  the  basis  of  his  1966  doctoral  dissertation. 
Thompson  worked  briefly  at  Haystack,  then  again  at  Arecibo,  before  he  found  a  position 
at  JPL.  He  returned  to  Arecibo  occasionally  to  make  lunar  radar  observations.16 


13.  Dyce  22  November  1994;  Pettengill  28  September  1993. 

14.  AIO,  Research  in  Ionospheric  Physics,  Research  Report  RS  61  (Ithaca:  CRSR,  31  December  1964), 
pp.  46-48;  ibid.,  Research  Report  RS  72  (Ithaca:  CRSR,  31  January  1968),  p.  127;  Vahi  Petrosian,  Two  Possible 
Methods  of  Detecting  UHF  Echoes  from  the  Sun,  Research  Report  RS  54  (Ithaca:  CRSR,  30  September  1963),  which 
was  his  masters  thesis.  His  doctoral  thesis,  completed  in  June  1967,  however,  was  on  "Photoneutrino  and  Other 
Neutrino  Processes  in  Astrophysics."  Petrosian  later  went  to  Stanford.  CRSR,  "Proposal  to  National  Science 
Foundation  for  Research  Ionospheric  Physics,  Radar-Radio  Astronomy,  October  1,  1969  through  September  30, 
1971,"  April  1969,  pp.  138-140,  Office  of  the  Administrative  Director,  NAIC. 

Donald  B.  Campbell  obtained  solar  continuous-wave  echoes  at  40  MHz  (7.5  meters)  during  the  summer 
of  1966.  AIO,  Research  in  Ionospheric  Physics,  Research  Report  RS  70  (Ithaca:  CRSR,  31  January  1967),  p.  75.  Alan 
D.  Parrish,  a  NASA  Trainee,  and  Campbell  made  more  solar  observations  in  1967.  ibid.,  Research  Report  RS  71 
(Ithaca:  CRSR,  31  July  1967),  pp.  78-79;  Campbell  8  December  1993. 

15.  Thompson  and  Dyce,  "Mapping  of  Lunar  Radar  Reflectivity  at  70  Cm,"  Journal  of  Geophysical  Research 
71  (1966):  4843-4853;  Thompson,  "Radar  Studies  of  the  Lunar  Surface  Emphasizing  Factors  Related  to  Selection 
of  Landing  Sites,"  Research  Report  RS  73  (Ithaca:  CRSR,  April  1968);  Gold,  CRSR  Summary  Report,  July  1,  1964— 
June  30,  1965,  1  July  1965,  CRSR,  p.  4;  Annual  Summary  Report,  Center  for  Radiophysics  and  Space  Research,  July  1, 

1966— June  30,  1967,  30  June  1967,  p.  10;  Annual  Summary  Report,  Center  for  Radiophysics  and  Space  Research,  July  1, 
1968— June  30,  1969,  30  June  1969,  p.  4;  AIO,  Research  in  Ionospheric  Physics,  Research  Report  RS  61  (Ithaca: 
CRSR,  31  December  1964),  pp.  39-41. 

16.  Thompson  29  November  1994;  NAIC  QR  Q2/1970,  n.p.;  Thompson,  "The  Study  of  Radar- 
Scattering  Behavior  of  Lunar  Craters  at  70  Cm,"  Ph.D.  diss.,  Cornell,  February  1966;  Thompson,  "Radar  Studies 
of  the  Lunar  Surface  Emphasizing  Factors  Related  to  Selection  of  Landing  Sites,"  Research  Report  RS  73 
(Ithaca:  CRSR,  April  1968).  The  lunar  radar  measurements  were  made  at  40  MHz  (7.5  meters)  and  430  MHz  (70 
cm)  at  the  AIO. 


LITTLE  SCIENCE/BIG  SCIENCE  93 


The  next  graduate  student  was  Raymond  F.  Jurgens,  whose  1969  dissertation  used 
Arecibo  radar  data  to  form  some  of  the  first  range-Doppler  images  of  Venus.  Then  came 
Donald  B.  Campbell,  originally  from  Australia.  Using  the  radar  interferometric  method 
developed  at  Haystack,  and  working  under  both  Dyce  and  Arecibo  director  Frank  Drake, 
Campbell  began  a  lifelong  career  devoted  to  the  radar  imaging  of  Venus.17  Both  he  and 
Jurgens  later  were  key  figures  in  planetary  radar  astronomy. 

While  its  relationship  with  Cornell  turned  Arecibo  into  a  breeding  ground  of  radar 
astronomers,  its  relationship  with  Lincoln  Laboratory  and  Haystack,  forged  through  the 
presence  at  Arecibo  of  Gordon  Pettengill,  provided  entree  to  the  software,  techniques, 
and  ephemerides  developed  by  Lincoln  Laboratory.  Pettengill  was  a  vital  factor  not  only 
as  associate  director  from  1963  to  1965,  but  also  as  Arecibo  director  from  1968  to  1970. 

At  the  heart  of  that  relationship  was  the  business  of  creating  radar  ephemerides.  The 
standard  planetary  ephemerides  issued  by  the  U.S.  Naval  Observatory  were  simply  not 
accurate  enough  for  radar  work,  so  special  ephemerides  computer  programs  had  to  be 
developed.  In  order  for  them  to  be  as  accurate  as  possible,  these  radar  ephemerides  had 
to  draw  on  a  data  base  of  radar  observations.  At  Lincoln  Laboratory,  Irwin  Shapiro  start- 
ed such  a  radar  ephemerides  computer  program.  Haystack  provided  a  large  amount  of 
the  ephemerides  data,  and  so  did  Arecibo  at  the  instigation  of  Gordon  Pettengill,  with  a 
modest  grant  from  NASA.  Pettengill  recalled  the  speed  with  which  radar  observational 
data  arrived  at  Lincoln  Laboratory:  "I  remember  we  used  to  send  it  back  by  special  deliv- 
ery mail.  We  would  mail  it  by  six  in  the  evening  at  Arecibo,  and  it  would  be  delivered  in 
Lexington,  Massachusetts,  at  nine  the  next  morning.  Very  efficient.  Then  it  would  be  put 
into  the  Lincoln  Laboratory  ephemeris  program."18  In  addition  to  the  ephemerides, 
Lincoln  Laboratory  supplied  Arecibo  with  software  and  techniques.  As  mentioned  earlier, 
Don  Campbell  adopted  the  Haystack  radar  interferometry  technique  at  Arecibo,  and  the 
special  fast  Fourier  transform  software  created  for  the  Haystack  interferometer  also 
migrated  to  Arecibo.19 

When  Pettengill  left  Arecibo  in  1970,  he  returned  not  to  Lincoln  Laboratory,  but  to 
MIT,  where  he  became  professor  of  planetary  physics  in  the  Department  of  Earth  and 
Planetary  Sciences.  The  change  from  Lincoln  Laboratory  to  MIT  was  as  stimulating  to 
Pettengill  as  the  original  move  to  Arecibo.  He  continued  planetary  radar  research,  using 
both  Haystack  and  Arecibo.  He  was  not  alone;  both  Tommy  Thompson  and  Don 
Campbell  used  both  telescopes.20  Moreover,  Pettengill,  who  already  had  guided  the  radar 
astronomy  dissertations  researched  at  Arecibo,  began  offering  a  course  in  radar  astron- 
omy at  MIT  and  sending  MIT  graduate  students  to  Arecibo  to  do  their  doctoral  research. 

The  fruit  of  this  cross-fertilization  between  Arecibo  and  MIT  and  Lincoln  Laboratory 
was  that  Arecibo  evolved  into  a  common  research  facility  for  both  Cornell  and  MIT,  so 
that  by  the  time  planetary  radar  astronomy  research  ended  at  Haystack,  Arecibo  already 
was  in  position  to  continue  the  research  programs  underway  at  Haystack.  That  did  not 
mean,  though,  that  the  Arecibo  telescope  provided  the  same  amount  of  observing  time  as 
Haystack. 

At  Haystack,  planetary  radar  astronomy  accounted  for  a  greater  percentage  of 
observing  time  than  at  Arecibo.  Although  planetary,  lunar,  and  solar  radar  experiments 
occupied  roughly  9  percent  of  Arecibo  antenna  time  for  the  period  December  1965 
through  September  1969,  only  2.4  percent  of  total  observing  time  was  given  over  to  radar 


17.  CRSR,  "Proposal  to  National  Science  Foundation  for  Research  Ionospheric  Physics,  Radar-Radio 
Astronomy,  October  1,  1969  through  September  30,  1971,"  April  1969,  Office  of  the  Administrative  Director, 
NAIC,  pp.  138-140;  Jurgens,  "A  Study  of  the  Average  and  Anomalous  Radar  Scattering  from  the  Surface  of  Venus 
at  70  Cm  Wavelength,"  Ph.D.  diss.,  Cornell,  June  1968. 

18.  Pettengill  28  September  1993. 

19.  Rogers  5  May  1994;  Hine  12  March  1993.  For  a  discussion  of  radar  interferometry  at  Haystack  and 
Arecibo,  see  Chapter  Five. 

20.  Pettengill  28  September  1993. 


94  TO  SEE  THE  UNSEEN 


astronomy  in  1970,  while  radar  accounted  for  about  a  third  of  Haystack  antenna  time  in 
the  same  year.21  Moreover,  as  radar  astronomy  use  of  Haystack  declined  from  17  percent 
in  1971  to  12  percent  in  1973,  radar  use  of  the  Arecibo  telescope  increased,  but  not  pro- 
portionally, and  peaked  in  1972  at  9.5  percent,  somewhat  lower  than  the  lowest  use  at 
Haystack.  The  combined  absolute  number  of  total  observing  hours  on  the  two  telescopes 
suggests  that  planetary  radar  astronomy  activity  in  the  early  1970s  was  not  increasing  or 
even  remaining  stable,  but  was  declining.  It  was  Little  Science  becoming  smaller. 

From  ARPA  to  the  NSF 

In  November  1974,  eleven  years  after  the  dedication  of  the  Arecibo  Ionospheric 
Observatory  (AIO) ,  a  second  dedication  ceremony  took  place  to  denote  the  instrument's 
upgrading  to  S-band.  The  upgrade  was  not  achieved  by  simply  adding  higher-frequency 
equipment.  The  reflector  surface  had  to  be  refinished,  the  suspended  platform  accom- 
modated to  the  new  equipment,  a  new  power  supply  provided,  and  the  S-band  transmit- 
ter and  maser  receiver  designed,  built,  and  installed.  Each  component  of  the  instrument 
had  to  be  adapted  in  order  that  the  whole  might  function  in  the  higher  frequency  range. 
For  planetary  radar  astronomy,  the  upgrade  essentially  created  a  new  instrument  with 
entirely  different  and  expanded  capabilities.  Nonetheless,  however  critical  the  upgrade 
was  for  radar  astronomy,  both  radio  astronomy  and  ionospheric  research  benefited  sig- 
nificantly from  the  resurfacing  and  equipment  improvements,  too. 

The  conversion  of  the  AIO  into  an  S-band  radar  telescope  was  a  long,  indirect,  and 
difficult  process,  even  if  considered  only  as  a  technological  feat.  The  conversion  paralleled 
and  was  inextricably  enmeshed  in  the  transformation  of  the  AIO  into  a  National  Science 
Foundation  National  Research  Center.  That  transformation  was  set  in  motion  by  cutbacks 
in  the  ARPA  budget,  not  the  Mansfield  Amendment. 

The  realization  that  the  S-band  upgrade  was  possible  is  said  to  have  been  born  in 
August  1966,  during  Hurricane  Inez.  The  100-kilometer-per-hour  (62-mile-per-hour) 
winds  moved  the  telescope  less  than  a  half  inch  (1.27  cm),  instead  of  the  foot  (30  cm)  it 
was  feared.  A  subsequent  study  of  the  telescope  structure  showed  that  it  was  sufficiently 
stable  to  operate  at  wavelengths  of  the  order  of  10  cm  (3,000  MHz).  Optimistically,  Frank 
Drake,  successor  to  Bill  Gordon  as  observatory  director,  thought  that  the  dish  could  be 
resurfaced  in  less  than  two  years  for  under  $3  million.22 

But  funds  were  not  readily  available.  Moreover,  the  annual  budget  allotted  by  ARPA 
started  to  shrink,  from  over  $2  million  initially  to  $1.8  million  in  the  period  1965  through 
1969.  Although  ARPA  was  cutting  back  all  research  in  order  to  support  the  Vietnam  War,23 


21.  Sebring  to  Hurlburt,  27  March  1970,  18/2/AC  135,  MITA;  AIO,  Research  in  Ionospheric  Physics, 
Research  Report  RS  69  (Ithaca:  CRSR,  30  June  1966),  p.  87;  ibid.,  Research  Report  RS  70  (Ithaca:  CRSR,  31 
January  1967),  pp.  124-125;  ibid.,  Research  Report  RS  71  (Ithaca:  CRSR,  31  July  1967),  pp.  113-124;  ibid., 
Research  Report  RS  72  (Ithaca:  CRSR,  31  January  1968),  pp.  125-134;  ibid.,  Research  Report  RS  74  (Ithaca: 
CRSR,  31  July  1968),  pp.  137-145;  ibid.,  Research  Report  RS  75  (Ithaca:  CRSR,  31  March  1969),  p.  51;  ibid., 
Research  Report  RS  76  (Ithaca:  CRSR,  30  September  1969),  p.  44;  NAIC  QR  Q1-Q4/1970,  passim.  The  Arecibo 
Observatory  quarterly  reports  for  the  years  1971  to  1975  indicate  the  fraction  of  radar  astronomy  use  of  the 
antenna:  2.9  percent  in  1971;  9.5  percent  in  1972;  6.9  percent  in  1973;  1.9  percent  in  1974;  and  7.2  percent  in 
1975.  At  Haystack,  in  March  1970,  for  example,  of  the  290  hours  scheduled,  90  (31  percent)  were  spent  on  radar 
observations.  See  Chapter  3  for  Haystack  radar  use. 

22.  Peter,  p.  12;  AIO,  Research  in  Ionospheric  Physics,  Research  Report  RS  70  (Ithaca:  CRSR,  31  January 
1967),  p.  1. 

23.  John  Lannan,  "An  Example  of  Scientific  Research  under  Scrutiny,"  The  Sunday  [Washington]  Star,  30 
March  1969,  p.  F-3.  For  the  AIO  budget,  see  CRSR  Summary  Report,  July  1,  1964— June  30,  1965,  1  July  1965,  CRSR, 
p.  1;  Annual  Summary  Refjart,  Center  for  Radiophysics  and  Space  Research,  July  1,  1965— -June  30,  1966,  30  June  1966, 
pp.  2  and  7;  ibid.,  July  1,  1966— June  30,  1967,  30  June  1967,  pp.  8,  10  and  12;  ibid.,  July  1,  1967— June  30,  1968, 
30  June  1968,  pp.  1,  11  and  13;  ibid.,  July  1,  1968— June  30,  1969,  30  June  1969,  pp.  1  and  15.  AFOSR  contract 
F44-620-67-C0066  allocated  $5,210,200  for  the  term  1  February  1967  through  30  September  1969. 


LITTLE  SCIENCE/BIG  SCIENCE 


95 


the  Arecibo  budget  suffered  because  ARPA  felt  that  the  telescope  performed  below  expec- 
tations. 

The  antenna  feed  operated  at  only  21  percent  efficiency;  the  dish  received  less  than 
half  the  power  it  should  have  received.  That  was  a  huge  dollar  loss,  too;  the  cost  of  build- 
ing a  dish  half  the  area  would  have  been  much  less.  Nonetheless,  it  was  still  an  extremely 
sensitive  telescope.  The  inefficiency  of  the  antenna  feed  became  a  source  of  friction 
between  Thomas  Gold  and  Bill  Gordon,  who  insisted  that  the  feed  could  be  improved, 
and  between  AIO  management  and  ARPA.24 


Figure  14 

Linear  antenna  feeds  attached  to  the.  suspended  platform  of  the  Arecibo  Observatory.  (Courtesy  of  National  Astronomy  and 
Ionosphere  Center,  which  is  of>erated  by  Cornell  University  under  contract  with  the  National  Science  Foundation.) 


24.  Gordon  28  November  1994;  Gold  14  December  1993;  Campbell  7  December  1993;  L.  Merle 
Lalonde  and  Daniel  E.  Harris,  "A  High-Performance  Line  Source  Feed  for  the  AIO  Spherical  Reflector,"  IEEE 
Transactions  on  Antennas  and  Propagation  AP-18  (January  1970):  41. 


96  TO  SEE  THE  UNSEEN 


The  line  feeds  were  an  ongoing  serious  problem.  After  a  three-day  visit  to  Arecibo  in 
October  1967,  BartJ.  Bok,  director  of  the  Steward  Observatory,  Tucson,  observed  that  the 
line  feed  problem  "seems  to  be  the  most  critical  one  facing  the  Arecibo-Cornell  group." 
A  number  of  Ithaca  researchers  attempted  to  improve  the  feeds.  One  Cornell  graduate 
student  considered  the  use  of  Gregorian  optics,  an  option  also  studied  by  the  AFCRL's 
Antenna  Laboratory.  However,  not  until  1988  was  the  first  Gregorian  feed  tested  and 
installed  at  Arecibo. 

Arecibo  had  three  feed  research  programs  going  on  at  the  same  time.  Only  one,  for 
a  high-powered,  430-MHz  radar  feed  operating  at  both  circular  polarizations,  was  vital  to 
its  radar  functions.  Of  two  competing  radar  feed  designs,  the  AIO  selected  that  of  Alan 
Love  of  the  Autonetics  Corporation,  a  subsidiary  of  North  American  Rockwell.  Love 
worked  with  Cornell's  L.  Merle  Lalonde  to  construct  an  appropriate  feed,  which  was 
installed  on  the  antenna  in  early  1972.  The  new  radar  feed  was  a  success.25 

ARPA's  funding  of  the  AIO  dropped  to  a  great  extent  because  of  the  inefficient  feed. 
Too,  radio  astronomy  at  the  AIO  was  expanding  rapidly  in  the  wake  of  the  discovery  of 
pulsars  (the  AIO  had  tremendous  advantages  for  investigating  them) ,  and  ARPA  felt  more 
and  more  that  it  should  support  just  the  facility's  ionospheric  work,  which  was  the  only 
research  relevant  to  Department  of  Defense  interests.  The  AIO,  though,  hoped  that  ARPA 
would  pay  for  the  resurfacing  and  a  new  radar  feed. 

Although  the  ARPA  contract  did  not  allow  the  AIO  to  seek  funding  from  other  agen- 
cies, ARPA  was  now  receptive  to  the  idea  of  sharing  the  AIO  budget  with  the  NSF.  So  with 
ARPA's  blessing,  Thomas  Gold  and  Frank  Drake  approached  the  National  Science 
Foundation  about  civilian  operational  money  for  the  AIO.  The  AIO  also  submitted  a 
proposal  to  the  NSF  in  early  1967  for  detailed  engineering  studies  and  a  cost  estimate  to 
resurface  the  reflector.26  The  search  for  both  resurfacing  and  operational  funds  thus 
proceeded  concurrently  and  was  boosted  by  the  report  of  the  Dicke  Panel. 

Thomas  Gold,  Frank  Drake,  and  Rolf  Dyce  pitched  the  Arecibo  resurfacing  project 
before  the  Dicke  Panel.  The  Panel  gave  the  project  highest  priority.  As  a  result,  Cornell 
obtained  an  NSF  grant  for  a  study  and  cost  estimate  of  the  reflector  resurfacing.  The  AIO 
selected  the  Rohr  Corporation,  which  also  built  JPL's  Mars  Station,  to  conduct  the  study. 
Rohr  planned  to  install  light  aluminum  panels  for  the  reflector  surface  at  a  total  cost  of 
$3.5  million.27 

The  NSF,  however,  did  not  ask  Congress  to  underwrite  the  resurfacing  of  the  Arecibo 
reflector.  The  feed  problem  stood  in  the  way.  At  its  meeting  of  16-17  October  1967,  the 
NSF  Astronomy  Advisory  Panel  resolved:28 

The  NSF  Advisory  Panel  urill  be  hesitant  to  favor  the  improvements  of  the  surface  of 
the  Arecibo  dish  or  the  undertaking  of  substantial  operating  expenses  for  Arecibo  until  a 
successful  radio  astronomy  feed  has  been  constructed  and  made  operational  at  frequencies 
low  enough  that  the  surface  is  not  critical. 


25.  Bok  to  George  B.  Field,  "Arecibo,"  NSFHF;  Kay,  A  Line  Source  Feed;].  Pierluissi,  A  Theoretical  Study  of 
Gregorian  Radio  Telescopes  with  Applications  to  the  Arecibo  Ionospheric  Observatory,  Research  Report  RS  57  (Ithaca: 
CRSR,  1  April  1964),  NAIC;  Peter,  p.  18;  Campbell  7  December  1993. 

26.  Diary  note,  Hurlburt,  15  December  1967,  and  Long  to  Haworth,  27  July  1967,  "Arecibo,"  NSFHF; 
Annual  Summary  Report,  Center  for  Radiophysics  and  Space  Research,  July  1,  1965— June  30,  1966,  30  June  1966, 
pp.  12  and  18;  ibid.,  July  1,  1966— June  30,  1967,  30  June  1967,  p.  8;  AIO,  Research  in  Ionospheric  Physics,  Research 
Report  RS  71  (Ithaca:  CRSR,  31  July  1967),  p.  1;  Gold  14  December  1993. 

27.  National  Science  Board,  Approved  Minutes  of  the  Open  Sessions,  pp.  113:14-113:15,  National 
Science  Board;  "Report  of  the  Ad  Hoc  Advisory  Panel  for  Large  Radio  Astronomy  Facilities,"  14  August  1967, 
typed  manuscript,  pp.  2-3,  NSFL;  Lalonde  and  Harris,  p.  42;  AIO,  Research  in  Ionospheric  Physics,  Research  Report 
RS  72  (Ithaca:  CRSR,  31  January  1968),  p.  4;  AIO,  Ibid.,  Research  Report  RS  74  (Ithaca:  CRSR,  31  July  1968), 
pp.  8-9. 

28.  Haworth  to  John  Foster,  9  November  1967;  Memorandum,  Gerard  Mulders  to  Haworth,  Randal  M. 
Robertson,  and  William  E.  Wright,  25  August  1967;  and  Memorandum,  Mulders  to  Robertson,  3  January  1968, 
"Arecibo,"  NSFHF. 


LITTLE  SCIENCE/BIG  SCIENCE  97 


In  short,  if  an  adequate  feed  design  were  not  feasible,  investing  in  an  expensive 
resurfacing  of  the  reflector  for  operation  at  higher  frequencies  made  no  sense.  The  feed 
problem  held  up  the  resurfacing  and  by  implication  the  entire  S-band  upgrade. 
Consequently,  Cornell  undertook  an  in-house  effort  to  design  a  327-MHz  feed  at  its  own 
expense. 

Although  the  reflector  resurfacing  project  came  to  a  temporary  halt,  the  drive  to 
secure  NSF  operational  support  succeeded  in  the  wake  of  the  Dicke  Panel  report.  In  July 

1967,  as  the  Dicke  Panel  was  meeting  in  Washington,  Cornell  Vice  President  for  Research 
and  Advanced  Studies  Franklin  A.  Long  asked  Leland  Haworth,  director  of  the  NSF,  for  a 
meeting  about  the  possibility  of  jointly  funding  the  operation  of  the  AIO  with  ARPA.  The 
NSF  and  ARPA  soon  entered  into  discussions  and,  by  late  August  1967,  the  NSF  was  agree- 
able to  replacing  the  AFOSR  as  the  government  agency  monitoring  the  Arecibo  con- 
tract.29 This  was  the  first  step  in  converting  the  AIO  into  a  civilian  observatory. 

ARPA  was  prepared  to  underwrite  the  full  AIO  budget  to  the  end  of  September  1968. 
Beginning  1  October  1968,  for  fiscal  years  1969  through  1972,  ARPA  would  pay  for  a  third 
of  the  AIO  budget,  representing  the  portion  of  telescope  time  spent  on  ionospheric  work. 
"It  is  very  much  hoped,"  the  ARPA  negotiator  expressed,  "that  the  entire  facility  will  be 
identified  as  a  National  Science  Foundation  Observatory  with  ARPA  as  one  of  several 
users."30 

In  December  1967,  well  before  passage  of  the  Mansfield  Amendment,  Cornell  and 
ARPA  came  to  an  agreement  on  the  AIO  contract.  Cornell,  NSF,  and  ARPA  would  nego- 
tiate a  one-year  contract  for  AIO  operation  from  1  October  1968  through  30  September 
1969.  The  ARPA-NSF  Memorandum  of  Understanding,  signed  in  late  April  1969,  left  the 
AIO  under  ARPA  and  the  AFOSR  until  1  October  1969,  when  the  NSF  took  over,  thereby 
anticipating  the  effect  of  the  Mansfield  Amendment.  For  the  fiscal  year  starting  1  October 

1968,  each  agency  agreed  to  pay  half  the  facility's  annual  budget.  For  the  two  years  begin- 
ning 1  October  1969,  ARPA  agreed  to  transfer  to  NSF  a  third  of  the  annual  budget  to  sup- 
port just  ionospheric  research.  ARPA  did  not  commit  any  funding  after  1  October  1971, 
but  left  the  door  open  to  the  possibility. 

The  Memorandum  of  Understanding  defined  ARPA's  step-by-step  divestment  of 
Arecibo.  Although  ARPA  initially  had  funded  Arecibo  for  Project  Defender,  the  telescope 
was  never  engaged  in  classified  military  research.  Moreover,  one  clause  in  the 
Memorandum  of  Understanding  specifically  forbade  the  participation  of  the  AIO  in 
secret  work:  'The  Observatory  shall  not  be  used  to  make  measurements  which  are  them- 
selves classified  nor  be  used  as  a  repository  for  classified  information."31  The  AIO  was  on 
the  rocky  road  to  civilian  supervision  and  funding. 

What's  In  a  Name? 

The  transformation  of  the  AIO  into  an  NSF  National  Research  Center  involved  two 
interconnected  issues,  the  observatory's  management  structure  and  the  status  of  ionos- 
pheric research,  both  of  which  were  complicated  by  personality  conflicts  and  turf  fights 
between  Big  Science  fields.  Implicit  in  being  a  National  Research  Center  was  free  access 
to  the  telescope  for  all  qualified  scientists.  The  AIO  always  maintained  that  it  operated  as 


29.  Hurlburt  diary  note;  Long  to  Peter  Franken,  23  August  1967,  and  Long  to  Leland  Haworth,  27  July 
1967,  "Arecibo,"  NSFHF. 

30.  Franken  to  William  Wright,  23  August  1967,  "Arecibo,"  NSFHF. 

31.  S.  J.  Lukasik  to  Long,  12  December  1967;  Memorandum  of  Understanding,  AIO,  attached  to  letter, 
Haworth  to  John  Foster,  30  April  1969;  and  Memorandum  of  Understanding,  AIO,  attached  to  letter,  S.  E. 
Clements  to  Haworth,  12  May  1969,  signed  by  Haworth  and  Foster,  "Arecibo",  NSFHF. 


98  TO  SEE  THE  UNSEEN 


a  national  center,  and  the  Cornell-Sydney  agreement  opened  the  observatory  to  foreign 
scientists.  The  real  problem  was  that  radio  astronomy  use  of  the  telescope  had  skyrocket- 
ed, especially  in  contrast  to  ionospheric  research.  From  December  1965  through 
September  1969,  for  example,  ionospheric  research  accounted  for  30  percent,  while  radio 
astronomy  took  up  50  percent  of  antenna  time.32 

Ionospheric  research  had  been  the  reason  for  creating  the  AIO  in  the  first  place,  and 
it  was  more  interesting  to  the  electrical  engineering  than  to  the  astronomy  department. 
The  name  of  the  facility  changed  to  the  Arecibo  Observatory,  discarding  the  "ionospher- 
ic" of  the  original  name.  To  some  individuals,  the  name  change  did  not  reflect  the  facili- 
ty's multiple  research  agenda,  which  was  the  intent  of  the  change,  but  instead  signified 
lack  of  interest  in  ionospheric  work.  As  Gordon  Pettengill  explained:  "We  settled  on  that 
name  early,  because  it  encompassed  the  radio  astronomy,  radar  astronomy,  and  ionos- 
pheric research.  There  was  quite  a  group  that  wanted  to  call  it  the  Arecibo  Ionospheric 
Observatory,  which  was  the  original  name  under  Bill  Gordon."33  Many  accused  Thomas 
Gold,  who  had  fostered  the  expansion  of  radio  astronomy,  of  thwarting  ionospheric  work, 
but  Gold  insisted  that  no  ionospheric  researchers  ever  were  turned  down. 

Perceptions  outside  Arecibo  and  Cornell  confused  the  presumed  reduction  of  ionos- 
pheric studies  with  the  rift  between  astronomy  and  electrical  engineering  within  the 
CRSR,  and  colored  everything  with  the  friction  between  Bill  Gordon  and  Thomas  Gold. 
Gold  found  Gordon  "a  little  difficult,  because  he  really  wanted  to  cut  himself  off  from 
Cornell,  from  everything  completely,  and  I  realized  that  if  he  did  so,  then  the  telescope 
would  never  be  used  for  radio  astronomy  and  radar,  and  it  would  become  merely  an  ionos- 
pheric instrument,  and  that  I  was  very  opposed  to,  being  nominally  in  charge  of  building 
such  a  huge  wonderful  instrument  and  then  finding  it's  not  used  for  what  it's  capable 
of  "34  Bin  Gordon,  for  his  part,  stated,  "If  you  ask  me,  I  was  mad  at  the  time,  and  whatev- 
er I  tell  you  has  some  personal  bias  built  in."  In  short,  he  explained,  "I  thought  I  was 
removed  from  a  job  that  I  deserved  to  have."35 

Frank  Drake,  radio  astronomer  and  one-time  Arecibo  director,  explained  the  con- 
flict rather  precisely.  "I  had  picked  up  enough  innuendo  in  Gold's  tone  and  Gordon's 
words  to  realize  that  the  two  of  them  were  engaged  in  a  bitter  battle  for  the  Arecibo  turf," 
he  wrote.  Gold  "wanted  the  Arecibo  telescope  freed  to  do  more  research  in  radio  astron- 
omy. He  was  lobbying  the  university  administration  to  put  it  under  his  jurisdiction." 
Gordon  "could  not  bear  to  relinquish  control  of  it."  He  left,  however,  after  Gold  pointed 
out  to  the  university  administration  that  Gordon  had  been  off-campus  far  longer  than  the 
university  bylaws  allowed.  "It  was  a  fact  people  might  have  been  willing  to  overlook,  but 
once  Gold  seized  on  it,  Gordon  was  forced  to  make  a  choice."36 

Feelings  about  the  friction  between  Gold  and  Gordon,  as  well  as  the  perceived 
neglect  of  ionospheric  work,  also  shaped  how  the  NSF  handled  the  AIO.  The  chief  per- 
sonality at  the  NSF  was  Tom  Jones,  director  of  the  Division  of  Environmental  Sciences.  He 
explained  the  situation  to  the  NSF  director  in  1968:37 


32.  Maintenance  and  equipment  improvements  were  1 1  percent  and  radar  astronomy  9  percent  of 
antenna  time.  AIO,  Research  in  Ionospheric  Physics,  Research  Report  RS  69  (Ithaca:  CRSR,  30  June  1966),  p.  87; 
Ibid.,  Research  Report  RS  70  (Ithaca:  CRSR,  31  January  1967),  pp.  124-125;  Ibid.,  Research  Report  RS  71  (Ithaca: 
CRSR,  31  July  1967),  pp.  113-124;  Ibid.,  Research  Report  RS  72  (Ithaca:  CRSR,  31  January  1968),  pp.  125-134; 
Ibid.,  Research  Report  RS  74  (Ithaca:  CRSR,  31  July  1968),  pp.  137-145;  Ibid.,  Research  Report  RS  75  (Ithaca: 
CRSR,  31  March  1969),  p.  51;  and  Ibid.,  Research  Report  RS  76  (Ithaca:  CRSR,  30  September  1969),  p.  44. 

33.  Pettengill  28  September  1993. 

34.  Gold  14  December  1993. 

35.  Gordon  28  November  1994. 

36.  Frank  Drake  and  Dava  Sobel,  Is  Anyone  Out  There?  (New  York:  Delacorte  Press,  1992) ,  pp.  77  and  79. 

37.  Jones  to  Haworth,  8  February  1968,  "Arecibo,"  NSFHF. 


LITTLE  SCIENCE/BIG  SCIENCE  99 


The  operation  ofAIO  has  been  tainted  by  a  great  deal  of  political  infighting  on  the 
Cornell  campus.  Results  of  these  confrontations  included  the  departure  from  Cornell  of 
Drs.  W.  Gordon  and  H.  Booker,  both  aeronomers,  who  were  the  originators  of  the  backscat- 
ter  concept  for  probing  the  ionosphere  and  who  saw  the  Arecibo  venture  through  from  the 
proposal  stage  right  on  up  to  its  final  construction  and  initial  operation.  There  are  indi- 
cations that,  aside  from  accepting  opportunities  for  professional  growth,  they  left  Cornell 
because  the  administrative  control  of  AIO  was  removed  from  the  director  of  the 
Observatory  and  placed  in  the  hands  of  another  individual  on  the  Cornell  campus.  We 
do  know,  from  conversations  with  aeronomers,  that  they  do  not  want  to  give  up  the  use  of 
the  Arecibo  instrument. 

Jones  maintained  a  vigil  on  the  AIO  case,  as  he  moved  from  the  Division  of 
Environmental  Sciences  to  the  Office  of  National  Centers,  which  directly  oversaw  the 
Arecibo  Observatory.  Thomas  Gold  found  that  Jones  "kept  expressing  a  sort  of  paranoia 
about  ionospheric  work,  but  constantly.  I  mean,  I  couldn't  talk  to  him  without  getting  a 
lecture  that  far  too  little  ionospheric  work  was  being  done,  and  he  couldn't  support  any 
funding  for  Arecibo  if  this  were  done,  even  though  at  the  time  it  was  doing  very  good  work 
in  radio  and  radar  astronomy,  but  not  enough  ionosphericists  wanted  to  go  there.  I  could- 
n't help  it!" 

According  to  Gold,  Jones  told  him  that  he  could  not  support  funding  for  Arecibo  if 
the  reduction  of  ionospheric  research  continued.  As  for  his  relations  with  Bill  Gordon, 
Thomas  Gold  insisted  that  it  had  nothing  to  do  with  ionospheric  research.  He  and 
Gordon  disagreed  over  the  management  of  the  observatory.  According  to  Gold,  Gordon 
wanted  to  operate  it  "in  a  way  independent  of  Cornell,"  and  he  did  not  want  to  return  to 
Cornell.  Bill  Gordon  "wanted  to  make  all  the  decisions  as  to  who  gets  what  time  and  all 
that,"  and  Gold  objected.38 

Control  of  the  observatory  was  the  key  issue  dividing  Gordon  and  Gold.  The  issue  of 
where  management  of  the  AIO  should  rest,  at  Arecibo  or  at  Ithaca,  was  precisely  the  con- 
cern of  the  NSF,  too.  The  issue  was  clouded  by  both  personality  conflicts  and  the  status  of 
ionospheric  research.  On  27-28  February  1968,  the  NSF  Advisory  Panel  for  Atmospheric 
Sciences,  which  included  Bill  Gordon,  issued  a  formal  statement  on  the  future  of  ionos- 
pheric research  at  the  AIO:  "As  the  NSF  assumes  increasing  operational  responsibility,  the 
Panel  strongly  recommends  that  any  management  changes  be  made  in  such  a  way  as  to 
insure  the  availability  of  the  AIO  for  experimental  research  in  aeronomy  and  solar-terres- 
trial physics."  Moreover,  'The  Panel  considers  it  important  to  establish  a  management 
structure  for  the  AIO  whereby  scientists  from  institutions  throughout  the  United  States 
may  use  the  Observatory.  To  accomplish  this,  it  is  suggested  that  the  scheduling  and  oper- 
ating policy  be  established  by  the  scientific  community  and  implemented  by  the  resident 
director.  An  appropriate  way  to  assure  representation  of  the  scientific  community  would 
be  to  place  the  management  of  the  AIO  in  the  hands  of  a  consortium  of  interested  uni- 
versities."39 

The  Advisory  Panel  was  not  alone  in  suggesting  management  by  a  university  consor- 
tium along  the  lines  of  NEROC  or  the  NRAO.40  However,  Cornell  and  Gold  wanted  to 
retain  control  of  the  Arecibo  Observatory  (AO).  Harry  Messel,  head  of  the  University  of 
Sydney  School  of  Physics  and  joint  director,  with  Gold,  of  the  Cornell-Sydney  University 


38.  Gold  14  December  1993.  Bill  Gordon  declined  comment  on  the  whole  affair.  Gordon  28  November 
1994. 

39.  Statement  of  the  National  Science  Foundation  Advisory  Panel  for  Atmospheric  Sciences  to  the 
Director  of  the  National  Science  Foundation,  21  March  1968,  "Arecibo,"  NSFHF. 

40.  See,  for  instance,  Haworth  to  Long,  23  January  1968,  "Arecibo,"  NSFHF. 


100  TO  SEE  THE  UNSEEN 


Astronomy  Center,  protested  to  Donald  F.  Hornig,  the  special  presidential  assistant  for  sci- 
ence and  technology,  that  any  change  in  the  AO  management  structure  would  affect  the 
Cornell-Sydney  arrangement,  too.  Despite  Hornig's  assurances  to  the  contrary,  the  evolv- 
ing AO  management  structure  led  to  the  termination  of  the  Cornell-Sydney  agreement.41 

However,  the  crux  of  the  management  structure  question — all  personality  and  turf 
conflicts  aside — was  separation  of  observatory  administration  from  all  academic  depart- 
ments, like  the  CRSR.  The  NSF  did  not  want  to  fund  National  Research  Centers  that  were 
prisoners  of  an  astronomy  department  or  of  any  other  academic  unit.  It  was  clear,  though, 
that  if  the  AO  were  to  become  a  National  Research  Center,  with  a  secured  budget  from 
the  NSF,  Cornell  would  have  to  draft  a  new  management  structure;  otherwise,  a  universi- 
ty consortium  might  take  over  Cornell's  managerial  role. 

In  March  1969,  as  the  NSF  looked  toward  assuming  full  responsibility  for  the  AO  on 
1  October  1969,  the  Foundation  asked  Cornell  to  prepare  a  proposal  for  the  operation  of 
the  AO  for  the  two-year  period  beginning  1  October  1969.  The  proposal  was  to  discuss  the 
AO  management  structure,  "bearing  in  mind  our  opinion  that  a  director  of  a  National 
Center  should  report  to  a  level  of  management  significantly  above  that  of  a  department 
or  similar  unit."42  The  April  1969  proposal  outlined  a  management  structure  drafted  the 
previous  summer.  The  director  of  the  AO  reported  to  a  policy  committee,  which  consis- 
ted of  only  the  university  provost,  the  director  of  the  CRSR  (Gold),  and  the  vice  president 
for  research  and  advanced  studies.43 

A  special  National  Science  Foundation  AIO  Group  reviewed  the  proposal.  Their 
major  objection  was  the  management  plan:  "It  does  not  show  much  change  from  the  exist- 
ing management  structure  at  Cornell  and  does  not  appear  to  be  suitable  for  a  National 
Center.  No  member  of  the  AIO  group  finds  it  acceptable."  Specifically,  the  problem  was 
the  three-man  policy  committee.  'This  Committee  seems  clearly  intended  by  Cornell  to 
be  the  group  which  runs  the  show.  It  is  proposed  that  it  be  made  up  exclusively  of  Cornell 
employees  resident  in  Ithaca.  The  suggestion  that  such  a  group  should  be  considered 
'national  management'  has  reduced  the  undersigned  [Fregeau]  to  a  conviction  that  his 
education  in  the  art  of  strong  language  is  grossly  inadequate." 

The  AIO  Group  felt  that  a  more  appropriate  structure  would  have  the  observatory 
director  report  directly  to  the  vice  president  of  research,  a  single  individual,  and  not  a 
committee;  otherwise,  "the  implication  [is]  that  the  committee  is  the  AIO  director's  boss." 
In  the  judgement  of  the  AIO  Group,  'The  Cornell  proposal  is  not,  in  its  present  form, 
suitable  for  review  by  the  scientific  community.  If  it  were  to  be  sent  out  in  this  form,  the 
community  reaction  would  probably  poison  the  beginnings  of  what  we  expect  to  be  a  fruit- 
ful venture  for  NSF."44 

On  1  October  1969,  when  monitorship  of  the  Arecibo  contract  passed  to  the  NSF, 
Cornell  reorganized  the  AO's  management  structure  to  conform  more  closely  to  the 
Foundation's  guidance.  The  observatory  was  removed  from  CRSR  supervision  and  placed 
under  an  Arecibo  Project  Office  headed  by  Assistant  Vice  President  for  Research  (Arecibo 
Affairs)  Thomas  Gold.45 


41.  Messel  to  Donald  Hornig,  12June  1968,  and  Hornig  to  Messel,  9July  1968,  "Arecibo, "  NSFHF;  Gold 
14  December  1993. 

42.  Randal  N.  Robertson  to  Long,  17  March  1969,  "Arecibo,"  NSFHF. 

43.  CRSR,  "Proposal  to  National  Science  Foundation  for  Research  Ionospheric  Physics,  Radar-Radio 
Astronomy,  October  1,  1969  through  September  30,  1971,"  April  1969,  Office  of  the  Administrative  Director, 
NAIC;  advanced  draft,  The  Management  of  the  AIO  as  a  National  center,"  July,  1968,  "Arecibo,"  NSFHF. 

44.  Memorandum,  J.  H.  Fregeau  to  Associate  Director  (Research),  NSF,  28  April  1969,  "Arecibo," 
NSFHF. 

45 .  A  nnual  Summary  Report,  Center  for  Radiophysics  and  Space  Research,  July  1,  1 969— June  30,  1 970,  30  June 
1970,  p.  9. 


LITTLE  SCIENCE/BIG  SCIENCE  101 


In  the  following  months,  Cornell  and  the  NSF  continued  to  consider  the  observa- 
tory's management  structure.  The  result  was  a  new  organizational  structure  effective 
1  July  1971  that  brought  it  more  in  line  with  other  National  Research  Centers,  and  a  new 
name,  the  "National  Astronomy  and  Ionospheric  Center"  (NAIC).  The  name  and 
acronym  were  intended  to  emulate  the  NRAO  as  a  model  and  gave  assurances  of  the 
importance  of  ionospheric  research. 

In  the  new  management  structure,  the  title  of  Assistant  Vice  President  of  Research 
(Arecibo  Affairs)  was  discontinued.  Gold  had  quit.  Those  duties  were  given  to  the  obser- 
vatory director,  who  was  responsible  to  Cornell,  through  the  vice  president  for  research, 
for  the  overall  management  and  operation  of  Arecibo.  He  prepared  the  annual  budget, 
annual  program  plan,  and  long-range  plans  for  the  AO.  The  observatory  director  was  to 
be  located  primarily  in  Ithaca  and  was  also  the  director  of  the  NAIC.  The  director  of 
observatory  operations,  who  answered  to  the  director,  had  responsibility  for  the  opera- 
don,  maintenance,  administration,  and  improvement  of  the  facility,  oversaw  personnel 
and  time  allocations,  and  helped  prepare  the  budget.  He  was  required  to  be  located  in 
Arecibo.46 

For  the  new  director  of  observatory  operations,  the  NAIC  hired  Tor  Hagfors  in  1971. 
His  selection  reassured  those  who  worried  about  the  status  of  ionospheric  research. 
Hagfors  had  an  impressive  background  in  ionospheric  (and  radar)  research  and  admin- 
istration at  the  Norwegian  Defense  Research  Establishment,  Stanford  University,  the 
Jicamarca  Radio  Observatory  (where  he  was  director,  1967-1969),  and  Lincoln 
Laboratory's  Millstone  Hill  radar.47 

The  NSF  and  NASA  Agreement 

As  the  new  management  structure  emerged,  and  as  the  National  Science  Foundation 
took  over  the  Arecibo  contract,  the  search  to  fund  the  S-band  upgrade  continued.  In  May 
1969,  the  Subcommittee  on  Science,  Research,  and  Development  of  the  Committee  on 
Science  and  Astronautics,  headed  by  Emilio  Q.  Daddario  (D-Conn.),  recommended 
deferring  the  NSF  request  for  resurfacing  money.  Gordon  Pettengill,  speaking  as  Arecibo 
director,  pointed  out  that  "many  throughout  the  radio  astronomy  community  were  seri- 
ously disappointed  at  the  failure  of  the  Congress  to  authorize  funds  for  the  resurfacing  of 
the  AO  reflector."  When  the  Dicke  Panel  reconvened  in  June  1969  and  reaffirmed  the 
need  for  the  resurfacing,  they  too  expressed  disappointment  that  the  new  reflector  sur- 
face had  not  yet  been  started.48 

A  major  breakthrough  occurred  when  NASA  took  an  interest  in  the  project. 
Throughout  the  1960s,  NASA  had  funded  only  mission-oriented  radar  research,  but  not 
radar  telescope  construction.  In  January  1969,  Harry  H.  Hess,  chair  of  the  Space  Science 
Board,  wrote  to  John  Naugle,  associate  administrator  of  Space  Science  and  Applications 
at  NASA,  urging  NASA  to  fund  the  Arecibo  radar  upgrade.  The  cost,  estimated  to  be  $5 
million  for  the  resurfacing  plus  $2  or  $3  million  more  for  the  radar  equipment,  was  "small 
in  comparison  with  the  construction  of  a  new  radar  facility  but  would  make  it  possible  to 


46.  Campbell  9  December  1993;  Arecibo  Observatory  Program  Plan,  October  I,  1970—Sef>Umber  30,  1971, 
May  1971,  pp.  35-39,  Office  of  the  Administrative  Director,  NAIC. 

47.  Pettengill  28  September  1993;  Campbell  7  December  1993;  Arecibo  Observatory  Program  Plan, 
October  1,  1971— September  30,  1972,  January  1972,  NAIC,  pp.  25-31;  Arecibo  Observatory  Program  Plan,  October  1, 
1970— September  30,  1971,  May  1971,  p.  63,  AOL;  NAIC  QR  Q3/1971,  9. 

48.  AIO,  Research  in  Ionospheric  Physics,  Research  Report  RS  76  (Ithaca:  CRSR,  30  September  1969),  p.  1; 
"Report  of  the  Second  Meeting  of  the  Ad  Hoc  Advisory  Panel  for  Large  Radio  Astronomy  Facilities,"  15  August 
1969,  typed  manuscript,  p.  3,  NSFL. 


1 02  TO  SEE  THE  UNSEEN 


map  the  surface  of  Venus  with  a  resolution  of  a  few  kilometers.  Such  a  map  would 
obviously  be  a  tremendous  step  forward  in  our  knowledge  of  the  planet.  The  NASA  con- 
tribution to  the  total  cost  of  improving  the  Arecibo  facility  would  be  very  small  compared 
to  the  cost  of  obtaining  the  same  information  from  some  future  orbiter."49 

Hess's  argument  closely  resembled  that  of  Werner  von  Braun  in  an  anecdote  related 
by  Don  Campbell:  "I  don't  know  if  it's  apocryphal  or  not,  but  there  is  the  story  that 
Werner  von  Braun  said,  if  you  can  get  a  two-kilometer  resolution  on  Venus  for  $3  million, 
which  is  roughly  what  we  were  talking  about,  that  it  was  an  immense  bargain,  and  that 
NASA  should  take  it  straight  away."50 

Indeed,  NASA  became  interested  in  funding  the  upgrade  for  one  major  reason.  The 
S-band  equipment  could  make  radar  maps  of  the  Venusian  surface  with  a  resolution  of  two 
to  five  kilometers.  The  space  agency  was  interested  in  a  one-megawatt  radar  operating  at 
10  cm  (3,000  MHz).  And  as  NASA  chief  of  planetary  astronomy  William  Brunk  came  to 
realize,  the  total  cost  of  the  upgrade  was  a  fraction  of  the  initial  cost  of  the  facility.51 

The  country  was  discovering  that  it  could  not  afford  both  guns  and  butter,  the 
Vietnam  War  and  the  Great  Society.  NASA  and  NSF  were  under  serious  pressure  to  cut 
their  budgets,  and  in  December  1969,  the  new  Republican  President  shut  down  the  NASA 
Electronics  Research  Center  in  Cambridge.  Budgetary  austerity  perhaps  led  NASA  to  sup 
port  the  Arecibo  S-band  upgrade,  at  a  cost  of  a  few  million  dollars,  over  the  NEROC  tele- 
scope, with  an  estimated  price  tag  of  $30  million  dollars.  Furthermore,  given  the  superi- 
or transmitter  power  and  receiver  sensitivity  of  the  upgraded  Arecibo  S-band  radar  over 
the  proposed  NEROC  radar,  NASA  would  be  getting  a  better  investment  for  its  dollars. 

Budgetary  belt  tightening  also  induced  NASA  to  realize  that  every  planetary  mission 
had  to  do  something  that  could  not  be  done  from  the  ground,  and  missions  would  have 
to  rely  on  ground-based  results  more  than  ever.  The  radar  images  obtainable  from  the 
upgraded  radar  would  be  invaluable  to  the  exploration  of  the  planets.  Thus,  the  mission- 
oriented  logic  of  NASA,  combined  with  budgetary  restraint,  led  to  its  adopting  the 
Arecibo  upgrade  project.52  NASA  now  approached  the  NSF. 

When  NASA  and  NSF  representatives  met  on  2  December  1969,  the  NASA  budget 
for  fiscal  1971  was  among  the  topics  of  discussion.  The  space  agency  was  going  to  ask  for 
an  extra  $1  million  to  build  a  major  planetary  research  facility  as  part  of  its  Planetary 
Astronomy  Program.  Three  candidate  projects  were  under  consideration:  a  60-inch  (1.5- 
meter)  planetary  telescope  at  Cerro  Tololo,  Chile;  a  large-aperture  infrared  telescope; 
and  the  Arecibo  upgrade.  The  final  choice  pivoted  on  the  NSF  budget  submission  to  the 
Bureau  of  the  Budget  and  Congress. 

The  NASA  strategy  was  to  pay  for  the  resurfacing,  if  the  NSF  failed  to  win  funds  from 
Congress,  and  to  worry  about  the  rest  of  the  S-band  upgrade  later.  Brunk  knew  that  NASA 
had  to  be  prepared  to  pay  for  the  radar  equipment.  Because  radar  equipment  was  "not  a 
high  priority  item  for  general  radio  astronomy,"  he  reasoned,  "the  development  of  a  high 
power  radar  transmitter  at  a  wavelength  of  10  centimeters  will  be  a  low  priority  for  NSF 
funding  and  must  therefore  be  included  in  the  NASA  Planetary  Astronomy  budget."53 

Soon  after  the  NASA-NSF  meeting,  in  February  1970,  Cornell  submitted  a  funding 
proposal  for  the  S-band  upgrade  to  both  NASA  and  the  NSF.  The  proposal  asked  for  $3 
million  over  three  years,  with  work  to  begin  February  1971.  Both  the  NSF  and  NASA  fis- 
cal 1971  budget  requests  contained  money  for  Arecibo.  The  NSF  proposed  to  underwrite 


49.  Hess  to  Naugle,  27  January  1969,  NHOB. 

50.  Campbell  7  December  1993. 

51.  Brunk,  Planetary  Astronomy  New  Starts,  FY 1971,  n.d.,  NHOB. 

52.  Tatarewicz,  p.  98.  For  the  creation  and  demise  of  the  NASA  Electronics  Research  Center,  see  Ken 
Hechler,  Toward  the  Endless  Frontier:  History  of  the  Committee  on  Science  and  Technology,  1959-1979  (Washington: 
USGO,  1980),  pp.  219-231. 

53.  Henry J.  Smith,  Memo  to  the  files,  11  December  1969,  NHOB. 


LITTLE  SCIENCE/BIG  SCIENCE  103 


the  reflector  resurfacing,  while  NASA  budgeted  for  the  radar  equipment  and  its  installa- 
tion. Congress  approved  both  the  NASA  and  NSF  Arecibo  S-band  expenditures.  The  NSF 
funds  were  frozen,  however,  until  a  new  cost  estimate  became  available.  The  estimate, 
completed  in  November  1970,  was  $5.6  million.54 

The  upgrade  brought  together  the  NSF  and  NASA  into  a  special  relationship  that 
started  with  joint  discussions  in  December  1970  between  William  Brunk,  chief  of  the 
NASA  Planetary  Astronomy  Program,  and  Daniel  Hunt,  head  of  the  NSF  Office  of 
National  Centers  and  Facilities  Operations.  As  discussions  progressed,  on  6  March  1971, 
NASA  formally  expressed  its  intent  to  enter  into  an  agreement  with  the  NSF  for  the  addi- 
tion of  the  S-band  equipment.  The  two  agencies  entered  into  negotiations  and,  on  24  June 
1971,  signed  a  Memorandum  of  Agreement,  which  went  into  effect  1  July  1971.55 

Under  the  agreement,  the  NSF  funded  the  resurfacing  and  NASA  the  addition  of  a 
one  megawatt  S-band  radar  transmitter,  receivers,  and  associated  changes  to  the  antenna 
to  provide  radar  capability  at  a  wavelength  of  ten  centimeters  (3,000  MHz).  The  project 
was  to  be  managed  under  the  existing  NSF-Cornell  contract.  The  NSF  would  serve  as  the 
monitoring  agency,  and  NASA  would  transfer  its  portion  of  the  funds  to  the  NSF.  The 
agreement  deferred  the  issue  of  S-band  operational  costs  until  later,  although  the  two 
agencies  intended  to  share  those  costs  proportionally.56 

In  this  way,  NASA  came  to  fund  radar  instrument  construction  and  committed  itself 
to  supporting  the  research  performed  with  the  instrument.  This  deviation  from  earlier 
policy  was  motivated  by  an  interest  in  mission-oriented  research,  namely,  to  obtain  radar 
images  in  support  of  space  missions  to  the  planets,  particularly  to  Venus.  The  conse- 
quence was  a  permanent  institutional  and  funding  arrangement  for  planetary  radar 
astronomy  at  Arecibo,  as  well  as  a  unique  instrument. 


Arecibo  Joins  the  S-Band 


The  NASA-NSF  agreement,  backed  by  Congressionally-approved  funds,  provided  the 
legal,  financial,  and  managerial  framework  for  the  actual  upgrade  work  to  take  place.  The 
upgrade  began  with  a  search  for  a  contractor  to  undertake  the  reflector  resurfacing.  Two 
firms  bid,  the  Rohr  Corporation  and  LTV  Electrosystems  of  Dallas,  and  in  November  1971 
Cornell  awarded  the  contract  to  LTV  Electrosystems,  which  shortly  afterward  changed  its 
name  to  E-Systems.  The  original  spherical  reflector  consisted  of  1/2-inch  (1.3  cm)  steel 
wire  mesh  (chicken  wire)  supported  by  heavy  steel  cables.  Over  38,000  thin  aluminum 
panels,  fabricated  on-site  by  E-Systems,  replaced  the  chicken  wire.  From  the  beginning, 
inefficiencies  and  equipment  failure  plagued  panel  installation,  but  they  were  overcome, 
and  the  last  panel  was  installed  in  November  1973.57 


54.  AIO,  Proposal  to  NSF  and  NASA  for  Major  Additions  and  Modifications  to  the  Suspended  Antenna  Structure 
and  Equipment  of  the  Arecibo  Observatory,  February  1971  through  February  1973,  February  1970,  and  Daniel  Hunt  to 
Brunk,  11  December  1970,  NHOB;  National  Science  Board,  Minutes  of  the  Open  Meetings,  132:6  and  133:7-8, 
National  Science  Board;  NAIC  QR  Q3/1971,  p.  13. 

55.  Hunt  to  Brunk,  11  December  1970;  NASA  Deputy  Associate  Administrator  for  Space  Science  and 
Applications  to  Assistant  Administrator,  Office  of  DoD  and  Interagency  Affairs,  6  March  1971;  Memorandum, 
Director  of  Planetary  Programs,  Office  of  Space  Science  and  Applications,  NASA,  to  Associate  Administrator  for 
Office  of  Tracking  and  Data  Acquisition,  20  May  1971;  and  Memorandum  of  Agreement  between  NASA  and  the 
NSF  for  the  Addition  of  a  High-Power  S-Band  Radar  Capability  and  Associated  Additions  and  Modifications  to 
the  Suspended  Antenna  Structure  of  the  NAIC  at  Arecibo,  24  June  1971,  NHOB. 

56.  Memorandum  of  Agreement  between  NASA  and  the  NSF  for  the  Addition  of  a  High-Power  S-Band 
Radar  Capability  and  Associated  Additions  and  Modifications  to  the  Suspended  Antenna  Structure  of  the  NAIC 
at  Arecibo,  24  June  1971,  NHOB;  "High  Power  Transmitter  to  Boost  Arecibo  Radar  Capability,"  NSF  press 
release,  17  August  1971,  "Radar  Astronomy,"  NHO. 

57.  NAIC  QR  Ql/1971,  p.  5;  Q2/1971,  p.  6;  Q3/1971,  p.  6;  Q4/1971,  p.  7;  Ql/1972,  p.  10;  Q2/1972, 
p.  13;  Q3/1972,  p.  11;  and  Ql/1973,  p.  13;  National  Science  Board,  Minutes  of  the  Open  Meetings,  144:4-5, 
National  Science  Board. 


1 04  TO  SEE  THE  UNSEEN 


Concurrently,  the  NAIC  oversaw  the  design  and  construction  of  the  S-band  radar 
transmitter,  receivers,  and  associated  equipment;  the  necessary  modifications  to  the  sus- 
pended feed  platform;  and  construction  of  a  new  carriage  house  to  hold  the  S-band 
equipment.  Ammann  &  Whitney,  a  well-known  structural  engineering  consulting  firm, 
reported  on  the  suspended  structure  and  reflector  cable  anchorages  as  well  as  on  the  fea- 
sibility of  upgrading  the  suspended  structure.  They  found  no  basic  deficiencies  in  the 
structure  that  would  make  upgrading  impractical  or  inadvisable.58 

In  order  to  develop  specific  transmitter  characteristics  that  met  scientific  goals,  yet 
represented  realistic  state-of-the-art  feasibility,  NAIC  staff  discussed  its  design  with  experi- 
enced radar  astronomers  and  with  experts  from  Varian  Associates,  Raytheon,  and 
Continental  Electronics.  The  operating  frequency,  2380  MHz  (12.6  cm),  appeared  to  be 
the  optimum  choice  for  both  radar  and  radio  astronomy  and  was  close  to  the  JPL  plane- 
tary radar  frequency  (2388  MHz;  12.6  cm).59 

Originally,  the  transmitter  was  to  produce  800  kilowatts  using  two  klystrons.  The 
NAIC  based  the  decision  on  the  experience  of  JPL  Goldstone,  where  a  single  klystron  pro- 
duced 400  kilowatts  of  average  continuous-wave  power  at  2388  MHz.  Although  Varian  was 
developing  a  one  megawatt  continuous-wave  klystron,  the  advantages  of  proven  reliability 
and  ready  availability  of  spares  militated  against  using  a  single,  experimental  one- 
megawatt  klystron.  Finally,  after  extensive  discussion  with  representatives  of  NASA  and  the 
NSF,  the  NAIC  reduced  the  transmitter  power  requirement  to  450  kilowatts,  thereby  low- 
ering costs  "without  impacting  upon  scientific  goals  of  the  program."  In  contrast,  the  orig- 
inal UHF  radar  transmitter  produced  only  150  kilowatts  of  average  power.60 

The  experience  of  JPL  in  operating  at  S-band  proved  invaluable  to  the  Arecibo  radar 
upgrade.  In  addition  to  providing  expert  advice  to  the  NAIC  staff,  a  former  JPL  employ- 
ee reviewed  technical  matters  for  the  NASA  technical  monitor.  The  maser  receivers,  more- 
over, were  excess  Deep  Space  Network  equipment.  The  agreement  between  the  NAIC  and 
JPL  for  the  transfer  of  the  masers  noted  that  JPL  was  "a  pioneer  in  the  development  of 
maser  systems,"  and  that  "no  commercial  firms  have  the  required  capability,  experience 
and  expertise  to  produce  an  S-band  maser  system  that  would  be  operational  at  2.38 
GHz."" 

The  renovated  reflector  was  dedicated  on  15-16  November  1974.  After  delivery  of 
the  keynote  speech,  Rep.  John  W.  Davis  (D-Ga.)  gave  the  signal  for  the  transmission  of 
The  Arecibo  Message,  1974,  an  attempt  to  communicate  with  extraterrestrial  civilizations. 
The  radar  upgrade,  however,  was  not  yet  completed  and  would  not  be  entirely  ready  until 
the  following  year.62 

Yet,  shortly  after  the  resurfacing  dedication,  Gordon  Pettengill  (Arecibo)  and 
Richard  Goldstein  (JPL)  used  the  S-band  transmitter  to  bounce  signals  off  the  rings  of 
Saturn.  Because  the  Arecibo  maser  receiver  was  not  yet  installed,  Arecibo  sent  and  JPL's 
Mars  Station  received.  The  bistatic  experiment  worked,  despite  line  feed  and  turbine  gen- 
erator problems  at  Arecibo. 


58.  AIO,  Proposal  to  NSF  and  NASA  for  Major  Additions  and  Modifications  to  the  Suspended  Antenna  Structure 
and  Equipment  of  the  Arecibo  Observatory,  February  1971  through  February  1973,  February  1970,  pp.  7-8,  11-15, 
NHOB;  NAIC  QR  Q3/1972,  pp.  11-12. 

59.  NAIC  QR  Q4/1971,  p.  8;  and  Q2/1972,  p.  13. 

60.  Campbell  8  December  1993;  NAIC  QR  Q2/1970,  p.  4,  Q4/1970,  p.  9,  Ql/1972,  p.  12,  Q3/1972,  p. 
12,  and  Ql/1973,  p.  14;  AIO,  Proposal  to  NSF  and  NASA  for  Major  Additions  and  Modifications  to  the  Suspended 
Antenna  Structure  and  Equipment  of  the  Arecibo  Observatory,  February  1971  through  February  1973,  February  1970,  pp. 
14-15,  NHOB;  AIO  dedication  brochure,  no  page  numbers,  Cornell,  1974,  NHOB. 

61.  Brunk  to  Claude  Kellett,  18  April  1973,  NHOB;  Jack  W.  Lowe  to  W.  E.  Porter,  29  March  1977,  Office 
of  the  Administrative  Director,  NAIC;  NAIC  QR  Ql/1972,  p.  1 1;  Peter,  p.  13.  Documents  relating  to  the  transfer 
can  be  found  in  the  Office  of  the  Administrative  Director,  NAIC. 

62.  Drake  and  Sobel,  pp.   180-185;  Campbell  8  December  1993;  Dedication  publication,  Cornell 
University,  1974,  NHOB;  National  Science  Board,  Minutes  of  the  Open  Meetings,  168:2,  National  Science  Board; 
NAIC  QR  Q3/1974,  p.  10,  Q2/1975,  p.  4,  and  Q3/1975,  p.  4. 


LITTLE  SCIENCE/BIG  SCIENCE  105 


As  Don  Campbell  recalled:  'The  initial  feeds  that  we  used  with  the  transmitter  need- 
ed cooling;  we  were  having  trouble  attaching  the  cooling  lines.  People  would  line  up  late 
at  night  in  front  of  the  control  room  during  this  experiment.  We  would  turn  on  the  trans- 
mitter, and  there  would  be  this  sort  of  flash  of  light,  as  things  burned  up  up  there  and 
everybody  went  'Ah!'  It  was  a  bit  like  fireworks.  When  the  problem  finally  got  solved,  I 
think  everyone  was  rather  disappointed  that  there  wasn't  any  flash  of  light  up  there!"63 

The  Arecibo  S-band  upgrade  literally  created  a  new  instrument  with  which  to  do 
planetary  radar  astronomy,  a  field  whose  outer  limits  of  capability  still  leaned  strongly  on 
the  availability  of  new  hardware.  Although  the  Arecibo  telescope  made  S-band  radar 
observations  of  Mars  beginning  August  1975  for  NASA's  Viking  mission,  the  arrangement 
with  NASA  freed  Arecibo  also  to  do  radar  research  that  was  not  mission  related.  So,  late 
the  following  month,  on  28  September  1975,  the  radar  detected  Callisto,  followed  two 
nights  later  by  Ganymede,  the  first  detections  of  Jupiter's  Galilean  moons.64 

The  NASA  agreement  guaranteed  planetary  radar  astronomy  an  instrument  and  a 
research  budget.  Nowhere  else  did  planetary  radar  astronomy  operate  with  such  extensive 
institutional  and  financial  support.  These  unique  advantages,  combined  with  its  relations 
with  Cornell  and  MIT,  have  sustained  Arecibo  as  the  focal  center  of  planetary  radar 
astronomy  to  the  present  day. 


The  JPL  Mars  Station 


In  sharp  contrast  to  Arecibo,  JPL  did  not  formally  recognize  planetary  radar  astron- 
omy as  a  scientific  activity.  Planetary  radar  had  neither  a  budget  line  nor  a  program  at  JPL; 
it  was  invisible.  Its  role  was  to  test  the  performance  of  the  Deep  Space  Network  (DSN) .  Eb 
Rechtin,  the  architect  of  the  DSN,  deliberately  avoided  creating  a  radar  astronomy  pro- 
gram. He  saw  no  reason,  other  than  for  science,  why  NASA  ought  to  fund  it.  Instead,  plan- 
etary radar  became,  in  the  words  of  JPL  radar  astronomer  Richard  Goldstein,  the  "cow- 
catcher on  the  DSN  locomotive,"  financed  at  the  "budgetary  margin"  of  the  DSN.  In 
Goldstein's  own  words,  "I  was  the  cow-catcher  and  still  am."65 

Radio  astronomy,  on  the  other  hand,  held  a  more  privileged  position.  Nick  Renzetti, 
the  DSN  manager  responsible  for  links  between  the  Network  and  its  users  (NASA  space 
missions),  forged  an  agreement  with  NASA  Headquarters  that  permitted  qualified  radio 
astronomers  to  perform  experiments  on  Goldstone  antennas  at  no  cost,  provided  the 
experiments  did  not  conflict  with  the  antennas'  prime  mission,  spacecraft  communica- 
tions and  data  acquisition.66 

Not  only  was  JPL  planetary  radar  astronomy  invisible,  but  relations  between  JPL  and 
its  oversight  institution,  the  California  Institute  of  Technology,  were  about  as  distant  as 
those  between  Lincoln  Laboratory  and  MIT.  JPL  employees,  like  their  peers  at  Lincoln 
Laboratory,  could  not  have  graduate  students,  unless  they  held  a  joint  appointment  at 
Caltech.  Although  Dick  Goldstein  taught  a  radar  astronomy  course  at  Caltech  during  the 
1960s,  his  students  did  not  become  radar  astronomers,  but  went  into  other  fields.  An 
unusual  case  was  Lawrence  A.  Soderblom,  who  took  Goldstein's  course  in  the  fall  of  1967. 
Soderblom  later  joined  the  U.S.  Geological  Survey,  where  he  interpreted  planetary  radar 
data.67 


63.  Campbell  8  December  1993;  Campbell  7  December  1993;  NAIC  QR  Ql/1975,  p.  4. 

64.  NAIC  QR  Q3/ 1976,  pp.  4-5. 

65.  Goldstein    14  September    1993;   Goldstein   7  April    1993;   Rechtin,   telephone   conversation, 
13  September  1993. 

66.  Renzetti  16  April  1992;  Renzetti  17  April  1992. 

67.  Soderblom  27  June  1994. 


1 06  TO  SEE  THE  UNSEEN 


Unlike  Lincoln  Laboratory  or  Arecibo,  JPL  did  not  hire  people  to  do  radar  astron- 
omy, because  JPL  officially  did  not  have  a  radar  astronomy  program.  Goldstein  and  Dewey 
Muhleman  had  participated  in  the  1961  Venus  radar  experiment,  not  because  they  were 
Caltech  graduate  students,  but  because  they  were  JPL  employees  in  Walt  Victor's  group. 
Roland  Carpenter,  another  JPL  planetary  radar  astronomer  of  the  1960s,  also  worked 
under  Walt  Victor.68  Once  Roland  Carpenter  and  Dewey  Muhlemen  left  JPL,  Dick 
Goldstein  remained  the  sole  JPL  radar  astronomer  for  several  years. 

Planetary  radar  astronomy  subsisted  at  JPL  during  the  1960s  on  money  earmarked 
for  various  space  missions  and  on  the  budget  of  the  DSN.  The  NASA  budget  then  was 
more  generous.  NASA  paid  the  cost  of  operating  and  maintaining  the  Goldstone  radar  as 
part  of  the  DSN,  so  that  the  costs  of  the  radar  instrument  were  paid.  When  Goldstein 
needed  a  piece  of  hardware  designed  and  built,  he  assigned  the  job  to  one  of  the  employ- 
ees he  supervised  as  manager  of  Section  331.  The  Advanced  Systems  Development  bud- 
get of  the  DSN  paid  for  hardware  design  and  construction.69 

In  order  to  obtain  time  on  the  Goldstone  radar,  Goldstein  went  from  mission  to 
mission  and  explained  why  the  mission  ought  to  support  his  radar  experiments.  With 
approval  from  a  mission,  Goldstein  could  then  request  antenna  time  from  the  committee 
in  charge  of  allocating  antenna  use.  Mariner  missions  supported  many  of  the  radar  obser- 
vations, while  Viking  and  Voyager  supported  experiments  on  Mars,  Saturn's  rings,  and  the 
Galilean  satellites  of  Jupiter.  Officially,  the  experiments  were  done  for  neither  radar 
improvement  nor  the  science,  but  for  "better  communications"  with  spacecraft.70 

If  the  NASA  Headquarters  Planetary  Science  Program,  then  headed  by  William 
Brunk,  approved  of  a  particular  set  of  radar  experiments,  getting  antenna  time  was  much 
easier.  As  Goldstein  explained,  Brunk  "would  support  me  a  little  and  I  took  that  as  a  pos- 
itive thing,  and  I  guess  later  on  he  turned  that  off,  but  it  wasn't  very  big  in  the  first 
place. ...It  was  a  kind  of  a  way  to  get  legitimacy.  If  he  funds  you  a  little,  that  means  it's 
important.  If  he  doesn't  fund  you  at  all,  that  means  it's  not  important....!  would  go  to  great 
lengths  to  get  antenna  time  and  a  little  funding  from  Brunk  was  helpful."71 

Planetary  radar  astronomy  at  JPL  thus  came  into  existence  and  continued  to  func- 
tion because  of  the  Laboratory's  Big  Science  space  missions  and  Deep  Space  Network 
activities.  In  particular,  it  was  the  idea,  put  forth  by  the  DSN's  chief  architect  Eb  Rechtin, 
that  radar  astronomy  would  have  the  dual  function  of  testing  the  DSN's  ability  to  support 
interplanetary  missions  and  developing  new  hardware  for  the  DSN  (that  is,  the  justifica- 
tion for  having  Advanced  Systems  Development  underwrite  radar  astronomy  hardware). 
It  was  specifically  for  developing  and  testing  new  DSN  hardware  that,  shortly  after  the 
1961  Venus  radar  experiment,  Rechtin  arranged  with  NASA  to  set  aside  a  Goldstone  radar 
for  that  purpose.  On  that  instrument,  Goldstein  and  Carpenter  made  Venus  radar  obser- 
vations during  the  1962  and  1964  conjunctions.  Planetary  radar  research  benefitted  from 
the  developmental  work,  which  increased  the  continuous-wave  radar's  average  power  out- 
put from  10  to  13  kilowatts  in  1962  and  then  to  100  kilowatts  for  the  1964  Venus  experi- 
ment.72 

When  Goldstein  made  observations  during  the  1967  Venus  conjunction,  however,  he 
used  a  new,  more  powerful  64-meter-diameter  (210-ft-diameter)  S-band  antenna,  the  Mars 
Station.  The  need  to  handle  missions  at  ever  increasing  distances  from  Earth  furnished 


68.  Carpenter,  telephone  conversation,  14  September  1993. 

69.  Jurgens  23  May  1994;  Goldstein  14  September  1993;  Downs  4  October  1994. 

70.  Memorandum,  Carl  W.  Johnson   to  Murray,  31   October   1977,  62/3/89-13,  JPLA;  Goldstein 
14  September  1993. 

71.  Goldstein  14  September  1993. 

72.  Victor,   "General  System  Description,"  p.  3  in  Goldstein,  Stevens,  and  Victor,  eds.,  Goldstone 
Observatory  Report  for  October-December  1962,  Technical  Report  32-396  (Pasadena:  JPL,  1  March  1965);  Waff, 
ch.  6,  pp.  17  &  19;  Goldstein  and  Carpenter,  "Rotation  of  Venus,"  pp.  910-911;  Carpenter,  "Study  of  Venus  by  CW 
Radar,"  p.  142. 


LITTLE  SCIENCE/BIG  SCIENCE  107 


the  raison  d'etre  for  JPL's  entry  into  the  Big  Dish  arena,  and  incidentally  supplied  its 
future  radar  astronomers  with  an  ideal  instrument  for  imaging  and  other  planetary  radar 
work.  With  the  Mars  Station,  Goldstein  and  his  colleagues  discovered  three  rugged  sec- 
tions of  Venus;  the  largest  received  the  name  Beta.  The  needs  of  NASA  space  missions,  not 
radar  astronomy,  dictated  the  design  of  the  Mars  Station. 

The  Mars  Station  represented  the  DSN's  commitment  to  the  S-band  and  its  need  for 
large  antennas  capable  of  communicating  with  probes  at  great  distances  from  Earth. 
Starting  in  1964,  all  new  space  missions  were  to  use  the  higher  S-band.  Despite  the  com- 
mitment to  S-band,  NASA  still  had  active  missions  operating  at  lower  frequencies.  The 
switch  to  S-band  throughout  the  Deep  Space  Network  therefore  required  a  hybrid  tech- 
nology capable  of  handling  missions  operating  at  either  the  higher  or  lower  frequency 
bands.  A  JPL  design  team  devised  the  equipment,  which  was  installed  throughout  the 
DSN. 

The  hybrid  equipment,  however,  was  only  a  transitional  phase  before  the  construc- 
tion of  more  powerful  and  more  sensitive  antennas  specifically  intended  to  handle 
unmanned  missions  to  the  planets.  In  order  to  determine  the  essential  characteristics  and 
optimal  size  for  those  antennas,  JPL  initiated  a  series  of  studies  in  1959  that  culminated 
in  the  Advanced  Antenna  System.  NASA's  Office  of  Tracking  and  Data  Acquisition,  which 
oversaw  the  DSN,  sponsored  a  pioneering  conference  on  large  antennas  on  6  November 
1959.  Speakers  reported  on  three  kinds  of  antennas:  steerable  parabolic  dishes,  fixed 
antennas  with  movable  feeds  (e.g.,  Arecibo),  and  arrays,  the  same  antenna  types  consid- 
ered later  by  NSF  panels. 

NASA  and  JPL  decided  to  stay  with  the  proven  design  of  steerable  dishes.  The  next 
decision  was  antenna  size.  JPL  engineering  studies  showed  that  antenna  diameters 
between  55  and  75  meters  (165  and  225  ft)  were  near  optimal  and  the  most  cost-effective. 
The  final  choice,  64  meters  (210  ft),  was  the  same  size  as  the  recently-completed 
Australian  radio  telescope  at  Parkes.  This  was  no  coincidence.  JPL  engineers  had  received 
a  lot  of  help  from  the  Australian  designers.  Their  studies  of  the  Parkes  telescope  provid- 
ed JPL  engineers  with  a  wealth  of  data  and  ideas  to  use  in  the  design  of  their  64-meter 
(210-ft)  dish. 

JPL  also  commissioned  private  firms  to  carry  out  feasibility  and  preliminary  design 
studies  for  the  Advanced  Antenna  System  beginning  in  September  1960,  before  awarding 
a  construction  contract  to  the  Rohr  Corporation  in  June  1963.  Construction  proceeded 
after  JPL  analyzed  and  approved  the  Rohr  design  in  January  1964.  Rohr  completed  the 
antenna  in  May  1966,  following  the  formal  dedication  on  29  April  1966. 


108 


TO  SEE  THE  UNSEEN 


Figure  15 

JPL  Goldstone  Mars  Station  (DSS-14)  upon  completion  in  1966.   (Courtesy  of  Jet  Propulsion  Laboratory,  photo  no. 
333-5967BC.) 

The  dish  was  dubbed  the  Mars  Station,  because  its  mission  was  to  support  Mariner 
on  its  journey  to  Mars  in  1964,  long  before  the  antenna  was  operational.  Nonetheless,  on 
16  March  1966,  the  big  dish  received  its  first  signals  from  Mariner  4  and  provided  opera- 
tional support  for  Pioneer  7,  launched  in  August  1966.  The  Mars  Station  subsequently 
supported  several  other  missions,  including  the  first  Surveyor  flights,  and  made  possible 
live  Apollo  television  pictures  from  the  Moon,  not  to  mention  planetary  radar  images  and 
topographical  maps.  In  order  to  systematize  its  growing  number  of  antennas  around  the 
world,  the  DSN  instituted  a  numbering  system,  so  that  each  Deep  Space  Station  (DSS) 
would  bear  a  unique  number.  The  original  Echo  antenna  became  DSS-12,  while  the  anten- 
na used  in  the  Venus  radar  experiments  became  DSS-13.  The  Mars  Station  was  DSS-14.73 

The  Mars  Station,  as  part  of  the  Deep  Space  Network,  underwent  a  major  upgrade 
in  the  1970s  in  order  to  accommodate  the  needs  of  the  Viking  and  Mariner  Jupiter-Saturn 
spacecraft  (later  known  as  Voyager) .  For  the  Viking  mission,  each  DSN  station  would  have 
to  handle  six  simultaneous  data  streams  from  the  two  Viking  Orbiters  and  the  one  Lander. 


73.  Corliss,  Deep  Space  Network,  pp.  37-38,  50,  60-61,  82,  84,  87,  129  and  131;  Renzetti,  A  History, 
pp.  25-26,  32,  52  and  54;  Robertson,  pp.  255-261;  The  NASA/JPL  64-Meter-Diameter  Antenna  at  Goldstone, 
California:  Project  Report,  Technical  Memorandum  33-671  (Pasadena: JPL,  15 July  1974),  pp.  7-17;  Rechtin,  Bruce 
Rule,  and  Stevens,  Large  Ground  Antennas,  Technical  Report  32-213  (Pasadena:  JPL,  20  March  1962),  pp.  7-10. 


LITTLE  SCIENCE/BIG  SCIENCE  109 


Viking,  in  fact,  was  a  dual-frequency  craft;  it  used  both  S-band  and  X-band  frequencies. 
For  the  Mariner  flight  to  Jupiter  and  Saturn,  the  telemetry  rates  were  the  same  as  those 
for  Mariner  10,  but  the  data  were  coded  and  transmitted  at  X-band  from  distances  up  to 
nine  astronomical  units.  Operating  in  the  higher  X-band  range  gave  the  increased  sensi- 
tivity needed  to  remain  in  contact  with  Mariner,  as  it  flew  by  Jupiter  and  Saturn. 
Construction  of  the  400-kilowatt,  X-band  (8495  MHz;  3.5  cm)  transmitter  for  the  Mars 
Station  was  completed  by  Advanced  Systems  Development,  and  the  DSS-14  began  opera- 
ting at  X-band  in  1975.74 

During  the  1970s,  the  population  of  JPL  planetary  radar  astronomers  grew.  Jurgens 
had  an  undergraduate  and  graduate  degree  in  electrical  engineering  from  Ohio 
University  and  had  taught  electrical  engineering  at  Clarkson  College  (Ohio) ,  before  pur- 
suing a  doctoral  degree  at  Cornell.  Sometime  after  he  finished  researching  his  disserta- 
tion, a  study  of  the  radar  scattering  properties  of  Venus,  at  Arecibo,  JPL  hired  Jurgens  in 
1972  to  serve  on  the  technical  staff  of  the  Telecommunications  Research  Section,  not  to 
do  planetary  radar  astronomy.75 

Also  working  in  Goldstein's  section  was  George  Downs,  who  had  studied  radio 
astronomy  at  Stanford  University  under  Ronald  Bracewell.  Goldstein  had  Downs  analyze 
Mars  radar  data  and  make  observations  at  Goldstone  to  assist  in  the  selection  of  the  Viking 
landing  site,  a  project  funded  by  the  Viking  Project  Office.  The  planetary  radar  work,  how- 
ever, was  in  addition  to  his  regular  JPL  duties,  which  involved  studying  newly  discovered 
radio  sources  as  potential  timing  sources  for  the  Deep  Space  Network.76 

During  the  heyday  of  the  Viking  Mars  radar  observations,  Goldstein  called  upon 
other  JPL  employees,  such  as  Howard  C.  Rumsey,  Jr.,  who  had  a  strong  background  in 
physics  and  mathematics,  and  the  hardware  experts  George  A.  Morris  and  Richard  R. 
Green.  Jurgens  described  the  atmosphere  at  JPL:  "We  all  knew  each  other's  talents.  It  was 
very  efficient.  Nobody  ever  felt  like  we  were  working  terribly  hard.  It  was  just  like  a  big 
playpen.  Everybody  came  here,  and  we  sort  of  did  our  thing  and  thought  about  what  we 
wanted  to  do.  We'd  talk  to  each  other,  and  we'd  go  out  to  lunch.  It  was  the  period  of  the 
long  lunches  sometimes.  We  had  the  Gourmet  Society.  The  Gourmet  Society  was  really 
headed  by  Howard  Rumsey,  who  really  liked  good  food.  He  would  read  the  Sunday 
gourmet  page  and  the  Thursday  gourmet  page  in  the  L.  A.  Times,  and  pick  out  interest- 
ing restaurants.  At  least  one  day  a  week,  we  went  trudging  off-lab  to  eat  decent  food  at 
some  interesting  place  that  Howard  had  selected.  These  things  often  involved  bicycle  trips 
as  far  as  Long  Beach."77 

Once  Viking  project  funding  ended  in  1976,  JPL  radar  astronomy  hit  hard  times. 
Getting  time  on  the  DSN  become  more  difficult.  It  was  easy  to  get  time  in  the  early  and 
middle  1960s,  when  the  DSN  was  tracking  few  spacecraft.  As  Dick  Goldstein  explained: 
"Back  in  the  sixties  I  thought  of  myself  as  director  of  the  Goldstone  Observatory.  I  got  to 
choose  what  we  could  do,  if  I  could  get  support  for  it."78  During  the  1960s,  the  JPL  radar 
experiments  conducted  on  Venus  involved  hundreds  of  hours  of  runs;  for  example,  the 
1961  Venus  experiment  involved  238  hours  of  data  collected  over  two  months.  But  by  the 
end  of  the  decade,  the  amount  of  time  available  had  declined.  The  JPL  1969  Venus  obser- 
vations were  not  made  daily  for  a  period  of  months  during  inferior  conjunctions,  but  only 
"on  17  days  spaced  from  11  March  to  16  May  1969."79 


74.  Rob  Hartop  and  Dan  A.  Bathker,  The  High-Power  X-Band  Planetary  Radar  at  Goldstone:  Design, 
Development,  and  Early  Results,"  IEEE  Transactions  on  Microwave  Theory  and  Techniques  MIT-24  (December  1976): 
958-963;  JPL  Annual  Report,  1974-1975,  p.  22.JPLA. 

75.  Jurgens  23  May  1994. 

76.  Downs  4  October  1994. 

77.  Jurgens  23  May  1994. 

78.  Goldstein  14  September  1993. 

79.  Golomb,  "Introduction,"  in  Victor,  Stevens,  and  Golomb,  p.  4;  Goldstein  and  Howard  C.  Rumsey,  Jr., 
"A  Radar  Snapshot  of  Venus,"  Science  169  (1969):  975. 


110  TO  SEE  THE  UNSEEN 


The  reduction  in  available  antenna  time  was  in  direct  proportion  to  the  increasing 
number  of  spacecraft  with  which  the  Deep  Space  Network  communicated.  By  1977,  the 
DSN  was  in  communication  with  a  record  14  spacecraft.  In  addition  to  the  three  Viking 
craft  (two  orbiters  and  one  lander),  the  DSN  communicated  with  Helios  1  and  2,  Pioneer 
11  (Saturn),  Pioneer  10  (which  was  leaving  the  solar  system),  Voyagers  1  and  2,  and 
Pioneers  6,  7,  8,  and  9.  That  number  grew  to  19,  a  new  record,  the  following  year,  when 
the  DSN  also  handled  communications  with  Pioneer  Venus,  which  was  an  orbiter  and  four 
probes.80 

Then  the  Deep  Space  Network  stopped  funding  radar  astronomy  hardware.  The  abil- 
ity to  carry  out  radar  astronomy  without  official  recognition  was  maintained  thanks  to  the 
presence  at  high  levels  of  JPL  management  of  Eb  Rechtin  and  Walt  Victor,  who  watched 
over  planetary  radar  activities.  But  Rechtin  left  JPL,  and  Victor  transferred  in  December 
1978  from  the  DSN  to  the  Office  of  Planning  and  Review.81  Without  their  guardianship, 
JPL  radar  astronomy  was  vulnerable. 

As  Goldstein  explained:  "From  a  chauvinistic  point  of  view,  it  was  a  disaster,  because 
the  rest  of  the  world  passed  us  by.. ..We  went  from  being  a  couple  years  ahead  to  being  a 
couple  years  behind."82  Without  funding  for  hardware,  the  radar  system  was  at  risk. 
Moreover,  the  Goldstone  Mars  Station  was  in  desperate  need  of  repairs,  and  the  equip- 
ment was  becoming  harder  and  harder  to  maintain.  In  1976,  the  antenna  already  was  ten 
years  old,  and  the  electronic  equipment  transferred  to  the  Mars  Station  from  the  Venus 
Station  (DSS-13)  was  even  older.83 

The  termination  of  Deep  Space  Network  funding  of  planetary  radar  astronomy  grew 
out  of  two  concerns,  one  within  JPL  and  the  other  within  the  Deep  Space  Network.  One 
of  Bruce  Murray's  chief  concerns  after  taking  over  as  laboratory  director  was  the  state  and 
status  of  science  and  scientists  at  JPL.  The  basic  criticism  was  that  JPL  lacked  a  commit- 
ment to  scientists.  But  the  problem  had  a  cultural  side;  technologically-centered  team- 
work dominated  laboratory  culture.  Also,  many  of  those  doing  science  were  like  Dick 
Goldstein  and  Ray  Jurgens;  trained  and  hired  as  electrical  engineers,  they  carried  out 
radar  astronomy  science  experiments.  Murray  made  the  problem  the  topic  of  mini- 
retreats,  meetings,  and  seminars  and,  as  a  first  step  in  elevating  the  status  of  science  at  JPL, 
appointed  in  October  1977  the  first  JPL  chief  scientist,  Caltech  physics  professor  Rochus 
E.  Vogt,  who  had  authored  a  report  on  relations  between  Caltech  and  JPL,  another  topic 
of  great  concern.84 

Despite,  or  rather  because  of,  Murray's  concerns  for  science  at  JPL,  planetary  radar 
astronomy  did  not  fair  well  under  his  reign  as  laboratory  director.  Goldstein  was  trans- 
ferred out  of  the  section  where  he  had  guided  and  supported  the  JPL  planetary  radar 
effort.  JPL  management  decided  that  it  was  not  proper  to  do  science  under  the  guise  of 
improving  the  DSN.  Radar  astronomy  should  compete  with  other  JPL  science  activities, 
and  the  Office  of  Space  Science  and  Applications  (OSSA;  now  the  OSSI,  Office  of  Space 
Science  and  Instruments)  at  NASA  Headquarters  should  fund  it,  they  ruled.85 

At  the  same  time,  the  DSN  budget  was  suffering  from  monetary  and  manpower  lim- 
itations.86 To  make  matters  worse,  a  routine  review  of  the  Deep  Space  Network,  chaired 


80.  JPL  Annual  Report,  1976-1977,  p.  22,  and  ibid.,  1978,  p.  20,  JPLA. 

81.  Murray  to  Allen  M.  Lovelace,  30  November  1978,  75/5/89-13,  JPLA. 

82.  Goldstein  14  September  1993. 

83.  Jurgens  23  May  1994. 

84.  Agenda,  Director's  Mini-Retreat,  "How  Does  Science  Fit  In  at  JPL?,"  22  March  1977,  55/3/89-13; 
Director's  Letter,  no.  22,  30  September  1977,  61/3/89-13;  Roger  Noll  to  Murray,  23  November  1977,  63/3/89- 
13;  and  typed  manuscript,  First  Annual  "State  of  the  Lab"  Talk  by  Murray  to  Management  Personnel,  1  April 
1977,  55/3/89-1 3,  JPLA. 

85.  Goldstein  14  September  1993. 

86.  Notes  from  a  discussion  of  TDA  problems  discussed  during  a  mini-retreat  held  8  November  1977, 
63/3/89-13,  JPLA;  Jurgens  23  May  1994;  and  Stevens  14  September  1993. 


LITTLE  SCIENCE/BIG  SCIENCE  1 1 1 


by  Eb  Rechtin,  declared  that  radar  astronomy  was  no  longer  the  "cow-catcher"  of  the  DSN, 
meaning  that  the  role  of  radar  astronomy  in  creating  new  hardware  to  help  drive  forward 
the  Deep  Space  Network  had  come  to  an  end.  It  was,  therefore,  time  to  pull  the  plug  on 
planetary  radar  astronomy,  after  previous  reviews  had  lauded  it. 

From  time  to  time,  acting  under  instruction  from  NASA  Headquarters,  the  Deep 
Space  Network  called  into  existence  the  TDA  (Tracking  and  Data  Acquisition)  Advisory 
Panel  to  review  DSN  long-term  plans.  Planetary  radar  was  held  high  as  an  integral  part  of 
DSN  development  activities  by  Ed  Posner,  a  DSN  manager.  Among  the  hardware  contri- 
butions of  radar  astronomy  he  listed  were  microwave  components,  signal  processing  tech- 
niques, and  station  control  concepts,  all  of  which  were  tested  in  a  "realistic  environment." 
Planetary  radar  fell  from  that  favorable  position  during  the  1978  review.  The  head  of  the 
review  panel,  now  called  the  DSN  Advisory  Group,  was  none  other  than  Eb  Rechtin,  the 
architect  of  the  Deep  Space  Network  and  the  one  responsible  for  making  planetary  radar 
a  testbed  of  DSN  technology.  DSN  management  asked  the  panel  to  consider,  among  many 
other  questions,  radar  astronomy.  In  the  opinion  of  the  Advisory  Group,  which  Eb 
Rechtin  wrote,  "Another  DSN  technology  which  may  have  had  its  day  as  a  foundation  for 
DSN  technology  is  DSN  radar  astronomy.  Radar  astronomy  served  the  DSN  very  well  for 
many  years.  The  Advisory  Group  wonders  what  the  next  area  might  be."87  Radar  astrono- 
my no  longer  produced  the  cutting  edge  hardware  that  justified  the  support  of  Advanced 
Systems  Development.  As  a  result,  planetary  radar  astronomy  at  Goldstone  went  begging 
for  money. 

A  good  part  of  the  problem  was  the  perception  of  planetary  radar  as  just  a  testbed 
for  DSN  technology.  The  value  of  the  science  was  simply  not  recognized  by  either  DSN 
management  or  NASA  Headquarters.  After  all,  in  accordance  with  Eb  Rechtin's  plan, 
planetary  radar  was  not  to  occupy  a  budget  line  nor  to  have  program  status;  it  was  simply 
a  DSN  activity  to  assist  in  the  development  and  testing  of  new  technology. 

The  lack  of  money  to  even  maintain  the  Goldstone  radar,  whose  age  and  one-of-a- 
kind  design  engineering  made  it  all  that  much  harder  to  maintain,  began  to  frustrate  the 
performance  of  experiments.  By  1980,  the  Goldstone  radar  was  in  such  bad  shape  that 
planetary  radar  astronomy  experiments  were  no  longer  carried  out  on  a  regular  basis.  The 
radar  was  resurrected  for  attempts  at  asteroid  4  Vesta  on  28  May  1982  and  comets  IRAS- 
Araki-Alcock  and  Sugano-Saigusa-Fujikawa  in  1983,  but  only  Comet  IRAS-Araki-Alcock  was 
detected  successfully.  As  Ray Jurgens  reflected  on  the  situation:  "Basically,  it  looked  like  it 
was  the  end  of  the  radar."88 

Goldstack 

In  discussing  radar  systems  available  for  planetary  research,  an  instrument  that  one 
must  not  overlook  is  the  bistatic  Goldstack  radar,  which  used  Haystack  as  the  transmitting 
antenna  and  the  JPL  Goldstone  DSS-14  radar  as  the  receiving  antenna.  In  the  past,  plan- 
etary radar  astronomers  seldom  used  bistatic  radars,  let  alone  radars  requiring  the 
coordination  of  two  unrelated  institutions.  Bistatic  radars  require  a  daunting  amount  of 
coordination  on  both  the  technical  and  institutional  level.  Nonetheless,  transmitting 
power  and  antenna  receiver  sensitivity  can  combine  to  create  a  radar  capable  of  doing 
more  than  either  facility  operating  monostatically.  In  theory,  Goldstack  could  outperform 
either  Haystack  or  DSS-14  separately  and  achieve  a  nearly  tenfold  increase  in  overall  radar 
performance. 


87.  TDA  Advisory  Panel,  1971-1972,"  and  TDA  Advisory  Council,  1978-1981,"  JPLPLC. 

88.  Jurgens  23  May  1994;  Jurgens,  "Comet  Iras,"  pp.  222  and  224. 


112  TO  SEE  THE  UNSEEN 


When  radar  astronomers  Irwin  Shapiro  and  Gordon  Pettengill  pitched  Goldstack  to 
NASA  in  1968,  they  outlined  an  ambitious  program  of  research:  1)  observations  of  the 
Galilean  satellites  Ganymede  and  Callisto;  2)  maps  of  the  surfaces  of  Mercury  and  Venus; 
3)  a  Moon-Earth-Moon  triple-bounce  experiment  to  study  the  Earth's  radar-reflecting 
properties;  4)  topographical  studies  of  Mars  at  a  resolution  of  150  meters;  and  5)  a  radar 
test  of  General  Relativity.89  Haystack  and  JPL  engineers  worked  out  the  technical  details 
of  those  experiments,  and  by  May  1970  JPL  had  installed  an  X-band  maser  tunable  to  the 
Haystack  frequency.  The  demands  of  the  space  program  on  the  Mars  Station,  however, 
forced  postponement  of  the  experiments.  As  Shapiro  recalled:  "DSN  always  had  schedul- 
ing problems.  Scheduling  was  the  biggest  pain  in  the  neck.  From  the  point  of  view  of  sci- 
ence, I  never  felt  the  best  things  were  done  with  scheduling;  the  engineering  and  mission 
pressures  were  too  enormous.  It  always  seemed  to  be  as  impossible  as  possible  to  schedule 
ground-based  science  experiments,  but  good  science,  in  fact,  was  done."  Goldstack  even- 
tually searched  for  Ganymede  and  Callisto  in  late  May  and  early  June  1970.90 


Jodrell  Bank 


Several  years  before  planetary  radar  astronomy  ended  at  Haystack  and  declined  at 
JPL,  radar  research  at  Jodrell  Bank  came  to  an  end,  too.  In  contrast  to  JPL,  Jodrell  Bank 
officially  recognized  and  funded  its  radar  astronomy  program,  and  Sir  Bernard  Lovell 
proudly  and,  in  the  face  of  adversity,  stubbornly  maintained  radar  research.  The  Jodrell 
Bank  facility  was  an  example  of  British  Big  Science;  private  and  civilian  governmental 
funding  underwrote  the  building  of  the  large  dish.  While  the  U.S.  military  funded  some 
meteor  radar  research,  Jodrell  Bank  radar  astronomy  was  not,  in  any  sense,  an  extension 
of  American  Big  Science.  The  demise  of  planetary  radar  astronomy  at  Jodrell  Bank  was  a 
lesson  in  the  dangers  inherent  in  Little  Science,  not  Big  Science. 

Thanks  to  NASA  and  the  American  military,  Jodrell  Bank  did  not  lack  for  radar 
equipment.  The  still  secret  agreement  between  Lovell  and  an  unidentified  Air  Force  offi- 
cer had  as  its  immediate  objective  the  sending  of  commands  to  the  Pioneer  5  spacecraft. 
The  U.S.  Air  Force  funded  Space  Technology  Laboratories  (STL),  a  Los  Angeles-based 
wholly-owned  subsidiary  of  Ramo-Wooldrige  (later  TRW),  to  install  a  continuous-wave 
410.25-MHz  (73-cm)  radar  transmitter  and  other  equipment  on  the  Jodrell  Bank  tele- 
scope in  order  to  track  lunar  rocket  launches.  Although  the  STL  transmitter  had  only  a 
few  kilowatts  of  power,  it  was  stable,  reliable,  and  free  of  the  problems  that  plagued  the 
pulse  radar  apparatus  pieced  together  by  John  Evans.  Ownership  of  the  STL  transmitter 
passed  to  NASA,  which  provided  operational  funds  between  1959  and  1964  to  track  rock- 
et launches,  not  to  perform  radar  experiments.  NASA  left  the  equipment  on  the  Jodrell 
Bank  antenna  "on  an  indefinite  loan  basis,"  so  that  the  University  of  Manchester  might 
use  it  for  scientific  research.91 


89.  Memorandum,  NEROC  Project  Office  to  Wiesner,  19  September  1968,  regarding  "Proposed 
Contact  with  Newell  Regarding  Possible  Partial  Support  of  Haystack  by  NASA,"  8/2/AC  135,  MITA;  NEROC, 
Proposal  to  the  National  Science  Foundation  for  Programs  in  Radio  and  Radar  Astronomy  at  the  Haystack 
Observatory,  8  May  1970,  pp.  III.8-III.10, 1 .1.1  A;  Brunk  to  Distribution  List,  4  October  1968,  NHOB. 

90.  Shapiro  4  May  1994;  Shapiro  1  October  1993;  "Funding  Proposal,  'Plan  for  NEROC  Operation  of 
the  Haystack  Research  Facility  as  a  National  Radio/Radar  Observatory,'  NSF,  7/1/71-6/30/73,"  26/2/AC  135, 
and  Sebring  to  Hurlburt,  27  March  1970,  1 8/2/AC  135,  MITA;  NEROC,  Proposal  to  the  National  Science 
Foundation  for  Programs  in  Radio  and  Radar  Astronomy  at  the  Haystack  Observatory,  8  May  1970,  pp.  Ill  .8- 
III.  10,  LLLA;  JPL  1970  Annual  Report,  p.  14,  JPLA. 

91.  Lovell,  11  January  1994;  Evans  9  September  1993;  Ponsonby  11  January  1994;  Lovell,  "Astronomer 
by  Chance,"  pp.  322-325  and  328-329;  Edmond  Buckley  to  R.  G.  Lascelles,  8  November  1961,  and  related  doc- 
uments in  2/53,  Accounts;  Able,  Thor,  and  Pioneer  5  materials  in  4/16,  Jodrell  Bank  Miscellaneous;  materials 
in  1/4,  Correspondence  Series  2;  2/53,  2/52,  2/55,  7/55,  8/55,  1/59,  and  3/59,  Accounts;  and  4/16,  Jodrell 
Bank  Miscellaneous,  JBA. 


LITTLE  SCIENCE/BIG  SCIENCE  1 1 3 


In  1962,  the  Jodrell  Bank  radar  group  consisted  of  only  John  Thomson  and  his  grad- 
uate student  John  E.  B.  Ponsonby.  Evans  had  sought  his  fortune  at  Lincoln  Laboratory.  As 
Ponsonby  characterized  the  radar  group,  "We  were  always  two  men  and  a  boy  [K.  S. 
Imrie]."  When  Ponsonby  arrived  at  Jodrell  Bank  in  1960,  he  was  shocked  to  discover  that 
he  was  the  only  one  in  the  radar  group  with  a  flare  for  electronics;  Thomson,  according 
to  Ponsonby,  was  happy  doing  computations.  Jodrell  Bank  radar  astronomy  was  small  not 
only  in  terms  of  staff,  but  also  in  observing  time,  which  varied  between  1  and  10  percent.92 

Thomson  and  Ponsonby  abandoned  much  of  the  equipment  Evans  had  been  using; 
they  used  a  simpler  approach  with  less  technical  risk.  The  old  apparatus  used  vacuum 
tubes;  the  new  was  all  solid-state  digital  electronics.  A  grant  from  the  DSIR  underwrote  the 
cost  of  these  modifications,  as  well  as  the  purchase  of  a  parametric  amplifier  and  spare  kly- 
stron tubes.  The  1962  and  1964  Jodrell  Bank  Venus  radar  experiments  were  carried  out 
with  this  digital  continuous-wave  equipment.93 

The  focus  of  Jodrell  Bank's  Venus  radar  research  after  1962  was  a  bistatic  experiment 
with  the  Soviet  Long-Distance  Space  Communication  Center  located  near  Yevpatoriya  in 
the  Crimea.  The  experiment  was  possible  only  because  Lovell  had  succeeded  in  thawing 
Cold  War  relations.  The  opportunity  came  in  March  1961,  when  Soviet  space  trackers  lost 
contact  with  a  Venus  probe  launched  the  previous  month.  The  Soviet  Academy  of  Sciences 
approached  Lovell  to  use  the  Jodrell  Bank  telescope  to  search  for  signals.  As  the  months 
passed,  and  Jodrell  Bank  attempted  to  make  contact  with  the  probe,  communications 
between  the  British  and  Soviets  increased.  The  collaboration  led  to  the  establishment  of 
a  telex  link  between  Jodrell  Bank  and  the  Yevpatoriya  radar  station,  as  well  as  an  invitation 
for  Lovell  to  visit  the  Soviet  Union  two  years  later. 

The  idea  of  doing  the  bistatic  experiment  came  to  Lovell  during  his  visit  to 
Yevpatoriya,  when  he  discovered  the  extremely  powerful  Soviet  transmitter.  Vladimir 
Kotelnikov,  who  headed  the  Soviet  planetary  radar  effort,  joined  Lovell  as  the  other  mov- 
ing spirit  behind  the  bistatic  project.  An  Iron  Curtain  of  secrecy  hindered  the  project, 
however.  In  order  to  set  up  the  bistatic  radar,  Jodrell  Bank  had  to  know  the  frequency  and 
precise  coordinates  of  the  Yevpatoriya  radar.  The  Soviets  were  loathe  to  disclose  their  fre- 
quency, transmitter  size,  location,  or  even  antenna  dimensions,  but  the  British  established 
those  parameters  step  by  step.  Nonetheless,  the  experiment  did  not  work  initially,  because 
Jodrell  Bank  lacked  the  correct  Doppler  shift.  After  testing  the  bistatic  arrangement  on 
the  Moon,  the  Yevpatoriya  facility  began  to  transmit  radar  signals  to  Venus,  and  Jodrell 
Bank  received  them  from  January  through  March  1966.  Data  tapes  were  delivered  to 
Kotelnikov  by  way  of  the  British  Embassy.  As  a  long-distance  bistatic  radar  experiment,  the 
effort  was  a  first.  However,  it  was  an  opportunity  lost.94 

Ponsonby  set  forth  a  cogent  analysis  of  the  bistatic  Venus  experiment  in  his  disserta- 
tion: "Planetary  radar  has  proved  to  be  a  field  in  which  new  results  are  only  obtained  by 
the  groups  which  have  the  most  sensitive  systems  and  the  data  processing  capacity  to  make 
the  best  use  of  the  data  acquired.  In  both  respects  the  group  at  Jodrell  Bank  has  never 
been  in  a  leading  position."95 

Lovell  disagreed;  the  bistatic  experiment  was  'just  too  late."  JPL  and  Lincoln 
Laboratory  already  had  determined  the  rate  and  direction  of  rotation  of  Venus.  "But  if 


92.  Ponsonby  1 1  January  1994;  summaries  of  telescope  use  in  1/2,  Correspondence  Series,  JBA. 

93.  Ponsonby   11  January   1994;   2/51,  Accounts,  JBA;   Ponsonby,  Thomson,   and  Imrie,    "Radar 
Observations  of  Venus,"  pp.  1-17;  Ponsonby,  Thomson,  and  Imrie,  "Rotation  Rate  of  Venus  Measured  by  Radar 
Observations,  1964,"  Nature  204  (1964):  63-64. 

94.  Lovell,  1 1  January  1994;  Ponsonby  1 1  January  1994;  Lovell,  "Astronomer  by  Chance,"  pp.  370-372; 
Lovell,  Out  of  the.  Zenith,  pp.  186-188  and  201-204;  Ponsonby  and  Thomson,  "U.S.S.R.-U.K.  Planetary  Radar 
Experiment,"  pp.  661-671  in  R.  W.  Beatty,  J.  Herbstreit,  G.  M.  Brown,  and  F.  Horner,  eds.,  Progress  in  Radio  Science, 
1963-1966  (Berkeley:  URSI,  1967);  Ponsonby,  "Planetary  Radar,"  pp.  6.11-6.22. 

95.  Ponsonby,  "Planetary  Radar,"  p.  6.21. 


114  TO  SEE  THE  UNSEEN 


only  my  1963  conversations  and  agreement  with  the  Soviet  Union  could  have  been  facili- 
tated without  trouble  at  this  end  and  without  trouble  at  the  transmitter,"  Lovell  argued, 
"we  would  have  been  first  on  that."96 

Lovell's  analysis,  as  well  as  that  of  Ponsonby,  raises  the  vital  question  of  the  ability  of 
the  Jodrell  Bank  radar  group  to  effectively  compete  against  American  radar  astronomers. 
The  STL  transmitter  operated  in  the  UHF  band  (410.25  MHz;  73  cm).  Although  the 
Arecibo  Observatory  operated  in  the  same  band,  the  trend  in  planetary  radar  astronomy 
was  toward  higher  frequency  ranges,  the  S-band  at  JPL  (and  later  at  Arecibo)  and  the  X- 
band  at  Haystack.  The  higher  frequencies  allowed  the  radar  to  do  much  more  radar 
astronomy  science  than  was  possible  at  UHF. 

Ponsonby  raised  another  point  in  his  dissertation:  "If  a  true  state-of-the-art  transmit- 
ter were  acquired  it  would  cost  an  appreciable  fraction  of  the  cost  of  the  telescope,  and 
clearly  to  justify  investment  on  that  scale  it  would  have  to  be  used  much  more  extensively 
than  would  be  compatible  with  the  predominantly  passive  radio  astronomical  programs  at 
Jodrell  Bank.  Passive  radio-astronomy  may  appropriately  be  done  as  a  secondary  line  of 
research  at  a  primarily  radar  installation,  but  experience  has  shown  that  the  two  activities 
do  not  combine  well  the  other  way.  Appreciating  this,  the  research  reported  in  this  thesis 
is  not,  at  least  for  the  present,  being  pursued  further."  Indeed,  Ponsonby  continued,  'The 
limited  computing  facilities  available  in  the  University  and  the  lack  at  the  time  of  on-line 
computers  at  Jodrell  Bank  in  effect  prevented  a  thorough  analysis  of  the  data  that  was 
acquired,  and  this  took  away  much  of  the  value  of  the  observations."97 

The  acquisition  of  new  radar  and  computer  equipment  certainly  would  have  consti- 
tuted a  significant  expenditure,  but  Lovell  probably  could  have  raised  the  necessary 
money.  Could  Jodrell  Bank  have  kept  up  with  the  development  of  planetary  range- 
Doppler  mapping  in  the  United  States?  Thomson  was  working  on  an  aperture  synthesis 
technique  for  making  lunar  radar  maps.  The  mathematical  process  for  constructing  the 
image  was  analogous  to  that  now  used  for  tomographic  brain  scanners  and  differed  entire- 
ly from  that  used  in  the  United  States  to  construct  range-Doppler  maps.  The  technique 
was  not  very  practical,  however;  it  required  computer  capacity  not  then  available  at  Jodrell 
Bank  and  ultimately  could  not  be  generalized  to  the  planets.98 

In  the  end,  the  small  scale  of  planetary  radar  astronomy  at  Jodrell  Bank  did  it  in. 
Thomson  and  Ponsonby  grew  tired  of  the  Soviet  bistatic  Venus  experiment.  They  carried 
the  main  load  of  the  work  at  irregular  hours  of  the  day  and  night.  Finally,  on  18  March 
1966,  Thomson  and  Ponsonby  could  take  no  more.  They  handed  Lovell  a  list  often  good 
reasons  for  ending  the  experiment.  Kotelnikov  agreed  to  "an  interval"  in  the  observations, 
which  never  resumed.99  Ponsonby  remained  rather  cynical  about  the  venture,  which  he 
has  characterized  as  a  political  exercise.  'The  signals  were  recorded  on  magnetic  tape  and 
sent  off  to  Russia,  and  I  never  heard  from  them  again!"100 

Ponsonby  already  was  tired  of  the  bistatic  experiments,  when  the  death  of  John 
Thomson  from  an  inoperable  brain  tumor  in  August  1969  devastated  the  Jodrell  Bank 
planetary  radar  program.  Without  Thomson,  and  certainly  without  Ponsonby's  interest, 
Jodrell  Bank  had  no  radar  group.  Through  sheer  stubbornness,  however,  Lovell  tried  to 
keep  the  radar  program  going.  In  October  1969,  he  and  his  Jodrell  Bank  colleagues  drew 
up  a  scientific  program  for  a  proposed  122-meter  (400-ft)  telescope,  the  Mark  V.  The  pro- 
gram included  a  series  of  planetary  radar  experiments  outlined  by  Ponsonby.  Was  this  the 


96.  Lovell  11  January  1994. 

97.  Ponsonby,  "Planetary  Radar,"  pp.  6.21-6.22. 

98.  Ponsonby  11  January  1994;  Lovell,  "Astronomer  by  Chance,"  pp.  373-375;  various  documents  in 
2/51,  Accounts,  JBA. 

99.  Lovell,  Out  of  the  Zenith,  pp.  207-208. 

100.  Ponsonby  1 1  January  1994. 


LITTLE  SCIENCE/BIG  SCIENCE  1 1 5 


telescope  that  could  have  revived  Jodrell  Bank  radar  research?  Like  its  American  cousin 
the  NEROC  telescope,  the  Mark  V  was  never  built.  In  retrospect,  Lovell  realized  that  "It 
was  now  out  of  the  question  for  us  to  continue....!  saw  the  passing  of  radar  as  inevitable, 
but  with  regret."101 

The  sixties  was  the  era  of  the  Big  Dish;  large  antenna  projects  came  and  went,  and 
so  did  planetary  radars.  In  1965,  four  antennas  supported  planetary  radar  experiments: 
Arecibo,  Haystack,  Jodrell  Bank,  and  the  Goldstone  Mars  Station.  A  fifth  dish,  the  NEROC 
telescope,  was  on  the  drawing  board.  But  ten  years  later,  the  NEROC  telescope  had  not 
been  built;  Haystack  and  Jodrell  Bank  no  longer  performed  planetary  radar  experiments. 
By  1980,  Goldstone  had  joined  their  number.  Only  Arecibo  remained.  Planetary  radar 
astronomy  appeared  to  be  a  collapsing  field. 

At  Arecibo,  nonetheless,  radar  astronomy  had  found  a  patron  in  NASA.  Planetary 
radar  there  also  had  a  recognized  and  guaranteed  budget,  as  well  as  a  world-class  research 
instrument,  and  both  Cornell  and  MIT  fed  graduate  students  to  the  Arecibo  facility.  Given 
the  financial,  institutional,  technological,  and  other  resources  available  at  Arecibo  for 
planetary  radar  astronomy,  one  would  have  expected  the  field  to  have  occupied  an 
increasing  amount  of  antenna  time  from  1974,  when  Haystack  ceased  radar  astronomy,  to 
1980,  when  JPL  activity  virtually  ended.  Instead,  antenna  use  remained  relatively  stable, 
averaging  about  six  percent  between  1971  and  1980  and  passing  seven  percent  concur- 
rently with  the  inferior  conjunctions  of  Venus.102 

In  terms  of  personnel,  one  could  count  the  field  of  planetary  radar  astronomy  as 
consisting  of  nine  individuals.  At  MIT  was  Gordon  Pettengill;  at  JPL,  Dick  Goldstein,  Ray 
Jurgens,  and  George  Downs.  The  Arecibo  Observatory  supported  four  radar  practition- 
ers: Don  Campbell,  associate  director  at  the  Arecibo  Observatory  since  1979;  John 
Harmon,  AO  research  associate  since  1978;  Steven  J.  Ostro,  Cornell  assistant  professor  of 
astronomy  since  1979;  and  Barbara  Ann  Burns,  a  graduate  student  of  Don  Campbell. 

In  1980,  planetary  radar  astronomy  was  indeed  a  small  field  in  terms  of  available 
instrumentation  and  active  practitioners.  It  was  an  example  of  Little  Science,  but  one 
which  depended  on  Big  Science  for  its  very  existence.  Moreover,  although  that  Big 
Science  had  been  as  diverse  as  military,  space,  ionospheric,  and  radio  astronomy  research 
at  the  emergence  of  radar  astronomy,  by  1980  Big  Science  had  come  to  mean  one  thing: 
NASA.  The  financial  and  institutional  arrangements  with  NASA  influenced  the  kind  of  sci- 
ence done.  In  order  to  understand  how  that  science  was  influenced,  we  must  first  look  at 
the  evolution  of  planetary  radar  astronomy  as  a  science. 


101.  Lovell  1 1  January  1994;  Ponsonby  1 1  January  1994;  Lovell,  Out  of  the  Zenith,  p.  203;  Lovell,  TheJodreU 
Bank  Telescope,  Chapters  5-6  and  9-10,  especially  pp.  55-56  and  257.  In  analyzing  the  demise  of  radar  astronomy 
at  Jodrell  Bank,  though  the  smallness  of  the  active  radar  astronomy  staff,  technical  and  technological  factors, 
and  the  American  lead  had  a  more  determinant  role,  to  be  sure,  one  must  not  overlook  the  lure  of  radio  astron- 
omy. 

102.  These  figures  are  based  on  the  NAIC  quarterly  reports  for  the  years  1971-1980.  The  percentage  of 
radar  use  annually  was  2.9  percent  in  1971;  9.5  percent  in  1972;  6.9  percent  in  1973;  1.9  percent  in  1974;  7.2  per- 
cent in  1975;  5.8  percent  in  1976;  7.3  percent  in  1977;  4.7  percent  in  1978;  5.0  percent  in  1979;  and  7.8  percent 
in  1980.  The  average  percentage  for  the  period  1971-1980  was  5.9,  while  the  average  for  1971-1975  was  5.68  per- 
cent and  for  1976-1980  6.12  percent 


Chapter  Five 

Normal  Science 


Starting  with  the  initial  detections  of  Venus  in  1961,  planetary  radar  astronomy  grew 
rapidly  by  discovering  the  rate  and  direction  of  Venus's  rotation,  by  refining  the  value  of 
the  astronomical  unit,  and  by  rectifying  the  rotational  period  of  Mercury.  Data  gathered 
from  radar  observations  made  at  Haystack,  Arecibo,  and  Goldstone  formed  the  basis  for 
precise  planetary  ephemerides  at  JPL  and  Lincoln  Laboratory.  In  sum,  the  results  of  plan- 
etary radar  astronomers  served  the  needs  of  the  planetary  astronomy  community.  In  addi- 
tion, radar  also  served  to  test  Albert  Einstein's  General  Theory  of  Relativity. 

Planetary  radar  astronomy  concerned  itself  with  two  different  but  related  sets  of 
problems.  One  set  of  problems  related  to  planetary  dynamics  and  ephemerides,  for 
instance,  orbits,  rotational  and  spin  rates,  and  the  astronomical  unit.  A  second  set  related 
to  the  radar  characteristics,  or  what  is  called  the  radar  signature,  of  the  planets,  such  as 
surface  scattering  mechanisms,  dielectric  constants,  and  radar  albedos.  The  latter  prob- 
lems are  epistemological;  that  is,  they  deal  with  how  radar  astronomers  know  what  they 
know. 

What  defines  this  second  set  of  epistemological  problems  is  the  fact  that  planetary 
radar  astronomy  is  based  on  the  use  of  techniques  particular  to  radar.  These  problems 
have  remained  unchanged  over  time.  In  contrast,  the  first  set  of  problems,  those  dealing 
with  planetary  and  dynamics  ephemerides,  have  changed  over  time.  The  nature  of  that 
change  has  been  additive;  at  each  stage  of  change,  new  problems  are  added  to  the  old 
problems,  which  remain  part  of  the  set  of  problems  radar  astronomers  seek  to  solve. 

Both  the  epistemological  and  scientific  sets  of  problems  are  interrelated.  For  exam- 
ple, planetary  radar  astronomers  derive  the  ability  to  solve  astronomical  problems  out  of 
the  resolution  of  epistemological  questions.  The  development  of  range-Doppler  mapping, 
for  example,  led  to  the  solution  of  a  set  of  problems  entirely  different  from  ephemerides 
problems,  yet  the  solution  of  ephemerides  problems  was  sine  qua  non  to  the  creation  of 
range-Doppler  maps.  Conversely,  the  attempts  to  solve  certain  scientific  questions 
required  reconsideration  of  the  radar  techniques  themselves. 

The  philosopher  of  science  Thomas  S.  Kuhn  has  attempted  to  explain  the  conduct 
of  scientific  activity.1  Although  Kuhn  has  used  the  term  "paradigm"  differently  over  time, 
initially  it  had  a  limited  meaning.  Stated  simply,  a  paradigm,  as  used  by  Kuhn,  is  a  core  of 
consensus  within  a  group  of  practitioners.  The  essence  of  the  paradigm  consensus  is  a  set 
of  problems  and  their  solutions.  Planetary  radar  astronomy  quickly  achieved  and  main- 
tained a  paradigmatic  consensus  on  which  problems  to  solve. 

Moreover,  the  field  often  achieved  scientific  success  by  solving  problems  left 
unsolved  or  unsatisfactorily  solved  by  optical  means.  Just  as  radar  astronomy  had  resolved 
earlier  that  meteors  were  part  of  the  solar  system,  so  the  determination  of  the  rotational 
rates  of  Venus  and  Mercury  and  the  refinement  of  the  astronomical  unit  were  astronomi- 
cal problems  inadequately  solved  by  optical  methods,  but  resolved  through  the  analysis  of 
radar  data. 


1.  The  works  of  Kuhn,  which  span  over  thirty  years,  have  been  summarized,  explained,  and  analyzed 
in  Paul  Hoyningen-Huene,  Reconstructing  Scientific  Revolutions:  Thomas  S.  Kuhn's  Philosophy  of  Science,  trans. 
Alexander  T.  Levine  (Chicago:  University  of  Chicago  Press,  1993).  Especially  relevant  to  the  discussion  here  are 
pp.  134-135,  143-154,  169,  188-190  and  193-194. 

117 


118  TO  SEE  THE  UNSEEN 


For  Kuhn,  "normal  science"  was  a  specific  phase  of  scientific  development  distin- 
guished by  universal  consensus  within  a  given  scientific  community  over  the  problems  to 
be  solved  and  the  ways  of  solving  those  problems.  In  other  words,  normal  science  was 
paradigm  science.  Preceding  its  evolution  into  normal  science,  according  to  Kuhn,  a 
scientific  activity  passes  through  a  developmental  phase  in  which  the  problem-solving 
consensus  that  characterizes  normal  science  does  not  yet  exist.  In  this  "preconsensus"  or 
"pre-paradigm"  phase,  and  immediately  before  a  phase  of  normal  science,  groups  of  inves- 
tigators addressing  roughly  the  same  problems  but  from  different,  mutually  incompatible 
standpoints  compete  with  each  other.  As  a  consensus  emerges,  members  of  the  compet- 
ing schools  join  the  group  whose  achievements  are  better,  as  measured  by  scientific  values. 

Planetary  radar  astronomy  did  not  pass  through  Kuhn's  "preconsensus"  phase,  how- 
ever. Complementary,  not  competing,  groups  marked  the  emergence  of  the  field.  The 
"bistatic  radar"  approach  of  Von  Eshleman  at  Stanford  University  complemented  the 
efforts  of  ground-based  planetary  radar  astronomers,  and  that  complementarity  had  been 
Eshleman's  intention.2  Ground-based  planetary  radar  astronomers  distinguished  them- 
selves from  the  Stanford  approach.  In  a  review  article  on  planetary  radar  astronomy 
published  in  1973,  Tor  Hagfors  and  Donald  B.  Campbell,  both  at  the  Arecibo 
Observatory,  explained,  "We  have,  however,  chosen  to  omit  this  work  [space-based  radar] 
here  since  it  is  our  opinion  that  it  properly  belongs  to  the  realm  of  space  exploration 
rather  than  to  astronomy."3  Space  exploration  versus  astronomy,  then,  was  how  planetary 
radar  astronomers  established  turf  lines. 

Planetary  radar  astronomy  was,  above  all  else,  a  set  of  techniques  used  with  large- 
scale  ground-based  radar  systems.  As  a  result,  planetary  radar  was  an  algorithm  in  search 
of  a  problem,  a  data  set  in  search  of  a  question.  Hence,  the  success  of  planetary  radar  inex- 
orably depended  on  its  ability  to  link  its  techniques  and  results  to  the  problem-solving  of 
a  scientific  discipline.  Initially,  those  problems  came  from  planetary  astronomy,  but  as  the 
types  of  techniques  accumulated,  radar  came  to  solve  new  problems  posed  by  planetary 
geology.  Furthermore,  the  solving  of  those  problems  tied  planetary  radar  astronomy  to 
NASA's  space  missions. 

Despite  its  mercurial  nature,  planetary  radar  astronomy  did  exhibit  an  essential  char- 
acteristic of  Kuhn's  normal  science,  a  paradigm.  The  paradigm  consisted  of  a  consensus  on 
a  particular  set  of  problems  (e.g.,  orbital  parameters)  and  agreement  on  a  particular  way 
of  solving  those  problems  (the  analysis  of  range,  Doppler,  and  other  radar  data  obtained 
with  ground-based  radars  from  solar  system  objects) .  The  detections  of  Venus,  Mercury, 
and  Mars  between  1961  and  1963  opened  the  field,  but  rotational  rates,  as  well  as  the 
refinement  of  the  astronomical  unit,  established  the  field.  With  the  successful  application 
of  range-Doppler  mapping  to  Venus,  the  paradigm  began  to  shift  in  a  new  direction. 

Around  the  Sun  in  88  Days 

The  first  radar  detection  of  Mercury  was  announced  by  the  Soviet  scientists  working 
under  Vladimir  A.  Kotelnikov  and  associated  with  the  Institute  of  Radio  Engineering  and 
Electronics  (IREE)  of  the  Soviet  Academy  of  Sciences  and  the  Long-Distance  Space 
Communication  Center  near  Yevpatoriya,  in  the  Crimea.  Kotelnikov's  group  made  53 
radar  observations  of  Mercury  during  the  inferior  conjunction  with  that  planet  in  June 
1962.  At  that  time,  the  distance  from  Earth  to  Mercury  was  between  83  and  88  million 


2.  Eshleman  9  May  1994. 

3.  Hagfors  and  Campbell,  "Mapping  of  Planetary  Surfaces  by  Radar,"  Proceeding!  of  the  IEEE  61 
(September  1973):  1219-1225,  esp.  1224. 


NORMAL  SCIENCE  119 


kilometers,  twice  the  distance  to  Venus  during  inferior  conjunction.  Although  the  weak- 
ness of  the  return  echoes  prevented  their  use  as  a  reliable  indicator  of  the  astronomical 
unit,  Kotelnikov  and  his  colleagues  claimed  a  technical  tour  de  force  and  a  first  in  plane- 
tary radar  astronomy.4 

Richard  Goldstein  and  Roland  Carpenter  at  JPL  took  up  the  Soviet  challenge  and 
bounced  radar  waves  off  Mercury  the  following  year  in  May  1963  using  the  Goldstone 
experimental  radar.  The  experiment  established  a  distance  record  that  overshadowed  the 
Soviet  claim.  Mercury  was  then  farther  from  Earth,  over  97  million  kilometers  away.  In 
addition,  the  JPL  experiment  confirmed  what  astronomers  already  knew  about  Mercury, 
that  its  period  of  rotation  was  88  days.  Goldstein  had  no  reason  to  believe  it  was  other- 
wise.5 

However,  when  Gordon  Pettengill  and  Rolf  Dyce  observed  Mercury  in  April  1965 
with  the  new  Arecibo  telescope,  they  reported  a  rotational  rate  of  59  ±  5  days.  This  dis- 
covery, one  of  the  earliest  major  achievements  of  planetary  radar  astronomy,  astounded 
astronomers,  who  sought  to  explain  the  new,  correct  rotational  rate.  As  Pettengill  and 
Dyce  concluded,  'The  finding  of  a  value  for  the  rotational  period  of  Mercury  which  dif- 
fers from  the  orbital  period  is  unexpected  and  has  interesting  theoretical  implications.  It 
indicates  either  that  the  planet  has  not  been  in  its  present  orbit  for  the  full  period  of  geo- 
logical time  or  that  the  tidal  forces  acting  to  slow  the  initial  rotation  have  not  been  cor- 
rectly treated  previously."6 

Pettengill,  Dyce,  and  Irwin  Shapiro  next  published  a  lengthier  discussion  of  their 
radar  determination  of  Mercury's  59-day  rotational  period  based  on  additional  observa- 
tions made  in  August  1965. 7  Working  with  Giuseppe  "Bepi"  Colombo,  an  astronomer 
from  the  University  of  Padova  visiting  the  Smithsonian  Astrophysical  Observatory,  Shapiro 
began  to  develop  an  explanation  for  the  new  rotational  period.  Colombo,  Shapiro 
recalled,  "realized  almost  immediately  that  58.65  days  was  exactly  two-thirds  of  88  days. 
Mercury  probably  was  locked  into  a  spin  such  that  it  went  around  on  its  axis  one-and-a- 
half  times  for  every  once  around  the  planet.  The  same  face  did  not  always  face  the  Sun. 
That  meant  that  near  Mercury's  perihelion,  that  is,  when  its  orbit  is  closest  to  the  Sun, 
Mercury  tends  to  follow  the  Sun  around  in  its  orbit.  Near  perihelion,  then,  the  orbital 
motion  and  spin  rotation  of  Mercury  were  very  closely  balanced,  so  that  Mercury  almost 
presented  the  same  face  to  the  Sun  during  this  period."8 

In  a  joint  paper,  Colombo  and  Shapiro  analyzed  Mercury  radar  data,  as  well  as  opti- 
cal observations  from  the  past,  and  presented  a  preliminary  model.9  In  a  seminal  paper, 
Peter  Goldreich  and  Stanton  J.  Peale  pointed  out  the  need  to  consider  the  capture  of 
Mercury  into  the  resonant  rotation  as  a  probabilistic  event.  If  initial  conditions  during  the 


4.  Kotelnikov,  G.  Ya.  Guskov,  Dubrovin,  Dubinskii,  Kislik,  Korenberg,  Minashin,  Morozov,  Nikitskiy, 
Pctrov,  G.  A.  Podoprigora,  Rzhiga,  A.  V.  Frantsesson,  and  Shakhovskoy,  "Radar  Observations  of  the  Planet 
Mercury,"  Soviet  Physics — Doklady  1  (1963):  1070-1072.  Given  the  stated  weakness  of  the  Mercury  echoes,  as  well 
as  their  difficulty  in  obtaining  accurate  and  verifiable  Venus  results,  the  Soviet  announcement  of  a  detection  of 
Mercury,  a  much  farther  radar  target  than  Venus,  raised  doubts  in  the  United  States  about  the  validity  of  the 
Soviet  claims. 

5.  Carpenter  and  Goldstein,  "Radar  Observations  of  Mercury,"  Science  142  (1963):  381. 

6.  Pettengill  and  Dyce,  "A  Radar  Determination  of  the  Rotation  of  the  Planet  Mercury,"  Nature  206 
(19  June  1965):  1240. 

7.  Dyce,  Pettengill,  and  Shapiro,  "Radar  Determination  of  the  Rotations  of  Venus  and  Mercury,"  The 
Astronomical  Journal  72  (1967):  351-359. 

8.  Shapiro  30  September  1993;  Giuseppe  Colombo,  "Rotational  Period  of  the  Planet  Mercury,"  Nature 
208  (1965):  575. 

9.  Colombo  and  Shapiro,  "The  Rotation  of  the  Planet  Mercury,"  The  Astrophysical  Journal  145  (1966): 
296-307.  Earlier,  it  had  appeared  as  an  internal  SAO  publication:  Colombo  and  Shapiro,  The  Rotation  of  the  Planet 
Mercury,  SAO  special  report  no.  188  (Cambridge:  SAO,  13  October  1965). 


120  TO  SEE  THE  UNSEEN 


formation  of  the  solar  system  had  been  slightly  different,  the  capture  may  not  have  taken 
place.10 

Irwin  Shapiro's  graduate  student,  Charles  C.  Counselman  III,  then  did  his  doctoral 
thesis  on  the  rotation  of  Mercury.  Counselman  developed  a  theory  of  capture,  escape, 
recapture,  and  escape,  as  the  eccentricity  of  Mercury's  orbit  changed,  in  a  two-dimen- 
sional statistical  model  of  the  capture  problem.  Later,  Norman  Brenner,  a  graduate  stu- 
dent working  with  both  Shapiro  and  Counselman,  expanded  the  analysis  into  a  three- 
dimensional  model  in  his  1975  doctoral  dissertation.  Meanwhile,  Stan  ton  Peale  published 
his  own  three-dimensional  analysis.11 

The  Outer  Limits 

Although  Venus  became  the  prime  target  of  planetary  radar  astronomers,  other 
planets  drew  their  attention  from  the  earliest  opportunity  to  detect  echoes  from  that  plan- 
et. Richard  Goldstein  made  the  first  radar  detection  of  Mars  during  the  opposition  of 
February  1963,  when  the  distance  to  Mars  from  Earth  was  over  100  million  kilometers. 
Goldstein  found  Mars  "a  very  difficult  radar  target  because  of  its  great  distance  from  Earth 
and  rapid  rate  of  rotation."12 

Mars  defined  the  farthest  limits  of  planetary  radar  detections  until  after  the  addition 
of  the  S-band  radar  to  the  Arecibo  telescope  and  the  X-band  upgrade  of  the  Goldstone 
Mars  Station.  Farther  out,  neither  American  nor  Soviet  efforts  ever  resulted  in  an  unam- 
biguous radar  detection  of  Jupiter.  Certainly  no  echoes  returned  from  any  solid  surface 
features.  Nonetheless,  US  and  Soviet  investigators  claimed  detections.  The  case  of  Jupiter 
demonstrates  the  difficulty  of  obtaining  radar  echoes  from  a  "soft"  target,  that  is,  one  that 
is  not  a  solid  body,  especially  at  such  an  extreme  distance. 

Soviet  investigators  working  with  Vladimir  Kotelnikov  at  the  \evpatoriya  radar  center 
claimed  to  have  detected  radar  echoes  from  Jupiter  as  early  as  September  1963  in  the  29 
December  1963  issue  of  Pravda.  The  planet  was  in  opposition  at  a  distance  of  about  600 
million  kilometers,  six  times  farther  than  Mars  at  opposition  in  1963.  Not  surprisingly, 
Kotelnikov  and  his  colleagues  reported  that  the  echoes  were  weak.13 

Between  17  October  and  23  November  1963,  during  the  same  opposition  of  Jupiter, 
Dick  Goldstein  attempted  observations  of  the  planet  with  the  Goldstone  experimental 
radar.  He  found  few  if  any  echoes.  Occasionally,  though,  a  single  run  did  indicate  a  "sta- 
tistically significant"  return.  Goldstein  noticed  that  the  time  interval  between  these  "sig- 
nificant" returns  were  most  often  a  multiple  of  the  rotation  period  of  Jupiter,  about  10 
hours.  It  seemed  that  a  single  localized  area  on  Jupiter,  which  did  not  coincide  with  the 
celebrated  red  spot,  was  both  a  good  and  a  smooth  reflector  of  radar  waves. 


10.  Shapiro  30  September  1993;  Peter  Goldreich,  Tidal  De-spin  of  Planets  and  Satellites,"  Nature  208 
(1965):  375-376;  Goldreich  and  Stanton  Peale,  "Resonant  Spin  States  in  the  Solar  System,"  Nature  209  (1966): 
1078-1079;  Goldreich,  "Final  Spin  States  of  Planets  and  Satellites,"  The  Astronomical  Journal  71  (1966):  1-7; 
Goldreich  and  Peale,  "Spin-Orbit  Coupling  in  the  Solar  System,"  The  Astronomical  Journal  7 1  (1966):  425-438. 
Also,  in  a  joint  paper,  Peale  and  Gold  attempted  to  explain  the  rotational  period  of  Mercury  in  terms  of  a  solar 
tidal  torque  effect.  Peale  and  Gold,  "Rotation  of  the  Planet  Mercury,"  Nature  206  (1965):  1241-1242. 

11.  Shapiro  30  September  1993;  Counselman,  "Spin-Orbit  Resonance  of  Mercury,"  Ph.D.  diss.,  MIT, 
February  1969.  See  also  Counselman,  The  Rotation  of  the  Planet  Mercury,"  Chapter  14,  pp.  89-93  in  R.  G. 
Stern,  ed.,  Review  of  NASA  Sponsored  Research  at  the  Experimental  Astronomy  Laboratory  (Cambridge:  MIT,  1967). 

12.  Goldstein  and  Willard  F.  Gillmore,  "Radar  Observations  of  Mars,"  Science  141  (1963):  1171-1172. 

13.  Memorandum,  O.  Koksharova  to  I.  Newian,  9  January  1964,  translation  of  Pravda  article,  microfilm 
22-314,  JPL  Central  Files.  The  article  later  appeared  as  Kotelnikov,  Apraksin,  Dubrovin,  Kislik,  Kuznetsov,  Petrov, 
Rzhiga,  Frantsesson,  and  Shakhovskoi,  "Radar  Observations  of  the  Planet  Jupiter,"  Soviet  Physics-Doklady  9  ( 1964) : 
250-251. 


NORMAL  SCIENCE  121 


To  investigate  further,  Goldstein  divided  Jupiter  into  eight  "time  zones"  and  aver- 
aged all  the  runs  which  illuminated  a  single  "time  zone."  The  zone  centered  about  the 
Jovian  longitude  32°  gave  a  response  that  Goldstein  characterized  as  "statistically  signifi- 
cant," although,  he  admitted,  "this  detection  cannot  be  considered  absolutely  conclusive." 
The  amount  of  return  was  simply  too  high  to  be  believable.  Goldstein  later  attempted  to 
obtain  echoes  from  Jupiter,  using  a  Goldstone  radar  that  was  "a  hundred  times  better,"  but 
he  did  not  find  any  echoes.  "We  never  were  able  to  repeat  it,"  he  confessed.14 

During  the  next  oppositions  of  Jupiter,  in  November  1964,  December  1965,  and 
February  1966,  Gordon  Pettengill,  Rolf  Dyce,  and  Andy  Sanchez,  from  the  University  of 
Puerto  Rico  at  Rio  Piedras,  bounced  radar  waves  off  Jupiter  using  the  430-MHz  Arecibo 
telescope.  They  designed  their  experiments  to  duplicate  both  the  Soviet  and  JPL 
approaches;  however,  they  failed  to  validate  either  the  Soviet  or  JPL  claims. 

The  Arecibo  investigators  obtained  results  that  were  many  times  smaller  than  those 
reported  by  Goldstein.  As  for  the  Soviet  results,  which  were  close  to  the  noise  level,  the 
Arecibo  investigators  concluded:  'The  results  reported  in  the  U.S.S.R.,  which  exceed  the 
associated  system  noise  by  only  1.3  standard  deviations  of  the  fluctuations  in  that  noise, 
should  probably  not  be  taken  seriously."  The  Arecibo  investigators  suggested  that  the 
echoing  mechanism  was  located  in  the  upper  levels  of  Jupiter's  atmosphere  "and  that 
echoes  might  be  returned  only  in  exceptional  circumstances."  They  concluded:  "Many 
more  observations  of  Jupiter  spanning  a  long  period  of  time  and  carried  out  at  many  wide- 
ly separated  frequencies  must  be  made  before  the  behavior  of  Jupiter  as  a  radar  target  can 
begin  to  be  understood."15 

Those  observations  never  took  place.  Jupiter  remained  a  misunderstood  and  disre- 
garded radar  target.  The  outer  reaches  of  planetary  radar  astronomy  remained  confined 
to  the  terrestrial  planets.  Jupiter  and  Saturn  had  to  await  the  Arecibo  S-band  and  the 
Goldstone  X-band  upgrades.  Even  then,  however,  planetary  radar  astronomers  focused  on 
solid  targets,  Jupiter's  Galilean  moons  and  Saturn's  rings. 

Icarus  Dicarus  Dock 

In  contrast  to  the  attempts  on  Jupiter,  the  radar  detection  of  Icarus  was  unambigu- 
ous. Icarus  is  an  Earth-crossing  asteroid,  meaning  its  orbit  around  the  Sun  crosses  that  of 
Earth.  On  occasion,  Icarus  comes  within  6.4  million  kilometers  of  Earth,  as  it  did  in  June 
1968.  Nonetheless,  Icarus  was  a  difficult  radar  target,  because  of  its  small  size.  Its  radar 
detectability  was  extremely  small,  one  thousandth  that  of  Mercury  at  its  closest  approach 
and  only  10"12  (one  trillionth)  that  of  the  Moon.16 

Only  Haystack  and  the  Goldstone  Mars  Station  succeeded  in  detecting  the  asteroid. 
Although  Icarus  was  within  the  declination  coverage  of  Arecibo,  attempts  on  15  and  16 
June  1968  yielded  ambiguous  results.  "A  successful  search  would  have  been  more  likely," 
Rolf  Dyce  reported,  "if  the  full  performance  of  the  line  feed  had  been  available."17 

Investigators  at  Haystack  Observatory  leaped  over  imposing  hurdles  to  make  the  first 
radar  detection  of  Icarus.  Irwin  Shapiro  and  his  Lincoln  Laboratory  colleagues  prepared 
an  ephemeris  based  on  71  optical  observations  of  Icarus  between  1949  and  1967.  Radar 
observation  began  in  earnest  at  Haystack  on  the  morning  of  12  June  1968.  Late  that 


14.  Goldstein  14  September  1993;  Goldstein,  "Radar  Observations  of  Jupiter,"  Science  144  (1964): 
842-843. 

15.  Dyce,  Pettengill,  and  Sanchez,  "Radar  Observations  of  Mars  and  Jupiter  at  70  cm,"  The  Astronomical 
Journal72  (1967):  Ill-Ill. 

16.  Goldstein,  "Radar  Observations  of  Icarus,"  Science  162  ( 1968) :  903. 

17.  Dyce,  "Attempted  Detection  of  the  Asteroid  Icarus,"  in  AIO,  Research  in  Ionospheric  Physics,  Research 
Report  RS  74  (Ithaca:  CRSR,  31  July  1968),  pp.  90-91. 


122  TO  SEE  THE  UNSEEN 


evening,  the  Haystack  observers  received  a  new  set  of  optical  positions  from  astronomer 
Elizabeth  Roemer  at  the  University  of  Arizona.  Michael  Ash,  of  Lincoln  Laboratory  Group 
63,  immediately  integrated  the  optical  data  into  the  radar  ephemeris,  and  by  midnight 
Haystack  was  observing  with  the  new  ephemeris. 

Despite  these  heroic  efforts  to  organize  an  improved  ephemeris,  rain,  which  severe- 
ly attenuates  X-band  radar  signals,  bedeviled  the  observations.  As  a  result,  Haystack  did 
not  obtain  a  reasonably  firm  indication  of  an  echo  from  Icarus  until  the  afternoon  of  13 
June.  Another  particularly  successful  run  that  evening  confirmed  the  presence  of  an  echo, 
and  by  the  morning  of  14  June  success  was  certain.  Haystack  terminated  observations  the 
morning  of  15  June.  To  achieve  its  results,  the  Haystack  radar  had  operated  non-stop  for 
20  hours.  Analysis  of  the  data  suggested  that  the  radius  of  Icarus  was  between  0.8  and  1.6 
km. 

The  effort  to  detect  Icarus  in  spite  of  the  rain  and  the  difficult  nature  of  the  aster- 
oid as  a  radar  target  inspired  Louis  P.  Rainville,  a  Lincoln  Laboratory  technician  who  par- 
ticipated in  the  observations,  to  compose  the  following  poem:18 

Anode  to  Icarus 
Icarus  Dicarus  Dock 
We  worked  around  the  clock 
For  three  straight  days 
We  aimed  our  rays 
And  an  echo  showed  on  the  plot. 

But  as  always,  there's  a  woe 

The  rain  made  a  better  show 

As  bleary  our  eyes 

Stared  at  the  skies 

We  hoped  that  the  clouds  would  go. 

Oh  for  the  roar  and  yell 

And  the  glory  for  old  double  "L  " 

If  on  that  crucial  day 

When  it  came  and  went  away 

We'd  had  one  more  decibel! 

Now  as  Icarus  speeds  from  our  sphere 
These  words  are  for  all  men  to  hear 
T'was  a  good  show  men! 

Let's  try  again 

In  another  nineteen  years! 

And  so  this  was  to  be  our  lot 
We  hoped  for  more  than  we  got 
But  we  beat  the  worst; 
Wediditfirstl 
Icarus  Dicarus  Dock 

EURICARUS! 


18.  "Weekly  Reports,  5/13/68-8/11/69,"  36/2/AC  135,  MITA.  The  results  appeared  as  Pettengill, 
Shapiro,  Michael  E.  Ash,  Ingalls,  Louis  P.  Rainville,  Smith,  and  Melvin  L.  Stone,  "Radar  Observations  of  Icarus," 
Icarus  10  (1969):  432-435. 


NORMAL  SCIENCE  123 


Although  Rainville's  verse  implied  a  contest  to  detect  Icarus,  no  such  competition 
existed;  notwithstanding  the  rain,  the  spin  direction  of  the  Earth  would  assure  Haystack 
the  first  look  at  the  asteroid.  At  JPL,  Dick  Goldstein  also  successfully  detected  Icarus  on 
14- 16  June  1968.  Goldstein  used  a  bistatic  radar;  the  Mars  Station  received  signals  from  a 
newly-developed  450-kilowatt  transmitter  installed  on  a  nearby  26-meter  (85-ft)  dish. 
Although  the  Goldstone  transmitter  had  nearly  twice  the  power  of  Haystack  Observatory, 
it  still  received  only  weak  echoes.19 

Using  optical  methods,  asteroid  astronomers  Tom  Gehrels,  Elizabeth  Roemer,  and 
others  calculated  values  for  the  period  and  the  direction  of  the  spin  axis  of  Icarus  and 
found  that  it  appeared  to  be  a  rough  stony-iron  body,  nearly  spherical,  with  nonuniform 
reflectivity  over  the  surface  and  with  a  spin  period  of  2  hours  and  16  minutes.  Its  radius, 
they  calculated,  was  at  least  750  meters,  which  was  close  to  the  low  end  of  the  Haystack 
estimate.  Armed  with  these  results,  Goldstein  then  reinterpreted  his  radar  data  and  con- 
cluded that  the  surface  of  the  asteroid  was  rocky  and  varied  in  roughness.20 

The  detection  of  Icarus  was  an  important  achievement  of  planetary  radar,  the  first 
detection  of  an  asteroid.  Icarus  also  served  to  bring  together  radar  and  optical  planetary 
astronomers  in  a  special  symposium  on  Icarus  organized  by  Gordon  Pettengill  and 
chaired  by  Arvydas  Kliore.  Held  in  Austin,  Texas,  on  10  December  1968,  the  symposium 
was  part  of  the  pre-inaugural  meeting  of  the  Division  for  Planetary  Science  (DPS)  of  the 
American  Astronomical  Society  (AAS) .  Appropriately,  the  symposium  papers  appeared  in 
the  journal  of  planetary  science  Icarus.^ 

The  Icarus  symposium  was  a  pivotal  moment  for  both  planetary  radar  astronomy 
specifically  and  planetary  astronomy  in  general.  Previously,  no  organization  dedicated 
exclusively  to  planetary  astronomy  existed.  The  AAS  had  approved  the  formation  of  the 
DPS  only  a  few  months  earlier  in  August  1968.  In  1973,  the  DPS  opened  its  ranks  to  plan- 
etary scientists  other  than  AAS  members,  such  as  chemists,  geologists,  and  geophysicists, 
and  the  DPS  endorsed  Icarus  as  the  primary  publication  for  planetary  research.  Under  the 
editorial  direction  of  Carl  Sagan,  a  champion  of  radar  astronomy,  Icarus  began  to  solicit 
more  articles  in  planetary  astrophysics,  as  opposed  to  the  earlier  focus  on  celestial 
mechanics.22 

The  Icarus  symposium  typified  the  normal  science  paradigm  of  planetary  radar 
astronomy  in  the  1960s.  Activity  centered  on  detecting  a  solar  system  object  with  a  ground- 
based  radar  instrument  and  analyzing  range  and  Doppler  data  to  obtain  information  on 
orbital  parameters  and  radii  and  related  questions.  Radar  astronomers  then  presented 
these  results  to  asteroid  astronomers,  echoing  the  fruitful  joining  of  radar  observers  and 
astronomers  that  led  to  the  discovery  of  the  origin  of  meteors. 

The  Planetary  Ephemeris  Program 

Starting  in  the  1960s,  the  raw  data  for  the  improvement  of  planetary  ephemerides 
was  provided  by  the  accumulation  of  radar  range  and  other  data.  Traditional  observations 
of  planetary  positions  involved  only  angular  determinations,  which  provide  a  position  in 
a  two-dimensional  plane  (the  sky).  Radar  added  new  dimensions  with  range  and  Doppler 
shift  data  and  included  the  astronomical  unit  and  the  radii  and  masses  of  Mercury,  Mars, 


19.  Goldstein,  "Icarus,"  pp.  903-904. 

20.  T.  Gehrels,  E.  Roemer,  R.  C.  Taylor,  and  B.  H.  Zellner,  "Minor  Planets  and  Related  Objects:  4. 
Asteroid  (1566)  Icarus,"  The  Astronomical  Journal  75  (1970):  186-195;  J.  Veverka  and  W.  Liller,  "Observations  of 
Icarus:  1968,"  Icarus  10  (1969):  441-444;  Goldstein,  "Radar  Observations  of  Icarus,"  Icarus  10  (1969):  430-431. 

21.  "Editor's  Introduction  to:  A  Symposium  on  Icarus,"  Icarus  10  (1969):  429. 

22.  Tatarewicz,  pp.  122-123. 


1 24  TO  SEE  THE  UNSEEN 


and  Venus.  JPL  and  Lincoln  Laboratory  undertook  separate  radar  ephemerides  pro- 
grams. 

The  Lincoln  Laboratory  radar  ephemerides  program,  known  as  the  Planetary 
Ephemeris  Program  or  PEP,  had  its  roots  in  the  anti-ICBM  early  warning  systems.  As  a 
member  of  a  Lincoln  Laboratory  task  force  charged  with  the  early  detection  of  incoming 
enemy  ICBMs  with  radar,  Irwin  Shapiro  became  expert  in  the  mathematics  of  deducing 
ballistic  missile  trajectories  from  radar  observations.  He  wrote  up  his  results  in  a  Lincoln 
Laboratory  report  in  early  1957.  After  the  launch  of  Sputnik,  the  New  York  publishing 
house  McGraw-Hill  released  Shapiro's  report  as  a  book  in  April  1958,  because  his  ballistic 
missile  techniques  were  applicable  (with  some  modification)  to  satellite  tracking.  That 
book  then  became  the  basis  for  the  JPL  ephemeris  program.23 

Shapiro  and  the  radar  group  at  Arecibo  worked  very  closely  on  gathering  data  for 
the  Lincoln  Laboratory  planetary  radar  ephemerides.  As  Don  Campbell  explained,  "He 
has  always  been  our  ephemerides  person,  and  we  provide  him  with  input."24  The  close 
connection  between  the  Arecibo  and  MIT  Lincoln  Laboratory  groups  resulted  from  the 
appointment  of  Gordon  Pettengill  of  Lincoln  Laboratory  as  trie  first  associate  director  of 
the  Arecibo  Ionospheric  Observatory.  Pettengill  set  up  the  program  so  that  the  Arecibo 
radar  ephemerides  would  always  come  from  the  PEP  group. 

Acquiring  input  for  the  PEP  required  extensive  data  taking  that  involved  long  hours 
of  observations,  often  late  at  night.  Don  Campbell  and  Ray  Jurgens,  both  graduate 
students  at  the  time,  did  a  lot  of  the  work  on  Venus,  Mars,  and  Mercury,  under  the  super- 
vision of  Rolf  Dyce  and  Gordon  Pettengill.  Campbell  remembered  the  Mars  observations 
in  particular:25 

This  involved  a  lot  of  late  nights,  unfortunately,  because  the  Mars  opposition  was 
around  midnight.  Every  time  the  radar  system  was  used,  you  had  to  go  up  to  the  sus- 
pended platform  and  actually  change  the  receiver  over.  Then  you  had  to  go  up  after  you 
finished  to  change  them  over  again.  Since  I  was  very  much  at  the  lowest  end  of  the  totem 
pole  at  the  time,  it  was  my  job  to  get  on  the  cable  car,  go  up  to  the  structure,  dabble  with 
the  thing  late  at  night,  change  the  receivers,  come  back,  then  when  we  finished,  go  back 
up  and  change  them  again.  I  suppose  in  retrospect  you  think  of  it  as  painful,  although 
at  the  time  I  don't  remember  being  particularly  worried  about  it.  I  probably  thought  it  was 
fun  initially,  although  there  were  a  lot  fewer  fences  and  safety  devices  on  the  platform  then 
than  there  are  now.  It  was  quite  possible  to  fall  right  through  the  thing. 

The  initial  PEP  calculations  performed  with  the  planetary  radar  data  served  to  refine 
the  astronomical  unit.  Shapiro,  however,  also  saw  the  need  to  refine  the  planetary 
ephemerides  and  the  planetary  masses.  "It  was  also  clear  to  me,"  he  explained,  "that  we 
should  not  do  it  the  way  astronomers  did,  that  is,  with  analytical  series  expanded  out  to 
huge  numbers  of  terms.  It  seemed  to  me  that  with  computers,  even  with  those  available  at 
that  time,  we  should  be  able  to  do  this  numerically,  integrating  the  equations  of  the 
motions  of  the  planets,  integrating  the  partial  derivatives,  and  doing  everything  digital- 
ly.'^ 

The  PEP  required  a  large  computer  as  well  as  an  immense  computer  program. 
Today,  the  program  has  well  over  100,000  Fortran  statements.  Computer  programming, 


23.  Shapiro,  Prediction  of  Ballistic  Missile  Trajectories  from  Radar  Observations  (New  York:  McGraw-Hill, 
1958);  Shapiro  4  May  1994. 

24.  Campbell  9  September  1993. 

25.  Campbell  7  December  1993. 

26.  Shapiro  30  September  1993. 


NORMAL  SCIENCE  125 


however,  was  not  Shapiro's  forte.  "I  am  pretty  much  a  computer  ignoramus,"  he  confessed. 
So  he  hired  a  summer  student,  Michael  E.  Ash,  who  was  a  Princeton  graduate  student  in 
mathematics.  After  graduating  from  Princeton,  Ash  worked  at  Lincoln  Laboratory  for 
about  twelve  years  before  taking  a  position  at  MIT's  Draper  Laboratory.  Ash  was  the  chief 
architect  of  the  PEP  computer  program.  John  F.  Chandler,  a  graduate  student  of  Shapiro, 
took  over  the  PEP  from  Ash  and  worked  on  it  for  over  twenty  years.  Chandler  expanded 
its  applications  so  that  now,  in  the  words  of  Shapiro,  "it  does  everything  but  slice  bread." 

Originally,  PEP  also  analyzed  optical  observations  of  the  Sun,  Moon,  and  planets, 
including  optical  data  from  the  U.S.  Naval  Observatory  back  to  1850.  "I  spent  more  time 
than  I  care  to  admit,"  Shapiro  confessed,  "transferring  to  machine-readable  form  all  the 
optical  observations  recorded  in  history  since  1750  of  the  Sun,  Moon,  and  planets.  In  the 
end,  I  didn't  think  it  was  worth  it.  I  never  published  our  results,  to  Michael  Ash's  chagrin. 
We  had  this  manuscript  about  so  high  [nearly  seven  and  a  half  centimeters  or  three  inch- 
es], but  I  could  never  find  enough  time  to  polish  it  to  my  satisfaction.  History  passed  us 
by.  That  was  the  biggest  unfinished  task  of  my  life.  Michael  Ash  put  in  a  lot  of  work  on 
that,  though  not  as  much  as  I  did.  But  the  ball  was  in  my  court  to  finish  it  off,  and  I  did 
not  do  it.  So  this  is  a  guilt  session."27 

Today  the  PEP  is  a  very  complicated  program  that  analyzes  a  variety  of  observations, 
including  lunar  laser  ranging  data.  When  he  moved  to  Draper  Laboratory,  Michael  Ash 
modified  it  for  satellite  and  lunar  work.  It  is  still  used  in  planetary  radar  and  by 
astronomers  at  the  Harvard-Smithsonian  Center  for  Astrophysics.  It  can  process  pulsar  as 
well  as  Very  Long  Baseline  Interferometry  (VLBI)  observations.  For  a  while,  most  of  the 
pulsar  observers  in  the  world  used  the  PEP;  however,  they  shifted  to  the  JPL  ephemeris 
program  in  recent  years.  A  lack  of  funding  has  left  the  PEP  just  able  to  keep  up  with  the 
Arecibo  ephemeris  work. 

In  contrast,  JPL  has  had  the  manpower  and  funding  to  support  it.  JPL  developed  its 
radar  planetary  ephemerides  to  support  NASA  spacecraft  missions.  Today,  the  JPL  plane- 
tary ephemeris  program,  under  the  direction  of  E.  Myles  Standish,  Jr.,  employs  about  a 
half  dozen  people  who  work  on  planetary,  lunar,  cometary,  asteroidal,  and  satellite 
ephemerides.  JPL  initially  called  their  ephemeris  programs  DE  followed  by  the  version 
number,  with  DE  standing  for  "Development  Ephemeris."  In  the  late  seventies,  JPL  sent 
over  fifty  copies  of  its  ephemeris  DE-96  to  observatories,  space  agencies,  and  astronomical 
research  groups  around  the  world. 

Next  came  the  DE-200  series,  which  used  a  new  equator  and  equinox.  All  major 
national  almanac  offices,  including  the  U.S.  Naval  Observatory,  and  the  French,  British, 
German,  Japanese,  and  Russian  almanac  offices,  now  use  the  JPL  DE-200  ephemeris  pro- 
gram, as  do  many  universities,  the  European  Space  Agency,  and  radio  astronomers. 
Moreover,  the  DE-200  program,  formerly  available  on  magnetic  tape,  now  is  distributed 
through  the  Internet  as  an  FTP  file.28 

The  Lincoln  Laboratory  and  JPL  planetary  ephemeris  programs  were  uses  of  plane- 
tary radar  data  that  did  not  necessarily  lead  to  publications.  Moreover,  the  vast  amount  of 
data  routinely  collected  by  radar  astronomers  and  stored  in  the  data  bases  of  those 
ephemeris  programs  did  not  result  from  experiments  designed  to  achieve  a  special  pur- 
pose. Many  planetary  radar  experiments  quickly  became  routine  operations.  A  glance  at 
the  extant  Haystack  radar  log  books  indicates  that  radar  astronomers  rarely  ran  experi- 
ments themselves;  expert  technicians,  like  Haines  Danforth  and  Lou  Rainville,  operated 


27.  Shapiro  30  September  1993. 

28.  Shapiro  30  September  1993;  Shapiro  4  May  1994;  E.  Myles  Standish,  Jr.,  telephone  conversation, 
20  May  1994;  Paul  Reichley,  telephone  conversation,  19  May  1994;  Memorandum,  Standish  to  R.  Green,  10  May 
1979, Jurgens  materials. 


1 26  TO  SEE  THE  UNSEEN 


the  radar  equipment,  and  the  software  consisted  of  "cookbook  programs."29  This  rou- 
tinization  of  experimentation  is  one  aspect  of  Kuhnian  "normal"  or  paradigm  science. 

Testing  Albert  Einstein 

According  to  Shapiro  and  his  colleagues  at  Lincoln  Laboratory,  the  main  purpose  in 
gathering  radar  data  for  the  planetary  ephemeris  program  was  "to  test  Einstein's  theory 
of  General  Relativity."30  The  Shapiro  test  of  the  gravitational  time  delay  predicted  by 
General  Relativity  is  interesting  for  its  contribution  to  theoretical  physics  and  astrophysics, 
as  well  as  a  major  early  achievement  of  planetary  radar.  Its  development  underscores  the 
close  and  necessary  connection  between  the  capabilities  of  radar  instruments  and  the 
kinds  of  scientific  problems  that  one  can  solve  with  radar.  It  also  illustrates  the  emotional 
intensity  with  which  scientists  struggle  to  assert  their  claims  of  discovery  and  priority  of 
publication. 

After  announcing  his  theory  of  Special  Relativity  in  1905,  Albert  Einstein  spent 
another  ten  years  developing  the  theory  of  General  Relativity.31  The  theory  of  General 
Relativity  traditionally  has  found  support  in  three  principal  experimental  areas.  The  first 
came  from  its  accounting  for  the  precession  of  Mercury's  perihelion,  the  point  at  which 
Mercury  is  closest  to  the  Sun.  Traditional  theoretical  physics  had  been  incapable  of 
explaining  the  precession  of  Mercury's  perihelion  without  leaving  certain  discrepancies 
unexplained.  The  ellipse  of  Mercury's  orbit  was  turning  faster  than  traditional  physics  said 
it  ought  to  by  an  amount  of  some  43  seconds  of  arc  per  century.  Einstein  found  that  his 
equations  gave  just  that  amount  of  deviation  from  the  measure  predicted  by  traditional 
physics.  The  perihelion  motion  came  out  not  only  with  the  right  numerical  value  but  also 
in  the  correct  direction. 

Einstein's  theory  of  General  Relativity  predicted  that  a  gravitational  field  would  bend 
or  deflect  the  path  of  light  rays.  For  a  light  ray  glancing  the  Sun,  the  theory  of  General 
Relativity  predicted  a  deflection  of  1.7  seconds  of  arc,  about  1/1,000  of  the  angular  width 
of  the  Sun  as  seen  from  the  Earth.  The  theory  of  General  Relativity  also  predicted  that  the 
gravitational  field  would  cause  the  speed  of  a  light  wave  to  slow. 

Three  types  of  experimental  tests  conducted  over  several  decades  confirmed  the  pre- 
cession of  Mercury's  perihelion,  the  deflection  of  light  rays  in  a  strong  gravitational  field, 
and  the  red  shift.  Consequently,  Irwin  Shapiro  called  his  the  Fourth  Test  of  General 
Relativity.  Initially,  Shapiro  was  interested  in  using  radar  to  confirm  the  precession  of 
Mercury's  perihelion.  He  hit  upon  that  idea  in  1959,  but  Shapiro  was  not  sure  whether  a 
check  on  a  widely  accepted  physical  theory  would  be  a  worthwhile  experiment.  So  in  April 
1960,  he  asked  a  visiting  French  physicist,  Cyrano  de  Dominicis,  about  the  experiment. 


29.  Hine  12  March  1993;  Log  books,  Haystack  Planetary  Radar,  HR-70-1,  9  December  1970  to  1 1  August 
1971;  HR-71-1,  16  August  1971  to  14  April  1972;  HR-73-1,  27  June  1973  to  26  November  1973;  and  HR-73-2,  9 
December  1970  to  11  August  1971,  SEBRING.  There  is  a  lacuna  in  the  log  book  records;  observations  made  after 
14  April  1972  and  before  27  June  1973  are  not  represented. 

30.  Ash,  Shapiro,  and  Smith,  "Astronomical  Constants  and  Planetary  Ephemerides  Deduced  from 
Radar  and  Optical  Observations,"  The  Astronomical  Journal  72  (1967):  338. 

31.  The  section  on  Einstein's  general  theory  of  relatively  draws  loosely  from  Banesh  Hoffmann, 
Relativity  and  its  Roots  (New  York:  W.  H.  Freeman  and  Company,  1983);  Peter  G.  Bergmann,  The  Riddle  of 
Gravitation,  revised  and  updated  (New  York:  Charles  Scribner's  Sons,  1987);  and  Mendel  Sachs,  Relativity  in  Our 
Time:  From  Physics  to  Human  Relations  (Bristol,  PA:  Taylor  and  Francis,  1993) .  See  also  Klaus  Hentschel,  "Einstein's 
Attitude  towards  Experiments:  Testing  Relativity  Theory,  1907-1927,"  Studies  in  History  and  Philosophy  of  Science  23 
(1992):  593-624. 


NORMAL  SCIENCE  127 


Dominicis  told  Shapiro  he  thought  the  experiment  worth  doing,  because  scientists  had  so 
few  tests  of  relativity.32 

No  radar  at  the  time,  however,  had  the  necessary  sensitivity  to  carry  out  the  preces- 
sion experiment.  At  any  rate,  the  Fourth  Test  was  not  to  measure  the  precession  of 
Mercury's  perihelion,  but  the  slowing  down  of  light  waves  caused  by  solar  gravity.  The  new 
idea  came  to  Shapiro  in  the  spring  of  1961,  as  he  was  attending  a  briefing  for  the  military 
on  some  of  the  research  conducted  at  Lincoln  Laboratory  and  MIT  with  Department  of 
Defense  funds.  After  his  lecture  on  measuring  the  speed  of  light,  George  Stroke,  in  a  con- 
versation with  Shapiro,  mentioned  that  the  speed  of  light  is  not  the  same  everywhere,  but 
depends  on  the  gravitational  field  through  which  it  is  passing.  Shapiro  was  surprised.  He 
refreshed  his  memory  on  General  Relativity  and  realized  that  there  was  a  misunderstand- 
ing: according  to  General  Relativity,  a  (freely)  falling  observer  would  measure  at  any 
location  the  same  speed  of  light,  independent  of  the  (local)  gravitational  field.  However, 
Shapiro  reasoned,  the  effect  of  the  gravitational  field  on  the  speed  of  light  would  be 
cumulative  over  a  round-trip  path  (unlike  the  red  shift)  and  that  a  radar  experiment, 
therefore,  ought  to  be  able  to  detect  this  gravitational  time  delay. 

Shapiro  now  had  the  idea  of  testing  the  gravitational  time  delay  predicted  by  General 
Relativity,  but  he  realized  that  extant  radars  could  not  measure  this  small  relativistic  effect. 
Moreover,  Shapiro  did  not  write  up  the  idea  at  that  time.  "I  just  kept  it  in  the  back  of  my 
mind,"  he  explained.33 

The  inauguration  of  the  Arecibo  Ionospheric  Observatory  in  November  1963 
revived  Shapiro's  interest  in  testing  General  Relativity.  In  July  1964,  Shapiro  and  his  wife, 
pregnant  with  their  first  child,  travelled  to  Arecibo  at  Gordon  Pettengill's  invitation  to 
spend  the  summer  working  at  the  AIO.  When  Charles  Townes,  then  MIT  Provost,  visited 
Arecibo  that  summer,  Shapiro  briefed  him  on  his  proposed  relativity  test  and  told  him 
that  Arecibo  could  not  perform  the  test.  "We  would  never  be  able  to  see  this  effect," 
Shapiro  explained.  "The  plasma  effect  of  the  solar  corona  would  be  of  the  same  general 
type,  and  the  variations  would  be  much  larger  than  the  relativistic  effect  we  were  looking 
for.  We  would  never  be  able  to  pick  it  out."34 

Shapiro  then  returned  home  and  learned  that  Haystack  was  to  be  dedicated  in 
October  1964.  Suddenly  it  occurred  to  Shapiro  that  Haystack  might  have  enough  capa- 
bility to  do  the  experiment.  He  did  some  quick  back-of-the-envelope  calculations  and  con- 
cluded that  Haystack  might  be  able  to  do  the  experiment.  Shapiro  sent  his  manuscript  to 
Physical  Review  Letters,  and  the  journal  received  it  on  13  November  1964.35 

From  his  realization  that  Haystack  could  do  the  experiment  to  his  submission  of  the 
paper  took  only  one  week.  After  doing  the  calculations  more  accurately,  Shapiro  realized 
that  the  sensitivity  of  the  Haystack  radar  was  not  good  enough  to  detect  the  relativistic 
effect.  He  and  his  Group  Leader  then  requested  an  upgrade  of  the  Haystack  radar  from 
the  head  of  Lincoln  Laboratory,  Bill  Radford,  who  subsequently  obtained  a  funding 


32.  Shapiro's  recounting  of  the  conception  of  the  Fourth  Test  is  included  here,  because  the  three- 
decade-long  feud  that  resulted  from  it  has  become  a  part  of  the  lore  of  radar  astronomy.  The  sources  for 
Shapiro's  and  Muhleman's  versions  of  the  story  are  oral  histories  conducted  specifically  for  this  history,  namely 
Shapiro  1  October  1993  and  Muhleman  19  May  1994.  Paul  Reichley,  in  a  telephone  conversation  of  19  May  1994, 
refused  any  other  comment  than  to  state  that  he  agreed  with  whatever  Muhleman  said. 

33.  Shapiro  1  October  1993. 

34.  Shapiro  1  October  1993. 

35.  Shapiro,  "Fourth  Test  of  General  Relativity,"  Physical  Review  Letters  13  (28  December  1964):  789. 
Although  little  noted  at  the  time,  Shapiro  in  his  1964  paper  also  pointed  out  that  a  possible  change  with 

atomic  time  of  Newton's  universal  gravitational  constant  could  be  tested  with  radar  observations  of  Mercury. 
Such  a  change  was  predicted  by  Paul  Adrien  Maurice  Dirac  in  1937  in  his  "large  numbers  hypothesis."  Evidence 
for  such  a  change  is  being  actively  sought  still  from  monitoring  orbits,  as  Shapiro  suggested,  because  any  such 
change  would  have  profound  effects  on  the  evolution  of  the  universe  and  the  formation  of  structure  within  it. 


1 28  TO  SEE  THE  UNSEEN 


commitment  from  the  Rome  Air  Development  Center  for  the  upgrade.  The  upgrade 
consisted  of  design  and  construction  of  a  new  electronic  plug-in  unit,  boosting  the 
continuous-wave  transmitter  from  100  to  500  kilowatts,  and  replacement  of  the  cooled 
parametric  amplifier  with  a  lower  noise  maser.36 

In  January  1965,  as  the  design  and  construction  of  the  radar  upgrade  was  underway, 
a  colleague  showed  Shapiro  aJPL  internal  publication  dated  31  October  1964  in  which  an 
article  by  Duane  Muhleman  discussed  using  radar  to  measure  the  general  relativistic 
effect.37  Shapiro  was  upset.  He  recalled  vividly  that  in  January  1964,  he  was  walking  near 
Harvard  Square  with  Muhleman.  When  Muhleman  asked  him  why  he  was  still  interested 
in  radar  astronomy,  Shapiro  told  him  about  his  idea  to  test  this  new  effect  predicted  by 
General  Relativity.  Yet  Muhleman  did  not  acknowledge  that  conversation  in  his  JPL 
report.  Furthermore,  that  report  only  discussed  the  test  being  done  near  the  inferior  con- 
junction of  Venus,  where  such  a  test  was,  and  remains,  infeasible.  Shapiro  noted  that  sev- 
eral years  later,  he  approached  Muhleman 's  co-author  of  the  JPL  report,  Paul  Reichley, 
and  asked  him  how  he  got  involved  in  that  project.  To  Shapiro's  amazement,  Reichley 
responded  directly  that  Muhleman  had  said  to  him,  "Shapiro  says  there's  an  effect  here, 
let's  look  into  it." 

The  Muhleman  and  Shapiro  relativity  experiments  both  involved  using  radar  and 
finding  the  relativistic  time  delay,  but  the  design  of  their  experiments  differed  widely.  The 
Shapiro  Test  sent  radar  waves  from  Earth  to  graze  past  the  Sun  and  bounce  from  Mercury 
(or  Venus)  at  superior  conjunction,  that  is,  as  the  planet  was  just  going  behind  the  Sun 
(or  emerging  from  behind  the  Sun)  when  seen  from  Earth. 

The  radar  waves  then  returned  from  Mercury  (or  Venus)  and  again  passed  near  the 
Sun  on  their  return  trip  to  Earth.  The  Sun's  gravitational  field  would  slow  down  or  delay 
the  radar  waves.  General  Relativity  predicted  that  the  cumulative  time  delay  due  to  the 
direct  effect  of  the  Sun's  gravitational  field  might  be  somewhat  more  than  200  microsec- 
onds. On  the  other  hand,  this  time  delay  for  radar  waves  bounced  from,  say,  Venus  at  its 
inferior  conjunction  amounted  to  only  about  10  microseconds.38 

Muhleman 's  experiment  grew  out  of  his  theoretical  work  at  JPL  on  communications 
with  spacecraft  flying  near  the  Sun.  Spacecraft  navigation  was  at  that  time  essentially  a 
matter  of  measuring  Doppler  shift  to  a  high  degree  of  accuracy.  Because  JPL  also  was  con- 
sidering ranging  systems,  Muhleman  was  studying  the  effects  of  the  solar  corona  on  both 
Doppler  and  range  signals.  "While  working  on  that  problem,"  he  explained,  "I  realized 
that  the  main  effect  of  the  solar  corona  on  the  radio  signal  was  that  the  signal  was  bent  as 
it  went  around  the  Sun."  Muhleman  considered  the  solar  gravitational  field  as  though  it 
were  a  lens  with  an  index  of  refraction,  an  idea  he  later  discovered  in  various  relativity 
books.  On  a  practical  level,  the  Muhleman  and  Shapiro  relativity  studies  differed  widely. 
Whereas  Shapiro  intended  to  bounce  radar  waves  off  Mercury  (or  Venus)  at  superior  con- 
junction, Muhleman  proposed  measuring  at  inferior  conjunction,  when  the  relativistic 
effect  would  not  be  detectable.39 


36.  C.  Robert  Wieser  to  Gen.  B.  A.  Schriever,  31  May  1966,  13/56/AC  1 18,  MITA. 

37.  See  Shapiro,  "Fourth  Test,"  pp.  789-791;  Muhleman  and  Reichley,  "Effects  of  General  Relativity  on 
Planetary  Radar  Distance  Measurements,"  in  Supporting  Research  and  Advanced  Development,  Space  Programs 
Summary  37-29  (Pasadena:  JPL,  31  October  1964),  pp.  239-241.  Although  Muhleman's  note  had  an  earlier  pub- 
lication date,  it  was  in  an  internal  report  with  a  tightly  limited  distribution,  whereas  Shapiro  published  in  a  wide- 
ly distributed  scientific  journal.  Paul  Reichley,  Muhleman's  co-author,  was  a  young  college  graduate  recently 
hired  at  JPL  and  worked  with  Muhleman  on  occultation  studies  of  radio  signals.  Reichley,  telephone  conversa- 
tion, 19  May  1994;  and  Muhleman  19  May  1994. 

38.  Shapiro,  Effects  of  General  Relativity  on  Interplanetary  Time-Delay  Measurements,  Technical  Report  368 
(Lexington:  Lincoln  Laboratory,  18  December  1964),  pp.  1-2;  and  Shapiro,  Testing  General  Relativity  with 
Radar,"  Physical  Review  145  (1966):  1005-1010. 

39.  Muhleman  19  May  1994;  Shapiro  1  October  1993;  Shapiro,  Effects  of  General  Relativity,  p.  2. 


NORMAL  SCIENCE  129 


The  judgement  of  general  texts  is  that  Irwin  Shapiro  originated  the  Fourth  Test.40 
Muhleman,  for  a  number  of  reasons,  dropped  out  of  radar  astronomy  for  over  twenty 
years.  Shapiro  and  his  Lincoln  Laboratory  coworkers  eventually  did  perform  the  Fourth 
Test  at  Haystack  during  the  superior  conjunction  of  Mercury  in  November  1966.  Haystack 
made  subsequent  measurements  during  the  superior  conjunctions  of  18  January,  11  May, 
and  24  August  1967.  The  results  confirmed  General  Relativity  to  an  accuracy  of  about  ten 
percent.41 

Additional  observations  of  Mercury  and  Venus  made  at  both  Haystack  and  Arecibo 
during  several  superior  conjunctions  helped  to  refine  the  Fourth  Test  results.  Subsequent 
experiments  carried  out  on  spacecraft  further  improved  the  accuracy  of  the  test.  The  best 
accuracy  yet  achieved  was  from  a  combined  MIT  and  JPL  experiment  on  the  Viking  mis- 
sion to  Mars;  it  confirmed  Einstein's  theory  of  General  Relativity  to  a  tenth  of  a  percent. 
The  accuracy  of  the  measurement  of  the  relativistic  effect  had  improved  by  an  impressive 
factor  of  100,  or  two  orders  of  magnitude,  in  10  years.42 

A  Shifting  Paradigm 

The  planetary  radar  research  discussed  up  to  this  point  shared  a  consensus  on  prob- 
lem-solving activities  in  a  way  typical  of  a  Kuhnian  paradigmatic  science.  Among  the  forces 
driving  the  evolution  of  planetary  radar  astronomy  was  the  interaction  between  the  two 
kinds  of  problems  radar  astronomers  attempted  to  solve.  One  set  related  to  the  larger  the- 
oretical framework  which  the  results  of  radar  observations  and  analysis  attempt  to  address; 
the  other  related  to  epistemological  questions  and  included  radar  techniques.  Because 
the  two  problem  sets  are  necessarily  linked  to  one  another,  the  invention  or  adaptation  of 
new  radar  techniques  impacted  on  the  kinds  of  scientific  problems  addressed  by  radar 
astronomy  and,  as  a  result,  expanded  the  paradigm  without  altering  the  original  problem- 
solving  activities  and  techniques. 

One  of  the  most  powerful  new  radar  techniques  was  planetary  range-Doppler  map- 
ping. It  added  a  whole  gamut  of  answers  that  radar  astronomy  previously  could  not 
provide.  The  successful  application  of  the  new  technique  depended  on  the  availability  of 
a  generation  of  highly  sensitive  radars,  Haystack,  Arecibo,  and  DSS-14.  Technology  con- 
tinued to  drive  radar  astronomy.  Because  the  kinds  of  problems  range-Doppler  mapping 
solved  were  related  more  to  geology  than  to  astronomy,  planetary  radar  grew  close  to  the 
theoretical  framework  of  planetary  geology.  This  shift  of  the  paradigm  (without  alteration 
of  the  original  astronomy-oriented  paradigm)  also  reflected  the  evolving  social  context  of 
planetary  radar,  which  in  1970  found  itself  a  patron  in  NASA  and  its  missions  of  planetary 
exploration.  Thus,  changing  problem  sets  and  theoretical  frameworks  on  the  one  hand 
and  the  evolution  of  financial  and  institutional  patronage  on  the  other  became  inextrica- 
bly linked. 

Planetary  Range-Doppler  Mapping 

Both  range  and  Doppler  were  standard  radar  measurements  long  before  they 
united  to  provide  range-Doppler  maps  of  planetary  surfaces.  Range  or  time-delay 


40.  See,  for  example,  Peter  G.  Bergmann,  The  Riddle  of  Gravitation,  rev.  ed.  (New  York:  Charles  Scribner's 
Sons,  1987),  p.  158. 

41.  Shapiro  1  October  1993;  Shapiro,  Pettengill,  Ash,  Stone,  Smith,  Ingalls,  and  Brockelman,  "Fourth 
Test  of  General  Relativity:  Preliminary  Results,"  Physical  Review  Letters  20  (1968):  1265-1269. 

42.  Shapiro  1  October  1993. 


1 30  TO  SEE  THE  UNSEEN 


measurements  determine  how  far  away  a  target  is  by  the  amount  of  time  the  echo  takes  to 
return  to  the  radar  receiver.  The  greater  the  distance  to  the  target,  the  longer  the  echo 
takes  to  appear  in  the  receiver.  Conversely,  the  shorter  the  distance  to  the  target,  the  less 
time  the  echo  takes  to  appear  in  the  receiver.  Knowing  that  radar  waves  travel  at  the  speed 
of  light,  one  can  calculate  the  distance  traveled  by  a  radar  signal  from  the  amount  of  time 
between  transmission  of  a  radar  signal  and  reception  of  its  echo. 

If  one  assumes  that  a  planetary  target  is  a  perfect  sphere,  then  when  a  transmitter 
directs  radar  waves  at  it,  the  waves  arrive  first  at  a  circular  area  at  the  center  of  the  planet 
as  viewed  from  Earth.  The  point  on  the  planet's  surface  that  has  the  radar  at  its  zenith, 
and  is  thus  closest  to  the  observer,  is  called  the  subradar  point.  Thus,  the  radar  waves  first 
hit  a  circular  area  on  the  planet  surrounding  the  subradar  point  and  form  what  is  called 
a  range  ring.  Within  each  range  ring,  the  distance  from  Earth  to  the  planet's  surface,  that 
is,  the  range  or  delay  in  time,  is  the  same.  The  longest  delays  (and  therefore  ranges)  gen- 
erally correspond  to  echoes  from  near  the  planetary  limbs. 

When  a  radar  transmits,  it  sends  a  signal  that  contains  only  a  very  narrow  band  of  fre- 
quencies and  appears  almost  line-like.  Such  would  be  the  case,  too,  for  the  echo  received 
back  at  the  radar  were  there  no  difference  in  the  relative  motion  between  the  radar  and 
its  target.  In  reality,  when  looking  from  the  Earth  at  a  planetary  target,  this  relative  motion 
is  always  a  factor.  The  combined  motions  of  the  Earth  as  it  spins  on  its  axis  and  orbits 
around  the  Sun,  and  of  the  planetary  target  as  it  also  spins  on  its  axis  and  orbits  about  the 
Sun,  cause  what  is  known  as  the  Doppler  effect  or  Doppler  shift,  which  is  the  difference 
between  the  frequencies  of  the  radar  transmission  and  the  radar  echo.  The  differences  in 
the  relative  motions  of  the  radar  and  the  target  broaden  the  frequency  of  the  returning 
signal.  Instead  of  a  (nearly)  single  frequency,  the  returning  signal  exhibits  a  spectrum  of 
frequencies  "shifted"  or  set  off  from  the  transmitted  frequency. 

In  order  to  remove  the  Doppler  shift  caused  by  the  relative  motion  of  the  observer 
and  the  target,  planetary  radar  astronomers  generally  use  a  radar  ephemeris  program. 
The  program  automatically  adjusts  the  incoming  signal  for  the  expected  Doppler  shift, 
which  itself  changes  over  time  because  of  the  changes  in  relative  motion  of  the  observer 
and  the  target.  Thus,  the  predicted  Doppler  shift  must  be  accurate  enough  to  avoid 
smearing  out  the  echo  in  frequency.  This  requirement  places  stringent  demands  on  the 
quality  of  the  observing  ephemeris.  Thus,  the  Lincoln  Laboratory  PEP  and  the  JPL 
Development  Ephemeris  series  were  of  vital  importance  to  the  successful  execution  of 
planetary  range-Doppler  mapping. 

A  given  portion  of  the  echo  frequency  spectrum  corresponds  to  a  slice  or  strip  on 
the  planet's  surface.  Each  slice  is  parallel  to  the  plane  containing  the  line  from  the  observ- 
er to  the  planet  and  the  spin  axis  of  the  planet,  and  each  slice  has  the  same  Doppler  shift 
value,  because  each  portion  of  that  slice  of  the  planet's  surface  has  the  same  motion  rela- 
tive to  the  observer.  When  Doppler  shift  and  range  data  are  combined,  the  slices  of  equal 
Doppler  shift  intersect  the  range  rings  to  form  "cells."  In  general,  each  range-frequency 
cell  corresponds  to  two  particular  areas  on  the  planet's  surface.  The  amount  of  surface 
area  corresponding  to  a  particular  range-frequency  cell  represents  the  resolution  of  the 
radar  image  on  the  planet's  surface  and  varies  over  the  planetary  surface  (see  Technical 
Essay,  Figure  42). 

The  amount  of  power  returned  from  the  target  for  each  range-frequency  cell  can  be 
converted  into  a  twoniimensional  image  of  the  planetary  surface  through  a  series  of  com- 
plex mathematical  manipulations.  Each  spectrum  has  the  attributes  of  power,  bandwidth 
(the  maximum  spread  of  line-of-sight  velocities) ,  shape,  minor  features,  and  a  weak  broad- 
band component.  The  total  power  received  depends  on  such  instrument  factors  as  trans- 
mitter power,  antenna  gain,  and  pointing  accuracy,  as  well  as  on  the  reflecting  (backseat- 


NORMAL  SCIENCE  131 


tering)  properties  of  the  target  and  the  so-called  radar  equation.  The  radar  equation 
states  that  the  amount  of  power  in  an  echo  is  inversely  proportional  to  the  fourth  power 
of  the  distance.  That  means  that  the  echo  power  received  by  a  radar  decreases  sharply  with 
increasing  distance  of  the  target.  For  instance,  a  radar  echo  is  I/ 16th  as  strong  if  the  dis- 
tance to  the  target  is  doubled,  all  other  conditions  being  equal. 

In  general,  rough  planetary  surfaces  backscatter  more  power  from  near  the  planet's 
limbs  than  a  corresponding  smooth  sphere.  Thus,  a  rough  surface  leads  to  a  broadening 
of  the  frequency  spectrum  of  the  planetary  echo.  A  smooth  planetary  surface  (relative  to 
the  size  of  the  wavelength  of  the  radar  waves)  would  broaden  the  return  signal  to  a  far  less- 
er degree.  The  amount  of  power  returned  to  the  receiver  in  each  resolution  cell  therefore 
corresponds  to  the  planet's  surface  characteristics. 

The  idea  of  combining  range  and  Doppler  data  to  form  a  radar  image  came 
together  at  Lincoln  Laboratory  in  the  late  1950s.  There,  Paul  Green  began  to  consider  the 
calculation  of  a  planet's  spin  velocity  from  a  simultaneous  measure  of  range  and  Doppler 
spread.  Another  member  of  the  Lincoln  Laboratory  radar  group,  Roger  Manasse,  point- 
ed out  that  when  you  look  at  a  spinning  object,  the  planes  of  equal  Doppler  shift  are 
parallel  to  the  plane  containing  the  line  of  sight  and  the  rotation  vector.43  However, 
Manasse  did  not  put  the  slices  of  Doppler  shift  together  with  the  range  rings.  The  origi- 
nator of  that  idea  was  Paul  Green. 

Green  remembers  how  the  idea  came  to  him:  "I  was  sitting  in  my  living  room  won- 
dering what  the  relationship  was  between  the  two  of  them.  I  also  had  noticed  that  Ben 
Yaplee  had  actually  measured  those  things."44  Ben  Yaplee  and  others  at  the  Naval 
Research  Laboratory  were  using  range  rings  to  refine  the  Earth-Moon  distance.  They  dis- 
covered that  details  in  the  structure  of  the  return  echoes  could  be  correlated  with  lunar 
topography.45 

However,  they  did  not  develop  planetary  radar  range-Doppler  imaging.  "It  was  sim- 
ply an  unevaluated  measurement,"  Green  explained.  'There  was  no  attempt  to  know  what 
deeper  message  might  be  behind  that.  I  was  just  thinking,  'Hey!  Wait  a  minute!  That's 
kind  of  an  interesting  thing  to  do.'  Maybe  it  was  obvious,  but  might  there  not  be  some- 
thing deep  behind  it?"46 

Soon  after  formulating  range-Doppler  mapping,  Green  discovered  that  classified 
military  radar  research  at  the  University  of  Michigan  had  led  to  the  conception  of  a  simi- 
lar process  but  with  significant  differences.  The  military  process  involved  imaging  the 
Earth  from  aircraft  and  relied  on  developing  a  radar  "history"  of  the  target  to  create  an 
image,  while  planetary  range-Doppler  mapping  created  a  "snapshot"  of  a  planetary  sur- 
face from  a  ground-based  radar.  Because  of  the  similarities  in  the  two  methods,  Green  was 
careful  to  call  his  planetary  range-Doppler  mapping.  The  University  of  Michigan  radar 
effort,  as  we  shall  see  in  the  next  chapter,  eventually  had  a  profound  impact  on  planetary 
radar  astronomy. 

Paul  Green  first  presented  his  ideas  on  range-Doppler  mapping  at  the  pioneering 
Endicott  House  Conference  on  Radar  Astronomy,  then  at  the  URSI  workshop  on  radar 
astronomy  that  followed  immediately  afterward  in  San  Diego.  An  abstracted  form  of  that 
paper  and  the  others  presented  at  the  workshop  soon  appeared  in  the  Journal  of 
Geophysical  Research.47 


43.  Roger  Manasse,  The  Use  of  Radar  Interferometer  Measurements  to  Study  Planets,  Group  Report  312-23 
(Lexington:  Lincoln  Laboratory,  March  1957). 

44.  Green  20  September  1993. 

45.  See  Ch.  1,  note  69,  and  Ch.  3,  note  14. 

46.  Green  20  September  1993. 

47.  Green  20  September  1993;  Leadabrand,  "Radar  Astronomy  Symposium  Report,"  pp.  1111-1115. 
Earlier,  a  more  complete  exposition  of  the  theory  appeared  as  Green,  A  Summary  of  Detection  Theory  Notions  in 
Radar  Astronomy  Terms,  Group  Report  34-84  (Lexington:  Lincoln  Laboratory,  ISJanuary  1960).  See,  also,  Ch.  3, 
note  22. 


132 


TO  SEE  THE  UNSEEN 


Green  did  not  apply  his  theory  to  actual  radar  mapping  of  the  planets.  Instead,  it  was 
his  Lincoln  Laboratory  colleague  Gordon  Pettengill  who  used  it  beginning  in  1960. 
Initially,  Pettengill  explored  the  surface  of  the  Moon  with  the  Millstone  radar.  The  result 
was  an  image  that  barely  resembled  the  lunar  surface.  Pettengill  concluded,  "It  is  obvious 
that  much  patient  work  lies  ahead  before  detailed  correlation  with  optical  photographs 
may  be  attempted."48 


Figure  16 

The  first  range-Doppler  image  of  the  Moon,  7  January  1960,  made  by  Gordon  PettengiU,  using  techniques  developed  by  his 
Lincoln  Laboratory  colleague  Paul  Green.  The  top  of  the  image  (shown  in  range  box  2)  represents  the  point  on  the  lunar  sur- 
face closest  to  the  radar.  Pettengill,  as  the  first  associate  director  of  the  Arecibo  Ionospheric  Observatory,  as  it  was  then  called, 
later  guided  range-Doppler  imaging  of  the  Moon  and  planets  at  Arecibo  as  well  as  at  the  Haystack  Observatory.  (Courtesy  of 
MIT  Lincoln  Laboratory,  Lexington,  Massachusetts,  photo  no.  261209-1D.) 


48.      Pettengill,  "Measurements  of  Lunar  Reflectivity  Using  the  Millstone  Radar,"  Proceedings  of  the  IRE  48 
(May  1960):  933-934. 


NORMAL  SCIENCE  133 


Lunar  Radar  Mapping 


Pettengill  made  a  second  attempt  at  lunar  radar  mapping  in  June  1961,  again  using 
the  Millstone  radar.  Those  and  the  previous  Pettengill  radar  images  had  what  radar 
astronomers  call  north-south  ambiguity.  The  nature  of  range-Doppler  mapping  is  to  cre- 
ate an  uncertainty  (called  north-south  ambiguity),  such  that  the  observer  does  not  know 
from  which  hemisphere  the  echoes  are  returning.  The  range-Doppler  technique  creates 
two  points,  one  in  the  northern  hemisphere  and  the  other  in  the  southern  hemisphere, 
with  exactly  the  same  range  and  Doppler  values.  The  radar  data  cannot  distinguish  the 
hemisphere  of  origin  of  the  return  echo  and  thus  presents  a  confusing  picture  of  the  tar- 
get's features. 

Pettengill  had  no  technique  yet  for  distinguishing  northern-hemisphere  echoes 
from  southern-hemisphere  echoes.  He  knew  that  the  youngest,  and  therefore  the  rough- 
est, large  feature  on  the  lunar  surface  visible  from  Earth  was  the  crater  Tycho.  During  a 
full  Moon,  this  crater  appears  to  have  rays  emanating  across  the  lunar  surface.  When 
Pettengill  looked  at  the  echo  spectra,  he  found  anomalously  high  spikes  that  were  consis- 
tent from  run  to  run.  He  assumed  that  they  were  in  the  southern  hemisphere  (the  loca- 
tion of  Tycho)  and  found  they  matched  the  crater's  location.49 

For  the  first  time,  a  lunar  surface  feature  and  a  radar  return  had  matched.  However, 
the  north-south  ambiguity  problem  stood  in  the  way  of  refining  range-Doppler  mapping 
into  a  useful  tool  for  exploring  the  solar  system.  One  solution  appeared  when  the  Arecibo 
Ionospheric  Observatory  began  operation  in  November  1963.  There,  at  the  instigation  of 
Pettengill,  who  was  now  Associate  Director  of  Arecibo,  Thomas  W.  Thompson,  then  a 
Cornell  graduate  student,  and  Rolf  Dyce  began  range-Doppler  mapping  of  the  Moon. 

In  contrast  to  Millstone,  the  Arecibo  radar  antenna  had  a  narrow  beamwidth  relative 
to  the  angular  size  of  the  Moon.  The  Moon  has  a  diameter  of  a  half  degree  or  30  minutes 
of  arc.  The  width  of  the  Arecibo  antenna  beam  was  10  minutes.  Instead  of  aiming  the 
antenna  at  the  center  of  the  lunar  disk  facing  Earth,  Thompson  and  Dyce  aimed  it  at  a 
point  10  minutes  of  arc  south  from  the  center.  The  Arecibo  telescope  received  echoes, 
therefore,  only  from  the  lower  or  "southern"  part  of  the  Moon.  The  technique  assuaged 
the  problem  of  north-south  ambiguity,  but  was  applicable  to  only  the  Moon.  Venus  was 
only  a  speck,  slightly  more  than  one  minute  of  arc,  compared  to  the  Moon's  30  minutes 
of  arc.50 

Using  this  approach,  Thompson  and  Dyce  explored  eight  regions  of  the  lunar  sur- 
face and  collected  data  on  echo  strength.  They  converted  the  data  into  "contour"  lines  of 
relative  reflectivity.  Thompson  placed  these  lines,  computed  and  plotted  on  a  transparent 
overlay,  over  lunar  maps  made  from  photographs.  The  resultant  radar  contour  map  had 
a  resolution  of  20  by  30  km.51 

Thompson  continued  to  carry  out  range-Doppler  mapping  of  the  Moon  by  taking 
advantage  of  the  increasingly  narrow  beamwidth  of  the  Arecibo  antenna.  By  reducing  the 
beamwidth  from  10  to  7  minutes  of  arc,  he  succeeded  in  creating  a  range-Doppler  map  of 
the  crater  Tycho  with  surface  resolutions  between  7  and  10  km.  The  output  from  a  given 
radar  observation  now  represented  a  considerable  quantity  of  data;  between  10,000  (104) 
and  100,000  (105)  values  of  intensity  (or  pixels)  constituted  a  single  map. 


49.  Pettengill  and  John  C.  Henry,  "Enhancement  of  Radar  Reflectivity  Associated  with  the  Lunar  Crater 
Tycho,"  Journal  of  Geophysical  Research  67  (1962):  4881-4885.  Pettengill's  co-author  was  an  MIT  electrical  engi- 
neering graduate  student  who  used  the  experience  in  writing  his  master's  thesis.  Henry,  "An  Automated 
Procedure  for  the  Mapping  of  Extended  Radio  Sources,"  M.S.  thesis,  MIT,  1965. 

50.  Source  for  the  arc  measurement  of  Venus:  Goldstein,  "Radar  Studies  of  Venus,"  in  Audoin  Dollfus, 
ed.,  Moon  and  Planets  (Amsterdam:  North-Holland  Publishing  Company,  1967),  p.  127. 

51.  Thompson  29  November  1994;  Thompson  and  Dyce,  "Mapping  of  Lunar  Radar  Reflectivity  at  70 
Centimeters,"  Journal  of  Geophysical  Research  7 1  (1966):  4843-4853. 


134 


TO  SEE  THE  UNSEEN 


Figure  17 

Radar  map  of  the  lunar  crater  Tycho  with  a  resolution  of  I  kilometer  made  urith  the  3.8-cm  (7,750-MHz)  Haystack 
Observatory  radar.  The  grid  lines  are  spaced  about  17  km  apart.  (Courtesy  of  MIT  Lincoln  Laboratory,  Lexington, 
Massachusetts,  photo  no.  242336-1.) 

At  the  same  time,  Gordon  Pettengill  guided  lunar  radar  observations  at  Haystack, 
which  had  become  available  in  late  1964.  Haystack,  moreover,  had  a  narrower  antenna 
beamwidth,  only  3  minutes  of  arc,  and  the  higher  operating  frequency  of  Haystack  (3.8 
cm,  X-band)  compared  to  Arecibo  (70  cm,  UHF)  helped  Haystack  to  achieve  a  much  finer 
resolution  on  Tycho:  between  1  and  2  km.  The  Haystack  radar  images  now  approached 
the  quality  of  lunar  photographs  made  from  Earth.  In  the  words  of  Pettengill  and 


NORMAL  SCIENCE  135 


Thompson,  'The  most  immediately  striking  feature  of  the  3.8-cm  [Haystack]  observations 
is  their  resemblance  to  the  optical  photograph...."52 

The  coincidental  refinement  of  lunar  range-Doppler  imaging  and  the  commitment 
to  place  an  American  on  the  Moon  before  the  end  of  the  1960s  enhanced  the  value  of  the 
lunar  radar  work  done  at  both  Arecibo  and  Haystack.  NASA  Apollo  mission  staff  used  the 
radar  images  to  help  select  landing  sites,  and  Apollo  funded  Thompson's  dissertation  and 
subsequent  radar  studies  of  the  Moon.  Once  the  resolution  of  radar  images  surpassed  the 
resolution  of  lunar  photographs  made  from  Earth,  the  value  of  lunar  radar  studies  to 
NASA  grew  even  more.  Thus,  the  new  technique  brought  radar  astronomy  closer  to  the 
scientific  needs  of  NASA,  increasingly  the  patron  of  radar  astronomy. 

At  Arecibo,  Tommy  Thompson  and  Rolf  Dyce  undertook  radar  mapping  of  the 
Moon  at  both  40  MHz  (7.5  meters)  and  430  MHz  (70  cm)  under  a  supplementary  grant 
from  NASA.  A  joint  report  with  Lincoln  Laboratory  compared  the  Arecibo  results  with 
those  carried  out  at  Haystack  by  Stan  Zisk  with  additional  NASA  funding  under  a  contract 
between  MIT  and  the  Manned  Spacecraft  Center  in  Houston.  NASA  funded  lunar  studies 
at  both  telescopes  until  1972,  when  the  Apollo  program  came  to  an  end.53 


Venus  Radar  Mapping 


In  1964,  as  Thompson  and  Zisk  were  starting  their  lunar  mapping  activities,  Roland 
Carpenter  and  Dick  Goldstein  analyzed  spectra  from  Venus  and  discovered  the  first  fea- 
tures on  that  planet's  surface.  The  Goldstone  Venus  radar  lacked  sufficient  sensitivity  to 
apply  range-Doppler  mapping  to  Venus.  However,  once  the  Mars  Station  became  avail- 
able, Goldstein  continued  his  exploration  of  Cytherean  surface  features  using  range- 
Doppler  techniques,  but  without  resolving  the  north-south  ambiguity.  Thus  began  one  of 
the  most  long-lived  and  extensive  activities  of  planetary  radar  astronomers.  This  scientific 
niche  for  radar  resulted  from  that  planet's  opaque  atmosphere  which  barred  exploration 
with  optical  methods. 

When  Dick  Goldstein  observed  Venus  during  the  1964  inferior  conjunction,  he 
looked  only  at  the  structure  of  the  spectra  returned  from  the  planet.  This  was  the  same 
technique  that  Roland  Carpenter  had  used  earlier  to  discover  the  retrograde  motion  of 
Venus;  it  was  not  range-Doppler  mapping.  A  few  topographic  features  were  visible  as 
details  in  the  return  spectra.  Goldstein  found  two  features  represented  as  peaks.  They 
moved  slowly  across  the  spectrogram,  a  graph  plotting  echo  power  density  versus  fre- 
quency, from  the  high-frequency  side  to  the  low-frequency  side,  in  synchronization  with 
the  planet's  rotation. 

Goldstein  then  placed  his  two  features  on  a  coordinate  system  with  the  first  feature, 
named  Alpha  (a) ,  located  on  his  zero  degree  meridian  in  the  southern  hemisphere.  The 
second  feature,  named  Beta  ((3),  Goldstein  placed  in  the  northern  hemisphere.  His  coor- 
dinate system  was  somewhat  arbitrary  out  of  necessity,  as  astronomers  generally  had  not 
agreed  upon  any  Cytherean  coordinate  system.  Additional  analysis  of  the  1964  data 
revealed  three  more  features  around  the  equator.  Goldstein  named  them  Gamma  (i), 
Delta  (8),  and  Epsilon  (e). 


52.  Thompson  29  November  1994;  Pettengill  and  Thompson,  "A  Radar  Study  of  the  Lunar  Crater 
Tycho  at  3.8-cm  and  70-cm  Wavelengths,"  Icarus  8  (1968):  457-471,  esp.  464. 

53.  The  research  was  conducted  under  NASA  grant  NGR-33-010-024.  NEROC,  Semiannual  Report  of  the 
Haystack  Observatory,  15  July  1972,  p.  ii.  See,  also,  Ch.  4,  note  15. 


136 


TO  SEE  THE  UNSEEN 


Figure  18 

One  of  the  earliest  range-Doppler  images  of  Venus  made  by  Richard  Goldstein  ofJPL  with  the  Goldstone  radar.  The  notation 
"0°"  indicates  the  meridian  in  Goldstein 's  coordinate  system.  Visible  are  the  first  surface  features  identified  by  Goldstein:  Alpha 
(a),  on  the  meridian  in  the  southern  hemisphere,  Beta  (0),  in  the  far  west  of  the  northern  hemisphere,  and  Delta  (S),  just  to 
the  north  of  Beta.  Gamma  (T)  and  Epsilon  (E),  two  additional  features  identified  by  Goldstein,  are  not  labelled.  The  radar 
names  Alpha  and  Beta  were  retained  when  astronomers  began  naming  the  surf  ace  features  of  Venus.  (Courtesy  of  Jet  Propulsion 
Laboratory,  photo  no.  331-4849AA.) 


NORMAL  SCIENCE 


137 


Although  he  judged  that  these  features  were  probably  mountain  ranges,  Goldstein  had 
insufficient  evidence.  What  were  they?  "Venus  is  still  a  mystery  planet,"  Goldstein  con- 
cluded. "However,  it  may  no  longer  be  viewed  as  featureless,  but  rather  as  an  exciting 
object  for  further  study."54 

Using  the  data  taken  with  the  newly  operational  Mars  Station  during  the  1967  Venus 
inferior  conjunction,  Goldstein  studied  the  Beta  region  in  more  detail,  attempting  to 
determine  its  size  and  character,  rather  than  searching  for  new  features.  The  Mars  Station, 
moreover,  provided  sufficient  sensitivity  to  attempt  range-Doppler  mapping.  Goldstein 
observed  Beta,  Delta,  and  an  unnamed  region  at  (his)  40°  South  latitude  and  made  a 
crude  radar  image  of  the  6  region.  Still,  Goldstein  lacked  sufficient  data  to  determine 
whether  Beta  was  a  mountain  range  or  another  type  of  feature.55 


-40* 


-35°  -30° 

LONGITUDE 


-25' 


Figure  19 

A  detailed  radar  view  of  the  Beta  region  of  Venus,  1967,  made  by  Dick  Goldstein  ofJPL  using  the  Goldstone  radar.  It  exem- 
plifies the  limits  of  resolution  available  in  some  of  the  earliest  radar  images  of  that  planet.  (Courtesy  of  Jet  Propulsion 
laboratory,  photo  no.  P-8882.) 


54.  Goldstein,  "Preliminary  Venus  Radar  Results ,"  Journal  of  Research  of  the  National  Bureau  of  Standards, 
Section  D:  Radio  Science  69D  (1965) :  1623-1625;  Goldstein,  "Radar  Studies  of  Venus,"  in  Dollfus,  Moon  and  Planets, 
pp.  126-131.  This  article  also  appeared  as  Goldstein,  Radar  Studies  of  Venus,  Technical  Report  32-1081  (Pasadena: 
JPL,  1967). 

55.  Goldstein  and  Shalhav  Zohar,  "Venus  Map:  A  Detailed  Look  at  the  Feature  B,"  Nature  219  (1968): 
357-358;  Goldstein,  "A  Radar  View  of  the  Surface  of  Venus,"  Proceedings  of  the  American  Philosophical  Society  113 
(June  1969):  224-228.  Goldstein's  co-author,  Shalhav  Zohar,  was  a  fellow  JPL  employee  who  developed  much  of 
the  software  used  in  the  experiment. 


138 


TO  SEE  THE  UNSEEN 


Meanwhile,  Roland  Carpenter,  who  was  now  both  a  JPL  employee  and  an  instructor 
in  the  Department  of  Astronomy  of  the  University  of  California,  Los  Angeles,  had  ana- 
lyzed 1964  Venus  inferior  conjunction  radar  data.  Carpenter  found  two  distinct  peaks  in 
the  return  spectra  that  persisted  day  after  day  and  moved  slowly  with  time.  On  closer 
examination,  the  first  peak  appeared  to  have  three  components,  which  he  hesitated  to 
interpret  because  he  felt  their  nature  could  not  be  determined  with  the  available  data. 

Using  Goldstein's  coordinate  system,  Carpenter  began  to  identify  the  most  pro- 
nounced features  with  letters  of  the  alphabet  from  A  to  G.  He  labeled  less  probable  loca- 
tions as  numerical  extensions  of  nearby  features,  e.g.,  Bl,  Cl,  C2,  D2,  and  D3. 
Correlations  between  Carpenter's  and  Goldstein's  features  began  to  emerge.  Carpenter's 
feature  F  had  the  same  location  as  Goldstein's  a,  and  Carpenter's  group  B,  C,  and  D  cor- 
responded to  Goldstein's  |3  (Table  2).56 


Table  2 

Radar  Features  of  Venus 

Goldstein 

Carpenter 

Haystack 

Arecibo 

Alpha 

F 

Haystack  I 

Faraday 

Beta 

B 

Beta 

C 

Haystack  IV 

Beta 

D 

Beta 

Haystack  II 

Gauss 

Beta 

Haystack  III 

Hertz 

Gamma 

Delta 

D2 

Haystack  A 

(later  Haystack  VI) 

Epsilon 

A 

Bl 

Haystack  B 

Cl 

C2 

Haystack  V 

D3 

E 

G 

Haystack  C 

Haystack  D 

Maxwell 

Sources 

R.M.  Goldstein,  "Radar  Studies  of  Venus,"  in  Audoin  Dollfus,  ed.,  Moon  and  Planets  (Amsterdam:  North-Holland  Publishing 

Company,  1967),  pp.  126-131;  R.M.  Goldstein  and  H.C.  Rumsey.Jr.,  "A  Radar  Snapshot  of  Venus,"  Science  169  (1970):  974-977; 
R.L.  Carpenter,  "Study  ofVenus  by  CW  Radar:  1964  Results,"  The  Astronommljoumal  71  (1966):  142-152,  especially  pp.  148-151; 
A.E.E.  Rogers,  T.  Hagfors,  R.A.  Brockelman,  R.P.  Ingalls,  J.I.  Levine,  G.H.  Pettengill,  and  F.S.  Weinstein,  A  Radar  Interferometer 
Study  of  Venus  at  3.  8  cm,  Technical  Report  444  (Lexington:  Lincoln  Laboratory,  14  February  1968);  A.E.E.  Rogers,  R.P.  Ingalls, 
and  G.H.  Pettengill,  "Radar  Map  of  Venus  at  3.8  cm  Wavelength,"  /«znu21  (1974):  237-241;  D.B.  Campbell,  R.F.  Jurgens,  R.B. 
Dyce,  F.S.  Harris,  and  G.H.  Pettengill,  "Radar  Interferometric  Observations  of  Venus  at  70-Centimeter  Wavelength,"  Saence 

170  (1970):  1090-1092;  R.F.  Jurgens,  "Some  Preliminary  Results  of  the  70-cm  Radar  Studies  of  Venus,"  Radio  Sdence5  (1970): 
435-442-  and  R.F.  Jurgens,   A  Study  of  the  Average  and  Anamalous  Radar  Scattering  from  the  Surface  of  Venus  at  70  Cm 
Wavelength,"  PhD  diss.,  Cornell  University,  June  1968,  also  published  internally  as  CRSR  Research  Report  no.  297  (Ithaca: 

CRSR,  May  1968). 

Carpenter  dropped  out  of  radar  astronomy  and  pursued  a  teaching  career,  while 
Goldstein  continued  to  explore  Venus.  The  1969  inferior  conjunction  of  Venus  provided 
an  opportunity  to  use  range-Doppler  mapping.  Goldstein  combined  the  1969  data  with  ear- 
lier data,  then  applied  a  mathematical  method  devised  by  fellow  JPL  employee  Howard  C. 
Rumsey.Jr.,  which  involved  the  construction  of  a  large  matrix  of  range  and  Doppler  values. 

The  mapping  process  divided  the  surface  of  Venus  into  small  cells  1/2°  square  in  lat- 
itude and  longitude.  A  column  vector  (X)  consisted  of  the  unknown  reflectivities  of  these 
cells,  while  a  second  column  vector  (S)  contained  all  the  processed  data  from  17  days  of 


56.      Carpenter,  "Study  of  Venus  by  C\V  Radar:  1964  Results,"  The  Astronomical  Journal  71  ( 1966) :  142-152, 
especially  pp.  148-151. 


NORMAL  SCIENCE  139 


observations.  Already,  Goldstein  and  Rumsey  were  dealing  with  a  large  amount  of  data; 
vector  X  had  about  40,000  components,  vector  S  about  120,000  components.  They 
expressed  the  relationship  between  vectors  S  and  X  as  the  equation: 

AX  =  S, 

in  which  A  was  a  matrix  whose  components  could  be  computed  from  known  parameters 
and  the  motion  of  Venus  and  Earth.  Matrix  A  consisted  of  120,000  by  40,000  components. 

As  the  authors  wrote,  "Obviously,  we  cannot  compute  every  component  of  a  matrix 
with  over  109  entries."  The  matrix  was  "so  big,"  Goldstein  recalled,  "that  we  couldn't  even 
read  it  into  the  computer  except  one  line  at  a  time."57  Despite  the  difficulty  of  handling 
the  gargantuan  matrix,  Goldstein  produced  a  number  of  somewhat  unambiguous  images 
of  Venus.  Once  the  1969  data  had  been  converted  into  a  range-Doppler  map,  in  which 
each  resolution  cell  represented  an  area  on  the  planet's  surface,  Goldstein  made  cumu- 
lative maps  by  adding  earlier  data.  The  north  and  south  areas  of  the  cumulative  maps  were 
similar,  but  not  identical;  however,  the  images  suffered  serious  flaws,  including  the  "run- 
way" strip  running  more  or  less  along  the  planet's  equator.  Nonetheless,  Goldstein 
succeeded  in  resolving  a  for  the  first  time  on  a  map.  It  was  a  roundish  feature,  about 
1,000  km  across.58 

Goldstein  continued  to  map  Venus  with  Rumsey's  mathematical  approach,  adding 
data  taken  during  the  1970  inferior  conjunction  to  that  acquired  in  1969.  The  1970  data 
were  better,  being  less  noisy,  because  the  Deep  Space  Network  had  increased  the  trans- 
mitter power  of  the  Goldstone  Mars  Station  from  100  to  400  kilowatts.  The  total  system 
noise  temperature  stood  at  a  low  25  K.  Regions  a  and  B  remained  the  dominant  features 
of  the  JPL  radar  map.59 

Meanwhile,  at  Arecibo  and  Haystack,  radar  astronomers  were  creating  Venus  images 
with  their  own  techniques.  At  Arecibo,  Cornell  University  doctoral  student  Rayjurgens, 
with  support  from  an  NSF  Faculty  Fellowship,  undertook  the  analysis  of  radar  data  taken 
during  the  1964  inferior  conjunction.  Dyce  and  Pettengill  had  made  the  radar  observa- 
tions to  supply  the  Planetary  Ephemeris  Program  data  base,  not  to  make  a  range-Doppler 
map  of  Venus.60 

In  correlating  the  radar  data  with  the  Cytherean  surface,  Jurgens  abandoned  his  own 
zero  degree  meridian  in  favor  of  a  modified  version  of  Carpenter's  coordinate  system  that 
incorporated  the  latest  pole  position  and  rotation  rate  supplied  by  Irwin  Shapiro  from  the 
PEP.  Consequently,  Goldstein's  a  and  Carpenter's  F  were  not  at  the  zero  meridian  but 
closer  to  5°  longitude.  Jurgens  identified  the  features  he  found  by  latitude  and  longitude 
(e.g.,  20°,-102°,  in  which  "-"  indicated  South  latitude  or  West  longitude),  then  compared 
his  features  with  those  discovered  by  Goldstein  and  Carpenter. 

Jurgens  gave  particular  attention  to  Goldstein's  B  region  (Carpenter's  group  B,  C,  D, 
to  which  Jurgens  added  E),  and  he  managed  to  locate  most  of  Carpenter's  features.  In 
addition,  Jurgens  spotted  a  new  feature  near  Goldstein's  Beta.  Borrowing  from  Tommy 
Thompson's  lunar  radar  mapping  work,  Jurgens  interpreted  the  feature  as  a  ring  struc- 
ture, specifically  a  crater,  and  argued  that  such  a  crater  might  be  caused  by  meteoric 
impact.  Jurgens  admitted  that  "although  the  evidence  for  a  ring  structure  is  not  as  strong 
as  one  might  desire,  it  at  least  raises  the  question  of  whether  such  structures  would  be 
expected  on  Venus."61  Indeed,  it  was  one  of  the  first  attempts  to  relate  radar  observations 
and  geological  interpretation. 


57.  Goldstein  14  September  1993. 

58.  Goldstein  and  Rumsey,  "A  Radar  Snapshot  of  Venus,"  Science  169  (1970):  974-977. 

59.  Goldstein  and  Rumsey,  "A  Radar  Image  of  Venus,"  Icarus  17  (1972):  699-703. 

60.  Jurgens  23  May  1994. 

61.  Jurgens,  "A  Study  of  the  Average  and  Anomalous  Radar  Scattering,"  pp.  71  and  87-1 10. 


140 


TO  SEE  THE  UNSEEN 


Before  completing  his  dissertation,  Jurgens  observed  Venus  during  the  1967  inferior 
conjunction,  when  the  Arecibo  antenna  had  an  improved  receiver  system,  better  data 
acquisition  procedures,  and  a  lower  receiver  noise  temperature.  Jurgens  combined  the 
1967  data  with  additional  observations  made  during  the  subsequent  1969  conjunction.  In 
order  to  mitigate  the  north-south  ambiguity  problem,  he  compared  observations  made  a 
few  weeks  apart,  thereby  taking  advantage  of  the  changing  Doppler  geometries  between 
Earth  and  Venus. 

Jurgens  continued  to  explore  the  (3  region,  in  particular,  as  well  as  new  areas  of  the 
planet's  surface.  On  the  urging  of  Tommy  Gold,  he  named  his  features  after  scientists 
famous  for  their  work  in  electromagnetism:  Karl  Friedrich  Gauss  (1777-1855),  Heinrich 
Rudolph  Hertz  (1857-1894),  Michael  Faraday  (1791-1867),  and  James  Clerk  Maxwell 
(1831-1879).  Gauss  and  Hertz  both  corresponded  strongly  to  Goldstein's  |3  region. 
Faraday  was  Goldstein's  a.  However,  Maxwell,  discovered  during  the  1967  conjunction, 
had  no  match  among  previous  citings  of  Cytherean  surface  features.62  It  was  an  original 
and  enduring  contribution  to  Venus  mapping. 


Figure  20 

Ray  Jurgens  discovered  a  new  Venus  surface  feature,  named  Maxwell,  from  these  range-Doppler  images  made  at  the  Arecibo 
Observatory  on  4  September  1967  during  inferior  conjunction.  The  bright  spot  at  the  leading  edge  of  the  image  is  the  subradar 
point,  while  the  spot  closest  to  the  subradar  point  is  the  Beta  region.  Maxwell  is  the  spot  farther  from  the  planet's  leading  edge. 
(Courtesy  of  Ray  Jurgens.) 


62.     Jurgens,  "Some  Preliminary  Results  of  the  70-cm  Radar  Studies  of  Venus,"  Radio  Science  5  (1970): 
435-442;  AIO,  Research  in  Ionospheric  Physics,  Research  Report  RS  74  (Ithaca:  CRSR,  31  July  1968),  pp.  84-85. 


NORMAL  SCIENCE  141 


Investigators  at  Haystack  Observatory  also  observed  Venus  during  the  1967  conjunc- 
tion, but  they  used  a  unique  technique  they  pioneered  called  radar  interferometry.  It 
resolved  the  problem  of  north-south  ambiguity  in  a  superior  fashion.  An  optical 
interferometer  is  an  instrument  for  analyzing  the  light  spectrum  by  studying  patterns  of 
interference,  that  is,  how  lightwaves  interact  with  each  other.  Martin  Ryle  and  other  radio 
astronomers  had  been  designing  interferometers  since  the  late  1950s.  These  radio  inter- 
ferometers used  two  or  more  radio  telescopes  arranged  along  a  straight  line  (called  the 
base  line)  and  allowed  astronomers  to  "synthesize"  observations  at  higher  resolutions  than 
possible  with  a  single  antenna.63 

The  inventor  of  the  radar  interferometer  was  Alan  E.  E.  Rogers,  then  an  electrical 
engineering  graduate  student  at  MIT.  MIT  Prof.  Alan  H.  Barrett  was  recruiting  students 
to  participate  in  his  radio  astronomy  work  on  the  newly  discovered  OH  spectral  line.  Alan 
Rogers  joined  him  and  did  his  masters  and  doctoral  theses  on  the  OH  line.  As  part  of  his 
doctoral  thesis  research,  Rogers  helped  to  develop  a  radio  interferometer  that  linked  the 
Millstone  and  Haystack  radars. 

After  graduating  and  spending  a  year  home  in  Africa,  Rogers  returned  to  Lincoln 
Laboratory,  where  he  was  hired  to  work  in  the  radar  group  with  Gordon  Pettengill. 
Although  trained  as  a  radio  astronomer,  Rogers  rapidly  became  absorbed  in  planetary 
radar  work  and  proposed  a  radar  interferometer  to  eliminate  the  problem  of  north-south 
ambiguity  that  was  typical  of  range-Doppler  mapping.64  This  was  not  the  first  time  that  a 
radar  astronomy  technique  derived  from  radio  astronomy. 

The  X-band  (7,840  MHz;  3.8  cm)  radar  interferometer  linked  the  Haystack  and 
Project  Westford  antennas,  which  are  1 .2  km  apart,  in  the  so-called  Hayford  configuration. 
In  the  interferometry  experiments,  Haystack  transmitted  a  continuous-wave  signal  to 
Venus,  and  both  the  Haystack  and  Westford  antennas  received.  Technicians  working 
under  Dick  Ingalls  of  Haystack  reduced  and  analyzed  the  echoes  to  create  a  range- 
Doppler  map.  The  size  of  the  resolution  cell  on  the  planet's  surface  was  about  150  km 
square. 


63.  See  Bracewell,  "Early  Work  on  Imaging  Theory,"  pp.  167-190  and  Schcucr,  "Aperture  Synthesis  at 
Cambridge,"  pp.  249-265  in  Sullivan. 

64.  Rogers  5  May  1994. 


142 


TO  SEE  THE  UNSEEN 


Figure  21 

One  of  the  first  range-Doppler  images  of  Venus  made  with  a  radar  interferometer,  the  Haystack  and  Westford  antennas  in 
tandem,  in  1967.  Not  only  are  the  Alpha  and  Beta  regions  discernible,  but  the  complexity  of  Beta  is  revealed.  (Courtesy  of  Alan 
E.  E.  Rogers.) 

Next,  Rogers  and  Ingalls  combined  the  signals  from  the  two  antennas  to  obtain  the 
fringe  amplitude  and  phase  for  each  range-Doppler  cell.  In  an  elaborate  computer 
procedure,  they  rotated  the  fringe  pattern  so  that  the  lines  of  constant  phase  were  normal 
to  the  axis  of  apparent  rotation  of  the  planet.  The  lines  of  constant  phase  now  were 
perpendicular  to  the  slices  of  equal  Doppler  value.  Although  each  pair  of  resolution  cells 


NORMAL  SCIENCE  143 


that  exhibited  north-south  ambiguity  had  the  same  range  and  Doppler  shift  values,  one 
could  distinguish  the  north  and  south  cells  because  they  had  opposite  phases.65 

One  of  the  first  applications  of  this  radar  interferometer  was  to  the  lunar  work  being 
carried  out  at  Haystack  for  the  NASA  Manned  Spacecraft  Center  by  Stan  Zisk.  The  lunar 
topographic  maps  that  Zisk  created  with  the  Hayford  interferometer  were  carried  out 
under  the  name  "Operation  Haymoon"  until  December  1972,  when  the  Apollo  mission 
ended.66  Tommy  Thompson  carried  out  a  similar  interferometric  study  of  the  Moon  using 
the  40-MHz  (7.5-meter)  radar  at  Arecibo. 

Alan  Rogers  and  Dick  Ingalls  also  studied  Venus  during  the  1967  inferior  conjunc- 
tion with  the  Hayford  interferometer  and  identified  eight  surface  regions.  Just  as  each 
previous  radar  astronomer  had  invented  his  own  nomenclature,  they  labeled  features  with 
Roman  numerals  and  letters.  The  features  of  which  they  were  certain  became  Haystack  I 
through  Haystack  IV.  The  probable  regions  were  Haystack  A  through  Haystack  D.  Five  of 
these  eight  regions  corresponded  to  features  already  observed  by  either  Goldstein  or 
Carpenter.  Haystack  I  appeared  to  be  Goldstein's  a  and  Carpenter's  F,  while  Haystack  II 
matched  Goldstein's  6  (Table  2).  Jurgens'  Arecibo  results  had  not  yet  been  published.67 

Alan  Rogers  and  Dick  Ingalls  then  published  a  map  of  Venus  showing  the  correlation 
of  Haystack  and  JPL  features  in  a  1969  issue  of  Science.™  The  B  region  now  appeared  to  be 
large  and  complex.  The  Hayford  radar  interferometer  confirmed  and  extended  the 
observations  of  Goldstein  and  Carpenter.  With  interferometer  data  taken  during  the  1969 
and  1972  conjunctions  using  an  instrument  with  a  lower  system  noise  temperature,  Alan 
Rogers  and  Dick  Ingalls  refined  their  map  of  Venus;  the  data  continued  to  indicate  agree- 
ment among  the  Haystack  and  JPL  features.69 

The  waxing  tide  of  links  between  Lincoln  Laboratory  and  Arecibo  set  in  motion  by 
the  appointment  of  Gordon  Pettengill  as  associate  director  of  Arecibo  facilitated  the  trans- 
planting of  radar  interferometry  to  Arecibo.  In  fact,  investigators  at  Arecibo  built  two 
additional  antennas  to  study  the  Moon  and  Venus  with  the  new  technique.  The  lunar 
interferometer  used  the  40-MHz  antenna,  while  the  planetary  radar  interferometer  used 
the  430-MHz  antenna.  NASA  continued  to  underwrite  Tommy  Thompson's  lunar  radar 
work  through  a  supplementary  grant.70 


65.  For  a  description  of  the  radar  interferometer,  see  Rogers,  Hagfors,  Brockelman,  Ingalls,  Levine, 
Pettengill,  and  Weinstein,  A  Radar  Interferometer  Study  of  Venus  at  3.8  cm,  Technical  Report  444  (Lexington: 
Lincoln  Laboratory,  14  February  1968). 

66.  Rogers    5    May    1994;    Documents    in    44/2/AC    135;    "Haystack    Operations    Summary, 
8/11/69-5/18/70,"  37/2/AC   135;   "Funding  Proposal,   "Programs  in  Radio  Astronomy  at  the  Haystack 
Observatory,"  NSF,   10/1/72-9/30/73,"  28/2/AC   135,  MITA;  NEROC,   Semiannual  Report  of  the  Haystack 
Observatory,  15  July  1972,  p.  ii;  NEROC,  Final  Progress  Report  Radar  Studies  of  the  Planets,  29  August  1974,  p.  1.  A 
number  of  techniques  for  extracting  lunar  topography  from  interferometric  data  were  devised.  Delay-Doppler 
stereoscopy  was  developed  by  Irwin  Shapiro  and  independendy  by  Thomas  Thompson  and  Stan  Zisk.  Anodier 
technique,  called  delay-Doppler  interferometry,  was  suggested  by  Shapiro  and  developed  by  Zisk  and  Rogers; 
Thompson  pointed  out  the  strength  of  the  Hayford  interferometer  for  this  application.  Shapiro,  Zisk,  Rogers, 
Slade,  and  Thompson,  "Lunar  Topography:  Global  Determination  by  Radar,"  Science  178  (1972):  939-948,  esp. 
notes  19  and  21,  p.  948. 

67.  Thompson,  "Map  of  Lunar  Radar  Reflectivity  at  7.5-m  Wavelength,"  Icarus  13  (1970):  363-370. 

68.  Brockelman,  Evans,  Ingalls,  Levine,  and  Pettengill,  Reflection  Properties  of  Venus  at  3.8  cm,  Report  456 
(Lexington:  Lincoln  Laboratory,  1968),  especially  pp.  34-35,  44,  and  49-50;  Rogers  and  Ingalls,  "Venus: 
Mapping  the  Surface  Reflectivity  by  Radar  Interferometry,"  Science  165  (1969):  797-799. 

69.  Rogers  and  Ingalls,  "Radar  Mapping  of  Venus  with  Interferometric  Resolution  of  the  Range-Doppler 
Ambiguity,"  Radio  Science  5  (1970):  425-433;  Rogers,  Ingalls,  and  Pettengill,  "Radar  Map  of  Venus  at  3.8  cm 
Wavelength,"  Icarus  21  (1974):  237-241. 

70.  AIO,  Research  in  Ionospheric  Physics,  Research  Report  RS  75  (Ithaca:  CRSR,  31  March  1969),  pp.  2  and 
11-12;  Annual  Summary  Report,  Center  for  Radiophysics  and  Space  Research,  July  I,  1968— June  30,  1969,  30  June  1969, 
p.  4. 


144 


TO  SEE  THE  UNSEEN 


Figure  22 

Diagram  of  Venus  surface  features  made  with  the  Haystack-Westford  interferometer.  Features  observed  with  the  Haystack- 
Westford  interferometer  are  indicated  variously  by  capital  letters,  Roman  numerals,  and  coordinate  numbers.  Goldstein 's  Alpha 
and  Beta  regions  are  indicated  (Region  a  and  Region  ft),  while  the  labels  given  by  Carpenter  are  shown  in  parentheses. 
(Courtesy  of  Alan  E.  E.  Rogers.) 


NORMAL  SCIENCE 


145 


Figure  23 

The  antenna  built  by  Areribo  Observatory  employee  and  radio  amateur  Sam  Harris  and  located  at  Higuillales  about  10  km 
from  the  main  dish.  Harris  and  his  antenna  are  a  reminder  of  the  important  role  self-taught  engineers  and  radio  amateurs 

have  played  in  the  design  and  construction  of  scientific  instruments,  particularly  in  the  field  of  astronomy.  (Courtesy  of  Ray 
Jurgens.) 


Undertaking  radar  interferometric  observations  of  Venus  at  Arecibo  was  Cornell 
graduate  student  Don  Campbell.  Campbell  came  to  Cornell  from  Australia,  his  native 
country,  where  he  had  studied  radio  astronomy  at  the  University  of  Sydney,  though  not 
through  the  agreement  between  the  two  universities.71  His  observations  of  Venus  in  1969 
with  the  radar  interferometer  formed  the  basis  of  his  doctoral  thesis.  Located  about  10  km 
from  the  Arecibo  Observatory  at  Higuillales  near  Los  Canos,  the  auxiliary  interferometer 
antenna  was  a  square  parabolic  section,  30  meters  by  30  meters  (100  ft  by  100  ft)  with  a 
movable  offset  feed  that  allowed  tracking  up  to  10°  from  the  zenith.72 


71.  Campbell  7  December  1993. 

72.  Donald  B.  Campbell,  "Radar  Interferometric  Observations  of  Venus,"  Ph.D.  diss.,  Cornell,  July  1971; 
AIO,  Research  in  Ionospheric  Physics,  Research  Report  RS  75  (Ithaca:  CRSR,  31  March  1969),  pp.  12-13;  Campbell, 
Jurgens,  Dyce,  F.  Sam  Harris,  and  Pettengill,  "Radar  Interferometric  Observations  of  Venus  at  70-Centimeter 
Wavelength,"  Science  170  (1970):  1090-1092. 


146 


TO  SEE  THE  UNSEEN 


Figure  24 

Radar  interferometric  image  of  Venus  made  by  Don  Campbell  far  his  1971  doctoral  dissertation,  which  was  a  study  of  Venus 
using  the  Arecibo  Observatory  and  Higuillales  antennas  as  a  radar  interferometer.  The  resolution  is  about  150  km.  The  Alpha 
region  can  be  seen  in  the  lower  right  corner,  and  Beta  Regio  is  visible  in  the  upper  left  corner.  (Courtesy  of  D.  B.  Campbell, 
Cornell  University.) 

As  Don  Campbell  remembered,  the  original  antenna  was  owned  by  Sam  Harris,  an 
Arecibo  employee,  who  used  it  for  his  backyard  amateur  radio  Moon  bounces.  Harris  was 
a  self-taught  engineer  well  known  in  the  "ham"  community  for  his  Moon-bounce  work  and 
had  a  column  in  the  popular  ham  journal  QSTfor  many  years.  "He  was  a  real  character," 
Campbell  reflected.  "I  always  enjoyed  working  with  him  and  in  getting  this  interferome- 
ter to  work  over  the  year  or  so  that  it  took."73 

The  430-MHz  radar  interferometer  went  into  operation  in  March  1969.  Jurgens, 
Campbell,  and  Dyce  made  interferometric  observations  of  Venus  between  20  March  and 
27  April  1969.  Unfortunately,  because  the  interferometer  antenna  was  so  small,  the  radar 
sensitivity  fell  sharply,  and  they  achieved  a  surface  resolution  of  only  300  km.  The  north- 
south  ambiguity  had  been  resolved,  but  at  the  loss  of  resolution.  From  the  data,  nonethe- 
less, Campbell  deduced  that  the  Faraday  region  was  the  same  as  Goldstein's  a  and 


73.      Campbell  7  December  1993. 


NORMAL  SCIENCE  147 


Carpenter's  F.  He  concluded,  "Despite  the  considerable  advance  that  the  radar  interfer- 
ometer represents  over  other  methods  in  mapping  the  surface  scattering  of  Venus  at  radio 
wavelengths,  we  still  know  very  litde  about  the  actual  nature  of  the  surface."74  In  other 
words,  the  images  really  said  nothing  about  the  planet's  geology. 

Campbell  returned  to  Cornell,  wrote  his  thesis,  and  graduated  in  July  1971.  He  then 
returned  to  Arecibo  as  a  Research  Associate  employed  by  the  NAIC.  An  improved  line 
feed  promised  better  observations  during  the  next  Venus  inferior  conjunction  in  1972. 
Although  delays  in  manufacturing  the  new  analog-to-digital  converters,  as  well  as  power 
outages,  caused  lost  observing  time,  Campbell  mapped  Venus  with  the  radar 
interferometer  and  achieved  a  resolution  of  about  100  km.  'That  was  the  last  fling  prior 
to  the  upgrade,"  Campbell  recalled.75 

Campbell  also  derived  Venus  topographical  (relief  or  surface  height)  information 
from  the  1972  data.  The  most  notable  result  was  the  discovery  of  what  appeared  to  be  a 
mountainous  zone  located  at  a  longitude  of  100°  and  having  a  peak  height  of  about  3  km. 
Although  not  at  the  same  location  as  Jurgens's  suspected  crater,  which  still  remained 
noted  only  in  his  dissertation,  these  mountains  became  the  second  clearly  identified  topo- 
graphical feature  on  the  surface  of  Venus,  following  a  pioneering  study  by  Smith  and 
other  Lincoln  Laboratory  and  MIT  investigators  at  Haystack  published  two  years  earlier.76 

Dick  Goldstein  also  observed  Venus  in  1972  with  a  radar  interferometer  that  com- 
bined the  Mars  Station  with  a  nearby  26-meter  antenna.  These  were  Goldstein's  first  Venus 
observations  with  an  interferometer.  Because  he  did  not  suffer  the  obstacles  thrown  at 
Don  Campbell,  Goldstein  was  able  to  update  his  large-scale,  low-resolution  map  of  Venus, 
which  now  had  a  resolution  of  10-15  km.  He  also  assembled  his  first  altitude  map.  A  gray 
scale  of  only  five  levels,  with  each  level  representing  a  set  of  altitude  values,  indicated  the 
degree  of  relief.  The  map  showed  a  large  crater  about  160  km  in  diameter  about  36°  West 
longitude  and  2°  South  latitude.  Goldstein  estimated  the  height  of  the  crater  rim  to  be 
about  500  meters  above  the  crater  floor.  This  was  the  first  distinguishable  crater  Goldstein 
found  in  his  radar  data;  several  years  earlier,  though,  Ray  Jurgens  had  identified  a  crater 
in  his  Cornell  dissertation.77 

By  the  1972  inferior  conjunction  of  Venus,  the  combination  of  range-Doppler  map- 
ping and  radar  interferometry  was  beginning  to  reveal  a  general  overview  of  the  planet's 
major  surface  features.  Although  Venus  still  looked  like  a  strange  fish  bowl  in  radar 
images,  lunar  range-Doppler  images  looked  more  like  photographs.  These  initial  tentative 
steps,  whatever  their  drawbacks,  began  to  set  in  motion  a  shift  in  the  planetary  radar  par- 
adigm from  astronomy  to  geology.  Like  the  far  more  successful  (because  they  looked  like 
and  had  greater  resolution  than  ground-based  photographs)  lunar  radar  images,  Venus 
radar  images  showed  that  planetary  radar  astronomy  could  tell  scientists  useful  informa- 
tion about  distant  surface  formations.  These  images  were  not  the  only  techniques  radar 
astronomers  had  for  describing  planetary  surface  conditions.  Coincidental  with  the  grad- 
ual evolution  of  planetary  radar  toward  these  geological  problems,  NASA  was  turning 
from  Apollo  to  planetary  missions. 


74.  Campbell  7  December  1993;  AIO,  Research  in  Ionospheric  Physics,  Research  Report  RS  75  (Ithaca: 
CRSR,  31  March  1969),  pp.  12-13;  Ibid.,  Research  Report  RS  76  (Ithaca:  CRSR,  30  September  1969),  p.  23; 
Campbell,  Jurgens,  Dyce,  Harris,  and  Pettengill,  "Radar  Interferometric  Observations,"  pp.  1090-1092. 

75.  Campbell  7  December  1993;  NAIC  QR  Q2/1972,  pp.  3-4,  and  Q3/1973,  pp.  3-4. 

76.  Campbell,  Dyce,  Ingalls,  Pettengill,  and  Shapiro,  "Venus:  Topography  Revealed  by  Radar  Data," 
Science  175   (1972):  514-516.  Smith,  Ingalls,  Shapiro,  and  Ash,  "Surface-Height  Variations  on  Venus  and 
Mercury,"  Radio  Science  5  (1970):  411-423,  presented  an  earlier  topographical  study  of  Venus  made  from 
Haystack  data  taken  over  a  period  of  years.  That  study  was  confined  to  the  planet's  equator  and  found  a  2-km 
feature.  It  was  remarkable  for  the  variety  of  radar  techniques  used,  as  well  as  for  its  discovery  of  the  first  topo- 
graphical feature  on  Venus. 

77.  Rumsey,  Morris,  R.  Green,  and  Goldstein,  "A  Radar  Brightness  and  Altitude  Image  of  a  Portion  of 
Venus,"  Icarus  23  (1974):  1-7;  Jurgens,  "A  Study  of  the  Average  and  Anomalous  Radar  Scattering,"  pp.  87-110. 


Chapter  Six 

Pioneering  on  Venus  and  Mars 

Range-Doppler  mapping  and  radar  techniques  for  determining  the  roughness, 
height  variations,  and  other  characteristics  of  planetary  surfaces  came  into  their  own  in 
the  early  1970s  and  shaped  the  kinds  of  problems  planetary  radar  could  solve.  Radar  tech- 
niques and  the  kinds  of  problems  they  solved  were  cross-fertilizing  forces  in  the  evolution 
of  planetary  radar  astronomy.  In  the  early  1970s,  NASA  was  shifting  gears.  The  landing  of 
an  American  on  the  Moon,  the  zenith  of  the  Apollo  program,  was  history  when  in 
December  1972  Apollo  17  became  the  last  to  touch  down  on  the  Moon.  Now  the 
unmanned  exploration  of  the  planets  began  in  earnest. 

The  usefulness  of  radar  to  planetary  exploration  had  been  argued  by  radar 
astronomers  as  early  as  the  1959  Endicott  House  conference.  However,  not  everyone 
shared  their  enthusiasm.  Smith  and  Carr,  for  example,  in  their  1964  book  on  radio  astron- 
omy, wrote:  "It  is  inevitable  that  the  importance  of  the  exploration  of  the  planetary  system 
by  radar  will  diminish  as  instruments  and  men  are  carried  directly  to  the  scene  by  space 
vehicles.  However,  that  time  is  still  to  come.  In  the  meantime,  the  information  that  radar 
provides  will  be  vital  in  man's  great  effort  to  conquer  space."1  Soviet  radar  astronomers  B. 
I.  Kuznetsov  and  I.  V.  Lishin  expressed  similar  sentiments  in  1967:  "Certainly,  radar  bom- 
bardment of  the  planets  gives  less  information  than  a  direct  investigation  of  them  with 
spaceships  and  interplanetary  automatic  stations."  However,  they  did  foresee  that  infor- 
mation about  planetary  surfaces  would  "help  designers  in  the  development  of  spaceships 
intended  for  making  a  'soft'  landing  on  the  planets."2 

As  NASA  came  to  fund  planetary  radar  research,  experiments  and  NASA  missions 
became  linked.  Goldstone  antenna  time  depended  on  mission  approval,  while  Haystack 
radar  funding  was  tied  to  specific,  mission-oriented  tasks.  It  is  not  surprising,  then,  that 
planetary  radar  in  the  1970s  evolved  in  point  and  counterpoint  to  the  NASA  space  pro- 
gram, at  first  modestly  to  correct  data  returned  from  Soviet  and  American  missions  to 
Venus,  next  to  help  select  a  Mars  landing  site,  and  then  to  image  Venus  from  a  spacecraft. 
This  evolution  followed  from  the  precedent  established  by  NASA's  funding  of  lunar  radar 
imaging  for  the  Apollo  program.  The  Pioneer  Venus  radar  imaging  and  altimetry  missions 
took  radar  astronomy  off  the  ground  and  into  space.  Again,  just  as  ground-based  radar 
astronomy  had  piggybacked  itself  onto  Big  Science  radio  astronomy  facilities,  so  the 
Pioneer  Venus  radar  attached  itself  to  a  larger  mission  to  explore  the  planet's  atmosphere. 

The  new  techniques  and  problem-solving  activities  drew  radar  astronomers  into  clos- 
er contact  with  planetary  scientists  from  a  variety  of  disciplines  who  were  not  necessarily 
familiar  with  radar  or  the  interpretation  of  radar  results.  It  was  one  thing  for  radar 
astronomers  to  determine  a  spin  rate  for  a  planet  or  the  value  of  the  astronomical  unit; 
astronomers  easily  grasped  those  discoveries.  However,  when  radar  astronomers  described 
planetary  surfaces  in  such  abstract  terms  as  root-mean-square  slope  to  geologists,  whose  dis- 
cipline rests  heavily  on  hands-on  field  knowledge,  a  communication  problem  arose  and 
serious  misinterpretations  and  misunderstandings  of  radar  results  ensued. 


1.  Smith  and  Carr,  pp.  130-131. 

2.  Kuznetsov  and  Lishin,  p.  201. 


149 


1 50  TO  SEE  THE  UNSEEN 


The  Radar  Radius  of  Venus 

On  18  October  1967,  the  Soviet  Venera  4  space  probe  entered  the  atmosphere  of 
Venus  and  began  to  transmit  data  back  to  Earth.  From  that  data,  Soviet  scientists  calculat- 
ed a  value  for  the  radius  of  Venus,  6,079  ±  3  km,  on  the  assumption  that  the  break  in  the 
probe's  transmissions  indicated  that  it  had  reached  the  planet's  surface.  On  the  following 
day,  Mariner  5  passed  within  4,100  km  of  Venus  and  conducted  a  series  of  experiments. 
From  the  data  beamed  back  to  Earth,  Mariner  scientists  at  JPL  calculated  a  value  for  the 
radius  of  Venus  that  was  compatible  with  that  determined  by  their  Soviet  colleagues,  6,080 
±  10km. 

The  data  from  Venera  4  and  Mariner  5  were  consistent  with  each  other  and  with  the 
latest  optical  data,  which  yielded  a  value  of  6,089  ±  6  km.  However,  the  space  and  optical 
values  differed  markedly  from  the  size  of  the  radius,  6,056  ±1.2  km,  determined  by  Irwin 
Shapiro,  Bill  Smith,  and  Michael  Ash  with  the  Lincoln  Laboratory  radars  as  part  of  the 
Planetary  Ephemeris  Program.3 

If  the  spacecraft  and  optical  measurements  were  correct,  then  the  radar  data  or  its 
analysis  were  in  error.  The  radius  of  Venus  was  a  critical  radar  measurement;  its  value,  for 
example,  could  serve  to  study  the  planet's  topography.  Radar  astronomers  associated  with 
MIT  and  the  Haystack  Observatory,  Gordon  Pettengill,  Irwin  Shapiro,  Dick  Ingalls, 
Michael  Ash,  and  Marty  Slade,  and  those  at  the  Arecibo  Observatory,  Rolf  Dyce,  Don 
Campbell,  Ray  Jurgens,  and  Tommy  Thompson,  took  up  the  challenge  in  collectively 
authored  papers  that  appeared  in  Science  and  the  Journal  of  the  Atmospheric  Sciences.  The 
publications  embraced  both  a  general  audience  and  atmospheric  specialists. 

In  addition  to  data  collected  previously  at  Millstone,  Haystack,  and  Arecibo,  the  MLT- 
Arecibo  radar  astronomers  added  data  from  fresh  radar  observations  made  in  1966  and 
1967  as  well  as  optical  observations  from  the  U.S.  Naval  Observatory  from  the  period  1950 
through  1965.  The  magnitude  of  the  data  base  was  impressive  and  convincing.  The 
Arecibo  and  MIT  investigators  analyzed  their  data  separately  and  obtained  radii  of  6,052 
±  2  km  and  6,048  ±  1  km,  respectively.  They  concluded  that  Mariner  5  had  misjudged  its 
distance  from  the  planet's  center  by  about  10  km,  and  that  "the  simple  possibility  that 
Venera  4  underestimated  its  altitude  by  about  35  km  cannot  yet  be  ruled  out."4 

Dewey  Muhleman,  now  professor  of  planetary  science  at  the  California  Institute  of 
Technology,  with  Bill  Melbourne  and  D.  A.  O'Handley  of  JPL,  made  observations  of  Venus 
between  May  1964  and  October  1967  with  the  Goldstone  Mars  Station.  Because  their  data 
were  reported  only  in  internal  JPL  reports,  Lincoln  Laboratory  did  not  use  that  data. 
Consequently,  they  asserted,  their  observations  constituted  "an  entirely  independent  data 
source."  Muhleman  and  his  JPL  colleagues  determined  a  value  for  the  radius  of  Venus  of 
6,053.7  ±  2.2  km,  in  strong  agreement  with  the  MIT  and  Arecibo  results.5 

Arvydas  Kliore  and  Dan  L.  Cain,  two  JPL  scientists  on  the  Mariner  mission,  saw  the 
agreement  between  the  Caltech-JPL  and  the  Arecibo-MIT  values  and  realized  that  "the 
consistency  between  reductions  from  data  taken  by  different  radars  and  reduced  by  dif- 
ferent investigators  cannot  be  ignored."  They  discovered  that  the  different  timing  systems 


3.  C.  W.  Snyder,  "Mariner  5  Flight  past  Venus,"  Science  158  (1967):  1665-1669;  Arvydas  Kliore,  Gerald 
S.  Levy,  Dan  L.  Cain,  Gunnar  Fjeldbo,  S.  Ichtiaque  Rasool,  "Atmosphere  and  Ionosphere  of  Venus  from  the 
Mariner  5  S-band  Radio  Occultation  Experiment,"  Science  158  (1967):  1683-1688;  Gerard  H.  de  Vaucouleurs  and 
Donald  H.  Menzel,  "Results  of  the  Occultation  of  Regulus  by  Venus,  July  7,  1959,"  Nature  188  (1960):  28-33;  Ash, 
Shapiro,  and  Smith,  Astronomical  Journal  72  (1967):  338-350. 

4.  Ash,  Campbell,  Dyce,  Ingalls,  Jurgens,  Pettengill,  Shapiro,  Martin  A.  Slade,  and  Thompson,  The 
Case  for  the  Radar  Radius  of  Venus,"  Science  160  (1968):  985-987;  Ash,  Campbell,  Dyce,  Ingalls,  Jurgens, 
Pettengill,  Shapiro,  Slade,  Smith,  and  Thompson,  The  Case  for  the  Radar  Radius  of  Venus,"  Journal  of  the 
Atmospheric  Sciences  25  (1968):  560-563;  Shapiro  1  October  1993. 

5.  William  G.  Melbourne,  Muhleman,  and  D.  A.  O'Handley,  "Radar  Determination  of  the  Radius  of 
Venus,"  Science  160  (1968):  987-989. 


PIONEERING  ON  VENUS  AND  MARS  1 5 1 


used  by  the  Deep  Space  Network  to  acquire  Mariner  5  data,  namely  Station  Time  and 
Ephemeris  Time,  had  introduced  an  error  into  their  calculations.  The  amount  of  that 
error,  8.85  km,  brought  the  Mariner  5  value  for  the  radius  of  Venus  in  line  with  the  radar 
results. 

To  explain  what  was  now  the  anomalous  Soviet  value  for  the  radius  of  Venus,  Kliore 
and  Cain  concluded  that  either  the  Venera  4  capsule  landed  on  a  peak  or  plateau  that  was 
about  25  km  high  and  not  detected  by  planetary  radar  or  the  capsule  stopped  transmit- 
ting before  reaching  the  solid  surface  of  Venus.  The  problem  with  Venera  4,  Don 
Campbell  ventured,  "was  tied  up  in  an  ambiguity  difficulty  in  their  own  radar  system, 
which  was  a  pulsed  altimeter  radar.  I  think,  frankly,  that  the  scientists  who  reported  the 
results  did  not  know  how  it  worked.  It  was  a  military  radar  altimeter.  They  were  just  pro- 
vided the  answer,  essentially.  Although  I  don't  know,  and  probably  didn't  know  at  the  time 
either,  what  exactly  the  circumstances  were,  that  was  the  impression  that  one  got."6 

"A  Little  Radar  Knowledge  is  a  Dangerous  Thing." 

Well  before  radar  astronomers  began  collaborating  with  geologists,  misinterpreta- 
tions of  radar  data  occurred.  In  fact,  radar  astronomers  themselves  were  not  immune  to 
misconstruing  radar  results,  as  the  case  of  the  radar  brightness  of  Mars  illustrates.  In  ini- 
tial observations  of  that  planet,  radar  astronomer  Dick  Goldstein  assumed  a  relationship 
between  radar  brightness  and  optical  darkness.  Arecibo  observations  appeared  to  confirm 
that  relationship,  which  snowballed  among  planetary  astronomers  into  a  hypothesis  that 
correlated  radar  brightness  and  topography  (continental  blocks  and  dry  ocean  basins).  A 
reconsideration  of  evidence  showed  no  such  correlation. 

When  Dick  Goldstein  made  his  pioneering  radar  observations  of  Mars  in  1963,  he 
discovered  what  he  thought  was  a  relationship  between  radar  "brightness,"  that  is,  the 
average  amount  of  power  returned  in  the  echo  from  a  given  surface  area  of  the  planet, 
and  the  optical  darkness  of  that  same  surface  area.  Goldstein  constructed  what  he  called 
a  radar  map  of  Mars,  which  showed  variations  in  radar  brightness.  He  noted,  for  example, 
that  the  Syrtis  Major  region  appeared  bright  to  the  radar,  but  dark  to  visual  observations. 
Because  radar  brightness  is  a  function  of  surface  roughness,  he  argued,  the  brightest 
radar  areas  were  regions  of  flatness,  while  dark  radar  areas  were  topographically  rough.7 

In  1965,  Goldstein  observed  Mars  at  the  next  opposition  and  again  looked  at  the 
radar  brightness  of  the  planet's  surface,  this  time  at  latitude  21°  North.  The  average  power 
returned  (radar  brightness)  reached  a  maximum  in  the  region  of  Trivium  Charontis  (an 
optically  dark  area) ,  then  dropped  off  abruptly  when  the  neighboring  area  of  Elysium 
(optically  bright)  was  the  radar  target.  Based  on  the  known  relationship  between  surface 
roughness  and  radar  brightness,  Goldstein  concluded  the  existence  of  a  very  smooth, 
strongly  reflecting  area  extending  20°  to  30°  in  longitude  and  having  an  unknown  latitu- 
dinal extent  in  the  region  of  Trivium  Charontis.8 

During  the  same  opposition,  Gordon  Pettengill,  Rolf  Dyce,  and  Don  Campbell 
observed  Mars  with  the  UHF  radar  at  Arecibo.  When  they  compared  their  results  with  an 
optical  map  of  Mars,  the  Arecibo  investigators  found  a  general  tendency  for  weak  echoes 
to  correlate  with  the  (optically)  lighter  areas  of  Mars,  such  as  Arabia,  Elysium,  Tharsis,  and 


6.  Kliore  and  Cain,  "Mariner  5  and  the  Radius  of  Venus,"  Journal  of  Atmospheric  Sciences  25  (1968):  549- 
554;  Campbell  7  December  1993.  Murray,  pp.  90-91,  provides  further  anecdotal  accounting  of  Soviet  embar- 
rassment over  the  incident. 

7.  Goldstein  and  Gillmore,  "Radar  Observations  of  Mars,"  Science  141  (1963):  1172. 

8.  Goldstein,  "Mars:  Radar  Observations,  "Science  150  (1965):  1715-1717.  His  results  were  reported  also 
in  Goldstein,  "Preliminary  Mars  Radar  Results,"  Radio  Science  69D  (1965):  1625-1627. 


1 52  TO  SEE  THE  UNSEEN 


Amazonis,  and  a  tendency  for  strong  echoes  to  correspond  with  visually  darker  features, 
such  as  the  regions  near  Trivium  Charontis  and  Syrtis  Major.  They  did,  however,  note  that 
the  correlation  between  radar  brightness  and  optical  lightness  was  not  perfect.  For 
instance,  the  peak  radar  echo  near  Trivium  Charontis  occurred  at  201°  longitude,  which 
is  on  one  edge  of  the  visually  dark  region.  Likewise,  the  visually  darkest  region  of  Syrtis 
Major  corresponded  to  a  local  minimum  in  echo  strength.9 

The  Arecibo  results  were  rather  convincing.  Not  only  had  they  been  obtained  from 
roughly  the  same  area  (22°  North  latitude)  that  Goldstein  had  studied,  but  the  Arecibo 
and  Goldstone  observations  had  been  made  at  two  different  frequencies  (UHF  vs.  S- 
band) .  The  persistence  of  the  correlation  between  optical  darkness  and  radar  brightness 
at  both  frequencies  was  persuasive. 

Astronomers  Carl  Sagan  and  James  B.  Pollack,  then  at  the  Smithsonian  Astrophysical 
Observatory,  and  Richard  Goldstein  carried  out  a  lengthy  and  detailed  analysis  of  the  JPL 
1963  and  1965  radar  data.  They  maintained  and  extensively  documented  the  correlation 
between  high  radar  reflectivity  and  optical  darkness,  despite  some  exceptions.  Not  only 
did  radar  bright  and  optically  dark  areas  correlate;  they  claimed  that  topography  and 
radar  brightness  also  were  related.  Dark  areas  were  elevations  similar  to  continental 
blocks;  bright  areas  were  comparable  to  dry  ocean  basins.10  The  notion  that  Martian  dark 
areas  were  elevated  land  masses  rapidly  gathered  support  from  other  planetary 
astronomers  in  the  United  States  and  Britain.11 

Nonetheless,  Pettengill,  who  had  participated  in  the  earlier  effort  at  Arecibo,  now 
opposed  the  correlation  of  visual  darkness  and  radar  brightness  and  undertook  observa- 
tions at  Haystack,  during  the  1967  opposition,  specifically  in  order  to  oppose  the 
prevailing  hypothesis  that  now  correlated  topography  and  radar  brightness.  Pettengill 
conducted  a  series  of  straightforward,  precise  range  measurements  to  establish  the 
topographical  variations  along  latitude  22°  North.  Then  he  compared  those  range  mea- 
surements with  the  average  planetary  radius  taken  from  the  planetary  ephemeris  data.  He 
also  plotted  echo  power  over  longitude  along  that  same  latitude. 

Pettengill  found  no  significant  correlation  between  radar  brightness  and  topogra- 
phy. A  direct  comparison  between  the  radar  results  and  a  map  of  visible  Martian  surface 
features  revealed  no  clear  one-to-one  association  between  bright  or  dark  areas  and 
topographical  extremes.  What  others  had  observed  as  variations  in  radar  brightness, 
Pettengill  argued,  resulted  from  the  deviant  properties  of  relatively  small  regions  of  the 
surface  near  the  subradar  point.  Moreover,  he  pointed  out,  arguments  for  the  hypotheti- 
cal correlation  between  elevation  extremes  and  brightness  had  been  based  largely  on 
conclusions  drawn  from  a  range  of  disparate  isolated  locations.  Further  Haystack  obser- 
vations of  Mars  carried  out  under  Pettengill's  direction  reinforced  the  conclusion  that  no 
correlation  existed  between  regions  of  high  radar  reflectivity  and  optically  dark  areas.12 

Perhaps  one  of  the  most  notorious  examples  of  misinterpreted  radar  results  is  that 
of  Thomas  Gold  of  Cornell  University.  Gold  had  been  developing  theories  about  the  lunar 
surface  since  the  1950s.  Long  before  he  ever  saw  any  radar  data,  Gold  favored  a  meteoric 


9.  Dyce,  Pettengill,  and  Sanchez,  "Radar  Observations  of  Mars  and  Jupiter  at  70  cm,"  The  Astronomical 
Journal!?.  (1967):  771-777;  Campbell  7  December  1993. 

10.  Carl  Sagan,  James  B.  Pollack,  and  Goldstein,  "Radar  Doppler  Spectroscopy  of  Mars:  1.  Elevation 
Differences  between  Bright  and  Dark  Areas,"  The  Astronomical  Journal  72  (1967):  20-34.  This  article  appeared 
earlier  as  Sagan,  Pollack,  and  Goldstein,  Radar  Doppler  Spectroscopy  of  Mars:  1.  Elevation  Differences  between  Bright  and 
Dark  Areas,  Special  Report  221  (Cambridge:  SAO,  6  September  1966). 

11.  See,  for  example,  D.  G.  Rea,  The  Darkening  Wave  on  Mars,"  Nature  210  (1964):  1014-1015;  R.  A. 
Wells,  "Evidence  that  the  Dark  Areas  on  Mars  are  Elevated  Mountain  Ranges,"  Nature  207  ( 1965) :  735-736.  Rea 
was  at  the  University  of  California  at  Berkeley,  and  Wells  at  University  College,  London. 

12.  Pettengill,  Counselman,  Rainville,  and  Shapiro,  "Radar  Measurements  of  Martian  Topography,"  The 
Astronomical  Journal  74  (1969):  461-482;  Pettengill,  Rogers,  and  Shapiro,  "Martian  Craters  and  a  Scarp  as  Seen 
by  Radar,"  Science  174  (1971):  1324. 


PIONEERING  ON  VENUS  AND  MARS  1 53 


explanation  for  lunar  craters  and  developed  an  explanation  for  the  presence  of  vast  flat 
level  surfaces  that  did  not  require  the  deposition  of  volcanic  lava.  His  hypothesis  was  that 
these  flat  expanses  consisted  of  dust  from  meteoric  impacts.  Gold  interpreted  radar  obser- 
vations of  the  Moon  as  supporting  the  existence  of  a  surface  layer  of  fine  rock  powder  sev- 
eral meters  deep,  which  a  seismic  experiment  carried  out  by  Apollo  12  allegedly  support- 
ed. The  implications  for  landing  an  American  on  the  Moon  were  obvious;  an  astronaut 
might  sink  several  centimeters  into  the  powder  or  even  "wallow"  in  it.13 

Many  scientists  greeted  Gold's  prediction  of  a  deep  layer  of  powder  with  disbelief.  As 
Don  E.  Wilhelms  wrote,  'Tour  Surveyor  and  six  Apollo  landings  established  the  strength, 
thickness,  block  content,  impact  origin,  and  paucity  of  meteoric  material  in  the  Moon's 
regolith.  There  is  fine  pulverized  soil,  but  it  is  weak  only  for  a  few  centimeters  of  its  thick- 
ness. Yet  Thomas  Gold  is  still  fighting  the  battle.  Still  believing  radar  more  than  geologi- 
cal sampling..."14  Wilhelms  went  so  far  as  to  state,  "A  little  radar  knowledge  is  a  dangerous 
thing."15  Gold  later  defended  himself  by  insisting  that  although  the  "Gold  dust"  (as  it  has 
come  to  be  called)  would  be  many  meters  thick,  the  idea  of  sinking  in  it  was  a  "total  mis- 
conception."16 

The  Apollo  program  started  the  process  of  bringing  together  radar  astronomers  and 
geologists.  The  lunar  radar  images  created  by  Tommy  Thompson  and  Stan  Zisk  from  data 
gathered  at  Arecibo  and  Haystack  contributed  not  inconsequentially  to  America's  explo- 
ration of  the  Moon.  On  occasion,  nonetheless,  radar  astronomers  misinterpreted  lunar 
landing  sites.  In  one  instance,  a  landslide  was  mistaken  for  a  field  of  boulders  at  the  Apollo 
17  landing  site,  while  in  another  radar  astronomers  incorrectly  characterized  the  rough- 
ness of  the  Apollo  14  Cone  Crater  site.  These  problems,  however,  arose  not  from  mistak- 
en readings  of  radar  images,  but  from  misinterpretations  of  the  root-mean-square  slope 
and  dielectric  constants  of  the  surface.17 


Landing  on  Mars 


During  the  preparation  for  the  Viking  mission  to  Mars,  radar  astronomers  encoun- 
tered the  challenge  of  making  radar  data  understandable  to  NASA  mission  personnel 
unfamiliar  with  the  interpretation  of  radar  results.  Until  Congress  funded  the  Voyager 
mission  to  Jupiter  and  Saturn,  Viking  was  NASA's  biggest  and  most  expensive  program  for 
planetary  exploration.  Viking  was  to  land  on  that  planet,  and  NASA  needed  a  landing  site 
that  was  both  safe  for  the  lander  and  interesting  to  scientists.  Radar  astronomers  collect- 
ed and  interpreted  data  to  help  with  the  selection  of  candidate  sites. 

The  selection  of  the  Viking  lander  site  also  brought  together  ground-based  planetary 
radar  astronomy  and  the  Stanford  bistatic  radar  approach  under  the  aegis  of  NASA. 
Ground-based  planetary  radar  astronomy  had  distinguished  itself  from  "space  explo- 
ration" (the  Stanford  approach),  but  the  boundary  between  ground-based  planetary 
radar  astronomy  and  "space  exploration"  softened,  as  radar  astronomers  played  an 
expanding  role  in  NASA  missions  of  planetary  exploration  and  as  Stanford  investigators 
extended  their  field  of  applications. 


13.  Gold,  The  Lunar  Surface,"  Monthly  Notices  of  the  Royal  Astronomical  Society  115  (1955):  585-604; 
Malcolm  J.  Campbell,  Juris  Ulrichs,  and  Gold,  "Density  of  the  Lunar  Surface,"  Science  159  (1968):  973;  Gold  and 
Steven  Soter,  "Apollo  12  Seismic  Signal:  Indication  of  a  Deep  Layer  of  Powder,"  Science  169  (1970):  1071-1075; 
Gold,  The  Moon's  Surface,"  in  Wilmot  N.  Hess,  Menzel  and  John  A.  O'Kcefe,  eds.,  The  Nature  of  the  Lunar 
Surface  (Baltimore:  Johns  Hopkins  University  Press,  1966),  pp.  107-121;  Gold,  "Conjectures  about  the  Evolution 
of  the  Moon,"  The  Moon  7  (May-June  1973):  293-306. 

14.  Don  E.  Wilhelms,  To  A  Rocky  Moon:  A  Geologist's  History  of  Lunar  Exploration  (Tucson:  The  University 
of  Arizona  Press,  1993),  p.  347. 

15.  Wilhelms,  p.  299. 

16.  Gold  14  December  1993. 

17.  Schaber  27  June  1994;  Thompson  29  November  1994. 


154  TO  SEE  THE  UNSEEN 


Images  of  Mars  from  earlier  missions  provided  a  clue  in  selecting  candidate  Viking 
landing  sites.  As  early  as  1965,  Mariner  4  had  flown  past  Mars  and  snapped  22  pictures  of 
about  one  percent  of  the  planet's  surface.  Mariner  6  and  Mariner  7  took  about  200  images 
of  around  10  percent  of  the  surface  in  1969.  The  goal  of  Mariner  9,  to  make  a  complete 
photographic  map  of  Mars  was  thwarted;  when  the  spacecraft  arrived  at  its  destination,  a 
planet-wide  dust  storm  concealed  most  of  the  surface.  Once  the  storm  appeared  to  sub- 
side, Mariner  9  began  to  transmit  images  to  Earth  in  early  1972,  and  the  study  of  Martian 
topography  began  in  earnest.18 

Unlike  the  Mariner  flybys,  Viking  was  to  study  Mars  by  landing  on  its  surface.  A  pair 
of  orbiters  was  to  focus  on  atmospheric  studies,  while  a  pair  of  landers  studied  the  surface, 
if  all  went  well.  If  the  Viking  landers  were  to  touch  down  on  a  large  rock  or  precariously 
on  an  edge,  the  entire  mission  might  be  lost.  The  clearance  under  the  lander  body  was 
only  23  cm  (nine  inches) ,  so  a  relatively  smooth  landing  surface  was  a  prime  mission  req- 
uisite. 

NASA  selected  landing  and  backup  sites  for  two  landers.  The  sites  had  to  be  around 
25°  North  latitude;  at  any  other  latitude,  the  orbiter  solar  panels  would  not  receive  suffi- 
cient solar  energy  to  keep  the  spacecraft's  batteries  charged.  That  power  was  critical  to  the 
transmission  of  telemetry  to  Earth. 

A  major  criteria  for  selecting  candidate  landing  sites  was  the  potential  availability  of 
water.  Water  meant  the  possibility  of  finding  life,  which  was  a  major  mission  objective. 
Chryse,  located  at  19.5°  North  and  34°  West,  was  scientifically  interesting,  because  it  is 
located  at  the  lower  end  of  a  valley  where  the  largest  group  of  Martian  channels  diverges. 
The  site  may  have  been  a  drainage  basin  for  a  large  portion  of  equatorial  Mars  and,  there- 
fore, would  have  collected  deposits  of  a  variety  of  surface  materials.19 

Despite  the  scientific  interest  in  Chryse  as  the  prime  Viking  landing  site,  the  high- 
resolution  Mariner  9  images  lacked  sufficient  resolution  to  determine  the  site's  safety.  As 
Don  Campbell  recalled:  "NASA  was  very  concerned  about  how  rough  the  surface  was  at 
the  landing  site.  None  of  the  Mariner  9  imagery  had  any  hope  of  giving  information  at 
scales  of  10  cm  to  a  meter,  which  was  the  amount  of  surface  roughness  that  they  cared 
about."20  Mariner  9  images  had  a  resolution  of  about  100  meters,  roughly  the  size  of  a 
football  field,  and  simply  did  not  show  objects  small  enough  to  jeopardize  the  touchdown 
of  the  lander,  which  had  a  clearance  of  only  23  cm.  The  radar  data,  in  contrast,  were  capa- 
ble of  indicating  surface  roughness  down  to  objects  only  a  few  centimeters  across.  Once 
again,  radar  was  going  to  try  to  solve  a  problem  left  unresolved  by  optical  methods. 

The  Stanford  Center  for  Radar  Astronomy 

In  order  to  help  select  candidate  Viking  landing  sites,  NASA  turned  to  radar  astron- 
omy and  its  ability  to  appraise  gross  and  fine  surface  characteristics.  The  chief  advocate 
for  the  use  of  radar  data  was  Carl  Sagan.  Sagan  was  concerned  about  the  possibility  that 
the  first  lander  might  disappear  in  quicksand  at  one  of  the  equatorial  sites.  In  general,  he 
believed  that  too  much  stress  had  been  placed  on  visual  images  with  a  resolution  of  only 
100  meters  and  not  enough  on  radar,  which  could  indicate  surface  irregularities  at  the 


18.  Corliss,  The  Viking  Mission  to  Mars,  NASA  SP-334  (Washington:  NASA,  1974),  pp.  6-8;  Thomas  A. 
Mutch,  Raymond  E.  Arvidson,  James  W.  Head,  III,  Kenneth  L.Jones,  R.  Stephen  Saunders,  The  Geology  of  Mars 
(Princeton:  Princeton  University  Press,  1976). 

19.  Martin  Marietta  Aerospace,  The  Viking  Mission  to  Mars  (Denver:  Martin  Marietta,  1975) ,  pp.  111-21  to 
IH-23;  Edward  Clinton  Ezell  and  Linda  Neuman  Ezell,  On  Mars:  Exploration  of  the  Red  Planet,  1958-1978,  NASA 
SP-4212  (Washington:  NASA,  1984),  p.  298. 

20.  Campbell  8  December  1993. 


PIONEERING  ON  VENUS  AND  MARS  155 


10-cm  scale.  Sagan  urged  further  study  of  the  meaning  of  the  radar  data,  so  that  the  prop- 
erties of  the  Martian  soil  could  be  better  evaluated. 

In  response  to  Sagan's  urging,  on  1  March  1973,  Tom  Young  and  Gerald  Soffen, 
Viking  science  integration  manager  and  project  scientist,  respectively,  met  with  Von 
Eshleman  and  Len  Tyler  of  the  Stanford  Center  for  Radar  Astronomy.  Both  already  were 
investigators  on  Viking  with  a  radio  scattering  experiment.  Young  and  Soffen  asked  Tyler 
to  acquire,  analyze,  and  interpret  radar  data  and  to  set  up  a  radar  study  team  for  the  selec- 
tion of  Viking  landing  sites.  Tyler  agreed.21 

The  Viking  Project  Office  probably  approached  the  Stanford  Center  for  Radar 
Astronomy  because  Eshleman  and  Tyler  already  were  Viking  investigators,  but  also 
because  of  the  Center's  experience  in  interpreting  Doppler  spectra  from  the  lunar  sur- 
face. The  Stanford  Center  for  Radar  Astronomy  (SCRA)  was  a  joint  venture  of  Stanford 
University  and  the  Stanford  Research  Institute  (SRI)  created  in  1962  to  foster  scientific 
and  engineering  efforts  and  to  provide  graduate  student  training  in  radar  astronomy  and 
space  science.  It  was  the  umbrella  organization  for  Eshleman  and  his  program  of  bistatic 
radar  astronomy.  A  NASA  grant  underwrote  the  Center  itself,  while  additional  military 
and  civilian  awards  supported  a  range  of  theoretical  and  experimental  radio  and  radar 
research  on  space,  ionospheric,  and  communication  theory  topics.22 

Len  Tyler,  as  did  his  Stanford  colleague  Dick  Simpson,  brought  considerable  knowl- 
edge of  radar  techniques  to  the  effort.  A  graduate  of  Georgia  Institute  of  Technology, 
Tyler  had  been  at  the  SCRA  since  1967,  when  he  received  his  doctorate  in  electrical  engi- 
neering from  Stanford  under  Von  Eshleman.  Tyler  invited  Dick  Simpson  to  work  on  the 
Viking  data.  Simpson,  a  graduate  of  the  MIT  electrical  engineering  program,  had  joined 
the  SCRA  in  1967  as  a  research  assistant  while  working  on  his  MS  and  Ph.D.  in  electrical 
engineering.23 

Later,  during  the  1978  Mars  opposition,  Simpson  and  Tyler  conducted  29  bistatic 
radar  observations  using  the  Viking  1  and  2  orbiter  spacecraft  in  conjunction  with  the 
DSN  antennas  at  Goldstone  and  Tidbinbilla  (near  Canberra,  Australia)  to  study  Mars  sur- 
face roughness  and  scattering  properties,  and  Simpson  made  ground-based  monostatic 
radar  observations  of  Mars,  not  associated  with  the  Viking  project,  at  Arecibo.24  Their 
radar  work,  however,  began  much  earlier,  during  the  Apollo  era. 

For  his  doctoral  thesis,  Tyler  had  developed  a  method  for  creating  two-dimensional 
surface  images  of  the  Moon  using  an  Earth-based  transmitter  and  a  spacecraft  receiver 
and  based  on  theoretical  work  laid  out  earlier  by  another  SCRA  investigator,  Gunnar 
Fjeldbo  (now  known  as  Lindal).25  Tyler  first  applied  his  bistatic  imaging  method  on 
Explorers  33  (which  missed  the  Moon)  and  35,  the  first  U.S.  spacecraft  to  orbit  the  Moon, 


21.  Tyler  10  May  1994;  Ezell  and  Ezell,  pp.  309  and  320-321;  "VOIR,  Proposal  to  the  NASA  Management 
Section,  2/79,"  Box  13,  JPLMM. 

22.  SCRA,  Research  at  the  Stanford  Center  for  Radar  Astronomy,  semi-annual  status  report  no.  2  for  the  peri- 
od 1  July-31  December  1963  (Stanford:  RLSEL,  February  1964),  pp.  3-4;  Ibid.,  no.  4  for  the  period  1  July  - 
31  December  1964  (Stanford:  RLSEL,  January  1965),  pp.  2-3;  Ibid.,  no.  5  for  the  period  1  January-30June  1965 
(Stanford:  RLSEL,  July  1965),  pp.  5-6;  Ibid.,  no.  6  for  the  period  1  July-31  December  1965  (Stanford:  RLSEL, 

January  1966),  p.  4;  Ibid.,  no.  7  for  the  period  1  January-31  June  1966  (Stanford:  RLSEL,  August  1966),  p.  5; 
Ibid.,  no.  9  for  the  period  1  January-30  June  1967  (Stanford:  RLSEL,  9  July  1967),  pp.  6-8;  John  E.  Ohlson, 
A  Radar  Investigation  of  the  Solar  Corona,  SU-SEL-67-  071,  Scientific  Report  21  (Stanford:  RLSEL,  August  1967). 

23.  Simpson  10  May  1994. 

24.  Richard  A.  Simpson  and  G.  Leonard  Tyler,  "Viking  Bistatic  Radar  Experiment:  Summary  of  First- 
Order  Results  Emphasizing  North   Polar  Data,"  Icarus  46   (1981):   361-389;  Simpson  and  Tyler,   "Radar 
Measurement  of  Heterogeneous  Small-Scale  surface  Texture  on  Mars:  Chryse,"/ouma/  of  Geophysical  Research  85 
(1980):  6610-6614;  Simpson  10  May  1994. 

25.  Fjeldbo,  "Bistatic-Radar  Methods  for  Studying  Planetary  Ionospheres  and  Surfaces,"  Ph.D.  diss., 
Stanford  University,  1964,  especially  pp.  64-82.  Later  published  as  Fjeldbo,  Bistatic-Radar  Methods  for  Studying 
Planetary  Ionospheres  and  Surfaces,  SR  2  (Stanford:  RLSEL,  1964). 


1 56  TO  SEE  THE  UNSEEN 


and  obtained  crude  meter-scale  measurements  of  surface  roughness  and  radar  bright- 
ness.26 With  Simpson,  Tyler  performed  bistatic  radar  experiments  on  the  Moon  using  the 
Apollo  14, 15  (at  13  and  116  cm),  and  16  (at  13  cm  only)  command  service  modules  while 
those  vehicles  were  in  lunar  orbit;  at  the  same  time,  they  were  receiving  the  S-band  (13 
cm)  signals  at  Goldstone  and  the  VHF  (116  cm)  signals  at  the  Stanford  46-meter  (150-ft) 
dish.  However,  Tyler  and  Simpson  did  not  do  imaging;  they  were  more  concerned  with 
scattering  mechanisms.27 

Mars  Radar 

Tyler  and  Simpson  began  working  on  the  Viking  landing  site  selection  problem  by 
surveying  and  re-analyzing  the  available  data.  Radar  data  from  several  oppositions  already 
were  available,  and  those  data  obtained  during  the  1965  opposition  were  from  the  latitude 
of  the  preferred  Viking  landing  sites,  around  20°  North.  Radar  studies  of  Mars  made  dur- 
ing the  1969  opposition  provided  useful  topographical  and  surface  roughness  measure- 
ments, though  not  at  latitudes  interesting  to  the  Viking  mission.  Haystack  observed  a 
swath  of  the  planet's  surface  near  the  equator  (latitudes  3°  and  12°  North),  while 
Goldstone  took  observations  at  three  latitudes  (3°,  11°,  and  12°  North).28 


26.  Tyler  10  May  1994;  Tyler,  The  Bistatic  Continuous-Wave  Radar  Method  for  the  Study  of  Planetary  Surfaces, 
SU-SELr65-096,  Scientific  Report  13  (Stanford:  RLSEL,  October  1965),  which  later  appeared  as  Tyler,  The 
Bistatic,  Continuous-Wave  Radar  Method  for  the  Study  of  Planetary  Surfaces,  "Journal  of  Geophysical  Research  71 
(1966):  1559-1567;  Tyler,  Bistatic-Radar  Imaging  and  Measurement  Techniques  for  the  Study  of  Planetary  Surfaces,  SU- 
SEL-67-042,  Scientific  Report  19  (Stanford:  RLSEL,  May  1967);  Tyler  and  Simpson,  Bistatic-Radar  Studies  of  the 
Moon  with  Explorer  35:  Final  Report  Part  2,  SR  3610-2,  SU-SEL-70-068  (Stanford:  RLSEL,  October  1970) ;  Tyler  and 
Simpson,  "Bistatic  Radar  Measurements  of  Topographic  Variations  in  Lunar  Surface  Slopes  with  Explorer  35," 
Radio  Science 5  (1970):  263-271;  SCRA,  Proposal  to  the  National  Aeronautics  and  Space  Administration  for  Bistatic  Radar 
Astronomy  Studies  of  the  Surface  and  Ionosphere  of  the  Moon  based  upon  Transmission  from  the  Earth  and  Reception  in  a 
Surveyor  Orbiter,  Proposal  RL  21-62  (Stanford:  RLSEL,  7  September  1962),  Eshleman  materials. 

27.  Tyler  10  May  1994;  Simpson  10  May  1994;  Simpson  and  Tyler,  "Radar  Scattering  Laws  for  the  Lunar 
Surface,"  IEEE  Transactions  on  Antennas  and  Propagation  AP-30  (1982):  438-449;  Simpson,  "Lunar  Radar  Echoes: 
An  Interpretation  Emphasizing  Characteristics  of  the  Leading  Edge,"  Ph.D.  diss.,  Stanford  University,  1973. 

28.  Tyler  10  May  1994;  Rogers,  Ash,  Counselman,  Shapiro,  and  Pettengill,  "Radar  Measurements  of 
Surface  Topography  and  Roughness  of  Mars,"  Radio  Science  5  (1970):  465-473;  Goldstein,  Melbourne,  Morris, 
George  S.  Downs,  and  O'Handley,  "Preliminary  Radar  Results  of  Mars,"  Radio  Science  5  (1970):  475-478. 


PIONEERING  ON  VENUS  AND  MARS 


157 


Figure  25 

Outline  of  Mars  topography  at  8°  north  of  the  equator  released  byJPL  in  July  1969.  The  outer  white  circle  indicates  a  six-mile- 
high  scale.  The  inner  irregular  line  traces  topographical  variations  found  by  radar.  Syrtis  Major  and  Trivium  Charontis  were 
found  to  be.  long  slopes.  The  correlation  of  radar  topographic  data  with  known  features  in  Mars  photographic  images  aided 
geologists '  ability  to  interpret  the  physical  and  historical  geology  of  the  planet.  (Courtesy  of  Jet  Propulsion  Laboratory,  photo 
no.  331-4539.) 

The  1969  and  earlier  data,  moreover,  were  too  noisy  to  be  of  any  use  in  sorting  out 
a  Viking  landing  site.  The  best  data  had  been  collected  during  the  1971  opposition,  when 
Mars  came  closer  to  Earth  than  it  would  again  for  17  years.  Goldstone  achieved  its  high- 
est resolutions  to  date;  results  showed  a  rugged  terrain,  with  elevation  differences  greater 
than  13  km  from  peak  to  valley.  Altitude  profiles  showed  heavy  cratering,  including 
several  large  craters  50  to  100  km  in  diameter  and  1  to  2  km  deep.  Haystack  also  made 
high-resolution  Mars  radar  observations  during  the  1971  opposition,  measured  surface 
heights  with  relative  errors  down  to  about  75  meters,  and  correlated  craters  detected  by 
radar  with  those  in  images  taken  by  Mariner.29 


29.  Goldstein  14  September  1993;  Downs,  Goldstein,  R.  Green,  Morris,  "Mars  Radar  Observations,  A 
Preliminary  Report,"  Science  174  (1971):  1324-1327;  Downs,  Goldstein,  R.  Green,  Morris,  and  Reichley,  "Martian 
Topography  and  Surface  Properties  as  Seen  by  Radar:  The  1971  Opposition,"  Icarus  18  (1973):  8-21;  Pettengill, 
Shapiro,  and  Rogers,  Topography  and  Radar  Scattering  Properties  of  Mars,"  Icarus  18  (1973):  22-28;  Pettengill, 
Rogers,  and  Shapiro,  "Martian  Craters  and  a  Scarp  as  Seen  by  Radar,"  Science  174  (1971):  1321-1324. 


1 58  TO  SEE  THE  UNSEEN 


Nonetheless,  even  that  high-resolution  data  was  not  useful  to  the  selection  of  a 
Viking  landing  site.  Because  of  the  geometries  of  the  Earth  and  Mars  during  that  opposi- 
tion, planetary  radar  astronomers  observed  the  southern  hemisphere  of  the  planet.  The 
Goldstone  radar  observed  Mars  at  latitude  16°  South.  Haystack  observations  during  the 
1971  opposition  also  examined  southern  latitudes.30  The  best  candidates  for  the  Viking 
mission  were  in  the  northern  hemisphere. 

Thus,  in  1973,  when  Tyler  undertook  the  interpretation  of  Mars  radar  data  for  the 
selection  of  the  Viking  landing  sites,  radars  had  not  observed  the  preferred  Viking  land- 
ing area  near  20°  North  since  1967,  nor  any  of  the  backup  sites  near  the  equator  prior  to 
1975.  The  Viking  Project  Office  funded  a  round  of  Mars  radar  observations  in  1973  at  the 
Haystack,  Arecibo,  and  Goldstone  radar  telescopes  at  UHF,  S-band,  and  X-band  frequen- 
cies. Don  Campbell  and  Rolf  Dyce  provided  the  Arecibo  data,  while  Dick  Goldstein  and 
George  Downs  took  the  Goldstone  data,  and  Gordon  Pettengill  furnished  the  Haystack 
data.31 

The  1973  Haystack  Mars  data  was  placed  in  the  same  format  as  that  obtained  at 
Arecibo  in  order  to  facilitate  their  comparison.  Although  Haystack  provided  an  abun- 
dance of  radar  data,  its  signal-to-noise  ratio  was  generally  too  low  for  a  detailed  study  of 
surface  characteristics.  The  Haystack  klystron  was  acting  up,32  and  Haystack  ceased  to  par- 
ticipate in  the  Viking  mission;  shortly  thereafter  Haystack  stopped  all  planetary  radar 
experiments. 

The  1973  Viking  Mars  data  provided  no  direct  information  on  potential  landing 
sites.  The  orbital  geometries  of  Earth  and  Mars  meant  that  the  subradar  points  of  the 
three  telescopes  swept  areas  in  the  southern  hemisphere,  between  latitudes  14°  and  22° 
South  far  from  either  the  main  or  backup  landing  sites.33  The  1973  data,  nonetheless,  pro- 
vided an  opportunity  to  better  understand  the  radar  properties  of  the  Martian  surface  and 
for  Tyler,  in  particular,  to  begin  the  difficult  task  of  explaining  the  surface  roughness  of 
Mars  in  terms  of  root-mean-square  (rms)  slope  to  an  audience  unacquainted  with  the 
interpretation  of  radar  data. 

Radar  Tutorials 

Mariner  images  made  the  surface  of  Mars  obvious  to  everyone.  Radar  data  on  sur- 
face roughness  was  not  at  all  obvious  and  required  expert  interpretation.  The  "rift 
between  believers  in  radar  and  believers  in  photography,"  in  the  words  of  Edward  Clinton 
Ezell  and  Linda  Neuman  Ezell,  first  appeared  at  a  meeting  of  the  Viking  landing  site  work- 
ing group  on  25  April  1972,34  well  before  Tyler  and  radar  became  a  part  of  the  site  selec- 
tion process. 


30.  Pettengill,  Shapiro,  and  Rogers,  "Topography  and  Radar  Scattering  Properties  of  Mars,"  Icarus  18 
(1973):  22-28;  Pettengill,  Rogers,  and  Shapiro,  "Martian  Craters  and  a  Scarp,"  pp.  1321-1324. 

31.  Simpson,  Tyler,  and  Belinda].  Lipa,  Analysis  of  Radar  Data  from  Mars,  SR  3276-1,  SU-SEL-74-047 
(Stanford:  SCRA,  October  1974). 

32.  Ingalls  5  May  1994;  Simpson  10  May  1994. 

33.  Memorandum,  Sebring  to  Distribution,  9  December  1970,  44/2/AC  135;  "Applications  of  High 
Power  Radar  to  Studies  of  the  Planets,  NASA,  7/1/69-  6/30/70,"  67/2/AC  135;  "Radar  Studies  of  the  Planets, 
NASA,  7/1/72-6/30/73,"  68/2/AC  135,  MITA;  NEROC,  Final  Progress  Report  Radar  Studies  of  the  Planets,  29  August 
1974,  pp.  1-2;  NEROC,  Semiannual  Report  of  the  Haystack  Observatory,  15  July  1972,  p.  ii;  Simpson,  Tyler,  and  Lipa, 
"Mars  Surface  Properties  Observed  by  Earth-Based  Radar  at  70-,  12.5-,  and  3.8-cm  Wavelengths,"  Icarus  32 
(1977):  148.  For  the  radar  results  themselves,  see  Pettengill,  John  F.  Chandler,  Campbell,  Dyce,  and  D.  M. 
Wallace,  "Martian  Surface  Properties  from  Recent  Radar  Observations,"  Bulletin  of  the  American  Astronomical 
Society  6  (1974):  372;  Downs,  Goldstein,  R.  Green,  Morris,  and  Reichley,  "Martian  Topography  and  Surface 
Properties  as  Seen  by  Radar:  The  1973  Opposition,"  Icarus  18  (1973):  8-21;  Downs,  Reichley,  and  R.  Green, 
"Radar  Measurements  of  Martian  Topography  and  Surface  Properties:  The  1971  and  1973  Oppositions,"  Icarus 
26  (1975):  273-312. 

34.  Ezell  and  Ezell,  p.  298. 


PIONEERING  ON  VENUS  AND  MARS  159 


The  key  radar  information  on  surface  characteristics  was  not  expressed  visually,  but 
mathematically.  The  abstract  results  were  neither  visual  nor  directly  accessible  by  any  of 
the  senses.  Moreover,  the  transformation  of  raw  radar  data  into  information  on  surface 
characteristics  involved  the  interpretation  of  the  data  in  terms  of  scattering  laws  and  their 
expression  as  degrees  of  rms  slope.  The  number  of  degrees  of  rms  slope  indirectly  but  reli- 
ably described  the  planet's  surface  roughness. 

When  a  radar  wave  strikes  an  irregular  planetary  surface  covered  by  boulders  or 
other  material  with  multiple  sides,  a  complex  scattering  process  takes  place.  Some  power 
returns  to  the  radar,  some  power  is  deflected  away  from  the  radar  return  path,  while  some 
power  scatters  among  the  boulders.  The  rougher  the  surface,  the  less  power  returns  to  the 
radar  and  the  flatter  is  the  return  power  spectra. 

Because  each  radar  target  has  a  different  surface  makeup,  its  scattering  behavior 
varies.  Radar  astronomers  have  sought  general  laws  that  describe  scattering  behavior. 
These  scattering  laws  are  mathematical  descriptions  of  how  much  power  is  reflected  back 
towards  the  radar  at  different  angles  of  incidence.  They  are  important  tools  for  interpret- 
ing planetary  radar  data.  At  Haystack  and  Arecibo,  radar  investigators  used  what  had 
become  known  as  the  "Hagfors  Law,"  named  after  the  Cornell  University  ionosphericist 
and  radar  astronomer. 

The  Hagfors  Law  mathematically  expresses  the  general  roughness  of  a  planetary  or 
lunar  surface  in  terms  of  average  slope.  The  root-mean-square  is  a  specific  type  of  math- 
ematical average  for  the  expression  of  these  average  slopes.  When  using  the  Hagfors  Law, 
the  value  for  the  slope  varies  up  to  3°,  the  upper  theoretical  limit  for  the  validity  of  the 
assumptions  underlying  the  Hagfors  Law,  although  in  practice  much  higher  slope  values 
are  normal.  The  1973  slope  estimates  for  Mars  ranged  from  0.5°  to  at  least  3°,  suggesting 
that  some  areas,  those  closest  to  0.5°,  were  suitable  for  a  Viking  landing.  However,  none 
of  the  1973  radar  experiments  had  observed  areas  of  potential  Viking  landing  sites.35 

Tyler  and  the  members  of  his  radar  study  group  presented  their  results  to  the  land- 
ing site  working  group  meeting  at  Langley  on  4  November  1974.  Tyler  announced  that  his 
study  group  had  learned  a  great  deal:  overall,  the  Martian  surface  was  very  heterogeneous; 
Mars  tended  to  have  greater  variation  in  surface  reflectivity  than  Earth  or  the  Moon;  and 
the  planet  appeared  smoother  than  the  Moon  to  the  radar.  However,  he  concluded,  data 
acquired  in  the  southern  hemisphere  could  not  be  applied  to  northern  latitudes  without 
variation.  Also,  correlation  between  radar  features  and  Mariner  9  imagery  was  poor. 

Both  Tyler  and  Gordon  Pettengill  "laced  their  presentations  strongly  with  tutorial 
material  which  greatly  enhanced  the  ability  of  the  group  to  understand  and  correctly 
interpret  their  findings,"  reported  Edward  and  Linda  Ezell.36  After  all,  geologists  would 
rather  think  about  rocks  than  about  Hagfors'  Law,  rms  slopes,  or  dielectric  constants,  and 
those  in  charge  of  making  the  landing  site  selection  had  no  knowledge  of  radar.37  The 
abstract  nature  of  the  radar  data,  as  well  as  its  complex  and  difficult  interpretation,  had 
an  impact  on  the  actual  use  of  radar  in  the  selection  of  the  Viking  landing  site. 


35.  Simpson,  Tyler,  and  Lipa,  "Mars  Surface  Properties  Observed  by  Earth-Based  Radar  at  70-,  12.5-,  and 
3.8-cm  Wavelengths,"  /cams  32  (1977):  156. 

36.  Ezell  and  Ezell,  p.  322. 

37.  Simpson  10  May  1994;  Schaber  27  June  1994;  Shoemaker  30  June  1994;  Soderblom  26  June  1994; 
Gold  14  December  1993. 


160 


TO  SEE  THE  UNSEEN 


Figure  26 

The  radar  data  used  to  help  select  candidate  landing  sites  for  Viking  often  were  expressed  in  degrees  ofrms  slope.  This  illus- 
tration depicts  the  abstract  nature  of  that  radar  data.  Above,  (e)  is  the  rms  slope  derived  from  the  roughness  data  obtained  near 
latitude  -16°  and  shown  in  (b).  (a)  through  (c)  were  obtained  by  fitting  the  Hagfors  scattering  law  to  measured  angular  power 
spectra,  while  (d)  was  surface  reflectivity  derived  from  data  in  (a)  and  (b).  (Courtesy  of  Jet  Propulsion  Laboratory.) 


The  Landing  Site 


The  selection  of  the  final  landing  site  of  Viking  1  was  a  long,  tedious,  and  dramatic 
process.38  The  sites  under  consideration  at  the  last  minute,  literally  during  the  two  weeks 
that  Viking  orbited  Mars,  all  had  been  either  observed  by  radar  or  photographed.  Part  of 
the  problem  was  the  lack  of  overlap  between  the  radar  and  optical  data.  Areas  with  good 
radar  data  had  poor  photographic  documentation,  while  sites  with  good  photographic 
views  had  poor  radar  data.  Everybody  wanted  a  safe  landing;  nobody  wanted  to  take  a 
chance  with  a  site  confirmed  by  only  radar  or  only  photographs.  The  indecision  foiled  an 
earlier  interest  in  landing  Viking  on  the  Fourth  of  July  in  honor  of  the  country's  bicen- 
tennial. 

In  order  to  acquire  additional  information  on  the  candidate  landing  sites,  the  Viking 
Project  Office  commissioned  another  round  of  radar  observations  by  Goldstone  and 
Arecibo.  Observing  conditions  were  not  ideal,  because  Earth  and  Mars  were  not  in  oppo- 
sition. However,  the  Arecibo  S-band  (2380  MHz;  13  cm)  400-kilowatt  radar  had  just  come 
on  line,  and  Tyler  recommended  making  additional  Arecibo  observations  with  it.  Earlier 
Mars  radar  studies  had  been  conducted  only  when  Mars-Earth  distances  were  less  than 
one  astronomical  unit.  Signal  strengths  during  the  August  1975-February  1976  equatori- 
al observations  were  good,  but  the  Earth-Mars  distance  reached  2  astronomical  units  in 
May:July  1976.39 


38.  For  a  full  discussion,  see  Ezell  and  Ezell,  pp.  317-346,  as  well  as  Downs  4  October  1994. 

39.  Simpson,  Tyler,  and  Lipa,  Analysis  of  Radar  Data  from  Mars;  Simpson,  Tyler,  and  Campbell,  "Arecibo 
Radar  Observations  of  Mars  Surface  Characteristics  in  the  Northern  Hemisphere,"  Icarus  36  (1978):  156-157. 


PIONEERING  ON  VENUS  AND  MARS  161 


Arecibo  observed  Mars  between  August  1975  and  July  1976  over  the  latitudes 
between  12°  South  and  24°  North.  The  results  between  12°  South  and  4°  North  were  rel- 
evant to  potential  alternate  (i.e.,  backup)  Viking  sites.  Between  October  1975  and  April 
1976,  Goldstone  observed  the  two  regions  Syrtis  Major  and  Sinus  Meridiani,  particularly 
a  number  of  proposed  Viking  landing  sites,  including  the  prime  site  (called  Al)  near  lon- 
gitude 34°  and  latitude  19.5°  North.  As  a  result  of  the  radar  data,  the  Al  site  was  rejected 
on  26  June  1976,  while  other  sites  came  under  consideration.40 

Simpson,  Tyler,  and  Campbell  made  additional  Arecibo  observations  for  the  Viking 
Project  Office  near  20°  North  latitude,  the  latitude  of  the  landing  site,  particularly  the 
Viking  Chryse  and  Tritonis  Lacus  (the  A2  site,  first  alternate  to  Al)  landing  areas.  The 
search  for  a  suitable  site  then  moved  toward  the  northwest  where  a  region  designated 
A1NW  was  tentatively  selected  because  of  its  apparent  smoothness  as  seen  from  orbit.  The 
A1NW  site  was  finally  abandoned  because  of  its  questionable  radar  properties.  It  was 
toward  the  west  that  the  Viking  site  selection  and  certification  teams  moved  after  turning 
down  A1NW.41 


Did  Radar  Help? 


Had  radar  observations  and  expressions  of  rms  slope  actually  helped  in  the  selection 
of  the  final  Viking  1  landing  site?  Certainly,  Tyler's  reports  to  the  landing  site  working 
group  did  not  go  totally  unheeded,  and  radar  turned  down  some  potential  but  suspect 
landing  sites.  As  NASA  official  John  E.  Naugle  wrote  in  November  1976,  'The  choice  of 
the  actual  landing  site  was  eventually  based  on  a  combination  of  the  S-band  [Arecibo] 
radar  data  and  high  resolution  photography  obtained  from  the  Viking  1  Orbiter."42 
However,  not  everyone  was  as  diplomatic  as  Naugle;  some  doubted  the  utility  of  the  radar 
data. 

Tom  Young,  Viking  science  integration  manager,  believed  that  radar  data  eventually 
played  a  role,  although  when  the  project  selected  initial  landing  site  candidates,  he  admit- 
ted that,  "radar  played  no  role,  because  we  weren't  smart  enough  to  know  how  to  use  it." 
On  the  other  hand,  James  Martin,  Viking  Project  Manager,  remained  skeptical  about  the 
utility  of  the  radar  data.  Radar  provided  no  useful  information,  he  felt,  although  it  was  "an 
input  and  a  source  of  information  that  [we]  could  not  ignore."  Frankly,  he  admitted,  'The 
fact  that  it  [radar]  was  so  different  scared  me  off."43 

It  was  that  difference,  the  general  unfamiliarity  with  radar  data,  that  raised  a  barrier 
to  the  use  of  radar  results.  "People  didn't  quite  know  what  to  make  of  us,"  Tyler  explained. 
"People  were  willing  to  listen,  but  it  was  clear  that  they  didn't  like  the  answer!"  Farther  to 
the  cynical  side  was  the  judgement  of  Dick  Simpson:  "I've  always  said  that  the  radar  con- 
tribution to  picking  landing  sites  on  Mars  probably  came  out  with  a  net  result  of  zero.. ..If 
we'd  never  been  involved,  they  probably  would  have  had  the  same  end  result,  but  we  got 
to  play  in  the  game  and  sometimes  that's  part  of  it."  George  Downs,  who  analyzed  the 
Mars  radar  data  at  JPL,  was  convinced  that  project  personnel  simply  looked  for  a  site  as 
Viking  1  orbited  Mars,  ignoring  the  radar  data  entirely.  The  attitude  of  many,  he  felt,  was 
that  the  radar  astronomers  were  getting  their  answers  as  if  from  a  ouija  board.44 


40.  Simpson,  Tyler,  and  Campbell,  "Arecibo  Radar  Observations  of  Martian  Surface  Characteristics 
Near  the  Equator,"  Icarus  33  (1978):  102-115;  Downs,  R.  Green,  and  Reichley,  "Radar  Studies  of  the  Martian 
Surface  at  Centimeter  Wavelengths:  The  1975  Opposition,"  Icarus  33  (1978):  441-453. 

41.  Simpson,  Tyler,  and  Campbell,  "Mars  Surface  Characteristics  in  the  Northern  Hemisphere," 
pp. 153-173. 

42.  John  E.  Naugle  to  H.  Guyford  Stever,  8  November  1976,  NHOB. 

43.  Ezell  and  Ezell,  p.  357. 

44.  Tyler  10  May  1994;  Simpson  10  May  1994;  Downs  4  October  1994. 


1 62  TO  SEE  THE  UNSEEN 


The  radar  data  presented  was  indeed  quite  different;  it  was  degrees  of  rms  slope, 
rather  than  images  universally  understood.  Perhaps  if  range-Doppler  mapping  of  Mars 
had  been  possible,  the  difference  would  not  have  been  so  great.  Still,  the  episode  illus- 
trated the  kinds  of  challenges  that  radar  astronomers  would  have  to  confront  as  they 
played  an  increasing  role  in  planetary  exploration  and  sought  to  share  their  results  with 
scientists  who  lacked  an  understanding  of  radar.  It  was  simply  not  enough  to  meet  with 
planetary  geologists  and  other  scientists;  radar  astronomers  had  to  communicate  their 
results  in  a  way  understandable  by  other  scientists. 

The  availability  of  the  Mars  radar  data  at  JPL  was  the  catalyst  for  the  kind  of  inter- 
disciplinary communication  and  collaboration  that  interpreting  the  radar  results 
demanded.  George  Downs  struck  up  an  alliance  with  Ladislav  Roth  at  JPL  and  Gerald 
Schubert  at  UCLA.  Roth  and  Schubert  saw  value  in  the  radar  data;  that  is,  the  topo- 
graphical information,  not  the  surface  roughness  measurements.  Roth,  in  fact,  had 
approached  Downs  to  collaborate  in  interpreting  the  radar  topographical  data,  and  sev- 
eral studies  grew  out  of  that  collaboration.45 


A  Venus  Radar  Mapper? 


Concurrently  with  Viking  preparations,  NASA  planned  a  mission  to  Venus.  Pioneer 
Venus  marked  a  significant  departure  for  radar  astronomy.  Don  Campbell  and  Tor 
Hagfors  had  distinguished  planetary  radar  astronomy  from  space  exploration,  in  particu- 
lar, the  bistatic  radar  work  done  at  Stanford  University.  Pioneer  Venus  challenged  that  dis- 
tinction; it  was  no  longer  ground-based  planetary  radar  astronomy,  and  it  marked  a  sig- 
nificant entree  into  a  new  area  of  Big  Science. 

Instead  of  Big  Science  providing  a  large,  Earth-based  dish,  like  the  Arecibo  radar, 
spacecraft  missions  furnished  the  opportunity,  but  not  the  hardware,  to  do  planetary 
radar  astronomy  from  a  point  just  above  the  target,  not  millions  of  kilometers  away.  Like 
piggybacking  radar  astronomy  onto  an  Earth-based  facility,  placing  a  radar  experiment 
and  its  necessary  hardware  on  a  spacecraft  demanded  participating  in  the  politics  of  Big 
Science.  Radar  astronomy  aboard  Pioneer  Venus  remained  Little  Science,  though,  con- 
ducted by  a  single  investigator,  Gordon  Pettengill,  who  carried  out  the  entrepreneurial 
burden  of  placing  the  radar  instrument  on  the  spacecraft  and  who  brought  fellow  ground- 
based  radar  astronomers  into  the  project  as  analyzers  of  the  radar  data. 

Pioneer  Venus  also  facilitated  the  shift  of  planetary  radar  toward  serving  the  plane- 
tary geology  community.  Within  the  working  groups  established  by  NASA  space  missions, 
planetary  radar  astronomers  and  planetary  geologists  worked  together.  Behind  this  shift, 
too,  was  the  ability  of  radar  astronomers  to  solve  problems  of  interest  to  geologists.  If  plan- 
etary radar  astronomy  had  focused  solely  on  refining  planetary  orbital  parameters,  the 
prime  users  of  planetary  radar  results  would  have  remained  astronomers.  Radar 
techniques  that  described  planetary  surfaces,  in  contrast,  solved  problems  of  interest  to 
geologists,  especially  those  geologists  at  the  United  States  Geological  Survey  (USGS)  inter- 
ested in  planetary  geology,  or  what  the  USGS  called  astrogeology.  The  shift  to  geology  was 
an  educational  experience  for  both  geologists  and  radar  investigators,  and  it  eventually 
manifested  itself  in  the  journals  and  professional  societies  attended  by  planetary  radar 
astronomers  and  culminated  in  the  Magellan  mission  to  Venus. 

The  idea  of  using  radar  to  image  Venus  from  a  probe  predated  the  Pioneer  Venus 
project.  The  official  history  of  Pioneer  Venus  dates  the  beginning  of  the  project  to 


45.  Downs  4  October  1994;  Ladislav  E.  Roth,  Downs,  Saunders,  and  Gerald  Schubert,  "Radar  Altimetry 
of  South  Tharsis,  Mars,"  Icarus  42  (1980):  287-316;  Roth,  Saunders,  Downs,  and  Schubert,  "Radar  Altimetry  of 
Large  Martian  Craters,"  Icarus  79  (1989):  289-310. 


PIONEERING  ON  VENUS  AND  MARS  1 63 


October  1967,  shortly  after  the  Venera  4  and  Mariner  5  spacecraft  visited  Venus.  Three 
scientists,  Richard  M.  Goody  (Harvard  University),  Donald  M.  Hun  ten  (University  of 
Arizona;  Kitt  Peak  National  Observatory),  and  Nelson  W.  Spencer  (Goddard  Space  Flight 
Center)  formed  a  group  to  consider  the  feasibility  of  exploring  the  Cytherean  atmosphere 
from  a  spacecraft.  The  group's  formation  led  to  a  study  published  in  January  1969  by  the 
Goddard  Space  Flight  Center.46 

The  idea  of  mapping  Venus  with  a  radar  started  much  earlier.  As  early  as  1959,  NASA 
contracted  with  the  University  of  Michigan  to  design  a  Venus  radar.  In  1961 ,  NASA  let  out 
three  more  grants  and  contracts  to  develop  radars  for  a  future  Venus  mission  to  map  the 
planet's  surface  to  investigators  at  the  University  of  New  Mexico,  MIT,  and  Ohio  State.47 
In  1961,  for  example,  NASA  funded  a  study  under  J.  F.  Reintjes,  Director  of  MIT's 
Electronics  Systems  Laboratory,  "to  perform  an  investigation  of  radar  techniques  and 
devices  suitable  for  the  exploration  of  the  planet  Venus."  NASA  awarded  the  funds 
because  the  space  agency  saw  radar  as  an  attractive  technique  for  exploring  the  surface  of 
Venus  and  as  "a  logical  experiment  for  a  Venus  flyby  or  orbiter." 

Developing  a  radar  system  appropriate  for  space  travel  presented  numerous  prob- 
lems. The  equipment  had  to  meet  certain  weight,  space,  and  reliability  criteria.  The  MIT 
goal  was  to  design  and  build  a  space  radar  that  required  fewer  than  100  watts  and  weighed 
no  more  than  50  pounds.  After  completion  of  an  engineering  model  by  Reintjes  and  the 
MIT  Electronics  Systems  Laboratory,  in  October  1967,  tests  aboard  an  aircraft,  the 
Convair  CV-990  owned  by  NASA  Ames  Research  Center,  began.48 

Throughout  the  1960s,  then,  and  well  before  the  formation  of  the  Goddard  study 
group  in  1967,  the  idea  of  imaging  Venus  with  a  spacecraft-borne  radar  was  already  "in  the 
air."  But  before  a  spacecraft  could  carry  a  radar  to  Venus,  NASA  had  to  formulate  and 
fund  a  voyage  of  exploration  to  the  planet.  In  June  1968,  a  Space  Science  Board  study  on 
planetary  exploration  urged  NASA  to  send  a  space  probe  to  Venus,  though  without  rec- 
ommending inclusion  of  a  radar  experiment.49  By  June  1970,  the  NASA  program  of  plan- 
etary exploration  still  contained  no  significant  Venus  missions.  The  planned  flyby  of  Venus 
and  Mercury  was  essentially  a  Mercury  mission  with  only  a  small  contribution  to  Venus 
science.  In  contrast,  NASA  had  a  robust  plan  for  exploring  Mars  and  an  ambitious 
program  for  investigating  the  outer  planets.50 

In  June  1970,  to  address  the  lack  of  a  serious  Venus  mission,  the  NASA  Lunar  and 
Planetary  Missions  Board  and  the  Space  Science  Board  brought  together  21  scientists  to 
study  the  scientific  potential  of  a  mission  to  Venus  (Table  3).  Richard  Goody  and  Donald 
M.  Hunten,  who  had  helped  start  the  Goddard  study,  co-chaired  the  meeting.  Their 
report,  known  as  the  Purple  Book  because  of  the  color  of  its  cover,  recommended  that 
exploration  of  Venus  should  be  prominent  in  the  NASA  program  for  the  1970s  and  1980s. 
The  group  presented  its  recommendations  to  NASA  management,  and  the  Space  Science 
Board  endorsed  them.51 

Significantly,  the  Purple  Book  study  brought  together  a  planetary  radar  astronomer, 
Gordon  Pettengill,  then  Director  of  the  Arecibo  Ionospheric  Observatory,  and  a  planetary 
geologist,  Harold  Masursky  of  the  USGS.  Pettengill's  participation  in  the  Purple  Book 


46.  Richard  O.  Fimmel,  Lawrence  Colin,  and  Eric  Burgess,  Pioneer  Venus,  NASA  SP-461  (Washington: 
NASA,  1983),  pp.  14-15;  Colin,  The  Pioneer  Venus  Program, "  Journal  of  Geophysical  Research  85  (1980):  7575. 

47.  Tatarewicz,  pp.  150-151. 

48.  Memorandum,  Oran  W.  Nicks,  10  March  1966,  and  Memorandum,  Brunk,  29  November  1966, 
NHOB;  J.  F.  Reintjes  and  J.  R.  Sandison,   Venus  Radar  Systems  Investigations  Final  Report  (Cambridge:  MIT, 
Electronic  Systems  Laboratory,  Department  of  Electrical  Engineering,  March  1970),  Pettengill  materials. 

49.  Space  Science  Board,  Planetary  Exploration,  1968-1975  (Washington:  National  Academy  of  Sciences, 
1968). 

50.  Space  Science  Board,  Venus:  Strategy  for  Exploration  (Washington:  National  Academy  of  Sciences,  June 
1970),  p.  3. 

51.  C.  H.  Townes,  Preface,  Space  Science  Board,  Venus:  Strategy  for  Exploration,  n.p. 


164 


TO  SEE  THE  UNSEEN 


Table  3 

Purple  Book  Scientists 

Scientist 

Institution 

Richard  M.  Goody,  Chair 

Harvard  University 

Donald  M.  Hunten 

Kitt  Peak  National  Observatory 

Don  L.  Anderson 

California  Institute  of  Technology 

W.  Ian  Axford 

University  of  California,  San  Diego 

Alan  H.  Barrett 
Leverett  Davis,  Jr. 

Massachusetts  Institute  of  Technology 
California  Institute  of  Technology 

Thomas  M.  Donahue 
John  C.  Gille 

University  of  Pittsburgh 
Florida  State  University 

Seymour  Hess 

Florida  State  University 

Garry  E.  Hunt 

Atlas  Computer  Laboratory 

Robert  G.  Knollenberg 

University  of  Chicago 

John  S.  Lewis 

Massachusetts  Institute  of  Technology 

Michael  B.  McElroy 

Kitt  Peak  National  Observatory 

Gordon  H.  Pettengill 

Arecibo  Ionospheric  Observatory 

Robert  A.  Phinney 

Princeton  University 

S.  Keith  Runcorn 

University  of  Newcastle 

Verner  E.  Suomi 

University  of  Wisconsin 

Patrick  Thaddeus 

Columbia  University 

G.  Leonard  Tyler 

Stanford  University 

James  A.  Weiman 

University  of  Wisconsin 

George  W.  Wetherill 

University  of  California,  Los  Angeles 

study  marked  his  initial  involvement  in  Pioneer  Venus.52  By  then,  Pettengill,  the  future 
Professor  of  Planetary  Physics  in  the  MIT  Earth  and  Planetary  Sciences  Department,  had 
acquired  stature  in  his  field,  having  been  one  of  the  radar  astronomy  pioneers  at  Lincoln 
Laboratory,  but  also  as  Associate  Director,  then  as  Director,  of  the  prestigious  Arecibo 
Observatory. 

Masursky  had  joined  the  USGS  after  graduating  from  Yale  in  1947.  After  a  number 
of  years  as  a  general  geologist,  Masursky  joined  the  USGS's  Branch  of  Astrogeologic 
Studies.  In  1967,  he  became  chief  of  the  astrogeology  branch,  then  starting  in  1971  and 
until  his  death,  chief  scientist  of  that  branch.  Masursky  was  a  science  investigator  on 
almost  every  NASA  flight  project  to  the  Moon  and  the  planets,  including  the  Ranger, 
Lunar  Orbiter,  Surveyor,  Apollo,  Mariner  9,  and  Viking  missions.53 

The  Purple  Book  meeting  thus  was  a  first  step  in  planetary  radar's  shift  toward  geol- 
ogy, providing  an  initial  setting  for  planetary  radar  and  geology  to  interact  and  to  devel- 
op a  common  approach  for  the  study  of  Venus's  surface,  within  the  broader  context  of 
NASA-sponsored  research  of  the  planet's  atmosphere.  As  the  Purple  Book  itself  noted,  the 
space  missions  of  the  1960s  had  given  rise  to  new  fields  of  study:  "Very  rapidly  studies  of 
planetary  meteorology,  planetary  aeronomy,  planetology,  and  planetary  biology  emerged 
which  involved,  in  the  main,  research  workers  from  the  parallel  terrestrial  disciplines. 
Earth  and  planetary  studies  suddenly  merged  and  simultaneously  diverged  from  astrono- 
my. In  some  major  universities,  departmental  and  research  center  organization  was 
changed  to  meet  this  development."54 

Images  sent  back  from  space  had  encouraged  geologists,  like  Hal  Masursky,  to 
become  interested  in  planetary  surfaces  and  in  the  processes  that  shaped  them.  However, 
ground-based  radar  images  of  Venus  had  yet  to  find  their  audience  among  planetary  geol- 
ogists.55 


52.  Pettengill  28  September  1993. 

53.  V-Gram  no.  12  (July  1987):  15;  "Harold  Masursky,"  in  R.  R.  Bowker,  comp.,  American  Men  and  Women 
of  Science,  18th  edition  (New  Providence,  NJ:  R.  R.  Bowker,  1992),  vol.  5,  p.  275. 

54.  Space  Science  Board,  Venus:  Strategy  for  Exploration,  p.  4. 

55.  Campbell  9  December  1993. 


PIONEERING  ON  VENUS  AND  MARS  1 65 


As  far  as  ground-based  planetary  radar  was  concerned,  the  Purple  Book  applauded 
its  success.  "Virtually  all  our  present  knowledge  of  the  radius,  rotation,  and  surface  of 
Venus  has  been  obtained  using  ground-based  radars,"  the  Purple  Book  proclaimed.  With 
resolutions  ranging  from  100  to  500  km,  radar  had  revealed  features,  and  even  the  lack  of 
topographic  relief,  in  the  equatorial  region  of  Venus.  Including  a  radar  system  on  a  Venus 
probe  would  yield  "maps  similar  in  appearance  and  usefulness  to  photographic  maps  of 
the  same  region." 

Ironically,  the  Purple  Book  cautioned  against  imaging  Venus  with  a  spacecraft  radar. 
It  pointed  out  that  such  radar  images  would  be  "directly  competitive  with  ground-based 
observations  and  would  provide  similar  data."  That  point  resurfaced  later  during  plan- 
ning for  Magellan.  Although  a  spaceborne  radar  could  cover  more  of  the  planet's  surface, 
the  Purple  Book  concluded  that  "it  is  not  yet  clear  whether  the  high  cost  of  the  addition- 
al information  could  be  justified."  Not  only  would  a  spacecraft  radar  require  "great  weight 
and  complexity"  in  order  to  compete  with  the  resolution  already  achieved  by  ground- 
based  radars,  but  the  "rapidly  improving  capabilities  of  radar  observatories  on  the  earth 
to  image  Venus"  made  radar  mapping  of  the  planet  from  orbit  "less  important  at  the  pre- 
sent time."  The  report  reflected  the  anticipated  benefits  of  the  planned  upgrade  of  the 
Arecibo  telescope. 

While  technological  and  cost  constraints  militated  against  an  orbiting  radar,  a  viable 
alternative,  according  to  the  Purple  Book,  was  the  Stanford  bistatic  radar  method,  specif- 
ically that  mode  in  which  a  radar  on  Earth  transmitted  and  a  receiver  on  the  spacecraft 
collected  echoes.  The  Purple  Book  concluded  that  "bistatic-radar  experiments,  in  con- 
junction with  ground-based  observations,  can  provide  a  significant  insight  into  the  details 
of  the  surface  structure  and  electromagnetic  properties  of  Venus." 

The  recommendation  to  conduct  a  bistatic  experiment  was  not  surprising;  Len  Tyler 
of  the  SCRA  was  one  of  the  21  Purple  Book  scientists.  Although  Tyler  planned  to  do  some 
bistatic  observations  with  Pioneer  Venus,  those  plans  fell  by  the  wayside.  Later,  as 
Pettengill  was  writing  a  proposal  for  Pioneer  Venus  and  was  looking  for  scientists  to  join 
him,  he  invited  Tyler.  Tyler  turned  down  the  invitation  because  of  his  heavy  commitment 
to  the  Voyager  project. 

In  addition  to  the  bistatic  experiment,  the  Purple  Book  recommended  using  a  radar 
altimeter  to  measure  surface  relief.  Radar  altimeter  readings  would  complement  the  equa- 
torial topographic  information  available  from  ground-based  radar  observations,  and  a 
simple,  low-power  orbiting  radar  could  measure  vertical  relief  over  those  portions  of  the 
planet  not  covered  by  ground-based  radars.56  Using  the  altimeter  to  gather  relief  mea- 
surements was  the  cheapest  and  technologically  least  complicated  alternative.  In  the  end, 
a  modified  version  of  this  approach  was  to  fly  on  Pioneer  Venus. 

After  Venera  7  succeeded  in  transmitting  data  from  the  surface  of  Venus  for  23  min- 
utes on  15  December  1970,  a  special  panel  reviewed  the  Purple  Book  conclusions.  Their 
recommendation,  to  make  no  changes  in  the  Purple  Book,  opened  the  door  for  NASA  to 
issue  an  Announcement  of  Opportunity  in  July  1971  for  scientists  to  participate  in  defin- 
ing the  Venus  program.57 

NASA  established  the  Pioneer  Venus  Science  Steering  Group  in  January  1972,  in 
order  to  enlist  widespread  participation  of  the  scientific  community  in  the  early  selection 
of  the  science  requirements  for  the  Pioneer  Venus  project.  The  Science  Steering  Group 
met  with  Pioneer  Venus  project  personnel  between  February  and  June  1972.  The  Group 
developed  in  great  detail  the  scientific  rationale  and  objectives  for  several  voyages  to 
Venus  and  outlined  candidate  payloads.58 


56.  Tyler  10  May  1994;  Simpson  10  May  1994;  Venus:  Strategy  for  Exploration,  pp.  58-62. 

57.  Fimmel,  Colin,  and  Eric,  pp.  17-18. 

58.  Fimmel,  Colin,  and  Burgess,  p.  18. 


1 66  TO  SEE  THE  UNSEEN 


The  search  for  mission  objectives  stirred  radar  astronomer  Gordon  Pettengill  to  pro- 
pose a  radar  experiment  for  the  mission.  Pettengill  recalled:  "I  remember  doing  a  calcu- 
lation literally  on  the  back  of  an  envelope.  I  realized  that  if  we  could  get  even  a  tiny  little 
antenna  into  a  reasonable  orbit  around  Venus,  we  could  do  an  awful  lot  in  terms  of 
measuring  the  altitude  and  the  reflecting  properties  of  the  surface. ...By  going  around 
Venus  in  a  polar,  rather  than  an  equatorial  orbit,  we  could  get  a  totally  new  view  of  Venus. 
We  could  detail  the  whole  surface,  instead  of  just  the  equatorial  band  that  we  observed  at 
Arecibo." 

Pettengill  then  began  "beating  the  drums"  to  include  a  radar  experiment  in  the 
Venus  program.  'The  Science  Working  Group  studied  the  concept.  I  didn't  think  I  was 
going  to  survive  that,"  he  recalled.  "Pioneer  Venus  was  strictly  an  atmospheric  mission.  A 
radar  experiment  to  study  the  surface  stood  out  like  a  sore  thumb."  Nonetheless,  NASA 
awarded  Pettengill  funds  to  conduct  a  feasibility  study  of  a  radar  to  image  Venus.59 

Above  all  else,  the  prime  mission  of  Pioneer  Venus  was  to  study  the  planet's  atmos- 
phere. An  article  published  in  1994  in  Scientific  American60  evaluated  the  scientific  achieve- 
ments of  Pioneer  Venus  and  emphasized  its  contributions  to  atmospheric  science,  but 
failed  to  mention  the  radar  experiment.  Peter  Ford,  who  collaborated  with  Pettengill  on 
the  Pioneer  Venus  radar  experiment,  pointed  out  that  the  Scientific  American  article's 
emphasis  on  the  atmospheric  science  balanced  the  record;  during  the  first  three  years  of 
the  Pioneer  Venus  mission,  most  publicity  had  focused  on  the  radar  imaging.61 

Next,  the  Science  Steering  Group  published  its  comprehensive  report,  called  the 
Orange  Book.  Among  the  24  areas  of  research  advocated,  only  one  was  related  to  the  plan- 
et's surface.  As  the  project  evolved,  Pioneer  Venus  matured  into  a  single-opportunity  mis- 
sion with  a  multiprobe  and  an  orbiter.  In  September  1972,  NASA  disbanded  the  Science 
Steering  Group  and  issued  an  Announcement  of  Opportunity  for  scientists  to  participate 
in  the  multiprobe  mission.  Not  until  August  1973  did  NASA  issue  an  Announcement  of 
Opportunity  for  the  orbiter.  Over  the  ensuing  months,  the  NASA  Instrument  Review 
Committee  evaluated  proposals  for  orbiter  scientific  payloads,  including  Pettengill's  radar 
experiment,  then  presented  its  recommendations  to  NASA  Headquarters  in  May  1974. 
When  NASA  selected  the  final  orbiter  payloads  on  4  June  1974,  the  radar  experiment  was 
among  them. 

The  radar  was  only  one  of  12  scientific  instruments  on  the  orbiter.  In  contrast  to  the 
spaceborne  radar  initially  developed  at  MIT,  which  was  to  consume  no  more  than  100 
watts  and  weigh  less  than  50  pounds,  the  Pioneer  Venus  radar  required  only  18  watts  and 
weighed  9.7  kilograms  (21.3  pounds).  "You  could  literally  put  the  thing  under  one  arm 
and  carry  it,"  as  Pettengill  characterized  it.  Compared  to  other  instruments  on  Pioneer 
Venus,  though,  9.7  kilograms  was  an  appreciable  load;  it  accounted  for  22  percent  of  the 
total  weight  (45  kilograms)  of  all  12  orbiter  scientific  instruments.62 

Although  the  radar  experiment,  in  Pettengill's  words,  "stood  out  like  a  sore  thumb," 
NASA  Headquarters  wanted  to  see  the  surface  features  of  Venus  through  its  white,  sulfu- 
ric-acid  clouds.  The  information  was  a  vital  part  of  planning  for  a  future  mission  to  Venus 
to  map  the  planet's  surface,  known  eventually  as  Magellan.  The  only  reason  the  radar 
experiment  stayed  on  Pioneer  Venus,  according  to  Pettengill,  was  that  Advanced 
Programs  at  NASA  Headquarters  wanted  it,  even  though  its  inclusion  made  life  "a  little 
uncomfortable  for  the  other  experiments."63 


59.  Pettengill  28  September  1993. 

60.  Janet  G.  Luhmann,  Pollack,  and  Colin,  "The  Pioneer  Mission  to  Venus,"  Scientific  American  270  (April 
1994):  90-97. 

61.  Ford  3  October  1994. 

62.  Pettengill  28  September  1993;  Fimmel,  Colin,  and  Burgess,  pp.  18-21,  38  and  58. 

63.  Pettengill  28  September  1993. 


PIONEERING  ON  VENUS  AND  MARS  167 


The  key  individual  in  NASA's  Office  of  Advanced  Programs  who  supported  Pettengill 
and  the  radar  experiment  was  Daniel  H.  Herman.  Before  joining  NASA  in  1970  as  head 
of  Advanced  Programs  in  the  Office  of  Lunar  and  Planetary  Programs,  Herman  had 
worked  at  Northrup  on  the  development  of  surveillance  synthetic  aperture  radar  (SAR) 
mappers  for  the  Navy,  specifically  investigating  the  feasibility  of  transmitting  reconnais- 
sance data  in  real  time.  At  NASA,  his  job  was  to  develop  new  missions  and  to  "sell"  them 
through  the  NASA  hierarchy  and  ultimately  to  the  President  and  Congress.  Danny 
Herman's  job,  then,  was  to  sell  the  Pioneer  Venus  mission.  In  Pettengill's  words,  Herman 
was  "an  eminence  grise"  and  "a  supersalesman."  As  early  as  1972,  Danny  Herman  also 
began  to  put  together  and  push  the  Magellan  project.64 

Unlike  Magellan,  Pioneer  Venus  strictly  speaking  did  not  have  a  synthetic  aperture 
radar;  instead,  the  radar  altimeter  had  a  mapping  mode.  The  most  valuable  data  returned 
from  the  Pioneer  Venus  radar  experiment  would  be  the  extensive  topographical  infor- 
mation acquired  by  the  altimeter.  The  mapping  mode  did  generate  crude,  low  resolution 
images  of  portions  of  the  planet's  surface. 

Far  more  impressive  were  the  images  generated  by  synthetic  aperture  radars  (SARs) 
mounted  on  aircraft  and  regularly  utilized  by  geologists  to  study  the  geology  and  topog- 
raphy of  Earth.  The  use  of  SARs  in  Earth  geology  was  but  one  part  of  a  long  and  complex 
history  that  stretched  from  the  interpretation  of  aerial  photographs  to  the  emergence  of 
remote  sensing,  an  all-encompassing  term  which  has  came  to  involve  the  interpretation  of 
infrared,  ultraviolet,  microwave,  gamma  ray,  and  x-ray  images,  as  well  as  optical  pho- 
tographs. 

Radar  Geology 

Radar  geology,  as  the  study  of  geologic  surface  features  from  radar  maps  has  come 
to  be  called,  had  its  roots  in  the  military  surveillance  radar  research  of  the  1950s.  It  began 
to  find  a  home  in  NASA  during  the  1960s  and  found  a  common  bond  with  planetary  radar 
astronomy  in  the  1970s,  thanks  largely  to  Pioneer  Venus  and  Viking.  The  trickle  of  astro- 
geologists  converted  to  planetary  radar  images  by  Pioneer  Venus  and  Viking  swelled 
through  purposeful  steps  taken  in  the  planning  of  Magellan  to  bring  together  planetary 
geology  and  planetary  radar  investigators. 

By  World  War  I,  aerial  photography  had  become  a  key  tool  in  gathering  military 
intelligence.  The  scientific  applications  of  photointerpretation  grew  after  the  war,  partic- 
ularly during  the  1930s.  Government  agencies,  such  as  the  Agricultural  Adjustment 
Administration,  the  Forestry  Service,  and  the  Tennessee  Valley  Authority,  began  to  use 
aerial  photographs,  and  the  USGS  entered  the  field  of  photogrammetry,  the  making  of 
maps  from  photographs,  with  a  series  of  geologic  and  topographic  maps  constructed  from 
aerial  photographs.65 

After  World  War  II,  the  military  sponsored  research  on  two  types  of  Side-Looking 
Airborne  Radar  (SLAR)  used  in  remote  sensing  and  especially  for  surveillance.  One  type, 
known  as  real-aperture  or  incoherent  radar,  relied  on  transmission  of  a  narrow  beam  to 
provide  fine  image  resolutions  in  the  direction  parallel  to  the  flight  of  the  aircraft.  The 
other  type,  known  as  synthetic  aperture  radar  (SAR),  relied  on  coherent  data  processing 
to  synthesize  a  very  large  effective  aperture  in  the  direction  of  motion  and,  thereby,  to 
provide  a  very  narrow  corresponding  antenna  beam.  Continuously  operating  SARs 
achieve  a  surface  resolution  that  is  independent  of  wavelength  and  approximately  equal 
to  their  along-orbit  physical  antenna  dimension.  Normally,  in  real-aperture  radars, 


64.  Pettengill  28  September  1993;  Daniel  H.  Herman,  telephone  conversation,  20  May  1994. 

65.  William  A.  Fischer,  "History  of  Remote  Sensing,"  in  Robert  G.  Reeves,  Manual  of  Remote  Sensing  (Falls 
Church,  Virginia:  American  Society  of  Photogrammetry,  1975),  [2  volumes]  vol.  1,  pp.  27-39. 


1 68  TO  SEE  THE  UNSEEN 


resolution  is  better  the  shorter  the  wavelength.  In  order  to  achieve  high  resolution,  SARs 
replace  the  need  for  a  large  aperture  with  a  large  amount  of  data  processing.66 

The  military  branches  developed  SARs  in  the  1940s  and  1950s  under  highly  classi- 
fied conditions  in  corporate  and  university  laboratories,  such  as  those  at  the  Goodyear 
Aircraft  Corporation,  the  Philco  Corporation,  the  University  of  Illinois  Control  Systems 
Laboratory,  and  the  University  of  Michigan  Willow  Run  Research  Center.  By  the  late 
1950s,  a  number  of  experimental  SAR  systems  emerged,  such  as  the  one  built  by  Texas 
Instruments  for  the  Army.  In  1961,  under  Air  Force  contract,  Goodyear  built  the  first 
operational  SAR  system;  it  had  a  resolution  of  about  15  meters.  Throughout  the  1960s, 
Goodyear  and  other  firms  began  to  commercialize  SAR  applications.67 

A  series  of  symposia  underwritten  by  the  Office  of  Naval  Research  (ONR)  and  held 
at  the  University  of  Michigan,  where  a  great  deal  of  SLAR  work  took  place  under  contract 
with  the  ONR,  greatly  stimulated  and  advanced  radar  geology.68  The  University  of 
Michigan  symposia  series  grew  out  of  a  study  initially  recommended  by  a  subcommittee  of 
the  National  Academy  of  Sciences  (which  soon  formed  the  Committee  on  Remote 
Sensing  of  Environment)  and  the  Geography  Branch  of  the  ONR.  A  group  from  the  ONR 
and  the  National  Academy  of  Sciences  met  in  January  1961  to  discuss  the  need  for  more 
advanced  and  efficient  data  acquisition  techniques  in  the  Earth  sciences.  Although 
University  of  Michigan  faculty  dominated  the  first  symposium,  held  in  February  1962, 
subsequent  symposia  participants  reflected  the  spreading  commercial  importance  of  SAR 
systems  in  studying  the  Earth.  By  the  third  symposium,  held  in  October  1964,  the  empha- 
sis had  shifted  to  remote  sensing  from  weather  and  other  satellites.69 

During  the  third  University  of  Michigan  symposium,  held  in  October  1964,  R.  F. 
Schmidt  of  the  Avco  Corporation,  Cincinnati,  presented  a  theoretical  study  on  the  feasi- 
bility of  imaging  Venus's  surface  with  a  radar.  Schmidt  failed,  however,  to  address  such 
practical  questions  as  weight  and  power  requirements.70  Nonetheless,  it  was  clear  that 
those  interested  in  remote  sensing,  and  in  radar  imaging  in  particular,  were  open  to  the 
idea  of  imaging  Venus  from  a  spaceborne  radar. 

Meanwhile,  commercial  applications  of  SARs  to  geology  and  topography  expanded. 
The  successful  radar  mapping  of  Panama  in  1967-1968  by  Westinghouse  in  Project  RAMP, 
considered  to  be  one  of  the  major  achievements  in  radar  geology,  further  stimulated  com- 
mercial radar  mapping.  In  late  1971,  Westinghouse  surveyed  the  entire  country  of 
Nicaragua,  and  that  same  year  the  Aero  Service/Goodyear  RADAM  Project  (RADar  of  the 
AMazon),  initially  intended  to  cover  only  1.5  million  square  kilometers,  eventually  cov- 
ered the  entire  country  of  Brazil,  over  8.5  million  square  kilometers.  RADAM  was  consid- 
ered the  most  impressive  radar  mapping  program  ever  conducted.71 


66.  For  a  discussion  of  space  SARs  by  one  of  its  leading  practitioners,  see  Charles  Elachi,  Spaceborne 
Radar  Remote  Sensing:  Applications  and  Techniques  (New  York:  IEEE  Press,  1987). 

67.  Fischer,  pp.  42-43;  Allen  M.  Feder,  "Radar  Geology,  the  Formative  Years,"  Geotimes  vol.  33,  no.  11 
(1988):  11-14.  See  alsojohnj.  Kovaly,  Synthetic  Aperture  Radar  (Dedham,  MA:  Artech  House,  Inc.,  1976),  Chapter 
One.  I  am  grateful  to  Louis  Brown  for  this  last  reference. 

68.  Feder,  p.  12. 

69.  Proceedings  of  the  First  Symposium  on  Remote  Sensing  of  Environment  (Ann  Arbor:  University  of  Michigan 
Institute  of  Science  and  Technology,  March  1962).  Of  the  72  participants,  37  of  them,  or  51%,  were  University 
of  Michigan  faculty.  Proceedings  of  the  Second  (Ann  Arbor:  University  of  Michigan  Institute  of  Science  and 
Technology,  February  1963);  Proceedings  of  the  Third  Symposium  (Ann  Arbor:  University  of  Michigan  Institute  of 
Science  and  Technology,  October  1964);  Proceedings  of  the  Fourth  Symposium  (Ann  Arbor:  University  of  Michigan 
Institute  of  Science  and  Technology,  June  1966). 

70.  Peter  C.  Badgley,  The  Applications  of  Remote  Sensors  in  Planetary  Exploration,"  in  Proceedings  of 
the  Third  Symposium,  pp.  9-28;  R.  F.  Schmidt,  "Radar  Mapping  of  Venus  from  an  Orbiting  Spacecraft,"  ibid.,  pp. 
51-61. 

71.  Feder,  p.  13;  H.  MacDonald,  "Historical  Sketch:  Radar  Geology,"  pp.  23-24  and  27-28  in  Radar 
Geology:  An  Assessment  Publication  80-61  (Pasadena:  JPL,  1  September  1980).  This  was  a  report  of  the  Radar 
Geology  Workshop,  held  at  Snowmass,  Colorado,  16-20  July  1979. 


PIONEERING  ON  VENUS  AND  MARS  1 69 


Parallel  with  the  development  of  SAR  mapping  of  Earth  was  the  rise  of  astrogeology 
within  the  USGS  in  the  late  1950s  in  response  to  a  shortage  of  funds  and  a  surplus  of  geol- 
ogists within  the  Survey.  Following  the  discovery  of  an  abundant  supply  of  uranium  ore  in 
New  Mexico,  the  USGS  uranium  project  closed  down  in  1958.  Eugene  Shoemaker,  a  geol- 
ogist who  moved  to  the  USGS  Pacific  Coast  Regional  Center  at  Menlo  Park,  California,  fol- 
lowing the  closure  of  the  uranium  project,  suggested  lunar  geologic  mapping  as  one  way 
to  help  alleviate  the  money  and  personnel  problems. 

Shoemaker,  who  did  his  dissertation  on  Meteor  Crater,  sold  lunar  geologic  mapping 
to  NASA,  which  in  contrast  to  the  USGS  had  funding  but  too  few  geologists.  The  result 
was  the  creation  of  the  Astrogeologic  Studies  Group,  USGS,  Menlo  Park,  on  25  August 
1960.  Later,  Shoemaker  led  a  group  of  astrogeologists  to  a  new  location  in  Flagstaff, 
Arizona.72  In  1963,  geologist  Peter  C.  Badgley  came  to  NASA  from  the  Colorado  School 
of  Mines.  Badgley  was  interested  in  techniques  for  observing  Earth  from  space,  particu- 
larly to  support  the  Apollo  program.  He  let  out  contracts  to  firms,  such  as  Westinghouse, 
and  universities,  especially  the  University  of  Michigan,  to  carry  out  radar  geologic  studies 
from  aircraft.  Moreover,  Badgley  continued  to  shift  NASA  money  to  the  USGS  to  fund 
lunar  and  planetary  geology.73  Thus,  the  evolution  of  the  NASA  space  program  and  the 
USGS  astrogeology  branch  marched  forward  in  tandem. 

During  the  Apollo  program,  certain  USGS  astrogeologists  began  collaborating  with 
radar  astronomers  Stan  Zisk  and  Tommy  Thompson.  Among  them  were  Henry  John 
Moore  II,  Shoemaker's  former  field  assistant  and  part  of  the  Menlo  Park  Astrogeologic 
Studies  Group,  and  Gerald  G.  Schaber,  UCLA  and  USGS  Flagstaff.74  These  early  lunar 
efforts  involved  radar  mapping  and  topographical  data  collected  from  ground-based 
radars,  not  abstract  data  on  rms  slope  and  dielectric  constant.  Schaber  collaborated  with 
Tyler  on  interpreting  lunar  bistatic  radar  results,  which  were  expressed  in  abstract  math- 
ematical terms.  Schaber  admitted,  "I  never  really  did  much  with  the  interpretation  of 
bistatic  radar,  because  it  is  kind  of  a  theoretical  interpretation  I  don't  really  understand 
too  much."75 

The  launch  of  SEASAT  in  the  summer  of  1978  began  the  era  of  satellite  radar 
imagery.  SEASAT  demonstrated  the  feasibility  of  radar  observations  of  Earth  on  a  global 
basis,  and  initial  examination  of  the  SEASAT  radar  data  indicated  that  one  could  fruitful- 
ly apply  the  data  to  a  variety  of  problems  in  geology,  agriculture,  hydrology,  and  oceanog- 
raphy, as  well  as  to  planetary  exploration.76 

In  order  to  assess  the  application  of  radar  imaging  to  terrestrial  geologic  problems 
and  to  make  recommendations  to  NASA,  JPL  sponsored  the  Radar  Geology  Workshop  in 
Snowmass,  Colorado,  16-20  July  1979,  with  funding  from  NASA.  Among  those  on  the 
organizing  committee  were  Harold  Masursky,  USGS,  and  R.  Stephen  Saunders,  JPL,  who 
later  played  a  role  on  Magellan.  The  workshop  focused  on  radar  observations  of  Earth, 
not  the  planets.77 

Thus,  by  the  launch  of  SEASAT  in  1978,  the  year  also  of  Pioneer  Venus's  launch,  a 
good  number  of  geologists  were  familiar  with  and  could  interpret  radar  images  of  Earth 
made  from  aircraft.  But  those  geologists  were  more  interested  in  terrestrial  than  extrater- 
restrial geology.  On  the  other  hand,  through  the  pioneering  efforts  of  Gene  Shoemaker, 
the  USGS  Astrogeologic  Studies  Group  already  had  embraced  lunar  radar  geology.  The 


72.  Wilhelms,  pp.  37-40,  43,  46,  48  and  77. 

73.  Pamela  E.  Mack,  Viewing  the  Earth:  The  Social  Construction  of  the  Landsat  Satellite  System  (Cambridge: 
The  MIT  Press,  1990),  pp.  46-49;  MacDonald,  pp.  26  and  28-29. 

74.  Wilhelms,  p.  47;  Thompson  29  November  1994.  See,  for  instance,  Shapiro,  Stanley  H.  Zisk,  Rogers, 
Slade,  and  Thompson,  "Lunar  Topography:  Global  Determination  by  Radar,"  Science  17  (1972):  939-948. 

75.  Schaber  27  June  1994. 

76.  John  P.  Ford,  "Seasat  Orbital  Radar  Imagery  for  Geologic  Mapping:  Tennessee-Kentucky-Virginia," 
American  Association  of  Petroleum  Geologists  Bulletin  64  (1980):  2064-2094;  Radar  Geology:  An  Assessment,  p.  1. 

77.  Radar  Geology:  An  Assessment,  passim. 


170 


TO  SEE  THE  UNSEEN 


Figure  27 

SEAS.\T  image  of  Death  Valley,  Earth.  The  launch  ofSEASAT  in  1978  began  the  era  of  satellite  radar  imagery.  The  resolu- 
tion of  images  made  by  military  surveillance  satellites  was  much  finer,  however.  Utilization  ofSEASAT  technology  was  a  basic 
strategy  adopted  byJPL  in  the  planning  of  VOIR  (later  Magellan).  (Courtesy  of  Jet  Propulsion  Laboratory,  photo  no.  P-30224.) 

potential  for  planetary  geologists  and  planetary  radar  astronomers  to  work  together 
already  had  been  realized  in  the  Apollo  program  through  the  work  of  Stan  Zisk  and 
Tommy  Thompson.  The  NASA  Pioneer  Venus  working  committees  brought  together 
additional  radar  astronomers  and  geologists. 

Once  NASA  decided  the  Pioneer  Venus  payloads  and  science  experiments  in  June 
1974,  the  space  agency  created  the  Orbiter  Mission  Operations  Planning  Committee. 
Among  its  members  were  USGS  astrogeologist  Hal  Masursky  and  radar  astronomer 
Gordon  Pettengill.  They  also  worked  together  closely  in  the  Surface-Interior  Working 
Group,  one  of  the  six  mission  Working  Groups  responsible  for  developing  key  scientific 
questions.  Hal  Masursky  chaired  that  Working  Group  (Table  4).78 


78.      Fimmel,  Colin,  and  Burgess,  pp.  22  and  218. 


PIONEERING  ON  VENUS  AND  MARS 


171 


Table  4 
Pioneer  Venus  Surface/Interior  Working  Group 

Scientist 

Institution 

Harold  Masursky 
C.T.  Russell 
Gordon  H.  Pettengill 
William  M.  Kaula 
George  E.  McGill 
RogerJ.  Phillips 
Irwin  I.  Shapiro 

US  Geological  Survey 
University  of  California,  Los  Angeles 
Massachusetts  Institute  of  Technology 
University  of  California,  Los  Angeles 
Massachusetts  Institute  of  Technology 
Lunar  and  Planetary  Institute 
Massachusetts  Institute  of  Technology 

Pioneer  Venus 

Without  the  radar  experiment,  Pioneer  Venus  would  not  have  brought  together 
planetary  geologists  and  radar  astronomers.  Attending  meetings  of  the  Working  Groups, 
as  well  as  all  mission  meetings,  was  vital  to  the  survival  of  the  radar  on  a  project  whose 
prime  objectives  were  atmospheric.  As  Pettengill  explained:  "It  was  a  very  demanding  pro- 
ject that  had  to  be  watched  closely.  I  had  to  make  sure  that  we  did  not  lose  radar  capabil- 
ity. We  were  fighting  with  1 1  other  Principal  Investigators  on  Pioneer  Venus.  It  was  very 
important  that  I  never  miss  a  meeting.  If  I  missed  one  meeting,  those  guys  might  come  to 
some  decision  that  would  compromise  the  experiment." 

The  Pioneer  Venus  atmospheric  experiments  competed  with  the  radar  experiment 
for  spacecraft  parameters.  The  atmospheric  scientists  wanted  a  different  set  of  orbits  and 
a  different  allocation  of  down  link  data  bits.  "It  was  a  jungle  out  there!"  Pettengill  recalled. 
"You  had  to  have  a  certain  number  of  bits,  or  you  could  not  do  your  work.  If  you  turned 
your  back,  literally  if  you  missed  one  meeting,  they  could  make  a  decision  to  allocate  20 
percent  of  that  particular  format  to  some  experiment  instead  of  only  10  percent.  Then 
you  have  lost  that  10  percent.  In  1975,  especially,  all  of  this  was  coming  together.  I  could- 
n't miss  a  meeting.  It  really  was  taking  up  my  time."79 

The  data  handling  system  on  the  orbiter  integrated  all  analog  and  digital  telemetry 
data  into  formats  for  transmission  back  to  Earth.  Telemetry  storage,  playback,  and  real- 
time rates  varied.  The  orbiter  had  a  total  of  14  telemetry  formats;  some  were  used  during 
periapsis,  others  during  apoapsis.  The  radar  was  a  heavy  user  of  two  formats  designed  for 
use  at  periapsis,  and  in  fact  it  used  more  of  those  two  formats  than  any  other  experiment. 

NASA  procured  scientific  instruments  for  Pioneer  Venus  in  a  variety  of  ways. 
Normally,  the  principal  investigator  was  responsible  for  an  instrument's  design  and 
construction.  Either  his  own  laboratory  or  a  subcontractor  built  the  instrument.  NASA 
used  a  different  procurement  method  for  the  Pioneer  Venus  radar.  The  project  office  at 
Ames  Research  Center  built  it  for  a  radar  team  headed  by  Pettengill.  Carl  Keller,  an  Ames 
Research  Center  engineer,  had  overall  decision-making  responsibility,  and  the  instrument 
prime  contractor  was  the  Hughes  Aircraft  Company  Space  and  Communications  Group, 
El  Segundo,  California,  as  a  result  of  an  open  bid  procurement.  Pettengill  characterized 
Carl  Keller  as  an  engineer  from  "the  old  school,  a  seat-of-the-pants,  no  nonsense  teuton- 
ic. He  would  look  at  all  the  details.  He  was  the  right  guy  for  the  job.  I  enjoyed  working 
with  him.  Not  everybody  did."80 


79.  Pettengill  28  September  1993. 

80.  Pettengill  28  September  1993;  Fimmel,  Colin,  and  Burgess,  pp.  22,  41  and  43. 


1 72  TO  SEE  THE  UNSEEN 


Both  MIT's  Center  for  Space  Research,  with  which  Pettengill  was  associated,  and  JPL 
competed  for  the  Pioneer  Venus  radar  contract.  The  rivalry  between  MIT  and  JPL  was 
tense,  "a  real  Shootout"  in  Pettengill's  words.  At  JPL,  Walter  Brown  had  been  working  on 
a  Venus  orbiter  radar  since  the  1960s.  His  approach,  however,  differed  considerably  from 
that  of  MIT. 

Walter  Brown's  radar  proposal  involved  placing  a  100-MHz  (3-meter)  transmitter  on 
the  Pioneer  Venus  orbiter,  while  Pettengill  and  the  MIT  Center  for  Space  Research  pro- 
posed a  1,757-MHz  (17-cm)  system.  The  MIT  antenna  was  directive,  so  that  when  the 
spacecraft  rotated,  it  took  data  for  only  a  fraction  of  each  12-second  rotation  of  the  space- 
craft.81 

As  Pettengill  reflected:  "Meanwhile,  JPL  thought  they  had  the  inside  track.  They 
were  a  NASA  center,  after  all,  and  this  was  a  NASA  project.  If  I  have  a  fault  to  lay  on  JPL, 
it  is  that  they  think  that  there  is  no  place  else  in  the  world  that  does  things  as  well  as  they 
do.  They  think  they  deserve  the  first  cut  of  everything,  because  they  are  so  much  better 
than  everybody  else.  They  don't  take  kindly  to  new  ideas  that  are  not  in-house;  not  invent- 
ed here  is  very  much  a  JPL  hallmark.  Irwin  Shapiro  has  fought  this  on  the  Planetary 
Ephemeris  Program.  We  fought  it  on  radar  work,  and  Stanford  has  fought  it.  It  has  been 
difficult  over  time.  JPL  is  so  institutionalized  into  thinking  that  no  one  else  can  do  any- 
thing but  them.  It  has  been  an  uphill  battle  over  the  years.  It  has  put  grey  hairs  on  Von 
Eshleman's  head;  it  certainly  put  a  few  on  mine." 

JPL  lost  the  radar  battle.  Their  design  would  have  bathed  the  whole  spacecraft,  even 
the  solar  panels,  in  radiation  from  the  radar.  The  antenna  extended  all  around  the  space- 
craft, so  that  as  the  spacecraft  rotated,  the  radar  always  was  transmitting.  To  Walter  Brown, 
that  was  the  advantage,  but  it  made  the  electronics  engineers  nervous. 

In  the  end,  neither  MIT  nor  JPL  built  the  Pioneer  Venus  radar,  but  it  is  typical  of  the 
kinds  of  fights  for  hardware  contracts  that  mark  NASA  space  missions.  The  winner  of  the 
contract  was  Hughes.  Hughes  devised  a  method  by  which  the  radar  altimeter  could  image 
the  planet's  surface  at  low  resolution  with  a  small,  38-cm-diameter  antenna.  The  elec- 
tronics of  the  MIT  design  were  clumsy,  Pettengill  admitted,  whereas  the  Hughes  proposal 
was  'Very  clever  and  efficient." 

"If  we  had  done  the  experiment,"  he  mused,  "it  probably  would  not  have  stayed  in. 
I  have  to  hand  Hughes  some  credit  for  that.  They  really  had  a  flash  of  insight  into  a  clever 
way  of  instrumenting  it.. ..They  had  a  good  team,  and  so  did  we.  The  main  reason  Hughes 
won  was  that  they  were  willing  to  take  a  loss."  For  Hughes,  taking  a  loss  on  the  Pioneer 
Venus  radar  contract  was  a  gambit  to  gain  leverage  on  the  Magellan  radar  contract,  which 
they  ultimately  won.  "At  the  time,"  Pettengill  recalled,  awarding  Hughes  the  radar  map- 
per contract  "hurt  a  bit.  I  was  hoping  to  get  the  hardware  here  at  the  Center  for  Space 
Research." 

In  August  1974,  Congress  approved  Pioneer  Venus  as  a  new  start  for  fiscal  1975,  and 
in  November  1974,  NASA  made  the  final  contract  award  to  Hughes  Aircraft  Company.  By 
1975,  only  three  years  away  from  launch,  Pettengill  recalled,  "it  all  came  together.  With 
the  Hughes  contract,  we  started  cutting  metal."83  On  20  May  1978,  the  orbiter  left  Cape 
Kennedy,  followed  atop  a  second  Adas-Centaur  rocket  by  the  multiprobe  on  8  August 
1978.  Both  reached  Venus  in  early  December  1978.84 

The  radar  was  a  complicated  instrument  capable  of  operating  in  one  of  two  modes, 
altimeter  or  mapper.  It  was  a  1 ,757-MHz  ( 1 7-cm)  radar  with  a  peak  output  of  20  watts  and 
utilized  relatively  long  pulses  to  improve  the  signal-to-noise  ratio.  Such  a  radar  could  not 


81.  Pettengill  28  September  1993;  Memorandum,  Brunk,  29  November  1966,  NHOB. 

82.  Pettengill  28  September  1993. 

83.  Pettengill  28  September  1993. 

84.  Fimmel,  Colin,  and  Burgess,  pp.  27  and  35. 


PIONEERING  ON  VENUS  AND  MARS  1 73 


have  performed  planetary  radar  astronomy  experiments  from  Earth,  but  reducing  the  dis- 
tance to  the  target  made  all  the  difference. 

Shortly  after  its  encounter  with  Venus,  the  orbiter  began  making  altimeter  measure- 
ments of  surface  relief.  The  altimeter  measured  the  distance  from  the  orbiter  to  the  plan- 
et's surface.  In  order  to  ascertain  the  height  and  depth  of  surface  features,  that  distance 
was  subtracted  from  the  spacecraft's  orbital  radius,  that  is,  the  distance  between  the  space- 
craft and  the  planet's  center  of  mass.  The  Deep  Space  Network,  while  maintaining  two- 
way  communications  with  the  spacecraft,  generated  radiometric  data  from  which  JPL 
accurately  calculated  its  orbit,  and  the  MIT  group  then  used  both  the  orbital  and  radar 
data  to  determine  the  radius  of  the  planet  at  discrete  positions  on  the  surface. 

In  the  radar  mapper  mode,  the  instrument  compensated  for  the  complex  motion  of 
the  spacecraft.  Because  the  orbiter  spun  on  its  own  axis  about  five  revolutions  per  minute, 
radar  observations  took  place  only  periodically,  about  one  second  out  of  each  12-second 
spin  of  the  orbiter.  The  radar  mapper  also  automatically  compensated  for  the  Doppler 
shift  caused  by  the  motion  of  the  orbiter  relative  to  the  planet. 

The  instrument  took  altimeter  data,  whenever  the  orbiter  was  below  4,700  km,  and 
imaging  data,  when  the  orbiter  was  below  550  km,  subject  to  competition  with  other 
experiments  for  the  limited  telemetry  capacity.  In  order  to  minimize  telemetry  require- 
ments, the  orbiter  processed  the  radar  echoes  on  board  the  spacecraft.  The  radar  mapper 
achieved  its  best  resolution,  a  footprint  23  km  long  and  7  km  wide,  at  periapsis.  The  radar 
data  also  provided  information  on  surface  roughness  and  electrical  conductivity.85 

The  radar  mapper's  first  sweeps  showed  a  region  of  Venus  previously  unexplored  by 
ground-based  radar.  With  the  exception  of  a  deep  trench  near  the  equator,  the  surface  of 
Venus  appeared  relatively  flat,  similar  to  the  Earth's  surface  and  quite  different  from  the 
rough,  cratered  surfaces  of  Mars,  Mercury,  and  the  Moon.  Pioneer  Venus  continued  to 
complete  one  orbit  per  day,  when  on  the  14th  orbit,  the  radar  mapper  began  to  malfunc- 
tion; data  was  lost.  Scientists  and  engineers  failed  to  find  a  remedy.  Mission  control  turned 
off  the  radar  for  about  two  weeks  around  Christmas  and  the  New  Year.  When  mission  con- 
trol turned  on  the  radar  mapper,  they  discovered  that  it  worked,  though  not  quite  nor- 
mally. 

The  problem,  eventually  traced  to  a  timing  malfunction  that  resulted  from  a  differ- 
ential "aging"  rate  in  two  interconnected  semiconductor  devices,  appeared  when  the 
instrument  operated  longer  than  ten  hours.  Pettengill,  the  experiment  team  leader,  and 
project  personnel  decided  to  operate  the  radar  mapper  intermittently.  After  about  10  days 
of  intermittent  operation,  the  instrument  started  to  function  normally  on  20  January  1979 
(orbit  47)  .86 

Somehow,  though,  the  mission  had  to  recover  the  lost  data.  Data  recovery  was  not 
possible  during  the  first  extended  mission  (September  1979),  because  the  Deep  Space 
Network  was  handling  communications  with  Pioneer  11  at  Saturn,  so  it  took  place  during 
the  second  extended  mission,  April-May  1980.  The  10  other  scientific  instruments  (the 
infrared  experiment  failed  after  a  few  months  and  never  ran  again)  continued  to  transmit 
data  back  to  Earth;  the  radar  mapper,  however,  was  turned  off  as  planned  after  Orbit  834 
on  19  March  1981.87 


85.  Fimmcl,  Colin,  and  Burgess,  pp.  58-59  and  113-115;  Pettengill,  D.  F.  Horwood,  and  Carl  H.  Keller, 
"Pioneer  Venus  Orbiter  Radar  Mapper:  Design  and  Operation,"  IEEE  Transactions  on  Geosdence  and  Remote  Sensing 
GE-18  (1980):  28-32;  Pettengill,  Peter  G.  Ford,  and  Stewart  Nozette,  "Venus:  Global  Surface  Radar  reflectivity," 
ScienceZn  (1982):  640-642. 

86.  Pettengill,  Ford,  Walter  E.  Brown,  William  M.  Kaula,  Carl  H.  Keller,  Harold  Masursky,  and  George 
E.  McGill,  "Pioneer  Venus  Radar  Mapper  Experiment,"  Science  203  (1979):  806-808;  Colin,  "The  Pioneer  Venus 
Program, "  Journal  of  Geophysical  Research  85  (1980):  7588-7589;  Fimmel,  Colin,  and  Burgess,  p.  107;  Pettengill, 
Ford,  Brown,  Kaula,  Masursky,  Eric  Eliason,  and  McGill,  "Venus:  Preliminary  Topographic  and  Surface  Imaging 
Results  from  the  Pioneer  Orbiter,"  Sdence2Q5  (1979):  91-93. 

87.  Colin,  pp.  7589  and  7590;  Fimmel,  Colin,  and  Burgess,  p.  191. 


1 74  TO  SEE  THE  UNSEEN 


The  processing  and  interpretation  of  Pioneer  Venus  altimeter  and  mapper  data  sets 
by  the  MIT  group  again  brought  together  planetary  geologists  and  radar  astronomers. 
Peter  G.  Ford,  Pettengill's  colleague  in  the  MIT  Department  of  Earth  and  Planetary 
Sciences,  was  a  central  player  in  the  MIT  effort.  A  native  of  Britain,  Peter  Ford  initially 
came  to  MIT  to  work  in  VLBI  (Very  Long  Baseline  Interferometry)  radio  astronomy  with 
Irwin  Shapiro.  From  1977  to  1985,  he  worked  on  various  aspects  of  the  Pioneer  Venus 
orbiting  radar  experiments,  including  their  geologic  interpretation,  although  his  training 
was  in  nuclear  physics.  The  USGS  processed  some  of  the  data  to  create  a  three-dimen- 
sional effect  which  graphically  revealed  depressions  and  mountains.  Key  among  the  plan- 
etary geologists  were  Hal  Masursky  and  Gerald  Schaber  of  the  USGS,  Flagstaff,  and 
George  E.  McGill,  University  of  Massachusetts  at  Amherst. 

The  collaboration  of  radar  astronomy  and  planetary  geology  resulted  in  many 
important  discoveries  about  the  surface  of  Venus,  although  preliminary  analysis  showed 
that  much  more  could  be  learned  about  the  planet's  geological  history.  The  altimeter  data 
was  used  to  create  a  number  of  maps,  including  a  topographic  contour  map,  a  shaded 
relief  map,  and  a  map  showing  relative  degrees  of  surface  roughness.  The  altimeter  and 
radar  mapper  data  sets  were  assembled  and  placed  in  position  by  computer;  however,  vari- 
ations from  orbit  to  orbit  were  edited  by  hand  then  smoothed  out  by  computer. 

In  preparation  for  the  mission,  a  preliminary  map  was  compiled  from  ground-based 
images  and  used  by  mission  operations  for  planning.  For  this  map,  Goldstone  radar 
images  were  computer  mosaicked,  and  images  obtained  at  Arecibo  were  mosaicked  from 
photographic  copy.  The  scale  of  this  map  was  1:50,000,000.  Once  the  Pioneer  Venus  data 
were  in  hand,  the  map  was  updated  to  combine  the  spacecraft  and  ground-based  data. 

The  radar  altimeter  yielded  a  topographic  map  covering  93  percent  of  the  Venus 
globe,  with  a  linear  surface  resolution  of  better  than  150  km.  Vertical  measurement  accu- 
racy exceeded  200  meters.  Relief  was  expressed  as  a  center-of-mass-to-surface  radius. 
Extremes  went  from  a  low  of  6,049  km  to  a  high  of  6,062  km.  Despite  these  impressive 
extremes  of  surface  height  and  depth,  the  Pioneer  Venus  data  confirmed  and  greatly 
expanded  previous  Earth-based  observations  on  the  global  smoothness  of  Venus  relative 
to  the  Moon,  Mars,  and  Earth.  Only  about  five  percent  of  the  observed  surface  was  ele- 
vated more  than  two  km  above  the  mean  radius,  6,051.5  ±0.1  km. 

Radar  astronomer  Gordon  Pettengill  processed  and  interpreted  Pioneer  Venus 
altimeter  and  mapper  data  sets.  Don  Campbell  at  Arecibo,  and  Dick  Goldstein  and 
Howard  C.  Rumsey,  Jr.,  at  JPL,  supplied  ground-based  radar  images  and  digital  tapes, 
many  before  publication.  The  Arecibo  and  JPL  radar  images  were  compiled  into  a 
mosaic  for  the  Pioneer  Venus  Planning  Chart  that  was  used  in  mission  operations.  Their 
high-resolution,  Earth-based  radar-imaging  data  also  was  essential  for  the  interpretation 
of  the  spacecraft  images  and  altimetry  data.  Thus,  ground-based  radar  astronomers  were 
brought  into  the  Pioneer  Venus  project,  and  association  with  the  project  facilitated  radar 
astronomers'  access  to  the  Goldstone  radar. 

The  radar  brightness  and  elevation  extremes  dominated  the  imaging  and  topo- 
graphic maps  of  the  highlands  province,  which  included  Ishtar  Terra,  Aphrodite  Terra, 
and  Beta  Regio.  The  two  highland  regions,  Ishtar  and  Aphrodite  terrae,  resembled  ter- 
restrial "continents"  because  they  were  high  and  had  areas  comparable  to  continents  on 
Earth.  Ishtar  and  Aphrodite  appeared  to  be  the  size  of  continents,  roughly  equivalent  to 
Australia  and  Africa,  respectively.  Beta,  a  much  smaller  feature  initially  detected  with 
ground-based  radar,  appeared  to  differ  from  Ishtar  and  Aphrodite  in  roughness  char- 
acteristics and  possibly  in  age  and  chemical  composition.  Ishtar  Terra  was  the  most  ele- 
vated region  found  on  Venus.  It  included  three  topographic  elements:  Lakshmi  Planum, 
a  western  plateau  area;  Maxwell  Monies,  the  central  mountainous  area  previously  studied 


PIONEERING  ON  VENUS  AND  MARS 


175 


with  Earth-based  radars;  and  a  complex  eastern  region.  The  highest  point  found  on  Venus 
was  the  summit  of  Maxwell  Monies.  Standing  11.1  km  above  the  planet's  average  radius 
(in  Earth  terms,  above  sea  level),  Maxwell  Monies  was  higher  than  Mount  Everest,  which 
reaches  8.8  km  above  sea  level.  The  lowest  poini  found  on  Venus  was  a  rifl  valley  or  irench 
named  Diana  Chasma.88 


Figure  28 

Pioneer  Venus  map  of  Venus,  1 980,  showing  A  Ipha  Regio  and  Maxwell  Mantes,  along  the  planet 's  meridian,  and  Beta  Hegio 
at  longitude  280°.  Diana  Chasma  is  at  longitude  160°.  Compare  this  map  with  the  Venus  mosaic  made  from  Arecibo 
Observatory  radar  observations  (Fig.  30).  (Courtesy  of  Jet  Propulsion  Laboratory,  photo  no.  P45744.) 

The  planetary  radar  and  geology  collaboration  yielded  a  host  of  new  topographical 
names.  In  order  lo  systematically  standardize  the  names  of  Venus  surface  features,  as  well 
as  those  discovered  earlier  on  Mars  and  the  Moon,  on  an  international  level,  the 
International  Astronomical  Union  (IAU)  created  the  Working  Group  for  Planetary 
Sysiem  Nomenclaiure  (WGPSN)  during  iis  15th  General  Assembly  at  Sydney,  21-30 
August  1973.  The  IAU  established  the  WGPSN  because  of  ihe  receni  rapid  advance  in 
knowledge  of  the  topography  and  surfaces  of  planetary  bodies,  as  well  as  the  necessity  of 
coordinating  ihe  approved  systems  of  nomenclature  among  the  differenl  planels  and 
iheir  salelliles. 


88.  Fimmel,  Colin,  and  Burgess,  p.  154;  Masursky,  Eliason,  Ford,  McGill,  Pettengill,  Gerald  G.  Schaber, 
and  Schubert,  "Pioneer  Venus  Radar  Results,"  Journal  of  Geophysical  Research  85  (1980):  8232-8260;  Pettengill, 
Eliason,  Ford,  George  B.  Loriot,  Masursky,  and  McGill,  "Pioneer  Venus  Radar  Results:  Altimetry  and  Surface 
Properties,"  Journal  of  Geophysical  Research  85  (1980):  8261-8270;  V-Gram  no.  10  (January  1987):  20. 


1 76  TO  SEE  THE  UNSEEN 


Unlike  most  other  IAU  working  groups,  the  WGPSN  did  not  report  through  any 
commission  or  group  of  commissions,  but  was  responsible  to  only  the  IAU  Executive 
Committee.  The  WGPSN  was  charged  with  formulating  and  coordinating  all  topographic 
nomenclature  on  the  planetary  bodies  of  the  solar  system  and  had  certain  powers  of 
action  in  the  interval  between  General  Assemblies.  Radar  astronomer  Gordon  Pettengill 
was  a  member  of  the  WGPSN.  The  Task  Group  for  Venus  Nomenclature,  responsible  for 
compiling  the  detailed  material  presented  to  the  WGPSN,  included  Gordon  Pettengill, 
chair,  JPL  radar  astronomer  Dick  Goldstein,  USGS  geologist  Hal  Masursky,  and  the  Soviet 
scientist  M.  Ya.  Marov. 

Although  the  first  meeting  of  the  WGPSN,  held  in  Ottawa,  27-28  June  1974,  did  not 
concern  itself  with  the  naming  of  surface  features  on  Venus,  at  the  second  meeting,  held 
in  Moscow,  14-18  July  1975,  the  WGPSN  named  three  valleys  on  Mercury  Arecibo, 
Goldstone,  and  Haystack  after  the  radar  observatories  and  established  two  themes  for 
naming  Venus  features.  The  first  theme  was  the  "feminine  mystique  long  associated  with 
Venus."  Hence,  for  example,  the  continent-sized  features  Ishtar  and  Aphrodite  were 
named  for  the  Babylonian  and  Greek  goddesses  of  love,  respectively. 

The  second  theme  arose  from  the  "extensive  and  opaque  cloud  cover  which  sur- 
rounds the  planetary  sphere"  which  "requires  the  use  of  radio  and  other  techniques  in 
order  to  study  and  map  the  surface."  Therefore,  the  WGPSN  proposed  "to  assign  the 
names  of  deceased  radio,  radar  and  space  scientists  to  topographic  features."  One  excep- 
tion, Alpha,  was  admitted.  Alpha  was  one  of  the  first  Cytherean  features  to  be  observed 
"and  which  has  served  to  help  define  the  origin  of  the  official  IAU  system  of  longitude  for 
the  planet."  During  subsequent  meetings  of  the  WGPSN,  held  in  Grenoble,  30-31  August 
1976;  Washington,  1-2  June  1977;  Innsbruck,  2  June  1978;  and  Montreal,  13-15  August 
1979,  the  WGPSN  approved  not  only  Alpha,  but  Beta  and  Maxwell  as  well.89  Thus,  the  fea- 
ture names  first  given  by  ground-based  radar  astronomers  were  fixed  on  the  map  of  Venus. 

Pioneer  Venus  awakened  more  planetary  geologists  to  the  value  of  radar  data,  espe- 
cially radar  images.  Pioneer  Venus  also  was  a  new  taste  of  Big  Science  that  would  lead  to 
the  Magellan  mission.  In  turn,  Magellan  culminated  the  linking  of  planetary  geology  with 
radar  astronomy  and  further  blurred  the  distinction  made  earlier  in  the  history  of  plane- 
tary radar  astronomy  between  ground-based  radar  and  space  exploration. 


89.  Transactions  of  the  International  Astronomical  Union  17A  (1979):  113-114;  "Working  Group  for 
Planetary  System  Nomenclature,"  Ibid.  16B  (1977):  321-369;  "Working  Group  for  Planetary  System 
Nomenclature,"  Ibid.  17B  (1980):  285-304. 


Chapter  Seven 

Magellan 


Magellan  culminated  the  shift  of  radar  astronomy  toward  planetary  geology  kindled 
by  Apollo  and  fostered  by  Viking  and  Pioneer  Venus  with  the  creation  of  workshops  and 
microsymposia.  The  workshops  attempted  to  bridge  the  gap  between  radar  and  geologic 
knowledge  among  practitioners,  while  the  microsymposia  provided  annual  opportunities 
for  U.S.  and  Soviet  geology  and  radar  scientists  interested  in  Venus  to  exchange  research 
results.  This  shifting  of  the  planetary  radar  paradigm  toward  geology  also  manifested  itself 
in  articles  co-authored  with  planetary  geologists,  publication  in  new  journals,  especially 
the  Journal  of  Geophysical  Research,  and  attendance  at  American  Geophysical  Union  meet- 
ings. 

Furthermore,  the  close  relationship  between  NASA  missions  and  ground-based  plan- 
etary radar  astronomy  that  had  developed  at  Haystack,  Arecibo,  and  Goldstone  since  1970 
continued  with  Magellan.  The  Arecibo  and  Goldstone  radars  observed  Venus  throughout 
the  two  decades  spanned  by  Pioneer  Venus  and  Magellan,  and  their  data  contributed  to 
the  success  of  those  missions.  In  addition,  the  range-Doppler  images  created  from  that 
data  also  drew  geologists  to  planetary  radar  astronomy. 

Magellan,  like  Pioneer  Venus,  was  not  ground-based  planetary  radar  astronomy;  it 
was  space  exploration.  By  carrying  out  imaging  from  a  spacecraft,  radar  astronomer 
Gordon  Pettengill  had  erased  that  distinction.  That  distinction  no  longer  seemed  to 
describe  the  field,  as  Len  Tyler  and  Dick  Simpson  joined  the  Magellan  radar  team.  Tyler 
and  Simpson  had  not  abandoned  bistatic  radar  and  radio  occultation  experiments;  they 
had  simply  added  Magellan  radar  science  to  their  wide  range  of  research  interests. 

Unlike  the  Pioneer  Venus  mission,  or  the  Goldstone  and  Arecibo  facilities,  Magellan 
was  not  a  case  of  radar  astronomy  "Little  Science"  piggybacking  onto  a  Big  Science  facili- 
ty. Magellan  was  Big  Science.  Moreover,  its  single  scientific  instrument  was  a  radar.  The 
Smithsonian  push  to  have  Congress  fund  the  NEROC  440-ft  (134-meter)  dish  never 
reached  the  floor.  With  Magellan,  then,  Congress  considered  for  the  first  time  under- 
writing construction  of  a  facility  dedicated  primarily  to  planetary  radar  astronomy,  albeit 
one  whose  lifetime  was  rather  limited.  Magellan  illustrates  the  range  of  factors  that  influ- 
ence the  scientific  conduct  and  outcome  of  a  Big  Science  project.  The  change  of  admin- 
istration in  1980,  Cold  War  politics,  and  the  Challenger  accident,  as  well  as  ongoing  and 
changing  budgetary  and  technological  constraints  largely  shaped  the  scale  and  scope  of 
the  Magellan  mission  and  its  science. 

AllezVOIR! 

As  a  mission  concept,  Magellan  began  in  1972,  when  Danny  Herman,  the  head  of 
NASA  Advanced  Programs,  convened  an  informal  meeting  of  scientists,  including  Gordon 
Pettengill,  NASA  engineers,  and  representatives  of  several  key  aerospace  companies  at  the 


177 


1 78  TO  SEE  THE  UNSEEN 


Denver  division  of  Martin  Marietta  Aerospace,  to  discuss  putting  a  synthetic  aperture 
radar  on  a  spacecraft  to  Venus.1 

Subsequently,  two  NASA  laboratories,  Ames  Research  Center  and  JPL,  organized 
study  groups  and  began  planning  the  mission  and  appropriate  spacecraft  parameters.  At 
Ames,  Byron  Swenson  and  John  S.  McKay  put  together  a  study  group  that  worked  closely 
with  Martin  Marietta  Aerospace  in  planning  a  Venus  SAR  mapping  mission.  They  initially 
proposed  a  variation  on  Pioneer  Venus  with  an  elliptic  orbit.  During  the  period  1972 
through  1974,  Ames  Research  Center,  Martin  Marietta  Aerospace,  and  the  Environmental 
Research  Institute  of  Michigan  (ERIM) ,  which  had  been  involved  in  the  development  of 
airborne  SAR  systems  for  the  military  as  early  as  the  1950s,  carried  out  a  preliminary  eval- 
uation of  data  handling  problems  and  techniques.  The  1974  joint  report  of  Martin 
Marietta  Aerospace  and  the  ERIM  defined  the  project's  science  requirements  and  argued 
in  favor  of  a  circular  orbit.2 

At  the  same  time,  a  similar  study  was  underway  at  JPL  under  Louis  D.  Friedman.  In 
order  to  distinguish  their  Venus  project  from  that  of  the  Ames  group,  Friedman  and  Al 
Laderman  named  the  JPL  project  the  Venus  Orbiting  Imaging  Radar  (VOIR).  Laderman 
had  played  a  key  role  in  the  development  of  the  SEASAT  SAR.  He  and  Friedman  intend- 
ed the  acronym  to  connote  the  sense  of  the  French  verb  "voir,"  meaning  to  see.  VOIR  was 
going  to  "see"  the  (optically)  unseen  surface  of  Venus.  The  JPL  group  included  science, 
mission,  and  radar  people.  R.  Stephen  Saunders  was  the  principal  study  scientist.  Later,  he 
became  Magellan  Project  Scientist,  as  well  as  an  investigator  in  the  radar  group.  Saunders 
had  served  on  the  Viking  Mission  to  Mars,  before  carrying  out  NASA-funded  research  in 
planetary  geology  and  participating  on  the  Shuttle  Imaging  Radar  (SIR-A)  project. 

The  JPL  group  decided,  mainly  on  the  urging  of  Friedman,  to  use  a  circular  orbit.  A 
circular  orbit  would  simplify  the  radar  imaging  process.  The  radar  system  always  dealt  with 
the  same  parameters,  because  it  was  always  at  the  same  height  above  the  surface. 
Friedman  felt  that  simplifying  the  radar  versus  the  increased  propulsion  required  to 
achieve  a  circular  orbit  was  a  good  trade-off.  Although  the  added  propulsion  needed  to 
achieve  a  circular  orbit  would  increase  the  overall  cost  of  the  mission,  at  least  it  was  under- 
stood. The  synthetic  aperture  radar  was  a  new  technology;  an  elliptical  orbit  presented  a 
host  of  radar  and  data  processing  problems.  Jim  Rose's  study  group,  charged  with  plan- 
ning the  spacecraft,  proposed  a  vehicle  based  on  the  Mariner  system.  The  radar  study 
group  specified  a  radar  system  compatible  with  the  3-meter  (10-ft)  antennas  built  for  the 
Pioneer  missions  to  the  outer  solar  system.  Already,  the  goal  was  to  economize  by  using 
existing  technology.3 

Many  of  the  initial  assumptions  concerning  look  angle,  number  of  looks,  various  res- 
olution assumptions,  number  of  bits,  and  other  radar  system  parameters  came  under  crit- 
icism by  scientists  familiar  with  optical  data,  but  nonetheless  responsible  for  interpreting 
the  radar  data.  Those  criticisms  led  JPL  to  redesign  away  from  the  Mariner  approach  and 
to  exploit  internal  strengths  in  synthetic  aperture  radars  gained  through  the  SEASAT  pro- 
gram. Ultimately,  the  SEASAT  experience  gave  JPL  an  edge  over  its  competitors. 


1.  Herman,  telephone  conversation,  20  May  1994. 

2.  Memorandum,  Louis  D.  Friedman  toj.  C.  Beckman,  "VOIR,  Archeology,  10/79,"  Box  14  [hereafter 
Friedman-Beckman  Memorandum] ;  VOIR  Historical  Perspective,  "VOIR,  VOIR  Mission,  Briefing  to  NASA  Code 
S,  5/78,"  Box  8;  "VOIR,  A  Study  of  an  Orbital  Radar  Mapping  Mission  to  Venus,  Vol.  1,  9/73,"  Box  10;  "VOIR, 
Report,  A  Study  of  an  Orbital  Radar  Mapping  Mission  to  Venus,  Vol.  2,  9/73,"  Box  14;  "VOIR,  Report,  A  Study 
of  an  Orbital  Radar  Mapping  Mission  to  Venus,  Vol.  3,  9/73,"  Box  14;  and  "VOIR,  (NASA)  Correspondence 
VOIR  Mission  Study  Books,  10/77,"  Box  10,  JPLMM. 

3.  Friedman-Beckman  Memorandum;  VOIR  Historical  Perspective;  "VOIR,  Report,  A  Study  of  an 
Orbital  Radar  Mapping  Mission  to  Venus,  Vol.  2,  9/73,"  and  "VOIR,  Report,  A  Study  of  an  Orbital  Radar 
Mapping  Mission  to  Venus,  Vol.  3,  9/73,"  Box   14,  JPLMM;    V-Gram  no.  9   (October   1986):  3;  Campbell 
8  December  1993. 


MAGELLAN 


179 


SEASAT  was  an  Earth-orbiting  satellite  equipped  with  a  SAR  and  designed  for 
oceanographic  research.  In  its  1977  mission  and  systems  study,  JPL  proposed  the  SEASAT 
SAR  as  the  potential  design  base  for  the  VOIR.  JPL  argued  that  SEASAT  already  had  con- 
verted the  concept  of  a  spacecraft  imaging  radar  into  a  reality.  SEASAT  used  much  of  the 
conceptual  and  system  design  contained  in  the  original  JPL  VOIR  study,  while  later  VOIR 
studies  borrowed  heavily  from  the  SEASAT  experience.  JPL  also  contributed  SEASAT 
staff.  John  H.  Gerpheide,  SEASAT  satellite  system  manager,  became  VOIR/Magellan  pro- 
ject manager.  Anthony  J.  Spear,  sensor  manager  on  SEASAT,  became  VOIR/Magellan 
deputy  manager.4 

When  the  Science  Working  Group  convened  at  NASA  Headquarters  in  November 
1977,  NASA  already  had  selected  the  JPL  study.  NASA  charged  the  Science  Working 
Group  with  defining  the  major  scientific  objectives  and  rationale  for  a  Venus  orbiter 
equipped  with  a  radar  imager,  as  well  as  defining  other  experiments  and  defining  the 
radar-imaging  requirements  of  the  mission,  including  coverage,  resolution,  operating 
wavelength,  telemetry  data  rate,  and  data  processing.  The  Science  Working  Group  con- 
sidered the  merit  of  global  coverage  at  medium  resolution  and  imaging  selected  areas  at 
high  resolution. 

The  composition  of  the  VOIR  Science  Working  Group  drew  heavily  on  Pioneer 
Venus  alumni  and  from  both  the  planetary  radar  and  geology  communities  (Table  5) .  The 
planetary  radar  members  were  Don  Campbell  (Arecibo),  Dick  Goldstein  (JPL),  and 
Gordon  Pettengill  (MIT) ,  who  chaired  the  Group.  Harold  Masursky  and  Gerald  Schaber, 
both  astrogeologists  from  the  USGS,  Flagstaff,  and  both  participants  in  Pioneer  Venus, 
also  served  on  trie  Science  Working  Group. 


Table  5 

VOIR  (Magellan)  Science  Working  Group 

Scientist 

Institution 

Gordon  H.  Pettengill,  Chair 

MIT 

Harry  S.  Stewart,  Executive  Secretary 

JPL 

Donald  B.  Campbell 

NAIC,  Cornell 

Richard  M.  Goldstein 

JPL 

William  M.  Kaula 

UCLA 

Michael  C.  Malin 

JPL 

Harold  Masursky 
Norman  Ness 

US  Geological  Survey 
Goddard  Space  Flight  Center 

William  L.  Quaide,  Program  Scientist 
R.  Keith  Raney 

NASA  Headquarters 
Canada  Center  for  Remote  Sensing 

William  B.  Rossow 

Princeton  University 

R.  Stephen  Saunders,  Project  Scientist 

JPL 

Gerald  G.  Schaber 

US  Geological  Service 

Sean  C.  Solomon 

MIT 

David  H.  Staelin 

MIT 

A.  Ian  Stewart 

University  of  Colorado 

Robert  Strom 

University  of  Arizona 

G.  Leonard  Tyler 

Stanford  University 

The  Science  Working  Group  thus  became  a  forum  for  reinforcing  bridges  between 
planetary  radar  and  geology  scientists.  The  geologists  were  'Very  helpful  in  teaching  us 
radar  people  what  it  was  that  turned  them  on,  as  it  were,  while  we  were  helpful  to  them  in 
terms  of  optimizing  the  operation  of  the  radar,  so  as  to  provide  them  with  what  they  want- 
ed," Gordon  Pettengill  explained.  'This  interaction  shaped  the  specifications  that  turned 


4.  Friedman-Beckman  Memorandum;  VOIR  Historical  Perspective;  "VOIR,  (NASA)  Correspondence 
VOIR  Mission  Study  Books,  10/77,"  Box  10.JPLMM;  Robert  C.  Beal,  Venus  Orbiter  Imaging  Radar  FY7  7  Study  Report 
Radar  Studies,  Report  660-60  (Pasadena:  JPL,  2  May  1977),  pp.  5-1  through  5-18;  V-Gram  no.  9  (October  1986): 
2.  On  VOIR's  SEASAT  legacy,  see  also  Murray,  pp.  127-129. 


1 80  TO  SEE  THE  UNSEEN 


into  the  VOIR  and  later  the  Magellan  programs.  The  process  is  ongoing.  It  goes  on  even 
today."5 

NASA  was  particularly  mindful  that  the  Science  Working  Group  "take  full  account  of 
the  anticipated  capabilities  of  Earth-based  radar  systems  as  well  as  the  results  expected 
from  the  Pioneer  Venus  experiments."6  The  Committee  on  Planetary  and  Lunar 
Exploration  (COMPLEX)  of  the  Space  Science  Board,  and  in  particular  its  chairman, 
Caltech  professor  of  geology  and  geophysics  Gerald  J.  Wasserburg,  was  behind  that 
request.  The  request  was  logical,  Herman  judged  in  retrospect.  Given  the  high  cost  of 
VOIR,  why  should  NASA  and  the  Congress  commit  a  large  sum  of  money  to  a  space  mis- 
sion, when  Arecibo  could  acquire  the  same  imaging  data  for  far  less  money?  Having  the 
1977  VOIR  Science  Working  Group  assess  the  science  yield  from  a  large  ground-based 
radar  telescope,  like  Arecibo,  compared  to  the  science  yield  from  a  spacecraft  was,  in 
Herman's  words,  'Very  necessary  to  yield  off  the  devil's  advocate  question."7 

Herman  already  had  emphasized  to  the  initial  JPL  study  group  the  need  to  consider 
the  capabilities  of  Arecibo  for  undertaking  ground-based  radar  observations  of  Venus. 
The  chief  weakness  in  the  development  of  the  Venus  radar  orbiter  concept,  he  explained, 
was  the  belief  held  by  some  scientists  that  upgraded  ground  facilities  could  provide  data 
that  was  almost  as  good  at  a  far  lower  cost. 

By  1977,  range-Doppler  imaging  of  Venus  at  Goldstone  and  Arecibo  had  advanced 
considerably  thanks  to  the  refinement  of  interferometry  techniques  and  the  attainment 
of  finer  image  resolution.  At  Goldstone,  for  example,  Dick  Goldstein  used  a  radar  inter- 
ferometer, the  400-kilowatt  Mars  Station  linked  to  a  26-meter  Goldstone  DSN  antenna 
(DSS-13,  known  also  as  the  Venus  site)  located  about  22  km  to  the  southeast,  to  observe 
and  image  Venus  in  1972  for  the  first  time  and  subsequently  during  the  winter  of 
1973-1974  and  the  summer  and  fall  of  1975.  Over  that  period,  image  resolution  fell  from 
15  to  10  km,  although  in  some  instances  Goldstein  realized  resolutions  as  low  as  5  to  9  km 
in  the  East-West  direction  and  7  to  10.8  km  North  to  South.  In  1977,  Rayjurgens  and  Dick 
Goldstein  organized  a  three-station  interferometer;  the  Mars  Station  transmitted,  then  it 
and  two  26-meter  Goldstone  DSN  antennas  (DSS-12  and  DSS-13,  the  Echo  and  Venus 
sites,  respectively)  received.  The  three-station  data  yielded  image  resolutions  of  10  and 
even  down  to  8  km.8 

Planetary  scientists  R.  Stephen  Saunders  and  Michael  C.  Malin  of  the  JPL 
Planetology  and  Oceanography  Section  studied  the  Goldstone  Venus  images  and  con- 
cluded that  they  revealed  a  complex  and  varied  terrain.  They  found  degraded  impact 
craters  and  evidence  for  volcanism.  In  these  radar  images,  Beta  now  appeared  to  be  a  700- 
km-diameter  region  elevated  a  maximum  of  about  10  km  relative  to  its  surroundings  with 
a  60-by-90-km-wide  depression  at  its  summit.  Saunders  and  Malin  tentatively  identified 
Beta  Regio  as  a  shield  volcano.9 

Meanwhile  at  Arecibo,  the  radar  upgrade  from  UHF  to  S-band  increased  the  resolu- 
tion of  Venus  radar  images  abundantly.  In  1969,  with  the  old  430-MHz  radar  operating  in 
an  interferometric  mode,  Campbell,  Rayjurgens,  and  Rolf  Dyce  achieved  a  resolution  of 


5.  Pettengill  29  September  1993. 

6.  "VOIR,  (NASA)  Correspondence,  VOIR  Mission  Study  Books,  11/78,"  Box  13.JPLMM. 

7.  Herman,  telephone  conversation,  20  May  1994. 

8.  Herman,  telephone  conversation,  20  May  1994;  Rumsey,  Morris,  R.  Green,  and  Goldstein,  "A  Radar 
Brightness  and  Altitude  Image  of  a  Portion  of  Venus,"  Icarus  23  (1974):  1-7;  Goldstein,  R.  Green,  and  Rumsey, 
"Venus  Radar  \m*%es,"  Journal  of  Geophysical  Research  vol.  81,  no.  26  (10  September  1976):  4807-4817;  Goldstein, 
R.  Green,  and  Rumsey,  'Venus  Radar  Brightness  and  Altitude  Images,"  Icarus  36  (1978):  334-352;  Jurgens, 
Goldstein,  Rumsey,  and  R.  Green,  "Images  of  Venus  by  Three-Station  Radar  Interferometry — 1977  Results," 
Journal  of  Geophysical  Research  vol.  85,  no.  A13  (30  December  1980):  8282-8294. 

9.  Saunders  and  Michael  C.  Malin,  "Surface  of  Venus:  Evidence  of  Diverse  Landforms  from  Radar 
Observations,"  Science  196  (1977):  987-990;  ibid.,  "Geologic  Interpretation  of  New  Observations  of  the  Surface 
of  Venus,"  Geophysical  Research  Letters  4  (1977):  547-550. 


MAGELLAN 


181 


only  300  km.  An  improved  line  feed  brought  Venus  image  resolution  down  to  about  100 
km  in  1972,  the  last  Venus  observations  before  the  S-band  upgrade.10 

Concomitant  with  the  S-band  radar  upgrade,  the  NAIC  constructed  a  second  anten- 
na, a  30-meter  equatorially  mounted  reflector,  at  a  site  about  11  km  to  the  north- 
northeast  of  the  main  1,000-ft  (305-meter)  dish.  Data  taken  by  Campbell  and  Dyce  in  asso- 
ciation with  Gordon  Pettengill  during  the  Venus  inferior  conjunction  of  late  August  and 
early  September  1975  yielded  images  with  surface  resolutions  approximating  those  of 
Goldstone,  between  10  and  20  km.  Especially  interesting  was  a  detailed  view  of  Maxwell.11 


Figure  29 

Radar  image  of  Maxwell  Monies  made  at  Arecibo.  Surface  resolution  is  about  10  kilometers.  Maxwell,  which  measures  about 
750  kilometers  from  north  to  south,  includes  the  planet 's  highest  elevation:  1 1  kilometers  above  the  planetary  mean.  (Courtesy 
of  National  Astronomy  and  Ionosphere  Center,  which  is  operated  by  Cornell  University  under  contract  with  the  National  Science 
Foundation.) 

Thanks  to  hardware  improvements,  Don  Campbell  and  Barbara  Ann  Burns,  his  grad- 
uate student,  increased  the  resolution  of  Venus  images  to  five  km  during  the  1977  inferi- 
or conjunction.  For  her  doctoral  dissertation,  Burns  used  these  radar  images  to  study  cra- 
tering  on  the  planet.  She  and  Campbell  identified  over  30  circular  features  in  the  images 
and  tentatively  classified  them  as  craters,  but  the  level  of  resolution  did  not  permit  them 
to  ascertain  whether  their  origin  was  volcanic  or  impact.12  Also,  in  conjunction  with  USGS 


10.  Campbell,  Jurgens,  Dyce,  Harris,  and  Pettengill,  "Radar  Interferometric  Observations  of  Venus  at 
70-Centimeter  Wavelength,"  Science  170  (1970):  1090-1092;  NAIC  QR  Q2/1972,  pp.  3-4,  and  Q3/1972,  pp.  3-4. 

11.  Campbell,  Dyce,  and  Pettengill,  "New  Radar  Image  of  Venus,"  Science  193  (1976):  1123-1124. 

12.  Campbell  and  Barbara  Ann  Burns,  "Earth-based  Radar  Imagery  of  Venus,"  Journal  of  Geophysical 
Research  vol.  85,  no.  A13  (30  December  1980):  8271-8281;  Burns,  "Cratering  Analysis  of  the  Surface  of  Venus  as 
Mapped  by  12.6-cm  Radar,"  Ph.D.  diss.,  Cornell  University,  January  1982. 


182 


TO  SEE  THE  UNSEEN 


Figure  30 

Large  mosaic  of  Venus  made  from  Arecilm  radar  observations.  The  image  is  centered  on  longitude  320°  (see  Fig.  28).  Maxwell 
Mantes  is  the  large  white  area  in  the  upper  right  corner.  Isft  of  center  is  Beta  Regio.  (Courtesy  of  National  Astronomy  and 
Ionosphere  Center,  which  is  operated  by  Cornell  University  under  contract  with  the  National  Science  Foundation.) 


MAGELLAN  183 


geologist  Hal  Masursky,  Don  Campbell  and  Gordon  Pettengill  studied  images  of  Alpha, 
Beta,  and  Maxwell  made  from  combined  1975  and  1977  Arecibo  observations.13 

As  Campbell  and  fellow  radar  astronomers  using  the  upgraded  Arecibo  telescope 
achieved  resolutions  as  fine  as  5  kilometers  on  Venus  during  the  1977  inferior  conjunc- 
tion, the  high  resolution  invited  comparison  with  potential  space-based  radars.  In  order 
to  evaluate  the  capabilities  of  ground-based  radars  versus  orbiting  radars,  the  JPL  study 
group  brought  in  Thomas  Thompson.  Thompson  had  conducted  lunar  radar  work  at 
both  Arecibo  and  Haystack  for  the  NASA  Apollo  program.  As  a  result  of  Thompson's 
advice,  as  well  as  the  counsel  of  Danny  Herman,  Friedman's  study  group  framed  a  radar 
orbiter  mission  that  complemented,  rather  than  competed  with,  ground-based  radar 
observations  of  Venus.14 

Thompson  judged  that  the  best  ground-based  facility  would  be  the  upgraded 
Arecibo  telescope.  He  concluded  that  the  Earth-based  radar  was  a  very  powerful  tool  for 
mapping  the  surface  features  of  Venus.  "We  should  encourage  these  efforts  with  great 
vigor,"  he  wrote.  "It  seems  certain  that  the  Earth-based  mapping  will  show  many  features 
that  should  be  mapped  in  greater  detail  with  the  spacecraft.  Also,  the  spacecraft  will  be 
needed  to  map  the  hemisphere  of  Venus  which  is  not  pointed  toward  Earth  at  each 
inferior  conjunction."15 

The  combined  revolutions  of  Venus  and  Earth  around  the  Sun  lead  to  an  interval 
between  inferior  conjunctions  (known  as  the  synodic  period)  that  nearly  matches  the  spin 
rate  of  Venus  about  its  axis,  so  that  Venus  presents  almost  the  same  hemisphere  to  Earth 
observers  at  inferior  conjunction,  the  only  moment  when  radar  astronomers  have 
sufficient  signal-to-noise  ratio  to  image  the  planet.16  The  major  argument  in  favor  of  a 
spacecraft  imaging  mission  to  Venus  was  the  inability  of  ground-based  radars  to  image  the 
planet's  hidden  hemisphere.  A  major  upgrade  of  the  Arecibo  (or  Goldstone)  radar  could 
have  enabled  it  to  observe  and  image  Venus  at  orbital  points  before  and  after  inferior 
conjunction.  Such  an  upgrade  would  have  cost  less  than  the  Magellan  mission,  and  the 
improved  radar  would  have  been  able  to  carry  out  radar  research  on  a  variety  of  other 
solar  system  targets. 

In  1977,  NASA  asked  the  VOIR  Science  Working  Group  to  compare  the  costs  of 
acquiring  the  data  from  a  space-based  SAR  versus  from  a  ground-based  radar  telescope, 
like  Arecibo.  "We  knew  that  NASA  did  not  want  to  hear  that  it  would  be  cheaper,  even 
though  if  you  had  taken  what  it  actually  cost  to  do  Magellan  and  put  it  into  a  ground-based 
facility,  you  could  have  had  one  beautiful  ground-based  facility,  and  you  could  have 
endowed  a  fund  to  run  it  for  years,  forever  probably,  if  you  invested  the  money  properly," 
Gordon  Pettengill  explained. 

Moreover,  Pettengill  argued,  "As  an  investment  in  basic  research,  basic  astronomy,  a 
ground-based  observatory  would  be  a  much  wiser  investment  than  sending  Magellan  out 
there.  But  that  is  not  how  things  work.  The  money  is  available  for  the  Space  Station,  but 
not  available  for  any  ground-based  system  that  perhaps  would  do  some  of  the  same 
things."17 

Pettengill  assigned  the  tasks  of  comparing  altimetry  and  radar  imaging  capabilities 
of  ground-based  versus  space-based  radars  to  Don  Campbell  and  Dick  Goldstein.  They 


13.  Pettengill,  Campbell,  and  Masursky,  The  Surface  of  Venus,"  Scientific  American  243  (August  1980): 
54-65. 

14.  Thompson  29  November  1994;  Friedman-Beckman  Memorandum. 

15.  Venus  Orbiting  Imaging  Radar  Study  Team  Report  (Preliminary  Draft  (Pasadena:  JPL,  31  August  1972), 
pp.  22-28,  and  Friedman  and  J.  R.  Rose,  Final  Report  of  a  Venus  Orbital  Imaging  Radar  (VOIR)  Study  760-89 
(Pasadena:  JPL,  30  November  1973),  Pettengill  materials. 

16.  For  an  explanation  of  the  relationship  between  Venus's  spin  and  rotational  rates,  see  Goldreich  and 
Peale,  The  Dynamics  of  Planetary  Rotations,"  Annual  Review  of  Astronomy  and  Astrophysics  6  (1968):  287-320. 

17.  Pettengill  28  September  1993. 


1 84  TO  SEE  THE  UNSEEN 


completed  separate  reports,  with  Goldstein  considering  altimetry  and  Campbell  apprais- 
ing imaging  capabilities.  In  each  case,  they  compared  a  feasible  radar  design  (an  array 
located  probably  in  Puerto  Rico  to  have  the  planet  nearly  over  head)  with  the  current 
VOIR  design  requirements  and  judged  whether  the  radar  could  achieve  the  geologic 
objectives  of  the  Venus  mission  as  well  or  better  than  the  VOIR  design. 

Campbell  and  Goldstein  concluded  that  the  radar  array  could  do  the  VOIR  science 
(almost) .  The  ground-based  radar  would  not  observe  Venus  at  the  same  angles  of  inci- 
dence as  VOIR,  yet,  because  it  would  be  able  to  observe  Venus  at  a  distance  of  1.5  astro- 
nomical units,  it  could  see  the  side  of  Venus  hidden  at  inferior  conjunction.  The  100- 
meter  resolution  attainable  from  Earth  was  the  same  as  that  set  for  the  VOIR  mission. 
Moreover,  the  radar  array  could  do  the  job  for  less.  Pettengill  decided  to  not  include  their 
conclusions  in  the  Working  Group  report  "for  political  reasons."  He  believed  that  NASA 
had  no  interest  in  the  project,  and  that  the  conclusions  might  be  embarrassing.18 


Defining  the  VOIR 


In  1978,  VOIR  began  to  come  together.  The  concept  and  preliminary  design  studies 
completed,  the  time  had  come  to  begin  implementation  studies.  Radar  development 
began  in  1978  and  took  place  in  two  stages,  called  Phase  A,  lasting  from  June  through 
August  1978,  and  Phase  B,  October  1979  through  June  1980.  During  Phase  A,  JPL 
received  three  proposals  to  study  the  VOIR  SAR  and  selected  one  study  contractor, 
Goodyear  Aerospace  Corporation.  During  Phase  B,  JPL  received  three  proposals  and 
selected  two  study  contractors,  Goodyear  Aerospace  Corporation  and  Hughes  Aircraft 
Company.  Participation  in  Phase  B  studies  was  important  for  those  firms  wishing  to  build 
the  VOIR  radar;  implementation  phase  proposals  were  accepted  from  only  those  compa- 
nies participating  in  Phase  B.19 

The  mission,  its  spacecraft  and  radar  systems,  and  its  science  experiments  underwent 
many  revisions,  and  many  of  the  risks  foreseen  in  1978  materialized  before  Magellan  left 
Earth.  As  planned  in  1978,  the  Space  Shuttle  would  launch  the  VOIR  spacecraft  during 
the  period  May-June  1983.  VOIR  would  arrive  at  Venus  in  November  1983  and  spend  five 
months  in  orbit,  reduced  from  the  earlier  concept  of  a  19-month  mission.  JPL  considered 
the  possibility  of  the  launch  being  delayed  until  1984.  Such  a  delay  would  cause  an  over- 
lap with  Galileo,  complicate  scheduling  the  Deep  Space  Network,  and  raise  costs.  A 
delayed  launch  also  would  provide  an  opportunity  for  the  Soviet  Union  to  obtain  Venus 
SAR  images  before  the  United  States,  thereby  making  VOIR  radar  results  less  interesting, 
if  not  inconsequential. 

The  1978  version  of  VOIR  also  exploited  the  availability  of  extant  technology.  In 
order  to  economize  and  facilitate  selling  and  funding  the  project,  VOIR  would  use  com- 
ponents with  proven  performance  records  from  other  missions.  For  instance,  from 
Mariner  10  VOIR  borrowed  its  solar  array  and  louvers,  from  Voyager  its  spacecraft  elec- 
tronics, from  Pioneer  Venus  its  radar  altimeter,  and  from  SEASAT  its  synthetic  aperture 
radar.so 

JPL  hoped  to  make  VOIR  an  in-house  project.  NASA  had  other  ideas.  In  1979,  NASA 
stipulated  that  JPL  contract  out  both  the  radar  and  the  spacecraft  to  industry.  NASA  also 


18.  Pettengill  3  October  1993. 

19.  "VOIR,  Venus  Orbital  Imaging  Cost  Review,  6/78,"  Box  5;  "VOIR,  Venus  Orbiting  Imaging  Radar 
Review,  4/80,"  Box  10;  and  "VOIR,  VOIR  88,  Viewgraph  Presentation  to  NASA  Administrator,  11/87,"  Box  10, 
JPLMM. 

20.  'VOIR,  Status  Briefing  to  Committee  on  Planetary  and  Lunar  Exploration,  NASA  Headquarters, 
6/78,"  and  "VOIR,  VOIR  84,  Delayed  Launch  Option,  6/78,"  Box  3,  JPLMM. 


MAGELLAN  185 


specified  that  the  radar  would  have  a  single  individual,  from  NASA,  shoulder  the  respon- 
sibility of  making  it  work.  The  NASA  Headquarters  decision  had  an  immediate  impact  on 
VOIR  design.  The  JPL  in-house  effort,  which  came  to  an  end  in  February  1980,  had  con- 
centrated on  using  SEASAT  technology.  Now  an  industrial  design  would  serve.  In  order 
to  economize,  JPL  had  proposed  using  the  Galileo  circular  4.8-meter  antenna  for  both 
communications  and  the  SAR.  The  weight  of  the  Galileo  antenna  was  significantly  less 
than  that  of  a  competing  antenna  design.  Instead,  JPL  now  had  to  undertake  a  study  of 
the  competing  and  differing  antenna  patterns  proposed  by  the  contractors  Goodyear  and 
Hughes.2i 

In  planning  the  VOIR  radar  mapper,  the  Science  Working  Group  took  into  account 
the  resolution  of  the  images  sent  back  by  Mariner  9.  Those  images  had  revealed  for  the 
first  time  the  diversity  of  Martian  geologic  structures,  including  young  volcanoes,  liquid 
cut  channels,  and  large  canyons  of  possible  tectonic  origin  and  had  led  to  a  fundamen- 
tally new  understanding  of  the  nature  of  Mars.  The  VOIR  radar  mapper  had  to  have  com- 
parable or  better  resolution  than  Mariner  9.  Steve  Saunders,  project  scientist,  and  Gerry 
Schubert,  a  geophysicist  in  the  Department  of  Earth  and  Space  Sciences,  University  of 
California  at  Los  Angeles,  originated  the  high-resolution  design  requirement.22 

By  1978,  the  Science  Working  Group  had  defined  four  objectives  for  the  1984  VOIR 
mission:  1)  images  at  a  resolution  and  image  quality  equivalent  to  the  Mariner  9  Mars  mis- 
sion (100  percent  of  the  surface  at  mapping  resolution,  600  meters,  and  a  few  percent  in 
a  high  resolution  mode,  100  meters);  2)  a  global  topographic  map  of  the  planet;  3)  a 
global  map  of  the  gravity  field;  and  4)  new  investigations  of  the  atmosphere  and  exos- 
phere.  With  surface  exploration  taking  pride  of  place  over  atmospheric  experiments, 
VOIR  would  be  an  inverse  of  Pioneer  Venus. 

In  October  1978,  NASA  dissolved  the  Science  Working  Group  and  issued  an 
Announcement  of  Opportunity  requesting  proposals  for  VOIR  science  experiments  in 
three  categories:  1)  surface  and  interior  properties  of  the  planet  requiring  use  of  the  SAR 
and  altimeter,  2)  atmospheric  and  ionospheric  and  other  geophysical  experiments  requir- 
ing flight  instruments  other  than  the  SAR  and  altimeter,  and  3)  other  geophysical,  atmos- 
pheric, and  general  relativity  experiments  using  existing  spacecraft  subsystems.23 

Schooling  potential  users  of  Venus  radar  images  became  an  integral  part  of  the 
project.  Project  managers  understood  the  VOIR  radar  image  interpretation  community  as 
consisting  of  70  investigators  plus  130  associates  with  experience  interpreting 
photographs  of  the  Moon,  Mars,  and  Mercury.  In  order  to  inculcate  potential  users  in  the 
interpretation  of  radar  images,  JPL  planned  two  radar  image  interpretation  sessions,  ten- 
tatively scheduled  with  Goodyear,  to  take  place  in  1978  and  1979.  NASA  and  JPL  also  were 
to  sponsor  studies  based  on  the  analogy  between  Venus  radar  images  and  radar  images 
from  aircraft  and  Earth  satellites.24 

After  the  release  of  the  VOIR  Announcement  of  Opportunity,  experiment  proposals 
began  to  arrive  at  NASA  Headquarters.  Gordon  Pettengill  submitted  his  proposal  to  use 
the  synthetic  aperture  radar  to  image  Venus  in  February  1979.  Pettengill  defined  his  radar 
experiment  in  such  a  way  as  to  dovetail  radar  and  geological  science.  The  proposal 
focused  on  "those  processes  that  have  shaped  the  surface  of  Venus  and  that  have  led  to 
the  evolution  of  its  distinctive  atmosphere.  A  major  intermediary  in  achieving  this  goal  is 
the  preparation  of  a  global  map  of  the  surface  morphology  in  sufficient  detail  to  describe 
and  locate  the  major  geological  types  and  processes  exhibited  by  Venus." 


21.  Pettengill  28  September  1993;  "VOIR,  Venus  Orbiting  Imaging  Radar  Review,  4/80,"  and  "VOIR, 
Venus  Orbiting  Imaging  Radar  Review,  4/80,"  Box  10,  JPLMM. 

22.  A.  Gustaferro  to  W.  B.  Hanson,  8  May  1979,  "Magellan  Documentation,"  NHO;  Friedman-Beckman 
Memorandum;  VOIR  Historical  Perspective. 

23.  "VOIR,  (NASA)  Correspondence,  VOIR  Mission  Study  Books,  11/78,"  Box  13;  "VOIR,  Status 
Briefing  to  Committee  on  Planetary  and  Lunar  Exploration,  NASA  Headquarters,  6/78,"  Box  3;  and  NASA, 
Announcement  of  Opportunity  no.  OSS-5-78,  12  October  1978,  Box  13,  JPLMM. 

24.  "VOIR,  Venus  Orbital  Imaging  Cost  Review,  6/78,"  Box  3,  JPLMM. 


1 86  TO  SEE  THE  UNSEEN 


Pettengill's  proposal  emphasized  the  general  lack  of  knowledge  about  the  surface 
features  of  Venus.  Ground-based  observations  of  Venus,  Mariners  2,  5,  and  10,  the  Soviet 
Venera  missions,  and  Pioneer  Venus  all  provided  much  information  about  the  planet,  but 
the  proposal  argued,  'This  knowledge  is  heavily  weighted  toward  the  atmosphere  of  Venus 
and  its  interaction  with  the  solar  wind.  Comparatively  little  is  known  about  the  solid  sur- 
face or  the  interior  of  the  planet." 

Pettengill's  proposed  team  of  co-investigators  followed  closely  the  membership  of 
the  disbanded  Science  Working  Group.  Apart  from  Arecibo  radar  astronomer  Don 
Campbell,  most  co-investigators  came  from  MIT's  Center  for  Space  Research,  Pettengill's 
home  organization,  JPL,  and  the  U.S.  Geological  Survey.  Representing  the  USGS  were 
Pioneer  Venus  veteran  Hal  Masursky,  Gerald  Schaber,  then  assistant  chief  of  the  Branch 
of  Astrogeologic  Studies,  and  Laurence  A.  Soderblum,  chief  of  the  USGS  Branch  of 
Astrogeologic  Studies.  Again,  radar  and  planetary  geologists  associated  in  a  common 
endeavor. 

Among  the  geologists  who  ultimately  would  be  the  most  influential  on  the  VOIR  pro- 
ject was  James  W.  Head,  III,  an  associate  professor  in  the  Department  of  Geological 
Sciences  at  Brown  University.  Head  had  worked  at  NASA  Headquarters  for  Bell 
Communications,  a  telephone  company  subsidiary  that  provided  systems  analysis  and  sup- 
port, including  geologic  work  and  landing  site  selection,  to  NASA  on  the  Apollo  missions. 
His  research  interests  included  comparative  planetary  geology,  and  he  had  been  active  in 
the  geologic  interpretation  of  radar  data  from  the  Moon  for  some  years.  More  impor- 
tantly, as  we  shall  see,  he  was  a  guest  investigator  on  the  Soviet  Venera  15  and  16  missions. 

Pettengill  proposed  to  organize  his  co-investigators  into  Task  Groups  that  would  par- 
ticipate in  and  monitor  the  design  and  implementation  of  all  aspects  of  the  SAR  instru- 
ment, its  operation  during  flight,  and  the  reduction  of  imaging  and  ancillary  radar  data, 
as  well  as  the  subsequent  geological  and  geophysical  interpretation  of  the  data.25 

NASA  received  several  other  proposals,  but  they  were  not  successful  for  one  reason 
or  another.  H.  MacDonald,  a  radar  geologist  at  the  University  of  Arkansas,  proposed  inter- 
preting VOIR  data  in  the  form  of  a  radar  landform  atlas  of  Venus.  The  project  largely 
duplicated  the  mapping  contemplated  in  the  Pettengill  proposal.  Another  unsuccessful 
proposal  came  from  Charles  A.  Barth,  at  the  Laboratory  for  Atmospheric  and  Space 
Physics,  University  of  Colorado,  Boulder,  to  act  as  Principal  Investigator  on  the  airglow 
photometer  experiment.26  The  airglow  photometer  was  to  measure  the  horizontal  and 
temporal  characteristics  of  the  nightside  thermospheric  circulation.  That  proposal  failed 
for  reasons  external  to  VOIR,  as  we  shall  see. 

The  Stanford  Center  for  Radar  Astronomy  also  submitted  a  proposal;  it  succeeded. 
Proposing  radio  and  radar  experiments  on  NASA  space  missions  was  their  normal  mode 
of  conducting  scientific  research.  Len  Tyler,  Dick  Simpson,  and  John  F.  Vesecky  proposed 
to  study  radar  backscatter  from  the  surface  of  Venus,  in  order  to  infer  the  small-scale  phys- 
ical texture  of  the  surface,  and  to  relate  that  texture  to  the  large-scale  formations  visible 
in  the  VOIR  images.  Rather  than  create  a  separate  investigative  group,  the  Stanford 
researchers  proposed  that  they  participate  in  the  radar  group  with  Pettengill.27 


25.  "VOIR,  Scientific  Investigation  and  Technical  Plan,  Proposal  to  NASA,  2/79,"  Box  13,  JPLMM; 
V-Gramno.  11  (April  1987):  16;  V-Gramno.  13  (October  1987):  14;  and  V-Gramno.  11  (April  1987):  11. 

26.  'VOIR,  A  Proposal  to  NASA,  Submitted  by  University  of  Arkansas,  7/79;"  "VOIR,  Contract  Request 
for  Proposal  (APE)  Airglow  Photometer  Experiment,  5/81,  12/81;"  and  "VOIR,  Proposal  to  NASA,  for  Airglow 
Photometer  Experiment  for  the  VOIR  Mission,"  Box  13,  JPLMM. 

27.  'VOIR,  Proposal  to  the  NASA  Management  Section,  2/79,"  Box  13,  JPLMM. 


MAGELLAN  187 


The  Venus  Radar  Mapper 

Congress  already  had  voted  VOIR  a  new  start  in  the  NASA  budget,  when  Ronald 
Reagan  became  president  in  January  1981.  As  a  result  of  decisions  reached  in  the  early 
months  of  the  new  administration,  the  problems  foreseen  in  1978 — overlap  with  Galileo, 
complication  of  DSN  scheduling,  escalated  costs,  and  an  opportunity  for  the  Soviet  Union 
to  obtain  Venus  SAR  images  before  the  United  States — all  came  true.  National  politics 
now  took  its  turn  in  shaping  the  VOIR  mission.  Early  in  the  new  Republican  administra- 
tion, as  a  political  signal  that  the  new  president  was  serious  about  cutting  the  budget,  or 
at  least  the  civilian  portion  of  the  budget,  the  budget  czar  David  Stockman  pressured 
NASA  to  sacrifice  a  major  project.  NASA  chose  VOIR.28 

Failure  to  fund  the  project  until  fiscal  1984,  when  VOIR  became  a  new  NASA  start, 
led  to  a  postponement  of  the  launch  schedule  to  April  1988.  This  postponement  provid- 
ed the  Soviet  Union  an  opportunity  to  obtain  the  first  SAR  images  of  Venus.  In  this  case, 
the  Cold  War  rhetoric  of  the  White  House  did  not  have  its  equivalent  in  the  Space  Race. 
The  Space  Race  was  dead.  Starting  in  the  early  1970s,  as  the  United  States  withdrew  from 
the  war  in  Vietnam  and  the  Apollo  program's  objective  had  been  met  several  times  over, 
a  period  of  detente  started.  The  U.S.  and  U.S.S.R.  signed  an  accord  in  1972  to  allow  the 
exchange  of  scholars  between  the  two  countries.  A  decade  later,  however,  the  United 
States  let  the  accord  lapse  in  protest  over  the  Soviet  imposition  of  martial  law  in  Poland. 
Nonetheless,  many  U.S.  and  Soviet  scientists  sought  to  collaborate,  not  compete,  and  they 
did  so  with  the  tacit  approval  of  their  governments.  Cold  War  rivalry  and  competition  no 
longer  held  sway.29 

The  justification  for  canceling  VOIR  was  its  high  cost.  The  project,  conflated  into  an 
exploration  of  the  surface,  interior,  atmosphere,  and  ionosphere  of  Venus,  carried  a  total 
price  tag  of  $680  million.  NASA  andJPL  sought  ways  to  slash  that  price  tag  to  $200  to  $300 
million.30  In  the  opinion  of  Gordon  Pettengill,  the  project  "was  climbing  a  cliff.  The  pro- 
ject people  at  NASA  Headquarters  were  told  that  if  they  could  cut  the  cost  in  half,  they 
could  have  their  project.  In  other  words,  they  had  to  do  it  for  $300  million  instead  of  $600 
million.  So  an  ad  hoc  group  of  JPL  and  NASA  Headquarters  people  was  put  together  to 
study  ways  of  cutting  costs."31 

NASA  renamed  the  low-cost  reduced  mission  the  Venus  Radar  Mapper  (VRM)  ,32  The 
trick  was  to  lower  the  price  tag,  while  still  getting  the  science  done.  A  number  of 
approaches  were  suggested  and  taken,  not  all  of  which  were  technological,  such  as  the 
reduction  of  personnel  levels.  Many  of  the  cost-cutting  decisions  directly  reduced  the 
scientific  scope  of  the  mission.  For  example,  one  of  the  earliest  decisions  was  to  jettison 
all  scientific  experiments  that  did  not  use  the  radar.  Only  the  altimetry  and  imaging 
experiments,  which  used  the  radar  instrument,  and  the  gravity  experiment,  which  was  car- 
ried out  by  the  Deep  Space  Network,  remained.  Among  the  rejected  experiments  was  the 
airglow  photometer.33  As  Pettengill  pointed  out,  however,  "they  saved  $150  million  by 


28.  Pettengill  28  September  1993;  Saunders,  Pettengill,  Arvidson,  William  L.  Sjogren,  William  T.  K. 
Johnson,  and  L.  Fieri,  "The  Magellan  Venus  Radar  Mapping  Mission,"  Journal  of  Geophysical  Research  vol.  95,  no. 
B6   (1990):   8339;  Waff,  Jovian  Odyssey:  A  History  of  NASA's  Project  Galileo,  chapter  "Surviving  the  Reagan 
Revolution,"  pp.  8-10,  Waff  materials. 

29.  Henry  S.  F.  Cooper,  Jr.,  "A  Reporter  at  Large:  Explorers,"  The  New  Yorker  64  (7  March  1988):  50. 

30.  "VOIR,  Venus  Mapper  New  Start  Plans,  3/82,"  and  "VOIR,  Venus  Radar  Mapper,  A  Proposed 
Planetary  Program  for  1988,"  Box  10,  JPLMM. 

31.  Pettengill  28  September  1993. 

32.  For  a  brief  period  in  1981  and  1982,  project  documents  used  the  name  Venus  Mapping  Mission 
(VMM). 

33.  "VOIR,  Project  Management,  Venus  Orbiting  Imaging  Radar,  1981-82,"  Box  14;  "VOIR,  Venus 
Mapper  Briefing  to  NASA  Headquarters,  1/82,"  Box  10;  and  "VOIR,  Request  for  Proposal  for  VOIR  Synthetic 
Aperture  Radar,  7/81,  3/3,"  Box  13,  JPLMM. 


1 88  TO  SEE  THE  UNSEEN 


getting  rid  of  the  four  non-radar  experiments  that  originally  were  intended  for  the 
mission."34 

Throughout  various  iterations  of  the  project,  the  dimensions  of  the  high  and  low  res- 
olution radar  images  vacillated.  In  fact,  for  a  while,  the  high  resolution  detailed  images  of 
selected  surface  features  disappeared  entirely.  In  an  early  1981  iteration,  the  VRM  was  to 
map  at  least  70  percent  of  Venus  with  a  resolution  of  600  meters  and  take  high  resolution 
(150-meter)  data  over  about  one  percent  of  the  planet.  As  described  at  a  January  1982 
briefing  at  NASA  Headquarters,  however,  the  VRM  was  to  have  no  high  resolution  capa- 
bility and  would  image  only  70  percent  of  the  planet  with  a  resolution  of  better  than  one 
km.  At  a  February  1982  conference  held  at  JPL  for  the  selected  contractors,  Hughes 
(SAR)  and  Martin  Marietta  (spacecraft),  the  SAR  performance  parameters  called  for  cov- 
erage of  90  percent  of  the  planet  with  a  single  resolution  of  300  meters.  By  1984,  though, 
when  the  VRM  became  a  NASA  new  start,  the  baseline  performance  had  been  raised  to 
resolutions  of  215  meters  by  150  meters  and  480  meters  by  250  meters.35 

The  resolution,  and  consequently  the  science  that  the  VRM  would  achieve,  was  a 
trade-off  against  the  cost  of  the  project.  Only  by  lowering  overall  costs  did  JPL  and  NASA 
manage  to  put  together  a  mission  capable  of  high  resolution.  One  of  the  key  cost-reduc- 
tion approaches  was  to  "maximize  inheritance,"  a  term  that  meant  to  borrow  as  much 
technology  from  other  projects  as  possible.  Magellan  was  to  be  pieced  together  from  other 
NASA  projects. 

Among  the  projects  from  which  the  VRM  borrowed,  or  considered  borrowing,  were 
Viking,  Voyager,  Galileo,  and  ISPM  (International  Solar  Polar  Mission).  The  VRM  pro- 
posed borrowing  such  hardware  items  as  the  Voyager  3.7-meter  dish  antenna  for  its  syn- 
thetic aperture  radar,  Galileo's  tape  recorder,  and  Viking's  S-band  low-gain  antenna.  Also, 
JPL  suggested  using  NASA  standard  equipment  as  well  as  various  SEASAT  parts,  such  as 
sun  sensor  and  solar  array  drive  electronics  and  the  solar  array  actuators.36 

In  order  to  improve  the  VRM's  data  handling  capabilities,  JPL  modified  the  radar 
guidelines  in  order  to  use  the  Galileo  Golay  code,  rather  than  the  Golay  code  planned  by 
Hughes  (contractor  for  the  SAR) .  The  Galileo  Golay  code  and  a  restructuring  of  the  radar 
burst  header  format  (for  more  efficient  handling  by  the  Deep  Space  Network)  resulted  in 
a  considerable  saving  in  ground  software  costs. 

Another  key  decision  was  the  switch  from  a  circular  to  an  elliptical  orbit.  With  an 
elliptical  orbit,  the  parameters  of  the  radar  varied  as  a  function  of  the  spacecraft's  altitude 
above  the  planet's  surface.  Mapping  from  an  elliptical  orbit  eliminated  the  need  for  aer- 
obraking.  Aerobraking  is  a  technique  for  trimming  a  spacecraft's  orbit  by  having  it  pass 
repeatedly  through  a  planetary  atmosphere.  Its  use  would  reduce  the  amount  of  propul- 
sion needed  for  initial  orbit  insertion.  Aerobraking  offered  a  low-cost,  low-risk  option  that 
would  both  save  fuel,  and  therefore  mission  weight,  and  lower  mission  costs.37 

Using  digital  processing  to  simplify  the  electronics  was  a  significant  saver  of  money. 
Original  VOIR  planning  centered  on  analog  processing  for  the  radar,  but  by  1981  it  had 
become  clear  that  using  digital  circuitry  was  the  preferred  technology.  The  parameters  of 
an  analog  system  could  not  change  during  flight;  so,  aerobraking  and  a  circular  orbit  were 
necessities.  Digital  processing  allowed  the  radar  parameters  to  change  during  flight,  there- 
by tolerating  the  variations  of  a  less  expensive  elliptical  orbit.38 


34.  Pettengill  28  September  1993. 

35.  "VOIR,  Request  for  Proposal  for  VOIR  Synthetic  Aperture  Radar,  7/81,  3/3,"  Box  13;  "VOIR,  Venus 
Mapper  Briefing  to  NASA  Headquarters,  1/82,"  Box  10;  "VOIR,  Venus  Mapper  Conference  w/Hughes  and 
MMC,  2/82,"  Box  10;  and  "VOIR,  Project  Management  Report,  1984,  1/2,"  Box  14,  JPLMM. 

36.  'VOIR,  Venus  Mapper  Briefing  to  NASA  Headquarters,  1/82,"  Box  10;  "VOIR,  Venus  Mapper  New 
Start  Plans,  3/82,"  Box  10;  and  "VOIR,  Venus  Radar  Mapper,  A  Proposed  Planetary  Program  for  1988,"  Box  10, 
JPLMM. 

37.  "VOIR,  Project  Management  Report,  1984,  1/2,"  Box  14,  JPLMM. 

38.  Pettengill  28  September  1993. 


MAGELLAN 


189 


The  Microsymposia 


The  decisions  to  change  the  orbital  geometry,  use  digital  processing,  and  borrow 
technology  from  other  projects  lowered  project  costs  to  the  point  where  VRM  became  a 
new  NASA  start  in  1984.  As  a  result  of  the  postponed  launch  of  VRM,  Soviet  scientists 
gained  an  important  scientific  opportunity  to  image  Venus.  When  it  appeared  that  the 
United  States  would  launch  VOIR  on  schedule,  Soviet  scientists  decided  to  launch  their 
own  Venus  imaging  mission  only  if  the  United  States  did  not  send  a  Venus  radar  mapper 
before  1984.  Once  NASA  delayed  launch  of  the  VRM  beyond  1984,  Soviet  scientists  had 
to  move  forward  their  own  Venus  radar  mapper  very  quickly  in  order  to  seize  the  oppor- 
tunity. 

In  June  1983,  the  Soviet  Union  flew  two  spacecraft  equipped  with  radar  mappers  to 
Venus;  they  arrived  four  months  later.  Venera  15  and  16  covered  the  same  polar  region  of 
Venus  (30°  North  to  the  pole),  probably  on  the  assumption  that  one  of  the  spacecraft 
might  fail.  Their  goal  was  to  map  that  region  at  a  resolution  of  one  to  two  km  in  daily,  150 
by  7,000  km  strips  10°  to  the  side  of  the  orbital  track,  covering  a  total  area  of  115  million 
square  kilometers  by  the  time  the  main  mission  ended  in  July  1984.39 


fOTOKrtPTft. 


J1MCT      : 


Figure  31 

Radar  image  of  Venus,  near  Maxwell  Monies,  made  by  Venera  15  and  16.  (Courtesy  of  NASA,  photo  no.  88-H-8.) 


39.     Andrew  Wilson,  Solar  System  Log  (London:  Jane's,  1987),  pp.  112-113. 


190  TO  SEE  THE  UNSEEN 


Interpreting  the  images  from  the  Venera  15  and  16  mission  required  more  informa- 
tion about  Venus  surface  features  than  the  Soviet  Union  had  available.  Previous  Soviet 
missions  had  landed  only  in  limited  areas  of  the  planet.  Soviet  scientists,  desperately  in 
need  of  information,  turned  to  their  American  colleagues  to  exchange  Venus  data. 

Since  the  Apollo  era,  several  American  scientists  had  made  frequent  trips  to  Moscow 
and  to  international  meetings  where  they  met  Soviet  planetary  scientists.  Of  those 
American  scientists,  two  of  the  most  important  ones  for  the  Magellan  mission  were  Jim 
Head  of  Brown  University  and  Hal  Masursky  (USGS),  a  member  of  the  Pioneer  Venus  sci- 
ence team.  As  Venera  15  and  16  data  became  available,  its  value  to  future  American  explo- 
ration of  Venus,  especially  the  VRM  mission,  was  apparent,  and  a  parallel  American  inter- 
est in  collaboration  developed. 

On  25  March  1984,  Alexander  Basilevsky,  a  geologist  and  chief  of  the  Vernadsky 
Institute  Planetology  Laboratory,  and  Valery  L.  Barsukov,  director  of  the  Vernadsky 
Institute  (the  Soviet  equivalent  of  the  USGS),  presented  Venera  15  and  16  results  at  the 
Lunar  and  Planetary  Science  Conference  held  in  Houston.  United  States  scientists  appre- 
ciated that  the  Venera  15  and  16  SARs  had  yielded  mosaickable  images  of  a  large  part  of 
the  northern  hemisphere. 

COMPLEX,  the  Committee  on  Planetary  and  Lunar  Exploration  of  the  Space 
Science  Board,  requested  that  VRM  scientists  present  an  assessment  of  the  Venera  15  and 
16  accomplishments,  as  well  as  a  summary  of  VRM  capabilities  and,  if  deemed  desirable, 
ways  of  improving  VRM.  Gordon  Pettengill  presented  what  was  known  about  the  Soviet 
Venera  mission,  including  SAR  characteristics,  range  of  resolution,  and  coverage,  and  he 
compared  Venera  results  with  Arecibo  high  resolution  range-Doppler  images.  Having  reli- 
able images  of  Venus  was  vital  to  the  planning  of  the  VRM  mission.  Although  VRM  scien- 
tists already  had  data  with  which  to  plan  the  mission,  the  Venera  15  and  16  data  would 
have  added  important  information  on  the  northern  hemisphere.  Only  two  other  sources 
of  images  of  Cytherean  surface  features  were  available. 

One  source  was  Pioneer  Venus.  Its  radar  altimeter  measured  the  height  of  about 
90  percent  of  the  surface  at  roughly  75  km  intervals,  while  the  mapper  mode  furnished 
low  (20  to  40  km)  resolution  radar  images  of  only  the  equatorial  region.  Pioneer  Venus 
had  not  covered  the  northern  polar  region,  unlike  Venera  15  and  16.  Higher  resolution 
imaging  was  available  from  Arecibo,  the  second  source  of  Venus  surface  images.40  Arecibo 
covered  about  25  to  30  percent  of  the  planet  at  resolutions  around  2  to  4  km.  However, 
Arecibo  could  image  well  only  the  hemisphere  of  Venus  facing  Earth  at  inferior  conjunc- 
tion.41 

If  they  could  be  had  on  magnetic  tape  in  a  digital  format,  the  Venera  15  and  16  data 
would  have  assisted  VRM  planning  significantly.  The  data  did  become  available,  but  not 
through  any  political  maneuvering  by  the  corresponding  state  departments  or  other  high- 
level  official  channels.  The  exchange  of  scientific  results  between  Soviet  and  U.S.  scien- 
tists interested  in  the  surface  features  of  Venus  came  about  as  the  result  of  an  arrangement 
made  among  the  scientists  themselves  and  their  parent  institutions. 

The  1 1  March  1985  session  on  Venus  at  the  Lunar  and  Planetary  Science  Conference 
featured  Soviet  presentations  of  their  recent  interpretations  of  Venera  15  and  16  results 
by  Alexander  Basilevsky,  Valery  L.  Barsukov,  and  two  others  from  the  Vernadsky  Institute. 
Subsequently,  on  19-20  March  1985,  the  first  microsymposium  took  place  at  Brown 
University.  The  four  Soviet  scientists  reviewed  recent  results  of  Venera  15  and  16,  Arecibo, 
Pioneer  Venus,  as  well  as  future  Venus  missions  and  Venus  science  in  general.  Among 
those  attending  were  geologists  James  Head  and  Harold  Masursky  and  radar  astronomers 
Gordon  Pettengill  and  Don  Campbell  of  Arecibo. 


40.  "VOIR,  Project  Management  Report,  1984,  1/2,"  Box  14,  JPLMM. 

41.  Campbell  8  December  1993. 


MAGELLAN  191 


It  was  at  the  March  1985  microsymposium  that  James  Head  reported  that  the  Soviets 
appeared  to  be  receptive  to  the  idea  of  providing  some  of  their  data.  Preliminary  results 
indicated  that  the  Venera  SAR  radar  parameters  would  not  be  a  major  obstacle  to  their 
use  by  American  scientists.  Moreover,  both  Soviet  and  American  investigators  had  reached 
a  preliminary  agreement  on  the  choice  of  a  particular  small  feature  for  the  definition  of 
the  Venus  prime  meridian.  The  features  had  appeared  in  both  the  Arecibo  range-Doppler 
images  and  the  Venera  15  and  16  SAR  images.  Establishment  of  a  coordinate  system  was 
important  to  the  planned  VRM  cartography  efforts. 

In  November  1985,  Vladimir  Kotelnikov,  the  leader  of  Soviet  ground-based  radar 
astronomy  research,  then  head  of  Interkosmos,  delivered  to  Jim  Head  a  tape  with  one 
strip  of  digital  Venera  image  data  with  accompanying  altimetry.  Head  distributed  the  tape 
to  Saunders,  Pettengill,  Campbell,  and  Masursky  for  analysis.  They  had  no  difficulty  in  dis- 
playing the  image  using  conventional  American  image  processing  techniques. 

The  Soviet-American  agreement  to  exchange  Venus  data  was  underway.  The  agree- 
ment materialized  as  a  protocol  signed  in  1982  between  the  Governor  of  Rhode  Island 
(the  location  of  Brown  University)  and  the  Soviet  Academy  of  Sciences.  Under  the  agree- 
ment, one  microsymposium  per  year  was  to  take  place  in  each  country.  Traditionally,  the 
American  microsymposium  has  been  held  in  March  or  April  at  Brown  University;  while 
the  Soviet  meeting  takes  place  at  the  Vernadsky  Institute  in  Moscow  in  August.  James 
Head  organized  the  Brown  University  group,  and  Valery  Barsukov,  director  of  the 
Vernadsky  Institute,  organized  the  Soviet  group.  The  creation  of  the  microsymposia  owed 
much  to  the  fact  that  Head  was  a  guest  investigator  on  Venera  15  and  16.42 

The  Soviet  data  delivered  over  the  following  years  at  subsequent  microsymposia 
played  an  important  role  in  the  creation  of  planning  maps  for  the  VRM/Magellan  mis- 
sion. The  microsymposia  were  but  one  forum  within  which  geology  and  radar  communi- 
ties worked  together.  The  VRM  Radar  Investigation  Group  (in  charge  of  the  radar  sci- 
ence) was  another  forum  that  brought  the  two  communities  together  in  a  common  effort. 
The  Radar  Investigation  Group  (RADIG)  was  a  large  and  multifaceted  organization  typi- 
cal of  Big  Science.  In  order  to  more  effectively  coordinate  and  carry  out  VRM  and 
Magellan  science,  Pettengill  divided  the  group  into  smaller  subgroups  (Table  6). 

The  VRM  (and  later  Magellan)  Radar  Investigation  Group  combined  the  former 
Synthetic  Aperture  Radar  Group  and  the  Altimetry  Investigation  Group  of  the  VOIR  pro- 
ject. Gordon  Pettengill  headed  the  Radar  Investigation  Group  (RADIG).  Three  RADIG 
subgroups  dealt  with  mission  design,  while  three  other  subgroups  concerned  themselves 
with  scientific  interpretation.  These  last  three  subgroups  treated  cartography  and  geodesy, 
surface  electrical  properties,  and  geology  and  geophysics.  Geology  and  geophysics,  the 
largest  and  most  complex  area  of  scientific  interpretation,  consisted  of  even  smaller 
groups  dealing  with  volcanic  and  tectonic  processes;  impact  processes;  erosional,  deposi- 
tional,  and  chemical  processes;  and  isostatic  and  convective  processes.43 

Not  only  did  the  RADIG  bring  together  planetary  radar  and  geology  communities, 
but  it  illustrated  how  space  flight  science  groups  organized  Little  Science  to  function  as 
Big  Science,  if  only  on  a  temporary  basis  within  ephemeral  organizations.  Ordinarily,  in  a 
way  characteristic  of  Little  Science,  scientists  work  alone  at  a  university  or  technical  school 
with  a  small  budget  and  modest  laboratory  equipment.  NASA  space  missions  bring  these 
individual  scientists  together  and  make  them  function  in  ways  customarily  associated  with 
Big  Science,  mainly  as  part  of  a  large  group.  Any  given  scientist  works  as  a  member  of  two 
groups,  one  defined  by  a  flight  instrument  and  the  other  by  the  scientist's  discipline  or 


42.  Cooper,  "A  Reporter,"  p.  50;  Ford  3  October  1994;  Campbell  8  December  1993;  "VOIR,  Report 
Project  Management,  1985,"  Box  14,  JPLMM.  The  August  1991  microsymposium  was  delayed  until  November 
because  of  the  putsch. 

43.  V-Gram  no.  8  (24  March  1986) :  2-4. 


192 


TO  SEE  THE  UNSEEN 


Table  6 
Members  of  Magellan  Radar  Investigation  Group  (RADIG) 

Scientist 

Institution 

Raymond  E.  Arvidson 
Victor  R.  Baker 

Washington  University 
University  of  Arizona 

Joseph  H.  Binsack 
Donald  B.  Campbell 

MIT 
NAIC,  Cornell 

Merton  E.  Davies 

Rand  Corporation 

Charles  Elachi 

JPL 

John  E.  Guest 

University  of  London 

James  W.  Head,  III 

Brown  University 

William  M.  Kaula 

UCLA 

Kurt  L.  Lambeck 

Australian  National  University 

Franz  W.  Leberl 

Independent  Consultant 

Harold  C.  MacDonald 

University  of  Arkansas 

Harold  Masursky 

US  Geological  Survey 

Daniel  P.  McKenzie 
Barry  E.  Parsons 

Cambridge  University 
Oxford  University 

Gordon  H.  Pettengill 

MIT 

Roger  J.  Phillips 
R.  Keith  Raney 

Southern  Methodist  University 
Canada  Center  for  Remote  Sensing 

R.  Stephen  Saunders 

JPL 

Gerald  G.  Schaber 

US  Geological  Survey 

Gerald  S.  Schubert 

UCLA 

Laurence  A.  Soderblum 

US  Geological  Survey 

Sean  C.  Solomon 

MIT 

H.  Ray  Stanley 

NASA,  Wallops  Island 

Manik  Taiwan! 

Gulf  Research  and  Development 

G.  Leonard  Tyler 

Stanford  University 

John  A.  Wood 

Harvard-Smithsonian  Astrophysical 

Observatory 

subdiscipline.  Grouped  together  around  a  common  instrument,  scientists  jointly  design 
the  instrument  that  will  generate  their  data.  Grouped  together  around  a  common  scien- 
tific interest,  such  as  magnetospheres  or  geology,  scientists  jointly  utilize  data  derived  from 
the  operation  of  all  flight  instruments.  However  much  these  scientists  function  within  a 
Big  Science  organization,  the  organization  itself  is  defined  by  the  temporary  lifetime  of 
the  project.  In  the  end,  they  are  once  more  Little  Science. 

Osmosis 

In  December  1985,  NASA  Headquarters  notified  JPL  that  the  VRM  had  a  new  name, 
Magellan.  The  name  reflected  NASA's  general  plan  of  naming  major  planetary  missions 
after  famous  scientists  and  explorers  (Galileo,  Magellan,  Cassini).44  Ferdinand  Magellan 
had  been  a  Portuguese  navigator  and  explorer  who  led  an  expedition  into  the  Pacific 
Ocean  under  the  Spanish  flag. 

By  the  end  of  1985,  construction  of  the  Magellan  radar  instrument  was  underway. 
After  Hughes  Aircraft  Company  and  Goodyear  Aerospace  Corporation  completed  Phase 
B  studies  of  the  project  in  June  1980,  JPL  issued  a  Request  for  Proposals  for  the  synthetic 
aperture  radar  system,  including  the  antenna  design,  in  April  1981.  The  selection  of  the 
SAR  and  spacecraft  contractors  were  separate  processes.45 


44.  "VOIR,  Report  Project  Management,  1985,"  Box  14,  JPLMM. 

45.  "VOIR,  Venus  Orbiting  Imaging  Radar  Review,  4/80,"  Box  10,  and  "VOIR,  Request  for  Proposal  for 
VOIR  Synthetic  Aperture  Radar,  7/81,  1/3,"  Box  13,  JPLMM. 


MAGELLAN  193 


Hughes  had  hoped  to  turn  its  experience  with  the  Pioneer  Venus  orbiter  mapper 
into  an  advantage,  while  Goodyear  had  been  one  of  the  first  firms  to  commercialize  air- 
craft SAR  systems  to  study  the  Earth.  In  1983,  NASA  and  JPL  signed  contracts  with  Hughes 
and  Martin  Marietta  for  the  SAR  and  spacecraft.  Hughes  signed  the  definitive  radar  con- 
tract on  24  January  1984,  and  the  contract  was  executed  27  January  1984.  Throughout 
1985  and  1986,  Hughes  increased  the  number  of  employees  working  on  the  Magellan 
radar.  The  project  had  the  second  highest  priority  within  the  Hughes  Space  and 
Communication  Group,  behind  a  smaller  classified  project.46  Hughes'  Pioneer  Venus 
gambit  had  paid  off. 

Magellan  was  on  schedule  and  under  budget  when  the  Space  Shuttle  Challenger  blew 
up  on  28  January  198&.  The  tragedy  caused  a  serious  delay  in  the  Magellan  launch  sched- 
ule. In  fact,  the  disaster  adversely  affected  all  Shuttle  flights.  The  Shuttle  would  not  fly 
until  the  cause  of  the  Challenger  accident  was  determined  and  corrective  solutions  found 
to  prevent  future  repetitions  of  the  accident.  Only  then  would  a  new  Shuttle  flight  sched- 
ule be  drawn  up. 

In  February  1986,  Magellan  mission  personnel  began  to  appraise  probable  launch 
dates.  Realizing  the  uncertainties  of  the  Shuttle  launch  schedule,  they  investigated  two 
launch  windows  that  followed  the  approved  launch  period  in  April  1988.  One  was  between 
28  October  and  16  November  1989,  the  other  between  25  May  and  ISJune  1991.  In  each 
case,  Magellan  would  spend  eight  months  in  orbit  performing  its  prime  mission,  and  the 
mission  would  end  at  superior  conjunction,  in  November  1990  or  in  June  1992,  depend- 
ing on  the  launch  window.47 

A  delayed  launch  also  raised  the  likelihood  of  conflicts  with  the  Galileo  launch.  If 
Magellan  held  to  its  approved  launch  schedule  in  April  1988,  and  Galileo  delayed  13 
months,  then  coverage  conflicts  on  the  Deep  Space  Network  eased  considerably. 
Whatever  launch  window  Magellan  eventually  had,  conflict  with  the  Galileo  launch  and 
scheduling  of  the  Deep  Space  Network  would  have  to  be  taken  into  consideration. 
Further  complicating  the  launch  schedule  was  the  cancellation  in  June  1986  of  the 
Shuttle/Centaur,  which  was  to  launch  Magellan.  After  a  study  of  alternate  launch  vehicles, 
in  October  1986  NASA  settled  on  a  combination  of  the  Shuttle  and  a  launcher  known  as 
an  Inertial  Upper  Stage  (IUS)  and  assigned  Magellan  a  position  on  the  Shuttle  manifest 
for  April  1989.48 

The  change  required  reduction  of  the  spacecraft  mass,  as  well  as  new  structural  loads 
analyses.  In  order  to  undertake  the  analyses,  a  second  spacecraft  structure  was  needed  for 
static  load  tests.  The  only  one  available  was  on  the  Voyager  spacecraft  hanging  in  the 
Smithsonian  Air  and  Space  Museum  in  Washington.  NASA  made  arrangements  to  borrow 
the  Voyager  bus  from  the  museum  and  conducted  the  tests.49 

The  Challenger  accident  also  affected  Magellan's  use  of  Galileo  technology.  Because 
Magellan  launched  before  Galileo,  the  extra  Galileo  components  were  not  available. 
Ground  support  equipment  to  be  borrowed  from  Galileo  were  unavailable.  Now  the 
"spare  parts"  Magellan  was  to  borrow  from  Galileo  had  to  be  returned  to  Galileo  and  pur- 
chased new  for  Magellan. 

The  delay  of  Magellan  also  raised  the  cost  of  the  project.  The  total  dollar  impact, 
including  the  cost  of  hardware,  mission  design,  and  mission  operations,  was  estimated  to 
be  about  $150  million.  Gordon  Pettengill  summed  up  the  situation:  'That  disaster  need 
not  have  happened,  but  it  did;  it  was  just  one  of  those  things.  Magellan  would  not  have 
been  as  expensive,  if  we  had  launched  when  we  were  originally  planned  to  launch."50 


46.  Various  documents,  Box  6,  and  "VOIR,  Report  Project  Management,  1986,  1/2,"  Box  14,  JPLMM. 

47.  "VOIR,  Report  Project  Management,  1986,  1/2,"  Box  14,  JPLMM. 

48.  V-Gram  no.  10  (January  1987):  1  and  4. 

49.  V-Gram  no.  10  (January  1987):  1. 

50.  Pettengill  28  September  1993;  V-Gram  no.  10  (January  1987):  1. 


194  TO  SEE  THE  UNSEEN 


JPL  received  unofficial  notification  in  May  1986  from  NASA  Headquarters  that 
Magellan  had  slipped  to  the  October-November  1989  launch  window,  but  no  official 
launch  date  had  yet  been  established.  Nonetheless,  the  Magellan  project  proceeded  on 
the  assumption  of  that  launch  window.51 

Meanwhile,  the  collection  and  exchange  of  radar  data  for  the  assembling  of  maps  to 
be  used  in  planning  the  mission  proceeded.  The  Brown  University-Vernadsky  Institute 
microsymposia  continued  to  play  a  vital  role  in  the  exchange  of  scientific  information 
between  American  and  Soviet  scientists.  In  April  1986,  the  third  international  microsym- 
posium  on  Venus  took  place  at  Brown  University.  Valery  Barsukov,  Alexander  Basilevsky, 
and  four  other  Soviet  scientists  presented  preliminary  scientific  results  of  the  Venera  15 
and  16  missions  and  a  description  of  the  radar  system. 

The  Soviet  scientists  presented  the  Magellan  project  with  three  Venera  data  tapes 
consisting  of  unpublished  SAR  digital  data.  They  stipulated  that  the  data  be  used  strictly 
for  planning  the  Magellan  project;  it  was  not  for  scientific  publication  or  distribution, 
until  the  Soviet  scientists  had  published  the  information.  The  request  was  reasonable;  it 
protected  their  priority  of  discovery.  In  exchange,  the  Soviet  scientists  received  high  reso- 
lution digital  data  from  the  Viking  mission  to  assist  them  in  planning  their  Phobos  mis- 
sion to  Mars's  moon.52 

The  following  year,  Magellan  investigators  James  Head,  Steve  Saunders,  Hal 
Masursky,  Gerald  Schaber,  and  Don  Campbell  attended  a  microsymposium  held  11  to  15 
August  1986  at  the  Vernadsky  Institute  in  Moscow.  They  and  their  Moscow  colleagues 
exchanged  views  on  the  interpretation  of  Venus  data  from  Venera  15  and  16  and  Arecibo. 
The  Soviet  investigators  presented  the  Magellan  scientists  with  eight  tapes  of  Venera  15 
and  16  digital  radar  images  and  altimetry  profiles  for  use  by  the  Magellan  project  for  plan- 
ning purposes.53 

At  the  following  microsymposium  held  at  Brown  University  in  March  1987,  scientists 
debated  the  origin  and  evolution  of  volcanic  structures  and  deposits,  domes,  parquet  ter- 
rain, impact  craters,  ridge  and  linear  mountain  belts,  and  plate  tectonics.  Only  slight  con- 
sensus over  the  interpretation  of  features  emerged,  because  the  resolution  of  features  in 
Pioneer  Venus  images  (25  km)  and  Venera  15  and  16  images  (1-3  km)  was  sufficiently 
coarse  to  give  rise  to  ambiguities  in  interpretation.  Magellan's  higher  global  resolution 
(about  300  meters)  promised  to  resolve  many  questions  of  geologic  interpretation.  Soviet 
scientists  provided  the  Magellan  project  with  additional  Venera  15  and  16  digital  tapes;  in 
return  they  received  more  high-resolution  Viking  imaging  data  of  Phobos  and  the  surface 
of  Mars.54 

The  microsymposia  demonstrated  the  fruitful  cross-fertilization  of  planetary  geology 
and  radar.  In  order  to  facilitate  the  use  of  radar  data  by  geologists,  Magellan  Project 
Manager  John  Gerpheide,  Program  Scientist  Joseph  Boyce,  Principal  Investigator  Gordon 
Pettengill,  Project  Scientist  Steve  Saunders,  and  Science  and  Mission  Design  Manager 
Saterios  Sam  Dallas  formulated  preliminary  plans  in  July  1986  for  various  radar  work- 
shops. The  first,  to  be  held  in  1987,  was  to  cover  radar  operation  and  processing,  the  sec- 
ond the  interactions  between  radar  waves  and  planetary  surfaces,  and  the  third  interpre- 
tation of  SAR  images.  The  second  and  third  workshops  were  held  in  1988  and  1989, 
respectively.  The  sessions  were  open  to  Magellan  scientists  and  to  the  Planetary  Geology 
and  Geophysics  Program  investigators.  In  addition,  they  planned  one-day  Venus  science 
symposia  to  be  held  in  conjunction  with  other  project  meetings  for  each  year  between 
1987  and  1989. 


51.  "VOIR,  Report  Project  Management,  1986,  1/2"  and  "VOIR,  Report  Project  Management,  1986, 
2/2,"  Box  14,  JPLMM. 

52.  "VOIR,  Report  Project  Management,  1986,  1/2,"  Box  14,  JPLMM. 

53.  'VOIR,  Report  Project  Management,  1986,  2/2,"  Box  14,  JPLMM. 

54.  V-Gramno.  12  (July  1987):  1. 


MAGELLAN  195 


In  1987,  32  scientists  and  project  personnel  participated  in  the  field  trip  to  various 
sites  in  the  Mojave  Desert  and  Death  Valley.55  The  goal  was  to  compare  a  variety  of  geo- 
logic features  with  SAR  images  of  the  areas.  Steve  Wall,  Magellan  Radar  Experiment  rep- 
resentative, organized  the  field  trip,  which  Tom  G.  Farr  of  JPL's  Geology  and  Planetology 
Section  led.  Gerald  Schaber  of  the  USGS  contributed  to  the  technical  presentation  by 
sharing  his  knowledge  of  Death  Valley.56 

In  May  1988,  the  USGS  Flagstaff  hosted  another  field  trip,  which  was  incorporated 
as  part  of  the  quarterly  meeting  of  Magellan  scientists  and  project  staff.  The  major  objec- 
tive was  to  familiarize  participants  with  specific  radar  geology  targets  in  a  semi-arid,  rela- 
tively vegetation-free  environment.  The  trip  also  entailed  comparing  geologic  features 
with  X-band  and  L-band  SAR  images.  The  field  exercise  was  planned  and  led  by  Gerald 
Schaber,  Richard  Kozak,  and  George  Billingsley,  all  three  with  the  USGS  Flagstaff.57 

These  field  trips  helped  to  introduce  geologists  to  the  interpretation  of  radar  data. 
Geologists  learn  from  "hands-on"  experience,  but  that  kind  of  experience  is  impossible 
when  dealing  with  the  geology  of  Venus.  Radar  images,  moreover,  are  not  created  by  the 
reflection  of  light,  but  by  the  scattering  and  reflection  of  electromagnetic  waves.  They  can- 
not be  read  like  photographs,  and  radar  maps  cannot  be  read  like  ordinary  geological 
maps. 

In  order  to  fill  in  that  gap,  data  to  create  a  series  of  S-band  radar  images  of  the  lunar 
surface  were  collected  at  the  Arecibo  Observatory  between  1982  and  1992.  The  images 
were  made  at  various  angles  of  incidence  at  a  number  of  known  lunar  locations,  such  as 
the  Apollo  15  and  17  landing  sites,  Mare  Imbrium,  and  craters  Copernicus  and  Tycho,  in 
order  to  provide  experience  in  interpreting  surface  geology  in  radar  images.  Don 
Campbell,  assisted  by  Peter  Ford  of  MIT  and  later  by  Cornell  graduate  student  Nick  Stacy, 
made  the  observations  and  images  in  collaboration  with  Jim  Head  of  Brown  University. 
While  initial  image  resolutions  ranged  from  200  to  300  meters,  Nick  Stacy  brought  image 
resolution  down  to  25  meters  beginning  in  1990.  Elaborate  data  processing  techniques 
attempted  to  replicate  the  synthetic  aperture  radar  techniques  used  from  spacecraft  and 
aircraft.58 

As  Gordon  Pettengill  pointed  out,  the  workshops  were  not  the  main  path  for  geolo- 
gists to  learn  about  radar.  'The  people  who  attended  those  made  up  a  small  fraction  of 
the  overall  community.  That  route  is  an  exception  to  what  I  would  call  the  more  general 
experience.  Generally,  people  become  part  of  a  team,  and  they  work  with  radar  people, 
like  myself,  who  then,  by  a  process  I  would  call  osmosis,  pass  along  the  mystique  of  what 
is  going  on,  when  you  see  these  structures  on  a  radar  image,  how  to  interpret  them,  and 
what  to  look  out  for,  so  you  don't  make  errors." 

This  process  of  osmosis,  Pettengill  explained,  "is  the  best  way  to  go.  A  formal  course 
is  difficult.  They  call  them  workshops.  They  are  useful.  But  you  need  both.  You  need  the 
workshop  as  well  as  years  of  working  with  other  people  and  growing  used  to  what  you  are 
seeing."59 

That  process  of  osmosis  was  most  evident  at  the  Arecibo  Observatory,  where  Don 
Campbell  and  his  graduate  students  Barbara  Burns  and  Nick  Stacy  and  Research  Associate 
John  K.  Harmon,  collaborated  with  Jim  Head  and  other  geologists  at  Brown  University 
through  an  informal  accord  between  the  NAIC  and  Brown  University  beginning  around 
1980.  The  heart  of  the  accord  was  a  cooperative  effort  to  analyze  Arecibo  Venus  imagery. 


55.  "VOIR,  Report  Project  Management,  1986,  2/2,"  Box  14,  JPLMM. 

56.  V-Gramno.  11  (April  1987):  1. 

57.  V-Gmm  no.  15  (January  1989):  15. 

58.  Ford  3  October  1994;  Campbell  8  December  1993;  Nicholas  John  Sholto  Stacy,  "High-Resolution 
Synthetic  Aperture  Radar  Observations  of  the  Moon,"  Ph.D.  diss,  Cornell  University,  May  1993;  NAIC  QR 
Ql/1982,  Q4/1986,  Q2/1990,  Q4/1990,  and  Q3/1992. 

59.  Pettengill  29  September  1993. 


196  TO  SEE  THE  UNSEEN 


As  a  result  of  the  arrangement,  a  number  of  Brown  students,  such  as  Richard  W.  Vorder 
Brueggie  and  David  A.  Senske,  became  involved  in  the  analysis  of  Arecibo  radar  range- 
Doppler  imagery  and  wrote  their  theses  from  the  data. 

'The  effort  was  not  under  any  formal  agreement  between  the  NAIC  and  Brown 
University,"  Don  Campbell  explained.  "We  badly  needed  the  backing  of  a  planetary  geol- 
ogy group.  We  were  into  geology  at  this  point.  We  were  down  to  a  few  kilometers  of  reso- 
lution, and  they  were  extremely  enthusiastic.  Jim  Head  was  very  enthusiastic  and  had  a  lot 
of  students.  They  were  very  intent  on  getting  ready  for  the  Magellan  mission  and  spent  a 
lot  of  effort  on  both  the  Pioneer  Venus  and  Venera  data  sets."60 

The  Arecibo-Brown  arrangement  thus  fostered  the  geological  interpretation  of 
Venus  radar  images  well  before  Magellan  began  its  mapping  mission.  A  major  area  of 
interest  was  in  identifying  and  explaining  tectonic  activity  on  the  planet.  Some  of  the  1979 
high-resolution  Arecibo  radar  images  suggested  Earth-like  tectonic  features,  such  as  folds 
and  faults,  while  1983  Arecibo  radar  images  confirmed  the  presence  of  rifting  in  the 
southern  Ishtar  Terra  and  surrounding  plains  and  general  tectonic  activity  in  Maxwell 
Monies.61  Later  studies  examined  evidence  for  tectonic  activity  in  Beta  Regio,  Guinevere 
Planitia,  Sedna  Planitia,  and  western  Eistla  Regio  in  the  planet's  equatorial  region,  as  well 
as  in  the  southern  latitudes  around  Themis  Regio,  Lavinia  Planitia,  Alpha  Regio,  and  Lada 
Terra.fi2 

Don  Campbell  also  collaborated  with  Jim  Head's  group  in  searching  for  evidence  of 
volcanism.  Arecibo  radar  images  of  southern  Ishtar  Terra  and  the  surrounding  plains 
revealed  significant  details  of  volcanic  activity.  Images  made  from  data  gathered  at  Arecibo 
during  the  summer  of  1988  of  the  area  extending  from  Beta  Regio  to  the  western  Eistla 
Regio  furnished  strong  evidence  that  the  mountains  in  Beta  and  Eistla  Regiones,  as  well 
as  the  plains  in  and  adjacent  to  Guinevere  Planitia,  were  of  volcanic  origin.  Arecibo  radar 
images  of  the  southern  latitudes  showed  additional  evidence  for  past  volcanic  activity  on 
Venus.63 

The  study  of  cratering  on  Venus  started  by  Barbara  Burns  for  her  doctoral  thesis  con- 
tinued at  Arecibo,  too.  She  based  her  initial  analysis  on  data  collected  in  1977  and  1979. 
As  of  1985,  Burns  was  able  to  identify  only  two  features  that  exhibited  unambiguous  radar 
characteristics  that  could  tentatively  distinguish  them  as  either  volcanic  (Colette)  or 
impact  (Meitner)  in  origin.  Don  Campbell,  with  Jim  Head  and  John  Harmon,  continued 


60.  Campbell  8  December  1993. 

61.  Campbell,  Head,  John  K.  Harmon,  and  Alice  A.  Hine,  "Venus:  Identification  of  Banded  Terrain  in 
the  Mountains  of  Ishtar  Terra,"  Science  221  (1983):  644-647;  L.  S.  Grumpier,  Head,  and  Campbell,  "Orogenic 
Belts  on  Venus,"  Geology  14  (1986):  1031-1034;  Stofan,  Head,  and  Campbell,  "Geology  of  the  Southern  Ishtar 
Terra/ Guinevere  and  Sedna  Planitae  Region  on  Venus,"  Earth,  Moon,  and  Planets  38  (1987):  183-207;  R.  W. 
Vorder  Brueggie,  Head,  and  Campbell,  "Orogeny  and  Large-Scale  Strike-Slip  Faulting  on  Venus:  Tectonic 
Evolution  of  Maxwell  Monies,"  Journal  of  Geophysical  Research  vol.  95,  no.  B6  (1990):  8357-8381. 

62.  David  A.  Senske,  Campbell,  Stofan,  Paul  C.  Fisher,  Head,  Stacy,  J.  C.  Aubele,  Hine,  and  Harmon, 
"Geology  and  Tectonics  of  Beta  Regio,  Guinevere  Planitia,  Sedna  Planitia,  and  Western  Eistla  Regio,  Venus: 
Results  from  Arecibo  Image  Data,"  Earth,  Moon,  and  Planets  55  (1991):  163-214;  Bruce  A.  Campbell  and 
Campbell,  "Western  Eistla  Regio,  Venus:  Radar  Properties  of  Volcanic  Deposits,"  Geophysical  Research  Letters 
vol.  17,  no.  9  (1990):  1353-1356;  Senske,  Campbell,  Head,  Fisher,  Hine,  A.  de  Charon,  S.  L.  Frank,  S.  T.  Keddie, 
K.  M.  Roberts,  Stofan,  Aubele,  Grumpier,  and  Stacy,  "Geology  and  Tectonics  of  the  Themis  Regio-Lavinia 
Planitia-Alpha  Regio-Lada  Terra  Area,  Venus:  Results  from  Arecibo  Image  Data,"  Earth,  Moon,  and  Planets  55 
(1991):  97-161. 

63.  Stofan,  Head,  and  Campbell,  "Geology  of  the  Southern  Ishtar  Terra/Guinevere  and  Sedna  Planitae 
Region  on  Venus,"  Earth,  Moon,  and  Planets  38  (1987):  183-207;  Campbell,  Head,  Harmon,  and  Hine,  "Venus: 
Volcanism  and  Rift  Formation  in  Beta  Regio,"  Science  226  (1984):  167-170;  Campbell,  Head,  Hine,  Harmon, 
Senske,  and  Fisher,  "Styles  of  Volcanism  on  Venus:  New  Arecibo  High  Resolution  Radar  Data,"  Sei«n<*  246  (1989): 
373-377;  Campbell,  Senske,  Head,  Hine,  and  Fisher,  "Venus  Southern  Hemisphere:  Geologic  Character  and  Age 
of  Terrains  in  the  Themis-Alpha-Lada  Region,"  Science  251  (1991):  180-183;  Senske,  Campbell,  Head,  Fisher, 
Hine,  de  Charon,  S.  L.  Frank,  S.  T.  Keddie,  K.  M.  Roberts,  Stofan,  Aubele,  Grumpier,  and  Stacy,  "Geology  and 
Tectonics  of  the  Themis  Regio-Lavinia  Planitia-Alpha  Regio-Lada  Terra  Area,  Venus:  Results  from  Arecibo  Image 
Data,"  Earth,  Moon,  and  Planets  55  (1991):  97-161. 


MAGELLAN  197 


Burns's  crater  studies.  Images  made  from  the  data  collected  during  the  inferior  conjunc- 
tion of  1988  of  the  area  from  Beta  Regio  to  western  Eistla  Regio  revealed  a  low  density  of 
impact  craters  greater  than  15  km  in  diameter  in  that  region  compared  to  the  average 
density  for  the  higher  northern  latitudes.  These  crater  densities  suggested  that  the  plains 
were  geologically  younger  than  the  northern  regions.64 

Campbell,  with  graduate  student  Nick  Stacy  and  computer  software  manager  and 
part-time  radar  astronomer  Alice  Hine,  made  a  further  analysis  of  cratering  by  looking  at 
diameter-frequency  distributions  in  the  low  northern  latitudes  and  the  southern  hemi- 
sphere. The  Arecibo  investigators  found  that  the  average  crater  density  for  all  craters  in 
the  northernmost  quarter,  using  Venera  15  and  16  data,  was  1.27  per  million  square  kilo- 
meters, while  the  average  for  the  southern  hemisphere  (as  imaged  by  the  Arecibo  radar) 
was  0.95  per  million  square  kilometers.  The  different  crater  densities  suggested  that  the 
southern  latitudes  were  geologically  younger  than  the  low  northern  latitudes  imaged  by 
Venera  15  and  16.65 

Don  Campbell  also  participated  in  the  microsymposia  organized  by  Brown  University 
and  the  Vernadsky  Institute.  As  a  result,  he  also  came  to  collaborate  with  Alexander 
Basilevsky  and  other  Soviet  geologists  on  the  interpretation  of  Venera  15  and  16  results, 
and  that  collaboration  led  to  co-authorship  of  a  paper  with  combined  Vernadsky  Institute 
and  Brown  University  authors.66 

Don  Campbell's  osmotic  infiltration  of  the  scientific  community  interested  in  Venus 
typified  the  shifting  paradigm  of  ground-based  planetary  radar  astronomy  toward  geolo- 
gy. Further  facilitating  that  shift  was  the  availability  of  techniques,  hardware,  and  software 
at  Arecibo  that  yielded  high-resolution  range-Doppler  images  and  topographical  data. 
Image  resolution  improved  to  one  to  three  km  in  1983  and  to  1.5  km  in  1988,  the  last 
observations  made  before  the  arrival  of  Magellan  at  Venus. 

Because  Magellan  used  a  frequency  close  to  that  of  the  Arecibo  radar,  there  was  some 
concern  that  the  Arecibo  radar  might  contaminate  the  Magellan  data  or  endanger  the 
spacecraft,  so  Don  Campbell  did  not  pursue  Venus  mapping  after  1988.67  Nonetheless,  the 
participation  of  Arecibo  ground-based  investigators  in  Venus  radar  geology  illustrated  that 
the  marriage  of  radar  and  geology  was  not  limited  to  Magellan  and  space-based  radars. 


64.  Burns  and  Campbell,  "Radar  Evidence  for  Cratering  on  Venus,"  Journal  of  Geophysical  Research  vol.  90, 
no.  B4  (1985):  3037-3047;  Campbell,  Head,  Hine,  Harmon,  Senske,  and  Fisher,  "Styles  of  Volcanism  on  Venus: 
New  Arecibo  High  Resolution  Radar  Data,"  Science  246  (1989):  373-377. 

65.  Campbell,  Stacy,  and  Hine,  "Venus:  Crater  Distributions  at  Low  Northern  Latitudes  and  in  the 
Southern  Hemisphere  from  New  Arecibo  Observations,"  Geophysical  Research  Letters  vol.   17,  no.  9  (1990): 
1389-1392. 

66.  A.  T.  Basilevsky,  B.  A.  Ivanov,  G.  A.  Burba,  L.  M.  Chernaya,  V.  P.  Kryuchkov,  O.  V.  Nikolaeva, 
Campbell,  and  L.  B.  Ronca,  "Impact  Craters  on  Venus:  A  Continuation  of  the  Analysis  of  Data  from  the  Venera 
15  and  16  Spacecraft,"  Journal  of  Geophysical  Research  vol.  92,  no.  B12  (1987):  12,869-12,901;  Stofan,  Head, 
Campbell,  Zisk,  A.  F.  Bogomolov,  Rzhiga,  Basilevsky,  and  N.  Armand,  "Geology  of  a  Rift  Zone  on  Venus:  Beta 
Regio  and  Devana  Chasma,"  Geological  Society  of  America  Bulletin  101  (1989):  143-156. 

67.  Campbell  8  December  1993;  Burns,  "Cratering  Analysis  of  the  Surface  of  Venus,"  p.  1;  Stofan,  Head, 
and  Campbell,  "Geology  of  the  Southern  Ishtar  Terra/Guinevere  and  Sedna  Planitae  Region  on  Venus,"  Earth, 
Moon,  and  Planets  38  (1987):  183-207;  Richard  W.  Vorder  Brueggie,  Head,  and  Campbell,  "Orogeny  and  Large- 
Scale  Strike-Slip  Faulting  on  Venus:  Tectonic  Evolution  of  Maxwell  Montes,"  Journal  of  Geophysical  Research  vol.  95, 
no.  B6(  1990)  =8357-8381. 


198 


TO  SEE  THE  UNSEEN 


Figure  32 

Radar  image  of  the  central  portion  of  Alpha  Regio,  Venus,  at  a  resolution  of  about  1.5  km,  1988.  This,  and  the  image  in 
Fig.  33,  illustrate  the  fine  resolutions  achieved  by  the  ground-based  Arecibo  Observatory  radar  as  Magellan  began  imaging 
Venus.  (Courtesy  of  National  Astronomy  and  Ionosphere  Center,  which  is  operated  by  Cornell  University  under  contract  with 
the  National  Science  Foundation.) 


MAGELLAN 


199 


Figure  33 

Radar  image  of  Theia  Mons  in  Beta  Regio,  Venus,  at  a  resolution  of  2  km  made  from  data  gathered  with  the  Arecibo 
Observatory  radar,  1988.  (Courtesy  of  National  Astronomy  and  Ionosphere  Center,  which  is  operated  by  Cornell  University 
under  contract  with  the  National  Science  Foundation.) 


Magellan 


Throughout  1987  and  into  1988,  assembly  of  the  Magellan  spacecraft  and  final  test- 
ing of  the  radar  proceeded.  Hardware,  testing,  and  integration  costs,  coupled  with  an 
overall  tight  NASA  budget,  necessitated  cutbacks  and  deferrals  from  Magellan's  fiscal 
1988  budget  to  later  years.  Some  of  the  top  staff  transferred  to  other  projects.  Magellan 
Science  Manager  Neil  Nickle,  for  instance,  stepped  down,  and  Thomas  Thompson 
replaced  him.  Thompson  had  carried  out  lunar  radar  research  at  Arecibo  and  Haystack 
as  early  as  the  1960s,  and  he  was  still  making  lunar  observations  with  the  Arecibo  UHF 
radar  as  late  as  1987.  Also,  he  had  been  on  the  SEASAT  radar  team  in  the  1970s  and  more 
recendy  had  made  radar  observations  of  Mars  with  the  Goldstone  Mars  Station.68 


68.     Thompson  29  November  1994;  V-Gram  no.  15  (January  1989):  16;  V-Gram  no.  14  (May  1988):  2; 
NAICQR,  Q2/1987. 


200  TO  SEE  THE  UNSEEN 


In  September  1988,  a  month  ahead  of  schedule,  the  completed  craft  was  shipped  to 
Kennedy  Space  Center,  where  final  assembly  and  testing  took  place.  The  Magellan  launch 
date  was  moved  up  on  the  Shutde  manifest  from  October-November  1989  to  April-May 
1989  to  accommodate  the  launch  of  Galileo,  which  needed  to  go  to  Venus  for  a  gravity 
boost.  The  next  launch  window,  June  1991,  would  have  brought  Magellan  to  Venus  near- 
ly a  year  later  than  the  April-May  1989  opportunity.  Launching  six  months  earlier  also 
meant  that  Magellan  would  have  to  circle  the  Sun  one  and  a  half  times,  rather  than  the 
usual  one-half  circuit,  before  encountering  Venus.  Although  this  trajectory  took  Magellan 
almost  a  year  longer  to  reach  Venus  than  the  October-November  1989  opportunity,  it  still 
saved  a  year  over  the  June  1991  trajectory.  On  4  May  1989,  after  trouble  with  software,  a 
hydrogen  pump,  and  the  weather,  the  Shuttle  Atlantis  carried  Magellan  aloft  from 
Kennedy  Space  Center.  Magellan  became  the  first  planetary  mission  launched  by  the 
Space  Shuttle.  More  problems,  including  several  losses  of  signal,  plagued  Magellan's 
mission.69 

Magellan  entered  orbit  around  Venus  on  10  August  1990,  15  months  after  launch. 
On  15  August,  the  radar  sensor  was  turned  on  and  powered  up  in  preparation  for  the  first 
in-orbit  radar  test.  The  next  day,  during  the  radar  test,  the  spacecraft  lost  its  "heartbeat" 
and  protected  itself  by  invoking  on-board  fault-protection  routines.  Ground  control  noted 
this  immediately  by  the  terrifying  loss  of  signal.  Communications  were  re-established,  then 
lost  a  few  days  later.  After  a  shaky  start,  the  radar  began  mapping  on  15  September  1990. 

Mission  personnel  arranged  the  first  images  into  mosaics.  The  mosaics  covered 
about  500  km  segments  of  30  or  more  individual  image  strips.  One  of  the  first  mosaics  was 
centered  at  27°  South  latitude  and  339°  longitude  in  the  Lavinia  region  of  Venus.  It 
showed  three  large  impact  craters,  with  diameters  ranging  from  37  to  50  km.  The  craters 
showed  many  features  typical  of  meteorite  impact,  including  rough,  radar-bright  ejecta, 
terraced  inner  walls,  and  central  peaks.  Numerous  domes  of  probable  volcanic  origin 
were  visible  in  the  southeastern  corner  of  the  mosaic.  The  domes  ranged  in  diameter 
from  1  to  12  km;  some  had  central  pits  typical  of  volcanic  shields  or  cones.70 

During  its  243-day  prime  mission,  Magellan  amassed  more  imaging  data  than  all  pre- 
vious U.S.  planetary  missions  combined.71  Magellan  mapped  over  90  percent  of  the  plan- 
et's surface,  covering  regions  from  68°  South  latitude  to  the  North  pole.  The  images  were 
to  have  a  resolution  of  about  120  meters  near  the  equator,  degrading  slightly  to  about  190 
meters  near  the  poles  because  of  the  elliptical  nature  of  the  orbit.  Although  budgetary 
cuts  had  threatened  to  lower  the  resolution  of  Magellan  radar  images,  the  application  of 
advanced  digital  electronic  circuitry  had  restored  the  mission's  high  resolution  capability. 

SAR  data  from  each  orbit  was  to  be  processed  to  make  image  strips  about  350  pixels 
wide  in  the  across-track  dimension  by  220,000  pixels  in  the  along-track  direction.  Some 
1,852  such  SAR  image  strips  were  to  be  generated  byJPL's  Multimission  SAR  Processing 
Laboratory  during  the  primary  mission.  These  strips  were  to  be  sufficient  in  number  and 
coverage  to  encircle  the  planet,  with  overlap  of  adjacent  strips  even  in  lower  latitudes. 
Image  element  widths  were  75  meters  to  properly  preserve  both  the  along  and  cross-track 
spatial  resolutions. 

Each  strip  is  called  a  Full-Resolution  Basic  Image  Data  Record  or  F-BIDR.  In  total, 
the  1,852  F-BIDR  SAR  image  strips  formed  a  data  set  in  excess  of  100  billion  bytes.  The 
large  volume  and  the  unwieldy  width-to-length  ratios  for  the  data  made  them  unsuitable 
for  general  use.  Thus,  further  processing  was  necessary  to  produce  mosaicked  images 
(Mosaicked  Image  Data  Records  or  MIDRs)  that  could  be  more  readily  used  in  photo- 


69.  V-Gram  no.  15  (January  1989):  1;  V-Gram  no.  16  (August  1989):  1. 

70.  V-Gram  no.  18  (October  1990):  1-2. 

71.  V-Gram  no.  13  (October  1987):  1. 


MAGELLAN  201 


interpretative  studies  and  in  comparisons  with  the  other  Magellan  data.  Generating  full- 
resolution  mosaics  for  the  90  percent  of  the  planet  covered  by  F-BIDRs  created  an  enor- 
mous data  set,  severely  taxing  available  processing  facilities.  To  streamline  processing  and 
to  focus  efforts  toward  production  of  sets  of  mosaics  that  could  be  used  for  a  variety  of 
studies,  a  decision  was  made  to  compile  and  distribute  global  mosaics  from  compressed 
F-BIDR  data.  72 

The  USGS  converted  the  data  into  a  set  of  62  maps  in  the  standard  1:5,000,000  USGS 
planetary  series.  The  maps  showed  SAR  data  at  a  resolution  of  about  one  km,  and  they 
were  to  contain  altitude  contours.  In  addition,  a  set  of  about  200  photomosaics  were  to 
show  the  entire  mapped  area  of  the  planet  at  a  resolution  of  225  meters,  and  an  additional 
set  of  about  250  photomosaics  at  the  highest  resolution,  about  100  meters,  were  to  be  pre- 
pared for  selected  sections  of  the  planets.  Complementary  data  products  were  to  include 
a  topographic  map  at  about  10-km  surface  resolution  with  a  height  accuracy  of  better  than 
50  meters,  as  well  as  special  products  displaying  surface  roughness,  reflectivity,  brightness 
temperature,  and  emissivity.  Today,  the  radar  data  is  also  available  in  annotated  digital 
form  on  CD-ROMs.73 

Key  to  creating  these  and  other  Venus  images  was  an  accurate  knowledge  of  the  plan- 
et's pole  position  and  spin  vector.  An  analysis  by  Irwin  Shapiro  and  John  Chandler  of  1988 
Arecibo  radar  data  supplied  by  Don  Campbell,  Alice  Mine,  and  Nick  Stacy  provided  a  new 
pole  position,  accurate  to  better  than  3  km,  and  a  more  accurate  measurement  of  the 
planet's  rotational  period.74  Such  participation  in  NASA  space  missions  by  radar 
astronomers  as  "mission  support"  already  had  been  the  norm  for  two  decades. 

Don  Campbell  and  G-ordon  Pettengill  also  worked  closely  with  Stanford  scientists 
Len  Tyler  and  Dick  Simpson,  who  participated  on  the  science  team.  Tyler  chaired  the 
Surface  Electrical  Properties  (SEP)  Team,  composed  of  Tyler,  Campbell,  and  Gerald 
Schaber  (USGS).  Tyler,  Simpson,  and  John  Vesecky  used  the  altimeter  function  of 
Magellan's  radar  to  look  at  dielectric  constants  and  roughness,  to  study  the  top  meter  of 
Venus's  surface,  and  to  relate  its  structure  to  its  interaction  with  radar  waves.  They  trans- 
ferred their  data  to  a  CD,  with  the  intention  of  sending  copies  to  scientists  with  whom  they 


72.  V-Gram  no.  10  (January  1987):  9-10. 

73.  V-Gram  no.  8  (24  March  1986) :  2-3. 

74.  Magellan  Final  Science  Reports,  Report  D-11092  (Pasadena:  JPL,  22  October  1993),  p.  25;  Shapiro, 
Chandler,  Campbell,  Hine,  and  Stacy,  "The  Spin  Vector  of  Venus,"  The  Astronomical  Journal  100  (1990): 
1363-1368.  See  also  the  analysis  done  at  Goldstone:  Slade,  Zohar,  and  Jurgens,  "Venus:  Improved  Spin  Vector 
from  Goldstone  Radar  Observations,"  The  Astronomical  Journal  100  (1990):  1369-1374. 


202 


TO  SEE  THE  UNSEEN 


Figure  34 

Radar  image  of  Venus  at  65  degrees  east  longitude,  along  the  western  edge  of  Maxwell  Mantes,  made  from  Magellan  observa- 
tions. The  sloping  edge  of  Maxwell  Mantes,  the  highest  mountain  on  Venus,  is  visible  along  the  right  hand  side  of  the  image. 
The.  imaged  area  is  300  km  wide.  (Courtesy  of  NASA,  photo  no.  90-H-752.) 

collaborated,  such  as  Don  Campbell,  Peter  Ford,  and  Gordon  Pettengill,  as  well  as  inter- 
ested geologists.75 

Typical  of  Big  Science  projects,  Magellan  thus  became  a  meeting  ground  for  differ- 
ent scientific  disciplines  and  subdisciplines.  Its  broad  tent  covered  traditional  ground- 
based  radar  astronomy  and  Stanford  bistatic  radar  astronomy,  as  well  as  planetary  geolo- 
gy. Magellan  accelerated  cross-fertilization  between  planetary  geology  and  radar  that 


75.  Simpson  10  May  1994;  Simpson  and  Tyler,  "Venus  Surface  Properties  from  Magellan  Radio  and 
Radar  Data,"  V-Gram  18  (October  1990):  12-18.  For  the  results,  see  Tyler,  Ford,  Campbell,  Charles  Elachi, 
Pettengill,  and  Simpson,  "Magellan:  Electrical  and  Physical  Properties  of  Venus'  Surface,"  Science  252  (1991): 
265-270;  Tyler,  Simpson,  Michael  J.  Maurer,  and  Edgar  Holmann,  "Scattering  Properties  of  the  Venusian 
Surface:  Preliminary  Results  from  Magellan, "  Journal  of  Geophysical  Research  97  (1992):  13,115-13,139.  Pettengill 
and  Ford  also  produced  dielectric-constant  and  roughness  maps  to  accompany  the  global  topography  and  emis- 
sivity  data  they  produced.  The  Stanford  investigators  used  different,  but  complementary,  algorithms  that  com- 
bined the  altimetry  and  imaging  SAR  data  to  obtain  estimates  of  surface  roughness  and  dielectric  constant.  Both 
data  sets  were  made  available  on  CD-  ROMs. 


MAGELLAN  203 


made  radar  results  (mainly  range-Doppler  images  and  topography)  more  accessible  to  a 
larger  community  of  investigators.  As  Don  Campbell  reflected:  "We  are  suddenly  much 
more  respectable  than  we  used  to  be!  I  don't  want  to  characterize  what  people  thought  of 
us,  but  to  some  degree  I  suspect  that  we  were  regarded  as  a  litde  bit  of  the  fringe.  Radar 
astronomy  was  regarded  as  a  messy  and  expensive  occupation.  We  came  up  with  good 
stuff,  but  how  we  did  it  was  not  all  clear!"76 

As  radar  astronomers  grew  closer  to  planetary  geology,  they  sought  out  their  new 
audience  in  new  scientific  settings.  Radar  astronomers  still  discussed  their  findings  at 
meetings  of  the  IAU,  the  AAS  Division  for  Planetary  Science,  and  URSI,  but  also  at 
American  Geophysical  Union  (AGU)  meetings.  General  science  and  astronomy  journals, 
such  as  Science  and  The  Astronomical  Journal,  and  even  more  so  the  specialized  planetary  sci- 
ence journals,  such  as  Icarus  and  Earth,  Moon,  and  Planets,  remained  forums  for  publica- 
tion. In  addition,  because  they  had  added  the  planetary  geology  community  to  their  audi- 
ence, radar  astronomers  now  published  in  the  Journal  of  Geophysical  Research  and 
Geophysical  Research  Letters. 

The  new  audience  also  shaped  radar  astronomy  funding,  although  less  so  at  the 
Arecibo  Observatory,  where  the  NSF-NASA  agreement  assured  an  annual  budget  for 
radar  astronomy  research.  Researchers  elsewhere  seeking  NASA  money  for  planetary  sur- 
face studies  faced  the  demands  of  the  NASA  planetary  geology  program.  When  Dick 
Simpson  or  Len  Tyler,  for  instance,  applied  for  geology  program  funds  to  study  planetary 
surfaces,  geologists  reviewed  their  proposals.  One  of  the  frequent  comments  by  those 
reviewers  was  that  the  proposal  should  include  a  geologist  on  the  science  team.  As  a  result, 
Dick  Simpson  approached  USGS  Menlo  Park  geologist  Henry  Moore  to  collaborate  with 
him.77  Through  their  role  as  proposal  reviewers,  then,  planetary  geologists  began  to  shape 
radar  astronomy  research  proposals. 

Throughout  the  1970s,  as  planning  for  Magellan  and  the  flight  of  Pioneer  Venus 
took  place,  the  field  of  radar  astronomy,  measured  in  terms  of  active  practitioners  and 
telescopes,  grew  smaller.  In  1980,  the  Arecibo  Observatory  was  essentially  the  sole  active 
telescope;  it  supported  four  active  investigators.  In  contrast  to  this  Little  Science  reality 
stood  the  Big  Science  of  Magellan.  Around  a  single  radar  instrument,  the  big-budget, 
multi-year  mission  organized  individual  scientists  into  groups  that  crossed  turf  boundaries 
(radar  astronomy  versus  Stanford  "space  exploration")  and  that  fostered  common  inter- 
ests among  fields  (planetary  radar  and  geology  scientists) . 

Although  the  exploration  of  planetary  surfaces  with  space-based  radars  seemed  to 
invigorate  radar  astronomy,  the  space-based  approach  has  its  limits  in  an  era  of  budgetary 
limits.  Cassini  probably  will  be  the  last  mission  to  carry  a  radar  experiment  into  space.  As 
currently  conceived,  Cassini  will  explore  Saturn's  cloud-covered  moon,  Titan,  with  a  SAR. 
No  other  solar  system  bodies  have  impenetrable  atmospheres  that  lend  themselves  to 
radar  investigation.  The  problem  of  transmitting  data  back  to  Earth  at  distances  beyond 
the  orbit  of  Saturn  is  a  major,  though  not  insurmountable  obstacle  (as  Voyager  has 
shown).  The  use  of  laser  rather  than  radar  altimeters  on  future  missions  means  that  mod- 
ifying the  altimeter  to  carry  out  imaging,  as  was  done  on  Pioneer  Venus,  has  reached  its 
technological  limit  (although  military  research  may  well  yield  a  laser  altimeter  capable  of 
imaging). 

However,  the  most  formidable  barrier  to  any  future  mission  is  the  shrinking  space 
and  national  budgets.  The  Voyager,  Galileo,  and  Magellan  spacecraft  were  expensive,  cost- 
ing $2-3  billion,  huge,  standing  seven  meters  high,  as  tall  as  most  homes,  and  heavy, 
weighing  several  tons.  Galileo,  for  example,  weighed  three  tons.  In  order  to  accommodate 
a  future  of  smaller  budgets,  NASA  has  initiated  the  Discovery  program,  in  which  low-cost 
($150  million  limit)  small,  lightweight  spacecraft  with  limited  scientific  objectives  carry 


76.  Campbell  9  December  1993. 

77.  Simpson  10  May  1994. 


204  TO  SEE  THE  UNSEEN 


out  solar  system  exploration.  One  problem  with  this  approach  is  that  missions  to  Jupiter 
and  Saturn  or  beyond  simply  cost  too  much  to  fit  the  budgetary  limits  set  for  Discovery 
missions.78  Such  is  the  price  of  practicing  science  on  a  large  scale. 

Magellan  also  effectively  ended  ground-based  radar  observations  of  Venus.  Although 
a  few  experiments  were  still  possible,  for  example,  the  detection  of  rain  on  Venus  with  an 
X-band  radar  or  polarization  studies  of  surface  scattering  properties,79  they  likely  will  not 
achieve  prominence.  Indeed,  Don  Campbell,  who  has  spent  his  scientific  career  doing 
radar  studies  of  Venus,  volunteered  to  Nick  Renzetti  of  JPL  at  the  Lunar  and  Planetary 
Conference  at  Houston  in  1985  that  he  was  not  likely  to  do  any  more  Venus  observations; 
instead,  he  planned  to  concentrate  on  asteroid  and  comet  experiments.80 

Campbell  typified  the  new  direction  that  planetary  radar  astronomy  began  taking 
after  1975,  when  the  Arecibo  and  Goldstone  upgraded  radars  became  available. 
Technology  still  drove  planetary  radar  astronomy.  New  and  better  instruments  and  inno- 
vative techniques  allowed  radar  astronomers  to  solve  problems  previously  unsolvable  and 
to  detect  and  study  solar  system  objects  never  before  explorable  with  radar.  The  explo- 
ration of  those  objects  in  turn  presented  unusual  radar  characteristics  that  led  radar 
astronomers  to  solve  new  scientific  problems.  The  dynamic  resonance  between  radar  tech- 
niques (epistemological  issues)  and  problem  solving  (scientific  questions)  thus  remained 
at  the  heart  of  planetary  radar  astronomy.  Nonetheless,  despite  a  short  spurt  of  growth 
following  the  inauguration  of  the  upgraded  Arecibo  and  Goldstone  radars,  by  1980  the 
planetary  radar  literature  had  reached  a  plateau  of  activity;  the  field  had  reached  the 
limits  to  its  growth. 


78.  Richard  A.  Kerr,  "Scaling  Down  Planetary  Science,"  Science  264  ( 1994) :  1244-1246. 

79.  Goldstein  14  September  1993;  Pettengill  4  May  1994.  Bill  Smith  tried  to  look  for  rain  in  Venus' 
atmosphere  at  the  Haystack  Observatory  in  the  1960s.  Smith  29  September  1993. 

80.  GSSR  Min.  28  March  1985. 


Chapter  Eight 

The  Outer  Limits 


Planetary  radar  astronomy  was  a  problem-solving  activity,  an  algorithm  in  search  of 
a  problem.  Its  fundamental  driving  force  was  the  dynamic  interaction  between  radar  tech- 
niques and  the  kinds  of  problems  radar  astronomy  solved.  Improvements  in  radar  hard- 
ware and  innovative  radar  techniques,  such  as  range-Doppler  mapping,  allowed  radar 
astronomy  to  solve  scientific  problems  of  interest  to  astronomers  and  geologists. 
Conversely,  problem-solving  could  bring  attention  to  radar  techniques  and  properties  pre- 
viously neglected  or  little  used,  such  as  the  polarization  of  echoes. 

The  institutional  and  financial  linking  of  radar  astronomy  to  NASA  at  Arecibo  and 
JPL  gave  the  field  a  mission-oriented  cast.  The  justification  for  funding  was  the  field's 
utility  to  NASA  space  missions,  and  access  to  Goldstone  antenna  time  required  specific 
mission  support.  Beginning  with  Viking,  participation  in  NASA  missions  also  brought 
ground-based  radar  astronomers  into  closer  collaboration  with  the  radar  scientists  at  the 
Stanford  Center  for  Radar  Astronomy.  The  distinction  made  in  the  1960s  between 
ground-based  planetary  radar  astronomy  and  Stanford's  "space  exploration"  held  less  and 
less  meaning. 

Planetary  radar  astronomy  after  about  1975  also  remained  above  all  else  a  science 
driven  by  technology,  namely,  access  to  radars  with  the  transmitter  power  and  antenna 
and  receiver  sensitivity  to  explore  the  planets.  Without  those  radars,  radar  astronomy 
could  not  exist.  The  decline  of  radar  astronomy  at  JPL  followed  directly  from  the  deteri- 
orating state  of  the  Goldstone  radar.  Improvements  in  radar  hardware,  on  the  other  hand, 
drove  planetary  radar  forward. 

Additional  transmitter  power  and  receiver  sensitivity  meant  access  to  previously 
unexplored  targets.  The  orbit  of  Mars  defined  the  outer  reaches  of  planetary  radar  astron- 
omy until  1975,  when  both  the  Arecibo  and  Goldstone  radars  underwent  upgrades  that 
significantly  enhanced  their  value  as  research  tools,  as  discussed  in  Chapter  Four.  For  the 
first  time,  the  Galilean  satellites  of  Jupiter,  the  rings  of  Saturn,  cometary  nuclei,  and  a 
number  of  both  Earth-approaching  and  mainbelt  asteroids  came  within  reach  of  those 
planetary  radars.  Those  targets  represent  considerable  radar  distances;  the  round-trip 
radar  time  to  the  moons  of  Jupiter  is  about  1  hour  and  12  minutes  and  to  Saturn's  rings 
around  2  hours  and  15  minutes. 

Meanwhile,  the  planetary  radar  astronomy  community  remained  small,  and  Arecibo 
and  Goldstone  were  the  only  active  research  facilities.  Arecibo  was  still  a  major  NSF-fund- 
ed  center  for  radio  astronomy  and  ionospheric  research.  On  the  other  hand,  funded  by 
NASA,  not  the  NSF,  and  associated  with  exploration  of  the  solar  system,  radar  astronomy 
there  occupied  a  small,  peculiar  niche,  a  niche  that,  nonetheless,  furnished  a  research 
facility  for  both  Cornell  and  MIT  graduate  students  to  be  trained  as  future  radar 
astronomers. 

In  contrast,  Goldstone  did  not  train  graduate  students.  The  radar  astronomers  at  JPL 
did  not  hold  the  kind  of  appointment  at  Caltech  that  permitted  them  to  train  graduate 
students  as  future  radar  astronomers,  and  no  Caltech  professor  was  interested  in  training 
radar  astronomers.  A  similar  situation  had  existed  at  Lincoln  Laboratory  during  the  1960s 
until  Pettengill's  appointments  at  Arecibo  and  his  subsequent  teaching  position  at  MIT 
changed  that  situation  and  provided  the  institutional  matrix  for  the  training  of  graduate 


205 


206  TO  SEE  THE  UNSEEN 


students  as  future  radar  astronomers.  In  short,  the  teacher-disciple  pattern  that  prevailed 
at  Arecibo  was  lacking  at  JPL,  where  radar  astronomers  propagated  through  job  hiring. 
Planetary  radar  astronomy  at  JPL  remained  unofficial  and  invisible.  Between  1978  and 
1986,  furthermore,  essentially  no  radar  astronomy  work  took  place  at  Goldstone,  because 
investigators  lacked  a  reliable  research  instrument. 

The  Galilean  Moons  of  Jupiter 

Among  the  new  radar  targets  brought  into  range  by  the  Goldstone  X-band  and 
Arecibo  S-band  upgrades  were  Ganymede,  Eurcpa,  Callisto,  and  lo,  named  the  Galilean 
moons  of  Jupiter  after  their  discoverer,  Galileo  Galilei.  The  radar  exploration  of  those 
moons  illustrated  the  interactions  between  radar  astronomers  and  geologists,  as  well  as 
the  increasing  collaboration  with  Stanford  researchers  that  came  to  typify  ground-based 
planetary  radar.  Those  moons  also  puzzled  radar  astronomers.  Never  before  had  they 
encountered  such  peculiar  radar  characteristics  among  the  terrestrial  planets.  An  expla- 
nation for  the  bizarre  radar  readings  came  from  Earth  and  from  leading  edge  research  in 
the  physics  of  light. 

The  first,  though  unsuccessful,  attempt  at  the  Galilean  moons  took  place  in  1970. 
Dick  Goldstein  (at  Goldstone)  and  Dick  Ingalls  and  Irwin  Shapiro  (at  Haystack)  tried  to 
detect  echoes  from  Callisto  using  the  bistatic  Goldstack  radar,  in  which  the  Haystack 
300-kilowatt  telescope  transmitted  and  Goldstone  received.1  The  experiment  did  not 
work,  however,  because  of  a  misunderstanding  over  polarization. 

After  unsuccessfully  attempting  Venus  with  the  Goldstack  radar,  Ingalls  and 
Goldstein  pointed  the  radar  at  the  Moon  and  received  "the  weakest  of  signals."  Goldstein, 
trained  as  an  electrical  engineer,  realized  what  was  wrong.  Bistatic  radars  require  investi- 
gators to  agree  on  the  polarization  of  the  wave.  Physicists,  like  Shapiro,  use  one  definition 
for  left-handed  polarization,  defining  handedness  from  the  view  of  a  person  looking  in 
the  direction  that  the  wave  is  travelling,  while  electrical  engineers  use  the  opposite  con- 
vention, defining  handedness  from  the  view  of  the  receiving  antenna,  so  left  and  right  are 
reversed.  Goldstack  eventually  searched  for  Ganymede  and  Callisto  in  late  May  and  early 
June  1970.2  The  polarization  of  radar  echoes  was  about  to  become  a  key  radar  technique 
for  studying  the  Galilean  moons  and  other  solar  system  bodies. 

Dick  Goldstein  and  George  A.  Morris  succeeded  in  detecting  Ganymede  with  the  400 
kilowatts  of  Goldstone  S-band  radar  power  on  six  nights  in  late  August  1974.  Those  echoes 
set  a  record  for  the  longest  time  of  flight  to  a  radar  target,  one  hour  and  seven  minutes. 
The  echoes,  though,  were  very  weak,  well  below  the  noise  level.  From  those  weak  echoes, 
Goldstein  and  Morris  drew  conclusions  about  the  surface  of  Ganymede. 

From  the  total  signal  power  returned  and  the  width  of  the  spectrum,  they  conclud- 
ed that  Ganymede  "must  have  a  considerable  degree  of  roughness."  Their  data  did  not 
agree  with  accepted  theory,  derived  from  infrared  spectra  and  polarization  studies,  that 
Ganymede's  surface  consisted  mostly  of  ice.3  Goldstein  and  Morris  ventured  that  the  most 


1.  Referred  to  in  Campbell,  Chandler,  Pettengill,  and  Shapiro,  "Galilean  Satellites  of  Jupiter:  12.6- 
Centimeter  Radar  Observations,"  Science  196  (1977):  650. 

2.  Shapiro  1  October  1993;  "Funding  Proposal,  'Plan  for  NEROC  Operation  of  the  Haystack  Research 
Facility  as  a  National  Radio/Radar  Observatory,'  NSF,  7/1/71-6/30/73,"  26/2/AC  135,  and  Sebring  to 
Hurlburt,  27  March  1970,  18/2/AC  135,  MITA;  NEROC,  Proposal  to  the  National  Science  Foundation  for 
Programs  in  Radio  and  Radar  Astronomy  at  the  Haystack  Observatory,  8  May  1970,  pp.  III.8-  III. 10,  LLLA;  JPL 
1970  Annual  Report,  p.  14,  JPLA. 

3.  See  Joseph  Veverka,  "Polarization  Measurements  of  the  Galilean  Satellites  of  Jupiter,"  Icarus  14 
(1971):  355-359;  John  S.  Lewis,  "Low  Temperature  Condensation  from  the  Solar  Nebula,"  Icarus  16  (1972): 
241-252.  Although  lo,  Ganymede,  and  Europa  were  believed  covered  with  frost,  Callisto  was  believed  to  be  dif- 
ferent, more  like  the  Moon,  though  with  some  frost  possibly  present. 


THE  OUTER  LIMITS  207 


likely  possibility  was  for  the  surface  to  consist  of  rocky  or  metallic  material  from  meteoric 
bombardment  embedded  in  a  matrix  of  ice.4 

Soon  after  the  Arecibo  S-band  upgrade  reached  completion,  Don  Campbell  (NAIC 
Research  Associate)  and  Gordon  Pettengill  (MIT)  made  the  first  radar  detections  of 
Callisto  and  Europa  on  28  September  and  5  October  1975,  respectively,  and  detected 
Ganymede  on  30  September.  Pettengill  and  Campbell  noticed  that  the  satellites  had  an 
unusual  radar  signature.  The  three  moons  were  almost  uniformly  radar  bright;  they 
lacked  the  bright  specular  return  from  the  subradar  point,  the  area  on  the  target  closest 
to  the  Earth,  that  all  terrestrial  planets  exhibit.  The  uniformity  of  brightness  suggested 
tiiat  the  satellite  surfaces  were  probably  extremely  rough  on  scales  comparable  to  or  larg- 
er than  the  wavelength  of  12  cm. 

lo  remained  an  elusive  radar  target.  The  innermost  of  the  Galilean  moons,  lo  is 
inside  Jupiter's  magnetosphere,  which  may  have  interfered  with  the  radar  waves  aimed  at 
lo.  Campbell  and  Pettengill  unsuccessfully  attempted  the  satellite  twice  in  1975,  and  their 
attempt  to  detect  lo  in  January  1976  yielded  only  a  weak  echo  that  indicated  an  error  in 
the  ephemeris  large  enough  to  explain  the  previous  failed  attempt.  Not  until  1987,  when 
improved  hardware  was  available,  did  radar  astronomers  begin  to  receive  good  echoes 
from  lo. 

After  reducing  their  January  1976  data  on  the  four  Galilean  moons,  Campbell  and 
Pettengill  found  surprisingly  large  radar  cross  sections  for  Europa  and  Ganymede, 
approximately  1 .5  and  0.9  times  the  geometric  cross  section,  respectively,  while  those  for 
Callisto  and  lo  were  around  0.4  and  0.2,  respectively.  The  radar  cross  section  is  a  measure 
of  target  brightness.  Although  the  values  for  Callisto  and  lo  were  low  and  typical  of  the 
terrestrial  planets,  the  radar  cross  sections  for  Europa  and  Ganymede  were  abnormally 
high.5 

When  Pettengill  and  Campbell  resumed  their  observations  of  Jupiter's  moons  in 
October  1976,  the  Arecibo  radar  had  a  dual  polarized  circular  feed  paid  for  with  NASA 
S-band  operations  funds.  The  feed  increased  total  system  sensitivity  over  that  available  in 
1975  and  displayed  the  peculiar  radar  polarization  properties  of  the  Galilean  satellites. 

Previously,  all  observations  of  the  Galilean  moons  had  been  made  with  linear  feeds 
in  both  orthogonal  linear  polarizations.  The  transmitter  sent  out  signals  with  one  sense  of 
polarization,  and  the  antenna  received  both  the  same  linear  and  orthogonal  linear  polar- 
izations. The  same  linear  echoes  are  much  stronger  than  the  orthogonal  linear  echoes  for 
all  targets  detected  by  radar.  Although  the  switch  from  linear  to  circular  polarization  did 
not  alter  the  general  character  of  the  spectra  for  Callisto,  Ganymede,  and  Europa,  the  cir- 
cular polarization  ratios  of  the  echoes  were  totally  unanticipated. 

When  radar  astronomers  transmit  a  right-handed  circularly  polarized  signal,  they 
expect  the  echo  to  return  mostly  left-handed  circularly  polarized,  the  opposite  handed- 
ness.  This  type  of  polarization  return  is  called  variously  the  "expected,"  "polarized,"  or 
"opposite  circular"  (OC).  The  echo  power  returned  right-handed  circularly  polarized  is 
said  to  have  "unexpected,"  "depolarized,"  or  "same  circular"  (SC)  polarization.  The  SC-to- 
OC  ratio  is  known  as  the  circular  polarization  ratio. 

The  terminology  "expected"  and  "unexpected"  is  out  of  place  today.  The  "unex- 
pected" polarization  returns  from  the  Galilean  moons  and  other  icy  targets  are  no  longer 
considered  unusual  or  "unexpected."  The  terms,  however,  reflected  the  surprise  of  radar 
astronomers  in  the  past,  as  they  discovered  polarization  returns  that  differed  markedly 
from  those  of  the  terrestrial  planets.  For  the  sake  of  preserving  that  historical  flavor  of  dis- 
covery, and  to  avoid  using  terms  likely  unfamiliar  and  perhaps  confusing  to  the  reader 
(such  as  "polarized"  and  "depolarized"),  the  terminology  "expected"  and  "unexpected," 
or  OC  and  SC,  will  be  used  throughout. 


4.  Goldstein  and  Morris,  "Ganymede:  Observations  by  Radar,"  Science  188  (1975):  1211-1212. 

5.  Campbell  8  December  1993;  NAIC  QR  Q3/1975,  4-5;  NAIC  QR  Q4/1975,  5;  NAIC  QR  Ql/1976,  6. 


208  TO  SEE  THE  UNSEEN 


In  radar  observations  of  the  terrestrial  planets  and  the  Moon,  more  power  normally 
returns  in  the  expected  than  in  the  unexpected  mode.  The  circular  polarization  ratio  for 
these  targets  is  about  0.1;  for  Venus  and  the  Moon,  it  is  only  about  0.05.  In  the  case  of 
Jupiter's  moons,  however,  more  power  returned  in  the  unexpected  mode,  a  phenomenon 
called  circular  polarization  inversion.  For  Europa,  Ganymede,  and  Callisto,  the  average 
circular  polarization  ratios  were  1.61  ±  0.20, 1.48  ±  0.27,  and  1.24  ±0.19,  respectively.  They 
were  the  first  solar  system  objects  for  which  circular  polarization  inversion  was  observed.6 

The  dominance  of  unexpected  polarization  from  the  Galilean  satellites  was  enig- 
matic and  even  unbelievable.  "That  was  a  bit  of  a  puzzle,"  Don  Campbell  recalled.  'There 
was  a  lot  of  skepticism,  frankly,  about  the  results.... That  was  a  really  significant  puzzle  to 
everybody."7  The  phenomenon  was  also  a  puzzle  to  Steve  Ostro,  then  a  graduate  student 
at  MIT  working  under  Gordon  Pettengill.  Ostro  was  looking  for  a  dissertation  topic.  He 
joined  Pettengill  and  Campbell  in  observing  the  Galilean  satellites  at  Arecibo  in  late  1976. 
'The  anticipation,"  Ostro  explained,  "was  that  working  on  those  observations,  as  well  as 
on  the  data  reduction  and  interpretation,  would  evolve  into  a  good  thesis  topic."8 

When  the  bizarre  circular  polarization  inversion  first  appeared  during  the  26 
October  through  7  December  1976  observations,  Ostro  recalled,  "We  tested  to  the  point 
of  grasping  at  straws.  Maybe  we  had  crossed  the  cables.  Or  maybe  somebody  had  screwed 
up  in  the  data  acquisition  program.  We  checked  everything.  We  couldn't  believe  it,  just 
couldn't  believe  it."  A  test  on  Venus  returned  normal  echoes.  Then  they  pointed  the  tele- 
scope at  Europa,  and  the  circular  polarization  ratio  was  about  one  and  a  half.  At  that 
point,  Ostro  remembers  watching  Pettengill  reflecting  then  saying,  "Well,  now  I  have  to 
believe  it."  Then  he  turned  to  Ostro  and  said,  "If  you  can  explain  this,  it  would  be  a  good 
thesis  topic."9 

In  order  to  investigate  systematically  the  unusual  radar  cross  sections  and  polariza- 
tion ratios  of  the  Galilean  moons,  Ostro,  Campbell,  and  Pettengill  undertook  a  new  series 
of  20  observation  sessions  in  November  and  early  December  1977  and  obtained  results 
similar  to  those  found  the  previous  year.10 

Ostro,  Pettengill,  and  Campbell  continued  their  campaign  on  the  Galilean  satellites 
in  February  1979  and  March-April  1980,  when  the  satellites  were  in  different  phases.  Also, 
in  order  to  determine  whether  the  strange  polarization  ratios  were  a  function  of  fre- 
quency, Don  Campbell  undertook  a  separate  series  of  observations  with  the  old  430-MHz 
(70-cm)  radar  and  obtained  a  weak  detection  of  Europa,  but  not  of  Ganymede.11  Jupiter 
then  left  the  declination  window  of  the  Arecibo  Observatory  until  1987. 

In  order  to  account  for  the  unusual  radar  signatures  of  Europa,  Ganymede,  and 
Callisto,  Steve  Ostro  developed  a  model,  published  in  1978.  The  model  postulated  a  thick 
surface  layer  of  ice  saturated  with  nearly  hemispherical  surface  craters.  Hemispherical 
craters  would  favor  double  reflection  of  radar  waves  at  a  45°  angle  at  each  reflection,  so 
that  most  of  the  signal  would  return  with  the  same  handedness  of  polarization.  The  same 
craters  could  be  made  to  explain  the  high  radar  cross  sections,  as  well.12 


6.  Campbell,  Chandler,  Pettengill,  and  Shapiro,  "Galilean  Satellites  of  Jupiter:  12.6-Centimeter  Radar 
Observations,"  Science  196  (1977):  650-653;  Campbell,  Chandler,  Steven  J.  Ostro,  Pettengill,  and  Shapiro, 
"Galilean  Satellites:  1976  Radar  Results,"  Icarus  34  (1978):  254-267;  NAIC  QR  Ql/1976,  17;  Ostro,  "Radar 
Properties  of  Europa,  Ganymede,  and  Callisto,"  in  David  Morrison,  ed.,  Satellites  of  Jupiter  (Tucson:  University  of 
Arizona  Press,  1982),  p.  213. 

7.  Campbell  8  December  1993. 

8.  Ostro  18  May  1994;  NAIC  QR  Ql/1976,  6. 

9.  Ostro  18  May  1994. 

10.  Campbell,  Chandler,  Ostro,  Pettengill,  and  Shapiro,  "Galilean  Satellites:  1976  Radar  Results,"  Icarus 
34  (1978):  254-267;  Ostro,  "The  Structure  of  Saturn's  Rings  and  the  Surfaces  of  the  Galilean  Satellites  as  Inferred 
from  Radar  Observations,"  Ph.D.  dissertation,  MIT,  1978;  NAIC  QRQ4/1977,  5-6;  NAIC  QR  Ql/1978,  6. 

1 1 .  Ostro,  Campbell,  Pettengill,  and  Shapiro,  "Radar  Observations  of  Europa,  Ganymede,  and  Callisto," 
Icarus44  (1980):  431-440;  NAIC  QRQ1/1979,  10;  NAIC  QRQ2/1980,  11. 

12.  Ostro  and  Pettengill,  "Icy  Craters  on  the  Galilean  Satellites?"  Icarus  34  ( 1978):  268-279. 


THE  OUTER  LIMITS  209 


Dick  Goldstein  and  Richard  R.  Green  at  JPL  proposed  a  different  model  based  on 
their  own  observations  of  the  Galilean  satellites.  After  the  pioneering  observations  of  1974 
at  S-band,  Goldstein  took  additional  data  on  Ganymede  during  six  nights  in  December 
1977  with  the  Goldstone  X-band  radar  and  received  alternately  right-handed  and  left- 
handed  circular  polarization,  in  order  to  compare  the  expected  and  unexpected  echo 
strengths.  Despite  the  high  transmitter  power  (343  kilowatts)  and  low  system  noise 
temperature  (23  K),  the  Ganymede  echoes  were  noisy.  Nonetheless,  the  Goldstone  data 
confirmed  the  Arecibo  results,  which  had  been  the  subject  of  great  incredulity.  As  Don 
Campbell  recalled,  'That  confirmation  started  a  significant  discussion  about  the 
phenomenon.  Why  were  we  getting  these  odd  reflections?"13 

From  the  spectral  data,  Goldstein  and  Green  measured  the  radar  cross  section  and 
polarization  ratios  and  posited  a  model  of  Ganymede's  surface.  They  assumed  that  the 
upper  few  meters  of  its  surface  consisted  of  ice  "crazed  and  fissured  and  covered  by  jagged 
ice  boulders."  The  critical  part  of  the  model  was  a  large  number  of  interfaces  between  ice 
and  vacuum  where,  depending  on  the  angle  of  incidence  above  or  below  a  certain  limit 
(called  the  critical  angle),  the  sense  of  polarization  was  largely  preserved  and  most  of  the 
power  remained  in  the  original  polarization  sense.  In  a  1982  review  article,  Steve  Ostro 
concluded  that  "many  questions  remain  about  interpretation  of  the  radar  results,  but  we 
seem  to  be  pointed  in  a  sensible  direction."14 

Voyager  1  had  begun  sending  back  pictures  of  the  Jupiter  system  in  early  1979. 
Geologic  activity  on  Ganymede  appeared  varied,  while  Callisto's  entire  surface  was 
densely  cratered.  Europa  probably  was  covered  completely  by  ice.15  More  information 
than  ever  was  available  about  the  surfaces  of  the  Galilean  satellites,  yet  none  of  it  resolved 
the  questions  raised  by  planetary  radar  astronomers,  who,  in  the  meantime,  attempted  to 
explain  the  strange  radar  characteristics  of  the  Galilean  satellites  based  on  reflection 
geometries  and  radar  scattering  rules,  not  the  geology  of  those  worlds  as  revealed  by 
Voyager  imagery. 

Among  those  offering  explanations  for  the  high  cross  section  and  circular  polariza- 
tion inversion  was  Tor  Hagfors.  He  proposed  that  the  satellites'  unusual  radar  signatures 
were  due  not  to  reflections  at  the  interfaces  of  ice  and  vacuum,  as  Goldstein  and  Green 
had  suggested,  but  rather  to  the  bending  of  the  incident  wave  around  continuous  gradi- 
ents in  refractive  index.16  Von  Eshleman  developed  an  argument  around  refraction 
scattering  from  imperfect  spheroidal  lenses.  Then  he  modified  his  argument  and 
incorporated  Ostro's  notion  of  hemispheroidal  impact  craters,  as  well  as  elements  from 
the  Goldstein-Green  model.17 

The  Ostro,  Goldstein-Green,  Hagfors,  and  Eshleman  models  all  rested  on  radar 
geometries  and  scattering  mechanisms.  Not  a  single  model  linked  surface  or  subsurface 
structure  realistically  to  the  radar  signatures,  nor  did  the  models  explain  the  origins  of 
those  structures.  Positing  the  existence  of  hemispherical  craters  was  one  thing;  finding 
geologic  evidence  for  them  was  another.  Not  surprisingly,  Voyager  revealed  no  hemi- 
spherical craters  on  any  of  the  Galilean  satellites.  Ostro  now  sought  an  explanation  for  the 
radar  signatures  of  the  Galilean  moons  in  collaboration  with  USGS  planetary  geologist 
Eugene  Shoemaker. 


13.  Campbell  8  December  1993. 

14.  Goldstein  and  R.  Green,  "Ganymede:  Radar  Surface  Characteristics, "  Science  207  (1980):  179-180; 
Ostro,  "Radar  Properties  of  Europa,  Ganymede,  and  Callisto,"  in  Morrison,  Satellites  of  Jupiter,  pp.  225-233,  and 
quote  p.  235. 

15.  Morrison  and  Jane  Samz,  Voyage  to  Jupiter,  NASA  SP-439  (Washington:  NASA,  1980),  pp.  58,  60 
and  142. 

16.  Hagfors,  Gold,  and  M.  lerkic,  "Refraction  Scattering  as  Origins  of  the  Anomalous  Radar  Returns  of 
Jupiter's  Satellites,"  Nature  315  (1985):  637-  640. 

17.  Eshleman,  "Mode  Decoupling  during  Retrorefraction  as  an  Explanation  for  Bizarre  Radar  Echoes 
from  Icy  Moons,"  Nature  319  (1986):  755-757;  Eshleman,  "Radar  Glory  from  Buried  Craters  on  Icy  Moons," 
Science  234  (1986):  587-590. 


210  TO  SEE  THE  UNSEEN 


Shoemaker  had  a  rather  simple  and  elegant  geologic  solution  to  the  problem.  In 
developing  his  solution,  Shoemaker  drew  upon  his  knowledge  of  the  lunar  regolith  and 
Voyager  data.  He  assumed  that  the  surfaces  of  the  Galilean  moons  were  exactly  like  that 
of  the  Moon.  From  statistics  of  craters  observed  in  Voyager  images  of  Ganymede  and 
Callisto,  Shoemaker  inferred  that  the  surfaces  of  those  moons  had  a  history  of  meteor 
bombardment  similar  to  that  of  the  Moon.  He  concluded  that  they  were  probably 
blanketed  with  fragmental  debris  produced  by  prolonged  meteoroid  bombardment.  The 
only  difference,  then,  between  the  Moon  and  Jupiter's  moons  was  that  the  rocks  on  the 
Galilean  satellites  were  made  of  ice,  and  the  ice,  given  the  extremely  low  ambient 
temperatures,  would  behave  like  a  silicate  rock.  Ice  is  highly  transparent  to  radar  waves, 
so  the  icy  surfaces  of  the  Galilean  moons  would  permit  radar  waves  to  penetrate  those  sur- 
faces to  a  far  greater  extent  than  if  they  were  made  of  silicate  rock.  The  combination  of 
the  greater  penetrating  depth  and  the  greater  number  of  scattering  events  could  provide 
an  explanation  for  the  peculiar  radar  signatures  of  the  Galilean  satellites.18 

The  primary  contribution  of  the  Ostro-Shoemaker  model  was  its  geological  per- 
spective. Nonetheless,  the  model  only  partially  explained  the  radar  results;  a  satisfactory 
understanding  of  the  detailed  scattering  mechanism  that  gave  rise  to  the  odd  radar  sig- 
natures still  remained  beyond  reach.  Meanwhile,  Steve  Ostro  and  Don  Campbell  had 
begun  a  new  series  of  radar  observations  of  the  Galilean  satellites  at  Arecibo  in  1987. 
Unlike  the  previous  campaign,  Stanford  researchers  under  the  leadership  of  Von 
Eshleman  participated.  Dick  Simpson  took  data  at  Arecibo,  while  a  graduate  student,  Eric 
Gurrola,  was  charged  with  the  analysis.  Tor  Hagfors,  who  also  was  interested  in  experi- 
menting on  the  Galilean  satellites  for  reasons  similar  to  those  of  the  Stanford  researchers, 
joined  their  group. 

This  new  series  of  S-band  observations  was  to  provide  thorough  phase  coverage  for 
all  three  icy  satellites  (Ganymede,  Callisto,  and  Europa).  Started  in  November  1987,  the 
campaign  continued  into  1988,  then  November-December  1989,  January  1990,  and 
February-March  1991,  when  Ostro  observed  the  satellites  at  rotational  and  orbital  phases 
chosen  to  fill  in  gaps  in  the  1987-1990  phase  coverage.19  Then  Jupiter  left  the  Arecibo 
declination  window. 

At  the  same  time,  Arecibo  obtained  the  first  good  echoes  from  lo.  Its  radar  proper- 
ties were  unlike  those  of  the  other  Galilean  satellites.  Data  collected  in  1976  already  had 
shown  that  lo's  surface  was  significantly  rougher  on  average  than  the  terrestrial  planets, 
but  much  smoother  than  the  other  Galilean  moons.  Its  radar  cross  section  and  polariza- 
tion ratio  were  more  typical  of  the  inner  planets,  however,  and  argued  strongly  against  the 
presence  of  significant  quantities  of  surface  ice.20 

In  parallel  with  the  2,380-MHz  (12.6-cm)  observations,  Don  Campbell  studied  the 
Galilean  moons  with  the  430-MHz  (70-cm)  radar  beginning  in  November  1988,  the  first 
time  in  25  years  that  the  UHF  radar  had  been  used  in  the  continuous-wave  mode.  He 
detected  Ganymede  and  Callisto,  then  in  November-December  1989,  made  the  first  UHF 
detection  of  Europa.  The  purpose  of  the  experiment  was  to  compare  the  polarization 
properties  of  the  Galilean  satellites  at  both  S-band  and  UHF.  Campbell  discovered  that  the 
echoes  from  Ganymede  at  UHF  were  reminiscent  of  those  at  S-band.  Additional  UHF 
measurements  made  in  January  1990  apparently  confirmed  that  the  peculiar  polarization 
ratios  of  the  Galilean  moons  were  independent  of  frequency.21 


18.  Shoemaker  30  June  1994;  Ostro  and  Eugene  M.  Shoemaker,  The  Extraordinary  Radar  Echoes  from 
Europa,  Ganymede,  and  Callisto:  A  Geological  Perspective,"  Icarus  85  (1990):  335-345. 

19.  E-mail,  Simpson  to  author,  9  November  1994;  NAIC  QR  Q2/1987,  7;  Q3/1987,  8-9;  Q4/1987,  9; 
Q2/1988,  9;  Q4/1988,  8;  Q4/1989,  7;  Ql/1990,  7;  Ql/1991,  7;  Ql/1992,  8. 

20.  Campbell,  Chandler,  Ostro,  Pettengill,  and  Shapiro,  "Galilean  Satellites:  1976  Radar  Results,"  Icarus 
34  (1978):  254-267;  NAIC  QR  Ql/1976,  6;  Q4/1977,  5-6;  Q2/1987,  7;  Q3/1987,  8-9;  Q4/1987,  9. 

21.  NAIC  QR  Q4/1989,  7;  Ql/1990,  7. 


THE  OUTER  LIMITS  2 1 1 


Steve  Ostro,  who  now  had  a  position  at  JPL,  also  observed  the  Galilean  satellites  with 
the  Goldstone  X-band  radar  between  1987  and  1991  and  measured  polarization  ratios  and 
radar  cross  sections.  The  combined  X-band,  S-band,  and  UHF  radar  data  taken  over  a 
long  period  of  time  documented  the  degree  to  which  the  satellites'  radar  properties 
depended  on  target,  rotational  phase,  and  frequency.22  They  provided  a  considerable  base 
upon  which  to  explain  the  bizarre  radar  signatures  of  the  Galilean  moons,  and  a  reason- 
able explanation  soon  was  in  hand. 

Toward  the  end  of  the  Arecibo  and  Goldstone  campaign  on  the  Galilean  satellites, 
Bruce  Hapke,  an  optical  astronomer  and  scattering  expert,  drew  attention  to  a  growing 
body  of  literature  on  laboratory  and  theoretical  investigations  of  a  phenomenon  called 
alternatively  "coherent-backscatter  effect"  or  "weak  localization."  The  effect  has  potential 
application  in  a  new  class  of  semiconductors  in  which  photons,  rather  than  electrons,  per- 
form circuitry  functions.  Weak  localization  of  light  takes  place  at  the  microscopic  level 
and  arises  from  a  combination  of  coherent  multiple  scattering  and  interference. 
Backscattered  intensity  is  enhanced,  and  the  forward  diffusion  through  the  low-loss  medi- 
um reduced,  by  constructive  interference  between  fields  propagating  along  identical  but 
time-reversed  paths.23 

At  the  suggestion  of  Steve  Ostro,  Kenneth  J.  Peters  of  Caltech  did  calculations  that 
demonstrated  that  coherent  backscattering  from  forward  scatterers  could  explain  the 
high  reflectivity  and  polarization  ratios  of  the  Galilean  satellites.24  Coherent  backscatter- 
ing now  appeared  to  explain  adequately  the  high  radar  cross  sections  and  circular  polar- 
ization ratios  of  the  icy  satellites,  and  it  was  consistent  with  the  geologic  picture  of  those 
moons  painted  by  Gene  Shoemaker.  The  scattering  might  arise  less  from  individual  pieces 
of  ejecta,  but  more  likely  from  uncoordinated  changes  in  porosity  (and  hence  refractive 
index)  that  occur  randomly  throughout  "smoothly  heterogeneous"  regoliths,  argued 
Ostro  and  Shoemaker.25 

Additional  data  on  the  radar  properties  of  icy  surfaces  came  from  observations  of  the 
Earth.  In  June  1991,  the  NASA/JPL  airborne  synthetic  aperture  radar  (AIR-SAR)  flew 
over  a  vast  portion  of  the  Greenland  ice  sheet  called  the  percolation  zone,  where  summer 
melting  generates  water  that  percolates  down  through  the  cold,  porous  dry  snow  then 
refreezes  in  place  to  form  massive  layers  and  pipes  of  solid  ice.  The  AIR-SAR  radar 
observed  the  Greenland  ice  sheet  at  several  wavelengths  (5.6-,  24-,  and  68-cm)  and 
obtained  values  for  the  circular  polarization  ratio  greater  than  one.26 

The  riddle  of  the  strange  radar  signatures  of  the  Galilean  satellites  focused  radar 
astronomers'  attention  on  epistemological  questions,  the  fundamental  need  to  under- 
stand and  interpret  radar  echoes  and  their  relationship  to  the  target.  Such  questions, 
though,  were  of  interest  only  to  radar  astronomers;  their  solutions  contributed  to  an 


22.  Ostro,  Campbell,  Simpson,  R.  Scott  Hudson,  Chandler,  Keith  D.  Rosema,  Shapiro,  Standish,  R. 
Winkler,  Donald  K.  Yeoman,  Ray  Velez,  and  Goldstein,  "Europa,  Ganymede,  and  Callisto:  New  Radar  Results 
from  Arecibo  and  Goldstone ,"  Journal  of  Geophysical  Research  97  (1992):  18,227-18,244.  The  Goldstone  observa- 
tions were  made  10-11,  13,  15-16,  22,  26,  and  29-30  November  1988;  5  and  8  December  1988;  13,  14,  15,  18, 
19,  20,  22,  24,  27,  and  29  December  1989;  13,  18,  22  and  27  December  1990. 

23.  Ostro  18  May  1994;  Bruce  Hapke,  "Coherent  Backscatter  and  the  Radar  Characteristics  of  Outer 
Planet  Satellites,"  Icarus  88  (1990):  407-417;  Hapke  and  David  Blewett,  "Coherent  Backscatter  Model  for  the 
Unusual  Radar  Reflectivity  of  Icy  Satellites,"  Mz/«r«352  (1991)  46-47;  Sajeevjohn,  "Localization  of  Light,"  Physics 
Today  44  (May  1991):  32-40. 

24.  Kenneth  J.  Peters,  "Coherent-Backscatter  Effect:  A  Vector  Formulation  Accounting  for  Polarization 
and  Absorption  Effects  and  Small  or  Large  Scatterers,"  Physical  Review  B  46  (1992):  801-812;  John,  "Localization 
of  Light,"  Physics  Today  44  (May  1991):  32-40;  Ostro  18  May  1994. 

25.  Ostro   18  May  1994;  Ostro  and  Shoemaker,  The  Extraordinary  Radar  Echoes  from  Europa, 
Ganymede,  and  Callisto:  A  Geological  Perspective,"  7ean«85  (1990):  335-345. 

26.  Eric  J.  Rignot,  Ostro,  Jakob  J.  Van  Zyl,  and  K,  C.  Jezek,  "Unusual  Radar  Echoes  from  the  Greenland 
Ice  Sheet,"  Sci«n«261  (24  September  1993):  1710-1711. 


212  TO  SEE  THE  UNSEEN 


understanding  of  the  radar  characteristics  of  planetary  surfaces,  but  not  to  the  more  gen- 
eral scientific  questions  posed  by  non-radar  planetary  astronomers.  However,  if  radar 
astronomers  were  going  to  contribute  to  our  knowledge  of  the  Jupiter  and  Saturn  systems, 
they  first  had  to  resolve  such  basic  epistemological  issues  relating  to  the  radar  properties 
of  those  planetary  systems. 

Although  the  central  focus  of  radar  research  on  the  Galilean  satellites  had  been  the 
solution  of  the  satellites'  strange  radar  signatures,  the  data  also  has  served  to  correct  their 
ephemerides  as  part  of  the  Planetary  Ephemeris  Program  of  Irwin  Shapiro  and  John 
Chandler  of  the  Harvard-Smithsonian  Center  for  Astrophysics.  The  radar  data  uncovered 
errors  in  the  ephemerides  as  early  as  1976.  A  round  of  Callisto  observations  carried  out 
beginning  in  1987,  though,  were  intended  mainly  for  orbital  ephemeris  refinement  in 
support  of  the  Galileo  mission.27 

Sensitized  to  the  needs  of  planetary  geologists,  Ostro  also  attempted  to  relate  radar 
data  collected  at  Arecibo  and  Goldstone  between  1987  and  1991  to  surface  features  on  the 
Galilean  moons.  The  most  prominent  features  tentatively  identified  in  the  echo  spectra 
were  Ganymede's  Galileo  Regio  and  Callisto's  Valhalla  Basin.28  Using  a  new  radar  coding 
technique,  John  Harmon  and  Steve  Ostro  observed  Ganymede  and  Callisto  at  Arecibo 
from  February  to  March  1992  and  obtained  the  first  range-Doppler  images  of  the  moons. 
These  observations  also  constituted  the  first  successful  ranging  measurements  to  the 
Galilean  satellites  and  the  farthest  radar  distance  measurements  ever  reported.29 

The  exploration  of  the  Galilean  moons  of  Jupiter  illustrated  the  increasing  com- 
plexity of  the  planetary  radar  paradigm.  Hardware  improvements,  coding  techniques,  and 
even  discoveries  made  in  optics  laboratories  shaped  the  science  done  by  radar 
astronomers.  Moreover,  despite  the  shift  toward  geology,  planetary  radar  remained  ori- 
ented toward  astronomical  questions  and  NASA  missions,  such  as  Galileo. 

The  Outer  Limits 

The  rings  of  Saturn,  like  the  Galilean  moons  of  Jupiter,  presented  radar  astronomers 
with  a  target  very  different  from  the  terrestrial  planets.  The  rings  of  Saturn  were  believed 
to  be  icy  and  until  the  1970s,  were  thought  to  consist  of  tiny,  micron-sized  particles.  Radar 
astronomy  upset  that  conception  of  the  rings.  In  doing  so,  radar  astronomy  also  set  a  dis- 
tance record:  the  round-trip  light  time  to  the  rings  was  about  2  hours  and  15  minutes. 

After  an  unsuccessful  try  in  1967,  Haystack  researchers  successfully  bounced  X-band 
radar  waves  off  the  rings  in  1973. 30  Earlier,  however,  in  December  1972  and  January  1973, 
Richard  Goldstein  and  George  A.  Morris,  Jr.,  at  JPL  detected  the  rings  with  the  S-band 
Goldstone  Mars  Station.  Making  the  observation  was  not  easy.  The  orientation  of  the  rings 
is  optimum  for  radar  observations  only  twice  during  each  29-year  orbit  of  Saturn,  when 
the  rings  are  most  tilted  to  the  line  of  sight  and  present  the  largest  projected  area.  At  the 
same  time,  the  Doppler  spreading  and  consequent  dilution  of  the  signals  in  the  noise  is 
the  least. 


27.  NAIC  QR  Ql/1976,  7;  Q4/1977,  5-6;  Q3/1987,  8-9;  Q2/1988,  9;  Ql/1992,  8;  Campbell,  Chandler, 
Pettengill,  and  Shapiro,  "Galilean  Satellites  of  Jupiter:  12.6-Centimeter  Radar  Observations,"  Science  196  (1977): 
651;  Ostro,  Campbell,  Simpson,  Hudson,  Chandler,  Rosema,  Shapiro,  Standish,  Winkler,  Yeoman,  Velez,  and 
Goldstein,  "Europa,  Ganymede,  and  Callisto:  New  Radar  Results  from  Arecibo  and  Goldstone,"  Journal  of 
Geophysical  Research  97  (1992):  18,227-18,244. 

28.  Ostro,  Campbell,  Simpson,  Hudson,  Chandler,  Rosema,  Shapiro,  Standish,  Winkler,  Yeoman,  Velez, 
and  Goldstein,  "Europa,  Ganymede,  and  Callisto:  New  Radar  Results  from  Arecibo  and  Goldstone, "Journal  of 
Gerfhysical Research 97  (1992):  18,227-18,244;  NAIC  QRQ1/1991,  7. 

29.  Ostro,  Pettengill,  Campbell,  Goldstein,  Icarus  49  ( 1982) :  367. 

30.  NEROC,  Final  Progress  Report  Radar  Studies  of  the.  Planets,  29  August  1974,  pp.  1,3,6  and  8-9;  Log  Book, 
Haystack  Planetary  Radar,  HR-73-1,  27  June  1973  to  26  November  1973,  SEBRING;  and  Goldstein,  R.  Green, 
Pettengill,  and  Campbell,  "The  Rings  of  Saturn:  Two-Frequency  Radar  Observations,"  Icarus  30  (1977):  105. 


THE  OUTER  LIMITS  2 1 3 


The  echoes  Goldstein  and  Morris  found  were  unexpectedly  strong.  The  rings  were 
inclined  at  an  angle  about  26°  with  respect  to  the  line  of  sight,  and  the  amount  of  power 
returned  from  the  rings  was  about  10  times  that  for  Mercury  and  five  times  that  for  Venus. 
Moreover,  wrote  Goldstein  and  Morris:  "Particles  of  any  material  that  are  much  smaller 
than  our  wavelength  [12.6  cm]  are  ruled  out  by  our  data.. ..Large  (compared  to  the  wave- 
length), irregular,  rough  particles  could  produce  the  observed  echoes."31 

Shortly  thereafter,  on  31  July  and  1  August  1973,  JPL  organized  a  workshop  on 
Saturn's  rings  at  the  request  of  S.  Ichtiaque  Rasool  of  the  Planetary  Programs  Office, 
NASA  Headquarters.  Gordon  Pettengill  organized  the  scientific  program.  The  workshop 
responded  to  an  upsurge  in  interest  in  the  Saturn  system,  and  the  outer  systems  in  gen- 
eral, in  anticipation  of  the  1977  Mariner  Jupiter/ Saturn  mission,  later  known  as  Voyager. 

The  interpretation  of  the  JPL  radar  experiment  on  Saturn's  rings  surprised 
astronomers32  and  caused  rethinking  about  the  ring  particles  and  models  published  by 
radio  astronomers.  The  amazingly  large  particle  size  also  raised  questions  about  the  safe- 
ty of  a  spacecraft  near  the  rings  and  gave  rise  to  NASA  and  JPL  interest  in  the  radar  results, 
which  George  Morris  discussed  at  the  workshop.  Excited  by  the  Goldstone  radar  findings, 
astronomers  during  the  general  discussion  expressed  an  interest  in  obtaining  more  radar 
data  on  the  rings.33 

The  JPL  results  also  surprised  radar  astronomers.  For  example,  Gordon  Pettengill 
(MIT )  and  Tor  Hagfors  (then  at  the  Department  of  Electrical  Engineering  of  the  Norges 
Tekniske  Hogskole,  Trondheim,  Norway) ,  based  on  their  own  radar  experience  with  the 
terrestrial  planets  and  the  asteroids  Icarus  and  Toro,  felt  that  the  radar  cross  section 
observed  by  Goldstein  and  Morris,  0.62  ±  0.15,  was  unreasonably  high.  "Even  by  assuming 
the  particulate  matter  in  the  rings  to  have  linear  dimensions  comparable  to  or  larger  than 
the  radar  wavelength,"  they  wrote,  "we  are  left  with  the  need  to  explain  a  radar  scattering 
mechanism  more  efficient  by  a  factor  of  about  10  than  that  of  the  inner  planets,  unless  we 
wish  to  postulate  an  unreasonable  ring  particle  density  or  composition."34 

Astonished,  too,  were  radio  astronomers.  The  high  radar  return  had  to  be  reconciled 
with  the  rings's  low  radio  emission,  as  well  as  with  optical  and  infrared  results.35  As  the 
enigma  of  Saturn's  rings  continued  to  puzzle  astronomers,  the  Arecibo  S-band  upgrade 
reached  completion.  It  seemed  only  natural,  as  Don  Campbell  explained,  that  the  first 
radar  experiment  with  the  upgraded  telescope  should  be  an  attempt  to  detect  echoes 
from  the  rings  of  Saturn:  "When  Arecibo  first  came  on  line  in  1974,  the  very  first  thing  we 
did  to  test  the  transmitting  system,  apart  from  trying  to  communicate  with  a  star  system 
25,000  light  years  away,  was  to  run  a  bistatic  radar  measurement  on  the  rings  of  Saturn 


31.  Goldstein  and  Morris,  "Radar  Observations  of  the  Rings  of  Saturn,"  Icarus  20  (1973):  260-262; 
Morris,  "Distribution  and  Size  of  Elements  of  Saturn's  Rings  as  Inferred  from  12-cm  Radar  Observations,"  in 
Frank  Don  Palluconi  and  Pettengill,  eds.,  The  Rings  of  Saturn,  SP-343  (Washington:  NASA,  1974),  p.  73. 

32.  Campbell  8  December  1993.  See,  for  example,  Allan  F.  Cook,  Fred  A.  Franklin,  and  F.  D.  Palluconi, 
"Saturn's  Rings:  A  Survey,"  Icarus  19  (1973):  317-337  and  Pollack,  "The  Rings  of  Saturn,"  American  Scientist  66 
(1978):  30-37. 

33.  Rasool,   "Foreword,"  in  Palluconi   and   Pettengill,   pp.  v-vi;   ibid.,   pp.    192-195;   and   Morris, 
"Distribution  and  Size  of  Elements  of  Saturn's  Rings  as  Inferred  from  12-cm  Radar  Observations,"  pp.  73-82. 
Interestingly,  when  a  subsequent  workshop  on  Saturn's  rings  was  held  at  the  Reston  International  Conference 
Center,  Reston,  Virginia,  9-11  February  1978,  and  sponsored  by  the  NASA  Office  of  Space  Science,  no  radar  pre- 
sentations were  made.  The  purpose  of  the  workshop  was  more  tightly  defined  than  the  1973  workshop;  the  1978 
workshop  strictly  prepared  for  the  Voyager  mission. 

34.  Pettengill  and  Hagfors,  "Comment  on  Radar  Scattering  from  Saturn's  Rings,"  Icarus  21  (1974): 
188-190,  esp.  188. 

35.  Jeffrey  N.  Cuzzi  and  David  Van  Blerkom,  "Microwave  Brightness  of  Saturn's  Rings,"  Icarus  22  (1974): 
149-158;  Pollack,  A.  L.  Summers,  and  B.  Baldwin,  "Estimates  of  the  Size  of  the  Particles  in  the  Rings  of  Saturn 
and  their  Cosmogonic  Implications,"  Icarus  20  (1973):  263-279;  Morrison  and  D.  P.  Cruikshank,  "Physical 
Properties  of  the  Natural  Satellites,"  Space  Science  Review  15  (1974):  722-732;  Pollack,  The  Rings  of  Saturn,"  Space 
Science  Review  18  (1975):  3-97. 


214  fTO  SEE  THE  UNSEEN 


with  Goldstone.  At  that  time,  we  had  transmitting  capability,  but  we  had  not  yet  installed 
the  receivers.  The  dedication  of  the  upgraded  telescope  had  been  in  November  1974,  and 
this  was  in  December,  when  we  were  trying  to  get  the  transmitter  really  working  properly."36 

Despite  equipment  difficulties  at  Arecibo,  Goldstone  received  echoes  from  Arecibo 
by  way  of  Saturn.37  In  addition  to  the  bistatic  Arecibo-Goldstone  radar  test  on  Saturn's 
rings  in  December  1974,  Arecibo  and  Goldstone  performed  dual-polarization  experi- 
ments on  two  nights  in  January  1975.  These  bistatic  linear  polarization  experiments  estab- 
lished that  echoes  from  the  rings  of  Saturn  were  highly  depolarized,  that  is,  more  power 
appeared  in  the  unexpected  than  in  the  expected  polarization. 

Goldstein  also  conducted  monostatic  dual-polarization  observations  with  the 
Goldstone  X-band  radar  on  five  nights  in  December  1974  and  January  1975  and  measured 
a  high  circular  polarization  ratio.  Goldstone  and  Arecibo  investigators  now  knew  that 
Saturn's  rings  exhibited  high  linear  and  circular  polarization  ratios  and  that  the 
phenomenon  was  independent  of  frequency.  Moreover,  they  confirmed  at  both  X-band 
and  S-band  that  the  rings  had  high  radar  cross  sections.38 

The  high  radar  cross  sections  and  polarization  ratios  of  Saturn's  rings  were  puzzling. 
Campbell  and  Goldstein  considered  several  possible  explanations  for  those  radar  proper- 
ties. Two  models  appeared  plausible.  One  model  hypothesized  a  thick  cloud  of  irregular 
water-ice  chunks  a  few  centimeters  or  larger  in  radius.  The  other  posited  a  monolayer  of 
multimeter-sized  water-frost-coated  metallic  chunks.  Voyager  data  later  rejected  the  metal- 
lic composition  of  the  rings.39  In  summing  up  the  state  of  knowledge  on  Saturn's  rings  in 
1975,  Allan  F.  Cook  and  Fred  A.  Franklin  of  the  Smithsonian  Astrophysical  Observatory 
speculated  that  the  ring  particles  consisted  of  water  ice,  clathrated  hydrates  of  methane, 
and  ammonia  hydrates,40  in  agreement  with  one  of  the  radar  models. 

Meanwhile,  James  Pollack  and  other  astronomers  proposed  that  the  ring  system  was 
diffuse  and  many  particles  thick.  In  order  to  determine  whether  the  rings  of  Saturn  con- 
sisted of  one  or  several  layers,  and  in  general  to  test  various  models  of  the  thickness  and 
composition  of  the  rings,  Gordop  Pettengill,  Don  Campbell,  and  Steve  Ostro  undertook 
further  radar  observations  in  1977,  1978,  and  1979  on  a  total  of  13  nights.  Like  those  on 
the  Galilean  satellites  of  Jupiter,  the  observations  became  part  of  Ostro's  thesis.41  In 
March  1977,  also,  Gordon  Pettengill  and  Dick  Goldstein  resumed  bistatic  observations  of 
Saturn's  rings  with  the  Arecibo  and  Goldstone  S-band  radars.42 

The  key  to  the  radar  observations  made  in  1977, 1978,  and  1979  was  the  differing  tilt 
angles  of  the  rings  during  the  1 3  total  nights  of  observations.  The  tilt  angle  of  the  rings 
relative  to  the  line  of  sight  declined  over  those  three  years  from  18.2°  to  11.7°,  then  to 
5.6°.  The  astronomers  also  received  in  both  senses  of  circular  polarization  in  order  to 
measure  the  polarization  ratio  as  a  function  of  tilt  angle.  Their  results,  when  combined 


36.  Campbell  7  December  1993. 

37.  NAICQRQ1/1975,  4. 

38.  Goldstein,  R.  Green,  Pettengill,  and  Campbell,   "The  Rings  of  Saturn:  Two-Frequency  Radar 
Observations, "Icarus 30  (1977):  104-110. 

39.  L.  W.  Esposito,  Cuzzi,  J.  B.  Holberg,  E.  A.  Marouf,  Tyler,  and  C.  C.  Porco,  "Saturn's  Rings:  Structure, 
Dynamics,  and  Particle  Properties,"  in  Tom  Gehrels  and  Mildred  Shapley  Matthews,  eds.,  Saturn  (Tucson: 
University  of  Arizona  Press,  1984),  p.  46(j. 

40.  Allan  F.  Cook  and  Fred  A.  Franklin,  "Saturn's  Rings:  A  New  Survey,"  in  Joseph  A.  Burns,  ed., 
Planetary  Satellites  (Tucson:  University  of  Arizona  Press,  1977),  pp.  412-419.  See  also  Cuzzi  and  Pollack,  "Saturn's 
Rings:  Particle  Composition  and  Size  Distribution  as  Constrained  by  Microwave  Observations."  Icarus  33  (1978): 
233-262.  , 

41.  Campbell  8  December  1993;  Esposito,  Cuzzi,  Holberg,  Marouf,  Tyler,  and  Porco,  "Saturn's  Rings: 
Structure,  Dynamics,  and  Particle  Properties,"  in  Gehrels  and  Matthews,  Saturn,  p.  467;  NAIC  QR  Ql/1978,  7; 
NAIC  QR  Ql/1979,  9;  Ostro,  "The  Structure  of  Saturn's  Rings,"  pp.  105-157. 

42.  NAIC  QRQ1 /1977,7. 


THE  OUTER  LIMITS  215 


with  earlier  radar  data  and  the  theoretical  calculations  of  Jeffrey  N.  Cuzzi  and  James 
Pollack,43  provided  significant  constraints  on  ring  structure. 

The  observations  confirmed  that  the  radar  reflectivity  of  the  rings  was  quite  high  and 
that  depolarization  was  also  high.  The  polarization  ratio  for  the  Galilean  satellites,  a 
mystery  not  yet  solved,  however,  was  higher.  The  data  ruled  out  all  large-particle  mono- 
layer  models.  On  the  other  hand,  the  polarization  and  radar  cross  section  results  favored 
ring  models  of  several  layers.  The  radar  data  also  appeared  to  support  particle  composi- 
tion of  ice  or  metal,  but  not  silicate  rock.44 

Ostro,  Pettengill,  and  Campbell  also  concluded  that  the  A  and  B  rings  (the  outer- 
most rings)  were  responsible  for  most,  if  not  all,  of  the  S-band  radar  echoes,  and  that  the 
radar  reflectivity  of  the  A  ring  was  nearly  as  great  as  the  B-ring  radar  reflectivity.  The  radar 
reflectivity  of  the  C  ring  was  notably  less  than  that  of  the  B  ring.  Also,  they  found  no  evi- 
dence for  radar  echoes  from  beyond  the  A  ring  or  from  the  planet  itself.45 

The  case  of  Saturn's  rings  resulted  in  radar  astronomers  contributing  to  planetary 
science,  in  contrast  to  their  studies  of  the  Galilean  moons.  Those  studies  for  a  long  time 
had  been  limited  to  epistemological  issues,  namely,  what  caused  the  Galilean  moons' 
strange  radar  signatures?  Radar  contributed  to  Saturn  science,  on  the  other  hand,  by 
focusing  less  on  such  questions  of  radar  technique  and  more  on  scientific  questions,  such 
as  the  size  of  the  ring  particles  and  the  number  and  thickness  of  the  ring  layers.  Although 
the  solution  of  technical  problems  was  a  prerequisite  for  any  radar  astronomy  problem 
solving,  the  lack  of  obvious  relevance  to  planetary  science  was  a  serious  matter;  the  abili- 
ty to  solve  scientific  problems,  especially  those  relating  to  NASA  space  missions,  was  the 
basis  on  which  scientists  judged  the  value  of  radar  astronomy  and  on  which  funding  deci- 
sions were  made. 


Cometary  Nuclei 


The  nuclei  of  comets  provided  radar  astronomers  additional  icy  research  subjects. 
Comets  are  believed  to  represent  samples  of  the  most  primitive  material  of  the  solar  neb- 
ula and  to  hold  clues  to  the  origin  of  the  solar  system.46  They  make  challenging  radar 
targets,  because  close  approaches  are  rare.  The  relatively  small  size  of  comets  dictates  that 
they  be  studied  by  radar  only  when  they  approach  Earth  at  distances  of  a  fraction  of  an 
astronomical  unit.  Also,  ephemerides  derived  from  optical  data  lack  the  accuracy 
demanded  for  radar  observations.  Only  the  S-band  and  X-band  upgrades  of  the  Arecibo 
and  Goldstone  antennas  made  radar  studies  of  comets  possible. 


43.  Cuzzi  and  Pollack,  "Saturn's  Rings:  Particle  Composition  and  Size  Distribution  as  Constrained  by 
Microwave  Observations."  Icarus  33  (1978):  233-262. 

44.  Ostro,  Pettengill,  and  Campbell,  "Radar  Observations  of  Saturn's  Rings  at  Intermediate  Tilt 
Angles,"  Icarus  41  (1980):  381-388. 

45.  Ostro,  Pettengill,  Campbell,  and  Goldstein,  "Delay-Doppler  Radar  Observations  of  Saturn's  Rings," 
Icarus  49  ( 1982) :  367-381 .  See  also  Ostro  and  Pettengill,  "A  Review  of  Radar  Observations  of  Saturn's  Rings,"  in 
A.  Brahic,  ed.,  Planetary  Rings  1982  (Toulouse:  CEPADUES  Editions,  1982),  pp.  49-55. 

Later  radar  data  collected  at  Goldstone  by  Goldstein  and  Jurgens  and  at  Arecibo  by  Ostro,  Pettengill,  and 
Campbell  in  1981,  when  the  rings  were  at  a  6°  tilt  angle,  confirmed  that  the  ring  particles  were  large,  irregular, 
and  jagged  in  shape  and  made  of  ice;  the  researchers  finally  abandoned  the  notion  that  they  might  be  metallic. 
Moreover,  they  affirmed  the  conclusion  that  the  A  and  B  rings  reflected  most,  if  not  all,  of  the  radar  echo  from 
Saturn's  rings.  Goldstein  and  Jurgens,  "Radar  Observations  of  the  Rings  of  Saturn, "  Journal  of  Geophysical  Research 
submitted  for  publication;  Ostro,  Pettengill,  Campbell,  and  Goldstein,  "Delay-Doppler  Radar  Observations  of 
Saturn's  Rings,"  Icarus  49  (1982):  367-381;  Ostro,  Pettengill,  and  Campbell,  "Radar  Observations  of  Saturn's 
Rings  at  Intermediate  Tilt  Angles,"  Icarus  41  (1980):  381-388.  This  research  is  summarized  in:  Ostro  and 
Pettengill,  "A  Review  of  Radar  Observations  of  Saturn's  Rings,"  pp.  49-55. 

46.  Whipple,  "Comets,"  in  J.  A.  M.  McDonnell,  ed.,  Cosmic  Dust  (New  York:  John  Wiley  &  Sons,  1978), 
pp.  1-73. 


216  TO  SEE  THE  UNSEEN 


Early  attempts  all  ended  in  failure.  For  example,  after  an  attempt  in  January  1971  on 
Comet  Kohoutek  stymied  by  rain  and  snow,  the  Haystack  telescope  again  failed  to  detect 
that  comet  in  January  1974.  Although  Irwin  Shapiro  had  prepared  an  accurate  ephemeris 
in  advance,  neither  the  bandwidth  nor  the  center  frequency  of  the  radar  echo  was  known 
precisely,  so  they  had  to  search  for  the  echo.47 

It  took  the  S-band  upgrade  of  the  Arecibo  Observatory  to  make  the  first  comet  detec- 
tions possible.  Paul  G.  D.  Kamoun,  a  French  student  of  Gordon  Pettengill  at  MIT,  built  his 
dissertation  research  around  those  detections.  The  main  objective  of  his  dissertation  was 
to  use  cometary  radar  data  to  discriminate  between  two  different  models  of  cometary 
nuclei.48  One  model  was  that  proposed  by  Fred  Whipple,  who  served  on  Kamoun's  dis- 
sertation committee,  and  supported  by  Zdenek  Sekanina,  an  established  expert  on 
comets. 

In  the  Whipple  model,  the  cometary  nucleus  was  like  a  rotating  "dirty  snowball,"  an 
icy  matrix  of  water  ammonia,  methane,  carbon  dioxide,  or  carbon  monoxide,  combined 
with  rock,  dust  and  other  meteoric  debris.  A  popular  model  for  the  nucleus  in  the  early 
20th  century  predicated  a  "dust  swarm"  or  swarm  of  solid  particles  of  unknown  sizes,  each 
particle  carrying  with  it  an  envelope  of  gas,  mostly  hydrocarbons.  However,  that  model 
had  a  number  of  difficulties,  and  by  the  1970s  Whipple's  "dirty  snowball"  model  pre- 
vailed.49 Consequently,  Kamoun's  dissertation  did  not  contribute  meaningfully  to  the 
comet  debate. 

Kamoun's  research  on  comets  turned  around  the  unsuccessful  cometary  research 
begun  at  Arecibo  by  Gordon  Pettengill,  Brian  Marsden  (Harvard-Smithsonian 
Astrophysical  Observatory) ,  and  Irwin  Shapiro  (who  prepared  the  ephemerides) .  In  late 
July  1976,  they  attempted  to  detect  echoes  from  Comets  d'Arrest  and  Grigg-Skjellerup 
during  three  observing  sessions.  Both  attempts  failed,  although  Comet  d'Arrest  came 
within  0.15  astronomical  units  of  Earth.50 

The  first  comet  detected  by  radar  was  Comet  Encke.  As  Don  Campbell  explained,  "It 
was  a  historic  first.  We  had  never  actually  seen  a  comet  before."51  French  and  German 
astronomers  had  observed  Encke  earlier;  its  name  came  from  the  German  mathematician 
and  physicist  Johann  Encke,  who  initially  suggested  an  elliptical  orbit  with  a  period  of  12.2 
years,  then  correctly  recalculated  an  elliptical  orbit  of  3.3  years,  the  shortest  period  of  any 
known  comet.52  Comet  Encke  was  due  back  in  November-December  1980.  Although 
Encke  had  a  relatively  stable  and  therefore  predictable  orbit,  optical  observations  were 
neither  sufficiently  numerous  nor  sufficiently  accurate  to  formulate  a  satisfactory 
ephemeris  for  the  radar.  Irwin  Shapiro  and  Antonia  Forni  (Lincoln  Laboratory)  based 
the  radar  ephemerides  on  optical  data  from  both  past  appearances  and  new  observations 
associated  with  the  1980  appearance  supplied  by  Brian  Marsden.  The  ephemeris  difficul- 
ties resolved,  Kamoun,  Campbell,  and  Ostro  observed  Encke  for  12  hours  on  seven  con- 
secutive days,  2-8  November  1980,  about  30  days  before  the  comet  reached  perihelion 
and  at  a  distance  of  slightly  more  than  0.3  astronomical  units  from  Earth.  They  found  dis- 
tinct, but  very  weak,  echoes  during  each  observing  session.53 


47.  Log  book,  Haystack  Planetary  Radar,  HR-73-2,  9  December  1970  to  11  August  1971,  SEBRING; 
Shapiro  1  December  1993;  Eric  J.  Chaisson,  Ingalls,  Rogers,  and  Shapiro,  "Upper  Limit  on  the  Radar  Cross 
Section  of  the  Comet  Kohoutek,"  Icarus  24  (1975):  188-189. 

48.  Paul  Gaston  David  Kamoun,  "Radar  Observations  of  Cometary  Nuclei,"  Ph.D.  diss.,  MIT,  May  1983. 

49.  Whipple,  "A  Comet  Model.  I.  The  Acceleration  of  Comet  Encke,"  Astrophysical  Journal  111  (1950): 
375-394;  Whipple,  "A  Comet  Model.  II.  Physical  Relations  for  Comets  and  Meteors,"  ibid.,  113  (1951):  464-474. 

50.  Kamoun,  p.  31;  NAIC  QR  Q3/1976,  6-7. 

51.  Campbell  9  December  1993. 

52.  John  E.  Bortle,  "Comet  Digest,"  Sky  and  Telescope  60  (1980):  290;  Kamoun,  pp.  37-38. 

53.  Kamoun,  p.  51;  Kamoun,  Campbell,  Ostro,  Pettengill,  and  Shapiro,  "Comet  Encke:  Radar  Detection 
of  Nucleus,"  Science  216  (1982):  293-295;  NAIC  QR  Q4/1980,  8-9. 


THE  OUTER  LIMITS  2 1 7 


Next,  Kamoun  attempted  radar  observations  of  the  Comet  Grigg-Skjellerup,  which 
was  discovered  in  1902  by  Grigg  in  New  Zealand,  then  re-discovered  as  a  new  comet  in 
1922  by  Skjellerup  in  South  Africa.  Grigg-Skjellerup  has  an  orbital  period  of  5.1  years, 
making  it  the  second  shortest  periodic  comet  after  Encke.  The  time  of  perihelion  passage 
was  15  May  1982,  at  a  perihelion  distance  of  nearly  one  astronomical  unit  (0.989). 

Compared  to  other  cometary  experiments,  Kamoun  spent  an  unprecedented  and 
never  repeated  49  hours  observing  the  comet  between  20  May  and  2  June  1982,  about  a 
week  after  it  passed  perihelion,  while  the  comet  was  about  0.33  astronomical  units  from 
Earth.  He  received  echoes  in  both  senses  of  circular  polarization,  but  technical  problems 
prevented  the  acquisition  of  data  on  five  days.  An  interesting  feature  was  the  very  narrow 
(less  than  one  Hz)  Doppler  bandwidth  of  the  echo,  which  indicated  either  a  very  specu- 
lar echo,  a  slow  rotation  rate,  or  collinearity  of  the  polar  axis  with  the  line-of-sight.54 

Comet  Austin  came  next.  Unlike  Encke  and  Grigg-Skjellerup,  Comet  Austin  had 
only  been  discovered  on  the  morning  of  19  June  1982  by  Rodney  Austin  in  New  Zealand. 
Alan  Gilmore,  of  Mount  John  University  Observatory,  New  Zealand,  confirmed  the  dis- 
covery. The  comet  was  first  reported  on  21  June  1982  in  IAU  circular  3705  of  the  Central 
Bureau  for  Astronomical  Telegrams  by  Brian  Marsden,  who  also  computed  and  made  pub- 
lic a  set  of  orbital  elements  showing  that  the  comet  was  moving  on  a  parabolic  orbit.  From 
the  Marsden  ephemeris,  it  appeared  that  Comet  Austin  would  pass  close  enough  to  Earth 
to  detect  it  with  the  Arecibo  radar. 

Following  receipt  of  IAU  circular  3706  containing  the  improved  elements  of  the 
comet's  orbit,  Kamoun  undertook  the  task  of  obtaining  telescope  time.  He  attempted  to 
observe  the  comet  on  the  mornings  of  8-12  August  1982.  Despite  equipment  problems 
that  plagued  observations  on  8  and  9  August,  the  last  three  days  yielded  normal 
performance.  On  the  last  day,  12  August,  the  analyzing  bandwidth  was  doubled  from  380 
to  760  hz,  with  a  corresponding  increase  in  the  frequency  resolution,  in  order  to  widen 
the  search  window.  They  computed  an  ephemeris  after  the  experiment,  using  all  the  astro- 
metric  observations  available  for  Comet  Austin  between  June  1982  and  November  1982. 
That  ephemeris  turned  out  to  be  substantially  different  from  the  ephemeris  used  during 
the  actual  radar  observations.  Despite  correcting  for  this,  and  despite  the  distance  from 
Earth  being  very  similar  to  that  of  Comets  Encke  and  Grigg-Skjellerup,  five  days  of  obser- 
vations in  August  1982  did  not  result  in  a  successful  detection.55 

Radar  detections  of  comets  were  obviously  fairly  difficult  to  make,  even  with  the  best 
radar  telescope  then  available.  Another  opportunity  to  attempt  a  newly-discovered  comet 
came  later  that  year.  Comet  Churyumov-Gerasimenko  was  discovered  on  a  photograph 
taken  on  11  September  1969  at  the  Alma-Ata  observatory  in  the  Soviet  Union  by  K.  I. 
Churyumov  and  S.  I.  Gerasimenko.  At  the  time  of  Kamoun's  radar  observations  in 
November  1982,  Comet  Churyumov-Gerasimenko  was  0.39  astronomical  units  from 
Earth.  It  ought  to  have  been  detectable  by  the  Arecibo  radar.  Kamoun  attempted  Comet 
Churyumov-Gerasimenko  for  33  hours  between  7  and  16  November  1982.  Serious  tech- 
nical problems  on  7  and  16  November  prevented  acquisition  of  data.  Further  difficulties 
on  8  and  1 1  November  caused  loss  of  some  data.  In  the  end,  the  attempt  on  Comet 
Churyumov-Gerasimenko  was  not  successful.56 

From  his  successful  and  unsuccessful  observations  of  comets,  Kamoun  estimated  the 
radii  of  their  nuclei,  which  were  0.4-3.6  km  for  Encke,  0.4-2.2  km  for  Grigg-Skjellerup, 


54.  Kamoun,  pp.  90  and  85;  NAIC  QR  Q2/ 1982,  7-8. 

55.  Kamoun,  pp.  108-110;  NAIC  QR  Q3/1982,  8. 

56.  Kamoun,  pp.  21  and  122;  NAIC  QR  Q4/1982,  7-8;  K.  I.  Churyumov  and  S.  I.  Gerasimenko,  "Physical 
Observations  of  the  Short-Period  Comet  1969  IV,"  in  G.  A.  Chebotarev,  E.  I.  Kazimirchak-Polonskaya,  and  Brian 
G.  Marsden,  eds.,  The  Motion,  Evolution  of  Orbits,  and  Origin  of  Comets  IAU  Symposium  45  (New  York:  Springer- 
Verlag,  1972),  pp.  27-34.  Both  Churyumov  and  Gerasimenko  were  in  the  Department  of  Astronomy,  University 
of  Kiev. 


218 


TO  SEE  THE  UNSEEN 


less  then  1.5  km  for  Austin,  and  less  than  2  km  for  Churyumov-Gerasimenko.  He  also 
placed  upper  limits  on  the  number  of  millimeter  and  centimeter-sized  particles  in  the 
coma  of  the  four  comets  (Table  7)  .57 


Table  7 
Upper  Limits  on  the  Number  of  Grains  in  the  Coma  of  Four  Comets 

Comet 

Grain-Size 

Assumed 
Ice 

Grain 
Olivine 

Composition 
Magnetite 
Iron  Sulfide 

Encke 

mm 

cm 

4.5    10" 
1.5    10" 

1.5    10" 
6    10'° 

7.5    1016 
3    10'° 

Grigg-Skjellerup 
and  Austin 

mm 
cm 

3    10" 
10" 

1016 
4.5  10'° 

1016 
2    1010 

Churyumov- 
Gerasimenko 

mm 
cm 

6    10" 
2    10" 

2  10" 
9  10'° 

10" 
4    10'° 

In  setting  forth  a  program  of  future  cometary  radar  studies,  Kamoun  noted  that  the 
comets  attempted  in  his  dissertation  could  not  be  observed  again  during  the  next  10 
years.  Despite  the  scheduled  reappearances  of  Encke  in  1984  and  1987,  of  Grigg- 
Skjellerup  in  1987,  and  of  Churyumov-Gerasimenko  in  1989,  none  of  the  comets  would 
approach  close  enough  for  radar  observation.  On  the  other  hand,  he  calculated,  even  if 
no  improvement  in  radar  sensitivity  occurred,  other  comets  would  be  accessible, 
particularly  Comets  Haneda-Campos  (1984),  Giacobini-Zinner  (1985),  Borelly  and 
Denning-Fujikawa  (1987),  and  Brorsen-Metcalf  and  Dubiago  (1989). 58  None  of  those 
comets,  however,  was  ever  observed  by  radar. 

Instead,  opportunities,  in  fact  far  better  opportunities,  came  from  comets  never 
before  seen.  In  early  May  1983,  as  Paul  Kamoun  was  writing  his  dissertation,  preparations 
were  underway  at  Arecibo  to  observe  Comet  IRAS-Araki-Alcock.  On  25  April  1983,  the 
Infrared  Astronomical  Satellite  (IRAS)  discovered  Comet  IRAS-Araki-Alcock.  Initially,  sci- 
entists believed  it  was  an  asteroid.  In  either  case,  it  was  sure  to  approach  near  the  Earth. 
Astronomers  calculated  that  the  object  would  pass  Earth  at  a  distance  of  only  0.03 
astronomical  units  (450,000  km),  that  is,  about  10  times  closer  than  any  other  comet  that 
Kamoun  had  observed  for  his  dissertation.  In  fact,  such  a  close  approach  for  a  comet  had 
not  been  known  to  have  occurred  in  more  than  two  hundred  years.  Although  Kamoun 
had  pioneered  cometary  radar,  he  would  miss  the  most  spectacular  cometary  opportuni- 
ty. After  writing  up  his  thesis,  he  returned  to  France  and  took  a  position  with  a  French 
aerospace  firm.59 

But  observing  Comet  IRAS-Araki-Alcock  was  not  going  to  be  easy.  Its  orbit  was  high- 
ly inclined  relative  to  the  Earth's  equator,  and  to  make  observation  at  Arecibo  that  much 
harder,  as  Don  Campbell  explained,  "It  was  moving  in  declination  so  rapidly,  that  it 
actually  went  through  the  entire  sky  coverage  of  Arecibo  in  one  day.  We  had  a  two-and-a- 
half-hour  observing  window,  and  that  was  it!"60 


57.  Kamoun,  p.  230. 

58.  Kamoun,  p.  237. 

59.  Campbell  9  December  1993;  Kamoun,  p.  238;  Jurgens,  "Seeing  Comet  IRAS,"  p.  221;  information 
supplied  by  Pettengill. 

60.  Campbell  9  December  1993. 


THE  OUTER  LIMITS  2 1 9 


The  ability  to  get  good  data  on  Comet  IRAS-Araki-Alcock  depended  heavily  on  hav- 
ing an  accurate  ephemeris.  That  was  the  job  of  Brian  Marsden  and  Irwin  Shapiro,  who 
had  just  become  Director  of  the  Harvard-Smithsonian  Astrophysical  Observatory  in 
January  1983,  four  months  before  the  comet's  discovery.  'Taking  over  this  place  was  an 
all-consuming  job,"  he  recalled.  "I  worked  day  and  night.' But  for  a  few  days,  I  dropped  this 
job  like  a  ton  of  bricks,  literally,  to  develop  the  ephemeris  needed  to  observe  IRAS- 
Araki-Alcock  at  Arecibo  and  Goldstone."61 

Working  closely  with  Brian  Marsden,  Shapiro  generated  an  ephemeris  for  the  comet. 
"It  was  a  big  mess,"  Shapiro  explained.  "I  was  up  until  2:30  in  the  morning  every  night. 
The  difficulty  was  due  to  there  being  very  few  comet  observations,  mostly  bad.  We  had  to 
try  numerous  combinations  to  sort  the  good  from  the  bad."  Then  Shapiro  turned  to  the 
task  of  preparing  an  ephemeris  for  the  radar.  'The  radar  ephemeris  was  prepared  at 
Lincoln  Laboratory;  the  radar  observations  were  to  be  made  at  Arecibo.  It  was  a  logistical 
nightmare,  because  of  the  incredible  time  pressure,"  Shapiro  explained.  "As  the  time  of 
close  approach  of  the  comet  to  Arecibo  neared,  we  sent  the  ephemeris  electronically.  It 
arrived  an  hour  before  the  comet  was  to  make  its  one  and  only  pass  over  head.  It  worked 
brilliantly."62 

Don  Campbell  took  high  quality  data  on  IRAS-Araki-Alcock  for  about  three  hours 
during  the  single  observation  evening  of  1 1  May  when  the  comet  was  in  the  telescope's 
declination  window.  Campbell  recalled:  "We  got  extremely  nice  data.  You  could  actually 
see  the  echo  on  the  oscilloscope  right  there  in  the  control  room.  It  was  all  over  the  place. 
A  nice  sine  wave  popping  in  and  out.  It  was  all  very  exciting.  We  measured  only  spectra 
and  obtained  a  lot  of  very  interesting  data  on  IRAS-Araki-Alcock  in  just  that  two-hour 
period."63 

More  surprising  than  a  powerful  echo  from  a  relatively  large  nucleus,  the  spectra 
showed  a  broad  low-level  skirt  distinct  from  the  nucleus  echo.  The  skirt  suggested  the 
possible  existence  of  a  cloud  of  unexpectedly  large,  centimeter-sized  ejected  particles 
from  the  comet.  The  IRAS-Araki-Alcock  skirt  spectrum  appeared  to  be  consistent  with  a 
model  in  which  large  grains  were  ejected  from  the  nucleus  by  the  same  gas-drag  mecha- 
nism used  to  explain  the  ejection  of  the  smaller  particles  making  up  the  dust  coma  and 
tail.64  'This  was  the  first  time  that  such  particles  had  ever  been  discovered,"  Campbell 
explained.  "It  made  the  whole  experiment  much  more  interesting."65 

At  the  same  time,  Dick  Goldstein  and  Rayjurgens,  in  collaboration  with  JPL  comet 
specialist  Zdenek  Sekanina,  prepared  to  look  at  IRAS-Araki-Alcock  with  the  Goldstone 
radar.  Previously,  they  had  made  failed  attempts  at  Comets  d'Arrest  (1976),  Kohoutek 
(1974),  and  Bradfield  (1974).66  IRAS-Araki-Alcock  would  be  their  first  successful 
cometary  detection.  Their  chief  obstacle  was  the  resuscitation  the  Goldstone  radar.  As 
Jurgens  wrote:  "As  luck  would  have  it,  the  JPL  radar  system  had  been  shut  down  following 


61.  Shapiro  1  October  1993. 

62.  Shapiro  1  October  1993. 

63.  Campbell  9  December  1993;  Harmon,  Campbell,  Hine,  Shapiro,  and  Marsden,  "Radar  Observations 
of  Comet  IRAS-Araki-Alcock  1983d,"  The  Astrophysical  Journal  338  (1989):  1071;  Harmon,  Campbell,  Hine, 
Shapiro,  and  Marsden,   Radar  Observations  of  Comet  IRAS-Araki-Alcock  (1983d)  Report  245   (Ithaca:  NAIC. 
September  1988),  Pettengill  materials. 

64.  Campbell  9  December  1993;  NAIC  QR  Q2/1983,  7;  Harmon,  Campbell,  Hine,  Shapiro,  and 
Marsden,  "Radar  Observations  of  Comet  IRAS-Araki-Alcock  1983d,"  The  Astrophysical  Journal  338  (1989):  1071- 
1093;  Campbell,  Harmon,  Hine,  Shapiro,  Marsden,  and  Pettengill,  "Arecibo  Radar  Observations  of  Comets 
IRAS-Araki-Alcock  and  Sugano-Saigusa-Fujikawa,"  Bulletin  of  the  American  Astronomical  Society  15  (1983):  800; 
Goldstein,  Jurgens,  and  Zdenek  Sekanina,  "A  Radar  Study  of  Comet  IRAS-Araki-Alcock  1983d,"  The  Astronomical 
Journal^  (1984):  1745-1754;  and  Shapiro,  Marsden,  Whipple,  Campbell,  Harmon,  and  Hine,  "Interpretations 
of  Radar  Observations  of  Comets,"  Bulletin  of  the  American  Astronomical  Society  15  (1983):  800. 

65.  Campbell  9  December  1993. 

66.  Jurgens,  "Seeing  Comet  IRAS,"  p.  221;  Goldstein,  Jurgens,  and  Sekanina,  pp.  1745-1754. 


220  TO  SEE  THE  UNSEEN 


the  unsuccessful  tracks  of  asteroid  4  Vesta  on  28  May  1982.  Since  the  radar  system  has  seen 
only  sporadic  usage  over  the  past  few  years,  the  X-band  transmitter,  the  20  year  old 
computer  and  the  data  acquisition  equipment  were  unreliable.  We  were  in  the  midst  of  a 
major  rebuilding  project  that  would  not  be  put  into  operation  until  March  1985. 
Fortunately,  we  had  not  removed  the  old  equipment."67 

Jurgens  and  a  team  of  JPL  engineers  refurbished  the  radar  equipment,  while  Mike 
Keesey  prepared  a  radar  ephemeris  based  on  orbital  elements  supplied  by  Brian  Marsden 
and  Irwin  Shapiro,  who  also  had  supplied  the  Arecibo  ephemeris.  The  Goldstone  obser- 
vations took  place  on  11  and  14  May  1982  at  both  S-band  and  X-band.  On  a  few  runs, 
echoes  were  received  in  the  same  circular  polarization.68  Goldstein,  Jurgens,  and  Sekanina 
concluded  that  the  nucleus  of  Comet  IRAS-Araki-Alcock  was  very  rough  on  a  scale  larger 
than  the  radar  wavelength.  They  did  not  believe  that  the  predominant  backscattering 
mechanism  was  similar  to  that  observed  from  the  icy  surfaces  of  the  Galilean  satellites,  but 
instead  consisted  of  single  reflections  from  very  rough  surfaces.  They  posited,  further- 
more, that  the  shape  of  the  nucleus  appeared  to  be  irregular.  Jurgens  believed  that  the 
nucleus's  shape  could  be  represented  fairly  well  by  a  triaxial  ellipsoid  having  equatorial 
radii  in  a  ratio  of  two  to  one.  The  JPL  radar  astronomers  estimated  its  radius  to  be  between 
three  and  six  km  (larger  than  any  comet  observed  by  Ramoun)  and  its  rotational  period 
to  be  from  one  to  two  days. 

Because  of  Jurgens'  interest  in  asteroids,  he  and  his  JPL  colleagues  compared  the 
comet  to  known  asteroids.  'The  observed  spectral  shapes  are  typical  of  those  measured  for 
small  Earth-crossing  asteroids  except  for  the  broadband  skirt,"  they  noted.  "Due  to  dis- 
tance and  sensitivity  limitations,  such  a  skirt  would  not  have  been  detected  on  any  aster- 
oid observed  so  far  even  if  it  existed."69  However,  they  did  not  carry  out  a  detailed  analy- 
sis of  the  skirt. 

Within  weeks  after  Comet  IRAS-Araki-Alcock,  another  new  comet,  Sugano-Saigusa- 
Fujikawa,  passed  the  Earth.  The  two  comets  coming  so  closely  together  created  a  "once  in 
a  lifetime"  opportunity.  Comet  Sugano-Saigusa-Fujikawa  came  within  0.06  astronomical 
units  of  Earth  in  early  June  1983.  Don  Campbell  attempted  Sugano-Saigusa-Fujikawa  on 
the  one  day  it  was  within  the  Arecibo  telescope's  declination  window,  while  Jurgens  and 
Goldstein  tried  during  four  full  days  of  observations,  which  delayed  the  renovation  of  the 
Mars  Station  antenna  for  one  month.  "Night  after  night,"  Jurgens  wrote,  "we  searched  the 
sky  in  the  area  of  the  comet  with  no  indication  of  an  echo."70  Arecibo,  on  the  other  hand, 
did  find  echoes;  however,  Sugano-Saigusa-Fujikawa  was  about  three  times  further  away 
than  IRAS-Araki-Alcock  had  been,  and  it  was  a  smaller  comet,  so  that  it  was  a  less  inter- 
esting and  "somewhat  disappointing"  target.71 

Despite  the  many  unsuccessful  and  disappointing  attempts  to  detect  comets,  until 
the  passing  of  Comet  Halley,  only  the  radar  observations  of  IRAS-Araki-Alcock  made  at 
Arecibo  and  Goldstone  contributed  to  the  vast  amount  of  data  collected  by  comet  scien- 
tists at  optical,  radio,  infrared,  and  ultraviolet  wavelengths.72  Comet  Halley  returns  every 
76  years.  Its  reappearance  prompted  a  global  effort,  the  International  Halley  Watch,  to 
coordinate  ground  and  space  observations.  Unlike  previous  comets,  Halley  was  investi- 
gated from  a  number  of  spacecraft  sent  by  Japan  (Suisei  and  Sakigake),  the  Soviet  Union 
(Vega  1  and  2),  and  the  European  Space  Agency  (Giotto).  The  radar  results,  however,  did 


67.  Jurgens,  "Seeing  Comet  IRAS,"  p.  222. 

68.  Jurgens,  "Seeing  Comet  IRAS,"  p.  222;  Goldstein,  Jurgens,  and  Sekanina,  pp.  1745-1747. 

69.  Goldstein,  Jurgens,  and  Sekanina,  p.  1754. 

70.  Jurgens,  "Seeing  Comet  IRAS,"  p.  224. 

71.  Campbell  9  December  1993;  NAIC  QR  Q2/1983,  7. 

72.  Sekanina,  "Nucleus  of  Comet  IRAS-Araki-Alcock  (1983  VII),"  The  Astronomical  Journal  95  (1988): 
1876-1894. 


THE  OUTER  LIMITS  221 


not  play  a  part  in  the  international  effort.73  Radar  was  still  a  marginal  tool  for  cometary 
research. 

Comet  Halley  was  to  make  two  close  approaches  to  Earth  during  its  appearance  in 
1985-1986.  At  its  closest  approach  in  November  1985,  it  was  to  be  0.61  astronomical  units 
from  Earth,  and  during  its  second  approach,  even  closer,  0.41  astronomical  units,  to  Earth 
in  April  1986.  At  the  November  1985  approach,  Halley  would  be  visible  at  both  Arecibo 
and  Goldstone,  though  far  below  likely  detectability  at  the  latter  site.  Moreover,  Halley  was 
not  within  the  Arecibo  telescope's  limited  declination  coverage  during  its  closer  approach 
to  Earth  in  April  1986.74  The  chances  for  viewing  Halley  thus  were  small;  the  best  chance 
was  in  November  and  December  1985,  when  Halley  was  to  be  0.62  astronomical  units  dis- 
tant from  Earth,  not  a  good  distance  for  observing  comets. 

At  Arecibo,  John  Harmon  observed  Halley  on  24,  28,  29  November  and  1  and  2 
December  1985  during  its  inbound  Earth  approach  and  detected  a  weak  echo  from  Halley 
at  a  distance  of  0.62  to  0.64  astronomical  units,  the  most  distant  comet  yet  detected  with 
radar.  With  the  exception  of  IRAS-Araki-Alcock,  comets  observed  earlier  generally  had 
been  about  0.3  astronomical  units  away.  A  broadband  feature  with  a  high  radar  cross  sec- 
tion and  a  large  Doppler  bandwidth  dominated  the  echo  spectrum,  properties  that  were 
inconsistent  with  an  echo  from  the  nucleus.  Halley,  then,  became  the  second  comet  to 
yield  a  radar  detection  of  grains  larger  than  two  cm  in  radius  ejected  from  the  nucleus. 
Comet  Halley  also  was  the  first  radar  bright  comet  observed;  it  had  the  largest  radar  cross 
section  to  date  of  any  comet  detected  by  radar.  "If  our  interpretation  of  the  echoes  is 
correct,"  Don  Campbell  explained,  "Halley  is  the  first  comet  to  give  a  stronger  echo  from 
particles  than  from  the  nucleus  itself."75 

The  Arecibo  attempt  on  Halley  in  1985  was  the  last  successful  radar  detection  of  a 
comet.  In  1990,  John  Harmon  attempted  Comet  Austin  in  cooperation  with  Steve  Ostro, 
who  tried  to  obtain  echoes  with  the  Goldstone  X-band  radar.  Harmon  also  attempted 
Comet  Honda-Mrkos-Pajddusakova  in  1990,  but  again  without  success.76  These  failures 
only  served  to  highlight  the  extreme  difficulty  of  doing  radar  research  on  comets  and,  as 
a  result,  the  lack  of  major  radar  contributions  to  cometary  science. 

A  Vision  of  Things  to  Come 

Asteroids  did  not  make  easy  radar  targets,  either.  Their  small  size  and  distance  from 
Earth  placed  them  at  the  limits  of  planetary  radar  capabilities.  Also,  the  known  popula- 
tion of  asteroids  outside  the  mainbelt  between  Mars  and  Jupiter,  that  is,  the  known 
number  of  asteroids  that  might  approach  Earth  close  enough  for  radar  study,  was  far 
smaller  than  the  quantity  we  know  today.  After  the  detection  of  Icarus  at  Haystack  and 
Goldstone  in  June  1968,  only  six  more  asteroids  came  under  radar  investigation  between 
then  and  July  1980:  five  near-Earth  asteroids  (1566  Icarus,  1685  Toro,  433  Eros,  1580 
Betulia,  and  Phocaea)  and  two  mainbelt  asteroids  (1  Ceres  and  4  Vesta). 


73.  E.  Griin,  ed.,  "Halley  and  Giacobini-Zinner,"  Advances  in  Space  Research  vol.  5,  no.  12  (1985):  1-344; 
J.  W.  Mason,  ed.,  Comet  Halley:  Investigations,  Results,  Interpretations,  2  vols.  (New  York:  Ellis  Horwood,  1990);  R. 
Reinhard  and  B.  Battrick,  eds.,  The  Giotto  Mission:  Its  Scientific  Investigations  (Noordwijk:  ESTEC,  European  Space 
Agency,  1986);  M.  Grewing,  F.  Praderie,  and  R.  Reinhard,  eds.,  Exploration  of  Halley 's  Comet  (New  York:  Springer- 
Verlag,  1986). 

74.  Kamoun,  pp.  239-240;  Campbell,  Harmon,  and  Shapiro,  "Radar  Observations  of  Comet  Halley, "  The 
Astrophysical  Journal  338  (1989):  1094-1105;  Campbell,  Harmon,  and  Shapiro,  Radar  Observations  of  Comet  Halley 
Report  246  (Ithaca:  NAIC,  September  1988),  Pettengill  materials. 

75.  Campbell  9  December  1993;  Campbell,  Harmon,  and  Shapiro,  "Comet  Halley,"  pp.  1094  and  1103; 
NAICQRQ4/1985.8. 

76.  NAIC  QR  Q2/1990,  6. 


222  TO  SEE  THE  UNSEEN 


Interest  in  asteroids  was  growing  among  astronomers  during  that  12-year  period. 
Tom  Gehrels,  University  of  Arizona  at  Tucson,  was  the  most  vocal  advocate  of  asteroid 
research.  During  the  1970s,  he  organized  three  asteroid  conferences  at  Tucson  which 
provided  much  of  the  impetus  for  the  modern  investigation  of  asteroids.  He  also 
initiated  a  program  of  asteroid  detection  called  Spacewatch.  Spacewatch,  a  survey 
telescope  located  on  Kitt  Peak  to  discover  new  asteroids,  started  operating  in  May  1963. 
Tom  Gehrels  also  led  an  effort  to  use  a  modern  CCD  scanning  camera  on  a  specially 
designed  telescope  beginning  in  1979.  In  its  first  two  years,  Spacewatch  discovered  69  new 
asteroids.  The  rapid  discovery  rate  of  asteroids  that  started  in  the  1970s  was  due  largely, 
however,  to  the  Palomar  Planet-Crossing  Asteroid  Survey  (PCAS),  begun  in  1973  by 
Eleanor  Helin  and  Eugene  Shoemaker.  The  Survey  initially  used  a  46-cm  Schmidt  camera 
to  detect  asteroids  on  the  four  to  five  nights  each  month  around  the  new  Moon.  The 
exposed  photographic  plates  were  subjected  to  stereoscopic  examination  the  same  night 
they  were  taken,  in  case  a  new  asteroid  was  recorded  on  the  film.  If  an  object  were 
discovered,  positional  data  was  relayed  by  telephone  to  Brian  Marsden  at  the  Harvard- 
Smithsonian  Astrophysical  Center,  where  he  headed  a  center  for  data  on  minor  planets 
starting  in  1978.  Marsden  then  computed  the  orbit  and  ephemerides  for  further  observa- 
tions. 

As  a  result  of  the  Spacewatch  and  PCAS  programs,  the  asteroid  literature,  as  mea- 
sured by  citations  of  asteroid  papers,  underwent  the  kind  of  swift  growth  that  is  typical  of 
Big  Science.77  Although  radar  astronomers  at  first  simply  attempted  to  detect  asteroids, 
both  Arecibo  and  Goldstone  investigators  initiated  systematic  programs  of  asteroid  detec- 
tion and  research  in  the  mid-seventies.  The  focus  was  on  measuring  radii,  surface  rough- 
ness, and  composition,  and  on  improving  orbits.  In  addition,  Ray  Jurgens  pioneered  the 
modeling  of  asteroid  shapes. 

Dick  Goldstein,  using  the  Goldstone  Mars  Station,  obtained  echoes  from  1685  Toro, 
the  first  asteroid  detected  after  Icarus,  in  1972.  After  he  combined  the  radar  and  optical 
data,  Goldstein  inferred  that  the  asteroid  had  an  irregular  rocky  surface  slightly  smoothed 
by  a  mantle  of  loose  material.78  The  following  asteroid  opportunity,  433  Eros,  arrived  in 
January  1975.  The  experiment  carried  out  on  Eros  at  Goldstone  was,  in  the  words  of  Steve 
Ostro,  'The  most  important  asteroid  experiment  before  1980,"  because  data  was  taken  at 
two  frequencies  (X-band  and  S-band)  and  in  both  senses  of  circular  polarization.  "As  a 
result,"  according  to  Ostro,  "they  achieved  the  best  characterization  of  an  asteroid's  cen- 
timeter-to-decimeter scale  surface  properties  until  the  late  1980s.  By  then,  all  work  was 
dual  polarization.  Jurgens  and  Goldstein  were  well  ahead  of  their  time."79 

The  data  Goldstein  and  Jurgens  collected  indicated  that  the  surface  of  Eros  was 
much  rougher  than  the  Moon  or  any  of  the  terrestrial  planets.  They  described  a  surface 
completely  covered  with  sharp  edges,  pits,  subsurface  holes,  or  embedded  chunks.  They 
also  estimated  the  asteroid  to  have  equatorial  dimensions  of  18.6  and  7.9  km.80  In  order 
to  better  describe  the  shape  of  Eros  and  other  asteroids,  Ray  Jurgens  developed  a  triaxial 
ellipsoid  model.  His  work  represented  an  important  first  step  toward  modeling  asteroids 
with  radar  data.  Optical  observations  often  provide  the  spin  rate  and  pole,  prerequisite 
parameters  for  determining  the  shape  of  an  asteroid  from  radar  data.81 


77.  Clifford  J.  Cunningham,  Introduction  to  Asteroids:  The  Next  Frontier  (Richmond:  Willmann-Bell,  1988), 
pp.  2  and  97-101;  Tom  Gehrels,  "The  Asteroids:  History,  Surveys,  Techniques,  and  Future  Work,"  in  Gehrels  and 
Matthews,  eds.,  Asteroids  (Tucson:  University  of  Arizona  Press,  1979),  pp.  4-5  and  13-14. 

78.  Goldstein,  D.  B.  Holdridge,  and  J.  H.  Lieske,  "Minor  Planets  and  Related  Objects:  12.  Radar 
Observations  of  (1685)  Toro,"  The  Astronomical  Journal  78  (1973):  508-509. 

79.  Ostro  25  May  1994. 

80.  Goldstein  and  Jurgens,  "Radar  Observations  at  3.5  and  12.6  cm  Wavelength  of  Asteroid  433  Eros," 
Icarus  28  (1976):  1-15. 

81.  Jurgens,  "Radar  Backscattering  from  a  Rough  Rotating  Triaxial  Ellipsoid  with  Applications  to  the 
Geodesy  of  Small  Asteroids,"  Icarus  49  (1982):  97-108. 


THE  OUTER  LIMITS 


223 


Figure  35 

In  order  to  model  the  nonspherical  shape  and  numerous  axes  of  rotation  of  asteroids,  Rayjurgens  designed  a  coordinate  frame 
to  describe  asteroids  as  rotating  triaxial  ellipsoids.  This  was  the  first  attempt  to  model  asteroid  shapes  with  radar  data. 
(Courtesy  of  Jet  Propulsion  Laboratory.) 

Continuing  his  pursuit  of  radar  asteroid  research,  Rayjurgens  outlined  an  ambitious 
10-year  program  of  asteroid  opportunities  in  1977.  The  program  laid  out  the  kinds  of 
measurements  that  ground-based  radars  (both  Goldstone  and  Arecibo)  could  make  with 
currently  available  transmitter  power  and  receiver  sensitivity.  Jurgens  estimated  that  the 
number  of  detectable  asteroids  available  for  study  over  the  following  10  years  was  60.  It 
took  a  few  years  longer  to  reach  that  number,  however,  for  a  variety  of  reasons.  Jurgens 
also  pointed  out  that  astronomers  could  use  the  radar  data  in  many  cases  to  calculate  the 
radius,  average  surface  roughness,  rotational  rate,  and  polar  axis  direction,  and  in  some 
cases  the  radar  albedos  and  orbital  parameters,  of  asteroids.82 

In  a  memorandum  to  NASA  Headquarters,  Jurgens  described  the  kinds  of  asteroid 
opportunities  that  would  become  available  upon  the  upgrading  of  the  Goldstone  radar 
and  argued  for  the  scientific  value  of  determining  object  size,  rotation  period,  shape,  and 
surface  properties  from  range  and  Doppler  measurements,  in  the  hopes  of  funding 
asteroid  radar  research  at  JPL.83  Jurgens  had  foreseen  and  mapped  out  the  kind  of  radar 
asteroid  research  program  that  only  a  few  years  later  would  materialize,  but  at  Arecibo. 
Jurgens'  asteroid  research  program  did  not  take  root  at  JPL;  the  Goldstone  radar  was  shut 
down  after  some  unsuccessful  tracks  on  Vesta  on  28  May  1982.84  In  contrast,  radar  aster- 
oid studies  at  Arecibo  were  far  more  energetic.  There,  Brian  Marsden  worked  with  Irwin 
Shapiro,  the  guru  of  the  Planetary  Ephemeris  Program,  to  undertake  a  systematic  study 


82.  Jurgens  and  D.  F.  Bender,  "Radar  Detectability  of  Asteroids:  A  Survey  of  Opportunities  for  1977 
through  1987,"  Icarus  31  (1977):  483-497.  The  asteroid  research  program  grew  out  of  a  larger  work  Jurgens  did 
while  at  JPL,  namely,  Jurgens,  A  Survey  of  Ground-based  Radar  Astronomical  Capability  Employing  64  and  128  Meter 
Diameter  Antenna  Systems  at  S  and  X  Band,  Report  890-44  (Pasadena:  JPL,  March  1977).  See  also  Pettengill  and 
Jurgens,  "Radar  Observations  of  Asteroids,"  in  Gehrels  and  Matthews,  Asteroids,  pp.  206-211. 

83.  Jurgens  to  Geoffrey  A.  Briggs,  12  August  1982,  Jurgens  materials. 

84.  Jurgens,  "Seeing  Comet  IRAS,"  p.  222. 


224  TO  SEE  THE  UNSEEN 


of  asteroid  astrometry  and  composition.85  The  first  asteroid  observations  that  formed  part 
of  that  program  were  of  Eros. 

In  1975,  Don  Campbell  and  Gordon  Pettengill  observed  Eros  with  the  old  UHF  (430- 
MHz;  70-cm)  transmitter.  That  was  the  first  asteroid  detected  by  the  Arecibo  telescope 
radar.  Campbell  and  Pettengill  measured  the  radar  cross  section  of  the  asteroid  and  esti- 
mated its  radius  to  be  about  16  km.  They  also  found  the  surface  of  Eros  to  be  rough  com- 
pared to  the  surfaces  of  the  terrestrial  planets  and  the  Moon.  When  Pettengill  and 
Campbell  attempted  to  determine  the  composition  of  the  surface,  they  could  only  con- 
clude that  it  could  not  be  a  highly  conductive  metal.86 

After  unsuccessful  attempts  at  asteroids  Ceres  and  Metis,  Pettengill  and  Marsden 
observed  1580  Betulia  in  1976,  the  first  asteroid  target  of  the  new  S-band  radar.  Steve 
Ostro,  then  a  graduate  student  at  MIT,  did  the  analysis.  He  measured  the  asteroid's  aver- 
age radar  cross  section  and  set  a  lower  limit  to  the  asteroid's  radius  of  2.9  ±  0.2  km.87 

Pettengill  and  Ostro  next  turned  their  attention  to  the  mainbelt  asteroid  Ceres. 
Already,  in  December  1975,  Pettengill  and  Marsden,  in  collaboration  with  Goldstein  (JPL) 
and  Tom  Gehrels  and  Benjamin  Zellner  (University  of  Arizona)  had  failed  to  obtain 
echoes  from  both  Ceres  and  Metis,  another  mainbelt  asteroid.  The  lack  of  an  echo  from 
Metis  was  not  surprising,  but  Ceres  should  have  been  easy  to  detect;  they  interpreted  the 
absence  of  an  echo  as  indicating  a  smaller  cross  section  than  they  had  expected.88 

Ostro,  Pettengill,  and  Campbell  finally  detected  Ceres  with  the  Arecibo  S-band  radar 
in  March  and  April  1977.  This  was  the  first  mainbelt  asteroid  detected  by  radar.  The 
greater  sensitivity  of  the  S-band  instrument  made  it  possible  for  the  radar  to  reach  into  the 
mainbelt  of  asteroids  and  detect  such  a  small  body.  The  opportunity  of  March  1977  was 
slightly  more  favorable  than  that  of  1975,  thanks  to  the  installation  of  a  more  sensitive  line 
feed  in  1976.  Ceres  was  found  to  have  a  low  radar  cross  section,  less  than  that  for  the 
Moon,  the  terrestrial  planets,  and  even  Eros.  On  the  other  hand,  the  asteroid  appeared  to 
have  a  very  rough  surface  at  some  scale  comparable  to,  or  larger  than,  the  12.6-cm  wave- 
length of  the  radar,  that  is,  rougher  than  the  Moon  and  terrestrial  planets,  but  smoother 
than  the  Galilean  satellites  of  Jupiter.89 

Noisy  data  taken  on  mainbelt  asteroid  Vesta  during  three,nights  of  observations  in 
November  1979  returned  only  a  weak  detection.90  Each  asteroid  detection  seemed  to 
bring  a  new  revelation;  no  pattern  emerged.  Unlike  the  terrestrial  planets,  asteroids  pre- 
sented not  a  few  bodies  to  study  but  an  entire  population,  a  population,  moreover,  that 
the  growing  discovery  rate  kept  increasing.  Although  the  systems  of  Jupiter  and  Saturn 
defined  the  outer  limits  of  planetary  radar  astronomy  after  1975,  the  asteroids  defined  its 
future.  They  were  on  their  way  to  deposing  Venus  from  its  position  as  the  favored  target 
of  radar  astronomers. 


85.  NAIC  QR  Q2/ 1976,  6-7. 

86.  Campbell,  Pettengill,  and  Shapiro,  "70-cm  Radar  Observations  of  433  Eros,"  Icarus  28  (1976):  17-20; 
NAICQRQ1/1975,  4. 

87.  Pettengill,  Ostro,  Shapiro,  Marsden,  and  Campbell,  "Radar  Observations  of  Asteroid  1580  Betulia," 
Icarus  40  (1979):  350-354. 

88.  NAIC  QRQ4/ 1975,  5. 

89.  Ostro,  Pettengill,  Shapiro,  Campbell,  and  R.  Green,  "Radar  Observations  of  Asteroid  1  Ceres,"  Icarus 
40  (1979):  355-358;  NAIC  QR  Ql/1977,  6-7. 

90.  Ostro,  Campbell,  Pettengill,  and  Shapiro,  "Radar  Detection  of  Vesta,"  Icarus  43  (1980):  169-171; 
Ostro  25/5/94;  NAIC  QR  Q4/1979,  7. 


Chapter  Nine 

One  Step  Beyond 


Just  as  the  Arecibo  S-band  and  the  Goldstone  X-band  upgrades  had  propelled  radar 
astronomy  into  new  directions,  in  1986  a  second  upgrade  planned  for  the  Arecibo  radar 
and  the  restoration  and  upgrading  of  the  Goldstone  radar  stimulated  new  shifts  in  the 
planetary  radar  paradigm.  Instruments  and  hardware  continued  to  drive  the  field.  Fresh 
techniques,  either  developed  by  radar  astronomers  or  borrowed  from  other  fields,  name- 
ly ionospheric  and  radio  astronomy  research,  allowed  radar  astronomers  to  solve  new 
problems  on  the  terrestrial  planets.  Also,  the  bizarre  radar  signatures  of  the  icy  Galilean 
satellites  appeared  once  again,  though  closer  to  home  on  the  terrestrial  planets,  and  sug- 
gested new  problems  to  solve. 

The  Goldstone  Solar  System  Radar 

Planetary  radar  astronomy  survived  at  JPL  in  a  tenuous  state  as  a  testbed  for  DSN 
technology  and  as  a  mission-oriented  activity.  That  state  depended  largely  on  support 
from  specific  upper-management  individuals,  Eb  Rechtin  and  Walt  Victor.  After  Rechtin 
left  JPL  and  Victor  transferred  out  of  the  Deep  Space  Network  to  the  JPL  Office  of 
Planning  and  Review  in  December  1978,  radar  astronomy  became  vulnerable  to  extinc- 
tion. The  DSN  Advisory  Group,  headed  by  Rechtin,  had  judged  that  radar  astronomy  was 
no  longer  the  testbed  of  DSN  technology. 

The  Goldstone  radar  was  in  desperate  need  of  repair,  and  the  old  equipment  had 
become  very  hard  to  maintain;  few  people  knew  how  to  work  with  it.  By  1980,  much  of  the 
equipment  was  old  and  not  functioning  properly.  During  experiments,  for  instance,  entire 
runs  of  data  would  be  flawed  or  lost  as  a  result  of  computer  malfunctions.  "You  simply  had 
to  bite  the  bullet  and  rebuild  the  whole  damned  thing,  particularly  the  data  acquisition 
systems,"  Ray  Jurgens  explained.1  However,  nobody  wanted  to  pay  the  cost  of  the  needed 
repairs  and  upgrades. 

Reviving  the  Goldstone  radar  so  that  planetary  radar  astronomy  could  once  again 
prosper  at  JPL  required  that  the  activity  have  a  new  rationale.  The  initial  arguments  for 
funding  needed  new  equipment  focused  on  the  value  of  radar  to  NASA  flight  missions 
and  to  planetary  geology.  In  1979,  E.  Myles  Standish,  Jr.,  who  was  in  charge  of  the  JPL 
planetary  ephemeris  program,  wrote  a  memo  to  Richard  R.  Green,  who  had  recently  been 
promoted  from  the  radar  group  to  Advanced  Systems,  to  explain  that  if  no  radar  experi- 
ments were  conducted,  then  the  accuracy  of  the  ephemerides  for  the  terrestrial  planets 
would  suffer,  and  JPL  would  not  be  able  to  meet  its  ephemeris  commitments  to  either  the 
Galileo  or  Magellan  missions.2 

Obtaining  mission  approval  had  been  a  requisite  for  acquiring  antenna  time  for 
radar  experiments.  As  George  Downs  explained,  "Dick  Goldstein  always  wanted  to 


1.  Jurgens  23  May  1994.  In  addition  to  the  computer  and  other  hardware  problems,  small  cracks 
appeared  in  the  pedestal  of  the  Goldstone  Mars  Station.  The  repair  involved  raising  the  3,000-ton  structure  and 
replacing  a  large  portion  of  the  pedestal  concrete.  The  antenna  did  not  return  to  service  until  June  1984,  after 
being  down  a  year  for  repairs.  JPL  Annual  Report,  1983,  p.  26,  and  ibid.,  1984,  p.  26,  JPLA. 

2.  Memorandum,  Standish  to  R.  Green,  10  May  1979,  Jurgens  materials. 

225 


226  TO  SEE  THE  UNSEEN 


connect  us  with  a  project.  I  believe  he  felt  that  if  we  tried  to  get  constituency  from  geolo- 
gists alone,  we  wouldn't  make  it.  Well,  he  was  right."3  In  1979,  George  Downs  asked  USGS 
geologist  Henry  J.  Moore  to  write  a  letter  in  support  of  the  Goldstone  radar;  Moore  wrote 
to  Arden  L.  Albee,  Caltech  professor  of  geology  and  the  newJPL  Chief  Scientist. 

Albee  was  sympathetic  and  met  with  members  of  the  JPL  radar  group,  Ray  Jurgens, 
George  Downs,  Stan  Butman,  and  Rick  Green,  on  24  January  1980.  As  a  result  of  the  meet- 
ing, Albee  wrote  to  the  NASA  Office  of  Space  Science  recommending  a  line  item  for  radar 
astronomy  in  the  fiscal  1982  budget.  Thomas  Mutch,  associate  administrator,  NASA  Office 
of  Space  Science,  replied  that  he  could  not  raise  the  annual  allocation;  the  funding  level 
would  have  to  remain  level.4 

Some  support  for  resurrection  of  the  Goldstone  radar  could  be  counted  on  coming 
from  the  Planetary  Radar  Working  Group,  which  consisted  largely  of  geologists  in  the 
USGS  and  academia  plus  smaller  numbers  of  individuals  representing  SAR  remote  sens- 
ing and  NASA  Headquarters,  as  well  as  radar  astronomers  Pettengill,  Campbell, 
Goldstein,  and  Len  Tyler.  The  Planetary  Radar  Working  Group  met  in  conjunction  with 
the  AAS  Division  for  Planetary  Sciences  and  the  Lunar  and  Planetary  Science  Conference 
and  discussed  priorities  in  radar  astronomy  at  Goldstone  and  Arecibo.  Of  course,  the  fate 
of  the  VOIR  mission,  not  the  Goldstone  radar,  was  the  focal  point  of  discussions.5 

With  support  from  the  Planetary  Radar  Working  Group,  Ray  Jurgens  and  George 
Downs  wrote  a  proposal  requesting  about  $1.8  million  to  purchase  a  VAX  computer  to 
reduce  radar  data.  They  submitted  it  to  the  NASA  planetary  geology  office  because  they 
thought  planetary  geologists  would  be  the  prime  users  of  the  data.  In  retrospect,  George 
Downs  judged  that  reviewers  saw  the  proposal  as  a  threat  to  their  own  funding  and  did  not 
give  it  good  reviews,  while  those  who  saw  the  project's  usefulness  gave  it  good  reviews. 

Although  Jurgens  and  Downs  did  not  get  the  amount  requested,  the  NASA  Office  of 
Space  Science  and  Implementation  did  grant  them  enough  to  buy  a  new  VAX-700  and 
about  $150,000  a  year  to  analyze  radar  data.  Radar  astronomy  also  achieved  a  modest  level 
of  recognition  in  1982.  The  original  1971  NASA  Management  Instruction  governing 
ground  radio  science,  now  considered  obsolete,  replaced  the  term  "radio  science"  with 
"Radio  and  Radar  Astronomy."  Such  was  the  state  of  radar  astronomy  when  Downs  left  in 
1982.6 

In  1983,  radar  astronomy  acquired  a  new  advocate,  Nicholas  A.  Renzetti.  Originally 
a  DSN  manager  responsible  for  the  interface  between  the  DSN  and  its  flight  customers, 
starting  in  1975  with  the  Viking  and  Voyager  launches,  Renzetti  gave  less  attention  to 
flight  projects  and  more  attention  to  applications  of  radio  technology  to  non-flight  pro- 
jects, such  as  geodynamics,  the  Search  for  Extraterrestrial  Intelligence,  radio  astronomy, 
and  starting  in  1983,  radar  astronomy.  Renzetti  took  on  the  task  of  convincing  the  Office 
of  Space  Science  and  other  NASA  Headquarters  departments  that  it  was  in  NASA's  inter- 
est to  support  the  Goldstone  radar  as  a  scientific  instrument.7 

The  new  rationale  for  funding  the  Goldstone  radar,  as  defined  by  Renzetti,  would  be 
its  use  as  a  scientific  instrument.  In  his  campaign  to  garner  support  for  the  Goldstone 
radar,  Renzetti  was  assisted  by  Steve  Ostro,  who  took  a  position  at  JPL  in  late  1984,  after 
leaving  Cornell.  They  negotiated  a  new  task  in  December  1987,  in  which  the  Goldstone 
radar  would  be  treated  as  if  it  were  a  facility,  not  as  a  science  task,  with  an  annual  budget 


3.  Downs  4  October  1994. 

4.  Henry  J.  Moore  to  Arden  L.  Albee,  2  July  1979,  Jurgens  materials;  Memorandum,  William  H.  Bayley 
to  Murray,  4  February  1980,  91/7/89-13,  JPLA;  Various  documents  in  "NASA  Correspondence,  1980-1981," 
JPLPLC. 

5.  Jurgens    23    May    1994;    Planetary   Radar   Working   Group    mailing    list,  Jurgens    materials; 
Memorandum,  Carl  W.Johnson  to  Murray,  27  October  1980,  99/8/89-13, JPLA. 

6.  Jurgens  23  May  1994;  Downs  4  October  1994;  C.  H.  Terhune,  Jr.,  to  B.  I.  Edelson  and  R.  E.  Smylie, 
20  September  1982,  "Chron  1982,  #2,"  JPLPLC. 

7.  Renzetti  16  April  1992;  Renzetti  17  April  1992. 


ONE  STEP  BEYOND  227 


of  about  $200,000  for  hardware  improvements.  The  NASA  task  underwrote  the  interface 
between  the  DSN  and  the  radar  astronomers.  The  objective  of  the  new  task,  called  the 
Goldstone  Solar  System  Radar  (GSSR),  was  to  support  planning,  experiment  design,  and 
coordination  of  data  acquisition  and  engineering  activities  for  all  Goldstone  planetary 
radar  astronomy.  As  Steve  Ostro  explained,  'This  has  been  the  financial  backbone  for  the 
Goldstone  radar,  and  it  is  separate  from  the  DSN."8 

At  the  same  time,  Renzetti  created  a  part-time  position,  the  Friend  of  the  Radar.  The 
holder  of  that  position  was  to  carry  out  a  number  of  duties,  including  NASA  flight  project 
science  and  liaisons  with  Arecibo  Observatory,  but  most  importantly  interfacing  with  the 
scientific  community.  Tommy  Thompson  performed  those  duties  until  he  became 
Magellan  Science  Manager  in  1988,  when  Martin  A.  Slade  replaced  him.  Slade  had  been 
a  graduate  student  of  Irwin  Shapiro  at  MIT  and  had  had  some  exposure  to  radar  astron- 
omy during  summer  jobs  at  Haystack.  His  main  previous  research  interests,  however,  lay 
elsewhere.9 

The  creation  of  the  GSSR  task  and  the  Friend  of  the  Radar  were  only  first  steps  in 
addressing  the  core  issue  of  funding  the  Goldstone  radar  on  the  basis  of  its  use  as  a  sci- 
entific instrument.  Renzetti  took  tentative,  unsuccessful  steps  to  open  up  the  Goldstone 
radar  to  outside  researchers  in  order  to  operate  it  as  a  national  research  facility.  He 
approached  Von  Eshleman  and  two  others  from  outside  JPL  to  propose  radar  experiments 
at  Goldstone.  Renzetti  also  proposed  to  Tor  Hagfors,  NAIC  director,  that  a  single  peer 
review  panel  assess  radar  experiment  proposals  for  both  the  GSSR  (as  the  Goldstone  Mars 
Station  or  DSS-14  now  came  to  be  called)  and  Arecibo.  Moreover,  hoping  to  acquire  a 
facility  budget  for  GSSR  on  a  level  with  that  of  Arecibo,  Renzetti  proposed  to  Hagfors  that 
Arecibo  and  GSSR  present  a  common  front  to  NASA,  rather  than  appear  as  competing 
facilities.10 

But  it  did  not  make  sense  to  pursue  the  common  budget,  Renzetti  reasoned,  as  long 
as  the  GSSR  was  not  a  national  facility.  The  annual  amount  requested  from  NASA  to  make 
the  GSSR  a  "first-class  scientific  instrument,"  $500,000,  was  not  well  received  at  NASA 
Headquarters.  In  comparison,  the  NASA  budget  for  the  Arecibo  radar  was  only  $362,000 
in  1986.11  Nonetheless,  Renzetti,  who  felt  there  was  a  built-in  bias  in  favor  of  Arecibo  at 
high-level  NASA  meetings,  submitted  a  formal  proposal  to  make  the  GSSR  a  national  facil- 
ity, but  it  never  got  off  the  ground.12 

A  chief  critic  of  the  proposal  to  turn  the  Goldstone  radar  into  a  national  research 
center  was  Dewey  Muhleman  of  Caltech.  He  called  parts  of  the  proposal  "ludicrous"  and 
declared  that  it  would  do  "nothing  for  Science,  the  Nation,  NASA  nor,  in  the  long  run, 
JPL."  Moreover,  he  pointed  out,  the  heavy  scheduling  of  the  antenna  for  spacecraft  work 
militated  against  the  plan.  "I  strongly  favor,"  he  wrote,  "the  idea  of  getting  Radar 
Astronomy  at  JPL  out  of  the  closet  of  component  development  and  into  the  light  of  pure 
science."13 

Gradually,  that  was  starting  to  take  place.  During  a  JPL  administrative  reorganization 
in  the  fall  of  1987,  the  Office  of  Space  Science  and  Instruments  (OSSI)  was  created  with 
Charles  Elachi  as  its  head.  Elachi  was  a  seasoned  radar  engineer  with  decades  of  SAR 
experience.  After  he  obtained  a  modest  level  of  funding,  $150,000,  from  NASA 
Headquarters,  Elachi  named  Steve  Ostro  manager  of  Planetary  Radar  Science  and  autho- 
rized him  to  allocate  the  funding.14 


8.  Ostro  18  May  1994;  GSSR  Min.  6  December  1984. 

9.  Thompson  29  November  1994;  Slade  24  May  1994;  GSSR  Min.  6  December  1984  and  31  March 
1988. 

10.  GSSR  Min.  29  December  1986. 

11.  GSSR  Min.  22  January  1987  and  26  February  1987;  NAIC  QR  Ql/1986,  19. 

12.  GSSR  Min.  26  February  1987. 

13.  Memorandum,  Muhleman  to  Edward  C.  Posner,  28  October  1986,  Ostro  materials. 

14.  GSSR  Min.  3  December  1987,  14  January  1988,  18  February  1988,  and  28  April  1988. 


228  TO  SEE  THE  UNSEEN 


"At  that  point,"  Ostro  explained,  "I  had  a  little  bit  of  authority.  I  had  the  program 
office  backing  me.  I  acted  as  somewhat  of  a  filter  on  proposals  and  papers,  when  I  could, 
and  I  acted  as  the  voice  of  science  for  radar."  Ostro  agreed  with  Muhleman's  perception 
that  JPL  placed  too  much  emphasis  on  hardware  and  not  enough  on  doing  science.  The 
science  community  in  general,  he  pointed  out,  viewed  the  GSSR  as  state-of-the-art  elec- 
tronics, but  saw  Arecibo  as  producing  state-of-the-art  planetary  radar  data.  The  objective, 
Ostro  declared  in  1988,  "is,  a  year  from  now,  to  have  a  sparkling  list  of  GSSR  radar  articles 
that  have  appeared  in  high-quality  journals."15  Despite  such  sterling  intentions  on  the  part 
of  Ostro  and  Renzetti,  keeping  JPL,  DSN,  and  NASA  management  aware  of  the  Goldstone 
radar's  scientific  achievements  and  potential  has  been  a  Sisyphean  task.  In  contrast,  the 
value  of  radar  astronomy  was  established  from  the  outset  at  the  Arecibo  Observatory. 

Here  was  an  important  difference  between  the  two  facilities  that  had  a  profound 
impact  on  the  development  of  radar  astronomy  at  each  site.  Even  more  important,  how- 
ever, was  the  fact  that  Arecibo  had  acknowledged  and  formalized  the  existence  of  radar 
astronomy  from  the  start;  whereas  JPL  purposely  had  denied  radar  astronomy  any  formal 
existence.  The  difference  has  had  long-term  implications  that  has  favored  radar  astrono- 
my science  at  Arecibo,  while  holding  it  back  at  JPL. 

New  hardware  and  fresh  leadership  enabled  radar  astronomers  to  make  new  discov- 
eries about  Mars,  Mercury,  and  the  asteroids  with  the  Goldstone  radar.  The  major 
hardware  upgrade  did  not  arise  from  a  concerted  campaign  on  the  part  of  Renzetti  and 
Ostro  to  improve  the  state  of  radar  astronomy  at  JPL,  but  rather,  in  a  fashion  typical  of  the 
history  of  planetary  radar  astronomy,  came  from  outside  radar  astronomy,  namely,  the 
Voyager  mission  to  the  outer  planets. 

The  Voyager  upgrade  of  the  main  GSSR  antenna,  known  within  the  Deep  Space 
Network  as  DSS-14,  involved  enlarging  the  dish  diameter  from  64  (210  ft)  to  70  meters 
(230  ft),  increasing  the  surface  accuracy,  and  improving  the  receiving  system.  These 
measures  increased  the  sensitivity  of  the  DSS-14  significantly.  Tracking  and  acquiring  data 
from  the  Voyager  spacecraft,  as  they  encountered  Uranus  and  Neptune,  stretched  the 
capacity  of  the  Deep  Space  Network.  During  the  Neptune  encounter,  the  Voyager  X-band 
radio  signal  would  be  less  than  one-tenth  as  strong  as  during  the  Jupiter  encounter  in 
1979  and  less  than  one-half  as  strong  as  during  the  Uranus  encounter  in  1986. 

A  study  to  enlarge  all  the  DSN  64-meter  antennas  to  70  meters  already  had  been 
undertaken  as  early  as  1973  in  preparation  for  Voyager  when  it  was  still  called  Mariner 
Jupiter/Saturn.  After  completion  of  design  work  in  1984,  the  upgrade  of  the  DSS-14 
began  in  October  1987  and  concluded  in  May  1988.16  When  Steve  Ostro  arrived  at  JPL  in 
1984,  the  DSS-14  lacked  the  threshold  of  sensitivity  to  do  meaningful  asteroid  research. 
Upon  completion  of  the  initial  upgrade  phase,  however,  Ostro  made  his  first  successful 
asteroid  observations  with  the  DSS-14  in  May  1986,  when  he  detected  echoes  from  1986 
JK,  an  asteroid  only  just  then  discovered  by  Eugene  and  Carolyn  Shoemaker. 

The  Voyager  upgrade  had  a  profound  impact  on  the  practice  of  radar  astronomy  at 
JPL;  it  provided  the  GSSR  the  sensitivity  needed  to  carry  out  research  on  a  whole  new  set 
of  targets  (and  to  begin  solving  new  sets  of  problems).  Not  only  did  the  GSSR  gain  the 
ability  to  undertake  significant  asteroid  research,  but  when  linked  to  the  Very  Large  Array 
in  New  Mexico,  as  we  shall  see  later,  it  became  a  new  radar  research  tool. 

Despite  these  major  upgrades,  the  GSSR  had  serious  problems  as  a  scientific  instru- 
ment. The  site  lacked  dormitory  and  cooking  facilities  for  visiting  or  even  JPL  scientists, 
and  the  drive  to  Barstow  50  miles  away  on  winding  roads  after  a  night  of  observations  was 
dangerous.  These  deficiencies  and  dangers  persist  today.  Furthermore,  the  radar  itself  was 
far  from  user-friendly.  "It  was  just  impossible  to  work,"  Ostro  explained.  "For  example,  the 


15.  Ostro  18  May  1994;  GSSR  Min.  14  January  1988  and  18  February  1988. 

16.  JPL  Annual  Report,  1973-1974,  p.  15;  ibid.,  1984,  p.  13;  ibid.,  1987,  p.  41;  and  ibid.,  1988,  p.  28, 
JPLA. 


ONE  STEP  BEYOND  229 


VAX  that  is  used  for  data  acquisition  at  Goldstone  is  not  good  for  radar  astronomy  for 
various  technical  reasons.  It  has  been  improved  a  lot  since  the  mid-1980s,  but  even  now  it 
is  difficult,  for  example,  to  stamp  your  data  with  a  high-precision  UTC  [from  the  French 
for  Coordinated  Universal  Time]  time  tag.  For  this  kind  of  work,  the  first  thing  you  need 
on  your  data  is  a  UTC  time  tag."17 

The  Arecibo  Observatory  stood  in  sharp  contrast  to  the  Goldstone  radar.  It  had 
proper  quarters  for  visiting  scientists,  and  the  radar  was  far  more  user-friendly.  Moreover, 
in  1986,  the  Arecibo  Observatory  proposed  a  major  upgrade  of  the  radar  that  would 
benefit  both  ionospheric  and  radio  astronomy  research  and  planetary  radar  astronomy. 
The  Arecibo  upgrade  stirred  Renzetti  to  seek  funding  for  a  Goldstone  radar  upgrade. 

Renzetti  lobbied  the  DSN  and  NASA  hierarchy  for  funding  for  a  Goldstone  one- 
megawatt  transmitter,  which  JPL  engineers  initially  estimated  would  cost  $12  million.  A 
good  argument  for  DSN  use  of  the  radar  would  not  fly;  the  rationale  had  to  be  its  use  for 
scientific  research,  Renzetti  realized.  The  radar  upgrade,  to  be  completed  in  fiscal  year 
1993  and  costing  $10  million  over  two  years,  appeared  in  the  DSN  budget  for  fiscal  1989. 
JPL  viewed  the  price  tag  as  "pared  to  the  bone."  In  the  end,  Congress  approved  the  expen- 
diture not  as  a  specific  radar  upgrade  but  as  an  ambiguous  improvement  of  the  DSN.  This 
ambiguity  freed  DSN  management  to  use  the  radar  transmitter  money  to  purchase  low- 
noise  supercooled  masers  to  improve  antenna  sensitivity  for  Galileo's  encounter  with  Io.18 

It  was  not  clear,  moreover,  that  radar  science  at  JPL  needed  the  one-megawatt  trans- 
mitter. The  estimated  cost  of  the  transmitter  now  stood  at  $16  million.  Steve  Ostro 
believed  that  if  the  cost  were  reduced  below  $8  million,  the  improved  science  capacity 
would  justify  the  expense.  The  high  cost  reflected  JPL  administrative  and  DSN  operational 
support  requirements  that  added  several  million  dollars  to  the  cost.19 

Ostro  favored  upgrading  the  GSSR  antenna's  subreflector  to  improve  its  ability  to 
make  asteroid  observations.  The  long  time  needed  to  rotate  the  subreflector,  which  was 
never  designed  to  act  as  a  transmit/receive  switch,  compromised  short  round-trip-time 
asteroid  observations.  'The  most  powerful  scientific  rationale  for  the  longterm  support  of 
GSSR,"  Ostro  argued,  was  work  on  near-Earth  asteroids.  The  estimated  price  tag  for  the 
transmit/receive  upgrade,  which  involved  turning  the  transmit-only  horn  into  a  horn 
capable  of  switching  quickly  back  and  forth  between  transmit  and  receive,  was  $485,000.20 

Instead  of  going  directly  through  the  DSN  hierarchy  for  a  radar  upgrade,  Renzetti 
changed  his  strategy.  The  one-megawatt  transmitter  and  two  other  radar  improvements 
(construction  of  a  transmit/receive  horn  and  modernization  of  the  data  acquisition 
system)  were  submitted  to  a  panel  of  outside  scientists  for  review.  Gordon  Pettengill 
chaired  the  Goldstone  Planetary  Radar  Science  Review  Committee,  as  the  panel  was 
called.  It  included  planetary  astronomers  and  geologists,  as  well  as  Don  Campbell  and  Tor 
Hagfors  from  the  Arecibo  Observatory.21 


17.  Ostro  18  May  1994. 

18.  GSSR  Min.  22  January  1987,  18  June  1987,  23  July  1987,  24  September  1987,  18  February  1988, 
31  March  1988,  and  26  April  1990;  Renzetti,  Thompson,  and  Slade,  "Relative  Planetary  Radar  Sensitivities: 
Arecibo  and  Goldstone,"  TDA  Progress  Report  42-94  (Pasadena:  JPL,  April-June  1988),  pp.  287-293;  Arthur  J. 
Freiley,  Bruce  L.  Conroy,  Daniel  J.  Hoppe,  and  Alaudin  M.  Bhanji,  "Design  Concepts  of  a  1-MW  CW  X-Band 
Transmit/Receive  System  for  Planetary  Radar,"  IEEE  Transactions  on  Microwave  Theory  and  Techniqiies  40  (1992): 
1047-1055. 

19.  GSSR  Min.  6  February  1992. 

20.  Memorandum,  Ostro  to  Elachi,  29  August  1990;  Memorandum,  David  Hills  to  Dick  Mathison,  1 
October  1990;  Memorandum,  Ostro  to  Larry  N.  Dumas,  15  October  1990,  Ostro  materials. 

21.  Pettengill  to  Elachi,  22  August  1991,  and  attachments,  Ostro  materials.  The  members  of  the 
Goldstone  Planetary  Radar  Science  Review  Committee  were  Gordon  H.  Pettengill,  MIT;  Michael  J.  S.  Belton,  Kitt 
Peak  National  Observatory;  Donald  B.  Campbell,  NAIC;  Clark  R.  Chapman,  Planetary  Science  Institute;  Tor 
Hagfors,  NAIC;  Bruce  W.  Hapke,  University  of  Pittsburgh;  Randolph  L.  Kirk,  USGS;  David  Morrison,  NASA 
Ames  Research  Center;  and  F.  Peter  Schloerb,  University  of  Massachusetts. 


230  TO  SEE  THE  UNSEEN 


Although  invited  to  join  the  Committee,  Muhleman  declined.  He  "took  the  attitude, 
well,  this  is  one  more  panel,  it  can't  be  that  important.  How  about  if  I  don't  come?  Let  me 
know  how  it  comes  out.  That  was  a  terrible  mistake.  It  really  was.. ..The  JPL  viewpoint  was 
not  represented."22  More  importantly  for  Muhleman,  his  viewpoint  was  not  represented, 
and  he  paid  the  price.  The  Committee  met  on  8  August  1991  and  presented  its  conclu- 
sions later  that  month.  The  Committee  applauded  "the  efforts  currently  underway  by  JPL 
management  to  broaden  the  usage  of  the  Goldstone  facilities  (including  observations 
jointly  with  the  VLA)  to  include  members  of  the  larger  North  American  and  global  plan- 
etary communities." 

Of  the  three  improvements,  the  committee  gave  the  highest  priority  to  the  single- 
horn,  fast-transmit/receive-switchover  system.  That  improvement  would  serve  asteroid 
work  only.  "At  a  lower,  but  still  high,  priority,"  the  committee  endorsed  the  modernization 
of  the  data  acquisition  system  and  recommended  that  the  output  protocols  and  formats 
of  the  new  system  be  coordinated  with  those  of  the  Arecibo  planetary  radar.  Each  of  these 
two  improvements  had  a  modest  cost  of  about  $500,000  spread  over  one  to  two  years. 

The  one-megawatt  transmitter,  the  committee  judged,  "seems  less  attractive  as  an 
upgrading  option  than  the  first  two  presented."  The  cost  was  too  high  for  the  amount  of 
sensitivity  gained.  The  value  of  the  transmitter  upgrade,  the  committee  decided,  lay  in 
observing  Titan,  "but  we  do  not  find  the  scientific  argument  compelling  for  what  appears 
to  be  a  fairly  narrowly  focused  study  of  a  single  object.  We  note  also  that  the  improved 
transmitter  is  unlikely  to  be  available  in  time  to  provide  data  that  materially  assist  in  the 
design  of  the  Cassini  Mission."23 

Titan,  however,  was  of  the  highest  research  interest  to  Dewey  Muhleman.  "In  my 
absence,"  he  complained,  "this  panel  frankly  wrote  a  silly  report.  It  just  really  made  me 
sick  to  read  it.  It  said  that  the  only  advantage  of  going  to  a  megawatt  on  the  Goldstone 
antenna  was  to  be  able  to  do  Titan  better  with  the  VLA.  Nothing  else  was  really  important. 
That  is  ridiculous.  For  everything  we  do,  our  integration  time  would  be  cut  down  by  a  fac- 
tor of  four  by  doubling  our  power  to  a  megawatt.  We  would  be  able  to  do  much  more  on 
each  one  of  these  objects  and  quite  frankly  continue  to  rival  Arecibo  after  the  upgrade."24 

The  Arecibo  Upgrade 

The  struggle  at  JPL  to  gain  recognition  for  the  GSSR  as  a  scientific  instrument  stood 
in  stark  contrast  to  the  effort  to  upgrade  the  Arecibo  telescope.  Both  NASA  and  the  NSF 
already  recognized  Arecibo  as  a  national  research  center,  and  the  rationale  for  any 
upgrade  would  be  on  the  basis  of  scientific  need.  Furthermore,  the  Arecibo  upgrade  stood 
to  benefit  all  research  at  the  facility,  radio  and  radar  astronomy  and  ionospheric  research, 
not  just  planetary  radar  astronomy.  Other  factors  eased  the  process  of  garnering  support 
for  the  Arecibo  upgrade,  including  the  method  of  funding  what  was,  in  relative  terms,  a 
low-cost  project. 

The  Arecibo  upgrade  was  a  package  of  five  interrelated  improvements:  1)  installa- 
tion of  a  ground  screen  to  virtually  eliminate  noise  from  the  surrounding  earth;  2) 
adjustment  of  the  reflector  surface  to  enhance  antenna  gain;  3)  correction  of  the 
pointing  system;  4)  replacement  of  the  accumulation  of  radio  astronomy  line  feeds  with  a 
single  reflector  feed  possessing  large  bandwidth,  low  loss,  high  gain,  and  continuous 
frequency  coverage  from  300  MHz  (1  meter)  to  8  GHz  (3.75  cm);  and  5)  doubling  the 
S-band  transmitter  power  to  one  megawatt.  The  total  effect  of  these  changes  was  to 


22.  Muhleman  27  May  1994. 

23.  Pettengill  to  Elachi,  22  August  1991,  and  attachments,  Ostro  materials. 

24.  Muhleman  27  May  1994. 


ONE  STEP  BEYOND  231 


increase  radar  sensitivity  by  a  factor  of  10  to  50  (about  20  times  on  average),  to  double  its 
range  or  to  detect  objects  10  times  smaller  than  previously  possible.25 

The  principal  objective  of  the  upgrade,  however,  was  to  solve  a  problem  that  had 
plagued  the  telescope  since  its  creation — the  problem  of  spherical  aberration.  Unlike 
parabolic  dishes,  the  Arecibo  spherical  antenna  did  not  focus  waves  in  a  single  point.  The 
antenna  feed  system  designed  by  the  Air  Force  did  not  work  efficiently,  and  though  later 
feeds  improved  the  telescope's  performance,  they  did  not  perform  up  to  the  level  of  a 
Gregorian  reflector,  the  solution  recognized  as  early  as  the  1960s.  Named  for  the 
astronomer  John  Gregory,  a  Gregorian  reflector  is  concave  and  placed  above  the  prime 
focus  of  a  telescope.  In  a  Cassegrain  system,  the  type  used,  for  example,  on  the  Goldstone 
DSS-14,  the  reflector  is  convex  mounted  below  the  prime  focus.26 

Designing  the  Gregorian  optics  was  a  daunting  task.  A  Cornell  graduate  student  had 
considered  the  use  of  Gregorian  optics,  an  option  also  studied  by  the  AFCRL's  Antenna 
Laboratory.27  Frank  Drake,  director  of  the  NAIC  from  1971  to  1981,  nurtured  the 
Gregorian  reflector  idea  and  attempted  unsuccessfully  to  gain  financial  support  to  gather 
together  the  necessary  antenna  expertise  to  submit  a  formal  proposal  to  the  NSF.28 

Design  of  the  Gregorian  reflector  did  not  begin  until  1984,  after  Tor  Hagfors  became 
director  of  the  NAIC  in  late  1982.  After  serving  earlier  as  director  of  the  Arecibo 
Observatory  following  the  departure  of  Gordon  Pettengill,  Hagfors  spent  a  number  of 
years  in  Scandinavia  building  the  EISCAT  facility,  before  returning  to  Cornell  to  head  the 
NAIC.^ 

EISCAT  (European  Incoherent  Scatter  Association)  is  a  European  consortium 
headquartered  at  Kiruna,  Sweden.  Inaugurated  by  the  King  of  Sweden  in  August  1981,  the 
EISCAT  facility  is  a  high-power  radar  installed  at  sites  in  Norway  and  Finland  for  the  study 
of  the  Earth's  ionosphere,  upper  atmosphere,  and  magnetosphere  at  high  latitudes. 
Germany,  France,  and  the  United  Kingdom  bore  the  greatest  share  of  its  construction 
costs  (25  percent  each),  while  Sweden  (10  percent),  Norway  (10  percent),  and  Finland 
(5  percent)  contributed  the  rest.30 

Under  the  direction  of  Tor  Hagfors,  the  NAIC  initiated  systematic  studies  of  several 
major  antenna  upgrading  projects  in  1984.  As  part  of  the  upgrading  project,  the  NAIC 
concluded  consulting  agreements  with  a  number  of  antenna  experts.  Among  them  were 
Alan  Love,  who  had  designed  the  telescope's  first  circular  feed,  and  Sebastian  von 
Hoerner.  Morton  S.  Roberts,  director  of  the  National  Radio  Astronomy  Observatory 
(NRAO),  and  a  member  of  the  Arecibo  Advisory  Board,  suggested  that  the  NAIC  hire  as 
a  consultant  von  Hoerner,  a  well  known  antenna  expert  working  for  the  NRAO.  The 
project  appealed  to  von  Hoerner's  imagination,  and  he  set  to  work  designing  the 
Gregorian  optics  and  laying  out  the  initial  description  of  the  shape  and  size  of  the  reflec- 
tor. He  also  realized  the  need  for  a  tertiary  reflector.31 


25.  Hagfors,  The  Arecibo  Gregorian  Upgrading,"  in  Joseph  H.  Taylor  and  Michael  M.  Davis,  eds., 
Scientific  Benefits  of  an  Upgraded  Arecibo  Telescope  (Arecibo:  NAIC,  1987) ,  p.  4,  and  Ostro,  "Benefits  of  an  Upgraded 
Arecibo  Observatory  for  Radar  Observations  of  Asteroids  and  Natural  Satellites,"  in  ibid.,  p.  233. 

26.  Campbell  9  December  1993. 

27.  Kay,  A  Line  Source  Feed,  passim,  and  Pierluissi,  A  Theoretical  Study  of  Gregorian  Radio  Telescopes,  passim. 

28.  Hagfors,  The  Arecibo  Gregorian  Upgrading,"  p.  3;  Per-Simon  Kildal,  Lynn  A.  Baker,  and  Hagfors, 
The  Arecibo  Upgrading:  Electrical  Design  and  Expected  Performance  of  the  Dual-Reflector  Feed  System," 
Proceedings  oftheIEEE82  (1994):  714. 

29.  NAIC  QR  Q3/1982,  19;  Campbell  7  December  1993;  Campbell  9  December  1993. 

30.  Lovell,  The JodreU  Bank  Telescope,  pp.  270-271. 

31.  Campbell  9  December  1993;  Hagfors,  The  Arecibo  Gregorian  Upgrading,"  p.  3. 


232 


TO  SEE  THE  UNSEEN 


X 


Ring  Beam 


Window"  membrane  60"  Dia.  Slight  Pressurization 


\ 


Figure  36 

Diagram  illustrating  Gregorian  optics  of  the  Arecibo  upgrade  subreflector.  Unlike  the  Lincoln  Laboratory  radomes,  this  one  is 
not  designed  to  allow  radio  signals  to  penetrate  the  radome  shell.  (Courtesy  of  National  Astronomy  and  Ionosphere  Center, 
which  is  operated  by  Cornell  University  under  contract  with  the  National  Science  Foundation.) 

In  addition,  Hagfors  brought  in  Per-Simon  Kildal,  a  professor  at  Chalmers  University 
of  Technology,  Gothenburg,  Sweden.  Kildal  was  an  expert  in  the  design  of  feed  horns  and 
antenna  diffraction  effects  and  a  former  student  of  Hagfors.  He  had  performed  some  of 
the  design  work  on  the  EISCAT  antennas  for  his  doctoral  thesis.  When  Kildal  worked  for 
the  NAIC  for  two  months  during  the  summer  of  1984,  he  joined  NAIC  line  feed  designer 
Lynn  A.  Baker.  Baker  and  Kildal  devised  a  practical  Gregorian  design  to  correctly  illumi- 
nate the  primary  reflector.32 


32.      Campbell  9  December  1993;  NAIC  QR  Q2/ 1984,  14;  Hagfors,  The  Arecibo  Gregorian  Upgrading," 
p.  3;  Kildal,  Baker,  and  Hagfors,  p.  714. 


ONE  STEP  BEYOND  233 


Designing  and  installing  the  Gregorian  reflector  also  changed  the  mechanical  stress 
on  the  suspended  platform.  In  order  to  work  on  the  mechanical  engineering  aspects  of 
the  project,  Hagfors  asked  Paul  Stetson,  an  antenna  builder  formerly  with  Lincoln 
Laboratory,  to  come  out  of  retirement.  Stetson  joined  the  NAIC  in  February  1984.33 

As  a  test  of  the  Gregorian  feed  concept,  the  NAIC  at  its  own  expense  constructed  and 
installed  a  so-called  mini-gregorian  antenna  which  was  to  illuminate  a  107-meter  (350-ft) 
diameter  area  of  the  reflector.  Also,  the  ground  screen  underwent  preliminary  design, 
and  another  study  determined  that  the  dish  surface  could  be  adjusted  to  be  operational 
up  to  8  GHz  (3.75  cm). 34 

In  1984,  as  these  design  studies  were  underway,  the  NAIC  submitted  a  preliminary 
proposal  to  the  National  Science  Foundation  for  Phase  1,  the  ground  screen.  The  NAIC 
submitted  the  Phase  2  preliminary  proposal  in  1985  for  the  Gregorian  reflector  system, 
the  new  radar  transmitter,  ancillary  receivers,  and  data  processing  equipment.  The  NAIC 
then  entered  into  negotiations  with  both  the  NSF  and  NASA,  the  two  NAIC  funding  agen- 
cies. The  House  subcommittee  that  handled  NSF  appropriations  was  well  aware  of  the 
upgrade  project.  Jerome  Bob  Traxler  (D-Mich.),  the  chairperson  of  the  House  subcom- 
mittee, Harry  Block,  the  NSF  director,  and  Dick  Mallow,  the  subcommittee's  chief  of  staff, 
visited  Arecibo  several  times.35 

The  key  to  selling  the  project  to  the  scientific  community,  which  ultimately  reviewed 
all  NSF  proposals,  was  the  building  of  consensus,  a  standard  strategy  among  American  sci- 
entists. The  NSF  proposals  were  supposed  to  stand  on  their  own  merit.  Whether  those 
reviews  were  good  or  bad  was  critical  to  the  success  of  the  upgrade  project.  The  keystone 
of  consensus-building  was  a  workshop  held  at  Cornell  University  13-15  October  1986.  The 
NSF  proposal  for  Phase  1  was  already  under  review,  when  the  workshop  took  place.  Talks 
highlighted  the  kinds  of  scientific  experiments  one  could  do  with  the  upgraded  telescope, 
whether  in  atmospheric  research  or  in  radio  astronomy.  Steve  Ostro,  Don  Campbell,  and 
Irwin  Shapiro  pitched  the  possibilities  for  radar  astronomy. 


33.  NAIC  QR  Q2/1984,  14;  Campbell  9  December  1993;  Hagfors,  "The  Arecibo  Gregorian  Upgrading," 
p.  3. 

34.  NAIC  QR  Q2/1984,  14,  and  Q3/1984,  15;  Hagfors,  The  Arecibo  Gregorian  Upgrading,"  p.  4; 
Kildal,  Baker,  and  Hagfors,  pp.  717-718  and  722. 

35.  Campbell  9  December  1993;  Dickman  2  December  1992. 


234 


TO  SEE  THE  UNSEEN 


Figure  37 

View  of  the,  Arealm  Observatory  dish.  The  completed  ground  screen  is  visible  in  the  background.  (Courtesy  of  National 
Astronomy  and  Ionosphere  Center,  which  is  operated  by  Cornell  University  under  contract  with  the  National  Science 
Foundation.) 

Ostro  largely  proposed  research  on  mainbelt  and  near-Earth  approaching  asteroids, 
passing  quickly  over  other  solar  system  objects,  such  as  the  moons  of  Mars,  Jupiter,  and 
Saturn.  Don  Campbell  emphasized  exploration  of  the  terrestrial  planets  and  comets.  The 
major  impact  of  the  upgrading,  he  and  Shapiro  acknowledged,  would  be  on  the  observa- 
tion of  asteroids.36  The  scientific  repercussion  of  the  Arecibo  upgrade  for  radar  astrono- 
my would  be  to  sustain  the  observatory  as  the  major  research  instrument  and  to  make 
asteroid  studies  the  predominant  area  of  research. 

The  NSF  sent  the  NAIC  upgrade  proposals  out  for  review.  The  reviews  aided  the  NSF 
in  prioritizing  its  spending.  Where  the  project  stood  within  the  NSF's  own  priority  list  of 
projects  also  was  subject  to  input  from  the  Division  of  Astronomy,  primarily,  and  from  the 


36.  Ostro,  "Benefits  of  an  Upgraded  Arecibo,"  pp.  233-239;  Campbell,  "Prospects  for  Radar 
Observations  of  Comets  and  the  Terrestrial  Planets,"  in  Taylor  and  Davis,  pp.  243-248;  Shapiro,  "Radar  Tests  of 
Gravitational  Theories  and  Other  Exotica,"  in  ibid.,  pp.  225-232. 


ONE  STEP  BEYOND  235 


Division  of  Atmospheric  Sciences.  Within  NASA,  the  planetary  program  decided  funding 
priorities.  In  1988,  following  the  Cornell  workshop,  the  NAIC  submitted  the  main  pro- 
posal for  the  Gregorian  system  and  radar  transmitter.  Numerous  discussions,  presenta- 
tions, committee  meetings,  and  reviews  followed.  Also  providing  input  was  the  Bahcall 
Committee,  the  successor  to  the  Whitford  Panel.37 

The  Bahcall  Committee,  named  for  its  chair  John  N.  Bahcall,  Princeton  Institute  for 
Advanced  Study,  and  formally  known  as  the  Astronomy  and  Astrophysics  Survey 
Committee,  was  a  group  of  15  astronomers  and  astrophysicists  commissioned  in  1989  by 
the  National  Academy  of  Sciences  to  survey  their  fields  and  to  recommend  new  ground 
and  space  programs  for  the  coming  decade.  To  carry  out  the  actual  work,  the  Committee 
established  15  advisory  panels  to  represent  different  subdisciplines,  and  those  panels  sub- 
mitted their  reports  in  June  and  July  1990.38 

Radar  astronomy  came  under  the  general  umbrella  of  the  Planetary  Astronomy 
Panel,  chaired  by  David  Morrison,  NASA  Ames  Research  Center,  chair,  and  Donald 
Hunten,  University  of  Arizona,  vice  chair.  Among  the  22  planetary  scientists  constituting 
the  panel  was  one  radar  astronomer,  Steve  Ostro.  The  Planetary  Astronomy  Panel  recom- 
mended several  facilities  as  "critically  important"  for  planetary  astronomy  in  the  1990s. 
Prioritized  according  to  their  cost  (small,  medium,  large)  within  the  categories  "space- 
based"  and  "ground-based,"  the  most  important  small  ground  facility  for  planetary  astron- 
omy was  the  Arecibo  upgrade.39 

The  upgrade  was  never  regarded  as  a  huge  project.  The  total  estimated  price  tag  of 
the  upgrade,  around  $23  million  spread  out  over  four  years,  placed  it  in  the  "small"  cate- 
gory; even  the  medium-sized  proposed  facilities  cost  substantially  more.  The  relatively 
small  total  amount  underwent  further  diminution  in  such  a  way  that  the  project  was  never 
big  enough  to  be  a  separate  line  item  within  the  budget  of  the  Office  of  Management  and 
Budget.  Both  NASA  and  the  NSF  split  the  total  cost,  which  underwent  further  division 
within  each  agency,  so  that  the  total  amount  per  year  was  never  a  huge  sum  for  each  agen- 
cy or  for  each  agency  program. 

Geoff  Briggs,  director  of  the  Division  of  Solar  System  Exploration  within  the  NASA 
Office  of  Space  Science,  chaired  discussions  about  the  project  with  the  NAIC,  NASA,  and 
the  NSF.  According  to  Don  Campbell,  "Briggs  somewhat  arbitrarily  just  took  it  on  himself 
to  break  up  who  was  going  to  pay  for  what  right  there."40 

The  allocation  of  the  costs  of  what  was  already  considered  a  small,  low-cost  project 
was  a  strategy  in  tune  with  the  budgetary  times.  NASA  would  pay  100  percent  of  the 
ground  screen  and  the  one-megawatt  radar  transmitter  costs,  but  the  money  came  from 
the  budgets  of  three  different  divisions.  The  Division  of  Solar  System  Exploration  paid  for 
the  ground  screen;  the  Office  of  Space  Communications  paid  for  the  transmitter;  and  the 
Division  of  Biological  Sciences,  the  source  of  SETI  (Search  for  Extra-Terrestrial 
Intelligence)  funding,  contributed  partially  to  the  Gregorian  reflector.  The  NSF  paid  for 
the  remainder,  with  the  Division  of  Astronomical  Sciences  paying  for  some  specific  equip- 
ment. The  distribution  of  individual  program  contributions  split  the  cost  evenly  between 
the  two  agencies  and  became  the  basis  for  the  memorandum  of  understanding  between 
NASA  and  the  NSF  that  covered  the  upgrade.41 


37.  Campbell  9  December  1993;  Kildal,  Baker,  and  Hagfors,  p.  715. 

38.  John  Bahcall,  "Preface,"  in  National  Research  Council,  The  Decade  of  Discovery  in  Astronomy  and 
Astrophysics  (Washington:  National  Academy  Press,  1991),  pp.  ix-xi. 

39.  National  Research  Council,  Working  Papers:  Astronomy  and  Astrof>hysics  Panel  Reports  (Washington: 
National  Academy  Press,  1991),  pp.  X-  l-X-20. 

40.  Campbell  9  December  1993. 

41.  Dickman  2  December  1992;  Campbell  9  December  1993. 


236  TO  SEE  THE  UNSEEN 


Titan 

The  Arecibo  upgrade,  when  completed,  promises  entirely  new  research  capabilities 
that  will  open  up  a  new  set  of  targets  to  be  explored  and  new  problems  to  be  solved. 
Another  upgrade,  though  not  intended  to  provide  new  radar  capability,  created  a  research 
instrument  that  never  existed  before.  That  was  the  Voyager  upgrade.  It  involved  improve- 
ment of  the  GSSR,  as  well  as  the  Very  Large  Array  (VLA) ,  a  radio  telescope  located  in  New 
Mexico.  For  the  VLA  upgrade,  NASA  installed  low-noise  X-band  receivers  on  each  of  the 
27  VLA  antennas.  When  radar  astronomers  linked  the  Goldstone  radar  and  the  VLA  in  a 
bistatic  mode,  they  created  a  radar  with  an  extraordinary  capacity  for  exploring  the  solar 
system. 

The  upgrade  of  the  VLA  for  the  Voyager  mission  originated  in  the  need  to  commu- 
nicate with  the  spacecraft  at  unprecedented  distances.  During  Voyager's  encounter  with 
Neptune,  its  X-band  radio  signal  would  be  less  than  one-tenth  as  strong  as  from  Jupiter 
and  less  than  one-half  as  strong  as  from  Uranus.  In  addition  to  the  enlargement  of  the 
DSN  64-meter  antennas  to  70  meters  in  diameter,  the  Neptune  encounter  required  assis- 
tance from  the  Parkes  telescope  in  Australia  and  the  VLA.  Through  the  radio  astronomy 
technique  of  arraying,  and  the  installation  of  low-noise  receivers  on  each  VLA  dish,  the 
echoes  received  from  the  VLA  were  combined  with  those  received  at  the  Goldstone 
70-meter  and  34-meter  dishes  to  provide  a  data  rate  more  than  double  that  which  would 
have  been  available  with  Goldstone's  antennas  alone.42 

The  idea  of  using  the  VLA  as  a  receiver  in  a  bistatic  radar  system  was  not  new;  Ed 
Lilley  had  suggested  some  two  decades  earlier  a  bistatic  radar  consisting  of  the  VLA  and 
the  NEROC  transmitter  for  carrying  out  planetary  radar  mapping.43  Moreover,  the  VLA 
management  already  had  thought  of  the  possibility  of  a  Goldstone-VLA  bistatic  radar  years 
earlier,  when  they  were  looking  for  a  broader  foundation  of  support  for  a  facility  strictly 
dedicated  to  radio  astronomy.  They,  therefore,  were  receptive  to  the  suggestion  of  Nick 
Renzetti  (JPL)  that  joint  Goldstone-VLA  radar  experiments  be  conducted,  provided  the 
proposed  experiments  first  would  undergo  the  normal  review  process.44 

As  the  Goldstone  and  VLA  upgrades  were  underway,  Caltech  professor  Dewey 
Muhleman  became  interested  in  the  possibilities  opened  up  by  a  Goldstone-VLA  bistatic 
radar.  After  abandoning  a  career  in  radar  astronomy  in  1966  as  professor  of  planetary  sci- 
ence at  Caltech,  Muhleman  switched  to  the  study  of  radio  emissions  from  the  planets. 
Muhleman  thought  the  Goldstone-VLA  radar  an  excellent  tool  for  exploring  Saturn's 
barely  explored  and  poorly  understood  moon,  Titan.  Scientists  knew  nothing  about 
Titan's  surface,  because  like  the  surface  of  Venus,  it  is  hidden  by  an  opaque  cloud  cover.45 

Despite,  or  perhaps  because  of,  this  lack  of  knowledge,  scientists  speculated  on  the 
nature  of  the  satellite's  surface.  According  to  conventional  wisdom,  Titan's  surface  was  an 
ocean  of  ethane  and  methane,  which  would  have  almost  no  reflecting  surface  at  radar 
wavelengths.46  In  1980,  Voyager  1  flew  past  Titan  and  provided  fresh  facts  about  the 
moon's  surface  temperature  (about  94°  Kelvin)  and  surface  pressure  (around  1,500  mil- 
libars).  Voyager  found  an  atmosphere  composed  mainly  of  nitrogen  and  trace  amounts  of 


42.  Murray  to  Morton  S.  Roberts,  25  February  1982,  "Chiron  1982  #1,"  and  Memorandum,  Associate 
Administrator  for  Space  Tracking  and  Data  Systems  to  Deputy  Director,  JPL,  28  February  1983,   "NASA 
Correspondence,  1983,  pt.  #1,"JPLPLC;  JPL  Annual  Report,  1984,  p.  13,  and  ibid.,  1987,  p.  41.JPLA. 

43.  Memorandum,  Lilley  to  CAMROC  Project  Office  Members,  HJune  1966,  18/1/AC  135,  MITA. 

44.  Renzetti  17  April  1992. 

45.  Muhleman  8  April  1993. 

46.  The  ethane-methane  ocean  model  of  Titan  was  developed  by  Jonathan  I.  Lunine,  David  J. 
Stevenson,  and  Yuk  L.  Yung.  See,  for  example,  Lunine,  Stevenson,  and  Yung,  "Ethane  Ocean  on  Titan,"  Science 
222(1983):  1229-1230. 


ONE  STEP  BEYOND  237 


hydrocarbons  and  nitriles,  including  ethane,  methane,  and  acetylene.  But  Voyager 
revealed  nothing  about  the  moon's  surface  features.47 

Titan's  surface  remained  hidden  from  the  view  of  radar  astronomers,  too.  In 
February  1979,  using  the  Arecibo  S-band  radar,  Don  Campbell,  Gordon  Pettengill,  and 
Steve  Ostro  unsuccessfully  attempted  to  detect  Titan.  Later,  in  1987  and  1992,  Dick 
Goldstein  and  Ray  Jurgens  also  failed  to  receive  echoes  from  Titan  using  the  Goldstone 
Mars  Station  alone.48  The  bistatic  Goldstone-VLA  radar,  however,  promised  an  extra 
measure  of  sensitivity. 

Muhleman  hoped  to  find  land  masses  and  challenge  the  ethane  ocean  model.  He 
already  had  conducted  a  radio  study  of  Titan,  but  that  research  had  yielded  ambiguous 
results.  Muhleman  teamed  up  with  JPL  radar  astronomer  Marty  Slade,  who  oversaw  oper- 
ation of  the  Goldstone  half  of  the  bistatic  radar.  Muhleman 's  graduate  students,  Bryan 
Butler  and  Arie  Grossman,  participated  in  the  experiments,  too.  In  order  to  test  the  sys- 
tem, Muhleman,  Slade,  and  Butler  attempted  a  known  target,  the  rings  of  Saturn,  in  the 
spring  of  1988.  The  success  encouraged  them  to  attempt  Titan.49 

Muhleman,  Butler,  and  Slade  first  observed  Titan  on  the  nights  of  3,  4,  5,  and  6  June 
1989  with  the  VLA  in  the  so-called  C  configuration,  in  which  the  maximum  separation 
among  the  27  25-meter  (82-ft)  telescopes  was  about  three  km.  The  echoes  were  marginal, 
although  those  obtained  on  4  June  were  strong,  and  the  detection  of  5  June  was  "quite 
certain."  "The  data,"  they  concluded,  "appear  to  favor  a  real  variation  in  surface  proper- 
ties but  more  observations  are  required."50 

The  backscatter  from  Titan  was  highly  diffuse,  similar  to  that  from  the  Galilean 
satellites  of  Jupiter.  The  diffuse  backscatter,  they  believed,  was  a  strong  argument  against 
an  ethane  ocean  being  the  reflecting  medium.  A  liquid  body  without  floating  scatterers 
would  be  a  specular  not  a  diffuse  reflector.  Instead,  the  radar  echoes  from  Titan  suggest- 
ed an  icy  surface  similar  to  that  of  Europa,  Ganymede,  or  Callisto.  The  experiment, 
however,  did  not  rule  out  entirely  the  existence  of  liquid  hydrocarbons  on  Titan's  surface 
that  might  exist  in  the  form  of  small  lakes. 

Muhleman,  Slade,  and  Butler  attempted  Titan  again  in  August  1992  and  in  the 
summer  of  1993.51  From  these  fresh  echoes,  they  concluded  that  Titan  does  not  always 
keep  the  same  hemisphere  towards  Saturn,  as  had  previously  been  believed.  In  addition, 
one  region  very  bright  to  the  radar  consistently  appeared  15  hours  earlier  than  expected, 
suggesting  that  its  rotational  period  was  49  minutes  shorter  than  its  orbital  period  of 
15.945  Earth  days. 

More  importantly,  variations  in  radar  reflectivity  gave  the  first  indications  of  surface 
conditions  on  Titan.  Results  from  instruments  on  the  Voyager  spacecraft  in  the  1980s 
suggested  that  there  might  be  a  global  ocean  of  liquid  ethane.  However,  Muhleman, 
Slade,  and  Butler  reported  that  only  a  few  patches  of  liquid  will  be  found  by  the  European- 
built  Huygens  probe  scheduled  to  land  on  Titan  early  in  the  next  century  after  a  journey 


47.  Muhleman,  Arie  W.  Grossman,  Bryan  J.  Butler,  and  Slade,  "Radar  Reflectivity  of  Titan,"  Science  248 
(1990):  975-980. 

48.  NAIC  QR  Ql/1979,  9;  Campbell  8  December  1993;  Goldstein  and  Jurgens,  "DSN  Observations  of 
Titan,"in  Posner.ed.  The  Telecommunications  and  Data  Acquisition  Report:  Progress  Report,  Jan.-Mar.  1992  (Pasadena: 
JPL,  1992),  pp.  377-379. 

49.  Muhleman,  G.  Berge,  and  D.  Rudy,  "Microwave  Emission  from  Titan  and  the  Galilean  Satellites," 
Bulletin  of  the  American  Astronomical  Society  16  ( 1984) :  686;  JPL  Annual  Report,  1988,  p.  29,  JPLA. 

50.  Muhleman,  Grossman,  Butler,  and  Slade,  "Radar  Reflectivity  of  Titan,"  Science  248  (1990):  975-980, 
quote  on  p.  979. 

51.  Muhleman,  Grossman,  Slade,  and  Butler,  "Titan's  Radar  Reflectivity  and  Rotation,"  Bulletin  of  the 
American  Astronomical  Society  25  (1993):  1099;  Butler,  Muhleman,  and  Slade,  "Results  from  1992  and  1993 
VLA/Goldstone  3.5  cm  Radar  Results,"  ibid.,  p.  1040;  GSSR  Min.  19  February  1993. 


238  TO  SEE  THE  UNSEEN 


aboard  the  Cassini  spacecraft.  The  moon's  surface  seems  to  be  covered  mainly  by  icy 
continents,  perhaps  coated  in  tars  of  hydrocarbons. 

The  results  of  Muhleman's  radar  research  on  Titan  were  of  enormous  interest  to 
Dennis  L.  Matson,  Cassini  project  scientist,  and  others  involved  in  the  planning  of  the 
Cassini  mission.  In  1989,  NASA  was  preparing  the  Cassini  Announcement  of  Opportunity 
for  release  on  1  December  1989.  A  major  experiment  on  Cassini,  as  then  planned,  was  a 
radar  instrument  to  be  built  byJPL.  The  nature  of  Titan's  surface  was  a  major  parameter 
in  the  design  of  any  radar  system  for  the  Cassini  mission. 

If  an  ocean  of  ethane  and  methane  really  covered  Titan,  the  radar  would  have  to  be 
designed  to  anticipate  the  special  scattering  conditions  that  such  a  surface  would  create. 
The  Goldstone-VLA  radar  data,  then,  would  be  useful  in  targeting  the  Huygens  probe, 
and  the  targeting  decisions  had  to  be  made  before  the  launch  of  the  Cassini  spacecraft 
itself.52  As  Nick  Renzetti  characterized  the  situation:  "So  why  put  a  $20  million  radar  on 
Cassini  and  get  zilch?  That  really  stirred  the  community  for  the  last  three  years."53 


The  Polar  Ice  Caps  of  Mars 


The  radar  results  from  Titan  were  revealing  but  puzzling.  The  radar  study  of  Titan 
also  highlighted  the  continuing  mission-oriented  nature  of  radar  astronomy.  The  same 
was  true  of  Mars  radar  research.  Although  Muhleman  intended  to  use  the  Goldstone-VLA 
bistatic  radar  primarily  to  study  Titan,  equally  startling  results  came  from  its  application 
to  Mercury  and  Mars.  The  Goldstone-VLA  system  allowed  radar  astronomers  to  solve 
problems  previously  unsolved  or  solved  unsatisfactorily.  The  Goldstone-VLA  work  added 
to  a  long  tradition  of  studying  Mars  topography  that  began,  as  we  saw  in  an  earlier  chap- 
ter, before  Viking  went  to  Mars,  and  continued  in  support  of  the  Viking  mission.  Most  of 
the  Mars  radar  topography  work  done  in  the  1970s,  in  fact,  related  directly  to  Viking. 

The  exploration  of  Martian  topography  and  radar  reflectivity  from  the  1970s  into  the 
1980s  had  yielded  some  rather  interesting  results.  The  studies  done  for  Viking  had 
revealed  high  roughness  (large  rms  slopes)  and  sharp  roughness  transitions  in  the  area 
around  the  Tharsis  volcanoes  and  their  associated  lava  flows.  Tharsis  itself  was  found  to 
have  a  low  overall  reflectivity.  The  most  unusual  and  controversial  development  was  the 
claim  by  Stan  Zisk  and  Peter  Mouginis-Mark,  from  their  analysis  of  Goldstone  Mars  data 
from  1971  and  1973,  that  the  Solis  Lacus  region  showed  seasonal  variations  in  its  radar 
reflectivity  which  might  indicate  the  presence  of  near-surface  liquid  water.54 

The  Tharsis  and  Syrtis  Major  regions  were  of  special  radar  interest.  Syrtis  Major  was 
a  classical  radar  dark  spot  on  Mars.  From  topographical  data,  George  Downs  showed  that 
the  Tharsis  bulge  was  lower  than  originally  thought.  Geologists  used  the  radar  data  to 
show  that  Tharsis  had  been  tectonically  inactive  since  the  occurrence  of  the  last  major  lava 
flows.  Topographical  data  for  the  south  Tharsis  region  suggested  that  it  was  an  ancient 
impact  basin.  Interpretation  of  the  radar  studies  of  Downs  and  Simpson  (at  Arecibo)  of 
the  Syrtis  Major  area  by  USGS  geologist  Gerry  Schaber  indicated  that  it  was  a  low-relief 


52.  Muhleman  to  W.  E.  Giberson,  10  February  1989,  and  Memorandum,  D.  L.  Matson  to  Dumas, 
8  January  1991,  Renzetti  materials. 

53.  Renzetti  17  April  1992. 

54.  Harmon,  "Radar  Observations  of  Mars  and  Mercury:  History  and  Progress,"  paper  read  at  the 
Thirtieth  Anniversary  Celebration  of  Planetary  Radar  Astronomy,  3  October  1991,  Caltech;  Zisk  and  P.  J. 
Mouginis-Mark,  "Anomalous  Region  on  Mars:  Implications  for  Near-Surface  Liquid  Water,"  Nature  288  (1980): 
735-738.  See  also  Aaron  P.  Zent,  Fraser  P.  Fanale,  and  Roth,  "Possible  Martian  Brines:  Radar  Observations  and 
Models,  "Journal  of  Geophysical  Research  vol.  95,  no.  B9  (1990):  14,531-14,542. 


ONE  STEP  BEYOND  239 


shield  volcano,  rather  than  the  impact  basin  it  had  always  been  believed  to  be,  because  it 
was  not  very  heavily  cratered.55 

John  Harmon  arrived  shortly  after  the  installation  of  the  Arecibo  S-band  radar  as  a 
Research  Associate,  after  graduating  from  the  University  of  California  at  San  Diego  with  a 
doctoral  thesis  on  solar  winds.  John  Harmon  began  a  series  of  studies  of  Mars  topography 
and  scattering,  initially  under  the  direction  of  Don  Campbell,  and  drew  the  first  topo- 
graphic profile  of  Syrtis  Major.  Starting  in  February  1980,  Harmon  and  Steve  Ostro  under- 
took a  study  of  Tharsis  and  the  surrounding  area  using  both  the  Arecibo  S-band  and  the 
Goldstone  X-band  radars  and  taking  data  in  both  senses  of  circular  polarization,  in  order 
to  compare  polarization  ratios  at  both  S-band  and  X-band. 

While  the  initial  focus  in  1980  had  been  on  the  Tharsis  region,  the  1982  observations 
took  in  a  broader  area  and  revealed  correlations  between  maximum  depolarization  and 
the  volcanic  regions  Tharsis  and  Elysium,  while  the  heavily  cratered  upland  terrain  yield- 
ed relatively  low  depolarization.  This  led  to  the  suggestion  by  Harmon  and  Ostro,  and 
confirmed  independently  by  radar  astronomer  Tommy  Thompson  and  USGS  Menlo  Park 
geologist  Henry  J.  Moore,  who  used  Goldstone  data,  that  most  of  the  strong  sources  of  dif- 
fuse and  depolarized  backscatter  on  Mars  were  rough-surfaced  lava  flows.56 

Such  was  the  state  of  radar  studies  of  Martian  topography  and  scattering,  when 
Muhleman,  Butler,  and  Slade  began  looking  at  Mars  with  the  Goldstone-VLA  bistatic  radar 
in  1988.  The  proximity  of  Mars,  in  contrast  to  the  great  distance  to  Titan,  allowed  them 
to  construct  full-disk  images  of  the  planet.  During  the  1988  Mars  opposition,  moreover, 
the  Earth  and  Mars  were  closer  than  they  had  been  for  17  years. 

These  images  were  not  the  product  of  radar  range-Doppler  techniques,  but  of  stan- 
dard VLA  radio  astronomy  imaging  software.  The  array  and  its  software  avoided  the  prob- 
lem of  north-south  ambiguity  that  typically  plagued  planetary  range-Doppler  mapping; 
the  VLA  radio  imaging  software,  which  Muhleman  regularly  used  in  his  planetary  radio 
astronomy  research,  created  unambiguous  images.  In  this  bistatic  imaging  mode,  the 
Goldstone  radar  illuminated  the  target  with  a  continuous-wave  signal  whose  frequency  was 
adjusted  to  remove  the  Doppler  shift.  When  the  VLA  aimed  at  a  target,  the  signal  came 
from  all  over  the  planet,  as  though  the  target  were  a  natural  emitter  of  radio  waves.  Then 
the  powerful  imaging  software  of  the  VLA  processed  these  echoes. 

Muhleman,  Butler,  and  Slade  observed  Mars  twice  during  the  opposition  of  1988  and 
three  times  during  the  opposition  of  1992-1993.  They  obtained  surface  resolutions  of  80 
km  at  the  subradar  point.  The  Mars  observations  differed  from  those  of  Titan,  because  for 
Mars  the  VLA  A  array  (36-km  maximum  spacings)  was  used.  The  transmitted  signal  to 


55.  Downs,  Mouginis-Mark,  Zisk,  and  Thompson,  "New  Radar-Derived  Topography  for  the  Northern 
Hemisphere  of  Mars,"  Journal  of  Geophysical  Research  87  (1982):  9747-9754;  Mouginis-Mark,  Zisk,  and  Downs, 
"Ancient  and  Modern  Slopes  in  the  Tharsis  Region  of  Mars,"  Nature  297  (1982):  546-550;  Simpson,  Tyler, 
Harmon,  and  Alan  R.  Peterfreund,  "Radar  Measurement  of  Small-  Scale  Surface  Texture:  Syrtis  Major,"  Icarus  49 
(1982):  258-283;  Schaber,  "Syrtis  Major:  A  Low-relief  Volcanic  Shield,"/<nmia/  of  Geophysical  Research  87  (1982): 
9852-9866;  Roth,  Downs,  Saunders,  and  Schubert,  "Radar  Altimetry  of  South  Tharsis,  Mars,"  Icarus  42  (1980): 
287-316;  R.  A.  Craddock,  R.  Greeley,  and  P.  R.  Christensen,  "Evidence  for  an  Ancient  Impact  Basin  in  Daedalia 
Planum,  Mars,"  Journal  of  Geophysical  Research  95  (1990):  10,729-10,741;  Downs,  R.  Green,  and  Reichley,  "Radar 
Studies  of  the  Martian  Surface  at  Centimeter  Wavelengths:  The  1975  Opposition,"  Icarus  33  (1978):  441-453; 
Roth,  Saunders,  Downs,  and  Schubert,  "Radar  Altimetry  of  Large  Martian  Craters,"  Icarus  79  (1989):  289-310. 

56.  Harmon  15  March  1994;  Harmon,  Campbell,  and  Ostro,  "Dual-Polarization  Radar  Observations  of 
Mars:  Tharsis  and  Environs,"  Icarus  52  (1982):  171-187;  Harmon  and  Ostro,  "Mars:  Dual-Polarization  Radar 
Observations  with  Extended  Coverage,"  /caru$62  (1985):  110-128;  Thompson  and  Henry  J.  Moore,  "A  Model  for 
Depolarized  Radar  Echoes  from  Mars,"  Proceedings  of  the  Lunar  Planetary  Science  Conference  19th  (1989):  409-422; 
Moore  and  Thompson,  "A  Radar-Echo  Model  of  Mars,"  Proceedings  of  the  Lunar  Planetary  Science  Conference  21 
(1991):  457-472.  Later  radar  mapping  supported  these  observations:  Muhleman,  Butler,  Grossman,  Slade,  and 

Jurgens,  "Radar  Images  of  Mars,"  Science  253  (1991):  1508-1513;  Harmon,  Michael  P.  Sulzer,  Phillip  J.  Perillat, 
and  Chandler,  "Mars  Radar  Mapping:  Strong  Backscatter  from  the  Elysium  Basin  and  Outflow  Channel,"  Icarus 
95  (1992):  153-156. 


240  TO  SEE  THE  UNSEEN 


Mars  was  circularly  polarized  and  both  opposite  circular  and  same  circular  echoes  were 
received  and  mapped.  As  anticipated,  the  opposite  circular  echoes  were  dominated  by  the 
so-called  specular  (or  phase-coherent)  reflections. 

Muhleman  and  Butler  found  regions  with  anomalously  high  radar  cross  sections  on 
Mars,  particularly  around  the  three  Tharsis  volcanoes  and  Olympus  Mons.  These, 
Muhleman  recalled,  '^just  lit  up  like  a  Christmas  tree."  In  contrast,  the  region  west  of 
Tharsis,  extending  over  2,000  km  in  the  East-West  direction  and  500  km  across  at  its  widest 
point,  displayed  no  cross  section  distinguishable  from  the  noise  in  either  polarization. 
"We  didn't  believe  that  result.  We've  never  seen  that  on  any  real  surface,"  Muhleman 
explained.57 

Muhleman  dubbed  the  area  "Stealth,"  because  it  was  invisible  to  the  radar. 
Photographs  do  not  indicate  the  nature  of  the  Stealth  region.  Muhleman  interpreted  the 
lack  of  radar  echo  as  arising  from  a  deposit  of  ash  or  pumice  spewed  from  the  bordering 
Tharsis  volcanoes  and  carried  by  winds  blowing  off  the  Tharsis  ridge.  He  estimated  that 
the  Stealth  material  would  have  a  density  of  less  than  about  0.5  grams  per  cubic  centime- 
ter, be  free  of  rocks  larger  than  one  centimeter  across,  and  have  a  depth  of  at  least  five,  if 
not  ten,  meters. 

Equally  surprising  was  the  radar  signature  of  the  residual  southern  polar  ice  cap.  The 
1988  observations  were  made  in  the  southern  hemisphere  around  -24°  latitude  in  late 
spring,  so  the  seasonal  carbon  dioxide  ice  cap  had  sublimated  away  and  exposed  the  resid- 
ual southern  polar  ice  cap.  That  area  had  the  highest  radar  cross  section  of  any  other  area 
observed  on  the  planet  in  1988.  Furthermore,  the  residual  ice  cap  exhibited  strong 
circular  polarization  inversion.  Thus,  unexpectedly,  part  of  one  of  the  terrestrial  planets 
displayed  radar  characteristics  more  typical  of  the  Galilean  satellites. 

When  Muhleman,  Butler,  and  Slade  looked  at  the  VIA  images,  they  "instantly  saw 
that  the  brightest  thing  on  the  planet  was  the  South  pole,  which  turned  out  to  be  the 
residual  South  polar  ice  cap,"  Muhleman  recalled.  'The  amazing  thing  to  us  was  that  this 
ice  was  so  reflecting,  so  bright,  and  its  size  was  exactly  the  residual  polar  cap."58  Also 
amazing  was  the  fact  that  Dick  Simpson  and  Len  Tyler  had  failed  to  notice  any  unusual 
scattering  properties  from  the  North  pole  in  data  from  a  bistatic  radar  experiment 
conducted  from  the  Viking  spacecraft.59 

Butler,  Muhleman,  and  Slade  again  looked  at  Mars  with  the  Goldstone-VLA  radar 
during  the  1992-1993  opposition,  when  the  planet's  North  pole  was  visible  from  Earth.  It 
was  early  northern  spring  on  Mars,  and  much  of  the  seasonal  carbon  dioxide  polar  ice  cap 
was  present.  They  were  anxious  to  study  the  northern  polar  ice  cap,  but  the  ice  was  invis- 
ible to  the  radar.  In  stark  contrast  to  the  southern  pole,  no  regions  with  enhanced  radar 
cross  sections  appeared.  "We  still  haven't  figured  that  out,"  Muhleman  admitted.  "It's 
totally  a  mystery  why  we  didn't  find  the  residual  North  polar  ice  cap."60 

The  high  radar  cross  section  and  polarization  inversion  of  the  Martian  South  polar 
ice  cap  were  confirmed  by  observations  made  at  the  Arecibo  Observatory  during  the  1988 
opposition  by  John  Harmon,  Marty  Slade,  and  R.  Scott  Hudson.  Hudson  was  a  Caltech 
graduate  student  working  on  a  doctoral  degree  in  electrical  engineering  and  had  chosen 
aircraft  radar  imaging  as  his  dissertation  topic.  Like  those  made  by  Harmon  and  Ostro  in 


57.  Muhleman  27  May  1994. 

58.  Muhleman  27  May  1994. 

59.  Muhleman  27  May  1994;  Slade  24  May  1994;  Muhleman,  Butler,  Grossman,  and  Slade,  "Radar 
Images  of  Mars,"  Science  253  (1991):  1508-1513;  Butler,  "3.5-cm  Radar  Investigation  of  Mars  and  Mercury: 
Planetological  Implications,"  Ph.D.  diss.,  California  Institute  of  Technology,  9  May  1994;  Simpson  and  Tyler, 
"Viking  Bistatic  Radar  Experiment:  Summary  of  First-Order  Results  Emphasizing  North  Polar  Data,"  Icarus  46 
(1981):  361-389. 

60.  Muhleman  27  May  1994;  Butler,  "3.5-cm  Radar  Investigation;"  Butler,  Muhleman,  and  Slade, 
"Martian  Polar  Regions:  3.5  cm  Radar  Images,"  Lunar  and  Planetary  Science  Conference  25  ( 1994) :  211-212;  Butler, 
Muhleman,  and  Slade,  The  Polar  Regions  of  Mars:  3.5  cm  Radar  Images,"  Icarus  submitted  in  May  1994. 


ONE  STEP  BEYOND  241 


1980  and  1982,  these  were  monostatic,  dual-polarization  continuous-wave  observations 
made  with  the  Arecibo  S-band  and  the  Goldstone  X-band  radars. 

After  obtaining  promising  results  from  a  comparison  of  the  1988  data  at  both  wave- 
lengths, an  additional  set  of  observations  were  made  at  S-band  and  X-band  during  the 
1990  opposition.  Despite  scheduling  difficulties  and  the  demands  of  competing  types  of 
radar  observations  (ranging  observations  for  altimetry  and  mapping  were  also  made  at 
the  two  facilities),  a  good  continuous-wave  data  set  for  S/X-band  comparison  was 
obtained  in  1990. 

The  Arecibo  data  confirmed  the  existence  of  Stealth.  Using  an  algorithm  developed 
by  Scott  Hudson  and  the  Doppler  spectra  taken  in  the  unexpected  sense  of  polarization, 
they  produced  depolarized  reflectivity  maps  that  showed  clearly  the  anomalously  high 
radar  reflectivity  and  polarization  inversion  of  the  residual  South  polar  icecap.  Hudson's 
algorithm  allowed  the  investigators  to  use  only  Doppler  spectra,  without  range  measure- 
ments, to  create  a  two-dimensional  map  of  the  Martian  disk  largely  free  of  north-south 
ambiguity.61 

Hudson's  imaging  technique  was  necessary  in  order  to  overcome  the  planet's  over- 
spread nature.  In  comparison  to  Venus,  Mars  rotates  rapidly  on  its  axis  and  causes  radar 
echoes  from  the  limb  (beyond  the  subradar  area)  to  disperse  broadly.  The  echo  delay 
corresponding  to  the  radius  of  Mars  is  22.6  microseconds,  which  is  much  greater  than  the 
maximum  interval  of  0.725  microseconds  needed  to  preserve  complete  spectral  informa- 
tion over  the  band  of  frequencies  present  in  the  echo.  As  a  result,  when  the  computer 
samples  signals,  echoes  from  different  ranges  contaminate  each  other  and  become 
indistinguishable.  Such  radar  targets  are  called  "overspread." 

Arecibo  scientists  also  had  a  technique  for  overcoming  the  overspread  problem,  but 
they  were  not  motivated  to  apply  it  until  the  Goldstone-VLA  results  became  known. 
Harmon  explained:  "Dewey  Muhleman,  with  his  VIA  experiment,  spurred  us  on  to  try 
and  do  better.  I  really  hadn't  been  thinking  about  the  overspreading  problem.  I  probably 
should  have;  I  should  have  been  trying  to  figure  out  ways  to  get  around  it."62 

Overspreading  was  a  problem  that  ionospheric  scientists  had  been  dealing  with  for 
years,  because  the  ionosphere  is  an  extremely  overspread  target.  Michael  P.  Sulzer,  an 
ionosphericist  at  the  Arecibo  Observatory,  solved  the  problem  for  the  ionosphere  by  using 
non-repeating  codes.  Although  Don  Campbell  at  one  time  had  asked  Sulzer  to  think 
about  applying  the  technique  to  Mars,  no  progress  had  been  made  until  Harmon  told 
Sulzer  he  was  interested  in  trying  the  non-repeating  code  technique. 

Harmon  then  worked  with  Sulzer  and  Phil  Perillat,  who  wrote  the  modified  data- 
taking  program.  Normally,  when  a  continuous-wave  radar  sends  out  a  signal,  the  signal 
carries  a  code  with  a  finite  number  of  elements,  and  the  code  repeats  at  a  regular  inter- 
val. Harmon  and  Sulzer  tested  the  non-repeating  code,  called  alternately  the  "random 
code"  or  "coded  long  pulse"  technique,  and  it  worked  the  first  time.  Then  Harmon  wrote 
programs  to  do  the  data  analysis. 

Harmon  and  Sulzer  made  their  first  random-code  observations  on  18  nights  during 
the  Mars  opposition  of  September-December  1990  and  created  range-Doppler  maps. 
Those  maps,  like  all  range-Doppler  maps,  included  a  north-south  ambiguity  around  the 
Doppler  equator.  However,  from  eyeball  comparisons  with  maps  obtained  early  and  late 
in  the  opposition,  Harmon  was  able  to  resolve  much  of  the  ambiguity. 


61.  Hudson,  telephone  conversation,  21  November  1994;  Hudson  and  Ostro,  "Doppler-Radar  Imaging 
of  Spherical  Planetary  Surfaces,  "Journal  of  Geophysical  Research  95  (1990):  10,947-10,963;  Harmon,  Slade,  and 
Hudson,  "Mars  Radar  Scattering:  Arecibo/Goldstone  Results  at  12.6-  and  3.5-cm  Wavelengths,"  Icarus98  (1992): 
240-253. 

62.  Harmon  15  March  1994. 


242  TO  SEE  THE  UNSEEN 


The  random-code  maps  confirmed  the  observations  made  with  the  Goldstone-VLA 
radar  and  revealed  new  information  about  the  Elysium  region,  which  Harmon  had  spent 
a  long  time  studying  in  previous  observations  of  Mars.  Through  those  and  subsequent 
observations  made  during  the  1992-1993  opposition,  he  discovered  strong  depolarized 
radar  echoes  from  the  Elysium/Amazonis  outflow  channel  complex.  He  interpreted  the 
region,  which  was  very  young  by  Martian  standards,  as  having  lava  flows  that  appeared  to 
have  partially  filled  pre-existing  channels  cut  by  flowing  water.63 

Mercury:  Baked  Alaska? 

The  strange  radar  signature  exhibited  by  the  southern  residual  polar  ice  cap  of  Mars, 
reminiscent  of  the  radar  characteristics  of  the  icy  Galilean  satellites  of  Jupiter,  did  not  pre- 
pare Muhleman,  Butler,  and  Slade  for  the  surprising  discovery  of  ice  on  Mercury.  Mercury 
was  simply  too  hot  to  support  even  the  smallest  ice  deposit.  Previous  radar  observations  of 
Mercury  had  focused  on  scattering  and  topography  and  had  not  detected  ice. 

Analysis  of  Mercury  data  taken  between  1963  and  1965  at  Goldstone,  Haystack,  and 
Arecibo  snowed  the  planet  to  have  a  radar  roughness  'Very  similar"  to  that  of  the  Moon. 
Dick  Goldstein,  from  radar  observations  of  Mercury  made  in  1969,  started  characterizing 
Mercury's  topography.  His  work  was  the  most  detailed  radar  study  of  Mercury's  surface 
prior  to  the  Mariner  10  encounters  and  provided  the  first  strong  evidence  for  the  exis- 
tence of  craters  on  the  surface.  Dick  Ingalls  at  Haystack  and  Don  Campbell  at  Arecibo  also 
found  altitude  variations  on  Mercury's  surface  from  1971  observations.  Some  of  the  ear- 
liest topographic  radar  studies  of  Mercury  were  carried  out  at  Haystack  by  Bill  Smith  and 
Dick  Ingalls.64 

These  early  radar  studies  of  Mercury  were  not  linked  to  any  specific  NASA  mission, 
but  not  because  of  any  radar  shortcomings.  NASA  made  no  meaningful  effort  to  study 
Mercury  until  Mariner  10  flew  by  and  photographed  that  planet  in  1974-1975.  The 
Mariner  10  photographs  revealed  a  heavily  cratered,  lunar-like  surface,  as  predicted  by 
radar.  Although  Mariner  10  photographed  over  half  of  Mercury's  surface  during  its  flyby 
mission,  it  did  not  photograph  any  of  the  side  not  then  exposed  to  the  Sun's  light  and 
yielded  only  limited  topographic  information.  Moreover,  its  flyby  geometry  prevented 
Mariner  10  from  examining  either  pole  directly.65 

These  gaps  in  Mercury  coverage  motivated  a  program  of  observations  at  Arecibo  and 
Goldstone.  John  Harmon  and  Don  Campbell,  working  in  collaboration  with  Brown 
University  geologists  D.  L.  Bindschadler  and  James  W.  Head,  carried  out  a  campaign  of 


63.  Harmon  15  March  1994;  NAIC  QR  Q2/1990,  7;  Q4/1990,  7-8;  and  Ql/1991,  7;  Ql/1993,  9; 
Harmon,  Sulzer,  and  Perillat,  "Mars  Radar  Mapping:  Strong  Depolarized  Echoes  from  the  Elysium/Amazonis 
Outflow  Channel  Complex,"  Lunar  and  Planetary  Science  Conference  22  (1991):  513. 

64.  Muhleman,  "Radar  Scattering  from  Venus  and  Mercury  at  12.5  cm,"  Journal  of  Research  of  the  National 
Bureau  of  Standards,  Section  D:  Radio  Science  69D  (1965):  1630-1631;  Evans,  Brockelman,  Henry,  Hyde,  Kraft,  W. 
A.  Reid,  and  W.  W.  Smith,  "Radio  Echo  Observations  of  Venus  and  Mercury  at  23  cm  Wavelength,"  The 
Astronomical fournaHO  (1965):  486-501;  Pettengill,  Dyce,  and  Campbell,  "Radar  Measurements  at  70  cm  of  Venus 
and  Mercury,"  The  Astronomical  Journal  72  (1967):  330-337;  Goldstein,  "Mercury:  Surface  Features  Observed  dur- 
ing Radar  Studies,"  Science  168  (1970):  467-469;  Goldstein,  "Radio  and  Radar  Studies  of  Venus  and  Mercury," 
Radio  Science5  (1970):  391-395;  Goldstein,  "Radar  Observations  of  Mercury,"  The  Astronomical  Journal  76  (1971): 
1152-1154;  Goldstein,  "Review  of  Surface  and  Atmosphere  Studies  of  Venus  and  Mercury,"  Icarus  17  (1972): 
571-575;  Zohar  and  Goldstein,  "Surface  Features  on  Mercury,"  The  Astronomical  Journal  79  (1974):  85-91;  Smith, 
Ingalls,  Shapiro,  and  Ash,  "Surface-Height  Variations  on  Venus  and  Mercury,"  Radio  Science  5  (1970):  411-423; 
Ingalls  and  Rainville,  "Radar  Measurements  of  Mercury:  Topography  and  Scattering  Characteristics  at  3.8  cm," 
The  Astronomical  Journal  77  (1972):  185-190. 

65.  Murray,  Michael  J.  S.  Belton,  G.  Edward  Danielson,  Merton  E.  Davies,  Donald  E.  Gault,  Hapke, 
Brian  O'Leary,  Robert  G.  Strom,  Verner  Suomi,  and  Newell  Trask,  "Mercury's  Surface:  Preliminary  Description 
and  Interpretation  from  Mariner  10  Pictures,"  Science  185  (1974):  169-179. 


ONE  STEP  BEYOND  243 


S-band  radar  observations  of  Mercury  at  Arecibo  from  1978  to  1984.  They  measured 
Mercury's  topography  over  much  of  the  equatorial  zone  (between  12°  North  and  5°  South 
latitude),  an  area  not  imaged  by  Mariner  10,  and  concluded  that  radar  depths  for  large 
craters  supported  previous  indications  from  photographs  that  Mercury's  craters  were  shal- 
lower than  lunar  craters  of  the  same  size.66  At  the  same  time,  Ray  Jurgens,  using  the 
Goldstone  S-band  radar,  started  an  ongoing  series  of  Mercury  observations  to  study  the 
planet's  topography  and  to  correlate  radar  measurements  with  Mariner  10  visual  images, 
in  collaboration  with  geologists  Gerald  G.  Schaber  (USGS  Flagstaff)  and  P.  E.  Clark 

GPL)-67 

Such  was  the  state  of  radar  research  on  Mercury,  when  Muhleman,  Butler,  and  Slade 

began  their  observations  with  the  Goldstone-VLA  bistatic  radar  during  the  inferior  con- 
junction of  August  1991.  Although  they  made  further  observations  during  the  inferior 
conjunctions  of  November  1992  and  February  1994,  the  1992  effort  failed  because  of 
transmitter  problems,  and  the  1994  data  yet  remains  to  be  reduced.68  The  key  results, 
then,  were  those  from  the  1991  observations.  They  did  nothing  less  than  revolutionize  our 
knowledge  of  Mercury  in  a  way  that  radar  had  not  done  since  the  discovery  of  the  plan- 
et's 59-day  spin  rate  by  radar  astronomers  Gordon  Pettengill  and  Rolf  Dyce  in  1965. 

During  the  first  Goldstone-VLA  observation  of  Mercury  on  8  August  1991,  Ray 
Jurgens  coordinated  activities  at  the  Goldstone  X-band  transmitter,  while  Marty  Slade  and 
Bryan  Butler  awaited  the  echoes  at  the  VLA,  which  was  operating  in  the  so-called  A  array, 
the  most  widely  spaced  configuration.  During  the  10  hours  of  observation,  the  VLA 
received  in  both  senses  of  circular  polarization.  At  the  time  of  these  observations,  Mercury 
was  at  inferior  conjunction  and  presented  the  hemisphere  not  photographed  by  Mariner 
10,  roughly  between  180°  to  360°,  to  the  radar.  As  a  result,  the  subradar  point  was  far 
enough  North  to  see  over  the  North  pole  and  into  areas  believed  to  be  permanently  shad- 
owed from  the  Sun. 

When  Muhleman,  Butler,  and  Slade  looked  at  their  results,  they  were  astonished; 
they  had  found  ice  near  Mercury's  North  pole.  What  signalled  the  presence  of  ice  was  the 
abnormal  radar  signature  of  the  spot,  which  was  unusually  bright  and  showed  a  ratio  of 
same  circular  to  opposite  circular  polarization  greater  than  unity,  that  is,  a  circular  polar- 
ization inversion.  This  was  the  same  type  of  radar  signature  displayed  by  Jupiter's  Galilean 
moons.  Muhleman  recalled:  "We  instantly  looked  at  the  first  image  and  saw  this  white  spot 
on  the  North  pole.  We  said,  'My  God!  Are  we  going  to  find  an  ice  cap  on  every  planet  we 
look  at?'  This  is  crazy!"  Marty  Slade  remembered  looking  at  the  bright  spot  and  reacting: 
"It's  not  possible  that  could  be  ice!  It's  too  hot!"69 

Muhleman,  Butler,  and  Slade  again  observed  Mercury  with  the  Goldstone-VLA  radar 
two  weeks  later  on  23  August  1991.  This  time,  they  transmitted  both  right-handed  (RCP) 
and  left-handed  circular  (LCP)  polarization,  and  they  received  in  both  senses  of  polariza- 
tion for  either  sense,  so  that  they  could  make  all  four  correlations  of  the  two  polarizations 
(RCP  to  LCP,  RCP  to  RCP,  LCP  to  RCP,  and  LCP  to  LCP) .  Mercury  as  seen  from  Earth  had 
rotated  101°.  The  subradar  point  was  around  353°  and  the  ice  near  the  northern  polar 


66.  Harmon,  Campbell,  Bindschadler,  Head,  and  Shapiro,  "Radar  Altimetry  of  Mercury:  A  Preliminary 
Analysis,"  Journal  of  Geophysical  Research  91  (1986):  385-401. 

67.  See,  for  example,  P.  E.  Clark,  M.  E.  Strobell,  Schaber,  and  Jurgens,  "Some  New  Radar-Derived 
Topographic  Profiles  of  Mercury,"  Bulletin  of  the  American  Astronomical  Society  16  (1984):  668;  Clark,  Jurgens,  and 
M.  Kobrick,  "Analyses  of  Radar-Derived  Topography  and  Scattering  Properties  of  Mercury's  Equatorial  Region," 
Bulletin  of  the  American  Astronomical  Society  17  (1985):  712;  and  Clark,  M.  A.  Leake,  Slade,  Jurgens,  Robinett,  and 
C.  Franck,  "Scattering  and  Altimetry  Measurements  from  Goldstone  Radar  Observations  of  Mercury  in  1987," 
Bulletin  of  the  American  Astronomical  Society  19  (1987):  863. 

68.  Buder,  "3.5-cm  Radar  Investigation,"  preface. 

69.  Muhleman  27  May  1994;  Slade  24  May  1994. 


244  TO  SEE  THE  UNSEEN 


region  still  stood  out  brightly  and  exhibited  polarization  inversion.  The  researchers  now 
knew  that  this  was  no  fluke.70 

Surprised  by  their  own  results,  Muhleman,  Slade,  and  Butler  announced  their  results 
in  two  separate  talks  given  on  6  November  1991  at  the  meeting  of  the  AAS  Division  for 
Planetary  Science,  held  in  Palo  Alto,  California.71  The  scientific  community  greeted  the 
news  of  their  discovery  with  a  fair  amount  of  skepticism.72  Prior  to  the  launch  of  Mariner 
10,  few  had  suggested  the  presence  of  ice  on  Mercury,  and  then  for  the  wrong  reasons. 
Some  drawings  of  Mercury  showed  a  white  spot  visible  at  the  northern  pole,  and  in  1974, 
on  the  eve  of  Mariner  10's  first  reconnaissance  of  Mercury,  an  atmospheric  scientist  had 
proposed  that  ice  could  have  accumulated  in  the  small  planet's  polar  regions,  perhaps  in 
permanently  shaded  regions.73 

The  evidence  for  the  presence  of  ice  near  Mercury's  northern  pole  was  based  on  an 
analogy  between  the  radar  signatures  of  known  icy  targets,  the  Galilean  moons  of  Jupiter, 
and  those  found  on  Mercury.  But  more  convincing  evidence  was  needed,  because  Mariner 
10  had  documented  that  planet's  intense  surface  heat.  The  landscape  was  a  parched 
wasteland  of  impact  craters  and  volcanic  plains,  where  midday  temperatures  soared  to 
700°  K,  hot  enough  to  melt  lead.  At  the  same  time,  though,  Mariner  10's  ultraviolet 
spectrometer  had  identified  traces  of  hydrogen  and  oxygen  in  the  tenuous  atmosphere  of 
Mercury.  Project  scientists  had  considered  them  to  be  remnants  of  the  comets  and  aster- 
oids that  periodically  collide  with  the  planet.74 

While  such  collisions  would  explain  the  existence  of  water  on  Mercury,  an  explana- 
tion for  the  existence  of  a  permanent  water  ice  deposit  on  the  planet  came  from  a 
consideration  of  the  geometry  of  Mercury's  orbit.  An  impact  crater  could  provide  an  area 
of  permanent  shade,  provided  that  the  geometry  was  just  right.  Mercury  spins  on  its  axis 
and  rotates  around  the  Sun  in  such  a  way  that  its  equator  always  lies  in  the  same  plane  as 
the  Sun.  As  a  result,  neither  pole  ever  sees  more  than  a  sliver  of  the  Sun's  disk  above  the 
horizon.  On  the  other  hand,  the  plane  of  Mercury's  orbit  about  the  Sun  is  inclined  by 
seven  degrees  relative  to  that  of  the  Earth,  so  that  Earth-based  radars  can  see  into  impact 
craters  that  are  never  directly  illuminated  by  the  Sun. 

David  A.  Paige  and  Stephen  Wood  of  UCLA  recomputed  the  thermal  environment 
for  Mercury's  surface  and  concluded  that  the  interior  slopes  of  impact  craters  within  five 
degrees  of  the  poles  would  be  cold  enough  to  keep  the  loss  of  water  ice  through  subli- 
mation at  essentially  zero.  Other  planetary  scientists  also  began  to  argue  for  the  existence 
of  ice  in  craters  on  Mercury,  and  they  suggested  that  craters  on  the  Moon  might  also 
contain  ice.  As  early  as  1961,  Kenneth  Watson,  Bruce  C.  Murray,  and  Harrison  Brown  had 
proposed  that  ice  might  exist  in  permanently  shadowed  craters  near  the  lunar  poles,  but 


70.  Slade,  Butler,  Muhleman,  "Mercury  Radar  Imaging:  Evidence  for  Polar  Ice,"  Science  258  (23  October 
1992):  635-640;  Butler,  Muhleman,  and  Slade,  "Mercury:  Full-Disk  Radar  Images  and  the  Detection  and  Stability 
of  Ice  at  the  North  Pole,  "Journal  of  Geophysical  Research  vol.  98,  no.  E8  (1993):  15,003-15,023. 

71.  Slade,  Butler,  and  Muhleman,  "Mercury  Goldstone-VLA  Radar:  Part  I,"  Bulletin  of  the  American 
Astronomical  Society  23  (1991):  1197,  and  Buder,  Muhleman,  Slade,  andjurgens,  "Mercury  Goldstone-VLA  Radar. 
Part  II,"  Ibid.,  p.  1200. 

72.  David  A.  Paige,  "Chance  for  Snowballs  in  Hell,"  Nature  369  (1994):  182;  Chapman,  "Ice  Right 
Under  the  Sun,"  Nature  354  (1991):  504-505;  J.  Kelley  Beatty,  "Mercury's  Cool  Surprise,"  Sky  &  Telescope  83 
(January  1992):  35-36. 

73.  Richard  Baum,  "Radar  Bright,  Ice  Bright:  V.  A.  Firsoff  and  Ice  Caps  on  Mercury,"  Journal  of  the  British 
Astronomical  Association  103  (1993):  126  and  139;  Firsoff,  "Could  Mercury  have  Ice  Caps?"  The  Observatory  91 
(1971):  85-87;  and  G.  E.  Hunt,  "There  is  no  Evidence  for  Ice  Caps  on  Mercury,"  The  Observatory  92  (1972):  16; 
Beatty,  "Mercury's  Cool  Surprise,"  Sky  &  Telescope  83  (1992):  35-36;  Gary  E.  Thomas,  "Mercury:  Does  its 
Atmosphere  Contain  Water?"  Science  183  (1974):  1197-1198. 

74.  Beatty,  p.  36;  Chapman,  "Ice,"  p.  505;  Chapman,  Planets  of  Rock  and  Ice:  From  Mercury  to  the  Moons  of 
Saturn  (New  York:  Scribner,  1982);  and  Faith  Vilas,  Chapman,  and  Matthews,  eds.,  Mercury  (Tucson:  University 
of  Arizona  Press,  1988). 


ONE  STEP  BEYOND  245 


to  date  no  lunar  probe,  not  even  the  Clementine  orbiter,  has  found  any  ice  on  the 
Moon.75  A  radar  search  at  Arecibo  also  proved  unsuccessful. 

Nick  Stacy,  a  graduate  student  working  on  a  thesis  in  radar  astronomy  under  Don 
Campbell,  looked  for  ice  on  the  Moon  with  the  Arecibo  radar.  Earlier,  starting  in  1982, 
Don  Campbell  and  Peter  Ford  had  carried  out  high-resolution  range-Doppler  imaging  of 
the  Moon  and  found  no  evidence  of  ice,  but  they  were  not  looking  for  it  Ford  and 
Campbell  brought  the  resolution  of  their  images  down  from  300  to  150  meters,  using  the 
Higuillales  antenna  in  a  bistatic  mode  with  the  big  dish.  Stacy  reduced  the  resolution  to 
20  meters  and  aimed  at  the  lunar  poles.  Unfortunately,  the  radar  could  not  see  far  enough 
into  the  polar  craters  and  detected  no  ice,  though  Stacy  found  some  unusual  scattering 
properties  abound  a  number  of  lunar  craters.76 

Although  the  discovery  of  lunar  crater  ice  remained  elusive,  John  Harmon  and 
Marty  Slade  at  the  Arecibo  Observatory  confirmed  the  existence  of  ice  on  Mercury.  They 
imaged  Mercury  using  the  non-repeating  code  technique  developed  by  Harmon  and 
Mike  Sulzer  in  order  to  overcome  overspreading  on  Mars.  These  Arecibo  images,  accord- 
ing to  David  Paige,  left  "little  room  for  doubt"  about  the  presence  of  ice  on  Mercury.77 

Soon  after  observing  Mercury  on  8  August  1991  with  the  Goldstone-VLA  radar, 
Marty  Slade  travelled  to  the  Arecibo  Observatory  to  collaborate  with  Harmon  on  a  dif- 
ferent set  of  Mercury  observations.  They  acquired  their  initial  data  prior  to  8  August  1991, 
on  28  separate  dates  during  the  periods  28  March  to  21  April  1991,  31  July  to  29  August 
1991,  and  14  to  29  March  1992.  During  the  spring  1991  observations,  the  subradar  point 
of  the  Arecibo  telescope  subtended  an  area  in  the  southern  hemisphere  of  Mercury,  while 
the  summer  1991  observations  covered  a  portion  of  the  northern  hemisphere,  as  the 
Goldstone-VLA  had.  The  March  1992  data  added  to  that  already  observed  in  the  southern 
hemisphere. 

When  Slade  arrived  at  Arecibo,  his  first  time  at  the  observatory,  Harmon  had  not  yet 
analyzed  the  spring  1991  data;  he  had  been  too  busy  studying  Mars  data.  Slade  suggested 
to  Harmon  that  they  analyze  the  Mercury  data  and  look  for  the  icy  radar  signature  near 
the  North  pole,  which  he,  Muhleman,  and  Butler  had  just  found  with  the  Goldstone-VLA 
radar.  According  to  Harmon,  Slade  said,  "We  think  it's  the  pole;  we're  not  sure."  The 
Arecibo  data  confirmed  the  Goldstone-VLA  discovery.  There  was  no  question  of  priority; 
Muhleman,  Butler,  and  Slade  discovered  the  ice  on  Mercury  first,  with  the  Goldstone-VLA 
radar. 

Harmon  also  examined  the  data  collected  from  the  southern  hemisphere  of 
Mercury  in  March-April  1991.  "I  saw  a  feature  coming  from  what  I  figured  probably  had 
to  be  the  South  pole,  because  the  latitude  was  about  five  degrees  South  [sic],"  Harmon 
related.  "I  was  pretty  convinced  it  was  coming  from  the  South."78  To  confirm  that  the 
South  pole  was  the  source  of  the  icy  radar  signature  and  not  an  artefact  of  north-south 
ambiguity,  which  would  have  shown  a  portion  of  the  northern  polar  echo  at  the  South 
pole,  Harmon  and  Slade  observed  Mercury  again  in  March  1992,  when  the  subradar  point 
was  again  in  the  southern  hemisphere.  The  polar  ice  feature  was  seen  again,  confirming 
the  presence  of  ice  at  the  planet's  South  pole.79 


75.  Simpson  10  May  1994;  Paige,  Stephen  E.  Wood,  and  Ashwin  R.  Vaasavada,  The  Thermal  Stability  of 
Water  Ice  at  the  Poles  of  Mercury,"  Science  258  (1992):  643-646;  Andrew  P.  Ingersoll,  Tomas  Svitek,  and  Murray, 
"Stability  of  Polar  Frosts  in  Spherical  Bowl-Shaped  Craters  on  the  Moon,  Mercury,  and  Mars,"  Icarus  100  (1992): 
40-47;  Kenneth  Watson,  Murray,  and  Harrison  Brown,  "The  Behavior  of  Volatiles  on  the  Lunar  Surface,  Journal 
of  Geophysical  Research  66  (1961):  3033-3045. 

76.  Ford  3  October  1994;  Campbell   10  March   1993;  Campbell  8  December  1993;  Stacy,  "High- 
Resolution  Synthetic  Aperture  Radar  Observations  of  the  Moon,"  Ph.D.  diss.,  Cornell  University,  May  1993. 

77.  Paige,  "Chance  for  Snowballs  in  Hell,"  Nature  369  (1994):  182. 

78.  Harmon  15  March  1994. 

79.  Harmon  15  March  1994;  Harmon  and  Slade,  "Radar  Mapping  of  Mercury:  Full-  Disk  Images  and 
Polar  Anomalies,"  Scumce258  (1992):  640-642;  Harmon  and  Slade,  "An  S-band  Radar  Anomaly  at  the  North  Pole 
of  Mercury,"  Bulletin  of  the  American  Astronomical  Society  23  (1991):  1121. 


246  TO  SEE  THE  UNSEEN 


Next,  Harmon  and  Slade  proceeded  to  fit  the  radar  results  to  photographic  data 
from  Mariner  10.  Showing  a  correlation  between  a  known  crater  and  the  radar  ice  would 
be  persuasive  confirmation  of  the  discovery.  Matching  the  northern  polar  radar  ice  loca- 
tion with  a  crater  was  hard;  no  Mariner  10  photographs  were  available  for  the  entire 
region.  Furthermore,  the  North  polar  radar  anomaly  was  too  large  to  fit  within  a  single 
crater.  The  image,  instead,  appeared  to  consist  of  a  number  of  crater-size  (15-60  km  in 
diameter)  bright  spots.  Harmon  and  Slade  plotted  those  features  on  a  locating  map  cre- 
ated by  NASA  and  the  USGS  and  assigned  letter  labels  to  those  features  that  lay  in  the  pho- 
tographed hemisphere  and  to  three  prominent  features  in  the  unphotographed  hemi- 
sphere. Many  of  the  radar  spots  (8  out  of  20)  appeared  to  correspond  to  impact  craters. 
Correlating  the  southern  polar  radar  image  with  topography  was  simpler.  The  radar  spot 
was  entirely  inside  a  crater  called  Chao  Meng-Fu.80 

The  Goldstone-VLA  and  Arecibo  images  of  Mercury  once  again  highlighted  how 
planetary  radar  astronomy  often  solves  problems  left  unsolved  or  unsatisfactorily  solved  by 
optical  techniques.  The  discovery  of  ice  near  Mercury's  North  and  South  poles,  moreover, 
has  inspired  the  European  Space  Agency  to  mount  a  major  "keystone"  mission  to  Mercury 
in  search  of  polar  ice,  as  well  as  a  more  modest-sized  NASA  Discovery  flight.81 

Radar  astronomers  also  sought  signs  of  anomalous  radar  signatures  on  other  terres- 
trial planets.  Muhleman,  Butler,  and  Slade  turned  the  Goldstone-VLA  radar  on  Venus 
twice,  18  and  25  February  1990,  receiving  both  senses  of  polarization  in  order  to  detect 
any  peculiar  polarization  inversion,  and  made  two  maps.  The  maps  had  several  striking 
features.  Surprisingly,  Alpha  Regio  had  a  high  unexpected  (depolarized  or  SC)  reflectivi- 
ty on  both  maps  and  contained  the  second  highest  reflectivity  values  after  Maxwell.  On 
the  second  day's  map,  the  point  of  highest  reflectivity  was  in  the  Aphrodite  region  and  was 
not  visible  in  the  previous  map.  On  both  maps,  many  very  small  areas,  only  a  few  pixels 
across,  also  had  large  unexpected  (depolarized  or  SC)  reflectivities,  and  some  of  them 
corresponded  to  mapped  elevated  areas  such  as  Gula  Mons,  Sif  Mons,  and  Bell  Regio. 
Muhleman,  Butler,  and  Slade  concluded  that  a  correlation  existed  between  unexpected 
(depolarized  or  SC)  reflectivities  and  elevation.  Further  bistatic  observations  of  Venus  in 
the  spring  of  1993  furnished  fuel  for  another  Muhleman  graduate  student,  Albert 
Haldeman,  to  begin  doctoral  research,  while  Slade  and  Ray  Jurgens  also  found  highly 
reflective  areas  on  Venus  using  just  the  Goldstone  radar.82 

Asteroids 

Throughout  the  1980s  and  into  the  1990s,  the  number  of  asteroids  discovered  and 
the  number  of  publications  dealing  with  asteroids  grew  at  an  unprecedented  rate,  at  first 
as  a  result  of  the  Palomar  Planet-Crossing  Asteroid  Survey  studies  initiated  in  the  1970s, 
then  as  the  number  of  asteroid  researchers  swelled.  In  1932,  an  astronomer  discovered 
the  first  Earth-crossing  asteroid,  1862  Apollo.  By  1994,  about  200  Earth-crossing  asteroids 
were  known,  more  than  half  of  which  had  been  discovered  in  the  previous  seven  years;  yet 


80.  Harmon,  Slade,  Velez,  Andy  Crespo,  M.  J.  Dryer,  andj.  M.Johnson,  "Radar  Mapping  of  Mercury's 
Polar  Anomalies,"  Nature.  369  (1994):  213-215;  Harmon  and  Slade,  "Radar  Mapping  of  Mercury:  Full-Disk 
Images  and  Polar  Anomalies,"  Science  258  (1992):  640-643. 

81.  Muhleman  24  May  1994;  Paige,  "Snowballs,"  p.  182. 

82.  Slade  24  May  1994;  K.  A.  Tryka,  Muhleman,  Butler,  Berge,  Slade,  and  Grossman,  "Correlation  of 
Multiple  Reflections  from  the  Venus  Surface  with  Topography,"  Lunar  Planetary  Science  22  (1991):  1417;  Jurgens, 
Slade,  and  Saunders,  "Evidence  for  Highly  Reflecting  Materials  on  the  Surface  and  Subsurface  of  Venus,"  Science 
240  (1988):  1021-1023;  Butler,  "3.5-cm  Radar  Investigation,"  passim;  Slade  24  May  1994;  and  information  pro- 
vided by  Bryan  J.  Butler. 


ONE  STEP  BEYOND 


247 


the  undiscovered  population  is  huge.  In  the  decade  1975-1985  alone,  the  total  number 
of  catalogued  asteroids  rose  from  2,000  to  more  than  3,200. 83 

The  field,  as  measured  by  the  expanding  literature,  was  undergoing  the  kind  of  swift 
growth  that  is  typical  of  Big  Science.  Asteroid  astronomy  became  a  new  theoretical  frame- 
work with  problems  that  radar  astronomers  sought  to  solve.  Radar  found  its  niche  within 
asteroid  astronomy  because  it  could  solve  problems  that  other  observational  techniques 
could  not  do,  namely,  the  creation  of  more  accurate  and  reliable  ephemerides  and  the 
imaging  of  asteroids. 

The  focus  of  asteroid  research  was  on  near-Earth  asteroids,  although  main  belt 
objects  remained  of  interest,  too.  Near-Earth  asteroids,  like  meteorites,  are  thought  to 
come  primarily  from  mainbelt  asteroids  (Table  8).  A  large  population  of  asteroids  also 
cross  the  orbits  of  Earth  and  Mars.  The  term  near-Earth  asteroid  usually  means  any  aster- 
oid that  can  come  close  to  the  Earth,  whether  or  not  it  crosses  the  orbit  of  the  Earth.  Eros, 
for  example,  crosses  the  orbit  of  Mars,  but  it  is  not  an  Earth-crossing  asteroid  and  does  not 
come  near  the  Earth.  Almost  all  of  the  near-Earth  asteroids  detected  so  far  by  radar  are 
Earth-crossers. 


Table  8 
Asteroids  Detected  by  Radar,  1968-1994 


12  — 


10  — 


8  — 


6  - 


4  - 


2  - 


O  G*  ^ 

c>         o^         2> 
o*>         c>         o> 


Data  provided  by  Steve  Ostro 


Mainbelt  Asteroids 
Near-Earth  Asteroids 


83.      Ostro,  Campbell,  and  Shapiro,  "Mainbelt  Asteroids:  Dual-  Polarization  Radar  Observations,"  Science 
229  (1985):  442. 


248  TO  SEE  THE  UNSEEN 


The  more  interesting  near-Earth  asteroids  also  were  better  radar  targets  than  main 
belt  asteroids,  because  now  and  then  they  come  closer  to  the  Earth.  With  targets  as  small 
as  asteroids,  some  only  a  kilometer  or  two  in  diameter,  the  distance  to  the  target  is  critical 
to  radar  observations.  The  number  of  asteroids  observed  by  radar  astronomers  grew 
rapidly  during  the  1980s  because  of  the  availability  of  radars  with  sufficient  power  and  sen- 
sitivity to  detect  and  study  them.  Another  key  factor  in  the  growth  of  radar  asteroid  stud- 
ies was  the  decision  of  one  radar  astronomer,  Steve  Ostro,  to  begin  studying  asteroids 
almost  exclusively.  Quickly,  his  efforts  dominated  the  asteroid  study  started  at  Arecibo  and 
Goldstone  in  the  1970s. 

Before  beginning  this  intense  study  of  asteroids,  Ostro  had  been  making  radar  obser- 
vations of  the  Galilean  moons  and  the  rings  of  Saturn.  In  March  1979,  about  the  time  of 
Voyager's  encounter  with  Jupiter,  Ostro  attended  the  third  Tucson  asteroid  conference 
organized  by  Tom  Gehrels.  There,  Ray  Jurgens  and  Gordon  Pettengill  delivered  a  joint 
paper  on  radar  observations  of  asteroids.  The  conference,  especially  the  talks  that  placed 
the  science  of  meteoritics  and  asteroid  science  in  context  with  each  other,  gave  Ostro  the 
asteroid  bug.  He  saw  how  the  study  of  asteroids  was  essential  to  understanding  the  origin 
and  evolution  of  the  solar  system.  He  also  realized  that  radar  was  potentially  the  primary 
post-discovery  technique  for  observing  asteroids,  and  that  asteroids,  unlike  planets  and 
their  moons,  constitute  a  huge  and  diverse  population.84 

Later  in  1979,  his  MIT  dissertation  completed,  Ostro  took  a  teaching  position  at 
Cornell  University  and  began  preparing  a  campaign  of  asteroid  observations  at  Arecibo. 
The  following  year,  he  submitted  his  first  NASA  proposal  for  support  of  asteroid  research. 
Echoing  the  work  of  Jurgens  a  few  years  earlier,  Ostro  laid  out  those  asteroid  opportuni- 
ties that  would  become  available  over  the  forthcoming  decade  at  Arecibo,  as  well  as  the 
kinds  of  information  he  expected  from  his  experiments.  As  targets,  Ostro  proposed  three 
main  belt  asteroids  (Iris  in  September  1980,  Psyche  in  November  1980,  and  Vesta  in 
February  1981)  and  two  Earth-crossing  asteroids  (1862  Apollo  in  November  1980  and 
1915  Quetzalcoatl  in  March  1981).  He  planned  to  detect  echoes  from  each  target,  esti- 
mate echo  strength,  and  measure  polarization,  spectral  bandwidth,  and  Doppler  shift. 
From  those  four  quantities,  Ostro  proposed  to  estimate  asteroid  size  and  rotation,  place 
constraints  on  the  composition  and  structure  of  asteroid  surfaces,  and  improve  knowl- 
edge of  their  orbital  parameters.85 

Over  the  following  years,  the  estimation  of  asteroid  physical  properties  and  the  deter- 
mination and  refinement  of  their  orbits  remained  fundamental  aspects  of  Ostro's  radar 
studies  of  asteroids.  He  systematically  took  range  and  Doppler  data  on  all  asteroids,  as  well 
as  polarization  measurements  (receiving  in  both  the  expected  and  unexpected  senses)  in 
order  to  best  estimate  their  surface  roughness  and  structure.  From  measurements  of  the 
surface's  reflectivity  came  estimates  of  the  bulk  density  of  the  surface,  its  porosity,  and  rel- 
ative metallic  composition.  With  each  observation,  Ostro  tried  to  contribute  to  scientific 
knowledge  about  asteroids. 

Ostro  also  studied  mainbelt  asteroids.  "Virtually  every  experiment  gave  an  interest- 
ing result,  and  each  radar  signature  was  different,"  Ostro  recalled.  "Every  single  experi- 
ment was  lucrative."86  By  1992,  Ostro  had  observed  28  near-Earth  and  36  mainbelt 
asteroids.  Between  1980  and  1985  alone,  he  made  dual-polarization  observations  of  20 
mainbelt  asteroids  at  Arecibo.  These  objects  had  low  circular  polarization  ratios  (the  ratio 
of  unexpected  to  expected  echo  power)  ranging  from  about  0.00  to  0.40.  The  lowest 


84.  Ostro  25  May  1994;  Pettengill  and  Jurgens,  "Radar  Observations  of  Asteroids,"  in  Gehrels  and 
Matthews,  pp.  206-211. 

85.  Ostro  25  May  1994;  Ostro,  "Radar  Investigations  of  Asteroids,"  proposal  submitted  to  NASA  in  June 
1980  for  support  1  November  1980  through  31  October  1981,  Ostro  materials. 

86.  Ostro  25  May  1994. 


ONE  STEP  BEYOND  249 


value,  0.05  ±  0.02  for  the  asteroid  2  Pallas,  required  that  nearly  all  the  echo  arise  from 
single-reflection  backscattering  from  very  smooth  surface  elements. 

"It  became  clear,"  Ostro  explained,  "that  the  mainbelt  asteroids  had  a  dispersion  of 
reflectivities  and  polarization  ratios.  This  was  evidence  for  diversity  in  surface  structure 
and  in  surface  bulk  density."87  The  data  collected  helped  to  characterize  asteroid  surfaces 
at  scales  between  several  centimeters  and  several  kilometers  and  furnished  constraints  on 
surface  bulk  density  and  metal  concentration,  beyond  those  constraints  obtained  by 
optical  methods. 

The  metallic  composition  of  the  asteroids  was  an  interesting  question  relating  to  pos- 
sible meteoritic  analogues.  The  radar  observations  suggested  wide  variations  in  metal 
abundance,  porosity,  and  decimeter-scale  roughness  on  mainbelt  asteroid  surfaces,  under- 
scoring the  diversity  of  the  asteroid  population  already  evident  from  visible  and  infrared 
wavelength  studies.  Although  the  radar  signatures  of  mainbelt  asteroids  required 
substantial  surface  roughness  at  some  scale  much  larger  than  a  meter,  Ostro  could  not  dis- 
cern the  precise  scale  of  this  structure,  much  less  the  actual  morphologies  of  surface 
features.  Similarly,  the  radar  albedos  bolstered  the  hypothesis  that  metal  concentrations 
on  asteroids  run  the  gamut.  Serious  questions  remain,  however,  about  detailed  mineralo- 
gies, meteoritic  associations,  and  evolutionary  histories.88 

"Each  of  the  near-Earth  asteroids  is  interesting  in  its  own  way,"  Ostro  pointed  out, 
"and  still  some  interesting  mysteries  remain."89  Echoes  from  the  near-Earth  asteroid  1986 
DA  showed  it  to  be  significantly  more  reflective  than  other  radar-detected  asteroids.  This 
result  supported  the  hypothesis  that  1986  DA  was  a  piece  of  nickel-iron  metal  derived 
from  the  interior  of  a  much  larger  object  that  melted,  differentiated,  and  cooled,  and 
subsequently  was  disrupted  in  a  catastrophic  collision.  This  two-kilometer-sized  asteroid 
appeared  smooth  at  centimeter  to  meter  scales  but  extremely  irregular  at  10-  to  100-meter 
scales.  It  might  be  (or  have  been  part  of)  the  parent  body  of  some  iron  meteorites.  The 
composition  of  asteroids  thus  bears  directly  on  the  question  of  their  relationship  to  mete- 
orites, as  well  as  the  relationship  between  near-Earth  and  mainbelt  asteroids.90 

Starting  in  1983,  Steve  Ostro  began  observing  echo  spectra  with  unusual  shapes, 
including  some  spectra  with  double  peaks  (called  bimodal).  The  first  asteroid  to  show  a 
bimodal  spectra  was  2201  Oljato,  observed  during  12-17  June  1983  at  Arecibo.  Asteroid 
astronomers  had  been  discussing  binary  asteroids  and  contact-binary  asteroids  for  a  long 
time,  but  no  evidence  of  their  existence  was  at  hand.  216  Kleopatra,  a  large  mainbelt  aster- 
oid, exhibited  a  strong  bimodal  echo  spectrum.  "That  almost  definitely  is  a  contact  bina- 
ry," Ostro  explained.  "But  almost  definitely  is  not  definitely."91 

Proof  of  the  existence  of  binary  and  contact-binary  asteroids  eventually  came  from 
radar  data.92  Finding  that  proof  was  a  problem  left  unsolved  by  optical  and  other  research 
techniques.  To  the  telescope,  the  biggest  asteroid  looks  like  a  little  dot,  its  shape  indis- 
cernible. Radar  succeeded  in  solving  that  problem  through  the  development  of  new  imag- 
ing and  modeling  techniques.  The  key  to  developing  an  appropriate  technique,  though, 
was  to  avoid  simplistic  models.  Too,  it  was  important  that  the  asteroid  approach  Earth 
close  enough  to  provide  the  Arecibo  and  Goldstone  radars  a  sufficiently  strong  echo  to 
resolve  the  target. 


87.  Ostro  25  May  1994. 

88.  Ostro,  Campbell,  and  Shapiro,  "Mainbelt  Asteroids:  Dual-  Polarization  Radar  Observations,"  Science 
229  (1985):  442-446. 

89.  Ostro  25  May  1994. 

90.  Ostro,  Campbell,  Chandler,  Hine,  Hudson,  Rosema,  and  Shapiro,  "Asteroid  1096  DA:  Radar 
Evidence  for  a  Metallic  Composition,"  Sdence252  (1991):  1399-1404. 

91.  Ostro  25  May  1994. 

92.  See,  for  example,  the  discussion  in  W.  I.  McLaughlin,  "Radar  Tracking  of  Asteroids,"  Sf>arf flight  34 
(1992):  167-169. 


250  TO  SEE  THE  UNSEEN 


Ray  Jurgens  developed  the  first  modelling  technique  for  describing  asteroid  shapes 
in  the  1970s.  He  applied  it  to  spectral  data  from  Eros.  Steve  Ostro  applied  Jurgens'  triax- 
ial  ellipsoid  model  to  his  1980  and  earlier  1972  Toro  data  and  derived  a  rough  description 
of  the  asteroid.93  Similarly,  when  he  applied  Jurgens'  model  to  the  Earth-crossing  asteroid 
2100  Ra-Shalom  in  1981,  Ostro  found  it  to  have  a  somewhat  irregular  shape.94 

With  researchers  at  Cornell,  Ostro  developed  a  different  modelling  technique,  one 
that  synthesized  echo  spectra  acquired  at  different  rotational  phases  of  the  asteroid  into 
a  convex  envelope,  called  the  hull,  which  represented  the  asteroid's  silhouette  as  viewed 
from  a  pole.  After  he  fit  the  hull  model  to  Jurgens'  Eros  data,  Ostro  modeled  the  Earth- 
crossing  asteroids  1627  Ivar  and  1986  DA,  observed  in  July  1985  and  April  1986  at  Arecibo. 
Interestingly,  the  hull  estimates  indicated  that  1986  DA's  hull  was  "extremely  irregular, 
highly  nonconvex,  and  possibly  bifurcated."95 

The  case  of  1986  DA  suggested  that  any  asteroid  model  had  to  accommodate  the  pos- 
sibility that  the  target  might  not  be  convex;  both  Jurgens'  triaxial  ellipsoid  and  the  hull 
models  were  inadequate.  Ostro  also  attempted  to  image  asteroids  with  range-Doppler 
mapping  techniques,  beginning  with  1627  Ivar  in  1985. 

Range-Doppler  mapping  revealed  a  bimodal  distribution  of  echo  power,  suggesting 
that  the  target  was  not  convex.  All  previous  images  had  relied  exclusively  on  Doppler  spec- 
tra data;  these  were  the  first  range-resolved  images  of  an  asteroid.  Nonetheless,  they  failed 
to  define  the  asteroid's  global  shape.96 

The  next  opportunity  to  attempt  range-Doppler  imaging  came  in  1988,  with  the 
close  approach  to  Earth  of  the  small  asteroid  1980  PA.  The  technicians  at  Arecibo 
improved  the  telescope's  data  acquisition  software  and  hardware,  in  order  to  improve 
resolution  of  the  asteroid;  the  resolution  of  the  Goldstone  radar  on  the  same  target  was 
still  not  fine  enough.  The  Goldstone  radar  did  not  achieve  the  limit  needed  for  radar 
asteroid  observations  until  1986,  when  the  Voyager  upgrades  were  completed.97 

Ostro  again  attempted  range-Doppler  images,  this  time  of  1989  PB,  later  known  as 
4769  Castalia.  On  9  August  1989,  Eleanor  Helin  discovered  the  object  on  photographic 
plates  taken  at  Palomar  Observatory.  Orbital  calculations  two  days  later  showed  that  the 
asteroid  would  pass  through  the  Arecibo  Observatory's  declination  window  during 
19-22  August  and  that  at  closest  approach,  Castalia  would  be  only  0.027  astronomical 
units  from  Earth.  These  were  ideal  conditions  for  imaging  the  asteroid  at  Arecibo,  though 
not  so  at  Goldstone.  Communications  with  Voyager  2,  which  was  making  its  closest 
approach  to  Neptune,  occupied  the  Goldstone  70-meter  antenna;  it  was  unavailable  for 
use  as  a  radar  telescope  until  30  August,  when  some  observations  of  Castalia  took  place 
after  closest  approach.  "At  Goldstone,"  Ostro  recalled,  "everything  was  a  disaster.  We  had 
an  eight-hour  track,  and  we  got  about  20  minutes  of  data."98 

Getting  time  on  the  Arecibo  antenna  on  such  short  notice  (10  days  after  detection) 
was  not  a  problem;  Ostro  already  had  time  to  observe  Victoria,  a  mainbelt  asteroid,  which 
had  shown  a  hint  of  a  double-peak  spectral  structure  in  1982.  After  doing  a  few  runs  on 


93.  Ostro  25  May  1994;  Ostro,  Campbell,  and  Shapiro,  "Radar  Observations  of  Asteroid  1685  Toro,"  The 
Astronomical  Journal  88  (1983):  565-576. 

94.  Ostro,  Alan  W.   Harris,   Campbell,   Shapiro,   and  James  W.  Young,   "Radar  and   Photoelectric 
Observations  of  Asteroid  2100  Ra-Shalom,"  7eanw60  (1984):  391-403. 

95.  Ostro,  Robert  Connelly,  and  Leila  Belkora,  "Asteroid  Shapes  from  Radar  Echo  Spectra:  A  New 
Theoretical  Approach,"  Icarus  73  (1988):  15-24;  Ostro,  Rosema,  and  Jurgens,  'The  Shape  of  Eros,"  Icarus  84 
(1990):  334-351;  Ostro,  Campbell,  Chandler,  Hine,  Hudson,  Rosema,  and  Shapiro,  "Asteroid  1096  DA:  Radar 
Evidence  for  a  Metallic  Composition,"  Science  252  (1991):  1399-1404,  esp.  pp.  1400-1401. 

96.  Ostro  25  May  1994;  Ostro,  Campbell,  Hine,  Shapiro,  Chandler,  C.  L.  Werner,  and  Rosema,  "Radar 
Images  of  Asteroid  1627  Ivar,"  The.  Astronomical Journal  99  (1990):  2012-2018. 

97.  Ostro  25  May  1994. 

98.  Ostro  25  May  1994. 


ONE  STEP  BEYOND 


251 


Figure  38 

Range-Doppler  radar  images  of  Asteroid  1627  Ivar,  1985,  made  at  the  Arecibo  Observatory  by  Steve  Ostro.  These  are  theferst 
radar  images  made  of  an  asteroid.  (Courtesy  of  Jet  Propulsion  Laboratory.) 

Victoria,  Ostro  spent  the  rest  of  the  time  on  Castalia.  "We  saw  CW  [continuous-wave] 
echoes  instantly,"  Ostro  remembered.  "A  few  of  them  from  the  first  day  looked  strongly 
bifurcated."  This  was  the  first  echo  signature  that  said  'This  is  a  contact  binary."  Although 
he  had  never  claimed  discovery  of  bifurcated  asteroids  in  print,  Ostro  had  seen  the 
idiosyncratic  radar  signatures  several  times  before." 

From  the  Doppler  and  range  data,  Ostro  created  64  images  of  the  asteroid  with  an 
average  of  two  dozen  pixels  each.  Each  image  was  bifurcated  and  showed  a  bimodal 
distribution  of  echo  power.  Reading  the  sequence  of  images  from  left  to  right  from  top  to 
bottom,  one  can  see  the  asteroid  rotate. 

When  Ostro  presented  the  images  at  the  AAS  Division  for  Planetary  Science  meeting 
a  few  months  later,  they  attracted  a  dramatic  intensity  of  attention;  it  was  no  less  than  the 
first  time  that  anyone  had  resolved  the  shape  of  an  asteroid  from  Earth.  'This  was  a  major 
breakthrough,  definitely  a  major  breakthrough,"  Ostro  reflected.100 


99.  Ostro  25  May  1994. 

100.  Ostro  25  May  1994;  Ostro,  Chandler,  Hine,  Rose  ma,  Shapiro,  and  Yeomans,  "Radar  Images  of 
Asteroid  1989  PB,"  Science  248  (1990):  1523-1528. 


252  TO  SEE  THE  UNSEEN 


About  a  year  after  the  imaging  of  Castalia,  Scott  Hudson  started  working  on  a  math- 
ematical modelling  technique  to  reconstruct  the  asteroid's  shape  in  three  dimensions. 
While  still  a  Caltech  graduate  student,  Hudson  had  worked  with  Ostro  in  developing  a 
technique  for  creating  planetary  Doppler  images  free  of  north-south  ambiguity.  Hudson 
devised  a  complex  mathematical  model  with  169  parameters  in  order  to  capture  the  shape 
of  asteroid  Castalia.  The  resultant  three-dimensional  model  showed  indisputably  that  the 
asteroid  was  bifurcated  into  two  distinct,  irregular,  kilometer-sized  lobes.101 

Modelling  three-dimensional  asteroid  shapes  from  radar  data  provided  further  evi- 
dence for  the  existence  of  asteroids  with  exotic  shapes  upon  the  approach  of  1989  AC 
(later  known  as  4179  Toutatis),  discovered  in  January  1989.  Because  of  its  extremely  close 
approach  to  Earth,  9.4  lunar  distances  on  8  December  1992,  Toutatis  showed  high 
promise  as  a  candidate  for  imaging.  Ostro  proposed  a  Toutatis  experiment  to  the  NAIC 
and  to  Nick  Renzetti,  explaining  how  extraordinary  the  opportunity  was  and  urging  that 
Goldstone  also  make  observations. 

Ostro  planned  to  use  both  telescopes  to  take  data  in  both  senses  of  polarizations  and 
to  create  range-Doppler  images  of  several  thousand  pixels,  considerably  more  resolution 
than  had  been  achieved  ever  before.  The  high  resolution  was  possible  at  Arecibo  and 
Goldstone  because  of  incremental  improvements  made  in  the  data  acquisition  hardware 
and  software  over  the  preceding  years.  Ostro  obtained  continuous-wave  echoes  at 
Goldstone  on  27  November,  then  range-Doppler  images  daily  from  2-18  December  1992 
and  at  Arecibo  each  day  from  13-19  December.  In  addition  to  the  routine  monostatic 
observations,  Ostro's  team  took  advantage  of  new  antennas  recently  made  available.  They 
observed  Toutatis  bistatically  with  the  DSS-14  transmitting  and  a  new  34-meter  beam- 
waveguide  antenna  (DSS-13)  21  km  away  receiving,  and  on  one  day  they  received  with 
both  DSS-14  and  DSS-13  to  acquire  interferometric  data.  On  yet  another  day,  they  col- 
lected data  with  the  Goldstone-VLA  radar. 

Preliminary  analysis  of  the  data  showed  Toutatis  to  have  an  unusually  slow  rotation 
rate  and  a  maximum  dimension  of  no  less  than  3.5  km.  Interestingly,  too,  Toutatis 
appeared  to  consist  of  two  irregularly-shaped  components  in  close  contact.  The  images 
provided  a  first  glimpse  of  craters  on  an  Earth-crossing  asteroid,  as  well.  The  asteroid's 
roughness,  as  measured  by  the  circular  polarization  ratio,  indicated  a  considerable  degree 
of  general  roughness  at  centimeter-to-decimeter  scales,  supporting  the  belief  that  Toutatis 
had  undergone  a  complex  collisional  history. 


101.  Hudson,  telephone  conversation,  21  November  1994;  Ostro  25  May  1994;  Hudson  and  Ostro, 
"Shape  of  Asteroid  4769  Castalia  (1989  PB)  from  Inversion  of  Radar  Images,"  Science  263  (1994):  940-943; 
Hudson  and  Ostro,  "Doppler-Radar  Imaging  of  Spherical  Planetary  Surfaces,  "Journal  of  Geophysical  Research  95 
(1990):  10,947-10,963. 


ONE  STEP  BEYOND 


253 


Figure  39 

Radar  images  of  Asteroid  1989  PB  (later  known  as  4769  Castalia).  The  asteroid's  rotation  is  noticeable  in  the  64  images. 
(Courtesy  of  Jet  Propulsion  Laboratory.) 


254 


TO  SEE  THE  UNSEEN 


Model  of  Asteroid  4769  Castalia.  It  was  the  first  three-dimensional  model  of  an  asteroid  ever  produced.  The  picture  shows  16 
different  views  of  a  three-dimensional  model  of  Castalia,  which  is  1.8  km  across  at  its  widest.  The  model  was  created  by  Scott 
Hudson  (Washington  State  University)  and  Steve  Ostro  ([PL)  from  data  taken  at  Arecibo  Observatory  in  1989.  (Courtesy  of 
Jet  Propulsion  Laboratory,  photo  no.  P43041A.) 

Since  then,  Scott  Hudson  has  elaborated  his  model  to  recreate  three-dimensional 
asteroid  shapes.  With  Toutatis,  he  was  dealing  with  over  1,000  parameters.  The  application 
of  Hudson's  reconstruction  technique  to  the  Toutatis  images  was  complicated  by  the  aster- 
oid's rotation.  Unlike  all  other  targets  detected  by  radar,  Toutatis  was  in  a  tumbling  rota- 
tional state. 

At  the  1994  AAS  Division  for  Planetary  Science  meeting  in  November  1994,  Ostro 
and  Hudson  presented  several  movies  of  Castalia,  including  one  in  which  the  asteroid  was 
portrayed  as  it  might  be  viewed  in  space,  complete  with  fictional  optical  illumination.  The 
use  of  the  older  Castalia  data  was  on  purpose;  it  suggested  the  potential  rewards  of  using 
higher  resolution  data.  In  addition  to  Castalia  and  Toutatis,  Ostro  and  Hudson  began 
working  in  1994  on  three-dimensional  modeling  of  1620  Geographos,  an  asteroid  which 
the  ill-fated  Department  of  Defense's  Clementine  spacecraft  was  scheduled  to  observe 
during  a  flyby  mission.  Although  a  computer  malfunction  prevented  the  Clementine 
encounter,  Ostro  captured  a  detailed  sequence  of  Geographos  images  at  Goldstone  only 
days  before  the  scheduled  flyby.  Subsequent  modeling  of  the  data  has  yielded  an  impres- 
sive simulation  of  an  asteroid  flyby.102 


102.  Ostro  25  May  1994;  Hudson,  telephone  conversation,  21  November  1994;  Ostro,  Jurgens,  Rosema, 
R.  Winkler,  D.  Howard,  R.  Rose,  Slade,  Yeomans,  Campbell,  Perillat,  Chandler,  Shapiro,  Hudson,  P.  Palmer,  and 
I.  de  Pater,  "Radar  Imaging  of  Asteroid  4179  Toutatis,"  Bulletin  of  the  American  Astronomical  Society  25  (1993):  1126. 


ONE  STEP  BEYOND 


255 


Figure  41 

Thf.se  radar  images  of  Toutatis  repre- 
sent the  highest  resolution  then 
achieved  on  an  asteroid.  A  few  impact 
craters,  the  first  ever  documented,  are 
visible  in  the  images.  (Courtesy  of  Jet 
Propulsion  Laboratory,  photo  no. 
P41525) 


The  state-of-the-art  imaging  and  modeling  of  Castalia, 
Toutatis,  and  Geographos  are  feats  that  only  a  spacecraft 
flying  by  an  asteroid  could  match.  Although  no  probe 
deliberately  set  out  to  photograph  an  asteroid,  Galileo,  on 
its  voyage  to  Jupiter,  sent  back  the  first  spacecraft  images  of 
an  asteroid,  mainbelt  object  243  Gaspra,  on  29  October 
1991  from  a  distance  of  about  16,200  km.  Interestingly, 
Galileo  also  discovered  that  mainbelt  asteroid  951  Ida  had 
an  orbiting  satellite,  recently  named  Dactyl.103 

While  the  Toutatis  images  in  themselves  are  spectacu- 
lar witnesses  to  the  ability  of  radar  astronomy  to  solve  prob- 
lems left  unsolved  by  other  techniques,  radar  astronomy 
has  achieved  an  equally  great  degree  of  success  in  another 
problem-solving  area,  asteroid  orbits.  Determining  asteroid 
orbits  with  better  degrees  of  accuracy  and  predictive  relia- 
bility gained  higher  attention  as  scientists  and  the  general 
public  came  to  perceive  asteroids  as  an  ultimate  threat  to 
human  civilization  and  to  life  itself  on  Earth.  The  percep- 
tion grew  out  of  the  work  of  nuclear  physicist  and  Nobel 
laureate  Luis  Alvarez,  who  first  proposed  that  an  asteroid 
was  responsible  for  the  extinction  of  the  dinosaurs  some 
65  million  years  ago.  Since  then,  evidence  supporting  the 
theory  has  accumulated,  though  not  without  arguments 
and  evidence  questioning  the  theory. 

In  a  seminal  paper  published  in  Nature,  Clark 
Chapman  and  David  Morrison  argued  that  the  probability 
of  a  kilometer-size  asteroid  hitting  Earth  in  the  next  centu- 
ry was  1  in  5,000.  The  collision  would  have  a  global  effect, 
regardless  of  the  impact  site,  because  the  dust  blasted  into 
the  stratosphere  would  end  agriculture  for  several  years. 
Billions  of  people  would  starve  to  death.104 

In  order  to  detect  a  potentially  civilization-  and  life- 
threatening  asteroid,  the  scientific  community  proposed 
Spaceguard,  a  network  of  six  optical  telescopes  dedicated 
to  detecting  asteroids.  The  name  Spaceguard  came  from 
the  book  Rendezvous  with  Rama,  in  which  its  author  Arthur 
C.  Clarke  envisioned  an  asteroid  striking  Earth  in  northern 
Italy  in  the  year  2077.  In  response  to  the  impact's  devasta- 
tion, the  nations  of  Earth  formed  Project  Spaceguard. 

Creating  a  real  Spaceguard  has  not  been  so  straight- 
forward. After  asteroid  1989  FC  came  very  close  to  the 
Earth  in  1989,  the  American  Institute  of  Aeronautics  and 
Astronautics  recommended  to  the  House  Committee  on 
Science,  Space,  and  Technology  that  it  sponsor  studies  of 
asteroid  detection  and  defense.  Congress  then  commis- 
sioned NASA  in  1990  to  write  reports  on  those  subjects. 


103.  The  Spaceguard  Survey:  Report  of  the  NASA  International  Near- 
Earth-Object  Detection  Workshop  (Pasadena:  JPL,  25  January  1992),  p.  19; 
NASA  Press  Release  94-158,  20  September  1994,  Renzetti  materials. 

104.  Chapman  and  Morrison,  "Impacts  on  the  Earth  by  Asteroids 
and  Comets:  Assessing  the  Hazard,"  Nature  367  (1994):  33-40. 


256  TO  SEE  THE  UNSEEN 


NASA  already  had  considered  asteroid  detection  in  a  1981  workshop  held  in  Colorado, 
but  10  years  later  it  acted  in  response  to  a  Congressional  mandate.  The  NASA  1991  work- 
shop brought  together  24  asteroid  scientists  from  around  the  world,  including  radar 
astronomer  Steve  Ostro.105 

Although  Congress  has  not  yet  funded  Spaceguard,  a  battle  over  how  to  defend  the 
planet  against  a  "killer  asteroid"  rages.  The  recent  collision  of  Comet  Shoemaker-Levy 
with  Jupiter  has  driven  home  the  point  that  the  planets,  Earth  included,  are  susceptible 
to  potentially  life  threatening  impacts  from  comets  and  asteroids.  The  Spaceguard 
proposal  came  along  just  as  the  Department  of  Defense  was  seeking  post-Cold  War  appli- 
cations of  its  nuclear  arsenal.  The  deflection  of  a  menacing  asteroid  or  comet  with  a  series 
of  nuclear  explosions  is,  in  the  words  of  Carl  Sagan  and  Steve  Ostro,  "a  double-edged 
sword,"  which  if  wielded  by  the  wrong  hands  could  "introduce  a  new  category  of  danger 
that  dwarfs  that  posed  by  the  objects  themselves."  They  pointed  out  that  a  series  of 
nuclear  explosions  capable  of  thwarting  a  dangerous  asteroid  is  also  capable  of  diverting 
a  benign  asteroid  toward  Earth.106 

Regardless  of  the  means  used  to  defend  Earth  against  asteroid  hazards,  radar  is  suit- 
ed to  play  a  vital  role  in  identifying  potentially  hazardous  objects.  Radar  is  ffe  essential  tool 
for  astrometry  (position  and  movement);  it  can  determine  asteroid  orbits  with  greater 
accuracy  and  reliability  than  any  other  method.  After  the  detection  of  an  asteroid  and  the 
determination  of  its  orbit,  astronomers  extrapolate  the  orbit  into  the  future.  Without 
radar  precision  measurement,  the  uncertainty  of  that  extrapolation  increases  strikingly. 
The  role  of  radar  in  Spaceguard,  consequently,  is  as  the  primary,  post-discovery  ground- 
based  technique  for  refining  asteroid  orbits. 

After  Steve  Ostro's  experiences  with  the  errors  in  the  ephemerides  provided  for  1986 
DA  and  1986  JK,  he  and  fellow  JPL  employees  Don  Yeomans  and  Paul  Chodas,  who  were 
in  charge  of  calculating  ephemerides  for  space  missions,  including  those  for  a  potential 
future  asteroid  flyby  mission,  assessed  the  extent  to  which  radar  observations  could 
improve  the  accuracy  of  near-Earth  asteroid  ephemerides.  They  wanted  to  know  how  use- 
ful radar  ranging  was  for  refining  the  orbits  of  Earth-crossing  asteroids.  Could  radar 
improve  the  extrapolation  of  asteroid  orbits  into  the  future? 

They  studied  four  asteroids  with  different  histories  of  optical  and  radar  observations, 
1627  Ivar,  1986  DA,  1986  JK,  and  1982  DB.  The  radar  data  provided  only  a  modest 
absolute  improvement  for  Ivar,  which  had  a  long  history  of  optical  astrometric  data,  but 
rather  dramatic  reductions  in  the  future  ephemeris  uncertainties  of  asteroids  having  only 
short  optical-data  histories.  Those  improvements  were  impressive  ones,  to  three  orders  of 
magnitude. 

Ray  Jurgens,  who  had  been  observing  asteroids  at  Goldstone  since  the  1970s,  wrote 
a  proposal  to  fund  asteroid  emphemeris  work  at  JPL  and  persuaded  Don  Yeomans  and 
Paul  Chodas  to  help  in  the  analysis  of  asteroid  ephemerides.  As  Jurgens  became  over- 
whelmed by  research  and  the  rebuilding  of  the  Goldstone  radar,  Steve  Ostro  took  up  the 
tasks  of  strengthening  JPL's  asteroid  ephemeris  program  and  advocating  software  tools 
and  other  measures  for  improving  Goldstone's  capability  of  detecting  asteroids  and 
improving  the  accuracy  of  asteroid  orbit  predictions.107 


105.  The  Spaceguard  Survey,  pp.  1-3  and  49-52;  Cunningham,  pp.  1 13-1 16  and  141. 

106.  Sagan  and  Ostro,  "Dangers  of  Asteroid  Deflection,"  Nature  368  (1994):  501. 

107.  Ostro  25  May  1994;  Yeomans,  Ostro,  and  Paul  W.  Chodas,  "Radar  Astrometry  of  Near-Earth 
Asteroids,"  The  Astronomical  Journal  94  (1987):  189-  200;  Ostro,  The  Role  of  Ground-Based  Radar  in  Near-Earth 
Object  Hazard  Identification  and  Mitigation,"  in  Hazards  Due  to  Comets  and  Asteroids,  in  press,  p.  9.  For  a  summary 
of  asteroid  radar  astrometry,  see  Ostro,  Campbell,  Chandler,  Shapiro,  Hine,  Velez,  Jurgens,  Rosema,  Winkler, 
and  Yeomans,  "Asteroid  Radar  Astrometry,"  The  Astronomical  Journal  102  (1991):  1490-1502;  and  Yeomans, 
Chodas,  M.  S.  Keesey,  Ostro,  Chandler,  and  Shapiro,  "Asteroid  and  Comet  Orbits  using  Radar  Data,"  The 
Astronomical  Journal  103  (1992):  303-317. 


ONE  STEP  BEYOND  257 


The  astrometric  and  imaging  capabilities  of  radar  soon  will  combine  to  reformulate 
the  IAU  circular  that  announces  the  discovery  and  orbit  of  a  new  asteroid.  For  newly 
spotted  asteroids,  Ostro  has  a  vision  of  the  kind  of  IAU  circular  that  might  be  available 
before  the  end  of  the  century.  After  astronomers  discover  and  track  an  asteroid  optically 
for  a  few  nights  and  the  orbit  is  at  least  crudely  known,  an  IAU  circular  announces  the 
object's  existence.  A  few  days  later,  the  Arecibo  or  Goldstone  radar  observes  the  asteroid 
and  takes  range-Doppler  data,  refines  the  orbit,  and  images  the  object.  The  ephemeris  is 
updated  immediately.  Streamlined  software  transforms  the  image  data  into  a  three-dimen- 
sional model  of  the  asteroid,  then  produces  a  video  simulation  of  the  Sun-illuminated 
asteroid.  This  process  yields  a  computer  file  that  becomes  the  first  post-discovery  IAU 
circular:  a  finely-resolved  video  image  of  the  object,  as  if  made  by  a  flyby  spacecraft 
within  a  few  days  of  discovery.108  Here  was  the  future  of  asteroid  radar  research  and,  to  a 
dramatic  degree,  the  future  of  planetary  radar  astronomy,  as  well. 


108.    Ostro  25  May  1994. 


Conclusion 

W(h)ither  Planetary 
Radar  Astronomy? 

The  dynamic  interaction  between  epistemological  (instruments  and  techniques) 
concerns  and  the  kinds  of  problems  radar  astronomers  seek  to  solve,  which  we  have  seen 
driving  planetary  radar  astronomy  to  the  present,  also  in  all  likelihood  will  continue  to 
determine  its  future.  Both  new  instruments  and  techniques  will  furnish  the  means  for 
exploring  new  targets  and  for  resolving  problems,  especially  those  left  unresolved  or 
unsatisfactorily  resolved  by  optical  means. 

Planetary  radar  techniques  developed  recently  perhaps  hint  at  the  sources  of  future 
techniques.  Three  examples  are  John  Harmon's  non-repeating  code,  which  he  adapted 
from  Arecibo  ionospheric  research;  Dewey  Muhleman's  use  of  radio  astronomy  imaging 
and  arraying  techniques  at  the  VLA,  as  part  of  the  bistatic  Goldstone-VLA  radar;  and  the 
planetary  imaging  technique  developed  by  Scott  Hudson  and  Steve  Ostro.  The  Harmon 
and  Muhleman  techniques  reflect  the  continuing,  though  diminished,  influence  of  iono- 
spheric research  and  radio  astronomy  on  planetary  radar  astronomy. 

A  surprising  number  of  new  instruments  may  be  available,  too,  many  through  the 
grouping  of  either  the  Goldstone  or  Arecibo  antenna  in  tandem  with  a  radio  telescope  to 
form  a  bistatic  radar.  The  Goldstone-VLA  radar  appears  to  point  the  way  to  additional 
combinations  with  the  soon-to-be-completed  Green  Bank  radio  telescope,  or  perhaps  to 
the  Goldstone  X-band  radar  in  tandem  with  a  tracking  station  in  the  Soviet  Union. 
Already,  the  Russian  Yevpatoriya  tracking  station  has  made  bistatic  observations  of  the 
asteroid  Toutatis  in  conjunction  with  the  Effelsberg  radio  telescope,  though  without 
achieving  the  impressive  results  of  the  Arecibo  and  Goldstone  antennas.  Politics  and  fund- 
ing will  limit  what,  if  any,  future  bistatic  experiments  take  place  outside  the  United  States. 
Additional  bistatic  possibilities  in  the  United  States  include  the  JPL  Mars  Station  in  com- 
bination with  other  Goldstone  antennas,  as  well  as  an  Arecibo-Goldstone  link. 

The  bistatic  possibilities  are  not  limitless,  however;  not  inconsequential  institutional, 
political,  and  budgetary  obstacles  aside,  the  elementary  technological  need  for  compatible 
transmitting  and  receiving  frequencies  limits  many  bistatic  options.  Even  more  limited  is  the 
creation  of  new  radars.  Other  countries  continue  to  build  antennas,  such  as  the  Arecibo-size 
dish  planned  in  Brazil,  but  none  anticipate  a  radar  capability.  No  facility  dedicated  entirely 
to  planetary  radar  astronomy  ever  has  been  built;  nonetheless,  Steve  Ostro  believes  that  it  is 
time  to  build  one  in  order  to  study  asteroids.  The  cost  of  designing  and  building  such  a 
radar  observatory  would  approach  the  modest  level  budgeted  for  NASA's  Discovery  space 
missions.1  The  role  of  this  facility  in  the  Spaceguard  project  aside,  its  potential  scientific 
value  in  a  short  period  of  time  would  exceed  that  of  any  one  Discovery  flyby  of  an  asteroid. 
Time  will  tell  whether  this  worthwhile  and  economical  project  is  realized. 


1.        Ostro  25  May  1994. 

259 


260  TO  SEE  THE  UNSEEN 


These  are  all  possible  future  planetary  radar  instruments.  Nothing,  especially  not 
their  scientific  merit,  either  guarantees  or  favors  their  realization;  budgets,  not  science, 
will  determine  their  viability.  With  one  exception,  planetary  radar  astronomy  always  has 
subsisted  on  the  budgetary  margins,  either  by  design  (as  at  JPL)  or  by  fate  (as  at  Lincoln 
Laboratory) .  As  budgets  are  trimmed,  the  freedom  to  fund  bistatic  experiments  from  dis- 
cretionary funds  diminishes,  too.  The  only  exception  is  Arecibo,  where  a  five-year  contract 
stabilizes  the  research  budget,  although  within  the  shrinking  NASA  and  NSF  budgets.  If 
one  can  say  anything  about  the  future  of  planetary  radar  astronomy  with  certainty,  it  is 
that  the  future  is  at  the  upgraded  Arecibo  telescope. 

The  Arecibo  upgrade,  as  well  as  the  potentially  available  novel  instruments  and  tech- 
niques mentioned  above,  will  bring  new  research  targets  within  the  reach  of  radar 
astronomers.  Among  the  most  striking  new  targets  visible  to  the  upgraded  Arecibo  obser- 
vatory will  be  the  satellites  of  Jupiter,  lapetus,  Rhea,  Amalthea,  Dione,  and  Hyperion.  The 
detections  of  those  bodies  very  well  may  lead  to  radar  solving  new  scientific  problems.  In 
addition,  the  upgraded  Arecibo  telescope  will  be  able  to  map  Jupiter's  Galilean  moons  at 
much  higher  resolutions,  perhaps  down  to  100  kilometers,  and  uncover  fresh  facts  regard- 
ing lo  and  Saturn's  moon  Titan.2 

Planetary  radar  may  contribute  as  well  to  our  understanding  of  the  terrestrial  plan- 
ets through  analysis  of  their  polarization  ratios;  however,  the  greatest  amount  of  research 
activity  will  be  directed  toward  neither  the  terrestrial  planets  nor  the  systems  of  Jupiter 
and  Saturn,  but  the  asteroids.  The  space  in  which  Earth  turns  abounds  with  thousands  of 
asteroids.  The  largest,  a  kilometer  or  larger  in  diameter,  number  about  2,000,  while  those 
100  meters  or  more  in  diameter  number  150,000  or  more,  and  those  10  meters  and 
larger  amount  to  some  300,000,000.  These  are  estimates  of  the  asteroid  population;  the 
number  of  asteroids  actually  observed  increases  continually.  The  likelihood  that  one  of 
those  asteroids  might  approach  Earth  perilously  close  has  heightened  interest  in  them. 

In  many  ways,  then,  planetary  radar  astronomy  has  come  full  circle.  It  began  with  the 
study  of  large  populations  of  meteors,  and  the  observation  and  analysis  of  the  large  and 
varied  asteroid  population  is  carrying  it  into  the  future.  Forty  years  ago,  the  forte  of  radar 
lay  in  its  ability  to  determine  accurately  the  radiants  and  speed  of  meteors  and  to 
ascertain  unambiguously  that  they  orbited  around  the  Sun.  Today,  the  value  of  radar  is  its 
ability  to  fix  asteroid  orbits  with  an  accuracy  and  certainty  that  no  other  method  can 
match. 

Current  planetary  radar  techniques,  however,  can  do  much  more  with  asteroids  than 
the  earliest  radar  investigators  at  Jodrell  Bank  and  the  Canadian  National  Research 
Council  were  able  to  do  with  meteors  using  their  pioneering  techniques  and  far  less  sen- 
sitive radar  equipment.  Today's  planetary  radar  astronomers  can  characterize  asteroid 
composition,  size,  and  shape  and  can  provide  a  unique  imaging  ability.  The  ever-growing 
number  of  asteroid  targets,  combined  with  this  wide  range  of  epistemological  tools  and 
the  present  societal  interest  in  a  potential  "killer  asteroid,"  guarantees  that  the  future  of 
planetary  radar  astronomy  will  be  asteroid  research. 

W(h)ither  Planetary  Radar  Astronomy? 

Asteroid  literature  and  funding  have  grown  markedly  over  the  last  fifteen  years.  In 
the  past,  similar  rapid  growth  in  ionospheric  and  radio  astronomy  research  carried 
forward  planetary  radar  astronomy.  This  growth  has  not  yet  reached  radar  studies  of  aster- 
oids, however,  and  despite  the  expanding  observational  opportunities  created  by  asteroid 
studies,  the  number  of  radar  astronomers  probably  will  not  increase  significantly.  Steve 


2.        Ostro,  "Benefits  of  an  Upgraded  Arecibo  Observatory,"  pp.  238-239;  Ostro  25  May  1994;  Campbell 
8  December  1993. 


W(H)  ITHER  PLANETARY  RADAR  ASTRONOMY?  261 


Ostro  remains  the  sole  full-time  asteroid  radar  astronomer.  Once  the  upgraded  Arecibo 
radar  becomes  available,  the  number  of  radar  investigators  studying  asteroids  probably 
will  increase,  or  rather,  must  increase,  if  an  adequate  number  of  observational  opportuni- 
ties are  to  be  seized.  Already,  the  Arecibo  Observatory  has  hired  a  planetary  astronomer 
with  an  interest  in  asteroidsy3  who  will  also  take  part  in  radar  observations  of  asteroids. 
Don  Campbell  will  participate  in  those  observations,  as  too  may  Dick  Simpson  of  Stanford. 
The  growth  in  asteroid  science,  then,  may  shift  current  radar  researchers  into  the  field, 
rather  than  provide  a  basis  for  expanding  planetary  radar  astronomy. 

As  a  scientific  species,  planetary  radar  astronomers  have  tended  not  to  reproduce 
themselves.  Hiring  individuals  from  other  fields  yielded  planetary  radar  astronomers  in 
the  1960s  and  1970s,  but  none  in  the  last  15  years  with  the  exceptions  of  Marty  Slade  at 
JPL  and  the  recent  hire  at  Arecibo.  The  number  of  planetary  radar  astronomers  created 
through  paid  employment,  therefore,  may  remain  small  and  relatively  stable.  Being  small 
yet  may  have  its  advantages  in  a  future  certain  to  be  shaped  by  budget  cuts  in  NASA  and 
U.S.  scientific  research  in  general. 

The  other  traditional  career  path  into  radar  astronomy,  university  training,  may 
furnish  fresh  practitioners,  though.  Gordon  Pettengill  at  MIT  and  Don  Campbell  at 
Cornell  directed  many  radar  astronomy  dissertations,  although  certainly  not  all  of  those 
students  entered  the  field.  The  MIT-Cornell  axis  has  supplied  planetary  radar 
astronomers  since  the  1960s,  but  the  last  Ph.D.  to  enter  the  field  through  that  route  (Steve 
Ostro)  graduated  in  1978.  Moreover,  with  the  retirement  of  Pettengill  at  MIT  and  the 
approaching  retirement  of  Campbell  at  Cornell,  who  will  train  future  planetary  radar 
astronomers  at  Arecibo? 

Outside  of  MIT  and  Cornell,  only  Caltech  appears  equipped  or  willing  to  train  them. 
There,  Dewey  Muhleman  has  graduated  one  student,  Bryan  Butler,  in  1994,  who  did 
doctoral  research  in  radar  astronomy.  Although  interested  in  pursuing  radar  research, 
Butler  is  at  least  equally  excited  by  the  prospect  of  planetary  radio  studies  at  the  VIA, 
where  he  has  taken  a  position.  Muhleman  is  not  interested  in  training  additional  radar 
astronomers. 

In  contrast,  Steve  Ostro  at  JPL  teaches  a  course  on  radar  astronomy  at  Caltech.  That 
position  gives  him  the  ability  to  both  recruit  and  train  future  radar  astronomers.  The  key 
to  training  future  radar  astronomers  in  an  academic  setting  like  MIT  or  Cornell  remains 
the  master-disciple  relationship.  Replacing  Pettengill  and  Campbell,  then,  is  Ostro,  who  is 
in  a  unique  position  to  carry  the  MIT-Cornell  alliance  one  step  further  by  linking  Caltech, 
JPL,  and  Goldstone  to  it. 

Ostro,  a  graduate  of  MIT  who  conducted  his  doctoral  research  on  Cornell's  Arecibo 
instrument,  and  a  former  member  of  the  Cornell  faculty,  found  Ray  Jurgens  and  Marty 
Slade,  graduates  of  the  Cornell  and  MIT  programs,  respectively,  when  he  began  work  at 
JPL.  Ostro's  arrival  at  JPL  signalled  a  joining  of  the  JPL  and  MIT-Cornell  research  groups. 
His  opportunity  to  teach  at  Caltech  and  recruit  radar  astronomers,  coming  near  the 
retirements  of  Pettengill  and  Campbell,  assures  the  continuation  of  the  master-disciple 
relationship  as  the  source  of  future  radar  astronomers,  but  within  a  larger  institutional 
(MIT,  Cornell,  CaltectvJPL)  and  instrumental  complex  that  joins  the  Arecibo  and 
Goldstone  radars.  The  centering  of  Ostro  within  that  complex  also  positions  him  to  direct 
the  future  of  radar  astronomy. 

Like  the  number  of  practitioners,  the  radar  astronomy  literature  will  remain  at  a  low 
level  as  a  result  of  both  the  small  number  of  researchers  and  the  nature  of  the  science 
reported  in  those  publications.  The  discoveries  to  be  made  on  the  terrestrial  planets  and 
the  moons  of  Jupiter  and  Saturn  will  not  generate  a  substantial  number  of  articles, 
because  those  discoveries  likely  will  not  merit  that  level  of  scientific  attention.  The  results 


3.        Harmon  15  March  1994. 


262  TO  SEE  THE  UNSEEN 


of  asteroid  research,  moreover,  will  be  described  in  articles  that  discuss  the  characteristics 
of  a  substantial  population  of  asteroids  and  not  the  properties  of  just  one  or  two  asteroids. 
Consequently,  the  number  of  asteroid-related  publications  will  remain  limited. 

Indeed,  virtually  the  entire  history  of  planetary  radar  astronomy  has  been  one  of 
limits.  The  number  of  practitioners  has  been  limited,  if  not  declining.  As  we  saw,  after  the 
initial  "explosion"  of  planetary  radar  activity  in  the  early  1960s,  as  measured  by  the 
number  of  experimenters,  publications,  and  instruments,  the  field  of  planetary  radar 
astronomy  assumed  the  manpower  and  publication  dimensions  of  Little  Science.  After 
further  shrinking  during  the  1970s,  leaving  a  handful  of  researchers  utilizing  a  single 
radar  instrument  in  1980,  planetary  radar  astronomy  stabilized  at  this  lower  level  (the 
Arecibo  radar  being  down  for  the  duration  of  the  upgrade) .  The  circumscribed  number 
of  opportunities  to  train  future  radar  practitioners  in  academia,  as  well  as  retirements 
(most  current  practitioners  are  at  or  near  retirement  age),  will  keep  manpower  levels  low. 


Little  Science,  Big  Science 


The  practice  of  planetary  radar  astronomy  as  Little  Science  in  the  instrumental  and 
institutional  context  of  Big  Science  will  likely  continue  into  the  future.  A  number  of 
factors  integral  to  the  field  have  confined  planetary  radar  astronomy  to  its  existence  as 
Little  Science.  To  begin  with,  the  field  generally  has  operated  at  the  limits  of  the  technol- 
ogy (the  instrument  hardware).  As  soon  as  an  instrument  became  available,  radar 
astronomers  sought  to  discover  what  new  targets  it  could  detect.  Once  the  farthest  target 
was  reached,  and  the  spatial  limits  of  research  defined,  radar  astronomers  had  insufficient 
sensitivity  to  achieve  more  than  a  detection.  Imaging  planetary  surfaces  always  involved 
pushing  the  instrument's  signal-to-noise  ratio  and  resolution  capability  to  the  limit.  These 
restrictions  in  turn  prompted  radar  astronomers  to  continually  press  for  hardware  modi- 
fications that  provided  incremental  increases  in  sensitivity.  In  the  end,  though,  what  could 
be  done  was  limited  by  the  capability  of  the  instrument. 

Another  growth-limiting  factor  inherent  in  planetary  radar  astronomy  is  the  avail- 
ability of  targets,  a  factor  intimately  linked  to  instrument  capability.  The  planets  and  their 
moons  cannot  be  detected  unless  they  are  within  radar  range.  The  sensitivity  limits  of 
planetary  radars,  such  as  the  Arecibo  telescope,  prevent  investigators  from  observing 
targets  except  when  they  approach  Earth.  At  other  points  in  their  orbits  around  the  Sun, 
they  are  too  far  away  for  radars  to  detect  them.  Thus,  Venus  is  observed  at  inferior 
conjunction  and  Mars  at  opposition. 

A  related  problem  is  that  of  declination.  Although  most  planets  rotate  around  the 
Sun  more  or  less  in  the  same  plane,  called  the  ecliptic,  they  are  not  visible  in  the  sky  at  all 
times  because  of  the  Earth's  motion  about  its  own  axis.  A  further  complicating  factor  is 
the  ability  of  the  radar  antenna  to  "see"  a  portion  or  all  of  the  visible  sky,  that  is,  the 
so-called  declination  window  of  the  antenna.  The  declination  window  of  the  Goldstone 
DSS-14  dish  runs  from  40°  South  to  80°  North,  while  the  Arecibo  telescope  is  limited  to 
solar  system  objects  that  pass  within  the  far  narrower  band  from  40°  North  to  just  below 
the  equator.4 

The  combination  of  declination  window  and  radar  sensitivity  restricts  observational 
opportunities,  so  that  planetary  research  demands  only  about  five  percent  of  total  anten- 
na time.  The  finite  number  of  planetary  targets  and  the  narrow  observational  windows 
also  tend  to  limit  the  number  of  radar  researchers.  Thus,  the  tendency  at  Arecibo  was  to 
establish  a  given  target  as  the  terrain  or  turf  of  a  particular  researcher.  The  number  of 
radar  investigators  at  JPL  was  always  too  small  for  such  a  division  of  targets,  although 


4.        Renzetti,  Thompson,  and  Slade,  "Relative  Planetary  Radar  Sensitivities:  Arecibo  and  Goldstone," 
TDA  Progress  Report  no.  42-94  (Pasadena:  JPL,  April-June  1988):  292. 


W(H)  ITHER  PLANETARY  RADAR  ASTRONOMY?  263 


during  the  1970s  Ray  Jurgens  "specialized"  in  Venus  and  asteroids  and  George  Downs  in 
Mars,  with  Dick  Goldstein  continuing  to  do  a  little  of  everything. 

The  considerable  and  expanding  number  of  known  asteroids  is  too  large  for  a  single 
investigator.  This  will  be  especially  true  in  the  near  future,  once  asteroid  detection  relies 
on  CCD  imaging  and  the  Arecibo  upgrade  reaches  completion.  Then  joining  Ostro  in 
radar  observations  of  asteroids  (many  asteroid  scientists  hope)  will  be  virtually  all  mem- 
bers of  the  small  club  of  radar  astronomy  practitioners.  Again,  the  expanded  program  of 
asteroid  radar  research  that  will  take  place  throughout  the  remainder  of  this  decade  will 
not  lead  to  a  transformation  of  planetary  radar  astronomy  into  Big  Science. 

Planetary  radar  astronomy  has  been  and  likely  will  remain  Little  Science  embedded 
in  the  matrix  of  Big  Science.  John  Krige's  study  of  British  nuclear  physics  research  in  the 
period  right  after  World  War  II  provides  a  different  case  of  Little  Science  being  conduct- 
ed with  Big  Science  instruments.  One  can  find  another  parallel  example  in  the  telegraph 
networks  of  the  nineteenth-century  United  States. 

The  Western  Union  telegraph  company,  formed  by  the  merger  of  several  separate 
companies,  absorbed  both  of  its  principal  rivals  in  1866  to  become  one  of  the  nation's 
largest  companies  and  thereby  created  the  largest  electrical  communication  network  in 
the  world.  While  not  Big  Science,  this  was  Big  Business  and  Big  Technology.  By  the  very 
nature  of  their  position  in  the  company,  telegraph  operators  had  access  to  the  large-scale 
technological  laboratory  formed  by  the  telegraph  lines.  Just  as  access  to  technology  led  to 
the  emergence  of  planetary  radar  astronomy,  so  access  to  the  telegraph  network  led  these 
operators  to  perform  electrical  experiments  on  the  lines.  Out  of  those  experiments  came 
numerous  inventions,  many  of  which  were  patented.5 

It  is  not  going  too  far  to  draw  this  parallel  between  Little  Science  (planetary  radar 
astronomy)  and  Little  Technology  (telegraph  inventors),  for  several  reasons.  For  one, 
most  radar  astronomers  were  trained  as  electrical  engineers,  not  scientists.  Also,  radar 
astronomy  was  a  science  driven  by  technology,  namely,  the  availability  of  radars  capable  of 
planetary  exploration.  It  was  through  these  instruments  and  their  associated  techniques 
of  analysis,  not  through  direct  sensory  observation,  that  radar  astronomers  conducted 
their  experiments.  They  analyzed  not  sensory  experience,  but  wave  patterns  of  electro- 
magnetic signals  which  analysis  by  computer  software  made  "visible."  Thus,  not  only  were 
the  instrumentation  and  techniques  of  radar  astronomy  dependent  on  technology,  but  so 
was  the  very  content  of  the  science. 

Planetary  radar  astronomy  historically  has  remained  at  the  intersection  of  science 
and  engineering.  Attendance  of  radar  astronomers  at  both  LAU  and  URSI  meetings  dur- 
ing the  1960s  reflected  the  dichotomous  nature  of  radar  astronomy,  perched  between 
radio  engineering  (URSI)  and  astronomical  science  (IAU).  The  dichotomy  arose  from 
the  fact  that  radar  astronomy  is  a  set  of  techniques  (engineering)  used  to  generate  data 
whose  interpretation  yields  answers  to  scientific  (planetary  astronomy  and  geology)  ques- 
tions. Also  as  a  result  of  this  dichotomy,  planetary  radar  astronomy  concerns  itself  with  two 
different  but  related  sets  of  problems  (in  the  Kuhnian  sense  discussed  in  Chapter  Five). 
One  set  of  problems  is  epistemological,  that  is,  it  deals  with  how  radar  astronomers  know 
what  they  know  and  relates  to  the  radar  characteristics  of  the  planets,  such  as  surface  scat- 
tering mechanisms,  dielectric  constants,  and  radar  albedos;  these  problems  arise  out  of 


5.  For  a  careful  scholarly  study  of  telegraph  operators  as  inventors,  see  Paul  Israel,  From  Machine  Shop 
to  Industrial  Laboratory:  Telegraphy  and  the  Changing  Context  of  American  Invention,  1830-1920  (Baltimore:  Johns 
Hopkins  University  Press,  1992),  which  is  based  on  the  dissertation  of  the  same  title,  Ph.D.  diss.,  Rutgers 
University,  1989.  For  a  discussion  of  the  role  of  the  entrepreneur  in  channeling  the  resources  of  large-scale 
organizations,  specifically,  the  introduction  of  radio  and  radio  research  within  the  French  military  by  Gustave 
Ferric,  see  A.  Butrica,  The  Militarization  of  Technology  in  France:  The  Case  of  Electrotechnics,  1845-1914," 
paper  read  at  the  joint  meeting  of  the  American  Historical  Association  and  the  History  of  Science  Society, 
Cincinnati,  December  1988. 


264  TO  SEE  THE  UNSEEN 


the  engineering  side  of  radar  astronomy.  A  second  set  of  problems,  such  as  planetary 
orbits  and  spin  rates,  arises  out  of  the  science  side  of  the  field. 

The  rooting  of  Little  Science  (of  Little  Technology)  within  large  technological  sys- 
tems, such  as  the  Western  Union  telegraph  network  or  the  Deep  Space  Network,  suggests 
that  it  may  be  in  the  nature  of  large-scale  "technosocial  networks"  or  "systems"  (to  borrow 
the  terminology  of  the  social  construction  of  technology  mentioned  in  the  Introduction) 
to  sustain  Little  Science  (or  Little  Technology) .  Large  technological  systems  form  a  uni- 
fied set  of  relations  among  individuals,  objects,  and  ideas.  As  tightly  "constructed"  as  these 
technosocial  networks  may  be,  the  magnitude  of  the  resources  they  encompass  is  of  a  suf- 
ficient extent  to  allow  small-scale  entrepreneurs  (be  they  scientists,  engineers,  inventors) 
within  the  system  to  "socially  construct"  smaller  technosocial  networks  within  the  larger. 

Without  the  larger  technosocial  network,  then,  the  smaller  network  is  unthinkable. 
Planetary  radar  astronomy  simply  would  not  have  existed  without  the  enormous,  power- 
ful, highly  sensitive  radars  on  which  the  experiments  were  conducted  and  which  were 
called  into  existence  by  the  demands  of  the  Cold  War  and  Big  Science.  Another  requisite, 
of  course,  was  the  radar  experimenters  themselves.  The  linking  of  research  groups  at  MIT 
(Lincoln  Laboratory),  Cornell  University,  and  (most  recently)  JPL  (Caltech)  has  provid- 
ed a  means  by  which  the  Little  Science  planted  in  the  interstices  of  large  technological  sys- 
tems can  perpetuate  itself  despite  declining  resources  and  limits  to  growth.  For  example, 
as  planetary  radar  activity  ceased  at  Haystack,  it  continued  at  the  Arecibo  Observatory. 
Given  the  symbiotic  relationship  between  Big  Science  and  the  Little  Science  which 
depends  on  it,  as  well  as  the  nature  of  that  dependency,  funding  cutbacks  intended  to 
reduce  Big  Science  also  will  diminish,  or  perhaps  even  eliminate,  Little  Science.  Future 
research  will  have  to  determine  how  vast  (and  by  what  standard  (s)  that  vastness  is  mea- 
sured) a  technosocial  network  must  be  in  order  to  sustain  Little  Science. 

The  technological  dependence  of  radar  astronomy,  and  the  availability  of  that  tech- 
nology within  large  technological  systems,  thus  accounts  for  the  emergence  of  radar 
astronomy  within  Big  Science  settings.  The  technological  dependence  of  planetary  radar 
astronomy,  however,  does  not  explain  its  utilitarian  proclivity,  namely,  the  tendency  of 
radar  astronomers  to  justify  their  research  by  its  usefulness  to  space  exploration.  Nor  does 
the  training  of  most  radar  astronomers  as  electrical  engineers,  who  must  think  in  both 
theoretical  and  practical  terms  at  the  same  time,  illuminate  that  tendency.  The  rise  of 
radar  astronomy  concurrently  with  the  creation  and  rapid  growth  of  NASA  was  perhaps 
not  coincidental. 

Although  the  space  agency  did  not  build  research  instruments  outside  NASA  labo- 
ratories during  the  1960s,  its  very  existence  from  1958  suggested  the  future  availability  of 
funds  for  instruments  and  research  activity.  The  Endicott  House  Conference  reflected 
those  funding  hopes.  After  1970,  when  NASA  funding  became  a  reality,  radar  astronomy 
quickly  began  participating  in  NASA  space  missions,  such  as  Viking,  until  radar  astrono- 
my became  a  space  project,  the  Magellan  radar  mission  to  Venus.  This  close  relationship  to 
NASA  space  missions  certainly  amplified  whatever  utilitarian  bent  radar  astronomy 
already  had. 

This  utilitarian  bent  also  arose  from  the  very  nature  of  conducting  Little  Science 
within  the  context  of  Big  Science.  Doing  Little  Science  requires  that  scientists  constantly 
defend  the  pragmatic  value  of  their  research.  A  good  example  is  radar  astronomy  at  JPL; 
it  lived  off  the  budgetary  margins  of  NASA  space  missions  until  the  1980s.  Because  obtain- 
ing antenna  time  depended  on  securing  the  approval  of  a  NASA  mission,  radar 
astronomers  had  to  argue  the  value  of  their  research  on  practical,  mission-oriented  terms. 


W(H)  ITHER  PLANETARY  RADAR  ASTRONOMY?  265 


In  contrast,  obtaining  antenna  time  at  the  Arecibo  Observatory  depended  on  the  sci- 
entific value  of  the  radar  experiment;  its  value  to  NASA  was  far  less  important,  although 
research  directly  related  to  NASA  space  missions  was  carried  out  there.  The  primary  dif- 
ference between  the  JPL  and  Arecibo  facilities  was  the  official  recognition  granted  radar 
astronomy  at  Arecibo  from  the  start.  The  Arecibo  telescope  always  had  radar  astronomy 
as  one  of  its  prime  research  objectives,  while  the  JPL  Goldstone  antenna  served  mainly  to 
track  NASA  launches,  not  conduct  scientific  experiments.  NASA  recognition  for  the  sci- 
entific value  of  the  Goldstone  radar  dish  has  yet  to  be  realized  fully  or  even  established  on 
a  permanent  foundation,  though  some  preliminary  steps  have  been  taken. 

We  can  conclude  briefly  the  following  about  planetary  radar  astronomy.  After  a  brief 
initial  burst  of  activity,  radar  astronomy  quickly  developed  the  characteristics  of  Little 
Science  in  terms  of  manpower,  instruments,  and  published  literature.  The  field  continued 
to  shrink  throughout  the  1970s,  reached  a  low  plateau  of  activity  around  1980,  then  rose 
slightly  in  the  middle  1980s,  as  the  Goldstone  radar  once  again  became  available  for 
research. 

A  number  of  factors  kept  planetary  radar  astronomy  a  Little  Science.  Radar  sensitiv- 
ity and  target  visibility  within  the  declination  window  limited  observational  opportunities. 
The  shortage  of  observational  opportunities  in  turn  restricted  the  number  of  investigators 
who  could  pursue  radar  astronomy  on  a  full-time  basis.  Close  ties  to  NASA  space  projects 
intensified  radar  astronomy's  utilitarian  tendency.  The  need  to  justify  Little  Science  with- 
in a  Big  Science  setting  played  at  least  an  equal  part  in  shaping  that  tendency.  The  case  of 
the  Arecibo  Observatory,  though,  demonstrates  the  importance  of  securing  institutional 
recognition  for  the  conduct  of  Little  Science  from  the  outset.  Finally,  the  subsistence  of 
Little  Science  within  Big  Science  niches  and  their  symbiotic  relationship  may  be  a  func- 
tion of  large-scale  technological  systems,  whether  they  be  the  Western  Union  telegraph 
network  of  the  nineteenth  century  or  the  big  dishes  of  twentieth-century  radio  astronomy 
and  space  communications. 


Planetary  Radar  Astronomy 
Publications 

At  the  beginning  of  this  project,  a  bibliography  of  radar  astronomy  literature,  con- 
sisting of  384  items  arranged  chronologically  by  year  of  publication  and  alphabetically  by 
author  within  each  year,  was  constructed  from  a  search  of  the  NASA  STI  Database  (aero- 
nautics and  space)  and  a  published  bibliography,  Jean  E.  Britton  and  Paul  E.  Green,  Jr., 
Radar  Astronomy  (Cambridge:  MIT  Lincoln  Laboratory  Library,  1962),  which  Mr.  Green 
generously  made  available.  The  NASA  STI  Database  search  alone  resulted  in  a  printout  of 
589  items  published  since  1963.  To  this  initial  bibliography  were  added  additional  publi- 
cations uncovered  in  the  researching  and  writing  of  this  book. 

The  initial  bibliography,  with  fewer  than  400  entries,  illustrated  the  diminutive  char- 
acter of  planetary  radar  astronomy.  In  comparison,  the  radio  astronomy  literature  of  just 
the  past  two  decades  measures  in  the  thousands.  Because  the  extent,  as  well  as  the  devel- 
opment, of  the  literature  might  help  to  characterize  the  progress  of  planetary  radar 
astronomy  over  several  decades,  the  bibliography  was  pruned  and  grafted  in  such  a  way  as 
to  reflect  the  published  literature.  Dissertations  were  missing  from  the  bibliography,  while 
publications  by  foreign  researchers  and  abstracts  abounded. 

A  number  of  rules  were  followed  in  including  and  excluding  publications.  Internal 
reports  were  omitted;  these  are  not  intended  for  consumption  by  the  general  public  or 
the  scientific  community.  Only  works  by  American  practitioners  were  included;  British 
and  Soviet  titles  were  excluded.  Planetary  radar  astronomy  was  defined  more  strictly  than 
in  the  text;  solar,  lunar,  meteor,  auroral,  and  Earth  radar  studies;  and  synthetic  radar  aper- 
ture research  were  left  out,  because  they  are  specializations  unto  themselves.  Also  exclud- 
ed were  items  dealing  with  hardware,  instruments,  or  techniques  and  those  providing 
interpretations  of  radar  results  by  individuals  outside  the  field.  For  example,  an  article  on 
the  interpretation  of  radar  topographic  data,  whose  first  author  was  a  planetary  geologist, 
was  left  out;  however,  if  the  first  author  was  a  radar  astronomer,  the  article  was  added. 
Finally,  abstracts  were  excluded,  dissertations  included. 

The  resulting  planetary  radar  literature,  spanning  the  period  from  1958  to  1994 
inclusively,  amounted  to  272  entries,  or  an  annual  average  of  about  seven.  Only  twice  did 
15  or  more  items  appear  in  a  single  year.  A  line  chart  (Table  9)  showing  the  annual  dis- 
tribution of  planetary  radar  publications  indicates  the  explosion  of  radar  astronomy  activ- 
ity during  the  1960s.  The  remainder  of  the  chart  suggests  the  technological  dependence 
of  radar  astronomy.  A  second  spurt  of  growth  appears  following  1975,  when  the  Arecibo 
Observatory  S-band  radar  first  became  available,  and  a  third  spurt  occurred  around  1990, 
just  after  the  Voyager  upgrade  of  the  Goldstone  radar. 

When  the  annual  publication  numbers  are  grouped  by  5-year  intervals,  the  sharp 
peaks  and  valleys  of  the  annual  chart  are  smoothed  out  and  a  new  trend  emerges  (Table 
10) .  The  volatile  growth  of  the  1960s  remains,  but  what  appeared  to  be  seesaw-like  growth 
around  1975  and  1990  disappears.  Instead,  a  dip  replaces  the  growth  following  1975,  and 
the  literature  reaches  a  plateau  of  activity.  This  plateau  suggests  that  since  1980  the  field 
has  reached  the  limits  to  its  growth. 


267 


268 


TO  SEE  THE  UNSEEN 


Table  9 
Planetary  Radar  Astronomy  Publications 


Annual  Distribution 


Table  10 
Planetary  Radar  Astronomy  Publications 


60   -, 


1990 


By  5-Year  Interval 


A  Note  on  Sources 

For  the  early  history  of  radar  astronomy,  a  number  of  archival  sources  were  consult- 
ed. The  Historical  Archives,  U.S.  Army  Communications-Electronics  Command,  Ft. 
Monmouth,  NJ,  have  several  boxes  of  material  on  the  pioneering  lunar  radar  work  of  John 
DeWitt,  but  no  such  archival  material  was  found  on  the  radar  work  of  Zoltan  Bay,  with  the 
exception  of  the  documents  in  the  possession  of  his  widow.  The  Naval  Research 
Laboratory  Historical  Reference  Collection,  Office  of  the  Historian,  was  not  a  ready 
source  of  information  on  the  lunar  radar  work  carried  out  there;  much  of  the 
Laboratory's  records  remain  classified.  In  contrast,  the  archives  of  Jodrell  Bank,  housed 
at  the  University  of  Manchester,  contain  a  wealth  of  open  information  on  radar  astrono- 
my, and  a  computerized  index  is  available. 

Radar  research  on  meteors  began  at  Stanford  University  as  early  as  the  1950s.  The 
university  archives,  however,  hold  no  records  relevant  to  either  the  early  or  later  work 
done  there.  The  only  records  available  are  those  of  the  Stanford  Center  for  Radar 
Astronomy,  which  for  the  most  part  consist  of  a  large  collection  of  offprints  that  document 
the  Center's  research  results.  Von  Eshleman,  the  Center's  director,  was  a  far  more  impor- 
tant source  of  documentation. 

Records  relating  to  radar  astronomy  at  the  Arecibo  Observatory  are  located  for  the 
most  part  in  filing  cabinets  at  the  National  Astronomy  and  Ionosphere  Center  (NAIC) 
offices  on  the  Cornell  University  campus  and  are  not  normally  open  to  researchers. 
Among  the  most  useful  of  those  records  are  the  quarterly  reports  to  the  NSF  and  copies 
of  Center  for  Radiophysics  and  Space  Research  (CRSR)  research  publications.  The  NAIC 
library  retains  copies  of  dissertations  completed  at  the  Arecibo  Observatory.  The  CRSR, 
located  in  the  same  building,  has  the  earlier  ARPA  reports.  The  library  of  the  Arecibo 
Observatory  contains  additional  reports,  program  plans,  dissertations,  and  other  materi- 
als. The  minutes  of  the  open  sessions  of  the  National  Science  Board  were  helpful,  as  were 
the  archives  of  the  AFCRL  at  Phillips  Laboratory,  Hanscom  AFB,  although  the  amount  of 
documentation  at  each  place  was  lean. 

In  contrast,  an  overwhelming  abundance  of  documents  relating  to  the  history  of 
radar  astronomy  were  found  at  MIT  and  Lincoln  Laboratory.  The  Lincoln  Laboratory 
Library  Archives  contain  both  documents  and  photographs,  while  the  MIT  Institute 
Archives  and  Special  Collections  is  a  treasure  trove  of  documentation,  including  NEROC 
materials.  The  Pusey  Archives,  Harvard  University,  hold  additional  NEROC  documents.  In 
general,  the  MIT,  Lincoln  Laboratory,  and  Harvard  materials  are  available  to  researchers; 
examination  of  the  Pusey  papers  requires  written  permisoion  from  the  director  of  the 
Harvard  College  Observatory,  though.  A  small  building  near  the  Haystack  Observatory 
named  for  its  first  director,  Paul  Sebring,  holds  logbooks  and  other  records  relating  to  the 
Millstone  and  Haystack  facilities,  but  those  records  normally  are  closed  to  researchers. 

Documents  relating  to  radar  astronomy  at  Goldstone  can  be  found  in  the  Jet 
Propulsion  Laboratory  archives.  Magellan  materials,  although  somewhat  organized,  have 
not  been  fully  integrated  into  that  portion  of  the  archives  open  to  researchers.  Also,  a 
smaller  batch  of  materials,  initially  removed  from  document  storage  for  a  history  of  the 
Deep  Space  Network  and  slated  for  integration  into  the  JPL  archives  as  the  Peter  Lyman 
Collection,  was  especially  useful. 


269 


270  TO  SEE  THE  UNSEEN 


For  further  documentation  of  the  NEROC  saga,  see  the  Archives  of  the  Smithsonian 
Institution,  in  particular,  the  Office  of  the  Secretary  and  the  Under  Secretary  collections. 
The  papers  of  William  Brunk,  at  the  NASA  History  Office,  and  the  Historian's  File,  at  the 
National  Science  Foundation,  held  valuable  materials  on  the  first  upgrading  of  the 
Arecibo  facility.  The  library  of  the  National  Science  Foundation  and  the  archives  of  the 
National  Academy  of  Sciences  also  held  useful  secondary  sources. 

A  significant  number  of  documents  relating  to  radar  astronomy  are  in  the  possession 
of  individuals  who  made  the  materials  available  exclusively  for  the  writing  of  this  history. 
Until  the  day  arrives  when  (and  if)  those  documents  are  entrusted  to  an  archive,  the 
above  noted  depositories  will  be  the  chief  source  of  documentation  for  the  history  of 
radar  astronomy.  In  addition,  materials  gathered  or  created  in  the  process  of  writing  this 
history,  including  photocopied  documents,  notes,  and  oral  history  transcripts,  have  been 
deposited  with  the  NASA  History  Office  for  consultation  by  researchers. 


Oral  History  Interviews 


Because  planetary  radar  astronomy  is  a  relatively  new  field,  virtually  all  of  the 
founders,  even  those  active  during  the  1940s,  and  practitioners  are  still  with  us.  This  pro- 
ject has  been  fortunate,  too,  in  that  with  only  one  exception  everyone  approached  agreed 
to  be  interviewed.  Two-thirds  of  the  interviews  were  taped  and  transcribed.  The  author 
alone  conducted  all  interviews  with  the  exceptions  of  Schaber,  Soderblum,  and 
Shoemaker,  which  were  carried  out  jointly  with  Joseph  Tatarewicz,  as  noted  below.  Copies 
of  all  transcripts  are  held  by  the  NASA  History  Office  and  the  JPL  Archives;  interviews  of 
individuals  formerly  with  MIT  Lincoln  Laboratory  are  also  maintained  at  their  archives. 

Those  interviews  not  transcribed,  as  well  as  the  telephone  interviews,  consist  of 
either  notes  or  tapes  on  file  at  the  NASA  History  Office  and  the  JPL  Archives.  Additional 
interviews,  carried  out  by  Jose  Alonzo  and  housed  at  the  JPL  Archives,  were  consulted; 
they  are  listed  below,  too. 


Interviews 


Transcribed  Interviews 


Interviewee 

Date  of  Interview 

Place  of  Interview 

Donald  B.  Campbell 

7  December  1993 
8  December  1993 

Cornell  University 

9  December  1993 

Clark  R.  Chapman 

28  June  1994 

Flagstaff,  Arizona 

George  Downs 

4  October  1994 

Lincoln  Laboratory 

Rolf  B.  Dyce 

22  November  1994 

Aguadilla,  Puerto  Rico 

Von  R.  Eshleman 

9  May  1994 

Stanford  University 

John  V.  Evans 

9  September  1993 

NASA  Headquarters 

Thomas  Gold 

14  December  1993 

Ithaca,  New  York 

Richard  M.  Goldstein 

14  September  1993 

JPL 

William  E.  Gordon 

28  November  1994 

Rice  University 

Paul  E.  Green,  Jr. 

20  September  1993 

Hawthorne,  New  York 

John  K.  Harmon 

15  March  1994 

Arecibo  Observatory 

Raymond  F.  Jurgens 

23  May  1994 

JPL 

Sir  Bernard  Lovell 

11  January  1994 

Jodrell  Bank 

Duane  O.  Malik-man 

19  May  1994 
27  May  1994 

California  Institute  of 
Technology 

Steven  J.  Ostro 

18  May  1994 
25  May  1994 

JPL 

Gordon  H.  Pettengill 

28  September  1993 
29  September  1993 
4  May  1994 

MIT 

Robert  Price 

27  September  1993 

Lexington,  Mass. 

Alan  E.  E.  Rogers 

5  May  1994 

Haystack  Observatory 

Irwin  I.  Shapiro 

30  September  1993 
1  October  1993 
4  May  1994 

Harvard-Smithsonian 
Center  for  Astrophysics 

Richard  A.  Simpson 

10  May  1994 

Stanford  University 

Martin  A.  Slade 

24  May  1994 

JPL 

William  Boyd  Smith 

29  September  1993 

Cambridge,  Mass. 

271 


272 


TO  SEE  THE  UNSEEN 


Thomas  W.  Thompson 
G.  Leonard  Tyler 
Herbert  G.  Weiss 


29  November  1994 

10  May  1994 

29  September  1993 


JPL 

Stanford  University 
Cambridge,  Mass. 


Untranscribed  Interviews 
(Excluding  Telephone  Interviews) 


Interviewee 
Donald  B.  Campbell 
Robert  Dickman 
Peter  G.  Ford 
Richard  M.  Goldstein 
Alice  Hine 
Richard  P.  Ingalls 
Raymond  F.  Jurgens 

Duane  O.  Muhleman 
Steven  J.  Ostro 
John  E.  B.  Ponsonby 
Martin  A.  Slade 
Robertson  Stevens 


Interviewee 

Roland  L.  Carpenter 
Robert  Desourdis 
John  H.  DeWitt,  Jr. 
Von  R.  Eshleman 
Daniel  H.  Herman 
R.  Scott  Hudson 
Benjamin  Nichols 
Eberhardt  Rechtin 


Date  of  Interview 

Place  of  Interview 

10  March  1993 

Arecibo  Observatory 

2  December  1992 

NSF 

3  October  1994 

MIT 

7  April  1993 

JPL 

12  March  1993 

Arecibo  Observatory 

5  May  1994 

Haystack  Observatory 

26  January  1993 
28  April  1993 

JPL 

8  April  1993 

Caltech 

1  April  1993 

JPL 

1  1  January  1994 

Jodrell  Bank 

26  January  1993 

JPL 

14  September  1993 

JPL 

Telephone  Interviews 

Date  of  Interview 
14  September  1993 
22  September  1994 
14  June  1993 
26 January  1993 

20  May  1994 

21  November  1994 
14  December  1993 
13  September  1993 


A  NOTE  ON  SOURCES  AND  ABBREVIATIONS 


273 


Paul  Reichley 
Donald  Spector 
E.  Myles  Standish 


19  May  1994 

22  September  1994 

20  May  1994 


Interviewee 

Gerald  Schaber 
Eugene  M.  Shoemaker 
Laurence  A.  Soderblom 


Interviews  with 
Joseph  N.  Tatarewicz 

Date  of  Interview 


27  June  1994 
30  June  1994 
26  June  1994 


Place  of  Interview 

Flagstaff,  Arizona 
Flagstaff,  Arizona 
Flagstaff,  Arizona 


Interviews  Conducted  by  Jose  Alonzo 


Interviewee 


Richard  M.  Goldstein 


Nicholas  A.  Renzetti 


Date  of  Interview 

19  September  1991 
22  July  1992 

16  April  1992 

17  April  1992 

20  February  1992 


Place  of  Interview 
JPL 

JPL 


Technical  Essay 
Planetary  Radar  Astronomy      ; 

The  basic  technology  of  planetary  radar  astronomy  is,  as  the  name  implies,  radar. 
Radar  is  an  acronym  for  RAdio  Detection  And  Ranging.  U.S.  Naval  officers  Lieutenant 
Commanders  F.  R.  Furth  and  S.  M.  Tucker  devised  the  acronym  in  1940.  By  1943,  all  allied 
forces  had  adopted  the  name,  though  it  remained  a  classified  term  until  after  the  second 
world  war,  when  the  acronym  radar  received  general  international  acceptance,  though 
more  as  a  term  than  as  an  acronym.1 

As  the  expression  "radio  detection  and  ranging"  denotes,  radar  involves  the  use  of 
radio  for  both  detection  (is  it  there?)  and  ranging  (how  far  away  is  it?).  Radar  involves 
transmitting  electromagnetic  waves  (commonly  known  as  radio  waves)  toward  a  target  and 
receiving  the  echoes  from  that  target. 

The  wavelength  of  a  radio  or  radar  signal  traveling  through  space  is  measured  in 
meters  and  fractions  of  a  meter  (decimeter,  centimeter,  millimeter) ,  and  its  frequency, 
that  is,  the  number  of  waves  per  second,  is  expressed  in  hertz  or  multiples  of  hertz.  One 
hertz  is  one  wave  per  second.  The  high-frequency  radar  waves  used  in  planetary  research 
are  expressed  in  megahertz  (MHz,  a  million  hertz)  and  gigahertz  (GHz,  a  billion  hertz) . 

There  is  no  real  difference  between  radio  and  radar  waves.  International  treaties  and 
regulatory  agencies  have  set  aside  certain  groups  of  radio  frequencies,  called  bands,  for 
specific  radio  uses,  including  radar  applications  (see  Tables  11  and  12).  Although  the  first 
radars  to  attempt  detections  of  the  Moon  and  Venus  operated  in  the  UHF  band,  planetary 
radar  astronomy  today  uses  only  the  S  and  X  bands. 

A  radar  system  consists  of  a  transmitter  and  a  receiver,  plus  modulators,  signal  pro- 
cessors, and  data  processors.  Generally,  the  transmitter  and  receiver  share  the  same  anten- 
na. Such  an  arrangement  is  called  a  monostatic  radar.  When  the  transmitter  and  receiver 
do  not  share  the  same  antenna,  that  is,  when  they  are  located  in  different  places,  it  is 
called  a  bistatic  radar. 

All  of  the  radars  used  since  1958  to  study  solar  system  objects  have  a  parabolic  or  dish 
shape,  with  one  exception.  The  exception  is  the  Arecibo  antenna,  which  is  spherical. 

Another  difference  among  the  planetary  radars  is  their  transmitters.  The  Millstone 
Hill  radar,  which  Lincoln  Laboratory  investigators  used  to  attempt  a  detection  of  Venus  as 
early  as  1958,  was  a  pulse  radar.  Pulse  radars  transmit  short  bursts  of  energy  and  are  best 
suited  to  tracking  objects.  Millstone,  in  fact,  was  an  experimental  prototype  of  a  Ballistic 
Missile  Early  Warning  System  (BMEWS)  radar  used  to  detect  and  track  potential  incom- 
ing enemy  missiles.  In  contrast  are  the  continuous-wave  radars.  They  transmit  a  continu- 
ous flow  of  energy  and  are  better  suited  for  communications  applications.  JPL's  planetary 
radars  at  Goldstone  are  continuous-wave  radars. 

The  output  power  of  radars  is  expressed  in  watts.  When  comparing  the  power  of 
pulse  and  continuous-wave  radars,  one  must  keep  in  mind  that  although  pulse  radars  have 
relatively  high  peak  power  outputs  (that  is,  the  amount  of  power  at  the  highest  part  of  the 
pulse),  their  average  power  output,  a  measure  more  comparable  to  that  of  the  continu- 
ous-wave radars,  is  much  lower.  Average  power  is  what  counts.  Thus,  while  the  Millstone 
pulse  radar  had  a  peak  transmitting  power  of  265  kilowatts  in  1958,  the  JPL  transmitter  in 


1 .        Louis  A.  Gebhard,  Evolution  of  Naval  Radio-Electronics  and  Contributions  of  the  Naval  Research  Laboratory, 
Report  8300  (Washington:  NRL,  1979),  p.  170. 


275 


276 


TO  SEE  THE  UNSEEN 


Table  11 
Radar  Frequency  Bands  and  Usage 

Letter 
Band 

Frequency 
Range 

Usage 
in  Radar 

HF 

3-30  MHz 

Over  the  horizon  radar 

VHP 

30-300  MHz 

Very-long-range  surveillance 

UHF 

300-1000  MHz 

Very-long-range  surveillance 

L 

1-2  GHz 

Long-range  surveillance 
Enroute  traffic  control 

S 

2-4  GHz 

Moderate-range  surveillance 
Terminal  air  traffic  control 
Long-range  weather 

C 

4-8  GHz 

Long-range  tracking 
Airborne  weather  detection 

X 

8-12  GHz 

Short-range  tracking 
Missile  guidance 
Mapping  marine  radar 
Airborne  weather  radar 
Airborne  intercept 

Ku 

12-18  GHz 

High-resolution  mapping 
Satellite  altimetry 

K 

18-27  GHz 

Little  used  (water  vapor) 

Ka 

27-40  GHz 

Very-high-resolution  mapping 
Short-range  tracking 
Airport  surveillance 

V,W 

40-1  10  GHz 

Smart  munitions 
Remote  sensing 

Millimeter 

110  GHz 

Experimental 
Remote  sensing 

Source 

Fred  E.  Nathanson,  Radar  Design  Principles,  2d  ed.  (New  York:  McGraw-Hill,  1991),  p.  19. 

PLANETARY  RADAR  ASTRONOMY  PUBLICATIONS 


277 


Table  12 
Standard  Radar  Frequency  Bands 

Letter 
Band 

Frequency 
Range 

Specific  Frequencies 
Assigned  to  Radar 

HF 

3-30  MHz 

None  assigned 
(in  practice,  from  just  above  the 
broadcast  band,  1.605  MHz,  to 
40  MHz  or  higher 

VHP 

30-300  MHz 

138-144  MHz 
216-225  MHz 

UHF 

300-1000  MHz 

420-450  MHz 
890-942  MHz  (at  times  included 
in  the  L  band) 

L 

1000-2000  MHz 

1215-1400  MHz 

S 

2000-4000  MHz 

2300-2500  MHz 
2700-3700  MHz 

C 

4000-8000  MHz 

5250-5925  MHz 

X 

8-12  GHz 

8.5-10.68  GHz 

Ku 

12-18  GHz 

13.4-14.0  GHz 
15.7-17.7  GHz 

K 

18-27  GHz 

24.05-24.25  GHz 

Ka 

27-40  GHz 

33.4-36.0  GHz 

V 

40-75  GHz 

59-64  GHz 

W 

75-1  10  GHz 

76-81  GHz 
92-100  GHz 

Millimeter 

110-300  GHz 

126-142  GHz 
144-149  GHz 
231-235  GHz 
238-248  GHz 

Source 

Fred  E.  Nathanson,  Radar  Design  Principles,  2d  ed.  (New  York:  McGraw-Hill,  1991),  p.  19. 

1961  was  more  powerful,  though  its  average  power  output  was  only  nine  kilowatts.  When 
the  current  Arecibo  upgrade  is  completed,  it  will  have  the  highest  continuous-wave  trans- 
mitter output  available,  one  megawatt  (1,000  kilowatts). 

Radar  sensitivity  relates  to  the  ability  to  receive  signals.  One  of  the  limits  to  radar  sen- 
sitivity is  the  noise  created  by  the  antenna  and  receiver  systems,  not  to  mention  cosmic 
background  and  extraneous  terrestrial  radiation,  all  of  which  is  expressed  as  noise  "tem- 
perature" in  Kelvins  (abbreviated  K),  analogous  to  the  temperature  scale  of  the  same 
name.  The  higher  the  system  temperature  in  Kelvins,  the  noisier  the  radar  and  the  lower 
its  sensitivity.  In  1958,  the  Millstone  radar  had  an  overall  system  temperature  of  170 
Kelvins,  while  the  more  sensitive  JPL  radar  receiver  had  an  overall  system  temperature  of 
64  K  in  1961.  Although  impressively  low  in  their  day,  these  temperatures  today  are  judged 
intolerably  high. 


278  TO  SEE  THE  UNSEEN 


Planetary  radar  astronomy  borrows  much  of  its  terminology  from  optical  astronomy, 
although  not  always  retaining  the  original  meaning.  Facilities  for  conducting  radar  astron- 
omy research  are  called  observatories  and  the  instruments  telescopes.  Radar  telescopes 
"illuminate"  the  surface  of  targets.  The  reflecting  geometries  of  radar  telescopes,  called 
their  "optics,"  take  their  names  from  optical  instruments  (Cassegrainian  and  Gregorian 
subreflectors,  for  example) . 

Detection  and  ranging  are  two  of  the  elemental  observations  made  by  planetary 
radar  astronomers.  A  detection  occurs  when  a  radar  antenna  transmits  waves  toward  a  sus- 
pected target,  the  target  reflects  those  waves,  and  a  radar  antenna  receives  the  reflected 
waves  (echoes)  from  the  target.  If  we  were  crossing  the  Atlantic  Ocean  aboard  a  fictional 
ship,  say  the  U.S.S.  Marconi,  we  could  use  a  radio  transmitter  and  receiver,  acting  as  a  sim- 
ple radar  system,  to  detect  the  presence  of  icebergs  or  other  ships.  The  radio  pioneer 
Guglielmo  Marconi  suggested  doing  precisely  that  in  a  speech  delivered  in  1922. 

If  our  U.S.S.  Marconi  radar  were  to  detect  the  presence  of  another  ship,  we  could 
determine  the  distance  from  the  Marconi  to  the  other  ship  with  our  radar.  Measurements 
of  the  distance  to  the  target  are  called  range,  time-delay,  or  delay  measurements.  The  abil- 
ity to  use  radar  to  measure  range  is  based  on  the  knowledge  that  radio  waves  travel  at  a 
constant  speed,  namely,  the  same  speed  as  light. 

In  order  to  determine  how  far  away  a  target  is,  we  simply  measure  how  long  it  takes 
the  echoes  to  arrive  at  the  receiver  antenna.  The  greater  the  distance  to  the  target,  the 
longer  the  echoes  take  to  appear  in  the  receiver.  Conversely,  the  shorter  the  distance  to 
the  target,  the  less  time  the  echo  takes  to  appear  in  the  receiver.  The  time  between  the 
moment  of  transmission  and  the  moment  the  echo  is  detected  can  vary  considerably.  For 
the  farthest  bodies  detected  by  radar  astronomers,  such  as  Saturn's  rings,  the  signal 
round-trip  travel  time  is  about  two  and  a  half  hours,  while  the  round-trip  travel  time  to 
some  asteroids  detected  close  to  Earth  is  about  two  and  a  half  seconds. 

Another  basic  planetary  radar  measurement  is  Doppler  frequency  shift.  Whereas 
range  measurements  indicate  the  distance  between  the  radar  observer  and  the  target, 
Doppler  shift  indicates  the  motion  of  the  target  relative  to  the  observer.  With  our  fiction- 
al U.S.S.  Marconi  radar,  we  can  determine  not  only  the  presence  and  distance  of  another 
ship,  but  its  speed  toward  or  away  from  us  as  well. 

Radar  transmitters  send  waves  at  a  specific  frequency.  A  perfect  reflection  from  a 
motionless  target  appears  at  the  radar  receiver  (after  Fourier  transformation,  see  below) 
as  an  almost  line-like  peak.  The  echo  from  an  actual  solar  system  target,  however,  is  spread 
over  a  range  of  frequencies.  This  frequency  spread  is  called  a  spectrum  (plural  spectra) . 
In  radar  astronomy  experiments,  the  motions  of  the  Earth,  on  which  the  planetary  radar 
sits,  and  the  motions  of  the  target  are  far  more  complex.  The  Earth  spins  on  its  axis  and 
rotates  around  the  Sun,  while  the  target  planet  similarly  spins  and  rotates.  The  relative 
motions  of  the  Earth  and  target  planet  cause  what  is  known  as  the  Doppler  effect  or 
Doppler  shift  (or  even  Doppler  offset) . 

Simply  stated,  the  Doppler  effect  causes  the  frequency  of  radar  echoes  to  differ  from 
the  transmitted  frequency.  The  Doppler  effect  on  sound  waves  is  a  rather  common  expe- 
rience around  high-speed  transport.  If  we  stand  alongside  railroad  tracks,  or  a  freeway,  we 
can  detect  the  Doppler  effect  with  our  ears.  As  a  train  rapidly  approaches,  the  sound  of 
the  train  seems  to  rise  in  frequency,  that  is,  in  pitch;  as  the  train  travels  away  from  us,  its 
sound  seems  to  fall  in  frequency.  The  same  Doppler  effect  occurs  in  radar.  Depending  on 
the  line-of-sight  motion  of  a  planet  (or  whether  the  object  is  approaching  or  moving  away 
from  the  observing  radar),  the  frequency  of  the  planet's  echo  will  be  higher  or  lower  than 
the  transmitted  frequency. 


PLANETARY  RADAR  ASTRONOMY  PUBLICATIONS 


279 


Planetary  radar  astronomers  want  to  remove  the  average  Doppler  effect  in  order  to 
analyze  the  information  contained  in  the  Doppler  spectrum  spread,  so  they  use  a  radar 
ephemeris  program.  Although  the  average  Doppler  effect  sometimes  is  removed  in  the 
transmitter,  such  as  when  several  antennas  receive,  in  general  it  is  removed  in  the  receiv- 
er. An  ephemeris  (plural  ephemerides)  is  an  astronomical  term  that  refers  to  a  set  of 
tables  that  indicate  the  position  of  a  planet  or  other  body  in  the  sky.  A  radar  ephemeris 
program  is  computer  software  linked  to  the  radar  receiver  that  automatically  adjusts  the 
incoming  signal  for  the  expected  Doppler  shift.  The  amount  of  Doppler  shift  predicted 
by  the  ephemeris  program  must  be  accurate  enough  to  avoid  smearing  the  echo  in  fre- 
quency, and  this  requirement  places  stringent  demands  on  the  quality  of  the  radar 
ephemeris. 

Once  we  know  the  range  and  Doppler  shift  values  of  a  solar  system  target,  we  can 
construct  a  two-dimensional  radar  image  of  the  target  called  a  range-Doppler  or  delay- 
Doppler  image.  Maps  made  from  these  images  are  vital  to  the  exploration  of  the  solar  sys- 
tem, especially  the  planet  Venus,  whose  surface  is  obscured  by  clouds. 

In  range-Doppler  imaging,  we  assume  that  the  target  is  a  perfect  sphere.  An  excep- 
tion is  the  case  of  asteroids,  whose  nonspherical  shapes  require  special  modeling  tech- 
niques. The  transmitted  radar  waves  arrive  first  at  the  area  on  the  planet's  surface  that  is 
closest  to  Earth.  This  area  of  initial  impact  is  circular,  because  we  have  assumed  that  the 
target  is  spherical.  The  point  on  the  planet's  surface  that  is  closest  to  the  observer  is  called 
the  subradar  point.  If  we  could  look  at  the  target  with  radar  sensitive  eyes,  we  would  see  a 
relatively  dark  sphere  with  a  small  bright  spot  in  the  middle,  rather  like  a  shiny  ballbear- 
ing being  held  up  to  the  light. 


APPARENT 

ROTATION 

AXIS 


SUBRADAR 
POINT 


LINES 

OF 

CONSTANT 
PHASE 


RANGE  RINGS'^- -V-  - $  S ; :  ? : 


PHASE 

—  ^CALIBRATION 
CELL 


"DOPPLER  STRIPS" 


Figure  42 

Diagram  showing  intersection  of  range  rings  and  Doppler  strips  to  form  a  planetary  range-Doppler  image.  The  lines  of 
constant  phase  permit  resolution  of  north-south  ambiguity.  (Courtesy  of  Alan  E.  E.  Rogers.) 


280  TO  SEE  THE  UNSEEN 


Echoes  from  the  area  beyond  the  subradar  point  are  fewer  than  those  that  produce 
the  central  bright  spot.  Moreover,  they  reach  those  areas  later  than  the  waves  striking  the 
subradar  point,  because  they  have  a  greater  distance  to  travel.  The  range  values  for  those 
areas  toward  the  limbs,  then,  are  greater  than  those  for  the  subradar  region.  Looking 
again  at  the  target  with  our  radar  sensitive  eyes,  we  see  that  the  areas  at  a  constant  distance 
(range)  from  the  radar  transmitter  form  rings  around  the  subradar  point.  These  are 
called  range  rings. 

As  the  planet  spins  on  its  axis  toward  or  away  from  the  oncoming  radar  waves,  the 
spinning  motion  creates  a  Doppler  effect.  The  Doppler  frequency  shift  is  the  same  along 
a  strip  or  slice  running  across  the  planet's  surface,  because  within  each  Doppler  strip  of 
the  planet's  surface,  the  motion  relative  to  the  observer  is  the  same.  When  range  and 
Doppler  measurements  made  at  the  same  time  are  combined,  the  strips  of  equal  Doppler 
shift  intersect  the  range  rings  to  form  "cells."  Each  range-frequency  cell  (or  resolution 
cell)  corresponds  to  a  particular  area  on  the  planet's  surface.  The  amount  of  area  in  a  par- 
ticular cell  represents  the  amount  of  resolution  of  the  radar  image. 

In  range-Doppler  imaging,  any  given  range  ring  passes  through  the  same  Doppler 
strip  at  two  points.  One  point  is  in  the  northern  hemisphere,  the  other  in  the  southern 
hemisphere  of  the  planet.  The  two  points  have  the  same  range  and  Doppler  values, 
because  they  are  in  the  same  range  ring  and  the  same  Doppler  strip.  As  a  result,  these  two 
points  are  indistinguishable  in  the  radar  image  although  they  are  in  different  hemi- 
spheres. Radar  astronomers  call  this  problem  north-south  ambiguity. 

We  can  resolve  the  north-south  ambiguity  on  the  Moon  by  using  a  radar  whose 
beamwidth  is  narrower  than  the  diameter  of  the  Moon.  The  beamwidth  is  the  area  of  sky 
subtended  by  the  radar  beam.  Astronomers  measure  beamwidth,  and  all  solar  system 
objects,  in  minutes  and  seconds  of  arc.  The  diameter  of  the  Moon  is  a  half  degree  or 
30  minutes  of  arc.  With  a  beamwidth  of  only  10  minutes,  we  can  aim  the  radar  antenna  so 
that  the  subradar  point  is  10  minutes  of  arc  north  of  the  lunar  equator.  Echoes  are  not 
received  from  most  of  the  southern  hemisphere,  so  that  echoes  from  the  two  hemispheres 
do  not  overlap.  However,  the  technique  is  applicable  to  only  the  Moon.  Compared  to  the 
Moon's  30  minutes  of  arc,  Venus  is  only  a  speck;  its  diameter  is  but  one  minute  of  arc. 
Asteroids  are  less  then  one  second  of  arc  across. 

In  order  to  resolve  north-south  ambiguity  on  planetary  targets,  radar  astronomers 
sometimes  use  a  technique  called  interferometry.  An  optical  interferometer  is  an  instru- 
ment for  analyzing  the  light  spectrum  by  studying  patterns  of  interference,  that  is,  how 
light  waves  interact  with  each  oJier.  Radio  astronomers  began  designing  interferometers 
in  the  late  1950s.  Planetary  radar  interferometry  derived  directly  from  those  interferom- 
eters. Radio  interferometers  use  two  or  more  radio  telescope  antennas  arranged  along  a 
line  (called  the  base  line).  The  separate  antennas  are  linked  electronically,  so  that  the 
signals  received  at  different  points  along  the  base  line  can  be  combined,  compared,  and 
studied  with  elaborate  computer  programs.  Radar  interferometers  are  somewhat  simpler. 

A  radar  interferometer  consists  of  two  antennas.  The  primary  antenna  transmits 
signals  to  the  target  and  receives  them.  A  secondary  antenna,  located  not  far  (say,  1  to  10 
km  distant)  from  the  primary  antenna,  also  receives  the  echoes.  Although  a  three- 
antenna  radar  interferometer  was  attempted  between  1977  and  1988,2  in  practice  radar 
interferometers  use  only  two  antennas. 


2.       Jurgens,    Goldstein,    Rumsey,    and   R.    Green,    "Images   of  Venus   by   Three-Station    Radar 
Interferometry:  1977  Results, "  Journal  of  Geophysical  Research  85  (1980):  8282-8294. 


PLANETARY  RADAR  ASTRONOMY  PUBLICATIONS  281 


The  echoes  received  by  both  antennas  are  fed  into  a  complex  computer  program 
that  combines  the  echoes  and  obtains  the  fringe  size  (amplitude)  and  phase  for  each 
range-Doppler  resolution  cell.  The  computer  program  rotates  the  fringe  pattern  so  that 
the  lines  of  constant  phase  are  perpendicular  to  the  strips  of  equal  Doppler  value.  The 
north-south  ambiguity  now  is  resolved,  because  the  phase  at  points  A  and  B  have  distinct 
phase  values. 

During  the  1950s,  researchers  underwritten  by  the  military  developed  a  similar  radar 
imaging  process  that  used  both  range  and  Doppler  data.  However,  that  process  involved 
imaging  the  Earth  from  aircraft  and  relied  on  developing  a  radar  "history"  of  the  target 
to  create  an  image,  while  planetary  range-Doppler  mapping  created  a  "snapshot"  of  a 
planetary  surface  from  a  ground-based  radar.  The  airborne  imaging  process,  called 
synthetic  aperture  radar,  has  since  played  a  key  role  in  the  mapping  of  Venus  by  the 
Magellan  spacecraft 

Radar  astronomers  do  not  depend  entirely  on  range  and  Doppler  data,  however.  The 
echo  from  a  solar  system  target  exhibits  a  number  of  attributes.  From  their  analysis  of 
those  attributes,  radar  astronomers  draw  conclusions  about  the  characteristics  of  the 
target.  For  example,  the  shape  of  power  spectra  can  provide  information  about  a  target. 
If  we  aim  at  an  asteroid  and  get  an  echo  with  two  major  peaks,  called  a  bimodal  echo,  we 
can  interpret  the  echo  as  possibly  indicating  a  bifurcated  shape,  perhaps  two  asteroids 
joined  together.  Radar  observations  of  asteroid  4769  Castalia  (1989  PB),  for  instance, 
revealed  it  to  be  a  contact  binary  asteroid.3 

Small  detail  features  on  power  spectra  also  can  reveal  vital  information  about  a 
target's  motion.  For  example,  radar  observations  of  Venus  made  in  1964  indicated  that 
planet's  rotational  rate  and  direction.  The  radar  instrument  was  both  sufficiently  power- 
ful and  sensitive  that  a  large  feature  on  the  planet's  surface  showed  up  in  the  power 
spectra  as  an  irregularity  or  "detail."  The  detail  resulted  from  the  fact  that  the  surface 
feature  scattered  back  to  the  radar  antenna  more  energy  than  the  surrounding  area. 

On  close  examination,  one  irregularity  in  the  power  spectra  persisted  day  after  day 
and  appeared  to  change  its  position  slowly.  A  study  of  the  irregularity's  movement  led  to 
a  calculated  rotational  rate  for  the  planet,  but  not  immediately  its  prograde  (forward)  or 
retrograde  motion.  That  information  came  from  measurements  of  the  width  of  the  lower 
portion  of  the  power  spectra.  Those  widths  were  compatible  with  only  a  retrograde 
motion. 

In  the  normal,  round-trip  journey  of  a  radar  wave  from  transmitter  to  target  to 
receiver,  a  certain  amount  of  power  is  lost.  The  amount  of  that  loss  is  given  by  the  so-called 
radar  equation.  The  amount  of  power  that  reaches  a  target  is  inversely  proportional  to  the 
square  of  the  distance  to  the  target,  but  the  amount  of  power  returned  from  the  target  to 
the  receiving  antenna  also  varies  inversely  proportional  to  the  square  of  the  distance  to 
the  target.  After  the  complete  round-trip  from  transmitter  to  receiver,  the  amount  of 
power  that  arrives  at  the  receiving  antenna  varies  inversely  with  the  distance  to  the  target 
raised  to  the  fourth  power,  that  is,  the  square  of  the  square  of  the  distance.  The  radar 
equation  shows  that  large  amounts  of  power  (hundreds  of  kilowatts)  must  be  radiated  into 
space  in  a  very  narrow  beam  in  order  to  detect  a  target. 

The  amount  of  power  returned  from  a  target  can  reveal  much  about  its  surface  char- 
acteristics. The  total  power  returned  from  a  target  is  a  function  of  its  radar  cross  section 


3.        Hudson  and  Ostro,  "Shape  of  Asteroid  4769  Castalia  (1989  PB)  from  Inversion  of  Radar  Images," 
Sri«n«263  (1994):  940-943. 


282  TO  SEE  THE  UNSEEN 


or  backscattering  coefficient,  that  is,  the  target's  ability  to  reflect  energy  to  the  radar 
receiving  antenna.  Radar  astronomers  express  the  radar  cross  section  of  a  target  in  terms 
of  an  equivalent,  perfectly  reflecting  surface.  If  a  target  scatters  power  equally  in  all  direc- 
tions, its  cross  section  is  equal  to  the  geometric  area  of  the  target.  That  is  the  case  of  our 
ideal  ballbearing  target.  For  a  perfectly  reflecting  spherical  target,  the  radar  cross  section 
is  one  fourth  the  total  surface.  Surface  irregularities  affect  the  amount  of  power  returned 
(or  scattered  back)  from  a  target.  Radar  echoes  have  two  scattering  components,  called 
quasispecular  and  diffuse.  The  quasispecular  component  arises  from  mirror-like  reflec- 
tions from  parts  of  a  flat  or  gently  undulating  surface.  Those  surface  facets  are  perpen- 
dicular to  the  line  of  propagation,  so  they  direct  a  large  amount  of  energy  back  toward  the 
observer.  Such  echoes  concentrate  at  the  center  of  the  planet's  visible  disk,  that  is,  around 
the  subradar  point,  because  the  likelihood  of  finding  favorably  oriented  facets  is  highest 
where  the  surface  is  perpendicular  to  the  incoming  radar  beam.  The  diffuse  scattering 
component  comes  from  objects  and  structures  with  irregular  shapes  and  therefore  facets 
that  redirect  much  of  the  radar  beam  away  from  the  observer.  The  signal  returned  from 
the  areas  toward  the  limbs  is  called  diffuse. 

The  amount  of  power  returned  from  a  target  is,  therefore,  a  consequence  of  the  scat- 
tering component,  quasispecular  or  diffuse,  and  the  angle  of  a  surface  facet  relative  to  the 
line  of  propagation  of  the  radar  wave.  Flat  surfaces  perpendicular  to  the  line  of  propaga- 
tion return  power  directly  back  to  the  radar.  The  greatest  amount  of  power  returned  from 
a  target,  then,  comes  from  flat  surfaces  that  are  perpendicular  to  the  line  of  propagation. 
If  the  reflecting  surface  is  not  perpendicular  to  the  line  of  propagation,  then  power  will 
be  reflected  away  from  the  radar,  and  the  amount  of  power  returned  to  the  radar  anten- 
na will  diminish.  The  reduction  in  power  will  increase  as  the  surface  is  tilted  away  from 
the  radar. 

For  example,  if  a  planetary  target  has  mountains  or  craters,  a  portion  of  the  radar 
power  will  be  reflected  away  from  the  return  path,  depending  on  the  angle,  that  is,  the 
amount  of  slope,  of  the  mountain  or  crater.  The  more  power  returned,  the  gentler  is  the 
slope  or  angle  of  the  surface.  Factors  other  than  surface  slope  can  affect  the  amount  of 
power  returned  from  a  target,  too. 

If  a  planetary  surface  is  covered  by  boulders  or  other  material  with  multiple  sides,  a 
complex  scattering  process  takes  place.  Some  power  is  returned  to  the  radar,  some  power 
is  deflected  away  from  the  radar  return  path,  while  some  power  scatters  among  the  boul- 
ders. If  the  surface  is  covered  by  material  significantly  smaller  than  boulders,  say  volcanic 
ash,  the  loss  of  power  from  scattering  in  directions  other  than  the  return  path  can  be  con- 
siderable. 

Although  range-Doppler  mapping  techniques  provide  one  means  for  correlating 
echo  power  spectra  and  surface  features,  they  are  not  always  practical.  Other  methods 
must  be  used.  For  example,  Mars  rotates  much  faster  than  Venus,  whose  slow  retrograde 
motion  makes  it  an  ideal  radar  target.  Mars  is  what  radar  astronomers  call  an  overspread 
target.  The  rapid  rotation  of  that  planet  means  that  the  signal  from  one  range  ring 
spreads  over  into  the  next  ring,  or  the  signal  from  one  Doppler  strip  spreads  over  into  the 
next  strip.  Also,  the  echo  from  Mars  is  much  weaker,  because  the  distance  to  Mars  is 
greater  than  to  Venus. 

In  helping  to  select  a  landing  site  for  the  Viking  lander,  for  example,  radar 
astronomers  relied  on  a  different  approach  to  interpret  the  amount  of  power  returned 
from  an  area  of  the  surface.  In  this  approach,  a  geometric  model  for  the  entire  visible  sur- 
face of  the  planet  was  assumed.  These  models,  or  scattering  laws  as  they  are  called,  also 
can  be  derived  empirically  from  actual  radar  observations  of  the  target,  if  the  target  sur- 
face is  sufficiently  well  known.  The  most  commonly  used  model  is  the  Hagfors  scattering 


PLANETARY  RADAR  ASTRONOMY  PUBLICATIONS  283 


law,  named  for  its  originator,  Tor  Hagfors,  an  ionosphericist  and  radar  astronomer  who  is 
currently  Director  of  the  Max  Planck  Institut  fur  Aeronornie. 

In  studying  candidate  sites  for  the  Viking  lander,  radar  astronomers  at  Haystack, 
Arecibo,  and  Goldstone  applied  the  Hagfors  scattering  law  and  determined  the  slope,  that 
is,  the  degree  of  tilt  from  the  line  of  propagation,  of  various  areas  of  the  Martian  surface. 
Site  candidates  had  to  be  inclined  no  more  than  19  degrees;  otherwise,  the  lander  would 
topple  over.  They  also  had  to  be  free  of  rocks  and  other  objects  larger  than  22  cm,  the 
height  of  the  lander  vehicle. 

Radar  data  were  capable  of  indicating  the  roughness  of  the  Martian  surface  down  to 
a  few  centimeters,  while  photographs  had  a  resolution  of  roughly  100  meters,  larger  than 
a  football  field.  The  radar  data,  however,  was  not  expressed  visually,  like  the  photographs, 
but  mathematically  as  the  root-mean-square  (rms)  slope.  The  rms  is  a  special  mathemati- 
cal method  for  averaging.  The  rms  slope  gives  an  indication  of  the  average  slope  or  incli- 
nation of  a  given  area  of  the  Martian  surface.  When  applying  the  Hagfors  scattering  law, 
the  value  for  the  rms  slope  varies  in  theory  up  to  three  degrees,  the  upper  limit  for  the 
validity  of  the  assumptions  underlying  the  model.  In  practice,  however,  the  Hagfors  scat- 
tering law  yields  much  higher  values  of  rms  slope. 

One  of  the  most  important  signal  parameters  used  in  planetary  radar  astronomy 
today  is  polarization.  The  earliest  lunar  radar  experiments  carried  out  at  Jodrell  Bank 
used  a  linear  antenna  feed.  Antenna  feeds  are  either  linear  or  circular,  and  the  feed  shape 
determines  the  polarization  of  the  transmitted  wave.  When  Jodrell  Bank  investigators  sent 
radar  signals  to  the  Moon,  they  discovered  two  patterns  of  signal  fading.  Normal  lunar 
libration  caused  the  slowly  fading  echoes,  while  the  rapidly  fading  signals,  they  conclud- 
ed, resulted  from  the  radar  waves  passing  through  the  Earth's  ionosphere. 

In  the  19th  century,  the  British  scientist  Michael  Faraday  discovered  that  a  magnetic 
field  could  alter  the  plane  of  polarization.  The  effect  since  has  come  to  be  known  as 
Faraday  rotation.  In  the  case  of  the  lunar  radar  signals,  the  Earth's  magnetic  field  rotated 
the  signals'  plane  of  polarization  as  they  passed  through  the  ionosphere. 

A  radar  target  also  can  change  the  handedness,  or  rotational  sense,  of  circularly 
polarized  waves.  If  we  transmit  circular  waves  with  right-handed  polarization  to  a  perfect- 
ly reflecting  target,  the  power  returns  with  a  left-handed  polarization.  If  we  transmit  right- 
handed  polarization  and  adjust  the  antenna  feed  to  accept  right-handed  polarization,  the 
antenna  will  detect  little  or  no  returned  power.  In  practice,  when  dealing  with  the  inner 
planets  (Mercury,  Venus,  and  Mars),  most  power  returns  from  a  planetary  target  in  the 
opposite  sense  of  polarization  in  which  it  is  transmitted. 

Exceptions  to  this  rule  arose  when  radar  astronomers  began  exploring  the  Galilean 
moons  of  Jupiter  and  other  icy  targets.  When  radar  signals  return  from  the  surfaces  of 
those  targets,  somewhat  more  of  the  power  is  received  in  the  same  sense  of  polarization. 
In  other  words,  if  we  transmit  right-hand  polarization,  more  of  the  power  will  return  with 
right-handed  polarization.  The  peculiar  nature  of  these  radar  targets  has  elevated  the 
importance  of  the  ratio  of  same  sense  to  opposite  sense  polarization  as  a  radar  measure- 
ment. Radar  astronomers  now  transmit  one  sense  of  polarization  and  receive  both  right- 
hand  and  left-hand  polarization,  then  they  compare  the  right-hand  and  left-hand  values. 
While  fractured  ice  is  the  apparent  cause  of  this  polarization  phenomenon,  the  mecha- 
nism that  gives  rise  to  it  is  only  now  beginning  to  be  understood. 

Planetary  range-Doppler  radar  experiments  take  place  in  several  stages:  data  taking, 
decoding,  rotating  the  matrix,  the  Fourier  transform,  conversion  into  latitudes  and  lon- 
gitudes to  create  maps.  The  first  stages,  especially  data  taking  and  decoding,  are  rather 
routine  and  standardized;  software  specialization  tends  to  take  place  in  the  last  stages  of 
the  process,  such  as  converting  the  data  into  latitudes  and  longitudes. 


284  TO  SEE  THE  UNSEEN 


While  data  taking  involves  the  combined  use  of  the  radar  system  and  an  associated 
computer,  the  remaining  stages  take  place  entirely  on  a  computer.  Computer  time 
accounts  for  most  of  the  processing  time  spent  on  a  range-Doppler  experiment.  With 
modern  computer  technologies  that  accelerate  processing  time,  data  reduction  takes  far 
less  time  than  before.  At  the  Arecibo  telescope,  a  typical  run  of  observations  on  Mercury 
takes  about  10  minutes.  Data  processing  of  those  10  minutes  of  radar  activity  consumes 
another  hour  and  a  quarter  to  an  hour  and  a  half  of  computer  time.  Roughly,  then,  every 
minute  spent  making  radar  observations  translates  into  eight  minutes  of  processing  time. 

Without  those  special  accelerating  technologies,  a  mainframe  computer  takes  far 
more  time;  it  is  almost  80  times  slower.  One  run,  then,  might  take  an  entire  day  to  pro- 
cess. Older  mainframe  computers  were  even  slower.  The  competition  for  computer  time 
was  often  as  intense  as  it  was  for  antenna  time.  Moreover,  these  computer  times  apply  only 
to  data  reduction,  the  initial  preparation  of  the  data.  Analysis,  modeling,  and  interpreta- 
tion can  be  far  more  time  consuming. 

The  first  stage  of  a  planetary  radar  experiment  is  the  recording  of  the  raw  echoes  as 
they  come  from  the  antenna  through  the  receiver.  In  the  earliest  lunar  radar  experiments 
conducted  at  Jodrell  Bank  in  the  1950s,  the  echoes  were  observed  on  an  oscilloscope  and 
recorded  with  a  cinema  camera.  The  films  are  extant  and  form  part  of  the  archives 
deposited  with  the  University  of  Manchester.  Beginning  with  the  first  attempts  on  Venus 
in  1958,  the  raw  signals  were  recorded  on  magnetic  tape.  In  addition,  they  were  routine- 
ly converted  from  analog  into  digital  signals  for  processing.  Today,  all  planetary  radar 
astronomy  is  carried  out  digitally. 

The  unprocessed  echoes  are  usually  too  weak  and  too  noisy  to  process,  so  the  echoes 
are  accumulated  together.  The  next  stage  is  to  decode  the  signals.  Before  transmission, 
the  signal  is  encoded  with  a  repeating  binary  code.  Pulse  radars  achieve  binary  coding  by 
turning  the  signal  off  and  on.  With  continuous-wave  radars,  binary  coding  is  accom- 
plished by  changing  the  phase  of  the  signal.  These  off-on  states  and  phase  changes  in  the 
coded  transmission  tell  the  radar  astronomer  which  part  of  the  wave  is  being  examined. 
An  accompanying  time  code  identifies  the  location  on  the  planet  where  the  particular 
echoes  originate. 

The  next  step  in  forming  a  planetary  radar  map  is  to  rotate  the  matrix.  Once  the 
codes  have  been  removed  from  the  echoes,  the  signals  are  arranged  in  a  matrix  that  cor- 
responds to  the  various  range  rings  on  the  planet.  The  computer  software  looks  at  each 
code  cycle  and  considers  each  range  ring  separately.  The  values  for  a  given  range  ring  are 
a  function  of  time.  The  software  now  must  decide  which  frequencies  are  present,  in  order 
to  find  the  Doppler  delay  values. 

A  Fourier  transform  sorts  echoes  from  a  given  range  ring  into  frequency  bins.  A 
Fourier  transform  is  a  specific  type  of  transform,  a  powerful  mathematical  expression  that 
transforms  (hence  the  name)  one  geometrical  figure  or  analytical  expression  into  anoth- 
er. During  the  1960s,  the  Fast  Fourier  transform  was  devised  by  engineers  in  the  field  of 
signal  processing.  As  a  result,  a  mathematical  operation  that  previously  took  30  minutes 
on  an  IBM  8094  mainframe  computer  now  took  only  about  five  seconds.4 

The  result  of  the  Fourier  transform  is  a  range-Doppler,  two-dimensional  picture. 
Additional  analysis  with  various  computer  algorithms  written  in  the  software  can  yield  a 
three-dimensional  picture.  However,  the  three-dimensional  picture  requires  adding 
further  information  to  the  range-Doppler  map. 

This  succinct  cursory  overview  of  a  planetary  radar  experiment  is  limited  to  only 
range-Doppler  mapping.  Radar  astronomers  carry  out  several  other  types  of  experiments. 
Most  experiments  are  routine  and  rely  on  cookbook  software  and  processing.  Radar 


4.        Gwilym  M.Jenkins  and  Donald  G.  Watts,  Spectral  Analysis  and  its  Applications  (San  Francisco:  Holden- 
day,  1968),  pp.  313-314. 


PLANETARY  RADAR  ASTRONOMY  PUBLICATIONS  285 


interferometry  and  the  random  code  technique,  adapted  from  ionospheric  radar 
research,  for  example,  employ  specialized  software  and  processing  techniques. 

A  number  of  articles  and  book  chapters  on  radar  astronomy  published  since  1960 
discuss  the  field,  its  accomplishments,  and  its  techniques.  Their  intended  audience  runs 
the  gamut  from  general  to  specialized.  They  are  recommended  to  those  wishing  infor- 
mation on  radar  astronomy  beyond  that  provided  here. 

For  Further  Reading 

Eshleman,  Von  R.  "Radar  Astronomy:  Exploration  of  the  Solar  System  Using  Man-made 
Radio  Waves."  In  Aeronautics  and  Astronautics:  Proceedings  oftheDurand  Centennial  Conference, 
Stanford,  August  5,  1959,  edited  by  N.  J.  Hoff  and  W.  G.  Vincenti,  207-226.  London: 
Pergamon  Press,  1960. 

Eshleman,  Von  R.  and  Alan  M.  Paterson.  "Radar  Astronomy."  Scientific  American  203 
(1960):  50-54. 

Evans,  John  V.  "Radar  Astronomy."  Contemporary  Physics  2  (1960):  116-142. 
Evans,  John  V.  "Radar  Astronomy."  Science  158  (1967):  585-597. 

Green,  Paul  E.,  Jr.,  and  Gordon  H.  Pettengill.  "Exploring  the  Solar  System  by  Radar".  Sky 
and  Telescope  20  (1960):  9-14. 

Hagfors,  Tor,  and  Donald  B.  Campbell.  "Mapping  of  Planetary  Surfaces  by  Radar". 
Proceedings  of  the  IEEE  61  (1973):  1219-1225. 

Jurgens,  Raymond  F.  "Earth-based  Radar  Studies  of  Planetary  Surfaces  and  Atmospheres." 
JFFF.  Transactions  on  Geoscience  and  Remote  Sensing  GE-2Q  (1982):  293-305. 

Kippenhahn,  Rudolf.  Bound  to  the  Sun:  The  Story  of  Planets,  Moons,  and  Comets,  trans.  Storm 
Dunlop.  New  York:  W.  H.  Freeman  and  Company,  1990,  pp.  259-272. 

Muhleman,  Duane  O.,  Richard  M.  Goldstein,  and  Roland  Carpenter.  "A  Review  of  Radar 
Astronomy,  Parts  1  and  2."  JERK  Spectrum  2  (1965):  44-55  and  78-89. 

Ostro,  Steven  J.  "Planetary  Radar  Astronomy."  Reviews  of  Geophysics  and  Space  Physics  21 
(1983):  186-196. 

Ostro,  Steven  J.  "Planetary  Radar  Astronomy."  In  Encyclopedia  of  Physical  Science  and 
Technology,  edited  by  Robert  A.  Meyers,  10:611-634.  Orlando:  Academic  Press,  1987. 

Ostro,  Steven  J.  "Planetary  Radar  Astronomy."  Reviews  of  Modern  Physics  65  (1993):  1235- 
1279. 

Ostro,  Steven  J.  "Radar  Astronomy."  In  McGraw-Hill  Encyclopedia  of  Astronomy,  edited  by 
Sybil  P.  Parker  and  Jay  M.  Pasachoff,  347-348.  New  York:  McGraw-Hill,  1993. 


286  TO  SEE  THE  UNSEEN 


Pettengill,  Gordon  H.  "Radar  Astronomy."  Transactions  of  the  American  Geophysical  Union  44 
(1963):  453-455. 

Pettengill,  Gordon  H.  "Planetary  Radar  Astronomy."  In  Solar  System  Radio  Astronomy,  edit- 
ed by  Jules  Aarons,  401-411.  New  York:  Plenum  Press,  1965. 

Pettengill,  Gordon  H.   and  Irwin  I.  Shapiro.   "Radar  Astronomy."  Annual  Review  of 
Astronomy  and  Astrophysics  3  (1965):  377—410. 

Pettengill,  Gordon  H.  "Radar  Astronomy."  International  Science  and  Technology  58  (1966): 
72-74,  76,  78,  80-82. 

Shapiro,  Irwin  I.  "Planetary  Radar  Astronomy."  JF.F.R  Spectrum  5  (1968):  70-79. 

Thomson,  John  H.  "Planetary  Radar."  Quarterly  Journal  of  the  Royal  Astronomical  Society  4 
(1963):  347-375. 

Thomson,  John  H.  "Planetary  Radar."  Science  Progress  53  (1965):  183-190. 


Abbreviations 


For  the  most  part,  when  an  abbreviation  is  first  introduced,  it  is  preceded  by  the  full 
spelling.  Most  abbreviations  found  in  this  text  are  commonly  used,  such  as  AFB  for  Air 
Force  Base,  while  others  are  more  apt  to  be  seen  in  technical  literature,  such  as  K  for 
Kelvin.  In  the  case  of  organizations,  they  are  always  introduced  by  their  full  name;  abbre- 
viations appear  only  in  subsequent  references,  though  not  all  subsequent  references  are 
abbreviated.  Most  readers  will  recognize  many  organizational  abbreviations  immediately, 
such  as  NASA. 

Interviews  are  referenced  in  the  notes  in  an  abridged  form.  Only  the  interviewee's 
surname  and  the  interview  date  (in  the  form  date/month/year)  are  noted;  complete 
interview  information  is  located  in  Appendix  Two,  Oral  History  Interviews. 

A  few  reports  that  appear  serially  and  are  available  from  only  a  limited  source  are 
routinely  cited  in  the  notes  in  abbreviated  form.  The  annual  reports  published  by JPL  and 
found  in  the  JPL  Archives  are  cited  as  JPL  Annual  Reports,  JPLA.  The  quarterly  reports  of 
the  NAIC  were  found  only  at  the  NAIC.  These  reports  consist  of  a  small  number  of  typed 
pages  submitted  to  the  NSF,  the  oversight  agency  for  the  Arecibo  Observatory.  In  order  to 
cite  them  simply,  the  following  form  was  used:  NAIC  QR  Q2/1987,  4-5,  in  which  pages 
4-5  of  the  second  QR  (quarterly  report)  of  1987  are  referenced.  Also,  the  minutes  of  the 
meetings  of  the  Goldstone  Solar  System  Radar,  furnished  to  the  author  by  Steven  Ostro, 
are  referred  to  as  GSSR  Min.,  followed  by  the  date  of  the  meeting  in  the  form 
date/month/year. 

The  GSSR  minutes  were  only  one  of  many  items  provided  by  several  individuals  from 
their  personal  materials.  In  the  notes,  these  are  referred  to  as  "Smith  materials,"  after  the 
surname  of  the  individual  providing  them.  The  Acknowledgments  (p.  iv)  section  above 
indicates  the  full  names  of  those  furnishing  such  materials. 

Documents  in  open  archives  are  cited  in  one  of  two  ways,  depending  on  whether  the 
archives  had  assigned  numbers  to  files.  When  a  file  number  is  available,  the  citation  pro- 
vides a  description  of  the  item  and  its  date,  followed  by  the  file  number,  the  box  number, 
and  the  accession  number  (or  collection  name) ,  and  lastly  the  name  of  the  archival  repos- 
itory. Otherwise,  the  description  of  the  item  and  its  date  are  followed  by  the  folder  title  in 
quotes,  the  box  number  and  accession  number  (or  collection  name) ,  and  the  name  of  the 
archival  repository. 

References  to  unpublished  materials  use  the  following  abbreviations  to  indicate 
archival  repositories  and  specific  collections  within  those  archives. 

AIO  Arecibo  Ionospheric  Observatory 

AIOL  Library,  Arecibo  Observatory 

CRSR  Center  for  Radiophysics  and  Space  Research,  Cornell  University 

HAUSACEC        Historical  Archives,  U.S.  Army  Communications-Electronics  Command, 
Ft.  Monmouth,  NJ 

JBA  Jodrell  Bank  Archives,  University  of  Manchester 

JPLA  Jet  Propulsion  Laboratory  Archives 


287 


288 


TO  SEE  THE  UNSEEN 


JPLMM  Jet  Propulsion  Laboratory  Archives,  Magellan  materials 

JPLPLC  Jet  Propulsion  Laboratory  Archives,  Peter  Lyman  Collection 

LLLA  Lincoln  Laboratory  Library  Archives 

MITA  MIT  Institute  Archives  and  Special  Collections 

NAIC  National  Astronomy  and  Ionosphere  Center 

NAS  Archives  of  the  National  Academy  of  Sciences 

NHO  NASA  History  Office 

NHOB  NASA  History  Office,  Brunk  Papers 

NRLHRC  Naval  Research  Laboratory  Historical  Reference  Collection,  Office  of  the 
Historian,  NRL,  Washington 

NSFHF  NSF  Historian's  File,  National  Science  Foundation 

NSFL  Library,  National  Science  Foundation 

PAHU  Pusey  Archives,  Harvard  University 

RLSEL  Radioscience  Laboratory,  Stanford  Electronics  Laboratories 

SCRA  Stanford  Center  for  Radar  Astronomy 

SEBRING  NEROC,  Haystack  Observatory,  materials  held  in  the  Sebring  building 

SIA  Archives  of  the  Smithsonian  Institution 

SIAOS  Archives  of  the  Smithsonian   Institution,   Office   of  the   Secretary 
Collection 

SIAUSC  Archives  of  the  Smithsonian  Institution,  Under  Secretary  Collection 
SUA  Stanford  University  Archives 


Index 


Air  and  Space  Museum.  See  tinder  Smithsonian 
Institution. 

American  Astronomical  Society  (AAS),  61;  Division 
for  Planetary  Science  (DPS),  123,  203,  244,  251,  254. 

Abell,  George,  50. 

Advanced  Research  Projects  Agency  (ARPA),  46,  58, 
62,  65,  87,  88,  89,  90,  94,  95,  96,  97;  Defender 
Program,  88-89,  97. 

Albee,  Arden  L.,  226. 

Aller,  Lawrence,  50. 

Almond,  Mary,  16. 

American  Geophysical  Union,  177,  203. 

American  Institute  of  Aeronautics  and  Astronautics, 
255. 

Anderson,  Clinton  P.,  80,  82. 

Apollo,  9,  83,  85,  92,  108, 135,  149,  153,  169,  177,  183. 

Appleton,  Edward,  12,  13. 

Arecibo  Observatory,  67,  74,  75,  77,  83,  87,  92,  93,  94, 
95,  121,  127,  129,  133,  135,  139,  143,  147,  150,  151, 
152,  155,  158,  160,  161,  177,  180,  183,  190, 191,  195, 
197,  203,  205,  265;  design  and  building  of,  88-91; 
DoD  Ionospheric  Research  Facility,  90;  line  feed 
problems  and  research,  96-97;  formation  of  NAIC, 
101;  becomes  NSF  National  Research  Center,  94- 
101;  S-band  upgrade,  94,  96-97,  101-105;  "Arecibo 
Message,"  104;  NASA-NSF  agreement,  101-103,  203; 
second  upgrade,  225,  230-235,  260;  Gregorian 
feed/reflector,  96,  231-233;  impact  of  second 
upgrade  on  radar  astronomy,  260;  Arecibo  and 
Goldstone  compared,  265. 

Ash,  Michael  E.,  122,  125,  150. 

Aspinall,  Arnold,  20. 

Asteroids,  221-224,  259-260;  rapid  rate  of  discovery, 
246-247;  growth  of  literature,  222,  260-261;  and  Big 
Science,  222,  247;  as  radar  targets,  248;  near-Earth 
and  Earth-crossing,  121,  247;  contact-binary,  249, 
250-251;  composition  of,  249;  ephemcrides,  256-257; 
range-Doppler  imaging  of,  250;  modelling  shapes  of, 
222-223,  250-252,  254-255;  potential  Earth  collision 
of,  255-256;  Spaceguard,  255-256,  259;  Spacewatch, 
222;  Palomar  Planet-Crossing  Asteroid  Survey 
(PCAS),  222;  1989  AC  (4179  Toutatis),  252,  254, 
255;  Apollo,  248;  1580  Betulia,  224;  Ceres,  224;  1986 
DA,  249,  250,  256;  1982  DB,  256;  Eros,  4647,  222, 
224,  250;  1989  FC,  255;  243  Gaspra,  255;  1620 
Geographos,  254,  255;  Icarus,  121-123,  213,  221; 
Icarus  discovery  poem,  122;  951  Ida,  255;  IRAS- 
Araki-Alcock,  111;  Iris,  248;  1627  Ivar,  250,  256;  1986 
JK,  256;  216  Kleopatra,  249;  Metis,  224;  2201  Oljata, 
249;  1980  PA,  250;  2  Pallas,  249;  1989  PB  (4769 
Castalia),  250-255;  Psyche,  248;  Quetzalcoatl,  248; 
2100  Ra-Shalom,  250;  1972  Toro,  213,  250;  4  Vesta, 
111,  223,  224,  248;  Victoria,  250-251. 


Astronomical  Unit:  measured  by  radar,  42-46,  124; 

radar  value  adopted  by  International  Astronomical 

Union,  46-49. 
Auroras,  20-21. 

B 

Badgley,  Peter  C.,  169. 

Baker,  Lynn  A.,  232. 

Barrett,  Alan  H.,  141. 

Barsukov,  Valery  L.,  190,  191,  194. 

Barth,  Charles  A.,  186. 

Barthle,  Robert  C.,  58. 

Basilevsky,  Alexander,  190,  194,  197. 

Bateman,  Ross,  22. 

Bay,  Zoltan,  10-12,  32. 

Big  Science,  viii-xii,  87,  112;  and  Little  Science,  ix-xii; 
and  radar  astronomy,  106.  See  also  Radar  astronomy. 

Billingsley,  George,  195. 

Bindschadler,  D.  L.,  242-243. 

Bistatic  radar,  206,  214,  259;  Goldstack,  206,  111-112; 
Goldstone-VLA,  236-238,  239-241,  243,  259;  NEROC- 
VLA,  236;  Arecibo-Goldstone,  259;  observations  of 
asteroid  Toutatis,  252;  observations  of  Moon,  245. 

Blackett,  Patrick  M.  S.,  13. 

Bok,  Bart  J.,  96. 

Booker,  Henry,  88,  89,  90,  99. 

Boot,  Henry  A.  H.,  4. 

Bowen,  Dr.  Edward  G.  Taffy",  5,  31. 

Bowles,  Ken,  88. 

Boyce,  Joseph,  194. 

Bracewell,  Ronald  N.,  31,  109. 

Bradley,  Lames,  77,  78. 

Breit,  Gregory,  3. 

Brenner,  Norman,  120. 

Briggs,  Geoff,  235. 

Brouwer,  Dirk,  47,  48. 

Brown,  Harrison,  244. 

Brown,  Walter,  172. 

Brown  University,  186,  190,  191,  194,  1%,  197.  See  also 
Microsymposia. 

Browne,  Ian  C.,  44. 

Brunk,  William,  71,  102,  103,  106. 

Burke,  Bernard  F.,  75. 

Burns,  Barbara  Ann,  115,  181,  195,  196-197. 

Butler,  Bryan  J.,  237,  239,  240,  242,  243,  244,  245,  246, 
261. 

Butman,  Stan,  226. 


Cain,  Dan  L.,  150,  151. 

California  Institute  of  Technology  (Caltech),  36,  40- 
41,  61,  72,  105,  205-206,  261;  relations  with  Jet 
Propulsion  Laboratory,  110.  See  also  Owens  Valley 
Observatory, 


289 


290 


TO  SEE  THE  UNSEEN 


Callisto.  See  under  Galilean  moons. 

Gallon,  Michael,  x. 

Cambridge  Radio  Observatory  Committee.  See  CAM- 
ROC. 

Campbell,  Donald  B.  "Don",  60, 93,  102, 105, 115,  124, 
145-147,  150,  151,  154,  158,  161,  162,  174,  179,  180, 
181,  183,  184,  186,  190,  191,  194,  195,  196,  197,  201, 
202,  203,  204,  207,  208,  209,  210,  215,  213-214,  216, 
218,  219,  220,  221,  224,  226,  229,  234,  235,  237,  239, 
241,  242,  245,  261. 

CAMROC  (Cambridge  Radio  Observatory 
Committee),  63,  71-74.  See  aisoNEROC. 

Carpenter,  Roland  L.,  50,  51,  52,  61,  106,  119,  135, 
138. 

Cassini  project,  203,  230,  238. 

Center  for  Radiophysics  and  Space  Research  (CRSR) . 
See  under  Cornell  University. 

Chandler,  John  F.,  125,  201,  212. 

Chapman,  Clark,  255. 

Chisholm,  James,  59. 

Chodas,  Paul,  256. 

Clark,  P.  E.,  243. 

Clarke,  Arthur  C.,  255. 

Clegg.JohnA.,  14,  15,20. 

Clemence,  Gerald,  M.,  47. 

Clementine  spacecraft,  245,  254. 

Colombo,  Giuseppe  "Bepi",  119. 

Comets,  215-221;  as  radar  targets,  215;  International 
Halley  Watch,  220-221;  Austin,  217,  218; 
Churyumov-Gerasimenko,  217,  218;  d'Arrest,  216; 
Encke,  216,  217,  218;  Grigg-Skjellerup,  216,  217, 
218;  Halley,  220-221;  Honda-Mrkos-Pajddusakova, 
221;  IRAS-Araki-Alcock,  218-220;  Kohoutek,  216; 
Shoemaker-Levy,  256;  Sugano-Saigusa-Fujikawa,  220. 

Communications:  CODORAC,  36-37;  NOMAC  (NOise 
Modulation  And  Correlation),  30-31,  32;  meteor 
burst,  20;  Rake,  30-31;  Moon-bounce,  by  ham  radio 
operators,  146. 

COMPLEX  (Committee  on  Planetary  and  Lunar 
Exploration).  See  under  National  Academy  of 
Sciences. 

Cook,  Allan  F.,  214. 

Cornell  University,  58,  61, 62,  74,  75,  88, 89, 90, 92, 93, 
96,  97,  98,  99,  102,  103,  109,  152;  Cornell  University, 
Center  for  Radiophysics  and  Space  Research 
(CRSR),  89,  90,  98,  100;  Cornell-University  of 
Sydney  agreement,  99-101. 

COSPAR  (Committee  on  Space  Research),  47,  48. 

Counselman,  Charles  C.,  Ill,  120. 

Cuzzi,  Jeffrey  N.,  215. 

D 

Daddario,  Emilio  Q.,  101. 
Dallas,  Saterios  Sam,  194. 
Danforth,  Haines,  125. 
Davenport,  Wilbur  B.,  Jr.,  30,  56. 
Davies.JohnG.,  15,  16. 
Davis,  John  W.,  104. 
de  Dominicis,  Cyrano,  126-127. 


Deep  Space  Network,  36,  37, 63,  70, 104, 106, 109,  1 10, 
111,  151,  155,  173,  184,  187,  188,  193,  225,  229; 
Advisory  Group,  225;  Voyager  upgrade,  228;  HA- 
DEC  antenna  (Pioneer),  37,  39-40,  49;  AZ-EL  anten- 
na (Echo),  38,  39-40,  49;  Venus  Station  (DSS-13), 
108,  110;  Mars  Station  (DSS-14),  67,  72,  75,  96,  104, 
105-109,  110,  121,  123,  135,  137,  139,  147; 
Tidbinbilla  facility,  155.  See  also  Goldstone  radar; 
Bistatic  radar:  Goldstack. 

Dewitt,  John  H.,  Jr.,  6,  7,  9,  10,  12,  32. 

Dicke  Panel.  See  under  Radio  astronomy. 

Downs,  George  S.,  109,  115,  158,  161,  162,  225-226, 
238,  263. 

Drake,  Frank,  75,  93,  94,  96,  98,  231. 

Dyce,  Rolf,  75,  92,  93,  96,  119,  121,  124,  133,  135,  139, 
146,  150,  151,  158,  180-181. 


Effelsberg  (Germany)  radio  telescope,  76,  259. 
EISCAT  (European  Incoherent  Scatter  Association), 

231,  232. 

Elachi,  Charles,  227. 
Ellyett,  Clifton  D.(  15,  20. 

Eshleman,  Von  R.,  19-20,  55,  57,  58,  61,  155,  209. 
Europa.  See  under  Galilean  moons. 
European  Space  Agency,  220. 
Evans,  John  V,  23-24,  34-35,  41,  42,  44,  49,  55,  56,  112, 

113. 

Evans,  W.  E.,  Jr.,  19. 
Explorer  probes,  155-156. 
Ezell,  Edward  Clinton,  158,  159. 
Ezell,  Linda  Neuman,  158,  159. 


Farr,  Tom  G.,  195. 

Ferrell,  Oliver  Perry,  17. 

Ferric,  Gustave,  60. 

Findlay.John,  77. 

Fink,  Donald  G.,  9. 

Fjeldbo  (later  Lindal),  Gunnar,  155. 

Fleischer,  Robert,  81. 

Ford,  Peter  G.,  166,  174,  195,  202,  245. 

Forni,  Antonia,  216. 

Franklin,  Fred  A.,  214. 

Fricke,  Walter,  48,  49. 

Friedman,  Louis  D.,  178,  183. 


Galilean  moons,  206,  208,  210-211;  radar  signatures 
of,  207-208;  radar  backscattering  models  of,  208-212; 
radar  echoes  and  "weak  localization,"  211;  Callisto, 
105, 112,  206,  208-210;  Europa,  207-210;  Ganymede, 
105,  112,  206-210;  lo,  207,  210.  See  also  Range- 
Doppler  mapping. 

Galileo  mission,  184, 187,  200,  193,  203,  177,  212;  229. 

Gallagher,  Philip.  B.,  58. 

Ganymede.  See  under  Galilean  moons. 


PLANETARY  RADAR  ASTRONOMY  PUBLICATIONS 


291 


Gehrels,  Tom,  123,  222,  224,  248. 

General  Theory  of  Relativity,  9,  112,  117,  126;  radar 
test  of,  126-129. 

Gerks,  Irvin  H.,  25. 

Gerpheide.John  H.,  179,  194. 

Gillmor,  C.  Stewart,  18-19. 

Gihnore,  Alan,  217. 

Gold,  Thomas,  32,  57,  59,  75,  89-90,  91,  95,  96,  98,  99, 
100,  101,  140,  152,  153. 

Goldberg,  Leo,  66,  69. 

Goldreich,  Peter,  119. 

Goldstein,  Richard  M.  "Dick",  39,  40,  52,  61,  104,  105, 
106,  109,  110,  115,  119,  120-121,  123,  135,  137,  139, 
143,  147,  151,  152,  158,  174,  176,  179-180,  183-184, 
206,  209,  212,  213,  214,  219,  220,  222,  224,  226,  237, 
242,  263. 

Goldstein,  Samuel,  40. 

Goldstone  radar,  149,  152,  155,  156,  157,  158,  160, 
161,  174,  177,  180,  205,  206,  225;  attempted 
upgrade,  225-230;  Planetary  Radar  Science  Review 
Committee,  229-230;  Goldstone  Solar  System  Radar 
(GSSR),  225,  227-228;  Echo  station  (DSS-12),  180; 
Venus  station  (DSS-13),  180;  Mars  Station,  150,  180, 
199,  259.  See  also  Deep  Space  Network. 

Golomb,  Solomon,  39,  45-46. 

Goody,  Richard  M.,  163. 

Goodyear  Aerospace  Corporation,  168,  184,  185,  192- 
193. 

Gordon,  William  E.  "Bill",  88,  89,  91,  94,  95,  98,  99. 

Green,  Paul  E.,  Jr.,  30,  31,  32,  33,  36,  41,  52,  55,  56,  59, 
61,  131,  132. 

Green,  Richard  R.  "Rick",  109,  209,  225,  226. 

Greenstein  Panel.  See  under  Radio  astronomy. 

Grossman,  Arie,  237. 

Guerlac,  Henry,  1. 

Gurrola,  Eric,  210. 


H 


Hagfors,  Tor,  56, 101, 159, 162,  209,  213,  227,  229,  231, 

232,  233. 

Haldeman,  Albert,  246. 
Hapke,  Bruce,  211. 
Harang,  Leiv,  21. 
Hargreaves,  J.  K.,  22-23. 
Harmon,  John  K.,  115,  195,  196,  212,  221,  239,  241, 

242,  245,  246,  259. 

Harrington,  John  V.  "Jack",  55,  56,  59. 
Harris,  Sam,  145,  146. 
Harvard   University,   67,    71,    73,    76,   90;   College 

Observatory,  17,  67. 
Harvard-Smithsonian  Astrophysical  Observatory,  219; 

Center    for    Astrophysics,     125,     212.     See    also 

Smithsonian  Institution:  Smithsonian  Astrophysical 

Observatory. 
Hawkins,  G.  S.,  20. 
Haworth,  Leland  J.,  69,  81,  97. 
Haystack  Observatory,  62,  63,  65, 66,  67,  75,  76, 92, 93, 

94,  121,  122,  123,  127,  129,  134-135,  141,  150,  152, 

156,  157,  158,  183,  206.  See  also  Lincoln  Laboratory; 

NEROC. 


Head,  James  W.,  Ill,  186,  190-191,  194-196,  242-243. 

Helin,  Eleanor,  222,  250. 

Hellgren,  Gotha,  20. 

Helliwell,  Robert  A.,  18. 

Herlofson,  Nicolai,  14,  15. 

Herman,  Daniel  H.  "Danny",  167,  177,  180,  183. 

Hess,  Harry  H.,  101,  102. 

Hey,  James  S.,  13. 

Hibbs,  Albert  R.  "AT,  39. 

Higgins,  Charles  S.,  21-22. 

Hine,  Alice,  197,201. 

Hornig,  Donald,  100. 

Housman,  W.  B.,  20. 

Hudson,  R.  Scott,  240,  241,  252,  254,  259. 

Hughes,  Thomas  P.,  x. 

Hughes  Aircraft  Company,  185,  188,  192-193,  194. 

Hunt,  Daniel,  103. 

Hunten,  Donald  M.,  163,  235. 


I 


Imrie,  K.S.,  113. 

Ingalls,  Richard  P.  "Dick",  56,  85,  141-143,  150,  206, 

242. 
Institute    of  Radio    Engineering    and    Electronics 

(IREE),  45,  46,  113,  114,  118.  See  also  Yevpatoriya 

tracking  station. 

International  Solar  Polar  Mission  (ISPM),  188. 
International  Astronomical  Union  (IAU),  61,  62,  203, 

263;  adopts  radar  names  for  Venus  features,  175-176. 

See  also  Astronomical  Unit, 
lo.  See  under  Galilean  moons. 


I 


Jaffe,  Richard,  36. 

Jodrell  Bank  Experimental  Station,  13,  14,  15,  16,  20, 
21,  43-44,  59,  61,  76,  92,  260;  Venus  radar  at,  33-35; 
250-ft  (76-meter)  telescope,  33;  end  of  radar  astron- 
omy at,  112-115.  See  also  Lovell,  Sir  A.  C.  Bernard. 

Jones,  Harold  Spencer,  46,  47,  48. 

Jones,  Tom,  98,  99. 

Jet  Propulsion  Laboratory  (JPL),  36-40,  104,  125,  150, 
162,  169,  178,  179,  180,  183,  184,  185,  186,  187,  188, 
192,  193,  194,  205,  206,  213;  relations  with  Caltech, 
110;  Friend  of  the  Radar,  227;  Office  of  Space 
Science  and  Instruments,  227;  rivalry  with  MIT  over 
Pioneer  Venus,  172;  ephemeris  activity,  225. 

Jupiter,  120-121. 

Jurgens,  Raymond  F.  "Ray",  93, 109,  110,  111,  115, 124, 
139,  140,  143,  146,  147,  150,  180,  219-220,  222-223, 
225,  226,  237,  243,  246,  248,  250,  256,  261,  263. 

K 

Kamoun,  Paul  G.  D.,  216,  217,  218. 
Kauffman,  Herbert  P.,  7. 
Keesey,  Mike,  220. 
Keff,  Frank  J.,  21-22. 
Keller,  Carl,  171. 
Kildal,  Per-Simon,  232. 


292 


TO  SEE  THE  UNSEEN 


Kingston,  Robert  H.  "Bob",  31,  55. 

Kliore,  Arvydas,  123,  150,  151. 

Kotelnikov,  Vladimir  A.,  45,  46,  50,  113,  114,  118-119, 
120,  191. 

Kovalevsky,  Jean,  48. 

Kozak,  Richard,  195. 

Krige.John,  xi,  263. 

Kuhn,  Thomas  S.,  xii,  117-118,  263;  "normal  science," 
117-118;  scientific  paradigm  defined,  117.  See  also 
radar  astronomy:  Kuhn's  notion  of  paradigm  in. 


Laderman,  Al,  178. 

Lalonde,  L.  Merle,  96. 

Landmark,  B.,  21. 

Liller,  William,  47. 

Lilley,  A.  Edward  "Ed",  47,  63, 66, 67,  71,  72,  73, 82, 83. 

Lincoln  Laboratory,  27,  28,  29,  30,  31,  32,  33,  39,  61, 

63,  65,  66, 67,  71,  73,  76,  79, 80, 81, 92, 121, 122, 126, 

127,  219;  radar  astronomy  summer  course,  55-56;  El 

Campo  (Texas)  solar  radar  facility,  55,  58,  62,  92.  See 

also  MIT;  Sun. 
Long,  Franklin  A.,  97. 
Long-Distance   Space   Communication   Center.    See 

Yevpatoriya   tracking  station;   Institute  of  Radio 

Engineering  and  Electronics. 
Love,  Alan,  96,  231. 
Lovell,  Sir  A.  C.  Bernard,  13,  14,  15,  16,  20,  23,  24,  34, 

35,44,63,  112,  113,  114,  115. 
Low,  Ward,  89. 
Low,  George,  M.,  85. 

M 

Magellan  (VOIR  and  VRM),  162,  165,  167,  169,  226, 
264;  origins  as  VOIR,  177-178;  defining  the  VOIR 
mission,  184-185;  VOIR  Science  Working  Group, 
179-180,  185;  VOIR  cancelled,  187;  renamed  VRM, 
187-188,  189;  defining  the  VRM  mission,  191-192; 
organization  of  the  science  teams,  186;  radar  con- 
tract awarded,  192-193;  SAR  mapper,  178,  184-185; 
in-house  versus  contracting  out,  184-185;  named 
Magellan,  192;  delayed  launch  of,  193-194, 200;  man- 
agement changes,  199;  technology  borrowed  from 
other  NASA  flight  missions,  178-179,  185,  188,  193, 
199,  200;  and  shift  of  planetary  radar  astronomy 
toward  geology,  177,  179-180;  191,  194-196,  203; 
interpretation  of  radar  images,  185,  200-201;  role  of 
ground-based  radars  in,  201;  space-based  versus 
ground-based  radar,  180,  183-184;  impact  on 
ground-based  radar  astronomy,  203-204;  and  Venus 
geology,  194,  195-197;  as  Big  Science,  177,  191-192, 
202-203;  NAIC-Brown  University  agreement,  196.  See 
also  Microsymposia;  Venera. 

Malin,  Michael  C,  180. 

Mallow,  Dick,  233. 

Manning,  Lawrence  A.,  19. 

Mansfield  Amendment,  80,  87,  94,  97. 

Marconi,  Guglielmo,  1. 


Mariner  missions,  106,  108,  157,  178,  186,  242,  243, 
244,  246;  Mariner  1  and  2,  39,  49;  Mariner  4,  108, 
154;  Mariner  5,  150,  151,  163;  Mariner  6,  154; 
Mariner  7, 154;  Mariner  9, 154, 185;  Mariner  10, 109. 

Marov,  M.  Ya.,  176. 

Mars,  124;  topography,  238-239,  242;  radar  observa- 
tions of  polar  ice  caps,  238-242. 

Marsden,  Brian  G.,  48,  216,  217,  219,  220,  222,  223- 
224. 

Martel,  Hardy,  40. 

Martin  Marietta  Aerospace,  178,  188. 

Martin, James,  161. 

Maser,  31-32,  40,  65. 

Massachusetts  Institute  of  Technology.  SeeMIT. 

Masursky,  Harold  "Hal",  163,  164,  169,  170,  174,  176, 
179,  183,  186,  190,  191,  194. 

Matson,  Dennis  L.,  238. 

McAfee,  Walter  S.,  7. 

McGill,  George  E.,  174. 

McGuire,  William,  89. 

McKay,  John  S.,  178. 

McKinley,  Donald  W.  R.,  16,  17,  20. 

Melbourne,  Bill,  150. 

Menzell,  Donald,  66. 

Meos,  Johan,  20. 

Mercury:  first  detected  by  radar,  118-119;  period  of 
rotation  determined,  119-120;  topography,  242-243; 
discovery  of  polar  ice  242-246;  confirmation  of  polar 
ice  at  Arecibo  Observatory,  245. 

Messel,  Harry,  99. 

Meteors,  12-20,  88.  See  also  Communications:  meteor 
burst;  U.S.  Army:  meteors. 

Microsymposia,  194,  197;  origins,  190-191.  See  also 
Brown  University;  Vernadsky  Institute. 

Mikhailov,  Aleksandr  A.,  48. 

Millman,  Peter  M.,  16,  20. 

Millstone  radar  observatory,  29,  30,  31,  55,  63,  67,  88, 
101,  150;  Venus  (1958),  30-33.  See  also  Lincoln 
Laboratory. 

MIT:  Center  for  Space  Research,  56,  73,  172,  186; 
Draper  Laboratory,  125;  Electronics  Systems 
Laboratory,  163;  Radiation  Laboratory,  5-6,  9; 
Radiation  Laboratory  of  Electronics,  28.  See  also 
Lincoln  Laboratory. 

Mofenson,  Jack,  7. 

Montgomery,  G.  Franklin,  25. 

Moon,  92,  132-135,  245;  bistatic  radar  studies  of,  104, 
111-112,  113-114;  Operation  "Haymoon,"  143; 
Goldstack,  111-112;  jodrell  Bank-USSR  (Yevpa- 
toriya), 113-114.  See  also  Radar  interferometry: 
Operation  "Haymoon";  Radar  range-Doppler  map- 
ping: Moon. 

Moore,  Henry  John,  II,  169,  203,  226,  239. 

Morris,  George  A.,  Jr.,  109,  206,  212,  213. 

Morrison,  David,  235,  255. 

Morrison,  Philip,  57. 

Mouginis-Mark,  Peter,  238. 

Muhleman,  Duane  O.  "Dewey",  40,  47,  48,  50,  61,  106, 
128-129,  150,  227,  230,  236,  238,  239,  240,  241,  242, 
243,  244,  245,  246,  259,  261. 


PLANETARY  RADAR  ASTRONOMY  PUBLICATIONS 


293 


Murray,  Bruce  C.,  110,  244. 
Murray,  William  A.  S.,  22,  23. 
Mutch,  Thomas,  226. 

N 


NAIC  (National  Astronomy  and  Ionospheric  Center) , 
104,  147,  181,  196,  231,  233.  See  also  Arecibo 
Observatory. 

NASA,  72,  77,  81,  83,  85,  87,  88,  92,  93,  106,  149,  153, 
155,  163,  166,  169,  172,  177,  179,  180,  183,  184-185, 
186,  192,  193,  194,  203,  213,  255-256,  264,  265;  bud- 
get, 187;  Advanced  Programs,  166-167;  Ames 
Research  Center,  163,  171,  178;  Discovery  program, 
259;  Goddard  Space  Flight  Center,  163;  Lunar  and 
Planetary  Missions  Board,  163;  Office  of  Space 
Science,  39,  226;  planetary  programs  office,  213.  See 
also  Arecibo  Observatory:  NASA-NSF  agreement;  Jet 
Propulsion  Laboratory. 

National  Academy  of  Sciences,  168;  Space  Science 
Board,  57,  163;  COMPLEX  (Committee  on 
Planetary  and  Lunar  Exploration),  180,  190;  Bahcall 
Committee,  235. 

National  Aeronautics  and  Space  Administration.  See 
NASA. 

National  Astronomy  and  Ionospheric  Center.  See 
NAIC. 

National  Bureau  of  Standards,  62-63,  88;  Central 
Radio  Propagation  Laboratory  (Sterling,  VA),  18, 
22,  25,  58,  61;  Jicamarca  facility,  55,  63,  88,  101. 

National  Radio  Astronomy  Observatory  (NRAO), 
Green  Bank  radio  telescope,  58,  67,  69,  70,  259. 

National  Research  Council  (Canada),  260. 

National  Science  Foundation  (NSF),  69,  70,  73,  74,  75, 
76,  77,  79,  80, 81, 82, 83,  84,  87, 88, 94, 96, 97, 98, 99, 
100,  101,  205,  233.  See  also  Arecibo  Observatory: 
NASA-NSF  agreement 

Naugle,  John  E.,  81,  101,  161. 

NEROC  (Northeast  Radio  Observatory  Corporation) , 
73,  74,  75,  76,  77,  78,  79,  80,  81,  82,  83,  84,  85,  99, 
102,  177.  See  also  Haystack  Observatory;  CAMROC. 

Newell,  Homer  E.,  Jr.,  58. 

Nichols,  Benjamin  "Ben",  88. 

Nickle,  Neil,  199. 

Northeast  Radio  Observatory  Corporation.  See 
NEROC. 

NSF.  See  National  Science  Foundation. 

o 

O'Handley,  D.  A.,  150. 

Orlen.Joel,  72. 

Ostro,  Steven  J.  "Steve",  115,  208,  209,  210,  211,  212, 

214,  215,  216,  221,  222,  224,  226,  227,  228,  234,  237, 

239,  248,  249,  250,  251,  252,  254,  256,  257,  259,  261, 

263. 
Owens  Valley  Observatory,  70,  72,  73,  75,  81;  Westroc, 

73,  75.  See  also  California  Institute  of  Technology. 


Paige,  David  A.,  244,  245. 

Palomar  Planet-Crossing  Asteroid  Survey  (PCAS) ,  222. 

Parkes  radio  telescope,  107. 

Parsons,  S.  J.,  13. 

Pawsey,  J.  L.,  22,  31. 

Peale,  StantonJ.,  119,  120. 

Perillat,  Phil,  241. 

Peters,  Kenneth  J.,  211. 

Peterson,  Allen  M.,  19. 

Petrosian,  Vahi,  92. 

Pettengill,  Gordon  H.,  31,  35,  36, 41,  42, 48,  55,  56,  72, 
75,  85,  91-92,  93,  98,  101,  104,  112,  115,  119,  121, 
123,  124,  127,  132,  133,  134-135,  139,  141,  143,  150- 
152,  158-159,  162-164,  166,  167,  170-174,  176,  177, 
179,  181,  183-184,  185-186,  187-188,  190,  191,  193- 
195,  201-202,  207,  208,  213,  214,  215,  216,  224,  226, 
229,  237,  248,  261. 

Philco  Corporation,  168. 

Phillips,  J.W.,  13. 

Pickering,  William,  36. 

Pineo,  Victor  C.,  18,  55. 

Pioneer  Venus,  162,  177,  179,  180,  184,  186,  190,  193, 
194;  origins,  162-163;  Purple  Book,  163-165;  Orange 
Book,  166;  radar  mapper  experiment,  171-174. 

Planetary  Radar  Working  Group,  226. 

Planetary  radar  ephemerides,  93,  130,  212;  Planetary 
Ephemeris  Program  (PEP),  123-126,  139,  150,  172, 
212,  223;  JPL  Development  Ephemeris  (DE),  125- 
126. 

Polarization:  right-handed  and  lefthanded,  207; 
"expected"  and  "unexpected"  sense,  207;  circular 
polarization  inversion,  207-208. 

Pollack,  James  B.,  152,  214,  215. 

Ponsonby.John  E.  B.,  44,  113,  114. 

Posner,  Edward  C.  "Ed",  111. 

Prentice,  J.  P.  Manning,  14,  15. 

Price,  Robert  "Bob",  30,  31,  32,  33,  35,  41,  42,  55,  56, 
90. 

Price,  Derek  J.  De  Solla,  ix,  xi. 

Project  Echo,  38,  39. 

Project  Needles,  63,  141. 

Project  Diana.  See  under  U.S.  Army. 

Project  West  Ford.  See  Project  Needles. 

Purcell,  Edward  M.,  77. 


Rabe,  Eugene,  47,  48,  49. 

Radar:  origins  of  in  radio,  1;  and  magnetron  develop- 
ment in  Britain,  2,  4-6;  Tizard  Mission,  4-5;  Chain 
Home,  2-4;  DEW  Line,  29,  65;  BMEWS,  29,  45,  65; 
monostatic  versus  bistatic,  39.  See  also  Synthetic 
Aperture  Radar  (SAR). 


294 


TO  SEE  THE  UNSEEN 


Radar  astronomy:  and  misinterpretations  of  measure- 
ments, 151-153,  158-159;  Radar  Astronomy,  56; 
Endicott  House  Conference  on  ( 1959) ,  57-60;  driven 
by  technology,  259,  264;  as  problem-solving,  52,  117- 
118,  162,  204-205,  246;  and  epistemological  versus 
scientific  problems,  117-118,  259;  at  intersection  of 
engineering  and  science,  263-264;  as  Little  Science, 
93-94,  106,  109-111,  115,  203,  205,  262;  and  Big 
Science,  149,  162,  263-264;  social  construction  of, 
264;  Kuhn's  notion  of  a  scientific  paradigm  in,  117- 
118,  125-126,  129;  growth  of  literature,  261-262;  util- 
itarian tendency  of,  264;  NASA  mission  orientation 
of,  205,  215,  264;  MIT  Lincoln  Laboratory  summer 
course  in,  55-56;  academic  training  in,  92-93,  105- 
106,  205,  261;  at  JPL,  106,  109-111,  206;  limits  to 
growth  in,  262-263,  265;  and  geology,  225-226;  and 
computers,  124-125,  283;  at  Arecibo  Observatory 
and  JPL  Goldstone  compared,  265,  228,  229;  as  a 
space-based  endeavor,  203-204;  future  of,  259-260. 
See  also  Kiihn,  Thomas;  Planetary  radar 
ephemerides. 

Radar  geology,  167.  See  also  Radar  astronomy:  and 
geology. 

Radar  interferometry,  93,  141-147;  Operation 
"Haymoon,"  143;  Hayford,  141,  143;  at  Arecibo 
Observatory,  143,  145-147;  and  observations  of  aster- 
oid Toutatis,  252. 

Radford,  William  "Bill",  127. 

Radio  astronomy,  62,  69,  91,  101, 105,  125,  141,  259;  at 
Haystack  Observatory,  55,  63,  66^7,  84-85;  at  JPL 
Goldstone,  226;  Whitford  Report,  67,  69-71,  77; 
Dicke  Panel  (1969),  79,  81,  101;  Dicke  Panel  (1967), 
75-76,  96,  97;  Greenstein  Panel  (1971),  82;  spectral 
lines,  141;  Very  Long  Baseline  Interferometry 
(VLBI),  125,  174;  SETI  (Search  for  Extra-Terrestrial 
Intelligence),  226,  235.  See  also CAMROC;  NEROC. 

Radio  Corporation  of  America  (RCA),  3,  45. 

Radome,  65,  72-73,  78. 

Rainville,  Louis  P.  122,  123,  125. 

Randall,  John  F,  4. 

Range-Doppler  mapping:  planetary,  129-131;  at 
University  of  Michigan,  131;  first  applied  to  Moon, 
132-135,  143;  lunar,  114;  first  applied  to  Venus,  135- 
141;  of  Venus,  93,  101-102,  103,  107,  180-183;  of 
Venus  from  space,  163-165;  with  SARs,  167-168;  of 
Galilean  moons,  212. 

Rasool,  S.  Ichtiaque,  213. 

Rechtin,  Eberhardt  "Eb",  36-37,  39,  41,  47,  105,  105, 
106,  110,  111,225. 

Reichley,  Paul,  128. 

Reintjes.J.  F.,  163. 

Renzetti,  Nicholas  A.  "Nick",  105,  204,  226-227,  228, 
229,  236,  238,  252. 

Ripley,  S.  Dillon,  77,  78,  79,  81,  62. 

Roberts,  Morton  S.,  231. 

Roemer,  Elizabeth,  122,  123. 

Roger,  R.  S.,  44. 

Rogers,  Alan  E.  E.,  56,  141-143. 

Roman,  Nancy  G.,  58,  70. 

Rose,  Jim,  178. 

Rossi,  Bruno  B.,  57,  58,  58. 


Roth,  Ladislav,  162. 

Royal  Radar  Establishment  (Malvern),  59. 

Ryle,  Sir  Martin,  63,  69,  141. 

Rumsey,  Howard  C.,  Jr.,  109,  138-139,  174. 


Sadler,  D.  H.,  48. 

Sagan,  Carl,  123,  152,  154,  256. 

SAGE  (Semi-Automatic  Ground  Environment),  65. 

Sanchez,  Andy,  121. 

SAR.  See  Synthetic  Aperture  Radar. 

Sato,  Takoshi,  40. 

Saturn:  Arecibo-Goldstone  experiment  on  rings  of, 

213-214;  radar  limits  structure  of  rings,  214-215; 

strange  radar  echoes  from  rings,  213;  Titan,  236-238. 
Saunders,  R.  Stephen,  169,  178,  180,  185,  191,  194. 
Schaber,  Gerald  G.,  169,  174,  179,  186,  194,  195,  201, 

238-239,  243. 
Schmidt,  R.  F,  168. 
Schubert,  Gerald  "Gerry",  162,  185. 
Scott,  Hugh,  80. 
Seamans,  Robert  C.,  Jr.,  71-72. 
SEASAT,  169,  178-179,  184,  185,  188,  199. 
Sebring,  Paul  B.,  79. 
Sekanina,  Zdenek,  216,  219,  220. 
Senske,  David  A.,  196. 
SETI  (Search  for  Extra-Terrestrial  Intelligence).  See 

under  Radio  astronomy. 
Shain,  Alex,  21-22. 
Shapiro,  Irwin  I.,  47,  48,  52,  93,  112,  119,  121,  124, 

126-129,  150,  172,  174,  201,  206,  212,  216,  219,  220, 

223-224,  227,  234. 
Shoemaker,  Carolyn,  228. 

Shoemaker,  Eugene,  169,  209-210,  211,  222,  228. 
Simpson,  Richard  A.  "Dick",  155,  156,  161,  177,  186, 

201-203,  210,  240,  261. 
Slade,  Martin  A.  "Marty",  150,  227,  237,  239,  240,  242- 

246,  261. 

Smith,  William  B.  "Bill",  32,  42,  52,  147,  150,  242. 
Smithsonian    Air    and    Space    Museum.    See   under 

Smithsonian  Institution. 
Smithsonian   Astrophysical   Observatory.    See  under 

Smithsonian  Institution. 
Smithsonian  Institution,  77,  78,  79,  80,  81,  82,  177;  Air 

and  Space  Museum,  193;  Smithsonian  Astrophysical 

Observatory  (SAO),  67,  71,  73,  76,  77,  80,  119,  152, 

214;     STAG     (Smithsonian    Telescope    Advisory 

Group),    79,    81.    See    also   Harvard-Smithsonian 

Astrophysical  Observatory. 
Social  construction  (of  science  or  technology),  x.  See 

also  Radar  astronomy:  social  construction  of. 
Soderblom,  Lawrence  A.,  105,  186. 
Soffen,  Gerald,  155. 
Space  Science  Board.  See  under  National  Academy  of 

Sciences. 

Space  Technology  Laboratories  (STL),  47,  112. 
Spaceguard.  See  under  Asteroids. 
Spacewatch.  See  under  Asteroids. 
Spear,  Anthony  J.,  179. 
Spencer,  Nelson  W.,  163. 


PLANETARY  RADAR  ASTRONOMY  PUBLICATIONS 


295 


Stacy,  Nicholas  John  Sholto  "Nick",  195,  197,  201,  245. 

Standish,  E.  Miles,  Jr.,  125,  225. 

Stanford  Center  for  Radar  Astronomy  (SCRA).  See 
under  Stanford  University. 

Stanford  Research  Institute  (SRI).  See  under  Stanford 
University. 

Stanford  University,  61,  62,  153,  155;  "bistatic  radar," 
155,  162,  165,  202;  Stanford  Center  for  Radar 
Astronomy  (SCRA),  154-156,  186,  205;  Stanford 
Radio  Propagation  Laboratory,  18-19;  Stanford 
Research  Institute  (SRI),  58,  62,  92,  155. 

Stelzried,  Charles  T,  40. 

Stetson,  Paul,  233. 

Stevens,  Robertson  "Bob",  36,  37,  39,  42. 

Stewart,  G.  S.,  13. 

Stodola,  King,  7,  9. 

Stroke,  George,  127. 

Sulzer,  Peter  G.,  25. 

Sulzer,  Michael  P.,  241,  245. 

Sun:  astronomy  of,  70;  radar  studies  of  70,  92.  See  also 
International  Solar  Polar  Mission  (ISPM);  Lincoln 
Laboratory:  El  Campo  (Texas)  solar  radar  facility. 

Swenson,  Byron,  178. 

Swords,  Sean  S.,  1,  4. 

Synthetic  Aperture  Radar,  167-168,  178,  179,  185,  186, 
192-193,  195;  AIR-SAR  (NASA  JPL  airborne  SAR), 
211;  Shuttle  Imaging  Radar  (SIR-A),  178. 


Taylor,  G.  N.,  44,  49. 

Telecommunications  Research  Establishment,  88. 

Terman,  Frederick  E.,  18. 

Thompson,  Thomas  W.  'Tommy",  92,  93,  133,  135, 

143,  145,  150,  153,  169,  170,  183,  199,  227,  239. 
Thompson,  Frank,  Jr.,  81-82. 
Thomson,  John  H.,  24,  44,  49,  113,  114. 
Titan.  See  under  Saturn. 
Tizard,  Henry,  4. 
Townes,  Charles,  127. 
Traxler,  Jerome  Bob,  233. 
Tuve,  Merle  A.,  3. 
Tyler,  G.  Leonard  "Len",  155,  156,  158,  159,  161,  165, 

177,  186,  201-203,  226,  240. 


U 


U.S.  Air  Force,  80,  83,  85,  168;  Cambridge  Research 
Center  (also  Cambridge  Research  Laboratories  and 
today  Phillips  Laboratory),  18,  20,  24,  28,  58,  89; 
Office  of  Scientific  Research,  89,  97;  Research  and 
Development  Command  (EOARDC),  33. 

U.S.  Army,  168;  Corps  of  Engineers,  90;  Signal  Corps, 
6-9,  28;  radar  research,  5;  Project  Diana,  6-9,  32; 
Evans  Signal  Laboratory,  6,  7;  and  meteors,  17-18. 

U.S.  Geological  Survey  (USGS),  105,  162-164,  167, 
169, 174, 179, 186,  195,  203;  Branch  of  Astrogeologic 
Studies,  169,  186. 

U.S.  Navy:  Naval  Observatory,  93,  125,  150;  Naval 
Research  Laboratory  (NRL),  3,  5,  6,  24,  25,  31,  58, 
61;  NRL  Sugar  Grove  facility,  62,  67-69,  71, 89;  Office 
of  Naval  Research,  28,  33,  72,  75,  87,  88,  168. 


Udall,  Morris  K.,  81. 

Union  Radioscientifique  Internationale  (URSI),  60- 

62,  203,  263. 

University  of  Illinois,  Control  Systems  Laboratory,  168 
University  of  Michigan,  169;  Environmental  Research 

Institute  of  Michigan   (ERIM),    178,  Venus  radar 

development,   163;  Willow  Run  Research  Center, 

168. 


Valley,  George  E.,  Jr.,  9,  28. 

Venera:  Venera  4,  150,  163;  Venera  7,  165;  Venera  15 
and  16,  186,  189-191,  194,  197. 

Venus,  30-52,  106, 109,  180-183,  246;  Millstone  (1958), 
30-33;  Jodrell  Bank  (1959),  33-35;  Millstone  (1959), 
35-36;  JPL  (1961),  39-41;  Millstone  (1961),  41-42,  44; 
Jodrell  Bank  (1961),  44-45;  RCA  (1961),  45;  Soviet 
Union  (1961),  45-46;  priority  of  first  detection,  41; 
radar  determination  of  retrograde  rotation  of,  49-52; 
radius  determined  by  radar,  150-151;  radar  identifi- 
cation of  topography,  135-140;  geology  of,  139,  174- 
175.  See  also  Pioneer  Venus;  Magellan;  Radar  range- 
Doppler  mapping;  Synthetic  Aperture  Radar. 

Vernadsky  Institute,  190,  191,  194,  197;  Planetology 
Laboratory,  190.  See  also  Brown  University; 
Microsymposia. 

Very  Large  Array  (VLA),  69,  70,  72,  73,  74,  75,  81,  82, 
228,  230,  236;  Voyager  upgrade,  236. 

Very  Long  Baseline  Interferometry  (VLBI) .  See  under 
Radio  astronomy. 

Vesecky,  John  F.,  186,  201. 

Victor,  Walter  K.  "Walt",  36,  37, 39, 40, 42, 50,  106, 110, 
225. 

Viking,  83,  85,  105,  106,  108-109,  129,  153-162,  264, 
177, 178, 188, 194,  205;  selection  of  landing  site,  154, 
156-158,  160-162;  role  of  radar  in,  161-162. 

Villard,  Oswald  G.,  Jr.,  19,  58. 

von  Braun,  Werner,  102. 

von  Hoerner,  Sebastian,  231. 

Vorder  Brueggie,  Richard  W.,  196. 

Voyager  mission,  106,  153,  188,  193,  203,  209,  210, 
228,  236-237,  248,  250;  as  Mariner  Jupiter-Saturn, 
108-109,  213.  See  alsoVery  Large  Array;  Deep  Space 
Network. 


W 


Wall,  Steve,  195. 

Wasserburg,  Gerald  J.,  180. 

Watson,  Kenneth,  244. 

Watson-Watt,  Sir  Robert,  2,  3. 

Webb,  Earle  L.  R.,  16. 

Webb,  Harold  D.,  7. 

Weiss,  Herbert  G.  "Herb",  29,  55,  59,  76,  78,  83. 

Western  Union  (telegraph  company),  263,  265. 

Westinghouse,  168. 

Whipple,  Fred  L.,  15-16,  17,  77,  81,  216. 

Whitford  Report.  See  under  Radio  astronomy. 

Wiesner,  Jerome,  72. 

Wilhelms,  Don  E.,  153. 

Wilkins,  George  A.,  48. 


296  TO  SEE  THE  UNSEEN 


Wimperis,  Henry  Egerton,  2,  3.  Z 

Winter,  George,  89. 

Witt,  Gustav,  47.  Zellner,  Benjamin,  224. 

Wood,  Stephen,  244.  Zisk,  Stanley  H.  "Stan",  56,  135,  143,  153,  169,  170, 

238. 


Yaplee,  Benjamin  S.,  25,  68. 

Yeomans,  Don,  256. 

Yevpatoriya  tracking  station,  118,  259.  See  also  Institute 

of  Radio  Engineering  and  Electronics. 
Young,  Tom,  155,  161. 


About  the  Author 


Andrew  J.  Butrica,  a  graduate  of  the  doctoral  program  in  the  history  of  science  and 
technology  at  Iowa  State  University,  is  a  research  historian  and  author  of  numerous  arti- 
cles and  papers  on  the  history  of  electricity  and  electrical  engineering  in  the  United  States 
and  France  and  the  history  of  science  and  technology  in  nineteenth-century  France.  He 
is  the  author  of  a  corporate  history,  Out  of  Thin  Air:  A  History  of  Air  Products  and  Chemicals, 
Inc.,  1940-1990,  published  by  Praeger  in  1990,  and  a  co-editor  of  The  Papers  of  Thomas 
Edison:  Vol.  I:  The  Making  of  an  Inventor,  1847-1873,  published  by  Johns  Hopkins  University 
Press  in  1989. 

Prior  to  writing  this  history  of  planetary  radar  astronomy,  Dr.  Butrica  was  a  research 
fellow  with  the  Center  for  Research  in  the  History  of  Science  and  Technology,  Cite  des 
Sciences  et  de  1'Industrie  (La  Villette) ,  Paris,  thanks  to  a  grant  from  the  International 
Division  of  the  National  Science  Foundation  (1991-1992)  and  an  earlier  fellowship  from 
the  Centre  National  de  la  Recherche  Scientifique  (1987-1988).  Butrica  also  has  under- 
taken public  history  work,  including  the  researching,  conducting,  and  editing  of  oral  his- 
tory interviews  for  chemical  company  and  hospital  histories. 

Dr.  Butrica  has  been  an  invited  lecturer  at  the  Ecole  des  Hautes  Etudes  en  Sciences 
Sociales  (Paris),  the  University  of  Paris  (Sorbonne),  and  Nottingham  (England) 
University,  as  well  as  at  Rutgers  University,  and  has  been  a  visiting  scholar  at  the  Deutsches 
Museum  (Munich),  the  University  of  Pennsylvania,  and  Lehigh  University.  He  is  a  mem- 
ber of  several  professional  bodies,  including  the  American  Historical  Association,  the 
History  of  Science  Society,  the  Society  for  the  History  of  Technology  (Robinson  Prize 
Committee),  the  Society  for  French  Historical  Studies,  the  Institute  of  Electrical  and 
Electronic  Engineers,  and  the  Association  pour  1'Histoire  de  1'Electricite  en  France. 


297 


The  NASA  History  Series 


Reference  Works,  NASA  SP-4000: 

Grimwood,  James  M.  Project  Mercury:  A  Chronology. 
(NASA  SP-400 1,1963). 

Grimwood,  James  M.,  and  Hacker,  Barton  C.,  with 
Vorzimmer,  Peter  J.  Project  Gemini  Technology  and 
Operations:  A  Chronology.  (NASA  SP-4002,  1969). 

Link,  Mae  Mills.  Space  Medicine  in  Project  Mercury. 
(NASA  SP-4003,  1965). 

Astronautics  and  Aeronautics,  1963:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4004,  1964). 

Astronautics  and  Aeronautics,  1964:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4005,  1965). 

Astronautics  and  Aeronautics,  1965:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4006,  1966). 

Astronautics  and  Aeronautics,  1966:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4007,  1967) . 

Astronautics  and  Aeronautics,  1967:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4008,  1968). 

Ertel,  Ivan  D.,  and  Morse,  Mary  Louise.  The  Apollo 
Spacecraft:  A  Chronology,  Volume  I,  Through  November  7, 
1962.  (NASA  SP-4009,  1969). 

Morse,  Mary  Louise,  and  Bays,  Jean  Kernahan.  The 
Apollo  Spacecraft:  A  Chronology,  Volume  II,  November  8, 
1962-September  30,  1964.  (NASA  SP-4009,  1973). 

Brooks,  Courtney  G.,  and  Ertel,  Ivan  D.  The  Apollo 
Spacecraft:  A  Chronology,  Volume  III,  October  1, 
1964-January  20,  1966.  (NASA  SP-4009,  1973). 

Ertel,  Ivan  D.,  and  Newkirk,  Roland  W.,  with  Brooks, 
Courtney  G.  The  Apollo  Spacecraft:  A  Chronology, 
Volume  IV,  January  21,  1966-july  13,  1974.  (NASA  SP- 
4009,  1978). 

Astronautics  and  Aeronautics,  1968:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4010,  1969). 

Newkirk,  Roland  W.,  and  Ertel,  Ivan  D.,  with  Brooks, 
Courtney  G.  Skylab:  A  Chronology.  (NASA  SP-4011, 
1977). 

Van  Nimmen,  Jane,  and  Bruno,  Leonard  C.,  with 
Rosholt,  Robert  L.  NASA  Historical  Data  Book,  Vol.  I: 
NASA  Resources,  1958-1968.  (NASA  SP-4012,  1976, 
rep.  ed.  1988). 


Ezell,  Unda  Neuman.  NASA  Historical  Data  Book,  VolII: 
Programs  and  Projects,  1958-1968.  (NASA  SP-4012, 
1988). 

Ezell,  Linda  Neuman.  NASA  Historical  Data  Book,  VoL 
III:  Programs  and  Projects,  1969-1978.  (NASA  SP- 
4012,  1988). 

Astronautics  and  Aeronautics,  1969:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4014,  1970). 

Astronautics  and  Aeronautics,  1970:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4015,  1972). 

Astronautics  and  Aeronautics,  1971:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4016,  1972). 

Astronautics  and  Aeronautics,  1972:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4017,  1974). 

Astronautics  and  Aeronautics,  1973:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4018,  1975). 

Astronautics  and  Aeronautics,  1974:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4019,  1977). 

Astronautics  and  Aeronautics,  1975:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4020,  1979). 

Astronautics  and  Aeronautics,  1976:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4021,  1984). 

Astronautics  and  Aeronautics,  1977:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4022,  1986). 

Astronautics  and  Aeronautics,  1978:  Chronology  of  Science, 
Technology,  and  Policy.  (NASA  SP-4023,  1986). 

Astronautics  and  Aeronautics,  1979-1984:  Chronology  of 
Science,  Technology,  and  Policy.  (NASA  SP-4024, 1988). 

Astronautics  and  Aeronautics,  1985:  Chronology  of 
Science,  Technology,  and  Policy.  (NASA  SP-4025, 
1990). 

Gawdiak,  Ihor  Y.  Compiler.  NASA  Historical  Data  Book, 
VoL  IV:  NASA  Resources,  1969-1978.  (NASA  SP-4012, 
1994). 

Noordung,  Hermann.  The  Problem  of  Space  travel:  The 
Rocket  Motor.  Ernst  Stuhlinger,  and  J.D.  Hunley,  with 
Jennifer  Garland.  Editors.  (NASA  SP-4026,  1995) . 


299 


300 


TO  SEE  THE  UNSEEN 


Management  Histories,  NASA  SP-4100: 

Rosholt,  Robert  L.  An  Administrative  History  of  NASA, 
1958-1963.  (NASA  SP-4101,  1966). 

Levine,  Arnold  S.  Managing  NASA  in  the  Apollo  Era. 
(NASA  SP-4102,  1982). 

Roland,  Alex.  Model  Research:  The  National  Advisory 
Committee  for  Aeronautics,  1915-1958.  (NASA  SP- 
4103,  1985). 

Fries,  Sylvia  D.  NASA  Engineers  and  the  Age  of  Apollo 
(NASA  SP-4104,  1992). 

Glennan,  T.  Keith.  The  Birth  of  NASA:  The  Diary  of  T. 
Keith  Glennan,  edited  by  J.D.  Hunley.  (NASA  SP- 
4105,  1993). 

Project  Histories,  NASA  SP-4200: 

Swenson,  Loyd  S.,  Jr.,  Grimwood,  James  M.,  and 
Alexander,  Charles  C.  This  New  Ocean:  A  History  of 
Project  Mercury.  (NASA  SP-4201,  1966). 

Green,  Constance  McL.,  and  Lomask,  Milton. 
Vanguard:  A  History.  (NASA  SP-4202,  1970;  rep.  ed. 
Smithsonian  Institution  Press,  1971). 

Hacker,  Barton  C.,  and  Grimwood,  James  M.  On 
Shoulders  of  Titans:  A  History  of  Project  Gemini.  (NASA 
SP-4203,  1977). 

Benson,  Charles  D.  and  Faherty,  William  Barnaby. 
Moonport:  A  History  of  Apollo  Launch  Facilities  and 
Operations.  (NASA  SP-4204,  1978). 

Brooks,  Courtney  G.,  Grimwood,  James  M.,  and 
Swenson,  Loyd  S.,  Jr.  Chariots  for  Apollo:  A  History  of 
Manned  Lunar  Spacecraft.  (NASA  SP-4205,  1979) . 

Bilstein,  Roger  E.  Stages  to  Saturn:  A  Technological 
History  of  the  Apollo/Saturn  Launch  Vehicles.  (NASA 
SP-4206,  1980). 

Compton,  W.  David,  and  Benson,  Charles  D.  Living 
and  Working  in  Space:  A  History  ofSkylab.  (NASA  SP- 
4208,  1983). 

Ezell,  Edward  Clinton,  and  Ezell,  Linda  Neuman.  The 
Partnership:  A  History  of  the  Apollo-Soyuz  Test  Project. 
(NASA  SP-4209,  1978). 

Hall,  R.  Cargill.  Lunar  Impact:  A  History  of  Project 
Ranger.  (NASA  SP-4210,  1977). 

Newell,  Homer  E.  Beyond  the  Atmosphere:  Early  Years  of 
Space  Science.  (NASA  SP-4211,  1980). 


Ezell,  Edward  Clinton,  and  Ezell,  Linda  Neuman.  On 
Mars:  Exploration  of  the  Red  Planet,  1958-1978. 
(NASA  SP-4212,  1984). 

Pitts,  John  A.  The  Human  Factor:  Biomedicine  in  the 
Manned  Space  Program  to  1980.  (NASA  SP-4213, 
1985). 

Compton,  W.  David.  Where  No  Man  Has  Gone  Before:  A 
History  of  Apollo  Lunar  Exploration  Missions.  (NASA 
SP-4214,  1989). 

Naugle,  John  E.  First  Among  Equals:  The  Selection  of 
NASA  Space  Science  Experiments  (NASA  SP-4215, 
1991). 

Wallace,  Lane  E.  Airborne  Trailblazer:  Two  Decades  with 
NASA  Langley 's  Boeing  737  Flying  Laboratory.  (NASA 
SP-4216,  1994). 

Center  Histories,  NASA  SP-4300: 

Rosenthal,  Alfred.  Venture  into  Space:  Early  Years  of 
Goddard  Space  Flight  Center.  (NASA  SP-4301 ,  1985) . 

Hartman,  Edwin,  P.  Adventures  in  Research:  A  History  of 
Ames  Research  Center,  1940-1965.  (NASA  SP-4302, 
1970). 

Hallion,  Richard  P.  On  the  Frontier.  Flight  Research  at 
Dryden,  1946-1981.  (NASA  SP-4303,  1984). 

Muenger,  Elizabeth  A.  Searching  the  Horizon:  A  History 
of  Ames  Research  Center,  1940-1976.  (NASA  SP-4304, 
1985). 

Hansen,  James  R.  Engineer  in  Charge:  A  History  of  the 
Langley  Aeronautical  Laboratory,  1917-1958.  (NASA 
SP-4305,  1987). 

Dawson,  Virginia  P.  Engines  and  Innovation:  Lewis 
Laboratory  and  American  Propulsion  Technology.  (NASA 
SP-4306,  1991). 

Dethloff,  Henry  C.  "Suddenly  Tomorrow  Came  .  .  .":  A 
History  of  the Johnson  Space  Center,  1957-1990.  (NASA 
SP-4307,  1993). 

Hansen,  James  R.  Space/light  Revolution:  NASA  Langley 
Research  Center  from  Sputnik  to  Apollo  (NASA  SP-4308, 
1995). 

General  Histories.  NASA  SP-4400: 

Corliss,  William  R.  NASA  Sounding  Rockets,  1958-1968: 
A  Historical  Summary.  (NASA  SP-4401 ,  1971 ). 

Wells,  Helen  T.,  Whiteley,  Susan  H.,  and  Karegeannes, 
Carrie.  Origins  of  NASA  Names.  (NASA  SP-4402, 1976). 


PLANETARY  RADAR  ASTRONOMY  PUBLICATIONS 


301 


Anderson,  Frank  W.,  Jr.,  Orders  of  Magnitude:  A  History 
of  NACA  and  NASA,  1915-1980.  (NASA  SP-4403, 
1981). 

Sloop,  John  L.  Liquid  Hydrogen  as  a  Propulsion  Fuel, 
1945-1959.  (NASA  SP-4404,  1978). 

Roland,  Alex.  A  Spacefaring  People:  Perspectives  on  Early 
SpacejUght.  (NASA  SP-4405,  1985). 

Bilstein,  Roger  E.  Orders  of  Magnitude:  A  History  of  the 
NACA  and  NASA,  1915-1990.  (NASA  SP-4406, 
1989). 

Logsdon,  John  M.  Logsdon,  with  Lear,  Linda  J., 
Warren-Findley,  Jannelle,  Williamson,  Ray  A.,  and 
Day,  Dwayne  A.  Exploring  the  Unknown:  Selected 
Documents  in  the  History  of  the  U.S.  Civil  Space  Program, 
Volume  I:  Organizing  for  Exploration.  (NASA  SP-4407, 
1995). 


"New  Series  in  NASA  History,"  published  by 
The  Johns  Hopkins  University  rress: 

Cooper,  Henry  S.F.,  Jr.  Before  Lift-Off :  The  Making  of  a 
Space  Shuttle  Crew.  (1987). 

McCurdy,  Howard  E.  The  Space  Station  Decision: 
Incremental  Politics  and  Technological  Choice.  ( 1990) . 

Hufbauer,  Karl.  Exploring  the  Sun:  Solar  Science  Since 
Galileo.  (1991). 

McCurdy,  Howard  E.  Inside  NASA:  High  Technology  and 
Organizational  Change  in  the  U.S.  Space  Program. 
(1993). 

Lam brigh  t,  W.  Henry.  Powering  Apollo:  James  E.  Webb  of 
NASA.  (1995). 


ISBN  0-16-048578-9 


90000 


9  780160  485787 


New  in  the  NASA 
History  Series 


Exploring  the  Unknown:  Selected  Documents  in  the  History 

of  the  U.S.  Civil  Space  Program,  Volume  I:  Organizing  for 

Exploration 

Edited   by  John   M.   Logsdon,   with   Linda  J.   Lear, 

Jannelle   Warren-Findley,   Ray  A.   Williamson,   and 

Dwayne  A.  Day,  NASA  SP-4407,  1995 

The  first  of  a  projected  three  volume  selection  of  key 
documents  in  the  history  of  the  U.S.  civil  space  pro- 
gram, this  volume  prints  more  than  200  key  documents 
relative  to  the  theme  of  organizing  for  exploration, 
each  with  a  headnote  providing  background  and  bibli- 
ographical information.  These  are  organized  into  four 
sections  introduced  by  an  essay  that  gives  context  for 
the  larger  history  of  the  space  program.  This  is  a  major 
new  resource  for  those  who  seek  to  understand  the 
development  of  the  entry  of  the  United  States  into 
space  exploration. 

Space/light  Revolution:  NASA  Langley  Research  Center  from 

Sputnik  to  Apollo 

James  R.  Hansen,  NASA  SP-4308,  1995 

Focusing  on  Langley  Research  Center  in  Hampton, 
Virginia,  during  the  late  1950s  and  1960s,  this  book 
assesses  the  rapid  transformation  of  a  government 
research  laboratory  during  a  pivotal  era.  Langley, 
established  as  the  original  laboratory  of  the  National 
Advisory  Committee  for  Aeronautics  in  1917,  had  long 
been  involved  in  cutting-edge  aeronautical  research 
and  development.  The  flight  of  Sputnik  I  in  1957,  how- 
ever, prompted  important  changes  in  the  center's  focus 
and  method  of  operation.  It  became  part  of  NASA  in 
1958,  and  its  leaders  shifted  the  workload  from  almost 
exclusively  center-unique  aeronautical  research  to 
efforts  that  involved  other  research  facilities  and  dealt 
much  more  fully  with  the  challenges  of  spaceflight. 

The  Problem  of  Space  Travel:  The  Rocket  Motor 

Edited   by   Ernst   Stuhlinger   and  J.D.   Hunley  with 

Jennifer  Garland,  NASA  SP-4026,  1995 

This  is  the  first  fully  edited,  complete  English  transla- 
tion of  Hermann  Noordung's  1929  classic  book,  Das 
Problem  der  Befahrung  des  Weltraums,  treating  the  engi- 
neering details  of  an  orbital  space  station.  "For  those 
who  do  not  read  German  (or  who  do  not  have  access  to 
the  original),  and  who  are  interested  in  the  early  histo- 
ry of  space  travel  concepts,  this  is  an  invaluable  addi- 
tion to  one's  reference  library.  It's  been  a  long  time 
coming,  but  well  worth  the  wait." — Quest:  The  Magazine 
of  Spaceflight  History,  Spring  1995. 


The  NASA  History  Series 

National  Aeronautics  and  Space  Administration 

NASA  History  Office 

Washington,  D.C. 

1996