Hug 1967 SYSTEM CONCEPT FOR WIDE-FIELD-OF-VIEW OBSERVATIONS OF OCEAN PHENOMENA FROM SPACE AUGUST 1987 on € Nonwsis™ 50, EOSAT C. WILLIAMS COMMERCIAL/OPERA- TIONAL USERS PANEL J. HAUSTEIN - MOBIL RESEARCH AND DEVELOPMENT CORP C. BECK — NAVAL POLAR OCEANOGRAPHY CENTER P. CHAVASANT — NAVAL ENVIRON. PREDICT. FACILITY R, FAY — OCEAN IMAGING CO L. FISHER — NATIONAL MARINE FISHERIES SERVICE A. HAWORTH — WFOA J. HILL — LOUISIANA STATE UNIVERSITY T. LEMING — NATIONAL MARINE FISHERIES SERVICE J. MALAY — NAVAL SPACE COMMAND J. MALONEY — OCEANROUTES, INC P. MITCHELL — U.S. NAVAL RESEARCH LABORATORY V. NOBLE — U.S. NAVAL RESEARCH LABORATORY H. PALMER — MARINE TECHNOLOGY SOCIETY —. PUTNAM — HUGHES/SBRC W. SIAPNO — CONSULTANT - OCEAN MINING J. SVEJKOVSKY — OCEAN IMAGING CO R. TIPPER — U.S. NAVY/NOAA JOINT ICE CENTER M. WILLARD — EOSAT S. TILFORD SeaWiFs WORKING GROUP Ft @ We neal Gp a." 0? Td em 0 ar oo eS Oo ou a mn oi Des SS mo J. BAKER - JOINT OCEANOGRAPHIC INSTITUTIONS, INC K. RUGGLES - SYSTEMS WEST, INC D. LaPORTE - HUGHES/SBRC RESEARCH USERS PANEL O. BROWN - UNIVERSITY OF MIAMI ABBOTT — SCRIPPS INST. OF OCEANOGRAPHY (UCSD) ARNONE — NORDA BROWN — SAIC COLGAN — NAVAL POLAR OCEANOGRAPHY CENTER CORNILLON — UNIVERSITY OF RHODE ISLAND DAVIS — JET PROPULSION LAB EDEN — JOI, INC EPPLEY — SCRIPPS INST. OF OCEANOGRAPHY (UCSD) GAUTIER — SCRIPPS INST. OF OCEANOGRAPHY (UCSD) HUGHES — NOAA/NESDIS LANDSAT TRANSITION GROUP KERMOND —NATL. ASSOC. OF STATE UNIV.ERSITIES AND LAND GRANT COLLEGES McCLAIN — NASA/GSFC MOLLO-CHRISTENSEN — NASA/GSFC NJOKU — NASA/CODE EEC PENHALE — NSF POLAR PROGRAMS PERRY — UNIVERSITY OF WASHINGTON REEVE — NSF OCEAN SCIENCES RESEARCH SACKETT — AMERICAN GEOPHYSICAL UNION SAMBROTTO — NSF OCEAN SCIENCE RESEARCH SMITH — UCSB STEELE — WOODS HOLE OCEANOGRAPHIC INST STETINA — NASA/GSFC TAYLOR — NSF OCEAN SCIENCES RESEARCH TIPPER — U.S. NAVY/NOAA JOINT ICE CENTER UHLIR — NAS SPACE SCIENCE BOARD WALSH — UNIVERSITY OF SOUTH FLORIDA WILSON — NASA HQ, OCEANIC PROCESSES BRANCH WROBLEWSK! — OFFICE OF NAVAL RESEARCH YENTSCH — BIGELOW LAB. FOR OCEAN SCIENCES YODER — NASA HQ, CODE EEC © mG) 2 2nAtr O @ ws 27 OAS = IMPLEMENTATION PANEL A. MIKA - HUGHES/SBRC BARNES — NASA/GSFC BISHOP — SAIC CARDER — UNIV. OF SOUTH FLORIDA CLARK — NOAA/NESDIS DURHAM — HUGHES/SBRC ESAIAS — NASA/GSFC EVANS — UNIVERSITY OF MIAMI FELDMAN — NASA/GSFC FISCHEL — EOSAT GOLDSHLAK — HUGHES/SBRC GORDON — UNIVERSITY OF MIAM | HUBBARD — EOSAT JUROTICH — NOAA/NESDIS LANDSAT TRANSITION GROUP KIRK — NASA/GSFC MARTCH — RCA MOWLE — EOSAT MUELLER — SCRIPPS INST. OF OCEANOGRAPHY (UCSD) RUGGLES — SYSTEMS WEST SCHULMAN — EOSAT STUMPF — NOAA/NESDIS VERMILLION — NASA/GSFC WOODY — HUGHES/SBRC NAN O400 TT 0 0301 oO MO | REACH G25 Wer SYSTEM CONCEPT FOR WIDE-FIELD-OF-VIEW OBSERVATIONS OF OCEAN PHENOMENA FROM SPACE REPORT OF THE JOINT EOSAT/NASA SeaWiFS WORKING GROUP AUGUST 1987 Chairmen: DR. JAMES BAKER Joint Oceanographic Institutions, Inc. DR. KENNETH W. RUGGLES Systems West, Inc. Executive Secretary: DANIEL D. LaPORTE Hughes Aircraft Company Santa Barbara Research Center Editor; EVELYN S. PUTNAM Hughes Aircraft Company Santa Barbara Research Center EARTH OBSERVATION SATELLITE COMPANY ¥¥t NATIONAL AERONAUTICS AND SPACE ADMINISTRATION Earth Science and Applications Division 4300 Forbes Boulevard Washington, D.C. 20546 Lanham, Maryland 20706 ee 7 Pea Fo. , ‘ f iy A A J rs We SIV LON Ob % { RDA \ | be I hd } Woods Hale Oceanographic / \ ; INSTITUTION % a — eS i SUMMARY Satellite-acquired ocean-color and sea-surface- temperature data are powerful tools for understanding biological and physical processes in the ocean on a global scale. From 1978 to 1986, the Coastal Zone Col- or Scanner (CZCS) aboard the Nimbus-7 satellite pro- vided the first ocean-color data. During this period re- searchers demonstrated that these data can be used to determine the abundance of ocean biota. As a result, many commercial, operational, and research applica- tions were developed that take advantage of the direct relationship of the ocean's color to its phytoplankton content. Also, data from the long-wavelength infrared bands of the Advanced Very-High Resolution Radiometer (AVHRR) aboard the NOAA series of satellites have proven useful in developing global maps of sea-surface temperature. Used jointly, these data have given new insights into the role of the oceans in our biosphere as well as providing economic benefits to several major in- dustries. This work demonstrates the need for an operational spaceborne sensor that would provide data on ocean color and sea-surface temperature simultaneously. Since the CZCS has become nonoperational, this need has become acute. Recognizing the importance of sat- isfying this need and the opportunity for incorporating such a sensor on the Landsat-6 spacecraft, NASA, Headquarters and EOSAT convened a SeaWiFS! Work- ing Group in early 1987 to: ®@ Discuss and document commercial, operational, and research applications for wide-field-of-view ocean- color imagery from the Landsat-6 satellite, @ Define users' requirements for sensor performance and for data products and dissemination, and to e@ Determine the feasibility of meeting the users’ re- quirements with respect to sensor design, accommo- dation of the sensor on the Landsat-6 satellite, data collection and distribution, and necessary space- craft and ground-station interfaces. | Sea-viewing, Wide-Field-of-View Sensor Ml The Working Group was organized into three panels, representing commercial and operational users of oceanographic data, research users, and those responsible for implementing the system. The Need for Ocean-Color Data The value-added industry needs ocean-color data to support all of the above applications in providing interpreted data products to its clients. The Research Panel documented a number of important research goals that could be reached only through continued availability of ocean-color data. These goals are to: The Commercial and Operational Users' Panel identified two principal user groups. The first comprises the 36,000 - 37,000 ocean-going ves- sels engaged worldwide in fishing and marine transportation and U.S. Navy vessels. The sec- ond, smaller user group comprises the value- added and offshore oil and gas exploration and development industries. Ships at sea need the ocean-color data to: © Specify quantitatively the ocean's role in the global carbon cycle and other major biogeo- chemical cycles, © Determine the magnitude and variability of an- nual primary production by marine phytoplank- ton on a global scale, ® Understand the fate of fluvial nutrients and their possible effect on carbon budgets, ® | ocate fish populations, thereby improving catch efficiency, and to © Elucidate the coupling mechanism between upwelling and large-scale patterns in ocean ® Optimize ship routes, thereby reducing costs. basins, @ Answer questions concerning the large-scale distribution and timing of spring blooms in the global ocean, Oil and gas exploration and development in- dustries need the data to: © Acquire a better understanding of the pro- ® Provide an accurate and detailed understana- ing of the oceanographic environment for off- shore platform design, reducing the risks atten- dant to underdesign, © Determine "weather windows" when offshore operations, such as shipping supplies, pipelay- ing, and platform installation, can be conduct- ed most safely and efficiently, and to ® Provide timely information on strong current jets and eddies, since these can cause a loss of drilling time due to increased loads on the arill- ing riser. cesses associated with mixing along the edge of eddies, coastal currents, western boundary currents, etc., and to ® Acquire global data on marine optical proper- ties. Supporting Research Requirements Several types of supporting research were de- fined by the users’ panels to fully implement the applications defined by the commercial and opera- tional users and to realize research goals. The following objectives of some ongoing projects from the Navy's Research Program represent the type of research required to support future commercial and operational applications: ® Develop general water-mass classification by coupling satellite-derived bio-optical data with sea-surface temperature data. ® Study the biota using ocean-color properties. © Develop thermodynamic ocean models, includ- ing the absorption of solar heat by the oceans. (The absorption in the near-surface layer and the dissipation of this heat are partially con- trolled by the diffuse attenuation coefficient, k, of the water, measurable from SeaWiFS data.) ® Examine ways of using data on integrated aero- sol distribution, which would be obtainable from SeaWiFS data. Three initiatives are proposed in the mission- support science plan for achieving oceano- graphic-research goals: © A sequence of cooperative international stud- les using high-resolution ocean-color observa- tions of an ocean basin to address stratified sampling issues | ®@ An expanded effort to improve bio-optical rela- tionships for the SeaWiFS band set and to de- velop and verify a physiologically based algo- rithm for productivity estimates ¢ A global collection of SeaWiFS observations and production of composite moderate- resolution maps of pigments and primary pro- ductivity. SUMMARY User Requirements and Performance Goals Although the users' panels readily agreed on most requirements and sensor performance goals, three issues were debated at some length: revisit interval, number and location of the spectral bands, and data-dissemination requirements. The revisit-interval issue centered on assess- ing the value of data acquired at scan angles larger than about 30° to the two user communities since, currently, atmospheric effects make quantit- ative interpretation of these data infeasible. The research users, whose interests lie in quantitative interpretation, were satisfied with the first SeaWiFS design that had a +45° scan angle, providing every-other-day global coverage at the equator. However, the commercial and operational users demonstrated the great value of qualitative inter- pretation of imagery at scan angles greater than 45° for their uses and the need for daily revisits to the same scene location. Since the effect on sen- sor design was slight, it was agreed that the base- line design would have a +58° scan angle in order to provide a daily revisit interval. The baseline SeaWiFS spectral bands and radiometric performance requirements given in Table A-1 represent a consensus that balances the needs of both commercial and operational and research data users. Other important operating characteristics of the sensor are also presented in the table. With respect to the data dissemination issue, most commercial and operational users need to re- ceive data once a day within 24 hours or less of the time of acquisition, and major user groups re- quire daily, real-time reception. For example, the commercial fishing fleet needs to receive the data in near real time with relatively inexpensive equip- ment that is small in size, implying reception by a nondirectional antenna. Potential naval use would require daily, real-time reception in a format com- patible with their systems (e.g., the Tactical Envi- ronmental Support System (TESS) and/or the AN/ SMQ-11 receiver-recorder sets). A number of ap- plications envisioned by the value-added industry Vv vi Table A-1. SeaWiFS Baseline Spectral Regions and Performance Goals Minimum Minimum Bandwidth Signal-to-Noise Noise-Equivalent Ratio | Temperature Difference 433 - 453 nm 510 490 - 510 nm 500 555 - 575 nm 350 655 - 675 nm 285 745 - 785 nme 280 843 - 887 nm 280 10.5 - 11.5 um 0.29K (300K) 11.5-12.5 um 0.29K (300K) OANMDNAKRWNMY— Spatial Resolution: 1.13 km, inherent sensor resolution [Local area coverage (LAC)] 4.5 km, synthesized on board [Global area coverage (GAC)] Polarization Sensitivity: < 2% (worst case) Dynamic Range: 10 bits quantization (gain adjustable on board) Bright Target Recovery: 10 samples or less Scan Plane Tilt: t+ 20° Orbit: 705 km, circular, polar, sun-synchronous Equatorial Crossing Time: 10:30 a.m. (acceptable between 10:30 a.m. and 1:30 p.m.) THR. Gordon 1987: personal communication. The signal-to-noise values jmust be met at all sun angles. Blocked from 760 to 770 nm. will also require daily access to the stored data that is downlinked to the EOSAT ground- processing facility within 24 hours of their acquisi- tion. Researchers will use the data downlinked to the EOSAT ground-processing facility after it is transferred to the NASA/GSFC facility. Occasion- ally, quick-look data products for selected areas will be required within 12 hours of collection for positioning research vessels. However, for the most part, research needs will be satisfied if the raw data are available within 7 days of acquisition and other data products are available within 8 to 10 days of collection. Implementation of Requirements The purpose of the Implementation Panel was to translate the mission objectives of the commer- cial, operational, and research users into a work- able system concept that would provide the data required to meet the users’ needs. The work of TILT MECHANISM VNIR AFT ASSEMBLY DICHROIC BEAMSPLITTERS TIR AFT ASSEMBLY \ RADIATIVE COOLER SUMMARY this panel supported the other panels by defining the technical tradeoffs among the performance parameters and by identifying the practical conse- quences of various options in terms of cost and complexity. Thus, the Implementation Panel esta- blished a feasibility envelope for the Working Group, leading to a system concept that was not only useful from the users' perspective, but also technically and economically realizable. Sensor Design Concept The baseline SeaWiFS design, meeting all de- sired sensor requirements, is shown in Figure A-1. The sensor concept is based on low-cost, low- risk technology and results in a lightweight and compact instrument. In the proposed design, the telescope rotates 360° about a pivot axis to scan the scene, thereby avoiding the use of a scan mir- ror and its associated polarization effects. Specu- lar sun reflection is avoided by tilting the telescope in the plane perpendicular to the scan plane (i.e., along track) to one of three positions: +20°, 0°, Figure A-1. Baseline Sea- WiFS design. HALF-ANGLE MIRROR SOLAR DIFFUSER TRACK (TILT) or -20°. The continuous 360° scan allows refer- ence sources to be viewed during the non-scene- viewing part of the scan, as well as allowing a deep space view for a zero reference just before the scan begins. There is also a solar diffuser that can be inserted into the field of view of the sensor for calibration against the input solar radiance. Expected Sensor Performance Estimates of three key performance parame- ters were made: radiometric performance, modu- lation transfer function (MTF), and polarization sensitivity. The expected radiometric perfor- mance, shown in Table A-2, meets the perfor- mance goals established by the user groups. The MTF was calculated at the Nyquist angu- lar frequency of 0.313 cy/mrad. The results indi- cate that the VNIR MTF will be 0.36 in the scan di- rection and 0.57 in the track direction; TIR MTF will be 0.34 and 0.53 in the scan and track direc- tions, respectively. These values correlate well with the nominal rule for sensor design that the MTF should equal or exceed 0.3 at the Nyquist frequency; again, there is performance margin rel- ative to the user requirements. For the SeaWiFS, the polarization sensitivity depends on the scan angle, since the major con- tributor is the half-angle mirror. Figure A-2 shows the estimated polarization sensitivity of the Sea- WIFS as a function of scan angle at a wavelength of 443 nm and that it always remains within the 2% desired limit. Moreover, the 443 nm data repre- sent the worst case; polarization effects are small- er in all other bands. Table A-2. SeaWiFS Estimated Radiometric Performance Saturation Radiance! (nW/cm2-sr-um) Signal 1 2 3 4 5 6 if 8 1 2 At 300K. Vili Radiance! (nW/cm2 -sr-um) Noise-Equivalent Temperature Difference 2 (K) Signal-to-Noise Ratio H. R. Gordon 1987: personal communication. a es 86S UNM AR Y 3 = = Pa = D Zz LU 7) Zz fe) oe < N o < ot) O oO -1.4% Ae = 443 NM Figure A-2. SeaWiFS esti- mated polariza- tion sensitivity. > —————— TOTAL SCAN ——_______ -20 0 OBJECT-SPACE SCAN ANGLE, DEG Spacecraft and Ground Segment The current spacecraft configuration into which the SeaWiFS sensor would be integrated, differs from the original Landsat-6 spacecraft con- figuration due to programmatic changes and changes in the launch vehicle. The spacecraft concept is derived from a DMSP/TIROS-type sys- tem, but it has been extended to meet the EOSAT mission's needs. The projected SeaWiFS subsys- tem weight of 153 pounds is well within the 360 pounds available for growth in the proposed spacecraft. Hence, the spacecraft can support the SeaWiFS mission and may also be able to sat- isfy an EOSAT goal of adding a third, spare wide- band recorder for the Enhanced Thematic Map- per (ETM) data. One of the key spacecraft limitations encoun- tered in accommodating both the SeaWiFS mission and ETM mission on Landsat-6 lies in the power subsystem. These power constraints, which will affect mission operations (particularly with respect to nighttime operations) are currently being exam- ined in a System Integration Study, sponsored by EOSAT. Some compromises in the ETM and Sea- WiFS tasking profiles may be necessary to accom- modate the SeaWiFS. However, if the required compromises are unacceptable, expansion of spacecraft power resources will be addressed. SeaWiFS data will be acquired for, nominally, 40 minutes per orbit. Current plans and power budgets call for daylight-only imaging, but nighttime imagery might be acquired occasionally for experi- mental purposes. During imaging, SeaWiFS data will be transmitted in real time and recorded on on-board tape recorders. By combining the spacecraft-support resources for the SeaWiFS and ETM sensors and extending the capacity of the command/telemetry tape recorders, the eight orbits of data storage required for data collection outside the reception range of the EOSAT ground station can be acquired, and all stored data can be downlinked to a single facility. ix On-Board Data Processing The sensor's data stream will be formatted and the spacecraft's time code and ephemeris data in- corporated into the format prior to recording or transmitting data. The attitude of the spacecraft (pitch, roll and yaw) will be reported with a within- limits flag. Data Downlinks Three downlinks are currently planned for SeaWiFS data. One would be a stored-data downlink that would provide the global area cov- erage and local area coverage data to the EOSAT ground receiving facility. These data would be downlinked directly on the X-band. Another downlink would convey real-time, high-resolution LAC data at a frequency compati- ble with currently operating high-resolution picture transmission (HRPT) receiving stations and planned naval AN/SMQ-11 stations (L-band or S- band). The baseline direct-downlink data format is similar to the TIROS-N HRPT frame format. It pro- vides the proper synchronization blocks for the hardware while still transmitting all of the required data at an effective data rate of 665 kbps. The third downlink would convey real-time, low-resolution GAC data to subscribers on a UHF frequency. These data would be transmitted at 56 kbps, allowing some subscribers (e.g., moder- ately sized ships at sea that cannot mount large, tracking, dish antennas) to use relatively inexpen- sive, commercially available receivers and fixed receiving antennas. The data for real-time transmission will be pro- vided on a subscription basis. They will be en- crypted by the SeaWiFS Data Formatter to protect their commercial value; decoding keys will be fur- nished to subscribers in a manner similar to those furnished to subscribers of television services. No tape-recorded data will be available on either real-time downlink. The Implementation Panel recognized that re- xX ception of high-resolution LAC data is also desired by users restricted to unsophisticated receiving stations. However, transmitting high-resolution data to a fixed antenna would require much great- er power in the spacecraft transmitter than is available on the currently envisioned Landsat spacecraft. Adding the required power would not only be costly, but also might exceed the weight limitations of the spacecraft. One potential solu- tion to this problem would be to process the 1.13-km recorded data immediately upon receipt by the ground-receiving site, redistributing the data products via radio facsimile or telecommuni- cations links. The desire of some users to have near-real- time access to a global data set presents a great- er problem, since the current data-handling plans for the tape-recorded global data set do not allow real-time access. However, a study is being un- dertaken to determine the feasibility and cost of rerouting the X-band, downlinked global data set via communication links to the processing facilities of commercial and operational users. Data Products For Research Users The following data products will be produced at NASA/GSFC within 8 to 10 days of data acquisi- tion: © The Level-1 data product will contain the total radiances for visible and near-infrared bands and brightness temperatures for thermal bands. The Level-2 product is a product derived from Level-1 data containing chlorophyll-a, other pigments, water-leaving radiances, and sea- surface temperature. Level 3 is a daily mosaic product for nine Level- 2 products on an 18-km grid with statistics in- cluding the number of pixels, number of days, and sums of squares for each grid element. Weekly composites will be made of the geo- physical data. cs SUNN AF Y Browse images will be available, consisting of international research users through its archival images of all data products recorded on video and distribution system. EOSAT will acquire disks. copies of the data products for its archive to NASA/GFSC will provide data products to its serve all commercial and operational users. principal investigators, Announcement-of- Figure A-3 summarizes the baseline SeaWiFS Opportunity Investigators, and other national and data acquisition and dissemination plans. Figure A-3. Baseline SeaWiFS data acquisition and dissemination plans. RAW LAC DATA, HRPT-COMPATIBLE < | TRACKING ANTENNA SUBSCRIBERS REAL TIME SEAWIFS PAYLOAD DATA ACQUISITION DATA RECORDING L- OR S-BAND RAW GAC DATA, 56 KBPS OMNI ANTENNA SUBSCRIBERS REAL TIME EOSAT NASA/GSFC GROUND- COMPUTER- GROUND- RECEIVING COMPATIBLE PROCESSING FACILITY TAPES FACILITY DATA PRODUCTS DATA LEVELS-O, 1 2no EAC: GAC DATA PRODUCTS RAW LAC, GAC DATA, HRPT-COMPATIBLE PRODUCTS FORMAT SUBSCRIBERS RESEARCH USERS EXPEDITED 7- TO 10-DAY DATA ACCESS ACCESS Xl Xi FOREWORD Global and mesoscale oceanographic applications and coastal-zone studies require ocean-color imagery and sea-surface temperature measurements from satellite-borne instruments. Measuring and mapping chlorophyll concentrations, sediments, and temperature are of particular interest. These data provide a meas- ure of the spatial and temporal variability of phytoplank- ton biomass, sediment concentration, and ocean cur- rents. In addition to this research that promises to pro- vide an enhanced understanding of basic physical and biological processes in the biosphere, these data also constitute the basis for many commercial and opera- tional applications of significant importance to several industries and to the U.S. Navy. The first satellite-borne ocean-color sensor was the Coastal Zone Color Scanner (CZCS), which was aunched aboard the Nimbus-7 satellite in October 1978 and operated successfully until the summer of 1986. The purpose of this instrument was to establish the feasibility of determining chlorophyll concentrations from space by measuring ocean color. A mathematical relationship between the CZCS estimates of algal pig- ments and in-situ plankton chlorophyll measurements was first established in 1980, and validation experi- ments are continuing to extend the accuracy and utility of this relationship. CZCS data were also found to be useful in defining ocean fronts, current patterns, and coastal sediment transport. The knowledge of these phenomena, in conjunction with sea-surface tempera- ture measurements, was clearly shown to have eco- nomic significance for fisheries through the NASA Fish- eries Demonstration Program. These successes led to formation of a Science Working Group, chartered by NASA, with members rep- resenting the academic oceanographic community, Goddard Space Flight Center (GSFC), and other agen- cies. The group recommended that NASA build and fly an advanced Ocean Color Imager (OCI) to meet re- quirements for ocean chlorophyll data. The group's re- xiii XIV port, "Marine Resources Experiment Program," outlining the justification and necessary perfor- mance specifications was published in December 1982. In 1986 NOAA suggested that a government- industry partnership be formed to provide ocean- color data. In response, EOSAT initiated efforts to survey the market and to define user require- ments and studies on sensor design and space- craft accommodation of the sensor. In addition, NASA initiated "Phase A" studies to define ground-segment and data-processing require- ments. Recognizing the mutual benefits accruing from the joint collaboration of NASA and EOSAT, demonstrated by the Thermal Infrared Working Group (Putnam 1986), the Sea-viewing Wide-Field Sensor (SeaWiFS) Working Group was organized. The overall purpose of the EOSAT/NASA SeaWiFS Working Group was to define the specifications for a feasible and cost-effective SeaWiFS system, including spacecraft and ground segments. The SeaWiFS Working Group convened in a 2-day session at EOSAT headquarters in Lanham, Maryland, February 11 and 12, 1987. The work- shop was attended by about 70 persons from government, academia, and industry. The charter of the Working Group was to: © Demonstrate the technical capability of achieving the OCI/MAREX mission objectives through flying a wide-field-of-view sensor in addition to the Thematic Mapper on board the Landsat-6 spacecraft, and ® Define on-board and ground data-processing systems with the capability of acquiring, pro- cessing, distributing, and archiving SeaWiFS data within the time and data-format con- straints of the commercial, operational, and re- search user communities. The Working Group was organized into three panels, representing the interests of commercial and operational users of oceanographic data, oceanographic research, and those responsible for implementing the system. The panels met si- multaneously and convened each day in a plen- ary session to exchange information on progress made and emerging recommendations. The Re- search Panel focused on defining the scientific purposes that could be served by remotely sensed ocean-color imagery and temperature measurements and the system parameters that would be required to acquire these data. The Commercial and Operational Users' Panel sum- marized the public- and private-sector applica- tions for these data and the data processing and dissemination system that would be required for commercial and operational use. The Implemen- tation Panel explored sensor-concept definition, spacecraft integration, data handling, downlinks and formats, and data processing and distribution scenarios that were feasible for implementation to satisfy the requirements of the potential users of the data. The recommendations of the panels were integrated and summarized during a sec- ond meeting of the Working Group on 8 April 1987. This report contains the findings of the two meetings. The SeaWiFS Working Group effort builds on the success of the prior Thermal-Infrared Work- ing Group and represents an ongoing process of joint government and industry program evalua- tion to ensure development of significant new remote-sensing initiatives with commercial and scientific research applications. APPENDIX A APPENDIX B CONTENTS HISTORICAL PERSPECTIVE COMMERCIAL AND OPERATIONAL USERS' PANEL REPORT RESEARCH USERS' PANEL REPORT SYNTHESIS OF REQUIREMENTS IMPLEMENTATION PANEL REPORT BIBLIOGRAPHY DISCIPLINE - SPECIFIC VOCABULARY AND ACRONYMS PARTICIPANTS 21 33 47 63 81 85 XV Xvi HISTORICAL PERSPECTIVE The Coastal Zone Color Scanner (CZCS) was the first instrument to acquire ocean-color data from space. It was one of eight experiments on NASA's Nimbus-7 satellite, which was launched in 1978.' The CZCS was designed only to verify "proof of concept," and the instrument had a de- sign lifetime of about 1 year. However, the CZCS provided high-quality imagery from October 1978 until the summer of 1986 when the instrument stopped sending data. Table 1 summarizes the characteristics of the CZCS system. Since the CZCS is the only instrument of its kind, its loss is of major consequence to those interested in research, commercial, and operational applications for ocean-color data. Table 1. Major Parameters and Characteristics of the CZCS Band Center Width Phenomenon Chlorophyll Reference Gelbstoffe, sediments Chlorophyll Surface vegetation Surface temperature Orbital Altitude: 955 km Inclination: 99.2° Period: Ascending Node: IFOV: Footprint: Scan Angle: Swath Width: Scan Plane Tilt: Digitization: Repeat Coverage: Revisit Interval: Data Rate: 104.15 min. 11:52 a.m. (Local mean solar time) VNIR, 0.865 x 0.865 mrad TIR, 0.927 x 0.88 mrad VNIR, 0.826 x 0.826 km TIR, 0.885 x 0.840 km + 39.4° 1600 km + 20° along track 8 bits 6 days 2 days 800 kbps average 3.5 Mbps, maximum 'The Nimbus Program consisted of seven different research satellites that surveyed the atmosphere of the Earth, mapped land and water charac- teristics, and observed weather and climate patterns. Advanced opera- tional satellites now in use for weather and land observations include in- struments and systems based on Nimbus designs. During its orbit the AVHRR instrument observes a given point on the surface of the Earth twice during each 24-hour period, once in daylight and once in darkness. 4 The incentive to acquire ocean-color imag- ery from a Satellite platform developed in the 1960s when aircraft and shipboard studies dem- onstrated it would be possible to use satellite- acquired data to measure the spectra of sunlight reflected from ocean waters. The radiance re- flected from the ocean in the visible wavelength region (400-700 nm) is related to the concentra- tion of chlorophyll and other plant pigments present, since chlorophyll is a green pigment and the color of the water changes from blue to green as the concentration of chlorophyll in- creases. lf the concentration of chlorophyll is known, the amount of phytoplankton in ocean waters can be calculated. Thus, satellite- acquired ocean-color data constitute a powerful tool for determining the abundance of ocean bio- ta on a global scale. As discussed in the follow- ing sections, many applications have been devel- oped that take advantage of this simple concept relating the color of the ocean to the amount of phytoplankton it contains. The CZCS measured the radiance reflected from the sea's surface in the visible and near- infrared (VNIR) region and in the thermal-infrared (TIR) region. The information from the visible wavelengths was used to calculate chlorophyll concentration, whereas sea-surface tempera- ture was calculated from the information ac- quired from the TIR band. Data from the near- infrared band (750 nm) was used to correct the data acquired in the visible bands for the effects of the atmosphere. The amount of radiance reflected from the ocean is very small compared to the atmospheric radiance arriving at the sensor due to Raleigh scattering. Since the atmospheric radiance con- stitutes as much as 90% of the apparent ocean- color signal, it is necessary to correct radiance measured by the satellite for the effects of the atmosphere. Successful development of accu- rate atmospheric-correction algorithms was a crucial step in making CZCS data useful in quan- titative oceanographic studies, and one of the im- portant conclusions drawn from the CZCS experi- ence was that the utility of atmospheric-correction algorithms is a key consideration in the design of any ocean-color sensor. From a scientific perspective, acquisition of ocean-color data from space in the early 1990s is a high-priority goal that has been recognized in reports of the National Research Council of the National Academy of Sciences. For example, satellite-acquired ocean-color measurements are key to the success of the Global Ocean Flux Study (GOFS), a major component of the National Science Foundation's Geosciences Initiative. In addition to the U.S. scientific community, scientists from Europe, Japan, and from many other coun- tries are also interested in participating in GOFS, and an international Joint GOFS program for the 1990s will soon be formalized under the auspices of the International Council of Scientific Unions. The scientific uses of ocean-color data will be en- hanced if the next mission is concurrent with NASA and European Space Agency (ESA) altime- ter (TOPEX, ERS-1) and scatterometer (NSCAT, ERS-1) missions, scheduled for the early 1990s.° These satellite-borne instruments will measure glo- bal ocean winds and currents, and this information will help explain global patterns in the distribution of phytoplankton determined from satellite- acquired ocean-color measurements. Commercial and operational users of ocean- color data also are intensely interested in a follow- on mission to the CZCS. During the period when CZCS data was available, a focused effort was mounted by NASA (JPL) and NOAA to develop ? TOPEX is the Topography Experiment satellite, ERS-1 is the ESA's first Earth Remote Sensing satellite, which will carry an Active Microwave Instrument (AMI) and an Along-Track Scanning Radiometer (ATSR), and NSCAT is the scatterome- ter scheduled to fly on the Naval Research Oceanographic Satellite System (NROSS) applications of commercial and operational use. For example, an experimental demonstration pro- gram, the Fisheries Demonstration Program, was conducted on the U.S. West Coast to assess the utility of environmental charts tailored for com- mercial fishing operations. This program, initiated in 1981, continued until cessation of CZCS data and showed the value of ocean-color data in in- creasing catch efficiency. Based on the success of this program, the value-added industry is still using sea-surface temperature data from the HISTORICAL PERSPECTIVE Advanced Very-High Resolution Radiometer (AVHRR) to support U.S. and Japanese fishing fleets. As discussed in some detail in the follow- ing sections, these data are of importance to sev- eral other user groups in the private and public sectors, including the marine-transportation in- dustry, offshore oil exploration and production in- dustry, and the U.S. Navy, which has an ongoing research program to develop applications for ocean-color data. 2 COMMERCIAL AND OPERATIONAL USERS' PANEL REPORT Panel Chairman: Dr. James R. Haustein Contributors: Cheryl Beck Pimporn Chavasant Ruth Fay Leo Fisher Art Haworth Jack Hill Thomas Leming Jon Malay John Maloney Peter Mitchell Vince Noble Hal Palmer Evelyn Putnam William Siapno Jan Svejkovsky Ron Tipper Matthew Willard Background The diverse interests of commercial and operational users of remotely sensed ocean data include commercial fishing, marine transportation, ocean mining, offshore oil and gas exploration and extraction, hydrology, marine ecology, naval operations, and value-added products, such as "fisheries-aids’ charts. Satellite-acquired data on ocean phenomena from the experimental Coastal Zone Color Scanner (CZCS) and the operational Advanced Very High Resolution Radiometer (AVHRR) have provided the basis for developing a number of important applications serving these interests. For example, the fishing industry has used data on sea-surface temperature, surface currents, and ocean color to improve catch efficiency, enhancing profita- bility. The marine-transportation industry uses remotely sensed ocean data primarily for ship routing. Ship-routing firms provide a route advisory to vessels being serviced prior to sailing via Telex and then update this advisory by satellite communications or marine radio every few days during the voyage. The goal of these services is to optimize the transit of a vessel, thus minimizing total cost. These costs include fuel, damage to equipment and cargo on board, crew injuries, delays due to adverse weather, and operating costs. Potential savings can be viewed in the light of the fact that between 600 to 800 larger vessels of the merchant fleet, occupied primarily in open-ocean trade, are en route each day. According to a recent unpublished study of approximately 25 voyages between the west coast of the United States and Japan from November to March, an average savings of over 20 hours per voyage were at- tributed to the use of ship-routing services. An improve- ment in the accuracy of weather prediction and the location of ocean currents and eddies would increase these sav- ings. The marine-transportation industry and the U.S. Navy also use ocean-current analyses and routine weather-chart analyses and prognoses for information on currents and visibility. These data products are disseminated either di- rectly via government services or are routed to users by weather-forecasting services. At this time, infor- mation on ocean currents is provided about twice a week, while visibility data can be obtained as often as four times daily. SeaWiFS data will provide a finer definition of ocean currents, re- sulting in the ability to take full advantage of fa- vorable circulation patterns for oceanic transit. SeaWiFS data will also provide information on horizontal atmospheric visibility. The oil and gas industry constructs offshore platforms for mining hydrocarbons, and the cur- rent state of technology Supports production in water depths greater than 1000 feet. These ex- ploration and production operations, particularly in the Gulf of Mexico, are costly and often very sensitive to environmental conditions. In these deeper drilling areas and off the edges of the continental shelf, an accurate and detailed un- derstanding of the oceanographic environment is required for platform design. For example, un- derestimating the potential force of the wind, waves, and currents in a drilling location may re- sult in underdesigning a structure with attendant risks. Conducting offshore operations, such as shipping supplies, pipelaying, and platform instal- lation, also requires a thorough knowledge of the ocean environment to determine "weather win- dows" when these operations can be conducted most safely and efficiently. The total drag force (a dominating constraint for steel-jacket structures used in the Gulf of Mexico) on a platform member is a function of the square of the total water particle velocity. For many ranges of water depths, particularly sea- ward of the continental shelf break, and for cer- tain types of structures, water particle motion from both orbital wave motion and ambient cur- rents must be considered. For offshore struc- tures in regions where eddy events are possible, an eddy force contribution must also be consid- ered as well as storm-generated effects. Timely information on transient mesoscale cir- culation features with maximum surface velocities in the 100 to 150 cm/sec range (e.g., the Gulf of Mexico Loop Current and eddies) is required, since they can cause a loss of drilling time due to increased loads on the drilling riser. Eddy moni- toring is also required to schedule other opera- tions, such as rig movement, remotely operated vehicle activities, and supply-vessel operations. Many potential users of satellite-acquired data are not equipped to receive these data and many do not possess the resources or technical ability to analyze and prepare the data products required to utilize the information. This has led to formation of a loosely organized, but growing, value-added industry that provides the data products to some members of the industries de- scribed above. For the most part, these emerg- ing entrepreneurs have small, poorly capitalized firms, and the cost of acquiring SeaWiFS data by them is a concern. In the public sector, the National Marine Fish- eries Service (NMFS) has been using ocean- color and sea-surface temperature data in oper- ational and research applications. Operational applications include identifying fronts, river plumes, upwelling, and other areas of high pro- ductivity for guiding research-vessel sampling, for providing timely reports to local fishermen of po- tentially favorable zones, and in predicting poten- tially lethal conditions for certain species, such as zones of oxygen depletion and pollution. Re- search applications include monitoring long-term changes in the environment and their effects on fisheries recruitment, pollution effects on both standing stock and recruitment, niche or habitat studies for specific fish stocks, and flow visualiza- tion for monitoring larval transport conditions in coastal waters for estuarine-dependent offshore spawning species. Other research interests in- clude determining the migration patterns of highly mobile species such as tuna, billfish, and marine mammals, improving fishery conservation and management techniques, and improving resource assessments. The U.S. Navy has not yet documented oper- ational requirements for the ocean-color data that will be acquired by the SeaWiFS sensor. As a result, its Current interest is in using SeaWiFS data in research programs to develop techniques and algorithms for deriving usable geophysical parameters for which the Navy has identified re- quirements. However, it is clear these data can be used to enhance the detail and timeliness of the oceanographic information currently used by the Navy and to supplement the meteorological data currently being received and used for fleet support. In this regard, the location of ocean features, such as fronts, eddies, and warm- and cold-core rings, is of prime interest. Their posi- tion and distribution is needed on a global basis in near real time. Sea-surface temperature measurements from the AVHRR sensor are currently being used by the Navy for frontal detection and as inputs into numerical models; SeaWiFS data will be an addi- tional source of information for these applica- tions. As described later in this section, in many instances ocean-color imagery has given a bet- ter indication of circulation patterns than the sea- surface temperature measurements acquired by the AVHRR. Other naval interests include the spatial and temporal distribution of atmospheric aerosols, water optical properties, water mass identifica- tion, prediction of bioluminescence, coastal char- acteristics and processes, and chlorophyll pig- ment concentrations. Naval ship and operational centers will need near-real-time coverage of these quantities once the Navy's research pro- grams have demonstrated their utility. There is also an interest on the part of the Navy in assessing the variability of these parame- ters in the oceans in the form of a digital atlas. The data now in the digital atlas are based on data acquired by the CZCS. Hence, when the SeaWiFS sensor becomes operational, these data will enable this investigation to be completed. Commercial Applications Fishing Industry As indicated above, sea-surface temperature and ocean-color data have been successfully utilized in increasing the efficiency of the fishing industry, and commercial fishermen on the U.S. West Coast are currently paying for satellite- acquired data products. The potential commer- es COMMERCIAL AND OPERATIONAL USERS' PANEL cial value of SeaWiFS to the fishing industry has been demonstrated with respect to the anchovy fishing fleet. Anchovy fishing occupies a sizeable portion of the West Coast fleet, and approximately 25 million pounds of anchovy are caught each year off the coast of Southern California. The northern extent of anchovy spawning areas in the California bight and the offshore ex- tent of spawning north of Santa Catalina Island are limited by cold, upwelling waters flowing from the north. These cold-water boundaries are eas- ily identified in thermal-infrared CZCS imagery. The southern limit of anchovy spawning can be defined using ocean-color measurements, since there is a direct correlation between chlorophyll concentration and spawning activity. Figure 1 demonstrates this correlation. In this figure, warm colors (yellow, orange, and red) depict high chlorophyll concentrations, and cool colors (green, aqua, and blue) depict lower concentra- tions of chlorophyll. The numbers overlaid on the image represent the number of anchovy eggs collected over a 20-day experimental survey. Another example of the use of ocean-color im- agery by the fishing industry can be drawn from the experience of shrimp fisheries in the Gulf of Mexico. As indicated in Figure 2, shrimp cannot live in areas where the concentration of oxygen in the bottom waters is low. Oxygen depletion often occurs when huge numbers of microscopic plants and other living matter die and sink to the bottom where decomposition takes place, deplet- ing the water of most or all of the oxygen. The amount of chlorophyll in the water is related to the biomass of the microscopic organisms and, hence, is an indicator of potential locations of oxygen-deficient waters. Figure 3 is an image from the CZCS showing the chlorophyll pigment concentration in the wa- ter off the Gulf Coast. The warm colors in this im- age (yellow, orange, and red) represent areas of high chlorophyll pigment concentration, and the cool colors (green, aqua, and blue) represent areas of lower chlorophyll concentration. Figure 4 shows a prediction of potential areas of oxygen-deficient waters, derived by combining the pigment-concentration data of Figure 3 with sea-surface temperature measurements. 7 PIGMENTS mg/m3 PT. CONCEPTION Figure 1. An-. chovy spawning limits defined by ocean color measurements. (Fiedler 1983) Figure 2. Relation- ship between bottom oxygen content and shrimp catch. (Leming and Stuntz 1984) LESS THAN 2 PPM OXYGEN MARSH ISLAND Figure 4. Correla- tion between high chlorophyll con- centrations, sea- surface tempera- ture, and waters with low oxygen content. (Leming and Stuntz 1984) MARSH ISLAND Figure 3. CZCS im- agery showing the chiorophyll pigment concentration in the water off the Gulf Coast. (Leming and Stuntz 1984) NEW ORLEANS. « 10 In Figure 4, the white crosses show the loca- tion of research vessels where the concentration of oxygen in the bottom water was found to be less than 2.5 mg/l; dots indicate areas where the concentration of oxygen was greater than 2.5 mg/l. This experiment, conducted by the NMFS (Leming and Stuntz 1984), demonstrates the utility of using ocean-color information to aid the shrimp fishing industry, which is valued at nearly $500 million annually. Another example of using ocean-color imag- ery to locate fish species is shown in Figure 5, also in the Gulf of Mexico. Here, large concen- trations of butterfish were found by NMFS re- search vessels in April 1985 in the region of the temperature and chlorophyll front (Leming and Herron 1986). As discussed in greater detail be- low, these fronts can only be detected in summer and fall through use of ocean-color imagery at these latitudes, partially because of the low tem- perature differentials in the ocean's surface and partially because the high humidity makes atmo- spheric correction impossible. Hence, a Sea- WiFS-type sensor will increase temporal cover- age for the Gulf of Mexico by at least 25 to 35%. MOBILE BA The prior three examples are drawn from ex- periments conducted with CZCS imagery. How- ever, the albacore fishing industry used similar imagery to increase its catch during the period of time when this imagery was available. More tuna is consumed in the United States than any other type of seafood — over a billion cans annu- ally — and albacore is the most valuable species of tuna. This species migrates to waters off the coast of North America during the summer and fall months, and commercially valuable aggrega- tions of albacore are found in the warm, blue waters near ocean-temperature and ocean- color boundaries on the seaward edge of coast- al water masses. For several years during the operation of the CZCS, the imagery was processed in real time to derive ocean-color boundary charts. The charts were distributed to fishermen at sea by facsimile, and color photographs of the images were also distributed by overnight mail to Sea Grant Marine Advisors and to fishing ports. Figure 6 is an ex- ample of a CZCS image that has been processed to delineate ocean color boundaries. The boun- daries between water masses are accentuated Figure 5. Butterfish catches are correlat- ed with high chloro- phyll concentration and temperature fronts. (Leming and Herron 1986) by false color enhancement. The greener coast- al waters are represented by red, orange, and gold. The bluer, oceanic waters are colored blue and aqua. Circles overlaid on the image show the location and size of albacore catch for a 6- day period in 1981, demonstrating that most of the albacore were caught along the seaward COMMERCIAL AND OPERATIONAL USERS' PANEL side of the ocean-color boundaries. These prod- ucts were used, not only by commercial albacore fishermen, but also by commercial swordfish and salmon fishermen in Southern California. The avail- ability of real-time data from SeaWiFS will greatly en- hance the ability of these industries to improve their cost-effectiveness. Figure 6. CZCS imagery, processed using computer enhanced false color to identify water color struc- ture. Commercial fish catch data are depicted on the image. (Montgomery et al. 1986) NO. FISH CAUGHT PER DAY 0-40 fe) 44-76 80-114 O O 127-750 @) COOL, TURBID WARM, CLEAR COASTAL WATERJOCEANIC WATER 11 Ocean-color imagery also has potential com- mercial applications in the recreational sportfish- ing industry. For instance, most large gamefish, such as sailfish and marlin, are nearly always found in the blue water typical of open-ocean conditions. An operational map of distance and heading to the nearest blue water from selected sportfishing ports or marinas would be an attrac- tive commercial value-added data product. Fig- ure 7 is an example of such a map of the north- ern Gulf of Mexico derived from CZCS data. Al- ternatively, the availability of SeaWiFS data at a central site would also be extremely valuable to the sportfishing industry in reducing the time and fuel now spent searching for blue water. Offshore Oil and Gas Exploration and Production AVHRR sea-surface temperature data cur- rently are major sources of the information used in preparing eddy forecasts for offshore oil explo- ration and production (Haustein and Vastano 1987). Temporal changes in eddy size and posi- Figure 7. Distance in nautical miles and heading in degrees (from true North) from selected ports to the nearest blue water in the northern Gulf of Mexico on 9 May 1982. (Courtesy of T. Leming.) tion and current frontal locations are used to produce routine summaries of their positions, surface-flow directions, and estimates of their probability, duration, and magnitude. Figure 8 shows a typical summary. However, the utility of thermal-infrared sea- surface temperature measurements deteriorates seriously from the summer through fall in the Gulf of Mexico and in many other regions at latitudes between 30° South and 30° North (e.g., the equatorial Atlantic and Pacific Oceans and the Indian Ocean). First of all, during these months surface conditions are relatively isothermal as a result of strong solar heating of the surface layer, with temperature ranges in the narrow band from about 29 to 31°C. Secondly, humid atmospheric conditions cause a severe attenua- tion of some regions of the thermal-infrared sig- nature. The limitations due to surface heating are greatest when the surface is calm and solar intensity is high. In some instances the ocean's features are masked, significantly diminishing the usefulness of the data. PA So@MOB. BY PENS CHOC By 175 180 Ve 18 160 RAN CY 080 30 24 GULF OF MEXICO EDDY MONITORING FOR OFFSHORE OPERATIONS VALID DATES: 11/6-13/85 IMPORTANT OBSERVATIONS: Narrowing of Loop Current neck indicative of potential eddy detachment in the next —_-- few weeks. GALVESTON . BROWNSVILLE LOOP CURRENT IIG wath eye cay 44 ARROWS INDICATE DIRECTION OF FLOW DRILLING AND PLATFORM SITES: G C = GREEN CANYON SYNOPSIS OF FEATURES EDDY ID CENTER MOTION LAT LONG TO SPEED 85A 25.3 92.8 W 2.5 n.mi./day VELOCITY 1 to 2 knots DRILLING AND PLATFORM SITES SITE EDDY POTENTIAL START DURATION GC None at this time MAX EXPECTED Less than 1 knot An example of thermal-infrared imagery un- der these conditions is given in Figure 9. In this TIROS channel-4 (11 um) image, only the north- ern boundary of the Loop Current can be ob- served in the northeastern Gulf. In contrast, Figure 10 shows the CZCS imagery taken on the same day.° In this figure, regions with high chlo- rophyll concentrations are denoted by the light- est colors and those with low concentrations by darker colors. Clouds are shown in black. Many ocean features are clearly observable in this imagery. For instance, the continuous boundary of the Loop Current can be seen as it This image was processed to eliminate the atmospheric com- ponent using a Principal Component technique (Holyer and LaViolette 1984), although similar results can be obtained us- ing the more typical Gordon subtraction atmospheric removal technique. MAXIMUM SURFACE SURFACE VELOCITY Figure 8. Typical summary of eddy and current-jet locations used by the offshore oil exploration and production industry. (Courtesy J. Haustein) enters through the Yucatan Channel and mean- ders to its eastern extent. Two eddies can be observed in the western Gulf, and, within the shelf waters off Louisiana, Mississippi, Alabama, and Florida, the mixing patterns of these waters can be identified as significant fronts. It should be noted that the imagery in Figure 10 has been processed to the end of the swath in the western Gulf. Although these data can- not be subjected to quantitative analysis, the ocean's features clearly can be seen at the out- ward extent of the CZCS's 40° scan, document- ing that useful data can be obtained from CZCS imagery at scan angles greater than 30° from nadir. Despite the fact that a scan angle of 58° will be required to provide daily coverage from the Landsat-6 orbital altitude, the value of hav- ing daily coverage is enormous, even if some of the data can only be interpreted qualitatively. COMMERCIAL AND OPERATIONAL USERS' PANEL 13 14 Figure 9. TIROS thermal- infrared imagery of the Gulf of Mexico, 20 June 1979. (Courtesy of R. Arnone) Figure 10. CZCS imagery of the Gulf of Mexico, 20 June 1979. (Courtesy of R. Arnone) Operational Applications Navigation and Ship Routing As indicated earlier, the location of eddies, fronts, and currents is important for maritime and naval applications. The importance of ocean- color imagery to these uses is demonstrated in. Figures 11 and 12, both taken 12 May 1986, sep- arated in time by 14 hours. The thermal image from the AVHRR shown in Figure 11 indicates there is a warm spot in the center of the image below Majorca, Spain (represented by dark gray shades). During this period, ship and aircraft sur- veys registered calm sea conditions and high so- lar heating. The upper 1 meter of the water was reported to be as much as 3°C warmer than the lower layers. Hence, in interpreting this image, consideration must be given to the fact that sur- face heating may mask the actual circulation pat- terns. In the imagery of Figure 12 there is no evi- dence of biological distribution patterns below Majorca usually associated with warm water sur- rounded by colder water. Since the radiance leaving the water emanates from a depth of ap- proximately one attenuation coefficient (typically 4 to 20m, depending on turbidity), the imagery rep- resents the circulation patterns below the heated surface of the ocean. Since the ground-truth data indicates high solar heating that may mask the actual circulation patterns, it can be conclud- ed that the general circulation patterns of the ocean are better represented by biological distri- bution patterns than by surface thermal patterns under certain conditions. Hydrology The utility of satellite-acquired imagery in monitoring floods was also demonstrated using CZCS data. For example, Figure 13 is imagery acquired by the CZCS of the Parana River Valley in Argentina. The flooded area extends 700 km from the confluence of the Rio Parana to the Rio COMMERCIAL AND OPERATIONAL USERS' PANEL de la Plata near Buenos Aires and ranges from 20 to 70 km in width. While data from stream gauges can often provide warning of impending flood conditions, they do not provide information on the extent of flooding, which may be of critical importance to rescue or relief operations. Surveying, Monitoring, and Managing of Inland and Coastal Fisheries Compared to conventional ground-sampling techniques, remotely sensed data from inland and coastal fishing areas are more cost-effective for gathering data, if the data are received in a timely fashion or in near real time. This is especially true in sparsely populated, developing countries where communications are poor and environ- mental data are not available. Welcomme (1985) has enumerated the surveying and monitoring functions that can be accomplished using satellite imagery. A brief summary of those functions that can only be accomplished using data acquired by a SeaWiFS-type sensor is presented below. The potential fishery output of rivers has been found to be directly related to the flooded area of the river, i.e., catches in flood-plain rivers in a particular year are correlated with the flood intensity of the previous year (Welcomme 1985). Welcomme also found that macrophytes tend to tie up nutrients for longer periods than phyto- plankton. Data from a sensor like SeaWiFS can be used to measure macrophyte growth, phyto- plankton growth, and the extent of the drawdown of water bodies. The seasonal turnover and even upwelling can also be efficiently monitored. The same kinds of information can be ac- quired on coastal waters where circulation pat- terns are better defined, due to the increased flows and often higher color-to-temperature con- trasts between various water masses. These areas are often large and remotely located and, therefore, best assessed through use of satellite- acquired data. 16 Figure 11. Thermal- infrared Imagery of the Mediterranean, 12 May 1986. Pigments con- centration ratio 443:550 nm. (Courtesy of R. Arnone) | ALGERIA Figure 12. CZCS imagery of the Mediterranean, 12 May 1986. (Courtesy of R. Arnone) ss ee 06 COMMERCIAL AND OPERATIONAL USERS' PANEL Figure 13. Flood monitoring based on CZCS imagery. (Courtesy of Organi- zation of American States and Satellite Hydrology, Inc.) WZ, 18 Seafood, such as shrimp, oysters, crabs, and clams, are often cultured and harvested in the coastal ecosystem, and fish-related aquaculture activities are also increasing in these areas. Data from the SeaWiFS sensor will be valuable in moni- toring and managing these resources. For exam- ple, the opening and closing of shrimp grounds has traditionally been related to catch information in conjunction with water temperature and sus- pended sediment data. The SeaWiFS sensor sys- tem will also provide excellent seasonal water quality information that can be used to locate the best sites for new aquaculture facilities. Supporting Research Issues Except for the value-added industry, most po- tential users of processed data are not trained in its use or interpretation. For example, experience gained while distributing CZCS data to the fisher- ies industry showed that substantial user support is required before the information is put to its ap- propriate use and, hence, considered to be of value by the user. Commercial users need to be able to test the potential of applications of interest to them, including the compatibility of the system with existing software and hardware processing packages. Potential applications using SeaWiFS data should be demonstrated far enough in ad- vance of data availability that commercialization can commence immediately after launch. Hence, a study should be undertaken by the research community to establish the utility of Sea- WiFS-type data, based on AVHRR and historical CZCS data, for specific commercial applications. Tutorial sessions with members of associations representing potential users and user workshops are likely to lead to an improved perception of the value of the data and increased use of it. The following examples of ongoing research in support of operational uses of SeaWiFS data are drawn from the Navy's research program. However, much of this research is applicable to other users. In a research program funded by the Office of Naval Research (ONR), general water-mass classification is being developed by coupling satellite-derived bio-optical data with sea-surface temperature data. Since the information content in the visible bands and in the thermal-infrared bands is different, combining these data reveals improved methods of viewing the ocean surface and, therefore, of classifying ocean waters. At this time this is a basic research program and, hence, does not describe an operational require- ment of the Navy. However, SeaWiFS would be an ideal sensor for this work since the visible and infrared data will be coregistered. Basic research at ONR is also being directed toward assessing the biota using ocean-color properties. This research reflects the Navy's in- terest in ambient noise from marine life and in bio- luminescence. The occurrence of specific phyto- plankton pigments and their concentration are re- lated to data acquired on ocean color, and re- search is being directed toward determining a mechanism for isolating the phytoplankton groups responsible for bioluminescence from the spectral signature. Frontal locations can also be correlat- ed with the probability of the presence of marine life. Hence, data from the SeaWiFS sensor could be applied to this research and, if the research were successful, an operational Navy require- ment might result. Thermodynamic ocean models are being de- veloped for naval programs that require a knowl- edge of the absorption of solar heat by the ocean. The absorption in the near-surface layer and the dissipation of this heat are partially con- trolled by the diffuse attenuation coefficient, k, of the water. That is, the depth to which solar heat penetrates into the water column is inversely re- lated to the water's attenuation coefficient. The extent of this effect has not been determined, since the horizontal and temporal scales of varia- tion in water types are not known. However, pre- liminary studies have shown the effect of water type on resulting circulation and mixed-layer depth prediction calculations (Martin 1985). Sea- WiFS data will be used as an input into the Navy's thermodynamic model, although basic research will be required to determine how these data can be interpreted. es COMMERCIAL AND OPERATIONAL USERS' PANEL The distribution of aerosols in the atmos- phere, as defined by the 670 and 750 nm bands of the CZCS, is of significant importance to the research of the Navy's meteorological community, since there is a strong naval re- quirement for surface horizontal atmospheric visibility. The Naval Environmental Prediction and Research Facility (NEPRF) is examining ways of using data on integrated aerosol distri- bution for naval needs. Although basic re- search will be required to define the specific application, SeaWiFS will provide improved data for meeting this requirement. The Navy also needs to establish a tempor- al and spatial optical property (diffuse attenua- tion coefficient) data base, which can be used to establish scales of variability and to develop models that predict their distribution (Esaias et al. 1986). These data can only be acquired from a satellite platform with a sensor like the proposed SeaWiFS. 20 3 RESEARCH USERS' PANEL REPORT Panel Chairman: Dr. Otis B. Brown Contributors: Mark Abbott Robert Arnone Stephen Colgan Peter Cornillon Curtiss Davis Frank Eden Richard Eppley Catherine Gautier Mary Hughes John Kermond Charles McClain Erik Mollo-Christensen Eni Njoku Mary Jane Perry Mike Reeve William Sackett Raymond Sambrotto Raymond Smith John Steele Fran Stetina Phillip Taylor Ron Tipper Paul Uhlir John Walsh Stan Wilson Joe Wroblewski Charles Yentsch James Yoder Background Photosynthesis by land and ocean plants converts carbon dioxide into plant tissue and is one of the most important natural processes that removes carbon diox- ide from the atmosphere and oceans. Marine phyto- plankton are responsible for at least 30% of the total global photosynthesis, and recent studies suggest that phytoplankton photosynthesis may be underestimated by a factor of two. Phytoplankton photosynthesis is a key process in controlling the biogeochemical cycles of carbon, nitrogen, phosphorus, sulfur, and oxygen. These elements play major roles in controlling the glo- bal environment, and understanding their cycles is a major goal of the emerging field of Earth System Science. Phytoplankton contain chlorophyll and other pig- ments that capture sunlight, which provides the energy required for the photosynthetic process. Chlorophyll is a green pigment, and the color of water changes from blue to green as the concentration of phytoplankton and, hence, chlorophyll increases. As a result, phyto- plankton concentration and, thus, the photosynthetic potential of ocean waters can be estimated in most of the global ocean by measuring ocean color. As dis- cussed in Section 1, the possibility of measuring the photosynthetic potential of the sea from a satellite- borne sensor led to a ‘proof-of-concept’ mission, the Coastal Zone Color Scanner (CZCS) on the Nimbus-7 satellite. Once oceanographers verified the chlorophyll dis- tribution patterns revealed by CZCS imagery, the use of the imagery revolutionized biological oceanography. For the first time, oceanographers could obtain meas- urements of a biological property over large areas of the ocean. The concentration of phytoplankton varies greatly in space and time because the growth medium, water, is in constant, three-dimensional motion. Until CZCS imagery was available, biological oceanogra- phers were generally restricted to studying relatively small-scale phenomena, since ships cannot cover 21 22 enough area in a sufficiently short period of time to synoptically sample at ocean-basin or global scales. In the future, oceanographers will be able to use SeaWiFS imagery to solve large-scale problems, such as the role of phytoplankton pro- duction in the global carbon cycle. It is possible to consider such ambitious goals for the future partly because of the successful integration of CZCS imagery into studies of relatively small-scale systems. The remainder of this section consists of a brief review of some of the scientific uses of CZCS imagery, a description of how SeaWiFS im- agery will be used in the early 1990s, and a dis- cussion of scientific research requirements for the SeaWiFS system. Studies of Small-scale Processes Small-scale ocean features, i.e., features en- compassing less than about 10,000 km? of ocean area, generally form and dissipate within relatively short periods of time (days to weeks). The pre- dominant use of CZCS imagery has been in con- ducting studies of small-scale features in the ocean because, until recently, small-scale fea- tures were of greatest interest to biological and chemical oceanographers. The dimensions of these features are clearly visible in satellite imag- ery. In contrast, mapping small-scale features from oceanographic research vessels is difficult, if not impossible, because the features change faster than the ships can map them. Small-scale studies will continue to be an important applica- tion for satellite-acquired ocean-color imagery, since the results of such studies are the building blocks upon which programs to study large-scale processes are built. River Plumes Riverine and estuarine plumes contain rela- tively high concentrations of suspended organic and inorganic material that are highly reflective in the visible spectrum. This high reflectance is easily observed by satellite-borne color scanners, such as the CZCS. An issue currently being de- bated is the fate of fluvial nutrients and their pos- sible effect on carbon budgets. Simply stated, "Do the nitrates and phosphates produced from agricultural and urban sources and injected via freshwater discharge into the coastal zone result in a significant enhancement in primary produc- tion?" To answer this question requires an un- derstanding of the sedimentation and circulation processes that control the exchange of material across the continental shelf. Ocean-color imag- ery is beginning to provide answers to such questions by providing time-series imagery of plume formation and dissipation on continental shelves and insight into other processes that af- fect the rate at which river and ocean water in- termix. Coastal Upwelling Vertical movement, or upwelling, of deep, cold, nutrient-rich water is an important process in the marine ecosystem. Upwelling areas tend to be highly productive and are often the site of important fisheries, such as the anchovy fishery off the Peruvian coast. Upwelling is largely caused by wind stress and may occur in the coastal ocean and deep sea. Winds favorable for upwelling are episodic, varying on time scales of 3 to 5 days and on length scales from a few tens to several hundreds of kilometers. In freshly upwelled waters, phytoplankton grow faster than zooplankton can consume them, and, as a result, a large fraction of the phytoplankton may sink to the bottom. Thus, sites of wind-driven upwelling are important in understanding the ocean's role in the global carbon cycle. Studies of wind-driven upwelling systems off the U.S. West Coast revealed that their extreme variability is difficult to resolve using traditional ship sampling. Hence, satellite imagery is a ne- cessary tool for resolving upwelling dynamics and, perhaps more importantly, for determining the large-scale effect of these systems. For in- stance, CZCS and AVHRR imagery showed for the first time that plumes of upwelled, productive waters extend hundreds of kilometers seaward off the U.S. West Coast, as illustrated in Figure 14. A time series of imagery extending over many years will be required to quantitatively deter- mine the coupling between upwelling and large- scale patterns in ocean basins. Seasonal Phytoplankton Blooms During the vertical mixing process in winter, deep waters rich in plant nutrients are mixed with near-surface waters that are depleted of nutrients. The net effect is fertilization of the upper layers of the ocean and stimulation of rapid phytoplankton growth as the daily sunlight increases in the spring. Figure 14. Plumes of chlo- rophyll-rich wa- ters extend many kilometers off the U.S. West Coast. (Courtesy of M. Abbott) This period of rapid growth and accumulation of phytoplankton biomass in the mixed layer is called a "spring phytoplankton bloom" and is illustrated in Figure 15. The spring bloom is one of the ma- jor events in the sea and is a time when the flux of dissolved carbon dioxide into phytoplankton bi- omass is very rapid. Thus, spring blooms in the global ocean may play an important role in the global carbon cycle. Satellite ocean-color meas- urements provide the only means of answering questions concerning the large-scale distribution and timing of spring blooms in the global ocean. 23 24 Figure 15. Spring bloom in the North Atlantic. (Courtesy of G. Feldman and W. Esaias) Western Boundary Currents and Eddies Eddies and other physical processes asso- ciated with the large horizontal shears in the Gulf Stream and other major ocean currents give rise to significant lateral mixing and cross-frontal en- trainment. The resulting exchange of physical, chemical, and biological properties often results in a large modification of the local environment causing noticeable changes in the distribution of animals and plants at or near the frontal inter- face. Fishermen routinely make use of such con- ditions to locate commercially exploitable quanti- ties of fish that tend to congregate along oceanic fronts in search of prey. The variety of ocean eddies and the different environments in which they are found are the basis for a great diversity in physical and biologi- cal effects. For instance, eddy systems observed off the U.S. West Coast draw plumes of cold, pigment-rich coastal waters offshore. This pro- ~ PHYTOPLANKTON PIGMENT mg m3 05.1.2 .3.4.5.6.7.8 .9 1 31030 cess is an important mechanism for enriching off- shore waters with plankton and nutrients. Gulf Stream eddies off the U.S. East Coast north of Cape Hatteras, NC, constitute an important mech- anism for exchanging chemical and biological properties between coastal and offshore waters. CZCS imagery, such as shown in Figure 16, and AVHRR observations provided the first synoptic view of Gulf Stream eddies and showed how ed- dies are formed, how long they last, and where they go during their lifetime. It is clear the processes associated with mix- ing along the edge of eddies, coastal currents, western boundary currents, etc., are not only quite complex, but also that they vary greatly from one region and oceanographic feature to the next. Given their importance in the mixing of oceanographic parameters (salinity, temperature, biological populations, etc.), a better understand- ing of this variability is critical to gaining a better understanding of the distribution of oceano- graphic parameters in general. Figure 16. Chlorophyll- rich continen- tal shelf waters off the U.S. East Coast contrasted with less pro- ductive off- shore water. A Gulf Stream ring is forming in the right center of the image. (Courtesy of O. Brown and R. Evans) 25 26 Mixed-Layer Optical Properties Recent studies of mixed-layer dynamics have shown that it is essential to characterize the opti- cal properties of the upper water column. The absorption of solar radiation and its variation with depth can greatly affect the vertical stability of the water column, and variations in pigment con- centration are largely responsible for variations in optical properties in most of the world's oceans. The stability of the water column has a major effect on primary production by controlling nutrient Supply and the effective solar radiance captured by the phytoplankton. Vertical mixing a may influence the air-sea interaction and the cli- mate. The availability of global data on marine so affects sea-surface temperature and, hence, optical properties, combined with global sea- surface temperature and wind measurements, will improve our understanding of the complex interaction between physical and biological properties in the upper ocean. Flow Visualization An often-overlooked contribution of satellite- acquired imagery of ocean color or temperature fields to oceanographic research lies in the op- portunity it offers to visualize flow fields. It is dif- ficult to quantify such a contribution, but often the insight gained by examining a satellite image gives rise to new discoveries. For example, en- trainment of streamers around a large warm- core eddy can be observed in the CZCS imagery of the Gulf Stream. This process was unknown until CZCS imagery was available. Statistical techniques are currently under development that can be applied to satellite thermal and color data to better quantify ocean flow fields. Con- current and coregistered AVHRR and CZCS im- agery can also be used to study and statistically describe mixing between two different water masses. Studies of Global-Scale Processes The recent widespread distribution of CZCS imagery in the oceanographic community has stimulated ambitious plans for oceanographic Figure 17. A composite CZCS image showing the distribution of chlorophyll in the global oceans dur- ing December, 1981. High concentrations (over 4 ug/l) of chlorophyll (phytoplankton) are indi- cated by orange and red, whereas low concentra- tions (less than 0.5 ug/l) are indicated by blue. (Courtesy of GSFC and the Univ. of Miami) studies in the 1990s. For example, scientists in the United States and abroad are planning the Global Ocean Flux Study (GOFS) to better quanti- fy the ocean's role in the global carbon cycle and other major biogeochemical cycles. Ocean-color measurements are required to implement the scientific strategy of GOFS and other programs whose goals include the study of primary produc- tion on a global scale. Acquisition of data on ocean color is the key to the success of these studies, because these data are the only global measure of ocean biota that can be obtained within a relatively short period of time (days). Fig- ure 17 is an example of the global images that can be obtained from satellite ocean-color meas- urements. 27 28 The Global Carbon Cycle Over the last few decades, our knowledge of the Earth's oceans, atmosphere, continents, and ice cover has increased dramatically. The inter- action and balance among these elements of the biosphere are being increasingly appreciated, as is their influence on man and human society. Most change in the global system is natural, due to such causes as volcanic activity and changes in the Earth-to-Sun distance, but evidence is ac- cumulating that human activity also plays a major role in aspects of global ecology that directly af- fect the Earth as a unique home for life. The steady increase in the carbon dioxide content of the atmosphere associated with the burning of fossil fuels is a well-documented exam- ple, but the cycles of other biogenic gases, such as nitrous oxide, methane, and carbon monoxide are also affected by anthropogenic activity. These gases also contribute to the heating of our atmosphere through their property of absorbing infrared radiation (i.e., the "greenhouse effect"). With respect to carbon dioxide, at the present rate of increase of about 1.5 ppm per year, the concentration of carbon dioxide in the atmos- phere is expected to double relative to pre- Industrial-Age levels sometime in the next century. The other biogenic gases mentioned above are also increasing in the atmosphere and contributing to the greenhouse effect. Thus, some atmospheric models predict a gradual warming of the Earth's climate with as-yet- unknown consequences. The pathways and rates of removal of carbon dioxide from the atmosphere have not been de- finitively established, but it is known that about 50% of the carbon dioxide released from burning fossil fuels has accumulated in the atmosphere, and most of the remainder is in the ocean. To provide quantitative answers to questions con- cerning the ocean's role in the global carbon cycle and to predict the fate of anthropogenically derived carbon dioxide that reaches the ocean, observations and models must focus on key as- pects of the ocean's biogeochemistry. The Role of Phytoplankton in the Global Carbon Cycle The role of ocean biota in the global carbon cycle is understood qualitatively. Marine phyto- plankton carry out photosynthesis, converting in- organic carbon dissolved in the water to organic particles and dissolved organic materials. This process is known as primary production. The rate of primary production varies by as much as a factor of ten from ocean region to ocean re- gion, and, thus, some parts of the ocean are re- ferred to as being more productive than others. Much of the organic carbon produced from pho- tosynthesis is eaten and recycled back to inor- ganic carbon in the surface waters by animals and bacteria. The residual organic matter, along with associated inorganic skeletal components, such as calcite, aragonite, and opal, settle out of the surface waters. A small fraction of this flux is ultimately buried in the sediments and potentially represents an important mechanism for removing carbon from the global cycle. Ocean Productivity Measurements on a Global Scale The magnitude and variability of annual pri- mary production by marine phytoplankton is poor- ly specified on a global scale, largely due to the high degree of spatial and temporal variability in the distribution of phytoplankton in the sea. As noted previously, phytoplankton primary produc- tion accounts for at least 30% of the total annual global photosynthesis, but this percentage is not known with the level of accuracy required to ac- curately model the role of phytoplankton in the global carbon cycle. Recent studies suggest that phytoplankton photosynthesis may be underesti- mated by a factor of two; this uncertainty partially accounts for the difficulties encountered when attempting global-scale analyses using traditional oceanographic sampling methods. Only through satellite remote sensing of ocean color can information on marine primary production be obtained on a global scale, given es MESEARCH USERS' PANEL that significant changes occur over short periods of time (days to weeks) and over small distances (10 to 100 km). In much the same way that meteorologists use Satellite data as input to models that predict the weather, oceanographers will input satellite- acquired measurements of ocean chlorophyll into computer simulation models to improve predictions of the state of ocean ecosystems and their effects on the biogeochemical cycles of carbon, nitrogen, phosphorus, sulfur, and oxygen. In both cases, sat- ellite data provide global coverage that is impracti- cal to obtain in any other manner. Thus, satellite- acquired ocean-color imagery is essential to the de- velopment and verification of accurate models that quantify the role of ocean biota in the major biogeo- chemical cycles — the key to understanding the glo- bal ecosystem. The acquisition of global ocean chlorophyll measurements from the CZCS instrument was an im- portant first step that moved the field of oceanography toward a new global perspective on the couplings between atmosphere and ocean and the special role of phytoplankton primary production in biogeochemical cycles. The acquisition of Sea- WiFS global data is essential if this new approach in oceanography is to develop and mature. Mission Support Science Scaling up from the present focus on small-scale studies of phytoplankton biomass (chlorophyll) distri- butions to the goal of providing global estimates of primary production in the 1990s will require ocean- color and sea-surface temperature data on a global scale. It will also require conducting the experi- ments necessary to understand the relationship of small-scale to basin-scale distributions. This subsec- tion briefly outlines a science plan for making the transition from small scale to ocean-basin and global scales. Three initiatives are proposed in the mission- support science plan for SeaWiFS. The first.is a se- quence of cooperative international studies using high-resolution ocean-color observations of an ocean basin to address stratified sampling issues. The second is an expanded effort to improve bio-optical relationships for the SeaWiFS band set and to develop and verify a physiologically based algorithm for productivity estimates. The third is to collect SeaWiFS observations globally and to composite them into moderate-resolution maps of pigment and primary productivity. Ocean Basin Study A detailed study of one ocean basin using SeaWiFS imagery and mooring and ship data is essential to bridge the gap from current applica- tions of CZCS imagery to ocean-basin scales. Physical processes, for the most part, control phytoplankton distribution and productivity, and, generally, physical processes at small scales are dominated by local wind-forcing and eddy-scale features. At the ocean-basin scale, global oceanic and atmospheric circulation patterns predominate, but eddies and local wind forcing significantly modify the overall pattern. The bio- logical consequences of basin-scale physical processes have not been studied. The GOFS and other international programs planned for the early 1990s will collect much of the essential data required to study ocean basin- scale primary productivity. What is needed is a focused effort, in collaboration with these pro- grams, to process both the high- and low- resolution SeaWiFS data for the North Atlantic, or another appropriate ocean basin, simultaneously with in-situ optical and biological measurements. This kind of multiplatform study would be an es- sential first step toward the goal of obtaining global-scale productivity estimates. Bio-Optical Modeling Spatial variability in primary production is cur- rently being investigated by means of satellite sensors. On the other hand, low-frequency (months to years) temporal variability at a given location is best investigated from moored arrays, 99 30 which can provide continuous long-term data at a single location and as a function of depth in the water column. Vertical strings of bio-optical sen- sors, deployed strategically in the major ocean provinces, are required to provide the comple- mentary surface information necessary to fully exploit the scientific return from the SeaWiFS sat- ellite data. Unattended buoy systems would pro- vide the long-term bio-optical data from various ocean provinces and would be used (1) to inves- tigate both the long-term and vertical-distribution behavior of bio-optical algorithms, thus increasing the accuracy of those models, linking the dis- solved and suspended biological material to the subsequent optical properties, (2) as a platform for the direct long-term determination of the verti- cal distributions of pigment biomass, primary pro- duction, and ocean carbon flux, and (3) as a component of the multiplatform stratified sampling strategies for optimizing remotely sensed esti- mates of pigment biomass, primary production, and carbon flux. Validation of the SeaWiFS data product will require at least one dedicated cruise of at least 30 days in addition to a "calibration" cruise short- ly after launch. Similar cruises during the opera- tion of the sensor will confirm its on-going perfor- mance and stability. The cruises should be de- voted to measuring pigment concentration con- tinuously along the ship's course as well as up- welling spectral irradiance, downwelling spectral irradiance, pigment concentration, etc., at posi- tions within the field of view of the sensor. This data will also provide a basis for developing bet- ter bio-optical algorithms. Remote sensing of ocean color with the four CZCS visible channels is well understood. It is based on firm physical principles of radiative transfer and environmental optics as well as on a considerable body of experimental data linking biological constituents in ocean waters with their corresponding optical properties. Additional spectral bands are proposed for SeaWiFS that should greatly improve the accuracy of chloro- phyll estimates, particularly in areas with high chlorophyll concentrations and with suspended sediments or dissolved organic matter (Case-2 waters). There is also significant room for im- provement in the algorithms used for estimating primary production from ocean-color imagery. In particular, a robust and general algorithm for the purpose of handling imagery from various regions and over long time periods is needed, such as would be required in order to make basin-wide productivity estimates from color imagery. Re- cently, several biological optical models that could fill this need have been proposed. A syste- matic effort is required to evaluate, test, and re- fine these models using sample data from a wide variety of ocean environments. The objective is to develop a generally agreed-upon algorithm by the time SeaWiFS is operational, so that we may proceed to produce global ocean productivity maps in support of GOFS and other studies planned for the early 1990s. To achieve the accuracy in pigment- concentration estimates associated with the CZCS, the existing CZCS atmospheric-correction algorithm can be directly adapted to SeaWiFS data. The bands at 665, 765 and 865 nm, dis- cussed in Section 4, where the ocean approxi- mates a blackbody, will be used to determine the aerosol radiance and its spectral variation. How- ever, some studies will be necessary to establish the most accurate method of extrapolating the spectral variation in these bands into the visible region. To take advantage of the 10-bit sensitivity of the SeaWiFS sensor, compared to the 8-bit sensi- tivity of the CZCS, a more careful analysis of at- mospheric correction will be required. The as- sumption that Rayleigh and aerosol contributions to the radiance at the sensor can be separated will not be valid at the full 10-bit resolution of the sensor, and a more complex algorithm will be needed. Development of such algorithms has been underway for 4 to 5 years, their feasibility has been demonstrated, and they will be in place by launch. These improved algorithms should enable correction of atmospheric effects almost to the 58.25° edge of scan of the baseline Sea- WiFS instrument. Global Compositing of Chlorophyll and Productivity As indicated in Section 5, part of the data processing planned for SeaWiFS data is to pro- duce global maps of phytoplankton chlorophyll. Before these products can be incorporated into RESEARCH USERS' PANEL GOFS and other studies, the users must under- stand the limitations of large-scale composite im- agery. Thus, a project will be required to provide a firm assessment of large-scale sampling statis- tics and to perform initial comparisons with high- level (binned and averaged) correlative data sets. 32 4 SYNTHESIS OF REQUIREMENTS The issues surrounding the questions of what spectral bands and other sensor characteristics would best serve the users’ needs and whether the desired characteristics could be implemented within acceptable cost and risk constraints were discussed at length in all of the panel sessions at the in- itial workshop meeting. Considerable discussion also focused on defining the required revisit interval and data-processing, downlink, data-format, and dissemination requirements. The plenary sessions served to expose the positions of the panel members and to focus attention on the salient characteristics desired. Much of the second workshop meeting was devot- ed to working out viable compromises among the positions represented. This section presents the views expressed and the agreements reached. Sensor Requirements The point of departure for developing sensor require- ments for the SeaWiFS was the sensor parameters and per- formance of the CZCS, summarized in Section 1. The char- acteristics relevant to formulation of requirements for the SeaWiFs are repeated below: Spectral Bands [cen [eonen | CM [aaa Chlorophyll Reference Gelbstoffe, sediments Chlorophyll Surface vegetation Surface temperature Scan Plane Tilt: +20° along track Digitization: 8 bits 33 34 Spectral Band Selection The CZCS demonstrated the feasibility of de- termining ocean chlorophyll concentrations and diffuse attenuation coefficients from multispectral, visible, satellite-acquired observations. The goal of the SeaWiFS Working Group's band-selection process was to recommend a baseline set of bands that would be capable of providing the data required to resolve chlorophyll concentra- tions to within 50 percent over a range of con- centrations from 0.05 ug/l in the open ocean to 10.0 ug/l in outer continental shelf areas. This is a major goal for a follow-on ocean-color sensor to the CZCS (JO! 1984, 1985). Visible and Near-Infrared Bands The topic of spectral band selection for Sea- WiFS was introduced by the instrument design experts by proposing the following baseline band centers in the visible and near-infrared regions: 443, 500, 565, and 765 nm. The band at 443 nm is near the absorption maximum of chlorophyll at 435 nm, but its location minimizes interference from a Fraunhoffer absorption line (G) that oc- curs near 435 nm. The 500 nm band is between the maximum and minimum regions of pigment absorption, so it can be used to estimate pigment concentration when the concentration is so large that useful signals cannot be derived from meas- urements at the absorption peak. The 565 nm band is near the absorption minimum of phyto- plankton pigments, and the 765 nm band is in the near-infrared region where water can be consid- ered black, enabling use of data from these bands in atmospheric-correction algorithms. Since the instrument designers indicated that two bands could be added in the visible/near- infrared (VNIR) rather easily with only a minor in- crease in cost, in the ensuing discussion several other bands were suggested. For example, a band centered at 665 nm was requested for at- mospheric correction instead of the CZCS band at 670 nm to avoid the strong overlap of the 670 nm band with the in-vivo sunlight-induced fluores- cence feature of chlorophyll, centered at 685 nm. Although the SeaWiFS band center would be 5 nm lower than the CZCS band center, it would still permit existing CZCS algorithms for atmo- spheric correction to be used. This was consid- ered essential, since time will be required to de- termine the optimum techniques for using the new 765 nm band for estimating aerosol radiance, and because it is important to have direct compari- sons between historical CZCS data and SeaWiFS data to provide continuity in the study of long- term trends in marine productivity. After the atmospheric-correction algorithms for the 765 nm band have been validated, the 665 nm band will be useful in developing new algorithms for esti- mating pigment concentration (Clark 1981) and in assisting in the effort to extrapolate Angstrom ex- ponents from the near-infrared region to the visi- ble. As a result of these discussions, both panels agreed that the following five VNIR bands should be included in SeaWiFS as a minimum set: 443 +10 nm, 500 +10 nm, 565 £10 nm, 665 +10 nm, and 765 +20 nm. Data from these bands would be used for the purposes identified in Table 2. After agreement on adding a band at 665 nm was reached, the possibility of adding a sixth band was explored. It was felt that this opportu- nity should be exploited to improve accuracy and the number of optical properties of the ocean that could be derived in the presence of multiple con- stituents. The spectral position of this band was debated at length, using as a guideline that the position of the selected band should not have a significant influence on the cost or complexity of the instrument. SYNTHESIS OF REQUIREMENTS Table 2. Recommended Visible and Near-Infrared Bands (Minimum) for the Baseline SeaWiFS Instrument. Phenomenon Chlorophyll Absorption Pigment Absorption Sediment/ Hinge Point Atmospheric Aerosols Atmospheric Aerosols Used with the 565 nm band for determining color boundaries, chlorophyll concentration, and diffuse attenuation coef- ficient (k). Used with the 565 nm band for mapping color and chlorophyll concentration in coastal waters. Used as a hinge point for determining chlorophyll, pigments, water optical properties (k), and measuring suspended sediments. Used to correct above bands for atmospheric effects. This band is not the best for aerosols since total radiance at the sensor is not zero in coastal waters, but it is compatible with CZCS processing techniques. Used to correct first three bands for the atmosphere. Better than 665 nm, if the sensitivity of the band is set to monitor aerosols and not land/water boundaries. NOTE: The band centered at 765 nm actually consists of two bands, 745 to 759 nm and 770 to 785 nm, illuminating a single detector, but blocked to avoid interference by oxygen absorption near 765 nm. 405 nm Band. A number of panel members proceeding to lower wavelengths accentuates suggested including a band at 405 nm for the the difference between gelbstoffe and chlorophyll primary purpose of observing the strong blue ab- concentrations. It is impossible to determine sorption by gelbstoffe.4 sorption by chlorophyll is near 435 nm and Since the maximum ab- when gelbstoffe absorption is affecting pigment- concentration estimates with band-ratio tech- gelbstoffe absorption increases almost exponen- niques using the CZCS suite of bands. A 405 nm tially with decreasing wavelength in this region, band would provide this information, at least at aes low pigment concentrations where reflectance at “tis important to note that gelbstoffe (yellow substance or 405 nm is still measurable. blue absorbing matter) is not synonomous with what is com- However, good atmospheric correction for monly referred to in the literature as dissolved organic matter this band will be critical for use of the data and (DOM). Gelbstoffe is a variable, generally small, component of the total DOM that is strongly absorbing in the violet and will be very difficult to achieve. In addition, de- blue and is comprised, classically, of highly stable humic and tector performance in this region is poor, and the fulvic acids from terrestrial plant decomposition found in riv- sensor's signal-to-noise ratio (SNR) performance ers and swamps. On occasion, decomposing phytoplankton is likely to be significantly lower in this band than blooms also produce optically similar compounds. The DOM in other bands. Also, polarization sensitivity would released extracellularly from plankton (considered by some to be a major pathway of carbon cycling in the ocean) gen- be worst in this band. For these reasons, the erally shows little absorbance in the visible. Hence, the 405 concensus of the panels was to select a different nm band cannot be used to estimate DOM. region for the sixth band. 39 36 490 and 520 Bands. Moving the 500 nm band to 490 nm and including a 520 nm band was suggested since these bands would permit multiband spectral-curvature algorithms and re- lated second-derivative algorithms to be applied to derive chlorophyll pigment concentrations in coastal (Case-2) waters. These types of algo- rithms, and, in particular, one using a combination of 460, 490, and 520 nm bands, discovered em- pirically by Grew (1981), have been shown to be relatively insensitive to the effects of nonchloro- phyll absorption and scattering. Comparisons of the results obtained from applying curvature al- gorithms to remotely sensed data with similar re- sults obtained from laser-stimulated chlorophyll fluorescence data routinely yield correlation co- efficients greater than 0.9 (Hoge and Swift 1986). Hoge and Swift's analysis also showed that al- though the CZCS band set precluded application of the Grew relationship, a combination of 443, 490, and 520 nm bands was equally effective. Another reason presented for including a 520 nm band was that its use would benefit from the CZCS heritage and, like the 665 nm band, would permit better comparisons to be made be- tween CZCS and SeaWiFS observations. This could be especially important in waters with high pigment concentrations, where the values from nearly 8 years of CZCS observation have been derived using a 520/550 nm band ratio. Unless this heritage is available, it will be extremely diffi- cult to assess the validity of any long-term trends observed between CZCS and SeaWiFS data if their derivations differ. Where this is likely to be most troublesome is in detecting changes in com- munity structure based on pigment groups, since the 520 and 500 nm bands lie near the peak of the complex, multicomponent accessory pigment absorbance region. Changes in accessory pig- ment composition and concentration are common when the phytoplankton community's structure changes in response to nutrient stress, eutrophi- cation, or other environmental changes. The proposed change from 550 to 565 nm will also af- fect this comparison, but to a lesser degree, since these two wavelengths are both near the mini- mum of chlorophyll pigment absorption. The combination of 443, 490, and 520 nm was considered, but was found to be infeasible from an instrument-design point of view. This is be- cause the dichroic beamsplitters used to reflect the shorter wavelengths and to pass the longer wavelengths do not have the ability to precisely cleave the spectrum. To avoid polarization ef- fects near adjoining spectral regions of band pairs, there must be a minimum of 20 nm between the upper wavelength of one band and the lower wavelength of the adjacent band (in this case 500 nm and 510 nm).° The concensus was that the 443, 500, and 565 nm bands of the baseline selection would accomplish the same purposes as the 443, 490, and 520 nm set. 565 and 570 nm Bands. Inclusion of a band at 570 nm in conjunction with the band at 565 nm was discussed because of the recent work of Hoge and Swift (submitted to Applied Op- tics). In this work they obtained extremely strong relationships between their laser-stimulated fluo- rescence concentration and results obtained from using a 566/571 nm band ratio on data from Case-2 waters. Correlation coefficients obtained using this band ratio exceeded those obtained using 443/550 nm and 520/550 nm band ratios when applied to data taken in four flight experi- ments. The choice of two closely spaced bands is attractive in that it lessens the need for highly accurate Angstrom exponent extrapolations. It also minimizes errors due to strong vertical inho- mogeneity, since the penetration depth for the two wavelengths is so similar. The narrow separ- ation of these bands would be possible in the SeaWiFS design, in contrast to the CZCS, OCI, or MODIS sensors, since individual detector filters are used for the detectors in band pairs. However, selection of 570 nm as the location of the additional band was rejected in favor of the substantial advantages to be gained in the accu- racy of atmospheric-correction algorithms through inclusion of a band at 865 nm. 5 Upper wavelength of the 490 nm band = 490 + 10 = 500 nm. Lower wavelength of the 520 nm band = 520 - 10 nm =o 0%nin 865 nm Band for Atmospheric- Correction Algorithms. In the currently used atmospheric-correction algorithms, it is necessary to assume that the ratio of aerosol radiance at two wavelengths is independent of position (except over waters where the chlorophyll con- centration is less than 0.25 ug/l). However, spa- tial variations in the type of aerosol will induce spatial variations in the aerosol radiance ratio. If there were a band at 865 nm (where there will be virtually no radiance at the sensor) in addition to the band at 765 nm, variations in the aerosol ra- diance ratio could be detected by checking for spatial variations in the aerosol radiance ratios from the 665 and 765 nm bands and from the 665 and 865 nm bands. The addition of the 865 nm band would also improve atmospheric cor- rection in coastal waters where the total radi- ance at the sensor from the 665 nm band is not Zero. Since atmospheric correction is so vital to the accuracy of pigment-concentration estimates, this band was selected as the sixth VNIR band for the SeaWiFS instrument. Bands in the Mid- and Long-Wavelength Infrared To remain within cost and weight constraints, the SeaWiFS design can support only two bands in the mid- or long-wavelength regions. Since pairs of bands in either region are required for sea-surface temperature algorithms, the discus- sion focused on a pair of bands in the 3.5 to 4.0 um region or a pair of bands in the 10.5 to 12.5 um region. A pair of bands in the long- wavelength region would provide continuity with the substantial use of AVHRR data from this re- gion, separately and in conjunction with CZCS data, and would provide these data from the same platform. On the other hand, a pair of bands in the mid-wavelength region would pro- vide a capability for determining sea-surface tem- peratures between +30° latitudes where the long-wavelength data is inadequate and would SYNTHESIS OF REQUIREMENTS improve the accuracy of the measurements since transmission in this region is greater than in the long-wavelength infrared. The panel members supporting the mid-wavelength posi- tion assume that AVHRR data will continue to be made available for measurements in the 10.5 to 12.5 um region. Additional rationale for both lo- cations is presented below. The Commercial and Operational Users Pan- el recommended the long-wavelength bands based on their need to make continued use of the algorithms now used to interpret the data from the NOAA AVHRR sensors. The Research Panel members pointed out that AVHRR-derived estimates of sea-surface temperature in con- junction with CZCS-derived estimates of pigment concentration have been useful in several stud- ies of mesoscale processes (e.g., Brown et al. 1985 and Abbott and Zion 1985). However, since the CZCS and AVHRR measurements are not simultaneous, constraints are imposed on certain studies due to the movement of clouds and other ocean features between the satellites’ overpasses. Also, scientists must access two separate data archives. Since sea-surface tem- perature can be used as an indicator of physical processes, simultaneous measurements might improve estimates of productivity. Finally, simul- taneously acquired information on sea-surface temperature and the diffuse attenuation coeffi- cient (closely related to the pigment concentra- tion) may be useful in studying mixed-layer dy- namics and surface-transport mechanisms. The Research Panel members recognized the value of acquiring sea-surface temperature data in the tropical latitudes, but pointed out that, to obtain precise estimates, these measurements would have to be made in the nighttime segment of each orbit. This is because daylight-segment sea-surface data in the mid-wavelength region would need to be corrected for the atmospheric backscatter of the solar mid-infrared by aero- sols, and this correction would be difficult to 37 38 achieve. Furthermore, the instrument would al- ways be undergoing a tilt change somewhere in these latitudes, so daytime sea-surface tempera- ture measurements would be sporadic at the lati- tudes where the capability was desired. Since, as discussed in Section 5, the Landsat-6 nighttime power capacity is limited and nighttime data would be separated by 12 hours from data acquired in the visible regions, the Re- search Panel also favored locating the infrared bands in the 10.5 to 12.5 um region, preserving the continuity with prior AVHRR-based work. As a result, the baseline SeaWiFS instrument design contains the split long-wavelength band set. Band Selection Summary The spectral regions and band characteris- tics agreed upon for the baseline SeaWiFS instru- ment are summarized in Table 3. The SNR per- formance goals for the VNIR bands are chosen so that the error induced by the noise on the sig- nal approximately equals the error inherent in the atmospheric correction algorithms. These values represent minimum acceptable performance. The noise-equivalent temperature differences (NEATs) of Table 3 are sufficient to determine sea-surface temperatures in cloud-free areas to a few tenths of a Kelvin. An accuracy of 0.1K is the anticipated requirement for the 1990s; how- ever, the resulting NEAT requirement of a few hundredths of a Kelvin would exceed the capa- bility of the SeaWiFS instrument. Considering that the NEAT performance of the CZCS at 300K was 0.29K, the goal for the SeaWiFS was taken as a NEAT of less than 0.29K at 300K. Spatial Resolution As discussed in Section 5, the Landsat orbital altitude of 705 km, in conjunction with the deci- sion to use the AVHRR High-Resolution Picture Transmission (HRPT) data format of six frames per second, fixes the sensor's spatial resolution at 1.13 km at nadir. Both panels agreed that this resolution would be adequate for their local-area Table 3. SeaWiFS Baseline Spectral Regions and Performance Goals Spectral Region Range Visible Visible Visible Visible Near IR Near IR IR IR 433-453 490-510 559-575: 1 655-675 n 745-785 n 843-887 n 1 2 3 4 5 6 iG 8 Spectral mM mM mM mM mM mM 10.5-11.5 um 11.5-12.5 um Expected Signal Radiance Minimum (mW/cm2 -sr-um) ! SNR/NEAT! 1H. R. Gordon 1987: personal communication. The SNR values must be met at all sun angles. Notched between 760 and 770 to minimize interference from the 3 oxygen absorption band. At 300K. coverage uses, but also requested that the data be aggregated on board to provide global-area coverage at approximately 4.5 km resolution. The rationale for these requirements can be sum- marized as follows. The distribution of chlorophyll in the ocean is patchy on all scales down to less than a kilome- ter. To adequately map the variation in phyto- plankton concentration in high-concentration shelf areas (a major goal of the first of the MAR- EX studies), a sensor must be able to resolve about a kilometer of the ocean. This small foot- print size also allows measurements to be made close to the shore, permitting resolution of local outwelling and upwelling zones, which tend to be near-shore phenomena. The high data rate that will result from such a spatial resolution may be reduced somewhat for wide-area studies of open-ocean phytoplankton concentration, where statistical rather than process experiments are of more interest. For the latter case, a 4.5-km reso- lution is acceptable. Therefore, a system is re- quired that generates, stores, and transmits both resolutions of data. This type of data-processing system is analogous to the NOAA/AVHRR system, which has been used as a basis for defining the proposed SeaWiFS data products. The conversion of the higher resolution (1.13 km) data to a global (4.5 km) data set should take place in the on-board data processing system prior to recording or transmitting the data. The algorithm for this conversion will be determined at a later date; however, the consensus was that averaging the 16 1.13-km pixels is not desirable and that selecting the output of a single cloud- free pixel to represent a 4.5-km area would be a better solution. Radiometric Accuracy and Relative Precision The scientific and operational utility of an ocean-color imaging system depends completely on the ability to measure radiance at the instru- ment's aperture with sufficient accuracy and res- olution to separate and remove from each meas- SYNTHESIS OF REQUIREMENTS urement the contributions from the atmosphere and, thus, to infer the amount of water-leaving ra- diance within, essentially, the limits in accuracy of the atmospheric-correction models. On this ba- sis, a radiometric accuracy of approximately 5% is required in each band, and the relative preci- sion between individual measurements within each band must be much less than 1%. The em- phasis in the expression of these requirements is on the importance of relative precision between measurements in a given image or band and be- tween images on different days when a given po- sition on the surface is viewed at different scan and solar angles. On small spatial scales, pixel-to-pixel varia- tions in aerosol radiance are typically of the same order of magnitude as variations in the amount of water-leaving radiance. Under hazy conditions, the fluctuation in the amplitudes of aerosol radi- ance may be 4 to 10 times larger than the varia- tions in water-leaving radiance associated with ocean fronts of similar spatial scales. As a result, the algorithms used to remove the aerosol effects require precision between bands to within 1%. Even limited atmospheric correction algorithms, sufficient to locate front and eddy boundaries, re- quire removal of these atmospheric effects, and all quantitative applications require good radio- metric accuracy and extremely good relative pre- cision. Polarization sensitivity and the constancy of the solid-angle field of view of the radiometer are two major factors affecting relative radiometric precision. Polarization Sensitivity Polarization sensitivity is defined as the ratio of the difference between maximum and minimum output to the sum of the maximum and minimum output obtained when the plane of incoming lin- early polarized radiation is rotated through 180°. Normally, a radiometer is calibrated using un- polarized input radiance. Under these circum- stances, if the radiometer's response is polariza- tion sensitive (usually because of internal reflect- 39 40 ing surfaces), its calibration is valid only for scenes characterized by unpolarized radiance. However, in the ocean-atmosphere system, the largest signal contributor (and largest signal vari- ation) is Rayleigh scattering radiance, which is very strongly polarized. Moreover, the polariza- tion varies greatly across the range of relevant scan angles. Since the instrument's error due to polarization sensitivity may also vary with scan angle, the problem is compounded. These errors would be very difficult to correct, even using completely polarized radiative-transfer models. While the problem might be possible to solve at a satisfactory level of accuracy, the expense and uncertainty are far greater than would be the case with an instrument designed with a low pola- rization sensitivity. The CZCS specification was 2%, and this level of polarization sensitivity was deemed satisfactory. Solid Angle Resolution of IFOVs If a radiometer were designed with an optics train that varied the solid angle subtense of the instrument's field of view, e.g., to correct for foot- print distortion, that variation could lead to a loss of relative precision in the cross-scan direction or between tilt configurations. If the instrument's optical configuration is modified to vary the angu- lar IFOV for any reason, then the calibration of each distinct angular resolution configuration be- comes essentially independent. Aside from the complexity inherent in calibrating such a system, the loss of relative precision would cause the er- rors in achievable atmospheric corrections to reach totally unacceptable levels for any quantit- ative use of the data. In addition to these unten- able results, a variable-resolution design would be extremely difficult to monitor for degradation of the overall radiometric sensitivity. These effects can be avoided only if the instru- ment is designed in such a way that the product of the detector's solid angle and the area of the final optics aperture (or the area of the detector and the final optics solid angle) are constant for all instrument fields of view. Dynamic Range Both panels emphasized that the dynamic range of the SeaWiFS instrument must be such that subtle variations in reflectance and tempera- ture in open-ocean scenes of interest can be de- tected as well as major variations in scenes with high entropy, such as coastal waters. Within a fixed number of available quantizing bits these two requirements might conflict. Therefore, on- board adjustment of dynamic range is desirable. Possible solutions include programmable gain changes and nonlinear encoding. Careful con- sideration must also be given to the quantization of the points of the on-board calibration curve (i.e., from space and on-board calibration tar- get(s)). It is anticipated that 10 bits of digitization should provide sufficient range for detection of the radiance from typical open-ocean scenes. However, additional studies should be conducted to firmly establish the required range and to de- termine whether gain changes, additional bits, and/or nonlinear digitization are desirable. Ad- justable gain could also be used to enhance the signal at the reduced light levels occurring near the twilight portion of the orbit and to reduce the signal when employing the diffuser plate for in- flight instrument calibration. Bright Target Saturation The CZCS instrument experienced saturation- induced errors immediately after scanning over bright clouds or land. Following saturation, the data became unusable for distances up to 100 km, depending on the brightness of the clouds and their spatial extent. The SeaWiFS design should incorporate protective circuitry to minimize or, if possible, eliminate this type of instrument arti- fact. Locational Accuracy The location of data from all pixels in latitude- longitude coordinates is important for quantitative, scientific use of ocean-color imagery. In order to make these data useful, scientists must be able to utilize Observations from many passes to gener- ate time series and to do statistical analyses. This implies that the locational accuracy of data from different passes must be sufficiently precise to al- low compositing. For these purposes, an abso- lute navigational accuracy of 1 km for high- resolution data and 5 km for low-resolution global data are required. Maximum Scan Angle and Revisit Interval The topic of revisit interval engendered much discussion during the workshop. In fact, having a daily revisit interval emerged as the sine qua non for most commercial and operational users. The baseline SeaWiFS instrument design presented during the initial workshop had a +45° scan an- gle, resulting in a scan swath of 1500 km and a 2- day revisit interval. This design was selected based on the understanding that data from scan angles greater than about +30° could not be in- terpreted quantitatively. However, as demon- strated in Section 2, commercial and operational users find great qualitative value in imagery ac- quired at scan angles in excess of 40°. With the Landsat-6 orbit, a scan angle of +58.3° would be required to provide a daily revisit interval (2800 km swath), and this angle can be accommodated in the instrument design without difficulty. (This scan angle will give complete coverage at the equator with increasing overlap at higher and lower latitudes.) The positions of both panels on this issue and its resolution are presented below. Commercial and Operational Users' Requirements for a Daily Revisit Interval A daily revisit cycle was strongly recommend- ed by commercial and operational users since the temporal variability of ocean-color and tempera- ture features are of prime interest to them. A knowledge of the daily changes in these features is critical in understanding water-mass move- ments and in observing the movements of ocean- circulation features. For example, the movements of waves along the north wall of the Gulf Stream change significantly within a 1-day period. In ad- SYNTHESIS OF REQUIREMENTS dition, navigating ship movements for research station locations, positioning frontal boundaries for naval operations, and locating fish populations all require a daily revisit interval. This revisit-interval requirement is based on experience. Usually cloud cover hampers rou- tine coverage of areas of interest. With a revisit interval of every other day, if clouds hamper the image for 1 day (as is often the case in tropical or subtropical regions during Summer and in polar regions during winter), then no imagery is ob- tained for a period of 4 days. This is not ade- quate, since many ocean frontal boundaries are moving too rapidly to be able to infer the temporal variability from data that differs by 4 days. Ex- perience has also shown that the image- processing technique of "movie looping" succes- sive images for flow visualization requires at least one image a day in frontal regions in order for the human eye to interpolate or see and understand the motions of the ocean features. Circulation patterns are readily discernable in movie loops using twice-daily AVHRR images. Once-daily im- ages provide poor, but usable, results; however, circulation patterns are not recognizable with every-other-day coverage. An important and attractive use of the Sea- WIFS data will be in gaining an understanding of the temporal variability of the ocean surface. If the data are undersampled in time so that the dai- ly scales, or bidaily scales, of variability are not obtained, the utility of the sensor for any type of near-real-time commercial or operational applica- tion would be greatly limited. Research Users' Requirements for Revisit Interval Research requirements for world-wide chlo- rophyll observations dictate global measurements at least once every 3 or 4 days. However, be- cause imagery is lost due to cloud cover and sun glint, this requirement results in a need for global coverage on a 1- or 2-day cycle. Currently, algorithms for correcting ocean- color data for the effects of atmospheric degra- dation are viable to a scan angle of approximately 41 42 30°, and qualitative observations of color fea- tures are possible at larger angles, depending on atmospheric conditions. In a like manner, the ac- curacy of sea-surface temperature measure- ments decreases as the amount of water-vapor absorption increases due to slant path viewing. Therefore, the scientific community was satisfied with 2-day coverage (45° scan). However, since the commercial and operational users needed daily coverage and since providing daily revisit would not interfere with use of the data for re- search purposes, the Research Panel agreed that daily coverage should be a baseline Sea- WIFS requirement. Scan Plane Tilt Over the oceans, the data from a nadir view is contaminated by specular reflections from the oceans’ surface (sun glint). In order to minimize this effect, the field of view must be pointable on command along track to 20° on either side of na- dir, in addition to nadir (0°). Rapid slewing along track is desirable to minimize the loss of data. Calibration The research users expressed the absolute radiometric calibration accuracy goals for the SeaWiFS instrument as follows: When the instru- ment receives radiance levels from zero to the maximum level at its entrance aperture from a traceable (National Bureau of Standards) source, the output will be convertible to a value that is within 2% of the maximum radiance from the source for all reflectance bands. The desire for a lunar view to monitor the instrument's stability was also expressed. For the thermal-emittance bands, a calibrated blackbody "standard" source should be used. The measurements in the thermal-emittance bands should give values that are within 1% of the maximum radiance from the source value, which should range from zero to the maximum level. Thermal calibration requires a minimum of two points, with three being desirable. A deep- space view serves as a zero-radiance reference, and two blackbodies, emitting at appropriate tem- peratures in the thermal range of the sensor, pro- vide the other two points. It is recommended that every effort be made to include two black- body sources in SeaWiFS. System Requirements Data Processing, Downlinks and Formats, and Dissemination Commercial and Operational Users' Requirements The spatial resolution, revisit interval, and ac- cess time recommended by the Commercial and Operational Users' Panel is summarized in Table 4. These requirements are based on the panel members’ knowledge of the data products deliv- ered from the CZCS and the AVHRR. The Navy has established the Navy and Ma- rine Corps Specific Data Requirements for Atmo- spheric-Environmental Data Measurements from Satellites. Recently an ad hoc committee of the Navy Space Oceanography Science Working Group reevaluated this list to recommend new scientific research and development programs and projects that should be carried out over the next decade in order to ensure proper utilization of forthcoming satellite resources by the Navy (Mitchell 1987). Of these requirements, those that might be addressed by the SeaWiFS sensor or next-generation instruments are included in Table 4. As indicated in Table 4, most commercial and operational users need to receive data once a day within 24 hours or less of the time of acquisi- tion, and some applications require daily, real-time reception. Two major user groups for commer- cial and operational applications can be identi- fied, and the data downlinks required differ for each. The first and largest group consists of mer- chant, fishing, and naval fleets who require a di- rect, daily downlink of data on local conditions. Currently, the worldwide merchant fleet compris- es over 25,400 ships over 1000 gross tons, and there are 11,800 oceangoing fishing vessels. On the order of 400 naval vessels are types that would be useful to equip for reception of these data. The second user group represents the SYNTHESIS OF REQUIREMENTS Table 4. Commercial and Operational Users' Recommended Spatial Resolution, Revisit Interval and Data Access Time. Resolution Satellite Data Weeden ais (Nominal Revisit Access Discipline and Application at Nadir) Interval Time (km) (hr) (hr) Fishing Industry Fish Location Currents Visibility Fisheries Research Development of Applications 24 Monitoring Larval Transport 24 Habitat Studies N/A Monitoring Unusual Environmental Events 24 max Pollution Detection/Monitoring 24 max Research and Development 24 max Offshore Oil and Gas Industry Currents 24 max Fronts/Eddies 24 max Ice-Edge Location 24 max Sediment 12-24 Pollution Detection/Monitoring 12 max Research and Development N/A Marine Transportation Industry* Currents 24 max Fronts/Eddies 12-24 Ice-Edge Location 12-24 Visibility Vers! U.S. Navy** Sea Ice Cover 12 Sea-Surface Temperature Syil2 Turbidity (Differential Attenuation Coefficient) 0.25/83 Bioluminescence 6/12 Ocean Color (Chlorophyl 6/12 Atmospheric Visibility (Aerosols)*** 10 0.25 Littoral Sediment Transport*** 10m 0.5/3 Shallow Water Bathymetry*** 10/300m 0.25/24 To improve centralized ship routing, SeaWiFS data covering all areas where these services are provided will be required. Daily global data at a resolution of 4.5 km will satisfy this requirement. Data of this resolution will enable routing services to improve their strategic advisories to take advantage of ocean currents and eddies. However, vessels at sea will require higher resolution data in real time to tactically position their vessels to take full advantage of these currents. If there are two parameters in the columns, the first is for a 4200 x 4200 km coverage, and the second is for global coverage. In conjunction with other sensors. 44 value-added industry, some elements of the off- shore oil and gas industry, and the Navy who would use a central-processing facility to prepro- cess global data prior to distribution. The market comprising the commercial mari- time fleet, for the most part, can be captured only if the data can be acquired daily in near real time, the price of the receiving equipment is modest, and its size relatively small. This implies direct re- ception by a nondirectional antenna. However, the value of such data to these users is great enough to justify a monthly subscription fee of $1000 to $2000. If all of these conditions cannot be met, there will be much less interest in the data on the part of these users. Regarding reception by naval ships, the po- tential exists for SeaWiFS data to be received by existing naval systems that are capable of han- dling environmental data from satellites. Although these systems are not designed to handle Sea- WiFS-type data or products derived from this sen- sor, it is important to consider that these systems represent a naval asset that can and will utilize SeaWiFS data, if the Navy's requirements for ocean-color and sea-surface data can be satis- fied. The attractiveness of SeaWiFS data to the Navy will be judged partially on the degree of compatibility in reception and data format with their existing systems. In this context, the Tactical Environmental Support System (TESS) is a major Navy system that might be a candidate for pro- cessing SeaWiFS data. The system's specifica- tions have been documented by the Space and Naval Warfare Systems Command (1986). Also, by 1990 the Navy will have installed meteorologi- cal data receiver-recorder sets (AN/SMQ-11) on ships and at regional sites. For naval use, it is im- portant for the SeaWiFS data to be available in a real-time direct-readout mode as well as being re- ceivable (compatible frequency and format) by the AN/SMQ-11. The second user group requires a stored- data downlink, since members of this group serve customers whose platforms are located through- out the world or implement operational applica- tions whose regions of interest are worldwide. For most of these potential users it will be logisti- cally and economically infeasible to establish and maintain receiving facilities at one or more loca- tions. Hence, direct access to the data base in a central facility is needed. These users also re- quire daily data acquisition and access to the data within 24 hours of its collection. The need for data in near real time, docu- mented in Table 4, is perhaps the most stringent commercial- and operational-user requirement. Since most users will be unable to supply their own satellite receiving station, central ground stations for users to access data is desired. User access to sequentially stored local area cover- age (LAC) and global area coverage (GAC) data (i.e., last 48 hours of data) for review is useful in some applications, including forecasting models.° A real-time browse capability with the ability to capture some of the data is also needed. Although digital and analog imagery are po- tential real- or near-real-time SeaWiFS data prod- ucts, the commercial and operational user is most interested in receiving full-resolution, 10-bit, digi- tal data, including ephemeris and calibration data. Data products in a digital format will permit the user to preprocess the data, correcting for atmo- spheric effects, prior to use. It appears there is very little demand for lesser quality analog data products. 6 For the SeaWiFS, LAC data will be at a spatial resolution of 1.13 km, GAC data will be at a spatial resolution of 4.5 km. Research Users' Requirements Satisfactory data processing and delivery is of the highest priority to the success of the SeaWiFS mission. Data processing and delivery for re- search users should meet the following require- ments: @ Global coverage at 4.5 km resolution with a 2- day revisit cycle ® Quick-look data products for selected areas within 12 hours of collection for near-real- time use in positioning of research vessels ©@ Level-1 imagery available in 7 days. Level-2 imagery for both high- and low-resolution data, available to the user within 10 days of observation.’ Crossing Time Landsats 1 through 5 have been maintained in a sun-synchronous, 705-km orbit with a 9:30 a.m. equatorial crossing time, principally because the main function of their sensors is to observe land masses. However, the observation of ocean color depends critically on having sunlight pene- trate into the water where it is absorbed and backscattered into the sensor. For this reason, ideally, observations should be as near noon (solar zenith = 0°) as possible, but the research community agrees that there will be adequate wa- ter penetration by sunlight and that viable atmo- spheric correction will be possible if the equatorial crossing time is no earlier than 10:30 a.m. and no later than 1:30 p.m. This implies that the Landsat- 6 crossing time be moved from its current 9:30 a.m. baseline to at least 10:30 a.m.® Duty Cycle The SeaWiFS instrument is designed to pro- vide world coverage of the ocean basins, and 7 Level-1 imagery is raw data in a reformatted structure with calibration and navigation information within the header. Level-2 imagery is geophysical data, not gridded nor resam- pled. SYNTHESIS OF REQUIREMENTS many commercial, operational, and research ap- plications will require data from the Mediterrane- an Sea, Central Atlantic, Pacific, and Indian oceans and regions in the Arctic and Antarctic. Selected regions will probably be routinely cov- ered according to schedule while other regions will be viewed on an ad hoc basis. A 100% duty cycle would be ideal, since sea-surface tempera- ture data could be acquired during nighttime, giving a swath of visible and infrared imagery during the day and a swath of infrared data at night. However, it is recognized that satellite power restrictions may not permit a full duty cy- cle. The capability of the satellite in this regard is discussed in Section 5. Mission Life In order to conduct the in-situ field work ne- cessary to exploit the research value of ocean- color observations from space, experiments must be staged in a variety of seasons and conditions. Logistically, the spacecraft mission must last at least 3 years to encompass typical events, e.g., the occurrence of the El Nifo phenomenon. In addition, even the coarsest values for ranges in interannual productivity are not known for most ocean areas. Hence, a minimum of 3 years is necessary to identify its scale of variability. The nominal lifetime of Landsat-6 is 5 years, and this extension in time is highly desirable. In this re- gard, the instrument's calibration must be con- stant or identifiable during the mission to allow valid comparisons of ocean values observed at different times. Requirements Summary Table 5 summarizes the goals for the Sea- WiFS system set forth by the SeaWiFS Working Group. 8 this accords with the recommendations of the Geology and Evapotranspiration/Botany panels of the Thermal Infrared Working Group (Putnam 1986) that the equatorial crossing time of Landsat-6 be as close as possible to noon without ex- cessive loss of imagery due to cloud cover, i.e., about 10:30 am 45 46 Table 5. Users' Baseline Goals for the SeaWiFS System. Band 3 Minimum Bandwidth SNR/NEAT Spectral Bands 1 433 - 453 nm 510 2 490 - 510 nm 500 3 599 - S/o'nm 350 4 655 - 675 nm, 285 ‘ 745 - 785 nm 280 6 843 - 887 nm 280 i 10.5 - 11.5 wm 0.29K (at 300K) 8 Ml ou= 1225 q0im 0.29K (at 300K) Spatial Resolution 1.13 km Radiometric Accuracy: 5%, each band Relative Precision < 1% Between-Band Precision < 1% Polarization Sensitivity < 2% (worst case) Dynamic Range 10 bits quantization (gain adjustable on board) Bright Target Recovery 10 samples or less Locational Accuracy 1 km absolute, high-resolution data; 5 km absolute, low-resolution data Scan Plane Tilt + 20° Revisit Interval 1 day Repeat Coverage 16 days VNIR Absolute Radiometric Calibration Within 2% of maximum radiance from source (traceable to NBS standards) when receiving radiation from zero to the maximum level. TIR Absolute Radiometric Calibration Within 1% of maximum radiance from each of two blackbody sources when receiving radiation from zero to the maximum level, a space view serving as a zero-radiance reference. Data Access Direct reception of local area coverage in near real time and direct access to global data base within 24 hours of collection. Data Product Delivery Seven days, Level-1 imagery, 10 days, Level-2 high- and low-resolution imagery. 10:30 a.m. (between 10:30 a.m. and 1:30 p.m., acceptable). Crossing Time Mission Life Three years or more. 1 Blocked from 760 - 770 nm 3 IMPLEMENTATION PANEL REPORT Panel Chairman: Aram M. Mika Contributors: Bill Barnes William Bishop Kendall Carder Dennis Clark Wayne Esaias Robert Evans Gene Feldman David Fischel Leon Goldshlak Howard Gordon Ken Hubbard Matthew Jurotich Bob Kirk George Martch Ed Mowle James Mueller Kenneth Ruggles Joseph Schulman Richard Stumpf Charles Vermillion Loren Woody Implementation Panel Charter and Objectives The purpose of the Implementation Panel was to translate the mission objectives of the commercial, op- erational, and research users into a workable system concept that would provide the data required to meet the users' needs. The work of this panel supported the other panels by defining the technical tradeoffs among the performance parameters (e.g., radiometric sensitivity versus spectral bandwidth) and by identify- ing the practical consequences of various options in terms of cost and complexity. Thus, the Implementa- tion Panel established a feasibility envelope for the Working Group, leading to a system concept that was not only useful from the users’ perspective, but also technically and economically realizable. In essence, the role of the Implementation Panel was to pass the desires of the two user panels through the dual filters of physical and fiscal reality to arrive at a practical system concept meeting their needs. This process is illustrated in Figure 18, and the panel's charter is summarized below. Figure 18. Interactive process leads to a workable system concept. NEGOTIATION SCIENCE/ SCIENCE/ RESEARCH USERS RESEARCH USERS DESIRES NEEDS FEASIBILITY INITIAL ASSESSMENT FINAL SYSTEM SYSTEM CONCEPT COST/PERFORMANCE CONCEPT TRADEOFFS OPERATIONAL USERS USERS DESIRES NEEDS NEGOTIATION OPERATIONAL 47 48 implementation Panel Charter ® Develop a complete system concept meeting user requirements. ® Establish system feasibility. ® Negotiate with user groups to arrive at a base- line system concept. ® Quantify the performance of the baseline sys- tem. The end-to-end definition of a spaceborne remote sensing system encompasses a wide va- riety of topics including: ® Sensor Definition - What type of instrument is required to perform these missions, and what are its specific design and performance char- acteristics? © Spacecraft Integration - How will this sensor be accommodated on the spacecraft in terms of its mass, power, and viewing requirements? On-board Data Handling - How will the data stream from the instrument be processed and stored on the spacecraft? ® Data Downlink Formatting - How will the sen- sor's data be formatted, and what are the spe- cifics of the radio frequency channels for data transmission? Ground Reception and Processing - How and where will the downlinked data be received and processed? ® Data Product Definition - What are the specific end products to be derived from the data stream, and how will they be formatted? ® Data Access and Distribution - How and how soon after reception can the data be accessed and how and in what form will the data proa- ucts be distributed? Algorithm Development - What software tools are required to produce useful output data products from the raw data? Who will develop these tools, and how will these tools be made available to users? These and other issues were addressed by the Implementation Panel during the working sessions in February and April 1987. The results are discussed in some detail in the balance of this section. Sensor Definition Design Tradeoffs Usually a sensor concept is developed by performing tradeoffs among instrument perfor- mance characteristics, e.g., spatial, spectral, tem- poral, and radiometric resolution. However, in evolving the SeaWiFS design concept, many of the degrees of freedom normally available have already been constrained by spacecraft and data-format considerations. In addition, the high level of performance required of the sensor re- stricts the remaining design options. First of all, the resources of the Landsat-6 spacecraft must be assumed to be principally dedicated to supporting the Enhanced Thematic Mapper (ETM) mission. Hence, the SeaWiFS in- strument must be lightweight and require little power. Also, the current launch schedule for Landsat-6 (4th quarter of 1990) limits the Sea- WiFS sensor design and fabrication efforts to an activity of about 20 to 24 months. This latter con- straint leads to the requirement for an uncompli- cated, proven-technology concept. Secondly, to minimize ground station requirements for users of SeaWiFS data, the SeaWiFS data product should be compatible with the AVHRR High-Resolution Picture Transmission (HRPT) format, for which there are many existing ground stations. Since HRPT is formatted into six frames of data per second, the best choice of line rate for SeaWiFS is equal to this frame rate. At an orbital altitude of 705 km, this immediately defines the sensor ground sampling distance (GSD). That is, the satellite's orbital velocity moves it 1.13 km over the ground in 1/6 second; therefore, suc- cessive scan lines will be 1.13 km apart on the ground at nadir. Since data-processing require- ments are eased when data are sampled in a square grid (equal angular sample spacing along the scan and the track directions), the sample spacing along track is also taken to be 1.13 km at nadir. This results in a nominal square instan- taneous field of view (IFOV) of 1.6 mrad. The requirement for a proven-technology approach leads to a choice of moderately sized detectors, particularly for the thermal-infrared (TIR) region. Existing instruments, such as the VAS/VISSR, and detectors developed for several Santa Barbara Research Center IR&D programs use long-wavelength infrared (LWIR) HgCdTe detectors in sizes ranging from 100 to 125 um. Hence, the initial detector size selected was 100 um. However, in optimizing the optics and mechanical-packaging design, a 20% increase in the nominal detector size was required, resulting in 122 um detectors. This fixes the optical focal length at 7.64 cm (for an IFOV of 1.6 mrad). The very low reflectivity of the ocean creates a requirement for high signal-to-noise perfor- mance in the visible and near-infrared (VNIR) re- gion that drives the design towards concepts SAMPLE 1 CENTER SAMPLE 2 CENTER CENTER TRACE SAMPLE 3 CENTER A ateasge 6 a> ON = So =| NOS = x F [s) < c Ee So z ° a < WwW S) z < Ee 2 a . = 00 -500 0 500 DISTANCE ALONG SCAN, KM 1000 ee IMPLEMENTATION PANEL that use either long dwell times or time-delay in- tegration (TDI). The only practical method for re- alizing long dwell times is to reduce the required scan rate by using more than one detector per band along the track direction. For example, if there are two detectors along track rather than one, then the required scan rate for contiguous scan swaths would be three scans per second instead of the six scans per second required for one detector. Since the scan rate is halved, the detector dwell time and, therefore, the available signal integration time, is doubled. Unfortunately, the very wide scan angles of the SeaWiFS instru- ment cause severe bowtie distortion when multi- ple detectors are used along track, i.e., the off- axis angle and the Earth's curvature cause the spacings between sample centers along track to become larger and larger on the ground as the scan angle increases. This effect is shown in Figure 19. In order to avoid this geometric dis- tortion, the SeaWiFS design was constrained to using a single detector along track. 2.57 KM AT EDGE OF SCAN y Figure 19. Bowtie distor- tion from more than one detector per band along track and wide scan angle. 49 50 TILT MECHANISM Figure 20. Initial Sea- WiFS design. DEROTATOR DICHROIC BEAMSPLITTERS ASSEMBLY This constraint left TDI as the primary tech- nique for increasing the signal-to-noise ratio (SNR) performance of the VNIR bands. Initial performance estimates lead to a requirement for five detectors in TDI along scan, thereby provid- ing a square-root-of-five improvement in SNR. Since sensor complexity (and cost and risk) in- crease rapidly with the number of detectors in TDI in the TIR region, those bands had to be limit- ed to one detector per band. Based on these parameters, summarized in Table 6, several different sensor configurations were evaluated. The initial design concept, de- veloped as an input to the SeaWiFS Working Group, utilized a continuously rotating scanner Table 6. Scan Rate GSD IFOV Detector Size Optics Focal Length Number of Detectors SCAN MECHANISM VNIR AFT ASSEMBLIES SOLAR DIFFUSER - fete )\ |_— RADIATIVE COOLER }] | J, th x, vA (90 degree fold), followed by an afocal telescope and an image derotator, as shown in Figure 20. This design was compact, lightweight, high in per- formance, and low in risk (i.¢., low in complexity). However, a polarization analysis showed that the design had a polarization sensitivity on the order of 5%, principally due to the large angles of inci- dence of the k-mirror derotator. Since, as dis- cussed in Section 4, low polarization sensitivity is one of the key requirements of SeaWiFS, an alter- nate concept was pursued. The alternate con- cept entailed a design with as few reflections as possible, kept as close to normal incidence as possible. The resulting concept is described below. Initial SeaWiFS Design Parameters lines per second km mrad um cm per TIR band per VNIR band, TDI along scan Baseline SeaWiFS Design In the proposed baseline SeaWiFS design concept, shown in Figure 21, the telescope ro- tates 360° about a pivot axis to scan the scene, thereby avoiding the use of a scan mirror and its associated polarization effects. Also, the fold mir- rors used to direct the scene energy out of the IMPLEMENTATION PANEL telescope are located so as to minimize angles of incidence, and the half-angle mirror is placed in the plane perpendicular to the fold mirrors. This allows the polarization introduced by the half- angle mirror to be partially balanced by the fold mirrors’ contributions. The resulting polarization sensitivity is less than 1.4%, well within the Sea- WIFS requirement of 2%. Figure 21. Baseline SeaWiFS design. TILT MECHANISM VNIR AFT ASSEMBLY DICHROIC BEAMSPLITTERS AG Als< TIR AFT ASSEMBLY COOLER fh, BSN SCAN MECHANISM SCAN AXIS HALF-ANGLE MIRROR SOLAR DIFFUSER =x /j}\ TRACK (TIL RADIATIVE oN Ee mED 51 NADIR ey Figure 22. Sea- WiFS focal-plane assembly layouts. Specular sun reflection is avoided by tilting the telescope in the plane perpendicular to the scan plane (i.e., along track) to one of three posi- tions: +20°, 0°, or -20°. The continuous 360° scan allows reference sources to be viewed dur- ing the nonactive, or non-scene-viewing, part of the scan, as well as allowing a deep-space view for a zero reference just before the scan begins? There is also a solar diffuser that can be inserted into the field of view of the sensor for calibration against the input solar radiance. This concept has an active scan of 58.3°, providing a scan length of 2800 km (i.e., daily global coverage). After the scene energy leaves the 3X afocal telescope and fold mirrors, it is spectrally separat- ed into four beams. All separations are per- formed by dichroic beamsplitters to provide co- registration of the beams on the ground. The first dichroic splits the TIR (3 to 13 um) from the "The 360° scan would also permit calibration from a lunar view. However, provision of regular lunar radiance calibra- tion would require maneuvering the spacecraft. If deemed necessary, the occasions when a full moon happens to be within the field of view of the sensor could be calculated, and the sensor could be activated at these times. VNIR (0.4 to 1.0 um). The TIR travels straight through and is focused onto the detectors in the TIR aft assembly (consisting of focusing optics and two detectors). As mentioned above, one TIR detector per band minimizes the complexity of the instrument and allows a very simple radiative cooler to be used. The cooler envisioned, a standard prod- uct manufactured by Arthur D. Little Corp., pro- vides a detector operating temperature of about 110K. The TIR detectors are discrete photocon- ductive HgCdTe elements. These detectors and the layout of their spectral filters are shown in Figure 22. The design of the aft assembly en- ables either two LWIR bands (e.g., 10.5 to 11.5 um and 11.5 to 12.5 um), two mid-wavelength in- frared bands (e.g., 3.5 to 3.75 um and 3.75 to 4.0 um), or even one band from each region (e.g., 3.5 to 4.0 um and 10.5 to 12.5 um) to be accommodated. However, in accordance with the users’ agreement discussed in Section 4, the baseline design consists of the two LWIR bands. The VNIR light reflected from the first dichro- ic IS spectrally separated by the second dichroic into a short-wavelength VNIR beam and a beam containing the two longest wavelength VNIR bands. Assuming the baseline spectral bands agreed upon by the users’ panels and shown in Table 7, this split would occur between 675 nm and 745 nm (i.e., between bands 4 and 5). The VNIR bands are paired so that a minimum of dichroic splits and VNIR aft assemblies are need- ed; this requires two sets of five VNIR detectors (for TDI in each band) per aft assembly. Since this array of detectors extends along the scan di- rection, the field of view required of the optical system is 1.0° (11 IFOVs, as shown in the detec- tor layout in Figure 22). The remaining spectral split occurs between 510 nm and 555 nm (between bands 2 and 3). In each of the three VNIR aft assemblies, two VNIR bands are focused and detected. The VNIR detectors are photodi- ode/preamplifier hybrids. Since the hardware synchronization of the existing HRPT ground stations is fixed at 6 frames per second and 11,090 10-bit words per frame, the data frame structure shown in Table 8 was selected. This format provides the proper syn- chronization blocks for the hardware, while still transmitting all of the required data, and yields an effective data rate of 665 kbps. Sensor Performance Three key performance parameters were ex- amined: radiometric performance, modulation Table 7. ONOnAFEWNM— * *Blocked from 759 to 770 nm to minimize interference from the oxygen absorption band. transfer function (MTF), and polarization sensitivi- ty. For the radiometric performance estimates, the VNIR SNR was calculated, and the results are given in Table 9. For these SNRs, the sensor gain was chosen so that each band saturated at a ra- diance equivalent to the radiance from a turbid atmosphere with maximum water-leaving radianc- es. The signal radiances are typical of the maxi- mum radiances expected at a 45° scan angle. As shown, the SeaWiFS performance exceeds the goals in all six VNIR bands. In addition, since the sensor has a selectable gain (one of four values) prior to quantization, performance can be tailored to various expected signal levels. In the TIR region, the noise-equivalent tem- perature difference (NEAT) for a 300K scene was calculated, and Table 10 shows these results for various spectral-band pairs. These values are all well within the performance goal of 0.29K at 300K set forth in Section 4. The MTF was calculated at the Nyquist angu- lar frequency of 0.313 cy/mrad. The results indi- cate that the VNIR MTF will be 0.36 in the scan direction and 0.57 in the track direction; TIR MTF will be 0.34 and 0.53 in the scan and track direc- tions, respectively. These values correlate well with the nominal rule for sensor design that the MTF should equal or exceed 0.3 at the Nyquist frequency. SeaWiFS Baseline Spectral Bands Band Band Low chlorophyll Other pigments Baseline chlorophyll Subsurface scattering Atmospheric correction Atmospheric correction Sea-surface temperature Sea-surface temperature IMPLEMENTATION PANEL 53 54 Table 8. SeaWiFS Baseline Data Frame Format Synchronization Synchronization Identification Identification Time code Time code Telemetry Telemetry AVHRR back-scan data AVHRR space-view data Synchronization TIP data Spare/synchronization Data Synchronization Spare Spare Synchronization Calibration Spare Data Synchronization ZOE ONOOAWN= NOTE: Size is in 10-bit words, calibration = (2 TIR bands) x (10 calibration samples + 100 space samples) + (6 VNIR bands) x (50 space samples), and data = (8 bands) x (1274 samples per line) + (48 blanks). Table 9. SeaWiFS Estimated VNIR Radiometric Performance Saturation Signal Radiance! Radiancd (mW/cm2-sr-um) (mW/cm 2_sr-uum) 1 2 H. R. Gordon 1987: personal communication. See Table 3. Table 10. SeaWiFS Estimated TIR Radiometric Performance 10.50-12.50 3 S E 2 = 7) Zz uw 7) z2 fe) ke < N ra < — - O oO Figure 23. SeaWiFS estimated polarization sensitivity. 01sec N -20 0 20 OBJECT-SPACE SCAN ANGLE, DEG The polarization sensitivity depends on the scan angle, since the major contributor is the half-angle mirror. Figure 23 shows the SeaWiFS polarization sensitivity as a function of scan an- gle for fresh silver at a wavelength of 443 nm.'° The Thematic Mapper mirrors have measured polarization values very close to fresh silver, so this is a reasonable approximation to use. Also, calculating the polarization sensitivity at 443 nm is a worst case; the values are less at longer VNIR wavelengths. The figure shows that the polarization sensitivity is less than 1.4% and is significantly lower in the region around nadir. This allows those whose applications require even lower polarization sensitivities to still derive useful data from the SeaWiFS by using only the data acquired from near nadir. Calibration The high degree of calibration accuracy re- quired for SeaWiFS, described in Section 4, can be met only by using a multistep calibration pro- 1Onssumes 100% polarized input. cess since the calibration accuracy and preci- sion called for probably cannot be achieved through preflight ground calibration alone. Dur- ing ground calibration, a calibration accuracy of 3% will probably be acheivable for all bands. Af- ter launch, a data-gathering and calibration anal- ysis program will be required, as suggested in Section 3. Data gathered by ships coincident with SeaWiFS imagery will enable accurate cali- bration of the radiance measurements, probably to a calibration accuracy of about 1%. Calibration stability is actually more important than absolute radiometric precision. Because of this, a solar diffuser has been included in the in- strument, allowing periodic calibration of Sea- WiFS against the known exo-atmospheric solar il- lumination. Calibration against a lunar view was also requested by the users, since the moon acts as an almost ideal solar diffuser. Unfortunately, to provide this view on demand would require either an attitude adjustment of the spacecraft or the capability to point the instrument. Therefore, the moon will be considered a "target of opportu- nity," and a lunar calibration will take place only when the moon can be viewed during the space-view interval of the scan cycle. IMPLEMENTATION PANEL 55 56 Spacecraft Integration Spacecraft Configuration The current spacecraft configuration into which the SeaWiFS sensor would be integrated, differs from the original Landsat-6 spacecraft configuration due to programmatic changes and changes in the launch vehicle; the baseline launch vehicle is now expected to be a Titan Il. The concept is derived from a DMSP/TIROS-type system, but it has been extended to meet the Table 11. Capacity: Orbit: Power: Batteries: Solar array: 156 sq ft 150 A-hr capacity Sun-oriented array needs of the EOSAT mission and will change the spacecraft's flight orientation; the Titan II thrust axis (spacecraft long axis) is now the roll axis of the spacecraft and is perpendicular to the local vertical and in the plane of the orbit. Table 11 tabulates the key performance features of this spacecraft. The design concept utilizes equipment that is currently under NOAA contract for the STS ver- sion of the Landsat-6 spacecraft, combined with the latest versions of the DMSP S-15 program hardware. Spacecraft Characteristics, Exclusive of Payload 6000 pounds including the apogee kick motor Sun synchronous, 98.2° inclination; 705 km altitude 28V regulated power bus 1310W EOL array power to the load 1140W peak power at night Attitude: Star-referenced inertial guidance 0.01° about all axes Magnetic torquers and reaction wheels for attitude control Propulsion: Thiokol Star 37 XFP solid motor Hydrazine engines: 100 lbs and 0.5 Ib Cold gas control system Hydrazine orbit adjust subsystem Thermal: Communications: Louvers and heaters combined with thermal blankets X-Band System for the ETM mission data with three transmitters redundantly multiplexed to high-gain steerable antennas, S-Band command, telemetry, and ranging on an omnidirectional antenna Command Telemetry: Command and telemetry subsystem derived from the DMSP system of hardware in conjunction with Landsat units where appropriate. The SeaWiFS subsystem can best be accom- modated by the spacecraft system if it is designed to utilize the smallest possible amount of the growth-weight allocation and does not signifi- cantly increase the demand for critical power subsystem resources. This goal will be achieved best if the data-processing requirements on the spacecraft and ground segments are integrated. A more detailed System Integration Study is being conducted by EOSAT to better integrate the Sea- WiFS and the ETM data requirements and to de- termine optimal ways of accommodating SeaWiFS on Landsat-6. Required Modifications to the Landsat-6 Spacecraft for Integra- tion of SeaWiFS Although the baseline for the SeaWiFS equip- ment is still being developed at this time, NASA/ GSFC has proposed a potential configuration for it. Figure 24 shows the block diagram for this configuration. It is assumed that the SeaWiFS scan motor will be running continuously. However, the in- Figure 24. Block dia- gram of pro- posed con- figuration of the Sea- WiFS on the Landsat-6 spacecraft. SEAWIFS SENSOR "MIRP" SEAWIFS ELECTRONICS + ENCODED 40 MINUTES DAY- LIGHT PORTION/ ORBIT (4 KM) * HRPT FORMAT 665 KBPS strument will take data only during the 40 minutes per orbit when useable data can be acquired and will provide recorded data and real-time data transmission. During the instrument's operating phase, the sensor, data formatter, and signal switching unit will be operating, as well as record- ing units for global area coverage data and one S-Band or UHF transmitter. Other tape recor- ders will be used for up to 10 minutes during the 40 minutes of data-taking on each orbit to record high-resolution data. After the data are collect- ed, the recorded information will be transmitted to an EOSAT ground receiving station and then re- layed to the NASA ground-processing facility. In the recorder playback mode, the signal switching unit, one recorder unit, and one S-band transmit- ter will be operating. SeaWiFS equipment and their key features are listed in Table 12. The projected total subsystem weight of 153 pounds is well within the 360 pounds available for growth in the currently proposed spacecraft. Hence, the spacecraft can support the SeaWiFS mission and might also be able to satisfy an EOSAT goal of adding a third, spare wideband re- corder weighing 157 pounds. TAPE TAPE RECORDER RECORDER IMPLEMENTATION PANEL 57 58 Table 12. Sensor Electronics Heaters Data Formatter Switch Unit Data Recorder XMT S-Band Antenna S-Band XMT UHF Band Antenna UHF Harness Thermal Brackets Balances Data Management On-Board Data Processing The sensor's data stream will be formatted and the spacecraft's time code and ephemeris data incorporated into the format prior to record- ing or transmitting data. The attitude of the spacecraft (pitch, roll and yaw) will be reported with a within-limits flag. The baseline data format is similar to HRPT, and the high-resolution data from the sensor will nearly fill this format at 665 kbps. The low- resolution data rate is one-fourth the resolution and one-sixteenth the data rate, or 41.6 kbps. The low-resolution data will be reformatted to transmit at 56 kbps so they can be received by commercially available demodulators. The high- and the low-resolution data for real-time trans- mission will be encrypted by the SeaWiFS Data Formatter to protect their commercial value. Subscribers will be furnished encryption keys. Weight and Power Characteristics of the SeaWiFS System Weight faa Portion of CWS Motor & heater Preliminary Estimate Preliminary Estimate Record Playback |e ee ee ee eee “a os st it fD | PO On-Board Data Storage The maximum gap in the ability to receive a direct downlink from the satellite at the EOSAT ground station amounts to about eight orbits per day. Since the initially planned tape-recorder ca- pacity would be reached after four orbits, at first a second ground station was premised. However, an alternate configuration that com- bines the spacecraft Support resources for the SeaWiFS and ETM sensors was evaluated, and this configuration, in conjunction with an exten- sion in tape-recorder capacity, obviates the need for a second ground station. In the alternate configuration, a second transport is added to both ETM wideband recorders, i.e., the SeaWiFS and the ETM use identical recording units, and the tape speed is altered to increase its capacity. Not only does this provide maximum redundancy, but storage capacity is provided for SeaWiFS data from an additional four orbits, giving a total storage capacity of eight orbits per day. Eliminating the need for a second ground station offers two main advantages. First, the spacecraft can employ existing communications equipment for the playback data, reducing the amount of equipment on the spacecraft and re- quiring less operating power.'' Second, the glo- bal data set would be available at a single loca- tion at the EOSAT ground receiving station, and there would be no delays in data access due to shipping from a second, remote facility. The Sys- tem Integration Study is examining tradeoffs be- tween increased spacecraft tape recorder ca- pacity and the possibility of an additional ground receiving station, including the power required for nighttime data playback. Data Downlinks Current plans are for SeaWiFS to have three data downlinks. The first would be a stored-data link that would provide 40 minutes of global area coverage (GAC) and 10 minutes of local area coverage (LAC) to the EOSAT ground receiving facility. These data would be downlinked directly on the X-band. EOSAT will collect these data on some form of computer-compatible media and make them available to NASA for transfer to the NASA/GSFC ground receiving facility. The second data downlink would convey real-time, high-resolution LAC data, downlinked at 665 kbps, at a frequency compatible with cur- rently operating HRPT receiving stations and planned naval AN/SMQ-11 stations (probably L- band or S-band). The third data link would con- vey real-time, low-resolution GAC data to sub- scribers on a UHF frequency. These data would be transmitted at 56 kbps, allowing some sub- Mt is important to note that one of the key spacecraft limitations encountered in accommodating both the SeaWiFS mission and ETM mission on Landsat-6 lies in the power subsystem. These power constraints will affect mission operations, particularly with respect to nighttime operations. Some compromises in the ETM and SeaWiFS task profiles may be necessary to accom- modate the SeaWiFS mission. However, if the required compro- mises are unacceptable, expansion of spacecraft power re- sources will be addressed. scribers (e.g., moderately sized ships at sea that Cannot mount large, trainable, dish antennas) to use relatively inexpensive, commercially available receivers and fixed receiving antennas. The direct data downlinks will be provided on a subscription basis. No tape-recorded data would be available on either real-time link, and the real-time data will be encrypted to protect their commercial value. A key will probably be used for encryption and each subscriber will be supplied with a suitable key. The Implementation Panel recognized that re- ception of high-resolution LAC data is also de- sired by users restricted to unsophisticated re- ceiving stations. However, transmitting high- resolution data to a fixed antenna would require much greater power in the spacecraft transmitter than is available on the currently envisioned Landsat spacecraft. Adding the required power would not only be costly, but also might exceed the weight limitations of the spacecraft. One po- tential solution to this problem would be to pro- cess the 1.13-km data immediately upon receipt by the ground-receiving site, redistributing the data products via radio facsimile or telecommuni- cations links. The desire of some operational users to have near-real-time access to a global data set presents a greater problem, since the current data-handling plans for the tape-recorded global data set do not allow real-time access. A study is being undertaken to determine the feasibility of rerouting the X-band, downlinked global data set via communication links to the processing facili- ties of commercial and operational users. How- ever, this strategy is likely to be quite costly. Ground-Station Data Processing for Research Users Global data for research will be acquired from the EOSAT ground station on computer- compatible media and routed to a government ground-processing site. As currently envisioned, NASA will serve as the agent for processing and distributing these data. IMPLEMENTATION PANEL 59 60 The following levels of data processing will be undertaken: ® level 0. This is the raw data stream, |.e., what is contained on the ground station's tapes. This data stream will have navigation, predict- ed ephemeris elements, and attitude and housekeeping data within It. Level 1. This is Level O data in a reformatted structure, reversible to Level O, with calibration and navigation information within the header. The data product from this level of processing contains the total radiances for visible and near-infrared bands and brightness tempera- tures for thermal bands. The basic block of data will be determined by the recording peri- od. That is, for 4.5-km data, the basic block of data will be an entire orbit. For 1.13-km data, the smallest block of data will be the minimum recording period. A minimum recording period of 2 minutes is recommended, with a maximum of 12 minutes. Level 2. This level of data processing repre- sents the geophysical data in satellite swath format, not gridded nor resampled, and not re- versible to Level 1 format. The data product is a product derived from Level-1 containing chlorophyll-a, other pigments, water-leaving radiances, and sea-surface temperature. Level 3. This level of data processing con- sists of the geophysical data that have been resampled and/or composited - not reversible to Level-1 format. The data products are daily mosaics of nine Level-2 images on an 18-km grid with statistics including the number of pix- els, number of days, and sums of squares for each grid element. Weekly composites will be made of the geophysical data. Browse images will be available, consisting of all Level-1, -2, and -3 data products recorded on video disks. NASA will process all recorded high- and low- resolution data to Level-3 data products. The processing capacity has been sized to be twice that of the raw data rate to allow for processing backlog, implementation of improved algorithms, and possible processing of locally recorded HRPT data supplied to NASA. Archiving and Distribution of Data for Research All data products will be archived and distrib- uted through NSSDC/NODS. Three months of Level-1 data products and all Level-3 data prod- ucts will be accessible on-line at any time. Data will be loaded into the archive at monthly inter- vals, 1 to 2 months following collection. Cata- logue listings and inventory listings for digital and analog data, searchable by time and location via SPAN or other network systems, will be maintained and updated using the processing data base. NASA/GFSC will provide data products to its principal investigators, Announcement-of- Opportunity Investigators, and other national and international research users through the archival and distribution system described above. NASA will not offer its stored data to commercial or op- erational users in the private sector nor opera- tional users within the government. EOSAT will acquire copies of the data products for its ar- chive to serve all commercial and operational users. The system for processing and archiving the research data from SeaWiFS is based on the CZCS global data-processing and archiving effort underway at GSFC in terms of hardware, soft- ware, and methodology. Existing algorithms and processing times have been assumed for deter- mining pigment concentration and sea-surface temperature. Figure 25 summarizes the baseline SeaWiFS data acquisition and dissemination plans. Figure 25. Baseline Sea- WiFS data ac- quisition and dissemination plans. RAW LAC DATA, HRPT-COMPATIBLE TRACKING ANTENNA SUBSCRIBERS DATA ACQUISITION L- OR S-BAND RAW GAC DATA, 56 KBPS OMNI ANTENNA SUBSCRIBERS REAL TIME REAL TIME SEAWIFS PAYLOAD EOSAT GROUND- RECEIVING FACILITY RAW LAC, GAC DATA, HRPT-COMPATIBLE FORMAT SUBSCRIBERS EXPEDITED DATA ACCESS DATA RECORDING IMPLEMENTATION PANEL NASA/GSFC COMPUTER- GROUND- COMPATIBLE PROCESSING TAPES FACILITY DATA PRODUCTS LEVELS-O, PRODUCTS 1,2,3 LAC, GAC DATA PRODUCTS RESEARCH USERS 7- TO 10-DAY ACCESS 61 62 6 BIBLIOGRAPHY This bibliography is a compilation of citations contributed by a number of members of the Sea- WiFS Working Group. For the most part, it con- tains references only to works describing the bio- logical and physical processes that can be studied from satellite-acquired data on the ocean and the techniques through which these processes can be investigated. 63 64 rN Abbott, M.R., and P.M. Zion. 1984. Coastal Zone Color Scanner (CZCS) imagery of near surface phytoplankton pigment concentrations from the first coastal ocean dynamics experiment (CODE- 1). March-July 1981. JPL Publ. 84-42. Pasade- na, CA: Jet Propulsion Laboratory. 1985. Satellite observations of phyto- plankton variability during an upwelling event. Cont. Shelf Res. 4:661-80. Amidei, R., ed. 1985. Applications of remote sensing to fisheries and coastal resources. Re- port of a California Sea Grant workshop, No. T- CSGCP-012. La Jolla, CA: University of California, California Sea Grant College Program. Apel, J.R. and J.W. Sherman. 1973. Monitoring the seas from space: NOAA's requirements for oceanographic satellite data. Report AOML- LORS 6.73.1. Miami, FL: NOAA/DoC. Arnone, R.A. 1987. Satellite derived color- temperature relationship in the Albanian Sea. Re- mote Sensing Env. (In preparation.) Arnone, R.A., and P.E. LaViolette. 1986. Satellite definition of the bio-optical and thermal variation of coastal eddies associated with the African cur- rent. J. Geophys. Res. 9(C2):2351. Arvesen, J.C., J.P. Millard, and E.C. Weaver. 1973. Remote sensing of chlorophyll and temper- ature in marine and fresh waters. Astronaut. Acta. 18:229-39. Austin, R.W. 1974. The remote sensing of spec- tral radiance from below the ocean surface. In Optical aspects of oceanography, ed. N.G. Jerlov and E.S. Nielsen, chapter 14, pp. 317-44. Lon- don: Academic Press. 1979. Coastal Zone Color Scanner radi- ometry. SPIE Proc. 208:170-77. 1981. Remote sensing of the diffuse atten- uation coefficient of ocean water. 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(In press.) 79) 80 Appendix A DISCIPLINE - SPECIFIC VOCABULARY AND ACRONYMS Definitions Advection The flow of a current of water (as in the sea); also: trans- port by such a flow Anthropogenic Of, relating to, or resulting from the influence of human be- ings on nature Case-1 waters Waters in which phytoplankton and derivatives dominate in determining optical properties - generally the open ocean Case-2 waters Waters in which inorganic and/or organic sediments domi- nate in determining optical properties - generally coastal waters Epipelagic Of, relating to, or constituting the part of the oceanic zone into which enough light penetrates for photosynthesis Euphotic Of, relating to, or constituting the upper layers of a body of water into which sufficient light penetrates to permit growth of green plants Eutrophic Water rich in dissolved nutrients and often shallow with a seasonal deficiency in dissolved oxygen Fluvial Of, relating to, or living in a stream or river Gelbstoffe Yellow substance or blue absorbing matter Gyre A giant circular oceanic surface current Insolation Rate of delivery of direct solar radiation per unit of horizontal surface Intergrade (Vv) To merge gradually, one with another, through a continuous series of intermediate forms Intergrade (n) An intermediate form Macrophytes Large aquatic plants or seaweeds Mesoscale Of, or relating to, a meteorological or oceano- graphic phenomenon approximately 1 to 100 km in horizontal extent Mesotrophic Having a moderate amount of dissolved nutrients Movie loop A piece of film whose ends are spliced together so as to project the same material continuously Oligotrophic Deficient in nutrients and plant biomass Phaeophytin-a Degradation product of chlorophyll-a Phytoplankton Single-cell, drifting algae of the sea and other bodies of water. Most require only carbon diox- ide or carbonates as a source of carbon and in- go organic nutrients for metabolic synthesis. Phytoplankton pigments Any of various photosynthetic pigments of which chlorophyll-a and phaeophytin-a are usually the dominant components Plankton Passively floating or weakly swimming animal and plant life of a body of water Recruitment The addition of young to a natural population Trophic level One of the hierarchical strata of a food web characterized by organisms that are the same number of steps removed from the primary pro- ducers Troposphere The portion of the atmosphere below the strato- sphere that extends outward about 7 to 10 miles from the Earth's surface and in which tempera- ture generally decreases rapidly with altitude, clouds form, and convection is active Zooplankton Animal plankton Acronyms APT Analogue Picture Transmission AVHRR Advanced Very High Resolution Radiometer CZCS Coastal Zone Color Scanner ESA European Space Agency ETM Enhanced Thematic Mapper GAC Global Area Coverage GOFS Global Ocean Flux Study GSFC Goddard Space Flight Center HRPT High-Resolution Picture Transmission IFOV Instantaneous Field of View LAC Local Area Coverage LWIR Long-wavelength Infrared MAREX Marine Resources Experiment MIRP Manipulated Information Rate Processor NASA National Aeronautics and Space Administration NEAT Noise-Equivalent Temperature Difference NEPRF Naval Environmental Prediction and Research Fa- cility NMFS National Marine Fisheries Service OCI Ocean Color Imager ONR Office of Naval Research SNR Signal-to-noise ratio TESS Tactical Environmental Support System TIR Thermal Infrared VNIR Visible and Near Infrared APPENDIX A 83 84 Appendix B PARTICIPANTS Dr. Mark R. Abbott Univ. of Calif. - San Diego Scripps Inst. of Oceanography M/S A-002 La Jolla, CA 92093 Phone: 619-534-4791 818-354-4658 Mr. Robert A. Arnone NORDA Code 321 NSTL, MS 39529 Phone: 601-688-5268 Dr. D. James Baker Joint Oceanographic Institutions, Inc. 1755 Massachusetts Avenue, NW Suite 800 Washington, DC 20036 Phone: 202-232-3900 Dr. W. L. Barnes NASA Goddard Space Flight Center Code 625 Greenbelt, MD 20771 Phone: 301-286-8107, 8117 Ms. Cheryl Beck Naval Polar Oceanography Center 4301 Suitland Road Washington, DC 20390 Phone: 301-763-7439 Dr. Wm. P. Bishop Science Applications International Corp. (SAIC) 1710 Goodridge Drive Mail Stop G/6-1 McLean, VA 22102 Phone: 703-749-8931 Secty.: 703-821-5767 FAX: 442-0196 (Xerox 295) 85 86 Dr. Donald N. Brown Science Applications International Corp. (SAIC) 1710 Goodridge Drive McLean, VA 22102 Phone: 703-734-5847 FAX: 703-821-3071 Dr. Otis B. Brown Univ. of Miami RSMAS/MPO 4600 Rickenbacker Cswy. Miami, FL 33149-1098 Phone: 305-361-4018, 4770 Telex: 810-848-6067 FAX: 305-361-4622 Dr. Kendall L. Carder Univ. of South Florida 140 7th Avenue, South St. Petersburg, FL 33701 Phone: 813-893-9503 Ms. Pimporn Chavasant Naval Environmental Prediction Research Facility Airport Road Monterey, CA 93943-5006 Phone: 408-647-4752 Mr. Dennis K. Clark NOAA/NESDIS Ocean Sciences Branch SPC/Stop L Washington, DC 20233 Phone: 301-763-4244 Cdr. Stephen G. Colgan U.S. Navy Naval Polar Oceanography Center 4301 Suitland Road Washington, DC 20390 Phone: 301-763-5524 Dr. Peter Cornillon Univ. of Rhode Island Grad. School of Oceanography Narragansett, Rl 02882 Phone: 401-792-6283 Dr. Curtiss O. Davis Jet Propulsion Lab. Mail Stop 169-236 4800 Oak Grove Blvd. Pasadena, CA 91109 Phone: 818-354-5395 Dr. Frank Eden Joint Oceanographic Institutions, Inc. 1755 Massachusetts Ave., NW Washington, DC 20036 Phone: 202-232-3900 Dr. Richard W. Eppley Univ. of California - San Diego Scripps Inst. of Oceanography Mail Code A-018 La Jolla, CA 92093 Phone: 619-534-2338 Dr. Wayne E. Esaias NASA Goddard Space Flight Center Code 671 Greenbelt, MD 20771 Phone: FTS 888-5465 301-286-5465 Secty.: 301-286-6662 Dr. Robert E. Evans Univ. of Miami RSMAS/MPO 4600 Rickenbacker Cswy. Miami, FL 33149 Phone: 305-361-4018 Telex: 810-848-6067 FAX: 305-361-4622 Ms. Ruth Fay 1812 Coast Blvd Del Mar, CA 92014 Phone: 619-481-3786 Dr. Gene Carl Feldman NASA Goddard Space Flight Center Code 636 Greenbelt, MD 20771 Phone: 301-286-9428 Dr. David Fischel EOSAT 4300 Forbes Blvd. Lanham, MD 20706 Phone: 301-552-0623 Mr. Leo J. Fisher NOAA Natl. Marine Fisheries Service 1825 Connecticut Avenue, NW Washington, DC 20235 Phone: 202-673-5359 Dr. Catherine Gautier Univ. of Calif. - San Diego Scripps Inst. of Oceanography La Jolla, CA 92093 Phone: 619-534-4936 Mr. Leon Goldshlak Hughes Aircraft Co. Santa Barbara Research Center 75 Coromar Drive - B11/40 Goleta, CA 93117 Phone: 805-683-7173 FAX: 805-683-7149 Dr. Howard R. Gordon Professor of Physics Univ. of Miami Department of Physics Coral Gables, FL 33124 Phone: 305-284-2323 APPENDIX B Dr. James R. Haustein Mobil Research and Development Corporation Offshore Engineering 13777 Midway Road Dallas, TX 75244 P.O. Box 819047 Dallas, TX 75381-9047 Phone: 214-851-8344 Telex: 910-861-9058 FAX: 214-851-8349 Mr. Art Haworth WFOA P.O. Box 8978 Incline Village, NV 89450 Phone: 702-831-8862 Dr. John (Jack) M. Hill Associate Director Remote Sensing & Image Processing Laboratory Louisiana State Univ. Room 150, Electrical Eng. Bldg. Baton Rouge, LA 70803 Phone: 504-388-6826 Mr. Ken Hubbard EOSAT 4300 Forbes Blvd. Lanham, MD 20706 Phone: 301-552-0500 Ms. Mary F. Hughes Program Coordinator U.S. Dept. of Commerce NOAA/ Goddard Space Flight Center NOAA Landsat Operation Greenbelt, MD 20771 Phone: 301-286-9437 87 88 Dr. Matthew M. Jurotich NOAA/NESDIS/LTG Federal Building 4, Room 2051 Suitland, MD 20746 Phone: 301-763-4522 Dr. John L. Kermond Natl. Assoc. of State Universities and Land Grant Colleges One Dupont Circle, NW Suite 710 Washington, DC 20036-1191 Phone: 202-778-0823 Mr. Bob Kirk NASA Goddard Space Flight Center Code 671 Greenbelt, MD 20771 Phone: 301-286-7895 Mr. Daniel LaPorte Hughes Aircraft Co. Santa Barbara Research Center 75 Coromar Drive - B11/40 Goleta, CA 93117 Phone: 805-683-7196 FAX: 805-683-7149 Mr. Thomas D. Leming NOAA Natl. Marine Fisheries Service Natl. Space Technology Labs NSTL, MS 39529 Phone: 601-688-1214 504-646-7496 LCDR Jon Malay Naval Space Command Code N33 Dahlgren, VA 22448 Phone: 703-663-7873 Mr. John Maloney Vice President Oceanroutes, Inc. 680 W. Maude Avenue Sunnyvale, CA 94086-3518 Phone: 408-245-3600 Telex: 345-540 FAX: 408-245-5301 Mr. George K. Martch RCA Astro Space Division Locust Corner P.O. Box 800 Princeton, NJ 08650 Phone: 609-426-2414 Dr. Charles R. McClain NASA Goddard Space Flight Center Code 671 Greenbelt, MD 20771 Phone: 301-286-5377, 6662 Mr. Aram Mika Hughes Aircraft Co. Santa Barbara Research Center 75 Coromar Drive - B11/40 Goleta, CA 93117 Phone: 805-683-7260 FAX: 805-683-7149 Mr. Peter Mitchell U.S. Naval Research Lab. Code 8312 Washington, DC 20375 Phone: 202-767-3185 Dr. Erik Mollo-Christensen NASA Goddard Space Flight Center Code 670 Greenbelt, MD 20771 Phone: 301-286-6171 Mr. Don R. Montgomery NOAA/NESDIS Federal Building 4 Room 1069 Washington, DC 20233 Phone: 301-763-1564 Ms. Linda Moore EOSAT 4300 Forbes Blvd. Lanham, MD 20706 Phone: 301-552-0500 Mr. Ed Mowle EOSAT 4300 Forbes Blvd. Lanham, MD 20706 Phone: 301-552-0500 Dr. James L. Mueller Univ. of Calif. - San Diego Scripps Inst. of Oceanography Visibility Lab, POO3 La Jolla, CA 92093 Phone: 619-534-1756 Mr. Warren D. Nichols Hughes Aircraft Co. Santa Barbara Research Center 75 Coromar Drive - B1/15 Goleta, CA 93117 Phone: 805-562-2733 Dr. Eni G. Njoku NASA/Code EEC 600 Independence Avenue Washington, DC 20546 Phone: 202-453-1748 Dr. Vince Noble U.S. Naval Research Lab. Code 8310 Washington, DC 20375 Phone: 202-767-2330 Dr. Hal D. Palmer Marine Technology Society 2000 Florida Avenue, Suite 500 Washington, DC 20009 Phone: 202-462-7557 Dr. Polly A. Penhale National Science Foundation Polar Programs 1800 G Street, NW Washington, DC 20550 Phone: 202-357-7894 Dr. Mary Jane Perry Univ. of Washington School of Oceanography WB-10 Seattle, WA 98195 Phone: 206-543-2652 Mrs. Evelyn S. Putnam Hughes Aircraft Co. Santa Barbara Research Center 75 Coromar Drive - B11/40 Goleta, CA 93117 Phone: 805-683-7157 FAX: 805-683-7149 Dr. Mike Reeve National Science Foundation Head, Ocean Sciences Res. Sect. Ocean Sciences Division Room 611 Washington, DC 20550 Phone: 202-357-7924 Dr. Kenneth (Ken) W. Ruggles President Systems West, Inc. P.O. Box 222019 Carmel, CA 93922 Phone: 408-625-3653 FAX: 408-625-6913 Telex: 910-240-8768 89 90 Dr. William M. Sackett American Geophysical Union 2000 Florida Avenue, NW Washington, DC 20009 Phone: 202-462-6903, ext. 270 Dr. Raymond Sambrotto National Science Foundation OCE, Room 611 Washington, DC 20550 Phone: 202-357-9600 Mr. Joseph Schulman EOSAT 4300 Forbes Blvd. Lanham, MD 20706 Phone: 301-552-0621 Mr. William D. Siapno Ocean Mining Consultant Box 396 Ordinary, VA 23131 Phone: 804-642-3496 Dr. Raymond C. Smith Univ. of Calif. - Santa Barbara UCMBO/Geography Dept. Santa Barbara, CA 93106 Phone: 805-961-2618 Dr. John H. Steele Woods Hole Oceanographic Inst. Woods Hole, MA 02543 Phone: 617-548-1400 Mr. Fran Stetina NASA Goddard Space Flight Center Oceans Laboratory Code 675 Greenbelt, MD 20771 Phone: 301-286-5717 Dr. Richard P. Stumpf NOAA/NESDIS 1825 Connecticut Av., NW Code E/AI31 Washington, DC 20235 Phone: 202-673-5400 Mr. Jan Svejkovsky Ocean Imaging Co. 8367 Capricorn Way, Suite 4 San Diego, CA 92126 Phone: 619-549-3859 Dr. Phillip Taylor National Science Foundation Ocean Sciences 1800 G. Street, NW Room 609 Washington, DC 20816 Phone: 202-357-9600 Dr. Shelby G. Tilford NASA Director, Earth Science and Applications Division Office of Space Science and Applications Washington, DC 20546 Phone: 202-453-1706 Dr. Ron Tipper Capt. USN Director, Navy/NOAA Joint Ice Center 4301 Suitland Road Washington, DC 20390 Phone: 301-763-5524 ,2000,1111 Mr. Paul F. Uhlir Natl. Academy of Sciences Senior Program Officer Space Science Board 2101 Constitution Avenue, NW Washington, DC 20418 Phone: 202-334-3445 Mr. Charles H. Vermillion NASA Goddard Space Flight Center Code 675 Ocean Data Systems Office Greenbelt, MD 20771 Phone: 301-286-5111, 6171 Telex: 469077 DAWN CORP FAX: 301-286-2717 Dr. John J. Walsh Univ. of South Florida Dept. of Marine Sciences 140 7th Avenue, South St. Petersburg, FL 33703 Phone: 813-893-9164 Dr. Matthew Willard EOSAT 4300 Forbes Blvd. Lanham, MD 20706 Phone: 301-552-0570 Telex: 277685 LSAT UR FAX: 301-552-0507 Dr. Stan Wilson NASA Headquarters (EEC) Chief, Oceanic Processes Branch Washington, DC 20546 Phone: 202-453-1725 APPENDIX B Mr. Loren M. Woody Hughes Aircraft Co. Santa Barbara Research Center 75 Coromar Drive - B11/40 Goleta, CA 93117 Phone: 805-683-7299 FAX: 805-683-7149 Dr. Joe Wroblewski Office of Naval Research 800 N. Quincy Street Alexandria, VA 22217 Phone: 202-696-4530 Dr. Charles S. Yentsch Bigelow Laboratory for Ocean Sciences West McKown Point Boothbay Harbor, ME 04575 Phone: 207-633-2173 Dr. James A. Yoder NASA Headquarters Code EEC Washington, DC 20546 Phone: 202-453-1725 91 92 ee, NOTES NOTES MQ < Os [On Oe ae) Wore gg ° » BS ee ea = ATS DOCUMENT LIBRARY Woods Hole Oczanszrapaic Insiiiution OEMCO COMMERCIAL/OPERA- TIONAL USERS PANEL J. HAUSTEIN - MOBIL RESEARCH AND DEVELOPMENT CORP C. BECK — NAVAL POLAR OCEANOGRAPHY CENTER P. CHAVASANT — NAVAL ENVIRON. PREDICT. FACILITY R. FAY — OCEAN IMAGING CO L. FISHER — NATIONAL MARINE FISHERIES SERVICE A. HAWORTH — WFOA J. HILL — LOUISIANA STATE UNIVERSITY T, LEMING — NATIONAL MARINE FISHERIES SERVICE J. MALAY — NAVAL SPACE COMMAND J. MALONEY — OCEANROUTES, INC P. MITCHELL — U.S. NAVAL RESEARCH LABORATORY V. NOBLE — U.S. NAVAL RESEARCH LABORATORY H. PALMER — MARINE TECHNOLOGY SOCIETY E. PUTNAM — HUGHES/SBRC W. SIAPNO — CONSULTANT - OCEAN MINING J. SVEJKOVSKY — OCEAN IMAGING CO R. TIPPER — U.S. NAVY/NOAA JOINT ICE CENTER M. WILLARD — EOSAT C. WILLIAMS S. TILFORD J. HUSSY SeaWiFs WORKING GROUP E (9) Ps aul ey ay (2) fo} ea) J. BAKER - JOINT OCEANOGRAPHIC INSTITUTIONS, INC K. RUGGLES - SYSTEMS WEST, INC D. LaPORTE - HUGHES/SBRC RESEARCH USERS PANEL O. BROWN - UNIVERSITY OF MIAMI ABBOTT — SCRIPPS INST. OF OCEANOGRAPHY (UCSD) . ARNONE — NORDA . BROWN — SAIC COLGAN — NAVAL POLAR OCEANOGRAPHY CENTER CORNILLON — UNIVERSITY OF RHODE ISLAND DAVIS — JET PROPULSION LAB EDEN — JOI, INC EPPLEY — SCRIPPS INST. OF OCEANOGRAPHY (UCSD) GAUTIER — SCRIPPS INST. OF OCEANOGRAPHY (UCSD) HUGHES — NOAA/NESDIS LANDSAT TRANSITION GROUP . KERMOND —NATL. ASSOC. OF STATE UNIV.ERSITIES S9he Oo ae) Nc Dp a Ss == vm im © AND LAND GRANT COLLEGES McCLAIN — NASA/GSFC MOLLO-CHRISTENSEN — NASA/GSFC NJOKU — NASA/CODE EEC PENHALE — NSF POLAR PROGRAMS PERRY — UNIVERSITY OF WASHINGTON REEVE — NSF OCEAN SCIENCES RESEARCH SACKETT — AMERICAN GEOPHYSICAL UNION SAMBROTTO — NSF OCEAN SCIENCE RESEARCH . SMITH — UCSB STEELE — WOODS HOLE OCEANOGRAPHIC INST STETINA — NASA/GSFC TAYLOR — NSF OCEAN SCIENCES RESEARCH TIPPER — U.S. NAVY/NOAA JOINT ICE CENTER UHLIR — NAS SPACE SCIENCE BOARD WALSH — UNIVERSITY OF SOUTH FLORIDA WILSON — NASA HQ, OCEANIC PROCESSES BRANCH WROBLEWSK! — OFFICE OF NAVAL RESEARCH YENTSCH — BIGELOW LAB. FOR OCEAN SCIENCES YODER — NASA HQ, CODE EEC Spee as aad (J ua G) eA te oS) I no ful (qo) IMPLEMENTATION PANEL A. MIKA - HUGHES/SBRC BARNES — NASA/GSFC BISHOP — SAIC CARDER — UNIV. OF SOUTH FLORIDA . CLARK — NOAA/NESDIS DURHAM — HUGHES/SBRC - ESAIAS — NASA/GSFC EVANS — UNIVERSITY OF MIAMI FELDMAN — NASA/GSFC FISCHEL — EOSAT GOLDSHLAK — HUGHES/SBRC GORDON — UNIVERSITY OF MIAM | HUBBARD — EOSAT JUROTICH — NOAA/NESDIS LANDSAT TRANSITION GROUP . KIRK — NASA/GSFC MARTCH — RCA MOWLE — EOSAT MUELLER — SCRIPPS INST. OF OCEANOGRAPHY (UCSD) RUGGLES — SYSTEMS WEST SCHULMAN — EOSAT STUMPF — NOAA/NESDIS VERMILLION — NASA/GSFC . WOODY — HUGHES/SBRC EARTH OBSERVATION SATELLITE COMPANY e 4300 Forbes Boulevard e Lanham, Maryland 20706