seasat-a press kit

8/7/2019 Seasat-A Press Kit

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N E A NewsNational Aeronautics andSpace Ad ministrationWashington. D.C.20546AC 202 755-8370

PressKitFor Release IMMEDIATE

Project S e a s a t - ARELEASE NO: 7 8 - 7 7


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RELEASE NO: 78-77

CONTENTS

. GENERAL RELEASE .....................................MISSION DESCRIPTION .................................SCIENCE RATIONALE ...................................THE SPACECRAFT ......................................PAYLOAD.............................................DATA COLLECTION AND PROCESSING ......................LAUNCH VEHICLE SYSTEM (LVS) ........................MAJOR LAUNCH EVENTS FO R ATLAS F/SEASAT-A MISSION ....SEASAT-A EXPERIMENT TEAMS ...........................SEASAT-A MISSION TEAM ...............................SEASAT-A CONTRACTORS ................................

1-67-1415-2526-3334-3737-404142-4546-5051-5253-54

May 26. 1978


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NASANewsNational Aerona utics andSpace Adm inistrationWashington, D.C . 20546AC 202 755-8370

Dick McCormackHeadquarters, Washington, D.C.(Phone 2 0 2 / 7 5 5 -8 5 8 3 )

For Release:IMMEDIATE

Frank BristowNASA Jet Propulsion Laboratory, Pasadena, Calif.(Phone: 2 1 3 / 3 5 4 - 5 0 1 1 )

RELEASE NO: 7 8 - 7 7

NASA SATELLITE TO STUDY EARTH'S OCEANS FROM SPACE

NASA will launch Seasat-A, the first satellite to studythe world's oceans, from the Western Test Range, VandenbergAir Force Base, Lompoc, Calif., no earlier than June 24, 1 9 7 8 .

Seasat-A, a "proof-of-concept" mission, will be used todetermine if microwave instruments scanning the oceans fromspace can provide useful scientific data for oceanographers,meterorologists and commercial users of the seas.

The spacecraft will send back information on surfacewinds and temperatures, currents, wave heights, ice conditions,ocean topography and coastal storm activity.

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An Atlas-Agena launch vehicle will loft Seasat-A into aan 800-kilometer (500-mile) high near circular polar orbit.The spacecraft will circle the Earth 14 times a day and itsinstruments will sweep across 95 per cent of the oceans'surface every 36 hours, providing oceanographers with theirfirst synoptic, or worldwide, observation of the oceans.

Seasat-A will be used to prove the feasibility of lateremploying an operational, multiple-satellite Seasat networkto monitor the world's oceans on a continuous, near-real-time basis.

Twice daily, such a system could provide ships at seawith detailed charts of routes updated to show latest weatherconditions, sea state and hazards. Long-range use of thesystem could influence ship design, port development andselection of sites for such off-shore facilities as powerplants.

Other potential users of Seasat data include commercialfishermen, oil exploration firms, the Weather Service, pol-lution control agencies, the Coast Guard and Navy and avariety of others.

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The basic part of Seasat-A (engineers call it "thebus") is an Agena that serves as second stage of the launchvehicle and carries a sensor module on which the instrumentsand related science payload are mounted. Agena is a three-axis-stabilized spacecraft that has flown more than 300missions.

The spacecraft has all-weather capability, and can seeas well at night as in the daytime.

The instrument payload includes four microwave sensorsand a visual and infrared radiometer. Experiment teams,drawn from scientists representing various oceanographicdisciplines, will determine the geophysical significance ofthe microwave data.

The four microwave instruments are:

0 A scanning multifrequency nicrowave radiometer. Itwill measure sea surface temperature, estimate wind speedand detect water in the atmosphere (either vapor or liquid)to help scientists correct other instruments' data. DuncanRoss of the National Oceanic and Atmospheric Administration'sAtlantic Oceanographic and Meteorologic Laboratory, Miami,Fla., is team leader.

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0 A radar scatterometer will measure sea surface effectsthat can be converted directly to wind speed and direction.Prof. Willard Pierson of the State University of New Yorkis team leader.

0 A synthetic aperture radar (SAR) will provide all-weatherhigh-resolution pictures of ocean waves, ice fields, ice-bergs, ice leads (linear openings in ice through which shipsmay navigate) and coastal conditions. (The SAR also canreturn pictures of conditions on land.) The instrument willbe used only when Seasat-A can "see" one of the trackingstations specially equipped to handle its large amounts ofdata. Dr. Paul Teleki of the U.S. Geological Survey, Reston,Va., is team leader.

0 A radar altimeter serves two functions: It will1monitor average wave height and "significant wave height"-- a term oceanographers use to designate the largest one-third of all waves -- and the altitude of the spacecraftabove the ocean to a precision of 10 centimeters ( 4 inches).That will let scientists measure sea surface topographicfeatures that relate to ocean tides, storm surges and cur-rents. Dr. Byron Tapley of the University of Texas isteam leader.

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A fifth instrument aboard Seasat-A -- a visual andinfrared radiometer -- will provide data to support infor-mation from the microwave sensors. It will measure seasurface temperature in clear weather, and take pictures ofcloud patterns and ocean and coastal features. Dr. PaulMcClain of the National Oceanic and Atmospheric Administra-tion's National Environmental Satellite Service, Camp Springs,Md., is team leader.

While Seasat-A takes its measurement from space, anextensive program of "surface truth" also will be under way.Low flying aircraft, ships and instrumented buoys will takemeasurements to corroborate Seasat data.

Seasat-A's primary mission is for one year, but enoughfuel and other consumables are being put aboard so theflight can be extended for another two years.month or more after launch,scientists and engineers willcalibrate instruments and check out and improve computerprograms that have been designed to translate Seasat datainto useful information.

For the first

After the calibration phase is complete, the observationperiod will begin.

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This will be the primary test for Seasat: can aspacecraft carrying microwave instruments tell scientistsuseful things about the sea surface and the atmosphere andhow they interact?

If Seasat-A lives up to the expectations of those whobelieve the oceans can be studied from spacecraft, it couldlead to a global system that can continuously monitor theoceans.

The Seasat-A program is managed for NASA by the Officeof Space and Terrestrial Applications.Laboratory, Pasadena, Calif., manages the project and thesatellite system. NASA's Goddard Space Flight Center,Greenbelt, Md., provides tracking, orbit and attitude deter-mination for the mission and the Project Operations ControlCenter. NASA's Lewis Research Center, Cleveland, Ohio, hasmanagement responsibility for the launch vehicle. Launchcrew is provided by the U.S. Air Force Space and MissileTest Center. Lockheed Missiles & Space Co., Sunnyvale, Calif.,is prime contractor for the satellite system.

NASA's Jet Propulsion

(END OF GENERAL RELEASE. BACKGROUND INFORMATION FOLLOWS.)

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MISSION DESCRIPTION

The launch of Seasat-A is timed so that, once thespacecraft reaches the desired orbit, it will have atleast 30 days of full sunlight at the beginning of itsmission. The full Sun period will allow engineers to usemaximum spacecraft power during checkout and the engineer-ing assessment phase.

Seasat-A will be launched from the Western Test Rangeat Vandenberg Air Force Base, Calif. The Atlas-Agenalaunch vehicle will aim for an orbit that is circular, 800kilometers ( 5 0 0 miles) altitude, has an inclination of 108degrees and a period of 101 minutes (1 hour, 41 minutes).*The primary mission is scheduled f o r one year. Enoughfuel and other consumables are being put aboard the space-craft to allow for an additional two-year-long extended

mission.Seasat-A is a "proof-of-concept" mission with theseobjectives:0 Demonstrate techniques for global monitoring ofoceanographic phenomena and features:0 Provide oceanographic data of use to scientistsand to applications users; and0 Determine key features of an operational ocean-dynamics monitoring system.The major difference between Seasat-A and previousEarth observation satellites is the use of active and pas-sive microwave sensors to achieve an all-weather capability.The geophysical oceanographic measurement capabilities forSeasat-A are shown in Table 1. The altimeter andscatter-ometer benefit from the atmospheric corrections providedby the microwave radiometer.The altimeter provides measurements only at the nadirof ground track location. The synthetic aperture imagingradar looks out at a nadir angle of approximately 20 degrees.

*With these trajectory characteristics, sensors with 1,000 km(620 mi.) cross-track coverage will provide global repeatcoverage every 36 hours, using both day and night passes tocomplete the fill-in (Figure 1).-more-


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t25 m

Geophysical Oceanoqraphic Measurement Capabilitiesfor Seasat-A

25 m I

MEASUREMENT 1 RANGE 1 PRKISION/ACCURACY 1 RESOCUIION, Irm ISPACIAL GRID, lun 1 TEMPORAL GRID

t25 m 25m

sHous~cLouDs#ISLANDS V6lRRADIOMETER

GEOID 5 c m - M O mSURGES, l O c m - 10mTOPOGRAPHY LESS M A N6MONTHS* 20 cm I - l o1 . 6 - 12I 1

50 502 m/i OR *lo%ICROWAVERADIOMETER ' ds 36 h TO 95%COVERAGESURFACEWINDS f 2 m/a OR 10%f 20.i0.5 TO 1 .O m OR *lo%

50 100

N AD IR ON L Y.6 - 1236 h TO 95%COVERAGE

I IHEIGHT ALTIMETER 0.5 - 25 m

GRAVITYW A M S

1/14d NEARCONTINENTALU.S.I I

1.5' 1ELATIMI V61RABSOLUTE RADIOMETER CLEAR WEATHERI -2 -35OC 3 6 hI - 5-52.SURFACETEMPERATURE I I

1 0 II MICROWAVE 1 -2-35.CRADIOMETER AL L WEATHER I loo1001 .so 36 h- 5 km 3 6 h

1 IEXTENT MICROWAVEI RADIOMETER I 10-15h I 10-15 I 10-15 3 6 hSEA ICE1/14 EARC O N 1 N ENTALU.S.ICEBERGS I I > 2 5 m36h

OCEANFEATURES I 1/14 EARCONTINENTALU.S.36 hATMOSPHERICCORRECTIONS

WATER MICROWAVERADIOMETER i25m I 5 0 50

Table 1

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,qa S E A S A T - n 3 SEASAT -A P36 HR ORBITAL COVERAGE36 HR ORBITAL COVERAGE

12-24 HRS COVERAGE0-1 2 HRS COVERAGE


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The 100-km (62-mi.) swath then allows it to overlapits coverage with the scatterometer wind measurements.The scatterometer looks out both sides with narrowfan beams. The fan beams, placed 45 degrees forward and45 degrees back, allow two l o o k s at each piece of ocean

separated by 90 degrees, to allow a wind direction assess-ment. The fan beams extend on the ground from a surfaceincidence angle of 25 degrees to 55 degrees for the fullrange of winds (3-25 meters/second), and then to 65 degreesfor the higher winds (10-25 m/s). Below 25 degrees, thechanges in backscatter from different wind speeds are dif-ficult to differentiate. As a result measurements are notincluded in those small angles.The microwave radiometer scans +25 degrees acrosstrack, with a surface incidence angle of about 55 degrees.The visible and infrared radiometer scans horizon tohorizon, but only the middle 70 degrees of scan (or about

1,000 km -- 620 mi.) on the ground produce accurate tem-peratures. Angular distortions at the higher angles plusincreasingly long atmospheric path lengths make accurateinterpretation much more difficult.All of the instruments (except the imaging radar) areexpected to be operated continuously during most of themission to provide global coverage through on-board storageand then dump over one of the five NASA ground stationsexpected to be active in that period (see Figure 2).The imaging radar is to operate in real time only whenit is over appropriate high-data-rate Satellite Tracking

and Data Network (STDN) ground stations. Present plans forthe imaging radar use existing stations in Alaska, Californiaand Maryland (at Goddard Space Flight Center) and a newCanadian station at St. John's, Newfoundland, to cover allthe coastal waters of the U.S. and the major North Americanice fields of interest. A 24-hour ground trace is shownin Figure 3.

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SEASAT-ASTATION COVERAGEF i g u r e 2

80

0

I U -80 L0 180 I


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SEASAT-A24 hour GROUND TRACE

F i g u r e 3


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Project engineers and planners have divided the one-year primary mission into several phases:

craft is acquired by the first ground tracking station ofthe STDN . It will continue while the spacecraft receivesan initial checkout and the orbit is adjusted for launcherrors and determined to sufficient accuracy (ultimatealtitude accuracy will be a meter (three feet) or less).

The Initial Orbital Cruise Phase begins as the space-

The Engineering Assessment Phase will begin when theearly checkout is complete. Instruments aboard Seasat-Awill be calibrated against prelaunch test information.Algorithms (computer programs) specially designed forSeasat will be checked and updated or improved whereneeded. During this phase, which could last from 30 to 90days, the spacecraft, the sensors and the orbit must bechecked and made as near ideal as possible, in preparationfor the next phase -- the primary purpose of Seasat-A.The Observation Phase -- the key segment of Seasat'sproof-of-concept mission -- is broken down into two partsor subphases. Once the Engineering Assessment Phase ends,experiment teams, whose sole purpose is scientific evalua-tion of the instruments and computer algorithms, will takedata from the spacecraft sensors and other sources and de-termine how the information can be interpreted. Missionplanners refer to this work as geophysical evaluation, anddiscuss it as different entirely from the engineering eval-uation that precedes it.Once geophysical evaluation is complete, the second

phase begins. Now the mission teams will produce InterimGeophysical Data Records and distribute them to experi-menters and other users, independent of the evaluationteams. Sensors may be recalibrated in conjunction withsurface truth findings throughout this phase.During the observation phase, data will be taken fromall instruments (except the SAR) globally in an uninter-rupted stream, stored on the satellite and dumped to atracking station in three-hour segments.The Orbit Trim Phase will, from time to time, breakinto whatever work is going on. Interruptions will be

required whenever Seasat-A's orbit must be adjusted. Thesatellite will be removed from its cruise condition, con-figured for the orbit trim, the course correction will bemade and then the satellite will be returned to cruise.-more-


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Extended Operations -- the final phase -- is beingplanned. It would begin at the completion of Seasat'sfirst year of flight.Data from Seasat-A will be made available to users --after the experiment teams have completed their geophysical

evaluation -- in as timely a fashion as required for eachuser.When the data become available for everyday use, theU.S. Navy's Fleet Numerical Weather Central at Monterey,Calif., for example, will receive data within a few hoursof collection by the spacecraft. The eventual goal is toprovide weather data within six hours after it is collected.Data will be distributed by the project to other users --again, after the evaluation subphase is complete -- fromboth NASA's Jet Propulsion Laboratory, Pasadena, Calif.,and the Navy's computer operations.The Synthetic Aperture Radar will be used only on areal time basis. Since it collects data at the rate of110 million bits per second, it can operate only whenSeasat-A is within sight of a ground station equipped tohandle its data. These stations include Goldstone, Calif.;Merritt Island, Fla.; and Fairbanks, Alaska. The Canadiangovernment is planning to equip a station at St. John's,Newfoundland. The European Space Agency (ESA) is consideringsimilar plans for southern England.Project planners are setting up a mission plan thatreads more like a planetary encounter than an Earth-orbitingflight because mission activity builds with the passage oftime to a specific target period. The project aims at sup-port of a worldwide experiment in ocean and atmosphericsampling called the Global Atmospheric Research Project(GARP). Ships and aircraft from many nationsaround theworld will probe the air and sea during special samplingperiods in January and February, and again in June andJuly 1979.

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SCIENCE RATIONALE

The world's oceans play a fundamental role in thedynamics of the Earth's atmosphere and thus profoundlyaffect the weather and climate of the entire Earth.The oceans act as a planet-wide heat reservoir thatstores, distributes and then releases solar energy; thesea is also the source for most atmospheric moisture.Scientists have estimated that more than 4 0 per cent ofall the heat in the atmosphere comes from condensation ofwater vapor that enters the atmosphere by way of evapora-tion from the oceans.Exchanges between ocean and atmosphere produce large-scale transport of energy on a global scale, usually fromlower to higher latitudes, and have a major influence onweather and climate. A large portion of the heat energythat moves from the tropics to higher latitudes is carriedby ocean currents.The enormous quantities of energy involved are dramati-cally illustrated by hurricanes and typhoons. The sourceof their energy is heat stored in the oceans.Scientists believe it is unlikely they will ever beable to make reliable predictions of weather, climate,ocean currents and other oceanographic parameters withoutthe large-scale numerical models of atmospheric and oceaniccirculation that are possible only with satellite observations.A number of ocean science fields should be able toprofit, either directly or indirectly, from satellitestudies. Satellite oceanography is limited, generally tosurface and near-surface measurements in the few tens ofmeters below and above what scientists call the boundarylayer. That constraint is not as severe as it might appear,since data taken from satellites can be used with more con-ventionally derived information about vertical current andtemperature profiles, depth and changes in salinity.The areas of ocean-related science that can benefitfrom satellite information are marine geodesy and gravity;physical and biological oceanography; glaciology; boundarylayer meteorology; and climatology.

can benefit from satellite information: shipping, offshoreoil drilling and mining, fishing fleets and residents ofcoastal regions.

In addition, a number of applications oriented users

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It may be possible to monitor location and movementof oil spills from a satellite.Many Earth satellites have carried sensors with someapplications to oceanographic studies. Examples are TIROS,ITOS, Skylab, GEOS, Nimbus and the Applications Technology

Satellite (ATS) series. Seasat-A will be the first dedi-cated test bed for a new class of instrumentation -- micro-wave sensors -- that can operate independent of solar illum-ination and without having to cease operations because ofovercast.Seasat-A should add to our understanding of the oceansand the role they play in our lives in these fields:

Oceanography, Meteorology and ClimatologyWaves

Seasat-A should reveal the principal features of thedynamic behavior of ocean gravity waves, about which wenow have a dearth of quantitative data. Many fundamentalquestions remain largely unanswered.A comparison between theory and observation has beendifficult to obtain in large part due to the absence ofadequate experimental data on waves, especially under stormconditions. Because of this lack, not enough is known aboutthe genesis of waves in response to winds, their changingcharacteristics as they propagate over the ocean surface,their interactions with other surface wave fields, their

generating, in turn, of internal waves, their trapping andrefraction by strong currents and their attenuation as theyenter shallow waters and suffer major changes in amplitude,speed and direction before finally dissipating their remain-ing energy in erosive, often destructive assaults on thecoasts.Wave Heights -- The wave height information presentlyavailable has been generated largely by ships at sea. The_ _bulk of the information comes from some 1,200 ships, mostlyin the northern hemisphere, which report estimated waveconditions in terms of height, period and dominant directionof travel.Recently the GEOS-3 altimeter has begun to provide wavedata from space. Seasat's observations will be more accurateand cover the oceans much more systematically and completely.

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Seasat-A will make measurements of significant waveheight by means of its short pulse altimeter, the returnpulse broadening being a function of the wave amplitude.These measures will be good to 0.5 m (1.8 ft.) or + 10per cent in the 1 to 20 ( 3 . 8 to 65 ft.) range and ;ill beuniformly distributed over all the world's unfrozen oceansat a measurement density sufficiently great to permit theobtaining of good information about significant spatialvariations along the orbital track. Accurate measurementsof wave height every 50 km (31 mi.), for example, which isa reasonable operational schedule for Seasat-AI will resultin some 7,000 observations per day.

Wave Directional Spectra -- A very few weather ships,four or five in the North Atlantic and a single one in theNorth Pacific, record the wave height as a function of timeat a point. Non-directional frequency spectra can be de-duced from such records.Seasat-A will record wave directional spectra (i.e.,wave amplitude as a function of wavelength and propagationdirection) at some 5 0 0 or 600 locations in both hemispheres,using the coherent imaging radar of the type discussed inthe last section. It will thus, for the first time, fur-nish global, synoptic measures of wave height and directionalspectra which, together with the wind field, constitute themost basic quantities needed for open-ocean wave forecasting.Wave Images -- Where a wave field is not statisticallyhomogeneous, a spectral description is not adequate andwave images are required instead. This is true, for example,

of waves generated by intense storms, or in the study ofrefraction of waves as they enter shallower water, wherebathymetric features can lead to large concentrations ordilutions of wave energy.Wave generation, propagation, interaction and absorp-tion can be studied experimentally for a variety of condi-tions of wind speed, fetch and duration, using such data.Wave trapping and refraction through encounters with cur-rent systems is another phenomenon which can be elucidatedby means of Seasat-A wave images. Coupling between surfacewaves and internal waves can also be studied with the aidof imagery. Evidence has already been presented that effects

of internal waves are discernible in Landsat images in thevisible and near-infrared regions of the spectrum.

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Sea Surface TemperatureThe temperature of the ocean's surface, another oneof its basic characteristics, is currently mapped overcloud-free portions of the ocean by infrared radiometersoperating on Nimbus, N O M and SMS satellites, with pre-

cisions approaching + 1 deqree ~ ( 1 . 8 egrees F.). The tem-peratures of the remgining beclouded portions of the oceansurface are presently determined only from ships or buoys,however. Seasat-A's multichannel microwave radiometer willmap sea surface temperature under conditions of clouds orlight rains, albeit with considerably coarser spatial reso-lution and somewhat lower temperature precision than theinfrared instruments. However, the microwave measurementsshould represent bulk ocean temperatures more closely thanthe infrared measures do, particularly under conditionswhere light surface winds result in little surface mixing.temperature measurement for effects of atmospheric liquidand vaporous water and surface foam and roughness, must makeindependent determinations of these quantities by usingseveral frequencies and two polarizations. The records ofthe several channels, taken together, form the basis forthe determination of sea surface temperature, foam androughness and hence, high wind speeds, cloud distribution,atmospheric water vapor content and sea and lake ice cover.

The microwave radiometer, in order to correct the sea

Sea temperature is a parameter of considerable impor-tance in oceanic and atmospheric processes, since it reflectsthe absorption by the sea of that prime mover, solar energy.The difference between active and inactive hurricane seasonsmay be due to water temperatures in hurricane gestationareas just 2 to 3 degrees C ( 3 . 6 to 5.4 degrees F.) lowerthan average. Ocean temperature is a major factor in deter-mining the tone of weather and climate in coastal regionsof the world and indeed, as the North Pacific Experimentsuggests, may control short term climate on a continentalscale through its influence on the circumpolar jet stream.Maps of sea surface temperatures are very useful forunderstanding the dynamics of current systems such as theGulf Stream or Kuroshio, especially in winter and spring.Furthermore, open-ocean fish such as tuna tend to swim along

the lines of constant temperature at certain times in theirexcursions and thus ocean temperatures assist in marinebiological studies. In persistently cloudy areas such asthe Intertropical Convergence Zone or the Antarctic Circum-polar Current Region, temperatures derived from a microwaveradiometer will be of special value. Knowledge of sea sur-face temperature will also be important in connection withstudies of marine fog.

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Ice Fields and LeadsIce will be studied in several ways during theSeasat-A mission. The small-scale features of lake andpolar ice fields will be sampled frequently by the coherentimaging radar thereby providing data needed to chart iceleads, surface roughness characteristics, and motions ofridges, polynyas and openinqs in the ice, This informationwill be of value in studying the structure and dynamics ofice formations. Furthermore, there are indications thatthe age and thickness of ice may be determined from a pro-perly configured imaging radar.On a coarser but more nearly global scale, the micro-wave scanning radiometer should provide images of ice coverthat can be used to extrapolate the fine-grained imaging

radar coverage. Delineations of the edges of ice packs andglaciers and the general advance and retreat of ice covershould be possible with this device.

The information about the ice leads and openings willalso be of value in connection with the all-weather deter-mination of heat transfer into the atmosphere, which proceedsapproximately 1,000 times more rapidly across the water thanthe ice interface. Such data will be valuable for weatherand climate studies in the polar regions, where much of theworld's weather is spawned.Sea Surface Topoqraphy

The marine geoid is defined as the surface which wouldbe assumed by a motionless, uniform ocean under the influenceof the Earth's gravity and rotation, and uniform atmosphericpressure. Thus, it reflects only the effects of gravitationaland gross centripetal forces. Departures of the sea surfacefrom the geoid due to tides, currents, Coriolis force, wind,pressure and wave-making and other forces are grouped underthe term "sea surface topography." These departures, if mea-surable, can often be used to derive information on the forcingfunctions themselves.

The general strategy planned for conducting these topo-graphical experiments with Seasat-A includes the focusing ofefforts in the Western North Atlantic Quadrangle region de-fined by Goddard, Bermuda, Grand Turk and Cape Kennedy wherelaser trackers will yield accurate orbital heights for Sea-sat-A, and relatively good geoid information is available.

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The aim is to determine the sea surface topographyto about a third of a meter in this area, and to one or twometers elsewhere, or about a factor of two or more betterthan in the case of GEOS-C. In addition, the coverage pat-terns will be more uniform and complete in the case ofSeas t A.The Gulf Stream traverses this quadrangle and, in fact,exhibits all its major features in the area, i.e., relativelysteady flow, meanders and eddies.Tides -- The M tidal signal is relatively strong inthe quadrangle, and $he orbital paths are nearly paralleland orthogonal to the co-range lines there. The complicated,ill-understood transition from deep sea to coastal tides cana l s o be studied here.The deep ocean tides have amplitudes of the order ofa meter. It is anticipated that the determination of thedeep ocean tides on a global basis may be attempted by ana-lyzing the entire ensemble of data gathered over a period ofa year and solving say,for tidal amplitudes and phases, dis-

sipation Parmeters and quantities representing the yieldinqof the solid Earth in response to both the lunisolar gravi-tational effects and the loading of the ocean tides themselves.Tidal dissipations are thought to occur mainly in regions ofbroad continental shelves, such as the Patagonian Shelf andthe Bering Sea.Currents and the Oceanic Pressure Gradient -- The move-ment of water on a rotating Earth leads to a departure of thesurface of the ocean from the geoidal equipotential surfacedue to the balance between the horizontal component of thecoriolis acceleration and the resultant horizontal pressuregradient. The steady components of the dynamic topographyof the sea surface have an extreme range of the order of 2meters.The Seasat-A instrument complement will also includea thermal infrared imager which will aid in identifying andlocating ocean features such as currents, and thus facilitatethe interpretation of the altimeter records.The Seasat-A precision altimeter and tracking systems

will yield measurements along subsatellite tracks with anequatorial spacing of approximately 2,500 km (1,553 mi.)(and even less at higher latitudes). In three months, thetracks should overlay the equator at about 2 0 km (12 mi.)intervals. Variable topographic features which have suf-ficiently long time constants (or are periodic) and are largeenough to be sampled with this measurement precision and den-sity should be discernible against spatial variations in thebackground geoid. -more-


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It is anticipated, for example, that this approachwill be used to search for the transient mid-ocean currents,of a spatial scale of the order of 5 degrees, which haverecently been seen. Following them over the oceans as awhole will help greatly in the effort to understand howthey interact with the mean general circulation of the ocean,and thereby contribute significantly to the solution of thecentral problem in physical oceanography at the present time.

Tsunamis, Set-Up and Storm Surges -- Other oceanicdepartures from the geoid should b observable in the alti-metric signal if the satellite is overhead at the time andplace of occurrence. For example, a seismically excitedwave, or tsunami, should be detectable in mid-ocean as anear-periodic topographic ripple of perhaps 50 cm range anda couple of hundred kilometers in wavelength.disturbances last for tens of hours and ultimately traversethe entire ocean basin, there is a reasonable probabilityof observing one if it should occur during the lifetime ofthe spacecraft. The amplitude of a deep-ocean tsunami hasnever been measured.

Since these

Similarly, variations in the set-up of water againstthe coast due to longer term wind stress will be looked for,and the extreme form of this phenomenon, the storm surge,should be observable if the timing and positioning relativeto the satellite track are correct. Such an observation ofa storm surge is a low probability event but, if obtained,the data would be extremely valuable as checks on stormsurge prediction models.

Seasat-A will probably not solve the problems o f oceantides, currents and circulations completely, however, itsaccurate altimetry will permit important exploratory experi-ments to be conducted in all these areas. They should yielddata which will be of much intrinsic value, and will providethe foundation for planning the next phase of the program inthese areas of ocean science.Meteorology and Climatology

speeds, and to some extent, directions, by means of ascatterometer and a microwave radiometer. The former relieson Bragg scattering from wind-generated capillary waves,while the latter senses the increase in brightness tempera-ture due to foam and roughness. The fraction of the surfacecovered by the capillaries or the foam and roughness is afunction of wind speed.

Surface Winds -- Seasat-A will measure surface wind

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These instruments have both been operated on aircraftmissions and on Skylab.The Seasat-A surface wind data will be equivalent tosome 2 0 , 0 0 0 ship reports each day, roughly an order of mag-nitude larger than that presently provided by surface vessels.

Again, they will be more or less uniformly distributed overthe global oceans, thus filling the major gaps in the meteoro-logical coverage patterns which result from the fact that shipsare concentrated in the Northern Hemisphere, largely in theshipping lanes. Using wind data from the spacecraft in con-junction with ship, buoy and island information, it appearspossible to define the vector surface wind field throughoutthe planetary boundary layer every 2 4 hours, for speeds from4 to 5 m/sec to perhaps whole gale force or greater, on arelatively uniform grid of approximately 1,400 km (870 mi.)spacing.The definition of the surface wind over the oceans

will be a large step forward in ocean wave forecasting. Thewind data, used in conjunction with other surface-derivedinformation and wave directional spectra supplied by Seasat-Aas both initial and boundary values of the surface wave field,will allow development of an advanced, computerized globalwave forecast model whose potential monetary value to marineinterests is immense.Scientific problems in wind-wave interactions, such asthe generation and radiation of waves by intense storms, andin mixing processes in the upper layers of the ocean, may bestudied using the enhanced base of global data on winds,waves and ocean temperatures.The Planetary Atmosphere -- Coming, as they will, atthe time of the Global Atmosphere Research Project (GARP)/First GARP Global Experiment (FGGE) activities, these Sea-sat-A results will be especially relevant to the science ofthe atmosphere. The measurements of winds in the tropicsand of sea surface temperatures to be made by Seasat-A areexpected to be of real value in connection with weatherstudies in general and the FGGE in particular. Seasat-A isalso likely to play a useful role in the longer range studiesaimed at the second objective of GARP which is to investigate"the factors that determine the statistical properties of thegeneral circulation of the atmosphere which would lead to a

better understanding of the physical basis of climate."

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A significant improvement in the quality of theplanetary weather forecasts in the one-to-three-day intervalis expected to result from the infusion of Seasat-A datainto global weather prediction models. The improvement willoccur not only over the oceans but also over continentalareas, such as the East Coast and the western half of theUnited States, which are strongly affected by maritime con-ditions. The data-sparse Southern Hemisphere will benefitespecially. The quality of the forecasts there will increasesubstantially. This will result in both scientific and gen-eral gains in terms of our understanding of the atmosphereand the weather, and will permit studies of interhemisphereinteractions to get underway in earnest. The fierce meteoro-logical systems surrounding the Antarctic continent will alsobe susceptible to orderly study on a synoptic scale for thefirst time.

It is obvious that Seasat-A data will only form a por-tion of the total meteorological information entering intosynoptic or global scale weather and climate studies. How-ever, this expanded data base, containing global measurementsof surface wind, waves and sea temperature, will be an impor-tant and often unique adjunct to the data obtained from sur-face sources and from other spacecraft.

Solid Earth PhysicsThe Ocean Geoid

Although Seasat-A is designed primarily to give oceanicand atmospheric information, it will contribute significantlyto solid Earth geophysics as well.The present knowledge of the geoid is based on obser-vations of gravitational perturbations of satellite orbits,which reflect global features, and surface gravimetry whichprovides details in some local areas. The satellite alti-meter approach offers the best prospect for acquiring high-resolution ocean geoid data on a global basis. It has verylarge advantages over the conventional surface ship methodin terms of the practicalities of achieving worldwide coverage.The geoid data provided by the altimeter are not atten-

uated by height.will improve the spatial resolution of the global geoid. Theheight resolution is expected to be improved to a scale ofthe order of a meter.The regular coverage patterns of Seasat-A

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The fine structure of the geoid to be traced out bythe Seasat-A altimeter system is expected to reveal a greatdeal of information about the structure and dynamics of theEarth's crust. The small-scale undulations of the oceangeoid are manifestations of gravity anomalies which reflectdensity irregularities of corresponding scale and/or depth.Many of these, in turn, are considered to result from tem-perature patterns associated with convective flows withinthe asthenosphere. Upcurrents due to convection are thoughtto occur at ocean rise crests, and on their volcanic flanks.

Lithospheric dynamics will also be partially elucidatedby the high resolution surface gravity mapping obtained fromSeasat-A. The understanding of tectonic plate behavior nearsubduction zones associated with such phenomena as compressiveupbuckling will be increased.A continuing interplay between the oceans and the solid

The sedimentation pro-Earth is seen again in the continental shelves and abyssalplains, which are heavily sedimented.cess is influenced in significant ways by ocean waves, cur-rents, temperatures and nutrient levels. Thus, this aspectof the solid Earth's structure can be better understood throughan increased knowledge of ocean dynamics.

Fine resolution gravity maps will also permit moreeffective planning of other types of geophysical surveys thatuse, for example, heat flow probes, dredge hauls, seismic re-fraction profilometers, drill cores and precision depthsounders.Solid Earth Tidal Studies

The ocean tidal studies will also yield data on thesolid Earth tides. As mentioned earlier, the problem of theocean tides actually cannot be fully solved without simul-taneously determining the elastic behavior of the solid Earthas it responds not only to the lunisolar gravitational attrac-tions but also to the loading due to the ocean tides themselves.Once the ocean tides are known, intriguing possibilitiesfor detailed probing of the solid Earth can be opened up. Forexample, the ocean tidal currents flowing in the Earth's mag-netic field generate electric potentials which are functions

of the conductivity of both sea water and the solid Earth.Once the tides and currents are known, the influence of thesolid Earth on the potentials may be estimated, and the cor-responding effective conductivity as a function of effectivedepth in the Earth can be deduced.-more-


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Through this route, one may derive information aboutthe temperature distribution within the Earth's upper mantle,and draw inferences about the stress fields that may be re-sponsible for seismic activity.Oceanoaraphic and Geodetic Levelina

Oceanographic and geodetic methods have both been usedto determine the positions of the level surfaces along boththe east and west coasts of the United States. Mean sea levelappears to slope upward from the south to north by nearly ameter, relative to land based spirit leveling. This discrep-ancy cannot be explained in terms of the estimated accuraciesof the two procedures. The Seasat-A mission, with its capa-bility for accurate determination of sea surface topographyalong the U.S. East Coast, for example, may offer prospectsfor helping to resolve this long-standing controversy.

Orbital DynamicsThe very accurate tracking and altimetric systems em-ployed in the Seasat-A program will lead to considerable re-finements in the science of orbital dynamics. The effectsof high-order gravity perturbations will be better under-stood and accounted for. Non-gravitational perturbationssuch as those due to solar radiation pressure and residualatmospheric drag will be determined with increased accuracy.One result will be improved orbit determination and predic-tion models for other Earth-orbiting satellites.

Engineering ScienceA high technology system such as a spacecraft and theassociated ground facilities always brings along with it anumber of important developments in engineering science andtechnology. While it is difficult to specify exactly whatwill be the yield of Seasat-A in this regard, it is safe tospeculate that in the areas of microwave sensors, in laserand radar tracking technology, and perhaps in data handlingand dissemination, significant advances are to be expected.It is likely that other areas in space technology will beupgraded during the program, as well.

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- 2 6 -THE SPACECRAFT

The Agena, se cond s t a g e of t h e A t l a s F/Agena launchv e h i c l e , serves as t h e s a t e l l i t e b us pr o vi d in g a t t i t u d ec on t r o l , power , gu idan ce, t e l em et ry and command fu nc t i on s .The s en so r module i s t a i l o r e d s p e c i f i c a l l y f o r t h e Seasat-Apay load of f i v e microwave in s t ru me nt s and t h i e r an tennas .T o g e t h e r , t h e t w o modules are ab o u t 2 1 m ( 4 0 f t . ) l on g w i tha maximum di a m e te r of 1. 5 m (5 f t . ) w i t h o u t a p p e n d a g e s de-ployed . Atop t h e A t l a s b o o s te r r o c ke t , t h e e n t i r e s a t e l l i t ei s e n c l o s e d w i t h i n a 3-m (10 - f t . ) -d i am ete r nose f a i r i n gwhich matches t h e d i a m e t e r of t h e A t l a s . A f t e r b u r n o u t ofthe Agena s t a ge and i n j e c t i o n in t o th e 800-km (500-mi .)o r b i t , Seasat-A w e i g h t w i l l be n e a r l y 2 ,3 0 0 km C5,050 l b s . ) .r e s t r a i n e d a g a i n s t th e s e v e r e l a u nc h v i b r a t i o n d u r i n gp ow er ed f l i g h t . F o ll o wi n g t h e l aunch phase , appendages ,which w e r e l a t c h e d s e c u r e l y w i t h i n t h e nose f a i r i n g , a redeployed t o t h e i r o r b i t a l c o n f i g u r a t i o n . The Agena o r d-nance s ubs ys te m a c t u a t e s p i n p u l l e r s t o r e l e a s e n e a r l y ad oz en d e p lo y a b le s p a c e c r a f t e l e m e n t s i n c l u d i n g s o l a r p a n e l s ,an tennas and suppor t booms.( f i g u r e 4 ) l i k e a p e n c i l , t h e sensor and communicat ionsan t en n as p o i n t i n g t o ward E a r t h and t h e Agena ro ck e t noz z leand s o l a r p an e l s o p p o s i t e t ow ard space. Dominan t f ea tu re ofth e S e a sa t i s t h e S y n t h e t i c A p er t u re R ada r ( S A R ) an t en n a ,a 2.1 by 1 0 . 7 -m ( 7 by 3 5 - f t . ) p l an a r a r r a y d epl o yed p e r -p e n d i c u l a r t o t h e s a t e l l i t e body.

Many mechanical e l e m e n t s of t h e s a t e l l i t e a re r i g i d l y

I n o r b i t t h e s a t e l l i t e w i l l a p p e a r t o " s t a n d o n e nd "

S e a s a t - A i s c o n t i n u a l l y s t a b i l i z e d on t h r ee axes bya momentum whe el/h oriz on s e n s in g sy ste m t o a c c u r a t e l y p o i n tt h e s e n s or s a t t h e E a r t h ' s s u r f a c e .Hot-gas j e t s p ro vi de t h r u s t f o r a d j u s t in g t h e o r b i ta nd f o r a t t i t u d e c o n t r o l d u r i ng Agena bu rn a nd o r b i t a d j u s tp e r i o d s .

e l e c t r i c a l power.a re u se d p r i o r t o s o l a r p a n e l d ep lo ym en t an d s t o r e energyf o r pe ak power r e q u i r e m en t s a nd d u r i n g s o l a r e c l i p s ep e r i o d o p e r a t i o n s .m i l l i o n b i t s of i n f o r m a t i o n - - t h e e q u i v a l e n t of more t h a nt w o f u l l o r b i t s of measurements f r o m a l l s e n s o r s w i t h t h ee x c e p t i o n of t h e SAR . SAR d a t a i s n o t r eco r d ed .

Two 1 1- pa ne l s o l a r a r r a y s a re t h e p r i m ar y s o u r ce ofTwo n icke l-cadmium s to ra ge ba t t e r i e s

Data s t o r a g e c a p a c i t y on t h e s a t e l l i t e i s about 350

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Seasat-A On-Orbit Configuration

SCATTEROMETER

SYNTHETIC APERTURERADAR ANTENNA

MULT I-CHANN ELMICROWAVE RADIOMETERA N T E N N A No. 1VlRR RADIOMETER LASER RETROREFLECTOR

SAR DATAL I N K A N T E N N AF i g u r e 4

ALTIMETER


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Redundant S-band t r an s m i t t e r s and rece ive rs , f u n c t i o n -i n g as t r a n s p o n d e r s , p r o v i d e t h e c o mm un ic at io ns l i n k f o re n g i n e e r i n g an d s e n s o r t e l e m e t r y . A s e pa r a t e S-band t r a n s -m i t t e r p r o v i d e s t h e SAR downlink.I n a d d i t i on t o t h e p r im a ry t r a c k i n g i n f o r m a t i o n f ro m

S e a s a t ' s S-band com municat ions sys tem , t w o independentt r a c k i n g s y st em s a i d i n n a v i g a t i o n a nd o r b i t d e t er m i n at i o n .L a se r t r a c k i n g s i g n a l s o r i g i n a t e f rom g ro un d s i t e s and a rer e f l e c t e d f r o m a n a r r a y of r e t r o r e f l e c t o r s o n t h e s a t e l l i t e .A d ua l- fr eq ue nc y b ea co n t r a n s m i t s u l t r a s t a b l e c a r r i e r s t o aground t r a c k i ng ne twor k, TRANET.Power

The S e a s a t - A p o w e r s u b s y s t e m s u p p l i e s a l l e l e c t r i c a lpower t o t he s a t e l l i t e by ge n e r a t i n g , c on ve r t i ng a nd sw i t c h -i n g t h e power.Pr imary power source i s a p a i r o f s o l a r a r r a y s g e n e r a -t i n g a bo ut 1 , 0 0 0 w a t t s a t t h e b eg in ni ng of t h e m is s ion ,va r y ing t h r oughou t t h e m is s ion w i t h a minimum of 700 w a t t s .The p a n e l s , r o t a t a b l e on o ne a x i s , s u p p o rt 14.5 s q u a r e m( 1 5 6 s qu ar e f t . ) of s o l a r c e l l s .Two nickel-cadmium b a t t e r i e s , ke p t c ha r ge d by t h e s o l a ra r r a y s , s u p p l y a l l power d u r i n g a s c e n t t o o r b i t a nd d u r i n gs o l a r e c l i p s e p e r i o d s a nd a ugm en t s o l a r a r r a y power d u r i n gpeak loads . S o l a r e c l i p s e p e r io d s o c cu r i n a b ou t h a l f t h eo r b i t s d u r i n g t h e m is s ion .A d r i v e s y st em c on t i n uo u s l y p o s i t i o n s t h e a r r a y s a b o u tt h e i r c e n t r a l a x i s t o f a c e t he S un as t h e s a t e l l i t e p l y si t s o r b i t . The d r i v e sys tem, f e d d i r e c t i o n s by s u n s e n s o r sm ounted on t h e ou tboa r d pa ne l o f e a c h a r r a y , w i l l r o t a t et h e a r r a y s a b o ut 5 ,000 t i m e s d ur in g th e f i r s t ye ar o ff l i g h t .N o r m a l s a t e l l i t e power requi reme nts can vary f rom about5 0 0 t o 700 w a t t s but can exceed 1 , 2 0 0 w a t t s d u r i n g b r i e fp e r i o d s of SAR ope r a t i ons . During e me rgency c on d i t i o ns ,th e s a t e l l i t e can be powered down t o a bou t 450 w a t t s .Ave ra ge o r b i t a l power l oa d i s a bou t 7 0 0 w a t t s .

D a t a SvstemCommunications with Seasa t w i l l be S-band r a d i o l i n kb etw ee n t h e E a r t h s t a t i o n s of th e NASA S a t e l l i t e Track ingand Data Network ( S TDN ) an d t h e d a t a s y s te m a b oa r d t h es p a c e c r a f t .

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The u p l i n k c a r r i e s commands and ranging signals fromground s t a t i o n s t o t w o r ed u n d an t r ece iver s . The downlinkc a r r i e r , from one of a p a i r o f o ne -w at t t r a n s m i t t e r s , i smodulated by r a n g i n g s i g n a l s a n d r e a l t i m e a nd s t o r e d de -g i t a l d a t a .3 0 t h rece ive rs a re a lw ay s o n , o p e r a t i n g a t 2106 MHz .Only one t r a n s m i t t e r , s e l e c t e d by power-on command, i s ona t any one t i m e . T h e t r a n s m i t t e r s r a d i a t e a t 2287 MHz.Normally t h e downlink c a r r i e r w i l l be phase- locked t o t h eu p l i n k c a r r i e r -- a t r a n s m i t t e r a nd r e c e i v e r c om bi na ti onf u n c t i o n i n g as a t r a n s p o n d e r -- and r e l a t e d i n f re q u en c yby a known r a t i o . Two 0.5-m ( 2 0 i n .) -d i am e te r r e f l e c t i n gd i s k an t en n as a re use d i n o r b i t . A s t u b a n t e nn a w i l l beu se d d u r i n g a s c e n t a nd t h e p e r i o d p r i o r t o d e p l o y i n g t h eo r b i t a n te n na s .A s e p a r a t e f i v e - w a t t S-band t r a n s m i t t e r , w i t h i t s own

h e l i c a l an t en n a , s en d s a l l v e r y h i g h r a t e SA R d a t a i n r e a lt i m e t o s p e c i a l l y - e q u i p p e d STDN s t a t i o n s . SAR analog wide-band d a t a i s ac qu i re d o n ly when one of these s t a t i o n s i s i nview of the s a t e l l i t e .Ground commands, w hich can be t r a n s m i t t e d t o t h es a t e l l i t e a t 2 , 000 b i t s p e r s ec on d, a re of t w o t y p e s , r e a lt i m e and s t o r e d program commands, and prov ide c on t r o l o fs a t e l l i t e a nd s e n s o r o p e r a t i o n s . A l l commands a re 6 4 - b i twords decoded on the s a t e l l i t e . R e a l t i m e commands a res e n t s i n g l y a n d e x e c u te d i m m ed ia te ly upon r e c e i p t .program commands, s t o r e d i n t h e command memory f o r exec u-t i o n of a s eq uen ce o f e v e n t s , a re f o r m a t t e d i n t o m es sa ge s

of up t o 6 4 commands. Each of t w o r edundan t memoriess t o r e s 768 commands, al lo wi ng t h e S e a sa t t o o p e r a t e a u t o -m a t i c a l l y f o r up t o 20 o r b i t s . Commands can not be s t o r e df o r e x ec u t i on m o r e t h an s i x d ays a f t e r t he y a re l o a d e d i n t ot h e memory.

S t o r e d

During normal o p e ra t i o ns , command lo ad freq uen cy w i l lbe one 256-command lo a d eve ry f i v e t o 1 2 hours . Dur ingh i g h - a c t i v i t y p e r io d s , more f r e q u en t l o ad s may be r e q u i r ed .Data t e l em e t e r ed f r o m Seasa t -A w i l l c o n s i s t of en-g i n ee r i n g an d s en s o r m easu rem en ts p r ep a r ed f o r t r a n s m i s s i o nby t h e t e l e m e t r y f o r m a t t e r .

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Encoded informat ion w i l l i n d i c a t e v o l t a g e s , p r e s s u r e s ,t e m pe r a tu r e s a nd o t h e r va lu e s m ea su re d by t h e s p a c e c r a f tt e l e m e t r y s e n s o r s as w e l l a s pa y loa d s e ns o r d a t a which c a nbe t r a n s l a t e d l a t e r i n t o ge o phys i c a l m ea su re me nt s.

I n r e a l t i m e o p e r a t i o n , d a t a i s s e n t t o one of twot a p e r e c o r d e r s and t o t h e t r a n s m i t t e r , s im u lt an e ou s ly , a t25 k i l o b i t s p e r s ec on d. D ur in g p l a yb a c k , on e t a p e r e c o r d e rmodulates t h e downlink a t 800 k bp s w hi l e t h e o t h e r recor-d e r i s s t o r i n g d a t a f o r playback . The 32: l p layback- re-corded r a t i o a l lows more t h a n t w o o r b i t s of d a t a (EO0 m i n -u t e s ) t o be p layed back t o a STDN s t a t i o n i n l e s s t h a nseven minutes -- e a s i l y accompl ished i n s i n g l e s t a t i o n p a s s .N o SA R d a t a i s recorded. The S A R o p e r a t e s o n l y 10 t o1 5 m inu te s du r ing se lec ted o r b i t s ( a bou t 4 p e r c e n t of t h em is s ion t i m e ) a s it o v e r f l i e s one of f i v e ground s t a t i o n swhich can rece ive th e widebank te le me t ry stream. The on-

board S A R d a t a a nd t r a n s m i s s i o n s y s t em s o p e r a t e i n d e pe n d e nt l yo f t h e s a t e l l i t e communications system.T r a c k ing The S p a c e c r a f t

T o a ch ie ve t h e d e s i r e d o r b i t a l p e r i o d, e c c e n t r i c i t yand a l t i t u d e a c c u r a c i e s and t o s u p p o r t s c i e n c e d a t a p ro -c e s s i n g , v e r y p r e c i s e o r b i t d e t e r m i n a t i o n i s r e q u i r e d .T h r e e i ndepe nden t t r a c k in g s y s t em s p r ov ide t h e n e c e s s a r ymeasurements .F o r t h e s t a n d a r d D op pl er t r a c k i n g d a t a , t h e S -band

s i g n a l w i t h r a n gi n g c od es i n s e r t e d i s t r a n s m i t t e d f r o m t h eSTDN s t a t i o n s , r e c ie v ed a t t h e s a t e l l i t e ch an ged i n f r e -quency by a known r a t i o a n d r e - t r a n s m i t t e d t o E a r t h .p o s s i b l e t o d et er mi ne p r e c i s e l y t h e t i m e de l a y a nd th eD o p p l e r s h i f t of t h e r e c e i v e d s i g n a l , t h e re b y me as ur in gr a n g e an d v e l o c i t y r e l a t i v e t o t h e g ro un d s t a t i o n . T h i si s c a l l e d coh ere nt two-way t ra ck in g. Noncoherent one-wayt r a c k i n g i s when no up l ink s igna l i s re ce iv ed and t h e down-l i n k c a r r i e r f r equency i s provided by an onboard o s c i l l a t o r .

I t i s

A ground rece iver n e t w o r k , c a l l e d TRANET, o p e r a t e d byth e Department of Defense , r ece ives a dual f requency Dop-p l e r be ac on f rom S e a sa t . The t r ac k in g measurements w i l lbe used t o supplement the STDN S-band t r a c k i n g f o r o r b i tde t e r m ina t i on . Onboa rd e qu ipm en t i nc lud e s a n u l t r a s t a b l eCW t r a n s m i t t e r r a d i a t i n g a t 1 6 2 MHz and 324 MHz. S e a sa ta l s o w i l l use t h i s f requency onboard as t h e s o u r c e f o rs a t e l l i t e t iming .

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The t h i r d t r a c k i n g s y st em u s e s a w o r l d w i d e ne twork ofl a s e r s t a t i o n s , some o p e r a t e d by t h e STDN a nd o t h e r s b yt h e Smi thson ian As t r ophy s ica l Observa tory . 1Jsed a t s e l e c t e dtimes for c a l i b r a t i o n of t h e r a d a r a l t i m e te r , t h e l a s e rs i g n a l s , o r i g i n a t in g a t t h e ground s i t e s , a re beamed a t t h es a t e l l i t e s , r e f l e c t e d f r o m c o r n er cube" r e t r o r e f l e c t o r sand de t e c t e d on t h e ground. A r i n g of q u a r t z r e f l e c t o rc u b e s a b o u t 1 0 1 c m ( 4 0 i n . ) i n di am et er i s mounted on t h esensor module .A t t i t u d e C o n t r o l

The a s c e n t po r t i on of t h e a t t i t u d e c o n t r o l sy ste mp ro vi de s s t a b i l i z a t i o n of t h e S e a s a t a f t e r A t l a s s e p a r a t i o nand dur ing t w o f i r i n g s o f t h e Agena engine and controlsd u r a t i o n o f t h e engine burns .Fo ll ow in g o r b i t a l i n s e r t i o n , it a l s o o r i e n t s t h es a t e l l i t e from nose-forward t o nose-down and pr ov id ess t a b i l i z a t i o n d u r i n g dep lo ym en t of an tennas and s o l a r a r -r a y s = These f un c t i ons a r e per fo rm ed u s ing hyd r a z ine r e a c -t i o n c o n t r o l t h r u s t e r s f o r a t t i t u d e c o n t r o l and a gy ror e f er e n ce u n i t as o ne a t t i t u d e r e f e r e n c e , augmented byh o r iz o n s e n s o r s f o r a s h o r t p e r i o d p r i o r t o nose-down.A t w o t a nk hyd r a z ine s upp ly f e e d s s e t s of o r b i t a d ju s tand r e a c t i o n c o n t r o l t h r u s t e r s .High-mode t h r u s t e r s , 53.4-newton ( 1 2 l b . ) a re us e d du r inga s c e n t . F or o r b i t a d j u s t m an eu ve rs , t w o 22.2-N ( 5 - lb . )t h r u s t e r s a re mounted i n t h e Agena forward sec t ion so t h a tt h r u s t i s a p pl ie d i n e i t h e r d i r e c t i o n a lo nq t h e o r b i t a la x i s . D uring o r b i t a d j u s t p e r i o d s , l o w mode reaction con-t r o l t h r u s t e r s ( 1 . 8 - N o r . 4 l b . ) m ai nt ai n s a t e l l i t e a t t i t u d e .r e f e r e n c e d t o t h e g y r o u n i t .The i n i t i a l o r b i t a d j u s t maneuver i s des igned t o cor -r e c t i n j e c t i o n e r r o r s and w i l l be conducted about a weeka f t e r l a unc h when p r e c i s e o r b i t de t e r m ina t i on ha s be en madef rom an undis tu rbed s a t e l l i t e . Subsequent o r b i t t r i mmaneuvers , planned t o o c c u r n o t m o r e than once a month, w i l lbe used t o c om pe ns at e f o r a t m o s p he r i c d r a g , s o l a r p r e s s u r eand o t h e r s u b t l e o r b i t de g ra d at io n s. P r o p e l l a n t a l l o c a t i o nh a s been made fo r a th r ee -y ea r mis s ion .During nor ma l ope r a t i on s i n o r b i t , Seasa t i s t h ree -ax is s t a b i l i z e d by momentum wheels and g r a v i t y g r a d i e n tt e c hn ique s .

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- 3 2 -

S e ns o r p o i n t i n g r e q u i r em e n t s i n c l u d e c o n t r o l t o an ac-curacy of .5 d e g re e i n r o l l , p i t c h a nd yaw and t e l e m e t e r e dd a t a on s a t e l l i t e o r i e n t a t i o n t o an accur acy of .2-degreei n a l l a xe s. S ca nw he el s p r o v id e p i t c h and r o l l r e f e r e n c e sv iewing the E a r t h ' s h o r i z o n a n d p i t c h and r o l l f i n e con-t r o l . Y aw a t t i t u d e i s ma int ain ed by gyrocompassing. Suns e n s o r d a t a i s used t o d e t er m i n e a c c u r a t e l y yaw o r i e n t a t i o n ,b u t i s n o t u se d f o r c o n t r o l . T h e scanwheels a r e mounted a tt h e lower e nd o f t h e s e ns o r modu le ne a r a l l o f t h e c r i t i c a lan te nn as . P i t c h momentum wheel and roll r e a c t i o n w h e e l a rel o c a t e d i n a s u pp o rt s t r u c t u r e above t h e sensor module .Excess momentum accumulated i n t h e w heels i s removed by pro-v i d i n g a d j u s t i b l e t or q u e on t h e s a t e l l i t e u s i n g e l e c t r o -magnets which i n t e r a c t w i t h t h e E a r t h ' s m ag ne ti c f i e l d .Sensor Module

The se n so r module i s a p l a tf o r m f o r t h e o p e r a t i o n oft h e f i v e s e n s or s t o a c h ie v e t h e m i s si o n o b j e c t i v e s w i t h i nt h e r e q u i r e d r e s o l u t i o n a nd a cc ur ac y. The s e n s o r s a re l o -c a te d i n p o s i t io n s r e l a t i v e t o one ano t he r and t o t h e bea-con, l a s e r r e t r o r e f l e c t o r a nd c o mm un ic at io ns a n te n n as sot h a t e a c h h a s a n u n o b s t r u c t ed f i e l d o f v ie w a nd e ac ha c h i e ve s t h e r e q u i r e d po in t i ng a nd s c a n a ng l e . M ountingp o s i t i o n s also were se l ec t ed t o p r e v e n t e l e c t r o m a g n e t i ci n t e r f e r e n c e betw ee n m u l t i p l e r a d i a t i n g s o u rc e s .The s e ns o r m odule' s p r im a ry s t r u c tu r e i s a 25.4-cm( 10 - in . ) - d ia m e te r aluminum a l l o y t u bu l a r m a s t t o which

equipment mounts a re a t t a c h e d .Two scanwheel assemblies a re mounted near the forwarde n d o n t u b u l a r s u p p o r t s t o g i v e ea ch u n i t a c l e a r v i e w ofE a r t h ' s h o r i z o n .The Radar A l t i m e t e r (ALT) i s mounted a t t h e end of t h em a s t s t r u c t u r e -- n e a r e s t t h e E a r th -- t h e one-meter d iam ete rr e f l e c t o r a nt en na a nd RF u n i t on t h e forward end and t h es i g n a l p r o ce s s or t o t h e s i d e . The r i n g of c o r ne r c ubeq u a r t z r e f l e c t o r s f o r t he l a s e r t r a c k i n g s y st e m su r r o un d st h e a l t i m e t e r an tenna and RF e l e c t r o n i c s m odule.

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The Microwave Scatterometer (SASS) and Doppler beacont r a n s m i t t e r f o r t h e TRANET t r a c k i n g s y s t e m a r e mounted i n as u pp o rt s t r u c t u r e on t h e s i d e of t h e m as t. F our s l o t t e da r r a y s t i c k an te nn as f o r t h e SASS a r e s to we d a g a i n s t t h es t r u c t u r e and each d e p l o y e d s e p a r a t e l y . The TRANET an tennai s a t t ac h e d t o a dep loyab le boom which a l s o s upp or t s one o ft h e t w o S-band communicat ions an ten na s. T h e second i s de-ployed on a se pa ra te boom.The V i s i b l e a n d I n f r a r e d Radiometer ( V I R R ) c o n s i s t s o fa sc an ne r mounted on a dep loya b le boom and e l e c t r o n i c s ont h e mast tube.T h e f ive -cha nne l Scanning Mul t i f re que ncy MicrowaveRadiometer (SMMR) i s mounted as a s i n g l e u n i t on t h e s i d eo f t h e s e n s o r module s t r u c t u r e . T h e u n i t i n c l u de s f i x e do f f s e t p a r a b o l ic r e f l e c t o r , s can m echanism and d i g i t a l p r o -

c e s s o r .The S y n t h e t i c A p e r tu r e R ad ar ( S A R ) antenna and e l ec -t r o n i c s a r e i n s t a l l e d n e ar t h e base of t h e sensor module .The huge SAR s e n s o r a n t e n n a i s i n e i g h t se gm e nt s, f o l d e ddur ing l aunch and dep loyed t o form a f l a t r e c t a n g u la r a r -r a y w i t h a n area of 2 3 sq. m (245 sq. f t . ) The SAR down-l i n k t r a n s m i t t e r i s mounted on t h e m a s t and i t s h e l i c a lan tenna i s deployed on a s h o r t boom.

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- 3 4 -PAYLOAD

Radar AltimeterThe Radar Altimeter traces a 2 to 106 .2 5 mi.) wide path (dependent on surface

a line directly below the satellite. Themeasures average wave height to within 10of 2 to 2 0 m ( 6 to 6 5 ft.) and the height

km ( 1 . 2 5 toroughness), onRadar Altimeterper cent over a rangeof t'he spacecraftabove the ocean to a precision of 10 cm ( 4 in.).

The height measurements should allow determination ofsea-surface topographic features that correspond to oceantides, storm surges and currents.The altimeter generates a 1 3 . 5 6 gigahertz chirp signalat two kilowatts peak power. The signal is radiated to Earththrough a 1-m (39-in.) antenna that looks at the sub-spacecraftpoint.The reflected signal, when received at the spacecraft, isamplified, converted from analog to digital and processeddigitally in the sensor.That processing includes:0 Acquisition and tracking of the returned signal;

Development of estimates of altitude and wave state;Relaying the onboard measurements and other data fortransmission to Earth for additional processing.

The Radar Altimeter uses 177 watts and weighs 9 3 . 8 kg( 2 0 6 . 8 Ib.). Dr. Byron Tapley of the University of Texasis team leader.Scanning Multichannel Microwave Radiometer (SMMR)

The Scanning Multichannel Microwave Radiometer data areused to derive sea surface temperatures, wind speed andatmospheric water content. It measures absolute levels andrelative variations in the microwave radiation it receivesfrom the surface.

The instrument measures surface temperature with aprecision of 1 1 / 2 to 2 degrees Celsius ( 2 . 7 to 3 .6 degreesFahrenheit); wind speeds up to 5 0 meters per second (110 milesan hour); and provides atmospheric correction data to otherinstruments by measuring water vapor content in the atmosphere.- more -


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It observes an area beneath the satellite 690 km (430 mi.)wide.SMMR uses a scanning 42-degree-offset parabolic antennato receive the signal from Earth, It measures horizontal and

vertical polarization components of microwave radiation at 6.6gigahertz, 10.69 GHz, 18.0 GHz, 21.0 GHz and 37.0 GHz. Thesignal is then converted from analog to digital in theinstrument and is fed into the satellite telemetry datastream to Earth for final processing.The Scanning Multichannel Microwave Radiometer uses59.66 watts of power. It weighs 53.9 kg (118.8 lb.).Duncan R o s s of the National Oceanic and AtmosphericAdministration's Atlantic Oceanographic and MeteorologicLaboratory, Miami, Fla., is team leader.

Microwave Scatterometer (SASS)The Scatterometer measures fine-scale ocean-surfaceroughness caused by surface winds. The measurements can beconverted directly into wind speed and direction.The Scatterometer measures wind speed from 4 m/s (9 mph)to 48 m/s (107 mph), to an accuracy of 10 per cent or 2 m/s(4.5 mph), whichever is greater, and wind direction to 20per centThe instrument measures wind speed and direction in twosurface swaths on each side of the spacecraft, each 500 km(310 mi.) wide. The scatterometer can measure wind speedonly for an additional 250 km (155 mi.) on each side of themain swaths.The SASS generates a 14.6 gigahertz signal at 100-wattpeak power that is radiated to Earth through four fan-beamantennas that have vertical and horizontal polarization.The reflected signal is received, amplified and convertedfrom analog to digital within the sensor. It is then routedto the satellite data system for transmission to Earth forprocessing.The electronics assembly weighs 59 kg (130 lb.) , andeach antenna weighs 11 kg (24 lb.) for a total weight of103 kg (227 lb.).Professor Willard J. Pierson of the City University ofNew York is team leader.

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Visual and Infrared Radiometer (VIRR)The Visual and Infrared Radiometer is not a microwaveinstrument; its primary purpose is to provide supporting datafor the four microwave experiments.The VIRR will provide images of atmospheric conditions,cloud coverage patterns, ocean and coastal features: it willalso provide sea surface temperature maps.Visual image resolution will be 2 km (1.2 mi.): infraredimage resolution will be 4 km (2.4 mi.), over a 2,100-km-wide(1,300-mi.) surface swath.Radiation emitted from Earth is collected by an elliptical-shaped scan mirror that directs it into a dichroic beamsplitter. Infrared radiation is sent to a bolometer detector,while visible radiation is sent to a silicon PV detector. Thesignals are amplified, filtered and sent to the satellitetelemetry system as analoq siqnals. They are diqitized by thesatellite data processing-system for transmissionprocessing.The instrument, consisting of an electronicsscanner, weighs 8.1 kg (17.85 1b.)- It uses 7.3power.Dr. Paul McClain of the National Oceanic andAdministration's National Environmental SatelliteCamp Springs, Md., is team leader.

Synthetic ADerture Radar ( S AR I

to Earth for

module and awatts of

AtmosphericService,

The Synthetic Aperture Radar will provide allyweatherpictures of ocean waves, ice fields, icebergs, ice leads(linear openings in sea ice), fresh water ice, land, snowcover and coastal conditions. It will also provide oceanwave spectra including wave direction.The instrument produces images with resolution of 25 m(80 ft.) over a swath 100 km (62 mi.) wide. A typical passwith the instrument will last 10 minutes.The SAR is the first NASA radar system of its kind designedto study ocean wave patterns from orbit. The system consists ofa deployable radar antenna 2.1 m (7 ft.) by 10.7 m (35 ft.): aSAR sensor including a solid-state transmitter, low-noisereceiver and digital controller and a data link to transmitthe radar signal to Earth for processing.

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The sensor generates a 1 . 2 7 5 GHz chirp signal at 1,000watts peak power that is radiated to Earth by the radar antenna.The reflected signal is received on the spacecraft where it isamplified by the sensor, converted to 2 . 2 6 5 GHz and transmittedto Earth in analog form by the SAR data link. The signal isdigitized and stored on tape at the tracking station.signal is processed into radar images at Jet PropulsionLaboratory's Radar Imaging Processing Facility.

Because of the high data rate of the radar imagery

The

(equivalent to 110 million bps), the SAR, with its specialground equipment, will operate only within line of sight ofspecific tracking stations equipped to handle the data.Those tracking stations are located at Goldstone, Calif.;Merritt Island, Fla.; and Fairbanks, Alaska. The CanadianGovernment is planning to equip a station at St, John'sNewfoundland.

equipment for a tracking station at Oakhangar in southernEngland.The European Space Agency is purchasing

The Synthetic Aperture Radar weighs 147 kg ( 3 2 4 . 5 lb.)Dr. Paul Teleki of the U . S . Geological Survey, Reston, Va.,

and uses 2 1 6 watts of power.

is team leader.

DATA COLLECTION AND PROCESSINGThe Seasat-A mission data system embraces all project

elements associated with data flow between the satellite andthe experimenter-user community on the ground. (Figure 5)An end-to-end system design approach has been adopted and willbe implemented by a project data system design team.with initial program formulation, NASA will establish proof-of-concept engineering and geophysical validation of Seasat dataand users will provide the resources required for processing,analysis, dissemination and application of data peculiar totheir special interests.

Consistent

The data products of the Seasat sensors must serve avariety of users in a variety of forms.perishable; to be of practical value, operationally, they mustbe processed (e.g., formatted, merged, blended and analyzed)and applied in near real time.are of little interest except for climate studies or modeldevelopment. At the opposite end of the spectrum is thegeodesist, whose data are nearly time invariant. The geodesist'sapproach to analysis is often to fit and refit data by abootstrap approach, finally achieving a best fit model of theocean geoid.

Weather data is highly

Data older than eight hours

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SEASAT-AOCEAN DATA DlSTRl6UTION PLAN

Figure 5I STRUMENT SCIENCE

COMMUNICATIONSSATELLITE

SATELLITE

RATE DATA LINK S

SURFACE TRUTH

S T D N - S P A C E F L IG H T T R A C K I N G AND A T A N E T W O R K

G S F C - G O D D A R D S P A C E F L I G H T C E NT E RF N W C - F LE ET N U M E R I C A L W E A TH E R C E N T R A L USER ANALY S IDATA D ISSEMINATIONECON. VERIFICATION EXPMTS.


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Some of the users will have sizeable ground data systemsavailable to assist them in processing and analysis; otherswill have only inexpensive terminals with limited processingcapability. Some users care only for specific outputs suchas wind and wave data for use in ship routing: others, suchas university researchers, want as much of the data asavailable for application to development of advancedprediction models. Thus Seasat's end-to-end data system,consisting of NASA and user facilities equipment andcommunication networks, must be flexible and dynamic enoughto meet the demands of this broad spectrum of currentlyidentified and future user applications.

Data from the satellite will be returned in threeseparate streams. The real time stream at 25 kilobits persecond and the 800 kbps playback stream from the Seasat taperecorders contain all data except that from the SyntheticAperture Radar (SAR). An analog SAR data stream is obtainedin real time only at specially equipped ground stations --Goldstone, Calif., Fairbanks, Alaska, and Merritt Island,Fla. -- on special wide-band recorders utilizing Seasat-SAR-unique equipment. The data tapes will be forwarded directlyto Jet Propulsion Laboratory, Pasadena, Calif., for processing.

The SAR data processing facility at JPL contains uniqueequipment to correlate the raw radar data recorded at theselected STDN sites and to produce radar images on film.Both processing systems at JPL operate in non-real time,receiving data packages six to 10 days after the data isacquired.Two non-NASA ground stations also will receive SARtelemetry. SAR data received and recorded at a station inNewfoundland will be processed at JPL and at the CanadianCentre for Remote Sensing. The European Space Agency operatesthe other station, located in England.All other spacecraft telemetry data are recorded oneither of two on board recorders, 100 per cent of each orbit.Each of 12 STDN stations throughout the world is equipped toacquire playback (tape recorder dump) data. After acquisition,the data are forwarded to Goddard Space Flight Center, Greenbelt,Md., where the data are pre-processed and forwarded to JPL forfinal processing.Algorithms, needed to convert the data into informationusable by the ocean experimenters, are developed at JPL andapplied internally as well as provided to user organizationsoutside the project.

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- 4 0 -

The tracking station at Fairbanks, Alaska, is committedto provide this same data to the Fleet Numerical WeatherCentral Facility (FNWC) at Monterey, Calif., within threehours after receipt of each playback acquisition. Thesedata will be forwarded from Alaska to FNWC by commercialsatellite link. FNWC desires data less than 6 hours oldand will use these data in providing Seasat data productsto various users (NOAA, Department of Fisheries, CommercialWeather Forecasters, etc.).

In addition to this 3-hour requirement, other STDNstations will be used to attempt to provide global data toFNWC in a 12-hour time period.Real time data, approximately once each orbit, willbe provided to the Seasat Project Operations Control Center(POCC) at Goddard Space Flight Center (by any STDN station)where spacecraft housekeeping data will be extracted and

displayed for use in spacecraft health monitoring andconfiguration control operations.The STDN will also provide tracking support, bothS-band and laser. Orbit computations support will beprovided by the Mission and Data Operations Directorateat Goddard, utilizing these tracking data. The STDNstations are located at: Ascension Island; Santiago,Chile; Bermuda; Goddard; Goldstone; Guam; Hawaii; Madrid,Spain; Orroral, Australia; Merritt Island, Fla.; Quito,Ecuador; and Fairbanks, Alaska. All stations will providetracking, telemetry and command capabilities.Both the Navy and JPL will combine ocean measurementsfrom local sources with Seasat data. The "surface truth"data will be obtained from aircraft, ships and instrumentedbuoys making measurements along the satellite's target path.

The Navy's Fleet Numerical Weather Center (NOAA)will distribute the Navy-processed data. NOAA also willdistribute the non-real time data processed at JPLthrough the Environmental Data Service.

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LAUNCH VEHICLE SYSTEM (LVS)

The Launch Vehicle System (LVS) consists of a modifiedAtlas-F booster, an interstage adapter (ISA), a modifiedfairing and all associated aerospace ground equipment andfacilities. The LVS is 34.6 m (113.5 ft.) overall lengthand 3.05 m (10 ft.) in diameter. The fairing is 10.2 m(32.8 ft.) in length and 3.05 m (10 ft.) in diameter. TheLVS provides the initial boost and guidance to and the aero-dynamic protection f o r , the satellite system. The Agenabus portion of the satellite system provides the injectionstage propulsion and guidance functions. A nominal sequenceof events is provided below in Table 2. The flight vehicleconfiguration is shown in Figure 6.

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MAJOR LAUNCH EVENTS FOR ATLAS F/SEASAT-A MISSIONAltitudeKilometers - MilesEvent Time

Liftoff 0 0 0Roll StartRoll Stop

2.0 sec.15.0 sec.

Booster Engine Cutoff 2 min. 9.5 sec.Booster Engine JettisonStart Guidance Steering

2 min. 12.6 sec.2 min. 27 sec.

Fairing Jettison 3 min. 27.5 sec.Sustainer Engine Cutoff 4 min. 44.4 sec.Start Agena Programmer 4 min. 49.4 sec.Uncage Satellite System Gyros 5 min. 2.4 sec.Vernier Engine Cutoff 5 min. 3.4 sec.Satellite System Separation 5 min. 8.9 sec.Fire Atlas Retro Rockets 5 min. 9.4 sec.Satellite System 900 Roli Start 5 min. 18.4 sec.Satellite System 90 Roll Stop 5 min. 54.4 sec.Agena First BurnFirst Burn ShutdownAgena Second BurnSecond Burn Shutdown

6 min. 23.4 sec.10 min. 14.5 sec.57 min. 28.4 sec.57 min. 34.6 sec.

45.7

122.4173.5

185.2

790.2

28.4

76.0107.8

115.3

491.0-more-


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SEASAT-A MISSION FLIGHT COMPENDIUM

5. 5 SEC--?T L A S VEWER PIIASEt , 4 0 0 LE THRUST__ ~--flczE~ -VLCO Iv ) VLiwrfnENGINE CUTOFFAT+30S 5 NOMHAL )

COMMAND GUIDANCE DlSCWlT(S+lqBACWR ATLAS p n o c n a u m 1119 1)(CUD I U T U 1 2 1

RANGE SAFZTY COMMAND UN K(V*o ZIMAIN FUEL CUTOFT)PACE POSITION

LHKBACKUP RANGE SAFETY COMMA'D

P n o m u m DWLETICUPSS wnisrr szco+z SICPSI m m r r BACKUP SECO+~ECSTART ACENA T lMlNC S E C0 6 S ECSTART AGENA T lMlNG B IU ICO+ 6 S UUNCACE SV GYROS SECO+IO SI CUNCAGE SV GYROSB/U - SECOtII) 5 SEC

smcIwsIncuM C U I P ATLAS?Iux;I IAMMER T 4 3 0

8&-". IWAMTIOH V t 5 . S

COMMAND: GUIDANQ (V+S.5BACKUh PROCPAMLQR (V+FIRE RCTIIOROCUTS (VI()Tm E RCTIIOROCKLTS BI U (VI()


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T R A J E C T O R Y P R O F I L E F O R T H E A T L A S F I S E A S A T - A M I S S I O NFAIRING .

LIFT-OFF

AGENA ,/90' ROLLFOR 1 S T BURN \?*

BI R S T BURNTHRUST VECTORCONTROL \COAST '\GYROCOMPASS

DUMP PROPELLANTDURING 1/3 ORBIT

/JCONTROL

2N D BURN THRUSTVECTOR CONTROLORIENT AGENAFOR 2 N D BURN


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34

-45-F l i q h t V e h i c l e C o n f i g ur a t io n

LMSC -52.54

M

12 4 FA I R I NG

LMSC 247.0

SATELLITE MATING PLANELMSC 384 O

FAIR ING SEPARATION PLANELMSC 442.44L M S C U 7 . 0 JO~N~LMSC466.0 FIELD

FIELD

GDC 488.5 -TOI NT GD CA-- DC INTERSTAGE ADAPTERLMSC 547.5GDC 570.0

MOD IFIED ATLAS-F/-OOSTER

b DC 1309.98F i g u r e 6

. .


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- 4 6 -

SEASAT-A EXPERIMENT TEAMS

Science Steering GroupJames A. Dunne, ChairmanJohn R. Ape1

Jet Propulsion LaboratoryPacific Marine EnvironmentalLaboratory, NOAA

H. Michael Byrne

Duncan B. Ross

E. Paul McClain

John W. Sherman I11

John Wilkerson

Samuel L. Smith I11Vince E. NobleBenjamin Yaplee

Paul G. TelekiWillard PiersonRobert Stewart

Byron D. TapleyRene 0. Ramseier

Pacific Marine EnvironmentalLaboratory, NOAA (alternate)Atlantic Oceanographic andMeteorologic Laboratory, N O MNational EnvironmentalSatellite Service, N O MNational EnvironmentalSatellite Service, NOAANational EnvironmentalSatellite Service (alternate)Naval Surface Weapons CenterNaval Research LaboratoryNaval Research Laboratory(alternate)U.S. Geological SurveyCity University of New YorkScripps Institution ofOceanographyUniversity of TexasCanadian Department ofthe Environment

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Radar AltimeterByron D. Tapley, Team LeaderCraig L. PurdyH. Michael Byrne

J. M. DiamanteBernard H. Chovitz

Bruce DouglasPat LeDeonibus

Leonard Fedor

Joseph T. McGooganGeorge H. BornWilliam Fred TownsendHamilton HagarSamuel L. Smith I11Jack LorellCharles J. CohenJoseph N. SiryBenjamin YapleeDavid E. SmithE. M. Gaposchkin

F. 0. VonbunH. Jay ZwallyR. J. Anderle

University of TexasWallops Flight CenterPacific Marine EnvironmentalLaboratory, NOAANaval Oceanographic ServiceNaval Oceanographic Service,

Naval Oceanographic ServiceEnvironmental Monitoring

NOAA

and Prediction, NOAAEnvironmental ResearchLaboratory, NOAAWallops Flight CenterJet Propulsion LaboratoryWallops Flight CenterJet Propulsion LaboratoryNaval Surface Weapons CenterJet Propulsion LaboratoryNaval Surface Weapons CenterGoddard Space Flight CenterNaval Research LaboratoryGoddard Space Flight CenterSmithsonian AstrophysicalObservatoryGoddard Space Flight CenterGoddard Space Flight CenterNaval Surface Weapons Center

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- 4 8 -

Synthetic Aperture RadarPaul G. Teleki, Team LeaderClifford L. Rufenach

Duncan B . Ross

John W. Sherman 111

Frank T. BarathOmar ShemdinPaul E. LaViolette

Kumar KrishenRobert Beale

William J. CampbellBruce BlanchardRichard M. HayesRobert Shuchman

Robert Stewart

Rene 0. Ramseier

Frank Gonzales

Walter E. Brown, Jr.

U.S. Geological SurveyWave Propagation Laboratory,NOAAAtlantic Oceanographic andMeteorologic Laboratory, NOAANational EnvironmentalSatellite Service, NOAAJet Propulsion LaboratoryJet Propulsion LaboratoryNaval Ocean Research andDevelopment ActivityJohnson Space CenterJohns Hopkins UniversityApplied Physics LaboratoryU.S. Geological SurveyTexas A & M UniversityU.S. Coast GuardEnvironmental ResearchInstitute of MichiganScripps Institution ofOceanographyCanadian Department ofthe EnvironmentPacific Marine EnvironmentalLaboratory, NOAAJet Propulsion Laboratory

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Radar ScatterometerWillard Pierson, Team Leader City University of New YorkLedolph Baer Environmental Monitoring and

Prediction, NOAAGlenn Flittner National Weather ServicePeter G. Black National Oceanic andAtmospheric AdministrationIsidore Halberstam Jet Propulsion LaboratoryW. Linwood Jones Langley Research CenterRichard K. Morre University of KansasJack Ernst National EnvironmentalSatellite ServiceW. L. Grantham Langley Research Center

Visual and Infrared RadiometerE. Paul McClain, Team Leader National EnvironmentalSatellite ServiceAndrew W. McCulloch Goddard Space Flight CenterOscar C. Huh

Robert L. Bernstein

Coastal Studies Institute,University of Louisiana -Scripps Institution ofOceanography

Fred Vukovich Research Triangle Institute

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Scanning Multifrequency Microwave RadiometerDuncan B. ROSS, Team Leader Atlantic Oceanographic andMeteorologic LaboratoryJohn W. Sherman I11 National EnvironmentalSatellite Service, NOAAFrank T. Barath Jet Propulsion LaboratoryEni Njoku Jet Propulsion LaboratoryJoseph M. Stacey Jet Propulsion LaboratoryJ. W. Waters J e t P r o p u l s i o n L a b o r a t o r yPer Gloerson Goddard Space Flight CenterThomas T. Wilheit, Jr. Goddard Space Flight CenterCalvin T. Swift Langley Research CenterNorden E. Huang Wallops Flight CenterJames P. Hollinger Naval Research LaboratoryWilliam J. Campbell U.S. Geological SurveyVincent J. Cardone City University of New YorkJohn C. Alishouse National EnvironmentalSatellite Service

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SEASAT-A MISSION TEAM

NASA HeadquartersDr. Anthony J. Calio

Dr. Lawrence R. Greenwood

S. Walter McCandless, Jr.Norman Pozinsky

John F. YardleyJoseph B. Mahon

Jet Propulsion LaboratoryDr. Bruce C. MurrayRobert J. Parks

Walker E. GibersonDr. James A . DunneJohn H. GerpheideEdwin PounderAnthony J. SpearCharles A. YamaroneRichard T. HayesWillis G. Meeks

Associate Administrator forSpace and TerrestrialApplicationsDirector of EnvironmentalObservations SystemsProgram ManagerActing Associate Administratorfor Space Tracking and DataSystems

Associate Administrator forSpace Transportation SystemsDirector, Expendable LaunchVehicles

DirectorAssistant Director forFlight ProjectsProject ManagerOcean Experiments ManagerSatellite System ManagerMission Engineering ManagerSensors ManagerInformation Processing ManagerProject Operations ManagerChief of Mission Operations

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-52-G od dard S p a c e F l i g h t C e n t e rD r . R o b e r t S. CooperA l b e r t G . F e r r i s

John B . Z e g a l i a

L ew i s Resea rch C e n t e rD r . Bernard LubarskyS t e v e n V. Szabo, J r .

DirectorD i r ec to r , Mission andD a t a O p e r a t i o n sMission Suppor t Manager

A c t i n g D i r e c t o rC h i e f , Seasa t LaunchV e h i c l e O f f i c e

N a t i o n a l Oceanic and Atmospher ic A d m i n i s t r a t i o nJohn W. Sherman I11 NOAA P r o j e c t ManagerD r . John R . Ape1 D i r e c t o r , NOAA P a c i f i cMarine Environmental L a b o r a t o r y

Depar tment of DefenseCap t . Ha r ry L. B ix by, USN DOD Program Coord ina to rCap t . Ron E. Hughes, USN Commanding O f f i c e r , F l e e tNumerical W e a t h e r C e n t r a lD r . Vinc e n t Noble

D r . C h a r l e s M a r t in

D e pa rtm e nt o f T r a n s p o r t a t i o nR i c h a r d Hayes

C o o r d i n a t o r , Naval Resea rchL a b o r a t o r yCo ord ina to r , De fense MappingAgency

C o o r d i n a t o r , U .S . Coas tGuard ProgramsLockheed Missiles & Space Co.John C . S o lv aso n LMSC Pro gra m Manager

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-53-SEASAT-A CONTRACTORS

SatelliteLockheed Missiles & SpaceSunnyvale, Calif.Co., Inc.Ball Brothers Research Corp.Aerospace DivisionBoulder, Colo.Bell Aerospace, TextronBuffalo, N.Y.Hamilton Standard DivisionUnited Technologies Corp.Windsor Locks, Conn.Ithaco, Inc.Ithaca, N.Y.Motorola, Inc.Scottsdale, Ariz.Odetics, Inc.Anaheim, Calif.Pressure Systems, Inc.Los Angeles, Calif.Schaeffer Magnetics, Inc.Chatsworth, Calif.

Sensor SvstemsAeroj t General Corp.El Monte, Calif.Andersen Labs, Inc.Bloomfield, Conn.Applied Physics LaboratoryJohns Hopkins UniversityLaurel, Md.

Satellite System (bus andsensor modules): ProjectOperations SupportSAR Antenna

Rocket Engine

Thrusters

Orbital Attitude Control

Radio Transponder

Tape Recorders

Hydrazine Tanks

Solar Array Drives

SASS Antenna

ALT Radar Pulse Modulator

ALT RF and Sensor Integrationand Test,

seasat-a press kit

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