https://cdn.earthdata.nasa.gov/conduit/upload/5182/KeywordsCommunityGuide_Baseline_v1_SIGNED_FINAL.pdf 24.4 2026-07-22T11:07:16.739Z https://gcmd.earthdata.nasa.gov/KeywordViewer/scheme/platforms/053da8e9-78d7-4d7f-997a-d06773323b7e GEOSAT - Spacecraft Brief Description -The GEOdetic SATellite (GEOSAT) was a dedicated US Navy military oceanographicsatellite consisting of a radar altimeter designed to obtain closely spaced,precise mapping of the earth's geoid over the ocean. On November 8, 1986, thesatellite was moved into an Exact Repeat Mission (ERM) orbit with a repeatcycle of 17.05 days. The GEOSAT mission was originally managed by the Office ofNaval Research (ONR). During the development phase, the program responsibilitywas transferred to the Naval Electronics Systems Command, now called the Spaceand Naval Warfare Systems Command (SPAWAR) in Washington, D.C. The AppliedPhysics Laboratory (APL) was the prime contractor for the spacecraft and radaraltimeter and performed spacecraft command and control operations and collectedthe satellite data. The data was distributed to the Naval Surface WeaponsCenter (NSWC), the Naval Ocean Research and Development Activity (NORDA), andNOAA. An arrangement was made with the National Ocean Service of NOAA to obtainthe classified GEOSAT geophysical data records (GDR) providing wind, wave andsea-level products and made available to the user community. NASA obtainedGEOSAT data for extensive waveform modeling and ice sheet research.The basicstructure of the GEOSAT is similar to the GEOS-3 satellite: The design consistsof a conical structure below the core for the structural attachment of thevelocity control system. The GEOSAT attitude control subsystem was designed topoint the radar altimeter to within 1 degree of nadir 98 percent of the time.The system components were a 20-foot scissors boom with 100-pound end mass,redundant momentum wheels for roll and yaw stiffness, and pitch and rollattitude control thrusters. Attitude sensing was provided through the use ofthree digital sun-attitude detectors and a three-axis vector magnetometer.Spacecraft command was accomplished via a VHF uplink from the APL groundstation. The telemetry subsystem consisted of two S-band transmitters, two taperecorders, and two encryption units. The GEOSAT was equipped with two Odeticsdual-track high-density tape recorders that independently recorded the 10.205kbps telemetry stream and played it back at 833 kbps for transmission to theground. The GEOSAT also included redundant Doppler beacons for continuoustracking by a network of ground stations within the Defense Mapping Agency(DMA) and for a source of accurate timing to the radar altimeter and thetelemetry subsystem. A C-band transponder was also included on GEOSAT. SeeJensen,J.J. and F.R.Wooldridge, 'The Navy GEOSAT Mission: An Introduction';McConathy, D.R. and C.C.Kilgus, 'The Navy GEOSAT Mission: An Overview', andFrain,W.E., M.H.Barbagallo, and R.J.Harvey,'The Design and Operation ofGEOSAT', all in Johns Hopkins APL Technical Digest, Volume 8, Number 2 (1987). - Auxiliary Information - Launch Date and Time : 1985-03-12 Epoch Date and Time : Apogee (km or AU): 814. Perigee (km or AU): 757. Inclination (degree) : 108.1 Orbit Type : Information last updated on 1992-05-20Group: Platform_Details Entry_ID: GEOSAT Group: Platform_Identification Platform_Category: Earth Observation Satellites Platform_Series_or_Entity: GEOSAT Short_Name: GEOSAT Long_Name: Geodetic Satellite End_Group Group: Synonymous_Platform_Names Short_Name: GEOSAT End_Group Group: Platform_Associated_Instruments Short_Name: RADAR ALTIMETERS End_Group Group: Orbit Repeat_Cycle: 17 DAYS End_Group Creation_Date: 2007-09-26 Online_Resource: http://msl.jpl.nasa.gov/QuickLooks/geosatQL.html Online_Resource: http://leonardo.jpl.nasa.gov/msl/QuickLooks/geosatQL.html Online_Resource: http://nasascience.nasa.gov/missions/geosat Sample_Image: http://msl.jpl.nasa.gov/QuickLooks/pictures/geosat.gif Group: Platform_Logistics Launch_Date: 1985-03-13 Primary_Sponsor: USA/NASA Primary_Sponsor: United State Department of Defense End_GroupEnd_Group