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The GEOS 3 (Geodynamics Experimental Ocean Satellite) spacecraft was an octahedron, topped by a truncated pyramid, with a parabolic reflector for a radar altimeter on the flat bottom side. A metal ribbon boom with end mass extended upward approximately 6.1 m from the top of the pyramid. Passive laser retroreflector cubes were mounted in a ring around the parabolic reflector with the normal vector from each cube facing 45 deg outward from the direction of the earth. A turnstile antenna for VHF and UHF frequencies and separate antennae for earth-viewing 324-MHz Doppler, C-band, and S-band transponders were mounted separately on flat surfaces next to the parabolic reflector. The dimension across the flats of the octahedron was 1.22 m, and the spacecraft was 1.11 m high. The mission provided the stepping stone between the National Geodetic Satellite Program (NGSP) and the Earth and Ocean Physics Application Program. It provided data to refine the geodetic and geophysical results of the NGSP and served as a test for new systems. Mission objectives were to perform a satellite altimetry experiment in orbit, to support further the calibration and position determination of NASA and other agency C-band radar systems, and to perform a satellite-to-satellite tracking experiment with the ATS 6 spacecraft using an S-band transponder system. This system was also used for periodic GEOS 3 telemetry data relay through ATS 6, to support further the intercomparison of tracking systems, to investigate the solid-earth dynamic phenomena through precision laser tracking, to refine further orbit determination techniques and determine interdatum ties and gravity models, and to support the calibration and position determination of NASA Spaceflight Tracking and Data Network (STDN) S-band tracking stations. For more details, see special reports on the GEOS 3 in J. Geophys. Res., v. 84, n. B8, 1979.

Alternate Names

  • Geodetic Explorer Sat.
  • GEOS-C
  • 07734

Facts in Brief

Launch Date: 1975-04-09
Launch Vehicle: Delta
Launch Site: Vandenberg AFB, United States
Mass: 340.0 kg

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Engineering
  • Earth Science

Additional Information

Questions or comments about this spacecraft can be directed to: Coordinated Request and User Support Office.



NameRoleOriginal AffiliationE-mail
Mr. Charles J. FinleyProgram ManagerNASA Headquarters 
Mr. Hubert R. StanleyProject ScientistNASA Wallops Flight
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