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The GEOS 2 (Geodetic Earth Orbiting Satellite) was a gravity-gradient-stabilized, solar-cell-powered spacecraft that carried electronic and geodetic instrumentation. The geodetic instrumentation systems included (1) four optical beacons, (2) two C-band radar transponders, (3) a passive radar reflector, (4) a sequential collation of range radio range transponder, (5) a Goddard range and range rate transponder, (6) laser reflectors, and (7) Doppler beacons. Non-geodetic systems included a laser detector and a Minitrack interferometer beacon. The objectives of the spacecraft were to optimize optical station visibility periods and to provide complementary data for inclination-dependent terms established by the Explorer 29 (GEOS 1) gravimetric studies. The spacecraft was placed into a retrograde orbit to accomplish these objectives. Operational problems occurred in the main power system, optical beacon flash system, and the spacecraft clock, and adjustments in scheduling resulted in nominal operations.

Alternate Names

  • Explorer 36
  • GEOS-B
  • 03093

Facts in Brief

Launch Date: 1968-01-11
Launch Vehicle: Delta
Launch Site: Vandenberg AFB, United States
Mass: 469.0 kg

Funding Agency

  • NASA-Office of Space Science (United States)


  • Earth Science
  • Space Physics

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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