Explorer 36 (GEOS 2)

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 four optical beacons, two C-band radar transponders, a passive radar reflector, a sequential collation of range radio range transponder, a Goddard range and range rate transponder, laser reflectors, and 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.