The Geodetic and Earth Ocean Satellite 3 (GEOS-3) was part of a geodetic mission series lead by NASA. It launched April 9, 1975 and continued operating until July 1979. GEOS-3 mission was to measure the gravitational field around the Earth, specifically to identify the irregularities and anomalies. Gravitational anomalies over the ocean also can be used to measure large mesoscale circulation.
Two C-band antenna – Used to experiment what the accuracies would be for gravimetric and geometric measurements.
S-band tracking system – It consisted of an ATS and Earth viewing antennae, diplexer and transponder. The transponder operated in three modes: satellite to satellite tracking, direct unified S-band and Goddard Range and Range Rate ground-station tracking.
Radar altimeter – Ku band altimeter, it was the first altimeter to measure sea surface height
Doppler beacon – Dual frequency, 162 and 324 MHz, Doppler used to measure ionosphere.
Retroreflector array – Used to calculate the orbit by using ground laser ranging.
Orbit: Non-sun synchronous
Launch Date: 9 April 1975
Inclination: 115 degrees
Perigee: 824 km
Apogee: 856 km
Period: 102 minutes
Weight: 346 kg
Period: 101.82 minutes
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