The GEOS 3 (Geodynamics and Earth Ocean Satellite) spacecraft was launched on April 9, 1975. The spacecraft carried a radar altimeter for mapping of the oceans, as well as a laser retroflector, and other tracking beacons. Altimeter data from GEOS-3 became part of the GEM-T3, JGM-1 and JGM-2 gravity models. In addition SLR (satellite laser ranging) data to GEOS-3, as well as satellite-to-satellite Doppler tracking data from the geostationary satellite ATS-6 were also included in these models. During the development of the prelaunch TOPEX gravity models, GEOS-3 was considered to be an important satellite, since it was located near the mirror inclination of TOPEX/POSEIDON (66.6 deg).

EGM96 included GEOS-3 SLR data, as well as combined SLR and satellite-to-satellite tracking data from ATS-6.

Orbit Data for GEOS-3

Eccentricity: 0.00115
Inclination: 115 degrees.
Perigee Height: 840 km
Apogee Height: 860 km
Area: 1.4365 meters**2
Mass: 345.909 kg
Orbital Period: 102 minutes
Period of the Argument of Perigee: 1039 days
Year of Launch: 1975

References for more information on GEOS-3

Kahn, W. D., S. M. Klosko, and W. T. Wells, "Mean gravity anomalies from a combination of Apollo/ATS 6 and GEOS-3/ATS 6 SST tracking campaigns," J. Geophys. Res., 87, 2904-2918, 1982.

Lerch, F. J., Klosko, S. M., Laubscher, R. E., Wagner, C. A., "Gravity Model Improvement Using GEOS-3 (GEM-9 and 10)", J. Geophys. Res., 84(138), 3897-3915, 1979.

Rapp, R. H., "Gravity anomalies and sea surface heights derived from a combined GEOS 3/Seasat altimeter data set," J. Geophys. Res., 91, 4867-4876, 1986

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Last revised January 17, 2006.