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GEOS-3The GEOS 3 (Geodynamics and Earth Ocean Satellite) was part of a geodetic mission series lead by NASA.  It launched on 9 April 1975 and continued operating until July 1979. The spacecraft carried a radar altimeter for mapping of the oceans, as well as a laser retroflector, and other tracking beacons.
The 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. 
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.

  • 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.
  • Chapman, M.E. and Talwani, M., "Comparison of Gravimetric Geoids with GEOS-3 Altimetric Geoid", J. Geophys. Res., Vol. 84, pp. 3803-3816, 1979.
  • Eren, K., "Spectral Analysis of GEOS-3 Altimeter Data and Frequency Domain Collocation", OSU-Rpt. 297, 151pp, 1980.
  • 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.
  • Klosko, S.M., Lerch, F.J., Belott R.P., and Litkowski, E.M., "Laser Reference Orbits and Altimeter Validation for GEOS-3", Marine Geodesy Symposium, RSMAS, U. Miami, 1978.
  • Lemoine, F.G., "The 1998 to 1999 GEOS-3 Tracking Campaign: Analysis and Results", NASA Tech. Rept., NASA Goddard Space Flight, Jan 01, 1999.
  • Lerch, F.J., Klosko, S.M., Laubscher, R.E., and Wagner, C.A., "Gravity Model Improvement Using GEOS-3 (GEM 9 and 10)", NASA Doc. No. X-921-77-246, 121pp, 1977.
  • Lerch, F.J., Klosko, S.M., Laubscher, R.E., and Wagner, C.A., "Gravity Model Improvement Using GEOS-3 (GEM-9 and 10)", NASA X-921-77-246, September, 1977.
  • 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.
  • Marsh, J.G., Marsh, B., Conrad, T., Wells, W., and Williamson, R., "Gravity Anomalies Near the East Pacific Rise with Wavelengths Shorter than 3300 km Recovered from GEOS-3, ATS-6, Satellite-to-Satellite Doppler Tracking Data", The Use of Artificial Satellites for Geodesy and Geodynamics, pp. 296-342, 1979.
  • Marsh, J.G., Martin, T., McCarthy, J.J., and Chovitz, P., "Estimation of Mean Sea Surfaces in the North Atlantic, the Pacific, and the Indian Ocean Using GEOS-3 Altimetry Data", The Use of Artificial Satellites for Geodesy and Geodynamics, pp. 414-447, 1979.
  • Marsh, J.G., Koblinsky, C.J., Zwally, H.J., Brenner, A.C., and Beckley, B.D., "A Global Mean Sea Surface Based Upon GEOS-3 and SEASAT Altimeter Data", J. Geophys. Res., in press, 1992.
  • Mather, R., Lerch, F.J., Rizos, C., Masters, E., and Hirsch, B.,"Dynamic Sea Surface Topography from GEOS-3 Altimetry: Determination of Some Dominant Parameters", The Use of Artificial Satellites for Geodesy and Geodynamics, pp. 448-477, 1979.
  • Mather, R.S., Lerch, F.J., Rizos, C., Masters, E.G., and Hirsch, B., "Determination of Some Dominant Parameters of Global Dynamic Sea Surface Topography from GEOS-3 Altimetry", - NASA TM-79558, 40pp, 1978.
  • 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.
  • Schutz, B.E., Tapley, B.D., Ries, J.C., and Eanes, R.J., "Polar Motion Results From GEOS-3 Laser Ranging", J. Geophys. Res., 84(B8), July 30, 1979.