Within battery power constraints, altimeter data can be taken whenever the satellite is within view of a telemetry site, with data always transmitted in near real time. No storage of data is possible on board the spacecraft, although some averaging of data prior to transmission is possible. In addition transmision may also be via an S-band link through ATS-6, so that more than half a revolution of continuous visibility of GEOS-3 is possible for those missions for which ATS-6 is scheduled.
The major calibrations considered necessary for the built-in test/calibration system were time delay (bias), AGC/gain, and waveform calibration. Internally generated signals are provided for calibration. A 10-second time delay (bias) test is performed in each mode to determine the bias to within the required one meter. In each mode, a two-point AGC/gain calibration is obtained using IF reference pulses. For waveform calibration, controlled video waveforms are used in both modes. [Hofmeister et al., 1976]
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Hofmeister, E.L., B.N. Keeney, T.W. Godbey, and R.J. Berg, 1976. Data User's Handbook and Design Error Analysis: GEOS-3 Radar Altimeter Volume I, NASA CR-156870, National Aeronautics and Space Administration, 540 pp.
Leitao, C.D., N.E. Huang, and C.G. Parra, 1978. Remote Sensing of Gulf Stream Using GEOS-3 Radar Altimeter, NASA Technical Paper 1209, National Aeronautics and Space Administration, 31 pp.
Martin, C.F., 1977. Altimeter Error Sources at the 10-cm Permormance Level, NASA CR-141420, National Aeronautics and Space Administration, 63 pp.
Martin, C.F. and M.L. Butler, 1977. Calibration Results for the GEOS-3 Altimeter, NASA CR-141430, National Aeronautics and Space Administration, 119 pp.
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