GEOS 3 altimeter performance

GEOS 3 (Geodynamics Experimental Ocean Satellite) is the first satellite launched in the NASA Earth and Ocean Physics Applications Program and is designed to perform both geodetic and oceanographic missions. Aboard GEOS 3 is a radar altimeter for measuring the ocean surface characteristics and the spacecraft to ocean surface distance. Frequency of operation is 13.9 GHz, with two modes of operation - global or long pulse (200 nsec) mode, and intensive or short pulse (12 nsec) pulse mode. The discussion covers spacecraft and instrumentation, mission objectives, spacecraft performance, and altimeter data characteristics. Although the altimeter operation is planned only over water, the checkout of the altimeter system demonstrated that the global mode is capable of operating over land for which the terrain is not too mountainous. Sample altimeter sea surface and waveform measurements are presented.