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Comparison Of Noise Models And Resolution Capabilities For Satellite Radar Altimeters

Satellite radar altimeters measure sea surface topography along the satellite subtrack using reflected radar pulses. Error sources that interfere with the recovery of instantaneous sea surface height relative to the earth’s ellipsoid include those from the environment (e.g., atmospheric propagation delays), plus the bias and random electronic noise in the altimeter instrument itself The focus of this paper is on the description and quantification of the noise due to the altimeter instrument and on the relative capabilities of different altimeter missions to resolve shortwavelength geoid features. We have applied consistent definitions and techniques to develop noise models for four different satellite altimeter missions: GEOS-3, Seasat, Gcosat, and ERS-1. As the measurement technology has advanced, altimeter noise levels have decreased, and shortwavelength resolution limits have improved. The altimeter noise models derived in this work are necessary for geodetic collocation analyses and optimal least-squares interpolation. They are also valuable for preprocessing altimeter data for oceanographic analyses, and for choosing parameters for classical filter design (e.g., high frequency limits and roll-off rates).