COMPARISON OF GRAVITY FIELD MODELLING FOR ERS-1 USING DUAL CROSSOVER CONSTRAINT EQUATIONS

Abstract

Dual crossovers between TOPEX/Poseidon and ERS-1 provide a measure of the radial accuracy of ERS-1 relative to the more precise TOPEX/Poseidon orbits. In particular harmonic analysis of the residuals from narrow latitudinal bands yields the amplitude and phase of radial orbit error at specific orders in the Earth's gravity field. The procedure results in lumped harmonics of given orders which can be used either to refine a gravity field or to assess its accuracy. In this study the lumped harmonics will be employed to compare gravity fields in common use for ERS-1 and ERS-2 orbit determinations. Results will be presented from both the 35- and 168-day repeat cycles of ERS-1.