Accuracy assessment and refinement of the JGM-2 and JGM-3 gravity fields for radial positioning of ERS-1

ERS-1 radial positioning using the JGM-2 and JGM-3 gravity fields is assessed by analysing dual crossovers with TOPEX/Poseidon, neither field containing ERS-1 data. This method allows a more complete recovery of ERS-1 radial orbit error, specifically of the previously unattainable mean geographical error. The global analysis shows that the theoretical error derived from the JGM-2 covariance matrix is realistic and that JGM-3 represents a slight improvement, at least at the inclination of ERS-1. A latitudinal-based study in the southern ocean indicates possible weaknesses in both fields, notably for low and resonant geopotential orders m. A refinement of JGM-2, RGM-2, is undertaken through inclusion of ERS-1 and STELLA laser tracking and ERS-1 altimetry, reducing several of its deficiencies. Received: 14 May 1996 / Accepted: 17 February 1997