CROSS ANALYSIS OF TOPEX/POSEIDON AND ERS-1 DATA IN THE MEDITERRANEAN SEA

P. Bonnefond, P. Exertier

Observatoire de la Cote d Azur, CERGA/GRGS, Av. Copernic, F-06130 Grasse

Abstract. A short-arc orbit determination technique, which was developed and applied to TOPEX/Poseidon satellite (T/P) before (Bonnefond et al., 1994), has been applied to ERS-1 satellite over the Mediterranean area for a period of time of 6 months (corresponding to five 35-day repeat cycles). Due to a lack of SLR measurements during this period, a few orbital short-arcs have been improved by this technique solely. The results show a bias of - 42. +/- 7 cm when comparing to T/P mean sea profiles serving as reference, which is in good agreement with the ERS-1 altimeter bias.
The improvement of ERS-1 orbits has been extended to all the Mediterranean short-arcs using a cross-over method. The results show the level of consistency which is possible to reach between T/P (our reference) and ERS-1 data with this method (6 cm rms). However, the sea level differences at ERS-1/ERS-1 cross-over points serving as a control of these orbit improvements are at the level of 8 cm rms giving thus the level of precision. Finally, this cross-analysis provides an accurate and detailed mean sea surface, T/P data contributing to its accuracy while ERS-1 data in its space resolution.