Initial results from retracking and reprocessing the ERS-1 geodetic mission altimetry for gravity field purposes

All present global marine gravity fields are based on the lHz ERS-1 Geodetic Mission (GM) altimeter data combined with other altimetric datasets. Close to the coast (<25 km) this investigation shows that the altimetric gravity field determination degrades due to a combination of several factors, where the main reason is the degradation of the quality of the altimeter data.

By starting out from the original waveform data and retracking the entire ERS-1 GM mission using a highly advanced expert based system of multiple retrackers, the return time from both open ocean and coastal sea surface as well as from all ice-covered regions within the coverage of the ERS-1 can be derived with higher accuracy than presently available.

Initial results of the combined effort to improve the ERS-1 GM altimetric dataset through retracking and regression to 2Hz (3km) are presented, and its effort on gravity field modeling close to the coast and in Polar Regions is discussed. Close to the coast and in particular in Polar Regions the use of multiple retrackers leads to considerably more and better data than in the normal 1 Hz data delivered by the European Space Agency (ESA).

Extensive comparison with marine gravity field data by the National Geospatial-Intelligence Agency is also presented to document the improvement on gravity field determination