Reference frame

The earth's reference frame and the dynamic models are chosen according to the IERS standard [McCarthy, 1989] as much as possible. These standards pertain to a variety of model parameters and constants applied in modern orbit computation techniques.

In the following Sections some results of the precise orbit determination for Cycle 9 of ERS-1's 35-day repeat mission (19 January till 24 February 1993) are presented. This period is covered by arcs 160-169 of the operational orbit determination. The quality of these orbits will be assessed by means of various statistical analyses of SLR residuals, altimeter height residuals, crossover height differences, and orbital overlaps. Also, a comparison is made with the German ERS-1 Processing and Archiving Facility (D-PAF) PRC-01 orbit provided on the version 3.0 release of the ERS-1 OPR02 ocean product. This orbit is generated with a new gravity model (PGM035, an updated version of GRIM4-S3) using full-rate SLR normal points and altimeter crossovers as tracking data [Massmann et al., 1993; Massmann et al., 1994].