The precise satellite ephemerides for the ERS-1 and ERS-2 missions have been computed at the Delft Institute for Earth-oriented Space Research (DEOS), Delft University of Technology. The computations used the DGM-E04 gravity field model (see Scharroo et al., 1997). The DGM-E04 is a tuning of the JGM-3 model (Tapley et al., 1996) especially for handling ERS-1 and ERS-2. The tracking data on ERS-1 consists of satellite laser ranging only.
The current radial orbit accuracy estimate for the Phase C orbits (eighteen 35-day repeat cycles) is approximately 6-8 cm rms (1-sigma), including an estimate for geographically correlated orbit errors due to gravity. The average ERS-1 altimeter crossover residual rms is about 10 cm. For further information on these computed ephemerides, including a preprint of the paper by Scharroo et al., see the ERS Precise Orbit Determination pages at Delft.
REFERENCES:
Scharroo, R, P Visser, and G Mets, ``TOPEX-class orbits for the ERS satellites,'' submitted for publication in J. Geophys. Res., 1997.
Tapley, B, M Watkins, J Ries, G Davis, R Eanes, S Poole, H Rim, B Schutz, C K Shum, R S Nerem, F Lerch, J A Marshall, S Klosko, N Pavlis, R Williamson, ``The Joint Gravity Model 3,'' J. Geophys. Res., 101, 28029-28049, 1996.
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