Conclusions

The ERS-1 orbits for Cycle 9 of the 35-day repeat mission, that have been computed by DUT/SSR&T, have an estimated accuracy of 13 cm, even though they are based on only few SLR tracking data available during this period. This number includes an estimate for the geographically correlated orbit error. Especially the RMS height differences of crossovers consisting of passes with a time interval less than 2 days, is a helpful tool for the determination of the actual radial orbit error, since the short time interval excludes many contributions to the crossover RMS other than orbit errors.