ERS-1 Orbits: The Routine Operation and High Precision Products

The objective of the paper is to summarise the experience of one year of orbit determination and prediction for the ERS-1 spacecraft: firstly, the results of the operational solutions based on S-band ranging and doppler plus fast delivery altimetry will be discussed, and subsequently, higher precision solutions using data from the global laser ranging network. Steady progress has been achieved in improving the latter, in particular through better solutions for station positions, drag, gravity and tides. The development of this offline capability has strengthened considerably the routine orbit determination, and gives high confidence that the requirements for the latter are being satisfied. The paper attempts to quantify the accuracies which have been reached in the European Space Operations Center solutions, and to answer the question: how far are we still from achieving 10 cm radial accuracy for altimeter satellites at 800 km?