Computation of precise GLONASS orbits for IGEX-98

Abstract

On October 19, 1998, at the beginning of the International GLONASS Experiment (IGEX-98), the Center for Orbit Determination in Europe (CODE) has started to compute precise orbits for all active GLONASS satellites. The campaign was initially scheduled for three months, but the activities still continue in September, 1999. One of the main reasons for this extension was the launch of three new GLONASS satellites at the end of the year 1998.

The processing of the ILEX network is done on a routine basis at CODE and precise eghemerides are made available through the global ILEX Data Centers. The improved GLONASS orbits are referred to the Interna, tional terrestrial Reference System (ITRF96) and to GPS system time. They are therefore fully compatible with GPS orbits and allow a combined processing of both satellite systems.

All GLONASS satellites are equipped with a laser reflector array and the SLR ground network is tracking most of the GLONASS satellites. Comparisons of the GLONASS orbits computed by CODE with the SLR measurements show that the orbit accuracy is better than 20 cm.