GLONASS Data Analysis for IGS

The Federal Agency for Cartography and Geodesy analyses combined GPS/GLONASS data of a global network of observing stations since the beginning of the IGEX experiment in 1998. Significant milestones in the geometry of the tracking network, development of GLONASS receivers, constellation of GLONASS satellites and improvements of the analysis strategy became visible during that period of 6 years. The weekly analysis products include precise GLONASS satellite orbits, station coordinates, transformation parameters between PZ-90 and ITRF and the difference of the GPSand GLONASS system time. The system time differences could be compared to the results of other analysis centres, e.g. ESA, and to the publications of the BIPM. The precise knowledge of such numbers is a prerequisite for a complete combination of GNSS systems (GPS, GLONASS or GALILEO), e.g., if the analysis procedure solves for phase ambiguities between satellites of different systems. Recent results are not precise enough for the latter application. In our approach we solve for GLONASS satellite orbits but use orbits from IGS for the GPS satellites. We have demonstrated, that we could use the IGS rapid orbits in our analysis without significant impact on our products. This allows to submit our weekly GLONASS orbits before the generation of the IGS final orbits. We plan to continue with the analysis of GLONASS data, to expand our products by satellite clock estimates and to observe the possibility to add GALILEO observations to the analysis.