GPS orbit processing in support of low Earth orbiter precise orbit determination

There are currently an increasing number of LEO missions incorporating dual frequency GPS receivers for Satellite to Satellite Tracking. The majority of LEO precise orbit determination (POD) strategies rely on high quality GPS orbits and clocks such as those supplied by the IGS Final product. The availability of these products may not satisfy operational requirements due to their ten day latency. This paper studies the effect on the accuracy of the LEO POD of different kinds of GPS products as produced by ESOC, an IGS Analysis Centre. GPS products have been used for generating LEO POD results that differ in latency, frequency, and in being estimated or predicted. These results are then compared as part of the IGS LEO Pilot project to determine the improvement and degradation that can be expected by using the different GPS products. Additionally this paper will discuss an approach for the simultaneous solution of LEO and GPS POD. A simultaneous solution approach has the potential of providing improvements both in the GPS and in the LEO products, or to use fewer ground stations for generating the IGS products. In addition, it can reduce the latency that appears in the generation of LEO results based on separate GPS products. (C) 2003 COSPAR. Published by Elsevier Science Ltd. All rights reserved.