Use of double difference observations in combined orbit solutions for LEO and GPS satellites

At ESOC's Navigation Office a new approach to double differenced data processing is being implemented for combined solutions with GPS and LEO satellites. The algorithm enables efficient processing of virtually all double differenced combinations that are geometrically possible between the LEO satellite, a terrestrial ground station, and any two GPS satellites that are in common view. The concepts behind this algorithm will be explained, and it will be shown how such large numbers of double differenced measurements can enhance the stability of the simultaneous estimation process for all involved orbits, clocks and phase ambiguity parameters. Some applications to CHAMP and JASON will be shown.