EUROPEAN COMPLEMENT TO GPS - ORBIT DETERMINATION STRATEGIES AND RESULTS OF PRELIMINARY EXPERIMENTS

The reference mission of the European Complement to GPS (CE-GPS) is de stined to insure the integrity of the navigation message of the U.S. G lobal Positioning System (GPS) for the Civil Aviation community. CE-GP S is based on a geostationary payload capable of transmitting a GPS-li ke signal to ground users (civil aviation extended to maritime and ter restrial transport). This signal is broadcasted from a ground station (the Feeder Link Station) towards the geostationary which repeats it. The signal includes both a navigation message (GPS satellites ephemeri des) and a health status of the GPS constellation (integrity message). An Operational Orbitography Center capable of processing the orbits o f the geostationary and GPS satellites elaborates the navigation and i ntegrity messages. The measurements required for the computation of th e orbits are collected by a network of about six Monitoring Stations ( in the equatorial area) and transmitted to the Feeder Link station. Ex periments are under way to test the different new techniques involved in the development of the ground stations, and to select the optimal s trategies for the geostationary orbit determination process and for st ation synchronization.This paper presents the different orbit determin ation strategies developed for the geostationary satellite and prelimi nary results obtained with data collected during two campaigns: autumn 1993 with two ground stations (Paris and Toulouse) and Spring 1994 wi th three ground stations (Kourou, Hartebeeshoek and Toulouse). The pap er is organized in three parts: first, the CE-GPS concept is presented ; second, the experimental system designed by CNES to assess the CE-GP S technical performances is described; and last, the experimental resu lts are presented. Copyright (C) 1996 Elsevier Science Ltd