ONBOARD STATIONKEEPING OF GEOSYNCHRONOUS SATELLITES USING A GLOBAL POSITIONING SYSTEM RECEIVER

Many space missions are considering the use of a Global Positioning System (GPS) receiver as a means of onboard ephemeris determination due to its portability, accuracy, and low cost. A feasibility study of onboard stationkeeping using a GPS receiver has been performed. This paper describes three strategies for onboard stationkeeping utilizing onboard GPS measurements. Algorithms are developed and accuracies of orbit control are assessed based on proposed strategies and covariance analysis. Although this study is focused on the application to geosynchronous satellites, the same technique applies to other missions with circular orbits. The innovative strategy of formation keeping a satellite with a fictitious satellite whose ephemeris is predetermined can significantly improve the long-term prediction accuracy without ground support. Results of simulations show that the maximum deviations from a predetermined ephemeris range from less than 0.1 km to 0.3 km dependent on onboard hardware/software options.