Test Results of the PiVoT Receiver in High Earth Orbits using a GSS GPS Simulator

There is widespread interest in expanding the use of GPS for real-time on-orbit navigation of satellites or satellite constellations in highly eccentric or geostationary orbits. Recent studies have indicated that GPS is a viable option for these missions when used with an orbit determination filter to sequentially process sparsely available pseudorange measurements. Several organizations have undertaken efforts to develop new space GPS receivers that will satisfy this need. This paper presents results of tests conducted on the PiVoT GPS receiver under development at NASA Goddard Space Flight Center. A variety of design enhancements are being incorporated in the PiVoT receiver to enable its operation in a wide variety of high Earth orbits (HEO). Some of these features include integration of the GPS Enhanced Orbit Navigation System (GEONS), a good quality local oscillator, a robust clock model, and enhancements to basic receiver acquisition and tracking algorithms to enhance the ability of the receiver to track weaker GPS signals present in HEO. A realistic HEO test capability has been developed using a Global Satellite Systems (GSS) GPS simulator at NASA GSFC. The hardware in-theloop test setup is detailed, including specific