Ground and in-orbit testing of GPS for space applications

The use of GPS for space applications is rapidly developing. MATRA MARCONI SPACE (MMS) has developed AOCS concepts and designs based on GPS use and also acquired practical data through various experiments including hardware. The tests performed at MMS have contributed to the validation of the main in-orbit GPS applications. Orbital Navigation by GPS was validated for the Leostar project. The main performances of the selected receiver have been measured with a RF GPS simulator. Closed-loop tests in a full hardware avionics configuration have evaluated its robustness with respect to the LEO missions. During the ARP-K project, MIR-shuttle missions have demonstrated relative GPS techniques in flight for ATV rendezvous. Attitude determination by GPS has been tested using the real GPS constellation for realistic multi-path environment, both in static conditions for the Leostar project with a TRIMBLE receiver and in dynamics conditions for an ESA study with SEXTANT GPS-attitude receiver. These test campaigns have assessed the performance levels and pointed out the major error contributors showing the way to improvements. MMS will soon test the breadboard receiver of the Leeds University (UK), using the ASIC developed by ESA, in real conditions at ground level, and also with a RF stimulation. The purpose of this paper is to present all the test configuration set-ups used at MMS, the major results and the GPS experiments planned in the future.