ESA's PROBA Mission to include Space GPS Receiver

GPS World, Oct, 1999

The European Space Agency's (ESA's) Project for On Board Autonomy (PROBA) will employ a SGR-20 Space GPS Receiver recently delivered to the project by Surrey Satellite Technology Limited (SSTL). The four-antenna, 24 (L1)-channel receiver was developed by SSTL, a University of Surrey research and development company working at the Surrey Space Centre in Guildford, United Kingdom.

Designed to evaluate the advantages of autonomous spacecraft operations, the PROBA project's baseline for the simulation is an Earth observation mission based on a multispectral imager as a payload. The spacecraft, which is scheduled to launch in July 2000 on India's PSLV, will autonomously take and transmit images based on user requests.

The SGR will primarily be used for positioning and timing on board PROBA, as well as to provide an experimental attitude determination capacity. SSTL has already demonstrated the SGR's capabilities on its own UoSAT-12 minisatellite launched in April, as well as on TMSat, a microsatellite built for Thailand and launched last year.

The UoSAT-12 was built to validate minisatellite bus and payload technologies such as the SGR. The space receiver's orbit and attitude determination functions were successfully tested shortly after UoSAT-12's launch. From an "autonomous start" with no prior knowledge, the SGR achieved a position fix in 6.5 minutes. Positioning data were continuous over the five hours of test operation in orbit, with the SGR tracking from six to 12 GPS satellites simultaneously. Preliminary processing of the output suggests that the orbital position accuracy is as expected.

Experimentation is continuing on the UoSAT-12, including the development of rapid initialization procedures and the operation of multiple antennas on the spacecraft.