Applying GPS to a Constellation of Disaster Monitoring Satellites

Scott Gleason, Martin Unwin, Yoshi Hashida, and Mounir Adjrad

Abstract:	The Disaster Monitoring Constellation (DMC) is a programme led by Surrey comprising five microsatellites in low Earth orbit to provide daily imaging world-wide for the monitoring and mitigation of natural and man-made disasters and for dynamic Earth observation. Individual satellites are contributed by international partners and are used in co-ordination to increase the coverage of the Earth on a daily basis from space [SILV01]. The UK BNSC awarded SSTL funding for one microsatellite in the DMC, the Centre National des Techniques Spatiales (CNTS) of Algeria is providing one satellite [OUSS01], as is the Federal Ministry of Science & Technology of Nigeria, and two other countries are expected to be joining. To minimise cost and to ensure compatibility, the satellites are being manufactured at Surrey in collaboration with the international partners. Within the collaborative programme between SSTL and CNTS, a team of 11 Algerian engineers commenced work at Surrey in November 2000, working alongside SSTL engineers for 18 months on the design, build, launch and commissioning of Algeria’s first microsatellite, AlSAT-1. The programme has included the installation of a mission control ground-station in Algeria and associated training. The first DMC satellite, AlSAT-1, is expected to be launched in November 2002, with subsequent satellites following in May 2003. Each satellite in the constellation benefits greatly from the use of an on-board GPS receiver. GPS can offer routine orbit determination, on-board clock synchronisation, support for imaging operations, and feedback from orbit control operations. As on previous missions, the receiver to be used is Surrey's own SGR Space GPS Receiver [UNW00]. The UoSAT-12 mission, for example uses a five-antenna receiver for experimentation in orbit and attitude determination. In routine operations, there is sufficient power margin to permit the GPS receiver to be operated continuously. On the DMC satellite design, where a dual GPS antenna receiver is to be used, there is less power available, and an intermittent operating scheme is required for the receiver that minimises the power consumption, while considering the practicalities of operating a spaceborne GPS receiver and retaining all the benefits GPS offers.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	2059 - 2065
Cite this article:	Gleason, Scott, Unwin, Martin, Hashida, Yoshi, Adjrad, Mounir, "Applying GPS to a Constellation of Disaster Monitoring Satellites," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 2059-2065.
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