Preliminary Orbital Results from the SGR Space GPS Receiver

M.J. Unwin, M.K. Oldfield, S. Purivigraipong, Y. Hashida, P.L. Palmer, Ian Kitching

Abstract:	The SGR is an advanced 24 channel L1 GPS receiver that has recently been developed at the Surrey Space Centre, UK in collaboration with ESA, and this paper describes its first use in orbit. The receiver has been designed for the space environment, but is intended for small satellites with a smaller budget. Commercial technology is almost exclu-sively used, but key components have been verified for radiation tolerance in tests. The receiver can take parallel phase measurements from four antennas simultaneously, giving the potential for attitude determination. The SGR has the ability to accept new code, even while in orbit, to permit experimentation with new orbit and attitude deter-mination algorithms. UoSAT-12 is a privately funded 300 kg minisatellite launched on 21 st April 1999 on a converted SS-18 ICBM. UoSAT-12 is a technology development and demonstra-tion satellite that carries a multitude of remote sensing, at-titude determination and control, propulsion, on-board data handling, and communications experiments. The GPS experiment is a version of the SGR that can make use of up to 5 antennas for positioning and attitude determination experimentation. Preliminary operational results have seen up to twelve GPS satellites simultaneously tracked, and autonomous cold starts within 7 minutes. The SGR and the cold gas propulsion system are being used for trials with autonomous orbit determination and control. The SGR is designed such that phase can be measured simultaneously at four front-ends and therefore allows phase differences to be recovered directly. Re-search at Surrey is investigating the most appropriate and robust algorithms for attitude determination, and these will be tested on UoSAT-12 in orbit. In addition to UoSAT-12, TMSAT-1 is carrying a version of the SGR, and future satellites, Tiungsat, Tsinghua-1 and the ESA PROBA mission will also be carrying the SGR in space. The capability to update software in orbit overcomes unexpected software problems, and enables research algorithms to be demonstrated in both orbit and attitude determination. These experiments should help establish the SGR as a robust space GPS receiver for many future small satellite applications.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	849 - 856
Cite this article:	Unwin, M.J., Oldfield, M.K., Purivigraipong, S., Hashida, Y., Palmer, P.L., Kitching, Ian, "Preliminary Orbital Results from the SGR Space GPS Receiver," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 849-856.
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