A Miniature GPS Receiver for Precise Orbit Determination of the Sunsat 2004 Micro-Satellite

Oliver Montenbruck, Ben Nortier, and Sias Mostert

Abstract:	This paper describes the design of a miniature receiver for spaceborne GPS navigation and its use for precise orbit determination within the Sunsat 2004 project. Sunsat 2004 is the second remote sensing micro-satellite built by Stellenbosch University, South Africa. It carries a multispectral imaging payload with a resolution of 5 m and will be ready for launch in the second half of 2005. As part of the Sunsat 2004 mission, a Phoenix GPS receiver will provide navigation and timing information for real-time spacecraft operation. It is based on commercial-off-theshelf hardware (SigTec MG5001) but employs software specifically designed for high-dynamics applications. The receiver offers L1 C/A code and carrier tracking on 12 channels with representative accuracies of 0.4 m and 0.7 mm. The real-time navigation solution provided by the Phoenix receiver is typically limited to an accuracy of about 5-10 m by broadcast ephemeris and ionospheric errors. Raw measurements will therefore be down-linked and processed offline for precise orbit determination. Here, ionospheric path delays can be fully eliminated using a linear combination of L1 code and carrier data. In combination with precise orbit and clock products of the International GPS Service (IGS), a 3D accuracy of 0.5m can thus be achieved. The receiver has extensively been validated in a GPS signal simulator testbed, and the resulting measurements are used to demonstrate the envisaged performance of the Sunsat 2004 orbit determination concept.
Published in:	Proceedings of the 2004 National Technical Meeting of The Institute of Navigation January 26 - 28, 2004 The Catamaran Resort Hotel San Diego, CA
Pages:	636 - 642
Cite this article:	Montenbruck, Oliver, Nortier, Ben, Mostert, Sias, "A Miniature GPS Receiver for Precise Orbit Determination of the Sunsat 2004 Micro-Satellite," Proceedings of the 2004 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2004, pp. 636-642.
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