A Low Cost Spacecraft Receiver For Orbit and Attitude Determination

Thomas Clark, Doug Varney, and Frank Bauer

Abstract:	Many Earth-orbiting spacecraft are now including a GPS receiver for orbit deter- mination (O.D), attitude determination (AD) and precision time and frequency (PT&F). For low cost missions, the price of a commercial receiver can be a signif- icant portion of the project budget. Further, most receivers are based on proprietary designs and the ability to customize for the specific application is expensive and controlled entirely by the receiver’s manufacturer. Simple C/A code receivers that are little more than adaptations of low-cost consumer-grade GPS receivers end up carrying price tags of = HO5 - $106. For many years radio amateurs have building small low-cost satellites under the aegis of the AMSAT (the Radio Amateur Satellite Corp.). AMSAT is a non-profit group whose “basement inventors” have demonstrated with the OSCAR series of satellites that low-cost implies neither low reliability nor low functionality. A series of 27 OSCAR satellites have used industrial grade components which have operated for several years in orbit with few unantici- pated failures. Similar parts and design philosophies have recently been adopted by NASA and the US military as cost cutting moves. Lately the words “small- er, cheaper, faster, better“ are heard throughout the aerospace industry. AMSAT now building another satellite called Phase-3D (P3D), scheduled to fly in 1996 on an Ariane-5 to a Molniya-like orbit. This mission will carry an Ll C/A code GPS receiver and an array of eight GPS antennas for orbit and attitude determination. NASA/GSFC also has many mission requirements for GPS receivers, and has teamed with AMSAT to develop the concept of a low-cost “open architecture” GPS receiver for such missions. The receiver under con- struction is expected to provide orbital data accurate at the lo-20 meter level, to determine spacecraft attitude accuiate to a few tenths of a degree, and to-serve as a high accuracy spacecraft time and frequency standard. This paper will describe the development of a space qualified GPS receiver based on the GPlOlO and GP1020 chip set from GEC Plessey and a PC-class-micro- computer. We will discuss reliability of the receiver’s industrial grade compo- nents and radiation testing of parts for single event upset (SEU) and total dose radiation (TDR) with Co,, source at a medical research facility.
Published in:	Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994) September 20 - 23, 1994 Salt Palace Convention Center Salt Lake City, UT
Pages:	1711 - 1718
Cite this article:	Clark, Thomas, Varney, Doug, Bauer, Frank, "A Low Cost Spacecraft Receiver For Orbit and Attitude Determination," Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994), Salt Lake City, UT, September 1994, pp. 1711-1718.
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