High Performance Low Cost Ranging System for STENTOR GEO Payload

Jacques Barbier and Frédéric Saffre

Abstract:	STENTOR is a technological satellite developed by French government to test new telecommunication services. This satellite shall be equipped with plasma thrusters which involves new station keeping algorithms (low thrust maneuvers). In order to acquire a good knowledge of the "plasmic" station keeping, CNES needs to measure very accurately the effect of each ionic thrust. This requires a high performance orbit determination system that the standard TCR (Telemetry, Control & Ranging) cannot fulfill. CNES/DLA/SDS/SM has therefore proposed to STENTOR Project a low cost and very accurate ranging system based on pseudolite measurements (SLF "Système de Localisation Fine"). The ranging system is based on synchronous generation of two L1-band pseudolites with different PRN codes and one GPS receiver. The first pseudolite is directly transmitted to the GPS receiver for precise measurement of transmission time. The second one is upconverted in Ku-band, transmitted at low power to the STENTOR geostationary payload, downconverted and broadcasted back to the station. The GEO signal is then received in the ground station, downconverted in L1-band to the GPS receiver for precise datation of the reception (the carrier phase of the GEO signal is servo controlled to guarantee adequate characteristics of the signal at the input of the receiver). The round trip transit time is then available for orbit computation. The development of a network of three SLF ranging stations has been entrusted to the IN-SNEC (Calvados - France). Individual ranging performances have been characterized on an external converter. Functional tests have been performed on existing Telecom 2 satellite. The SLF cabinet has been also used for precise transit time measurements of the real Stentor payload on ground. The paper details how the SLF concept has been implemented for STENTOR satellite. Functional and material architecture of the SLF ranging stations is described. Performance results obtained during factory and on-site acceptance are then presented.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	1627 - 1635
Cite this article:	Barbier, Jacques, Saffre, Frédéric, "High Performance Low Cost Ranging System for STENTOR GEO Payload," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 1627-1635.
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