GEO Orbit Determination Via Covariance Analysis With a Known Clock Error

Edward Carolipio, Nitin Pandya and Mohinder Grewal

Abstract:	Geostationary Earth Orbit (GEO) satellites serve as relays to transmit messages for Space Based Augmentation Systems (SBASs), such as the Wide Area Augmentation System (WAAS), the European Geostationary Navigation Overlay Service (EGNOS), and the Multifunction Transport Satellite Based Augmentation System (MSAS). GEOs can act as ranging sources for SBAS users as well, adding to the availability and continuity of a number of SBAS services, as long as the GEO range errors are comparable to GPS range errors. The SBAS determines the GEO orbit error from covariance analysis of satellite dynamics and station-to-satellite geometry. Unfortunately, since the GEO is essentially stationary relative to the SBAS stations, separating the orbit determination errors from the clock errors is difficult. GEO range errors tend to be much larger than the GPS range errors. If the GEO orbit errors could be separated, or decoupled, from the clock errors, the GEO could become a more effective ranging source. This paper proposes a technique to make the GEO clock state a known quantity, hence performing this decoupling. Further, this paper considers this method’s effect on the derived GEO range error using Kalman filter analysis. Using this technique dramatically reduces the GEO orbit error by a factor of ~22 and implies the GEO could be used effectively as a ranging source.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	2360 - 2365
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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