Precise, Efficient GPS-Based Geometric Tkacking of Low Earth Orbiters

Sunil B. Bisnath and Richard B. Langley

Abstract:	Present GPS-based orbit determination techniques introduce spaceborne GPS (SGPS) receiver measurements from low earth orbiter (LEO) spacecraft into classical (dynamic) orbit determination (OD) strategies, to produce accurate a posterior orbits for the LEO and the GPS constellation. A purely GPS-based tracking strategy is proposed, that does not require dynamic models and filly utilises the properties of the GPS data. The strategy - the geometric tracking strategy – consists of applying the relative positioning technique between the LEO receiver and International GPS Service (IGS) terrestrial receivers to smooth LEO pseudorange-based position with carrier phase-based position change in a kinematic, sequentia~ least squares fflter/smoother. The required inputs are the LEO receiver measurements, IGS precise GPS orbits, a subset of the IGS receiver network measurements, and associated station coordinate and tropospheric zenith path delay estimates. An error propagation study was devised and carried out. Results from the study with simulated data indicate that decimetre-level position component precision can be attained. Equally-precise LEO position estimates at non-GPS measurement epochs can be computed from the falter/smoother results via interpolation. The technique promises to produce precise tracking results in only tens of minutes, regardless of LEO dynamics. Plans for future work include processing actual SGPS data, optimizing and improving computer realisation of the strategy, and improving upon the interpolation algorithms.
Published in:	Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999) June 27 - 30, 1999 Royal Sonesta Hotel Cambridge, MA
Pages:	751 - 760
Cite this article:	Bisnath, Sunil B., Langley, Richard B., "Precise, Efficient GPS-Based Geometric Tkacking of Low Earth Orbiters," Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999), Cambridge, MA, June 1999, pp. 751-760.
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