GPS Space Navigation: A Robust Approach to Withstand Multiple Satellite Failures

Carlo Carnebianca

Abstract:	Autonomous orbit determination functions are expected to be increased in the near future for system survivability enhancement. In this context, the Global Positioning System (GPS) is expected to play an important role for low earth orbit (LEO) applications. A GPS receiver, in fact, is capable of providing real-time host vehicle position and velocity with unprecedented accuracy. Navigation solution is accomplished by propagating forward in time the so called "user's nominal solution" according to a predefined process dynamics model. Such a solution is systematically corrected by adequate filtering of GPS measurements. The lessons learned supported by a full require sophisticated the navigation filter. indicate that navigation GPS constellation does not dynamics model on the part of Problems may arise in presence of multiple GPS satellite failures. A reduced constellation, in fact, can significantly degrade the system performance, as it was demonstrated by Landsat experiment. To overcome such undesirable effects, augmented gravity models should be considered in the navigation solution propagation. With this approach, the position/velocity error build-up, even in presence of a substantially reduced GPS constellation, could be bounded within limits comparable to nominal performance. This paper provides a study case on the subject, with relevant system modelling and Kalman filter design major characteristics. The analysis results show a clear evidence of the performance degradation reduction as the number of higher harmonics increases in the navigation filter gravity model. In this perspective, gravity model augmentation, which might only be limited by the onboard hardware computational capacity, seems an effective solution to enhance space navigation performance in presence of severe GPS outage.
Published in:	Proceedings of the 2nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1989) September 27 - 29, 1989 The Broadmoor Hotel Colorado Spring, CO
Pages:	145 - 148
Cite this article:	Carnebianca, Carlo, "GPS Space Navigation: A Robust Approach to Withstand Multiple Satellite Failures," Proceedings of the 2nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1989), Colorado Spring, CO, September 1989, pp. 145-148.
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