Ephemeris Failure Rate Analysis and its Impact on Category I LAAS Integrity

L. Gratton, R. Pramanik, H. Tang, B. Pervan

Abstract:	One of the integrity concerns for the Local Area Augmentation System (LAAS) is the ephemeris threat scenario. The responsibility of detecting such failures lies on the LAAS Ground Facility (LGF). It is essential for the system to provide monitor functions that minimize the integrity risk, while not affecting the availability and continuity levels significantly. At the very first stage of the monitor analysis, it is necessary to use an ephemeris Failure Rate (FR) in order to derive the monitor requirements. This paper derives a FR from rigorous analysis of the GPS performance standards to ensure that the rate used is conservative. The FR is further supported using archived ephemeris data from the last 10 years. The detailed analysis necessary to obtain the FR also leads to a new requirement to ensure integrity: the need of a solid notification channel between GPS and the LGF for failures and maneuvers. In case that reliable notification link cannot be established, some threats would remain unmitigated. Ideas on monitors that could potentially solve this problem are presented on this paper, as well as initial results on simulations to establish their effectiveness.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	386 - 394
Cite this article:	Gratton, L., Pramanik, R., Tang, H., Pervan, B., "Ephemeris Failure Rate Analysis and its Impact on Category I LAAS Integrity," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 386-394.
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