A Multiple Hypothesis Approach to Satellite Navigation Integrity

A general methodology has been developed for failure mitigation in satellite-based navigation systems. This new approach is founded on the direct evaluation of integrity risk under the unified consideration of all single-element failure hypotheses and the no-failure hypothesis. It is applicable to fault-tolerant estimation and integrity monitoring. In particular, the algorithm has been investigated for application as an airborne element of the Local Area Augmentation System (LAAS) integrity monitoring architecture. In this system, GPS ranging measurements from multiple ground-based reference receivers are to be used to mitigate the effects of reference receiver failures. The multiple hypothesis algorithm has been evaluated through analysis and simulation and has been shown to provide the tightest realizable protection limits for LAAS. The operational performance of the new algorithm has been compared with that of the approach currently under consideration by RTCA Special Committee-159. The performance of the multiple hypothesis algorithm has been demonstrated using experimental data collected during a series of LAAS prototype flight tests in a Beechcraft King Air.