X-RAY PULSAR NAVIGATION OPTIMIZATION USING SPHERICAL PARTITIONS

X-ray pulsars are stars which appear to periodically pulse due to the beams of energy which emanate from their magnetic poles as they rotate. This periodic pulsing proves useful and allows for X-ray pulsar based navigation (X-Nav) systems to be developed. However, the periodic nature of the signal makes it difficult to discern one pulse from the next when coming from the same pulsar. This introduces the problem of ambiguous measurements which leads to multiple possible solutions for position estimation algorithms which must be filtered in order to implement X-Nay. We investigate the use of a grid of spherical volumes to partition the mission space in order to reduce the computational load of resolving the ambiguity problem. Only spheres which may contain a potential position solution are analyzed further. The remaining spheres which have no chance of containing a potential solution can be ignored, thus reducing the computational complexity of the problem by prefiltering the potential locations in space where a valid position estimate may exist. We present a detailed implementation of this algorithm as well as preliminary simulation results which demonstrate the change in performance due to implementing this prefiltering.