Real-time navigation for mars final approach using X-ray pulsars

An accurate knowledge of Mars entry condition is the significant requirement for the successful aerocapture and pinpoint landing. In order to develop the real-time navigation scheme for Mars final approach, the feasibility of navigation embedded X-ray pulsar observations is verified, and the navigation performance is comparatively analyzed. In order to choose optimal navigation pulsars from pulsar candidates, the Fisher information matrix is utilized to evaluate the observability from the estimation theory point of view. The optimal navigation pulsars thus are selected such that the determinant of the Fisher information matrix is maximal. Two navigation scenarios based on the 2012 encounter at Mars of Curiosity spacecraft combining with X-ray pulsar based measurements are then considered to demonstrate the navigation performance. Furthermore, a series of research on the error ellipse in Mars B-plane and the distribution of estimated flight path angle indicate that Xray pulsar based navigation, which may provide more accurate knowledge of Mars entry condition, is a potential navigation scheme for Mars final approach in the future.