Orbit optimization of Mars orbiters for entry navigation: From an observability point of view

•The impact of orbiter configuration on observability of entry navigation is analyzed.•An observability-based orbit optimization method is proposed.•Optimal orbits with the maximum degree of observability are computed.•Orbiter-based navigation surpasses the accuracy of ground beacon-based navigation.

In this paper, the observability of orbiter-based Mars entry navigation is investigated and its application to the orbit optimization of Mars orbiters is demonstrated. An observability analysis of Mars entry navigation processing of range measurements to multiple orbiters based on Fisher information matrix is conducted. The determinant of Fisher information matrix is derived to quantify the degree of observability. The orbit optimization method based on the observability analysis is then proposed. Two navigation scenarios using three and four orbiters are considered in simulations. To verify the advantages of navigation performance, the orbiter-based and ground beacon-based navigation schemes are comparatively analyzed. In the simulation, an Extended Kalman Filter is used to examine the navigation accuracy. It is concluded that the proposed orbit optimization method is able to optimize the orbits of Mars orbiters with the maximum degree of observability. For the Mars entry navigation based on orbiters, a better configuration which is a main contributor to the observability, can be achieved. The navigation performance is more excellent than the ground beacon-based navigation. However, a diminishing return of navigation accuracy is obtained solely by increasing the number of orbiters.