Study On High-precision Integrated Navigation Technology For Mars Entry Under Large Uncertainty

There are larger atmospheric density uncertainty and vehicle’s aerodynamic parameters uncertain deviations in Mars entry dynamics, which heavily degrades Mars entry and landing accuracy. It’s believed that the navigation and guidance accuracy of Mars entry phase is the main decisive factor for landing accuracy. The traditional dead reckon based entry navigation cannot meet the requirement of future Mars pin-point landing mission. Therefore, it’s critical to develop new suitable navigation technology under the condition of large uncertainty for Mars entry.In this dissertation, innovative high-precision integrated navigation for Mars entry under large uncertainty is studied from following three aspects: integrated navigation scheme, navigation filtering algorithm, and observability analysis. Firstly, according to the given Martian environment model and entry vehicle configuration, simulation dynamics model is set up for simulating the real flight dynamics, and the evolution kinetic model is built up for subsequent navigation filter design. Secondly, radiometric measurements between entry vehicle and three orbiters are adopted as external correction, and desensitized extended kalman filter based integrated navigation algorithm is developed. Simulation results show that this integrated navigation algorithm can suppress the adverse impact of uncertain deviation and achieve higher navigation accuracy. Thirdly, one orbiter and two Mars surface beacons are adopted as external correction, and modified multiple model adaptive estimation based integrated navigation algorithm is proposed to overcome the undesired effect of larger uncertainty. Simulation results show that this integrated navigation method can enhance the adaptability for uncertain parameters and further improve navigation accuracy. In addition, Mars atmospheric density can also be precisely estimated as the by-product of navigation filter. Finally, the observability analysis of the two integrated navigation schemes above is performed. Simulation results show that the external measurement configuration is the main decisive factor for both system observability and navigation error, while the uncertain deviation in the dynamics model only impacts system observability in a local range.