An observability-based trajectory optimization considering disturbance for atmospheric entry

Atmospheric entry guidance is a necessary technology for a Mars pin-point landing in the future. For a preferred reference-tracking guidance, trajectory optimization is an indispensable prerequisite. In order to account for the disturbance of initial states and atmospheric density which is a practical situation for Mars atmospheric entry as well as to improve the navigation performance, an observability-based robust trajectory optimization method is proposed. The determinant of Fisher information matrix is used to quantify the degree of observability, and the integration of the degree of observability is chosen as the objective function. Meanwhile, by introducing the polynomial chaos theory, the uncertainty propagation of states and path constraint functions can be characterized. Then the traditional trajectory optimization problem is transformed and solved by pseudospectral method. A Mars entry navigation scenario is considered and the entry trajectory is optimized. Simulation results demonstrate the efficiency and accuracy of the proposed method. Meanwhile, the accuracy of polynomial chaos and linearization approaches is also discussed. It is concluded that the proposed robust trajectory optimization method is more suitable for the scenario design of Mars atmospheric entry.