Mars atmospheric entry guidance using a sensitivity method

In this study, we propose two simple analytical reference drag profile (RDP) update algorithms for drag-based Mars atmospheric entry guidance. First, the dynamic model for the predictive range-to-go is modeled. Then, a parameter sensitivity theory in dynamic systems is applied to investigate this dynamic model and design RDP update algorithms. The two algorithms are, respectively, named as the constant update algorithm and the linear update algorithm. In the developed algorithms, a constant correction and a linear correction are used to update the current RDP. The two update algorithms are implemented without any iterative procedure. The linear update algorithm is expected to obtain higher range control accuracy than that of the constant update algorithm, because it is designed by considering the range control authority. A quasi-crossrange parameter is employed to design the bank-reversal logic. The damping coefficient for the quasi-crossrange parameter is updated with the bank reversals, using a simple gain scheduling method. Comparisons of the proposed algorithms with the entry terminal point controller and the drag-based guidance without RDP updates demonstrate the excellent performance of the proposed algorithms.