Drag-based entry guidance for mars pinpoint landing

Future Mars missions require pinpoint landing capability, which motivates the need for closed-loop guidance. In this paper, a drag-based tracking guidance algorithm is present, which is modified on the basis of Space Shuttle entry guidance to accommodate a fixed trim angle of attack and a high ballistic coefficient and a very low lift capability. The guidance concept is to predict a reference drag acceleration, along with the initial states and bank angle profiles. In this paper, the active disturbance rejection control (ADRC) algorithm is applied to steer the bank angle to track the reference drag acceleration, thus to control the flying trajectory. Simulation results show that this entry guidance algorithm consistently achieves the desired target conditions.