MARS ATMOSPHERIC ADAPTIVE ENTRY GUIDANCE BASED ON ON-BOARD TRAJECTORY PLANNED

An adaptive entry guidance is presented for Mars exploration lander with low lift-to-drag ratios, the limited control authority and large initial states bias. The law is developed based on on-board trajectory planned. Firstly, the nominal trajectory is designed which described by the downrange value and other states such as drag acceleration, altitude rate. Then to the large initial state bias, the nominal downrange value is modified on-board by weighing the landing accuracy, control authority and parachute deployment altitude. The most prominent advantage of this approach is that it can successfully correct altitude error and avoid the control saturation. Finally, simulation results illustrate the adaptive guidance law can effectively decrease the parachute deployment altitude and dynamic press error.