Abstract:

Inertial navigation system (INS) is not sufficient to lead a probe to land on an extraterrestrial body safely, because its calculation error grows up with time. A practical navigation method which combines INS with rangefinder and doppler velocimetry is proposed to solve this problem. Altimeter and velocimetry can give direct measurements of altitude and three-dimensional surface-relative velocity respectively, and can be used to correct the outputs of INS. In this paper, the principle of INS and the strategy of altitude and velocity modification are introduced. And these key problems about the descent dynamics, sensor measurement models, filtering equations, influence of terrains are discussed in details. Numerical simulation results indicate that this method can satisfy the requirement of extraterrestrial bodies for safe landing.

Key words: Safe landing, Autonomous navigation, Inertial navigation system, Rangefinder, Doppler velocity measurement