Crater Navigation System for Autonomous Precision Landing on the Moon

Abstract

Interest in autonomous planetary precision landing missions has been increasing in the scientific and engineering community, and is likely to continue to do so for the foreseeable future. As an enabling technology in the context of lunar landing, DLR, German Aerospace Center has been developing a terrain absolute navigation system that matches craters detected in image data to globally available lunar crater maps. The proposed Crater Navigation (CNav) system is adaptive, comprising three different crater matching methods that are specifically tailored to different navigation conditions encountered during the vehicle descent, so that it may be used as a stand-alone navigation sensor that can be closely integrated with a lander guidance, navigation, and control system to enable reliable absolute navigation throughout the entire descent phase of a mission. As robustness is a vital aspect to mission success, the CNav system includes verification mechanisms that ensure high dependability of the resulting navigation solution. This robustness is verified separately for all of the three different matching techniques presented in this paper. Closed-loop performance of the matchers is demonstrated as well, both for simulated image data sets, as for navigation camera images acquired during the Chinese Chang’e-3 landing mission. Successful uninterrupted estimation of the entire Chang’e-3 kinematic vehicle state during the powered descent until a final altitude of 350 m above ground, with neither known camera calibration nor inertial measurement unit data available, showcases the potential of the CNav system.