Illumination Robust Landing Point Visual Localization for Lunar Lander With High-Resolution Map Generation

Landing point localization is of great significance to the lunar exploration engineering and scientific missions. Vision-based landing point localization methods have successfully been utilized in Chang'e series missions. The issues in landing point visual localization task containing low-resolution reference maps, illumination changes between descent images and maps, and low automation of the localization workflow still need to be solved. In this article, a high-precision and automatic landing point visual localization method with high-resolution map generation is proposed, including initial localization of the first frame, hybrid fine matching, landing point propagation in descent sequence images, and absolute position estimation for landing point. High-resolution digital elevation model and digital orthophoto map (DOM) are generated from Lunar Reconnaissance Orbiter Camera Narrow Angle Camera images and SLDEM2015 data. Phase-based image matching method is adopted for initial localization and matching between descent image and reference map to enhance the illumination robustness. The performance of our method is validated using the descent sequence images from Chang'e series missions. For Chang'e-6 lander, the estimated landing point coordinates are ($-$153.9870$^{\circ }$ $\pm$ 0.00002$^{\circ }$, $-$41.6378$^{\circ }$ $\pm$0.00001$^{\circ }$, $-$5256.962 m $\pm$ 0.0041 m). Compared with the manually measured lander coordinates, the deviation of landing point position is less than 1 pixel in DOM.