Centimeter-resolution topographic modeling and fine-scale analysis of craters and rocks at the Chang'E-4 landing site

Chang'E-4 was the first lunar mission to successfully land on the far side of the Moon. The stereo images collected by the panoramic camera (Pancam) mounted on the Jade Rabbit-2 rover have provided the most detailed in situ observations of the landing site along the rover traverse. This paper presents our efforts in centimeter-resolution topographic modeling and fine-scale analysis of craters and rocks at the Chang'E-4 landing site using the Pancam images. We first used an integrated photogrammetric and photoclinometric approach to generate a digital elevation model (DEM) and an orthoimage mosaic of the landing site and a 3D model of the Chang'E-4 lander itself, all with spatial resolutions of 1 cm/pixel. Craters with diameters of decimeters to meters and rocks with sizes of decimeters were then extracted and analyzed. The results indicate that Chang'E-4 landed on a terrain slope of 4 degrees toward 72.3 degrees southwest, with one foot sunk in the regolith 1.5 cm deeper than the other foot on the front side of the lander. Fine-scale analysis of the small craters at the Chang'E-4 landing site showed overall a similar power-law trend as large craters of hundreds of meters, but there is a clear gap between their size-frequency distributions, indicating the accumulated impact flux appears to be different for these two crater populations. The average depthto-diameter ratio of the small craters around the landing site was 0.061, obviously less than those of craters on the kilometer scale. Fine-scale analysis of rocks revealed that the Chang'E-4 landing site has a rock abundance of 0.21%, which agrees well with previous results based on orbital data. Joint analysis of craters and rocks indicates that more rocks are located inside craters with greater depth-to-diameter ratios on such a fine scale. The 3D topographic modeling approach and fine-scale analysis of craters and rocks presented in this paper provide new insights into lunar mapping and geological study. (C) 2020 The Authors. Published by Elsevier B.V.

Automated summary

This study utilized Pancam images to conduct centimeter-resolution topographic modeling and fine-scale analysis of craters and rocks at the Chang'E-4 landing site. Results revealed a terrain slope of 4 degrees at the landing site, an average depth-to-diameter ratio of 0.061 for small craters, a rock abundance of 0.21%, and a tendency for more rocks to be located inside craters with greater depth-to-diameter ratios.