Generation of Large-Scale Orthophoto Mosaics Using MEX HRSC Images for the Candidate Landing Regions of China’s First Mars Mission

Abstract

Planetary mapping products play a significant role in landing site selection, surface operations, and scientific investigations. This paper describes the techniques and processes used to create geometrically controlled image mosaics for the candidate landing regions of China’s first Mars exploration mission (i.e., Tianwen-1) using Mars Express (MEX) High-Resolution Stereo Camera (HRSC) images. In order to deal with the extremely complex situations due to large data volumes (hundreds of images), various imaging conditions (e.g., 5–80° incidence angles), and long time spans (>10 years), we developed corresponding methods and in-house software for the photogrammetric processing of MEX HRSC images. According to the characteristics of planetary images and multi-line pushbroom imaging, we optimized the algorithms of establishing control network, eliminating blunders, setting weights and processing abnormal images. The generated MEX HRSC image mosaics with a resolution of 12.5 m delivered a high relative accuracy (<1 pixel). Compared with the existing Mars global image mosaics, the generated image mosaics exhibit significantly better spatial resolution. The techniques and methods that we developed to solve the complicated photogrammetric processing problems can also be applied to produce global or large-scale Mars mapping products using existing and new returned orbital images.