The Generation of TGO-CaSSIS Stereo Products after six years of scientific mission: The Complete Stereo Chain of INAF

Abstract. CaSSIS (Colour and Stereo Surface Imaging System) on board the ExoMars Trace Gas Orbiter, which has been capturing images of Mars since April 2018, is a multispectral stereo camera and its stereo and colour data are used for generating high-resolution, three-dimensional maps and orthorectified images of the Martian surface. The instrument has already taken more than 50.000 images and covering >7.6% of Mars' surface, producing a total of 23.8 Tbit of data, with a small percentage (4.8%) taken using colour filters. These data are processed with the 3DPD software, which creates DTMs and orthorectified images with a ground resolution of 13.5 m per pixel and vertical accuracy of around 8 meters. All the stereo products are available to the scientific community through the INAF-hosted repository. The 3DPD software pipeline includes various stages: pre-processing to remove optical distortions and mosaicking, a matching core and DTM interpolation routines. A recent improvement through the integration of Bundle Adjustment, using the jigsaw tool from the USGS ISIS suite, has enhanced the precision of the data, reducing errors in the final 3D products. Overall, the work on CaSSIS and 3DPD plays a significant role in advancing Mars exploration, producing high-quality topographic maps and spatial data critical for scientific research.