Targeting and image acquisition of Martian surface features with TGO/CaSSIS

CaSSIS is a high-resolution visual telescope onboard the ExoMars Trace Gas Orbiter. The mission started the primary science phase in April 2018. The relatively small single image footprint (typically 40 km × 9.5 km) when compared to the total surface area of Mars demands that images should be targeted and target selection is key for the science return. This paper describes the science planning concept set around the target selection, and the process followed in order to generate the CaSSIS commands.

The tools used are described as well as all the iterations and teams involved. Finally, special cases and the handling of contingencies are discussed. The procedures may serve as a guideline for future high-resolution instruments on missions to planetary objects.