In project A3 “Ancient bombardment of the inner solar system – Reinvestigation of the ‘fingerprints’ of different impactor populations", we investigate the lunar cratering record and its crater size-frequency distribution (CSFD). Although CSFDs are widely used for the determination of relative and absolute planetary surface ages, it is still not clear whether there was more than one impactor population involved in the formation of the Moon’s cratering record during the late accretion period. Since current methodologies for dating the lunar surface assume that there was only one population involved, i.e., the origin of impacting projectiles remained constant, a combination of different populations would influence the age determination results significantly. In project A3, we thus conduct detailed geological mapping and crater size-frequency measurements in combination with new approaches of GIS spatial analyses to investigate the shapes of CSFDs and to validate the suitability of regions which were previously used for this purpose. Altogether, this will help to improve the methods of CSFD-based age determination, to examine a potential time-variable lunar crater production function and to further understand the late accretion history of planetary bodies in the inner solar system.