Since December 2014 the Japanese spacecraft Hayabusa2 is on its journey to asteroid (162173) 1999 JU3. Like its famous predecessor it is expected to study and return samples from its target body. This time, the mother spacecraft has several small passengers. One of them is a compact landing package called MASCOT (Mobile Asteroid surface SCOuT), which has been developed by the German Aerospace Centre (DLR) and the Centre National d'Etudes Spatiales (CNES). Once having been released from its mother spacecraft's cradle, MASCOT will descend to the asteroid and after a few bounces will come to rest at a certain location on the surface. Sitting on the surface, it will perform its scientific investigations of the asteroids surface structure, mineralogical and physical properties, thermal behaviour and magnetic effects by using its suite of four scientific instruments: a spectrometer (MicrOmega, IAS Paris), a camera (CAM, DLR Berlin), a radiometer (MARA, DLR Berlin) and a magnetometer (MAG, TU Braunschweig). These payload operations are made possible by, amongst others, a clever thermal subsystem design specifically devised to cope with the contrasting requirements of cold cruise and hot on-surface operations and a primary battery optimizing mass versus energy output. A mobility mechanism realizes locomotion on the surface supported by an attitude and motion sensing system. An intelligent autonomy manager which is implemented in the onboard software can operate MASCOT when ground intervention is not available. In a nutshell, with its many challenging technical hurdles that have been solved, the MASCOT lander can serve as a benchmark for extremely lightweight (10 kg), highly integrated mobile small body landing systems with onboard autonomy and high science output. This paper will summarize the mission and system development. We will provide an overview of the final capabilities of the system as well as discuss the last challenging pre-launch activities and tests. Further a summary and an outlook regarding the already performed as well as upcoming post-launch activities will follow. Lessons have been learned and will be told to be ready for future upcoming missions for small solar system body exploration.