AIM: Asteroid touchdown
ESA's next landing on a small body since Rosetta's Philae lander touched down on its comet in 2014 is proposed to take place as part of the Agency's Asteroid Impact Mission.In 2022 the Mascot-2 microlander would be deployed from the main AIM spacecraft to touch down on the approximately 170-m diameter ‘Didymoon’, in orbit around the larger 700-m diameter Didymos asteroid.The 15 kg Mobile Asteroid Surface Scout-2 (Mascot-2) is building on the heritage of DLR’s Mascot-1 already flying on Japan’s Hayabusa-2. Launched in 2014, the latter will land on asteroid Ryugu in 2018.Mascot-2 would be deployed from AIM at about 5 cm/s, and remain in contact with its mothership as it falls through a new inter-satellite communications system. Didymoon’s gravity levels will only be a few thousandths of Earth’s, so the landing would be relatively gentle, although multiple bounces may take place before it comes to rest.Light-emitting diodes (LEDs) would help AIM to pinpoint its microlander’s resting place from orbit. In case of a landing in a non-illuminated area, a spring-like ‘mobility mechanism’ would let the microlander jump to another location. Onboard GNC ‘guidance navigation and control’ sensors would gather details of the landing both for scientific reasons and to determine the microlander’s orientation for deployment of the solar array to keep it supplied with sufficient power for several weeks of surface operations.As well as a solar array, AIM would also deploy its low frequency radar LFR instrument, while cameras perform visible and thermal surface imaging. LFR would send radar signals right through the body, to be detected by AIM on Didymoon’s far side, to provide detailed subsurface soundings of an asteroid’s internal structure for the first time ever. Then Mascot-2 would repeat these measurements after Didymoon has been impacted by the NASA’s DART (Double Asteroid Redirection Test) probe, to assess the extent of structural changes induced by this impact event. AIM and DART together are known as the Asteroid Impact & Deflection Assessment mission.