MASCOT2 - A small body lander to investigate the interior of 65803 Didymos‧ moon in the frame of the AIDA/AIM mission

International audienceIn the frame of Near-Earth-Object exploration and planetary defence, the two-part AIDA mission is currently studied by NASA and ESA. Being composed of a kinetic impactor, DART (NASA), and by an observing spacecraft, AIM (ESA), AIDA has been designed to deliver vital data to determine the momentum transfer efficiency of a kinetic impact onto a small body and the key physical properties of the target asteroid. This will enable derivation of the impact response of the object as a function of its physical properties, a crucial quantitative point besides the qualitative proof of the deflection. In the course of the AIM mission definition, a lander has been studied as an essential element of the overall mission architecture. It was meant to be deployed on Didymoon, the secondary body of the binary NEA system 65803 Didymos and it was supposed to significantly enhance the analysis of the body's dynamical state, mass, geophysical properties, surface and subsurface structure. The mission profile and the design of the 13 kg (current best estimate) nano-lander have been derived from the MASCOT lander flying aboard Hayabusa2. Differing from its predecessor by having an increased lifetime of more than three months, a surface mobility capability including directed movement, a sensor system for localization and attitude determination on the surface and a redesigned mechanical interface to the mother spacecraft. The MASCOT2 instrument suite consists of a bi-static, low frequency radar as main instrument, supported by an accelerometer, a camera, a radiometer and a magnetometer; the latter three already flying on MASCOT. Besides the radar measurements, the camera is meant to provide high-resolution images of the landing area, and accelerometers to record the bouncing dynamics by which the top surface mechanical properties can be determined. During the DART impact, MASCOT2 was expected to be able to detect the seismic shock, providing valuable information on the internal structure of the body. MASCOT2 was supposed also to serve as a technology demonstrator for very small asteroid landing and extended operations powered by a solar generator. In this paper, we describe the science concept, mission analysis of the separation, descent and landing phase, the operational timeline, and the latest status of the lander's design. Despite the fact that AIM funding has not been fully confirmed during the ESA Ministerial conference in 2016, MASCOT2 is an instrument package of high maturity and major interest for planetary defence and NEO science. With appropriate tailoring and optimization, it can be considered and studied for future missions