DART/LICIACUBE PRE-IMPACT GEOLOGICAL ASSESSMENT OF THE NEA (65803) DIDYMOS SYSTEM

On September 26, 2022, the NASA DART spacecraft will impact the surface of Dimorphos, the 160 m size satellite of the S-type binary near-Earth asteroid (NEA) (65803) Didymos. In order to provide the best possible pre-impact surface assessment of Dimorphos, the spacecraft carries the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) camera (Rivkin et al., 2021). During the final four minutes before DART impact (T0) the DRACO images will be useful for characterizing the shapes, characteristics, and geology of the asteroids reaching spatial scales on Didymos ranging from 6 m/pixel to 3.5 m/pixel. Instead, in the final few seconds before T0, 0.5 m- to 0.1 m-resolution images of Dimorphos will be taken, hence providing pivotal information for characterizing the impact site at the scale of the spacecraft. Piggy-backing on the DART spacecraft during the launch, the Italian Space Agency (ASI) Light Italian Cubesat for Imaging of Asteroids (LICIACube, Dotto et al. 2021) will travel together with DART to the target. Released 10 days before impact, the LICIACube spacecraft will observe the binary asteroid and the DART impact from a close approach (CA) distance of 51 km. Two optical imagers will provide the observations: the LICIACube Explorer Imaging for Asteroid (LEIA), which is a high-resolution panchromatic camera, and the LICIACube Unit Key Explorer (LUKE), which is a wide-angle 3-band color imager (RGB Bayer pattern filter). At CA, LEIA will return images of Dimorphos' surface with a spatial scale < 2 m/pixel, complementing all DRACO observations performed during the pre-impact phase. Such dataset will be useful to pursue a multi-resolution geological characterization of 2/3 of the illuminated surface area of both Dimorphos and Didymos, improving the accuracy of the Dimorphos' shape and volume determination. What will be observed on the surfaces of both asteroids and at the DART impact site is still currently unknown, yet we describe here the main geological attributes we might find, using as a guide the previously observed NEAs and our current understanding of the formations of small and binary asteroids. Moreover, we will discuss the mapping strategies we plan to use, and the type of geological features and processes that we will seek to identify and analyze to understand Dimorphos' surface and interior structure.