The Preimpact Search for Further Didymos Natural Satellites Using DART and LICIACube Images

On 2022 September 26, the NASA/DART spacecraft performed the first-ever test of the kinetic impactor technique by hitting Dimorphos, the moon of the asteroid (65803) Didymos. The Italian Space Agency (ASI)/Light Italian CubeSat for Imaging of Asteroids (LICIACube) witnessed the event in situ. In this work, we used images from both Didymos Reconnaissance and Asteroid Camera for Opnav (DRACO) and LICIACube Explorer Imaging for Asteroid (LEIA) instruments on board the two spacecraft to search for small objects that may be present around the primary before the impact, to provide hints on the complete dynamical characterization of the system. This will be compared to the future environment the European Space Agency (ESA)/Hera mission will encounter in late 2026. We found no unknown objects larger than ∼50 m in the entire Hill sphere. When considering closer regions with respect to the primary object, the limiting size gets smaller, reaching a minimum diameter equal to ∼2 m within a radial distance of ∼2 km from Didymos. Despite the dynamical environment in the system being extremely perturbed and unstable, there is still a small chance that large objects could find a stable niche in the phase space of the Didymos–Dimorphos system, but the null result of our work is a strong indication that this niche is either nonexistent or empty.