Arecibo Observatory: a ground and space joint effort in support of small bodies exploration

We present how the planetary radar program at the Arecibo Observatory (AO) works in synergy with other ground-based and space telescopes, as well as planetary mission support. The AO's S-band radar system (2.38 GHz, 1 MW) is crucial for orbit refinement and characterization of near-Earth asteroids (NEAs), providing information about shape, spin, size, surface properties, and revealing natural satellites. Radar observations rely on optical and space infrared NEA surveys, allowing for rapid post-discovery orbit refinement, which can decrease orbit uncertainty and extend the predictability window. Furthermore, missions to small bodies use radar characterization to select suitable targets, such as NASA's OSIRIS-REx to 101955 Bennu, and JAXA's Hayabusa to 25143 Itokawa. The upcoming NASA's DART mission, part of the pioneer international collaboration AIDA, will test the kinetic impact on the secondary component of the binary system Didymos in 2022, becoming the first asteroid mitigation strategy performed. AO's radar system can measure speed and distance with incomparable precision, and will be actively supporting this deflection mission for a few weeks after the impact in real time.