We present recent science highlights of the Arecibo Observatory’s planetary radar project from 2019-2020. The Arecibo Observatory in Puerto Rico is a key facility for post-discovery characterization of near-Earth asteroids (NEAs) and for studies of celestial bodies from Mercury out to the icy moons of Saturn. The 2.38-GHz planetary radar system actively contributes to the investigation of physical and dynamical properties of NEAs by high-precision characterization of up to 120 NEAs annually. Planetary radar observations offer unparalleled imaging capabilities of NEAs that can directly reveal their shape, surface morphology, spin, and binarity. Furthermore, radar data can provide clues to the NEAs’ geology and near-surface physical properties at centimeter-to-decimeter size scales. These characteristics are invaluable information for understanding the formation and evolution of NEAs, the building blocks of our Solar System, for evaluating impact risk and developing impact mitigation technologies, and for ensuring safe spacecraft encounters.
Some of the recent science highlights include discovery of the binary natures of 2020 BX12 observed in January 2020 and 2016 AZ8 observed in January 2019, craters and hills on the surfaces of (52768) 1998 OR2 observed in April 2020 and (68950) 2002 QF15 observed in June-May 2019, and the removal of the 1-km sized asteroid 2020 NK1 from the Center for Near-Earth Object Studies Sentry list (and other virtual impactor lists) as a direct result of the radar observations on July 31. Before the radar observations, 2020 NK1 was third on the Sentry list of cumulative Palermo rating, and the only asteroid with a non-zero Torino rating. We present preliminary physical characterization of these and other recently radar-observed NEAs including sizes, spin periods, and radar albedos (indicative of the near-surface density), and any physical features visible in the radar images. See also the abstracts by Devogèle et al. on 1998 OR2, Venditti et al. on 2020 NK1, and López-Oquendo et al. on contact binary 2015 JD1.