Near-Earth Object Characterization Using Ground-Based Radar Systems

Abstract

Ground-based planetary radar systems are a crucial tool for post-discovery high-precision astrometry and physical characterization of near-Earth asteroids and comets. Radar ranging and imaging capabilities exceed those of any other ground-based instruments. As described in more detail in the Decadal white paper (henceforth WP) Mainzer et al. and WP Taylor et al., detection and characterization of potentially hazardous asteroids was mandated by the US Congress through George E. Brown, Jr. Near-Earth Object Survey Act in 2005. While optical telescopes survey for new asteroid detections, post-discovery characterization using planetary radar can secure the heliocentric orbit information, extending the interval of reliable orbit estimation by decades to centuries for most objects and preventing recently-discovered objects from being lost. Radar observations also provide constraints on the object’s size, rotation state, morphology, satellites, and near-surface geology as well as regolith properties, making ground- based radar systems a powerful, low-cost complement to spacecraft destined for specific targets. Furthermore, they can be used for characterizing the nuclei of comets, which are typically obscured by the dust coma at optical wavelengths, and probe the decimeter-scale coma particle abundance, which is relevant especially for the study of disintegrating comets. These characteristics are invaluable information for understanding the formation and evolution of asteroids and comets, which are the building blocks of our Solar System, for evaluating impact risk and developing impact mitigation technologies, and for ensuring safe spacecraft encounters. In the next decade, in addition to continuing as a state-of-the-art astrometric tool for planetary defense, we expect ground-based radar observations to expand our knowledge of the physical characteristics of the near-Earth asteroid population in terms of their shape, binarity, and near-surface structure. We recommend that facilities with ground-based radar systems, planetary radar programs, and research and analysis of radar observations receive full support from NASA and NSF to ensure their availability to the planetary science community and as a resource for planetary defense initiatives through the next decade.