The Roman Space Telescope as a Planetary Defense Asset

Abstract: NASA's Nancy Grace Roman Space Telescope, slated to launch in October 2026, will serve a critical role in the characterization and threat assessment of near-Earth Objects (NEOs), thus contributing to national and international planetary defense objectives. Operating from the Earth-Sun L2 point and observing in the near-infrared, Roman has the high sensitivity and high spatial resolution needed to measure the physical properties, compositions, and orbital trajectories of NEOs in order to understand their physical nature and potential hazards to Earth. Roman's planetary defense capabilities complement those of two wide-field survey missions: the now operational ground-based Vera C. Rubin Observatory's Legacy Survey of Space and Time and the upcoming space-based NEO Surveyor. Rubin, observing in visible light, will discover over 100,000 NEOs. NEO Surveyor, observing in the mid-infrared where NEO thermal emission peaks, will detect 200,000-300,000 NEOs, some as small as ~20 meters in diameter. With investment in developing the pipeline infrastructure required to extract information from moving target streaks, Roman will be able to observe NEOs down to the smallest sizes in order to improve our measurements of NEO orbits by 2-3 orders of magnitude, enable accurate diameter and albedo estimates in conjunction with NEO Surveyor, and reveal the spectral types and bulk compositions of the smallest NEOs. Together, these three US-led facilities will operate across the electromagnetic spectrum to form a comprehensive planetary defense network.