Orbital Capture of Ejecta into Periodic Orbits around Binary Asteroid (65803) Didymos

The successful impact of the Double Asteroid Redirection Test (DART) spacecraft on Dimorphos enabled the first-ever extensive observation of a postimpact ejecta tail from a binary asteroid system. Studying the ejecta can provide insights into impact physics and asteroid composition and inform future asteroid missions. In this research, the orbital capture of the impact ejecta around the Didymos binary asteroid system is investigated. The ejecta dynamics are described using an augmented bicircular restricted four-body model, which incorporates the binary’s irregular gravity field and solar radiation pressure (SRP) acceleration. Typical periodic orbit (PO) families, including planar Lyapunov and terminator orbits, are selected as the candidates for capture analysis. The candidate POs are perturbed and backward-propagated using the invariant manifold theory, and eligible trajectories intersecting the asteroids’ surfaces are recorded. The ejecta characteristics of different POs are summarized from three principal aspects: ejection location, ejection velocity, and ejection angle. The influence of two critical factors is qualitatively assessed, including the geometry of the asteroids in the binary system and the strength of SRP acceleration. Lastly, the likelihood for the ejecta from the DART impact being transferred to candidate POs is assessed.