Creating a Library of Potential DART Impact Ejecta Scenarios using the Rebound Ejecta Dynamics Package

The NASA Double Asteroid Redirection Test (DART) mission is set to impact Dimorphos, the binary component of the Didymos asteroid system, in July 2022. One primary goal of this mission is to improve our understanding of impact momentum transfer. Related modeling and evaluation of this transfer efficiency parameter can be applied to future experiments of hypervelocity impacts onto asteroids. One of the key components in impact momentum determination is the subsequent behavior of impact ejecta. To support this objective, we create a library of approximately 200 ejecta scenarios, which are based on differing impact and environmental conditions, by using our newly created Rebound Ejecta Dynamics package - RED (Larson and Sarid 2020). This package builds on the Rebound N-body integrator (Rein and Liu 2012) and can be straightforwardly applied in the same manner Each simulation contains at least 10⁴ particles and a combination of at least two of the following effects: radiation pressure on the ejecta, gravitational field in a binary asteroid system, rotation of the target body, and non-spherical shape of the target body. Testing a DART-like impact with varying combinations of effects builds a baseline to determine which effects are dominant in each simulation. We then vary the “impact” site, target body rotation period, ejection velocity, target body axes ratio, and ejecta particle size distribution. From these simulations, we create maps of where the ejecta particles are expected to travel and land on the surface of either Didymos or Dimorphos. This assists with DART impact planning to ensure the safety of the spacecraft and to locate the optimal impact configuration to alter Dimorphos’s orbital period. Additionally, each impact configuration can be characterized by a momentum transfer efficiency parameter that describes the transfer of momentum from the impactor to the target body. Our library of ejecta scenarios will be crucial to post-impact analysis and will allow us to associate a momentum transfer efficiency parameter with the impact event by comparing observations of the event to solutions in the library.