The Double Asteroid Redirection Test (DART) mission is NASA’s planetary defense technology demonstration mission set to launch later this year. The DART spacecraft will impact the secondary, Dimorphos, of the (65803) Didymos binary asteroid system and alter the mutual orbit. In addition to the momentum imparted by DART, ejecta coming off Dimorphos and escaping the system will cause a momentum enhancement characterized by the momentum enhancement factor, β, that would also affect the heliocentric orbit of the entire Didymos system.
Since the Didymos system has close approaches with the Earth in the next century, a change in its heliocentric orbit affects Didymos-Earth close approach parameters. In this contribution we present our latest results on how DART affects the system’s heliocentric orbit through changes in these close approach parameters. Using the current mission design specifications, we confirm that there is no significant increase in the risk of a collision between the Earth and the Didymos system due to DART.
However, since ejecta are likely escaping the system for weeks after impact, we find that there is a small but significant difference in modeling the DART impact as a singular impulse that accounts for the cumulative ejecta momentum contributions as opposed to multiple smaller impulses caused by ejecta escaping the system.
Thus, measuring the β-factor with respect to the entire Didymos system would open a new window into interpreting the results of the DART mission, since it could yield additional insights into ejecta momentum transport that would be relevant for future planetary defense initiatives. In order to determine whether the heliocentric orbit deflection is measurable in principle, we performed self-consistent batch least squares simulations to estimate β using a combination of radar and astrometry observations. By combining existing observations with proposed campaigns including occultation measurements, as well as observations by ESA’s Hera mission, we find that the heliocentric β could be accurately estimated as a multiplier along the DART impact velocity vector.