Estimation of the Heliocentric Momentum Enhancement from a Kinetic Impact: The Double Asteroid Redirection Test (DART) Mission

The NASA Double Asteroid Redirection Test (DART) has demonstrated the capability of successfully conducting kinetic impact-based asteroid deflection missions. The changes in the Didymos-Dimorphos mutual orbit as a result of the DART impact have been measured. To fully assess the heliocentric outcome of deflection missions, the heliocentric momentum enhancement parameter, β⊙, needs to be determined and disentangled from other non-gravitational phenomena such as the Yarkovsky effect. Here, we explore the measurability of β⊙ resulting from DART, which we estimate simultaneously with non-gravitational accelerations using a least squares filter. Results show that successful stellar occultation measurements of the Didymos system in the second half of 2024 in addition to the ones in the 2022-2023 campaigns can achieve a statistically significant estimate of β⊙, with an uncertainty slightly above 20% for an assumed β⊙ = 3. Adding additional occultation measurements and pseudo- range measurements from the Hera spacecraft operations at Didymos starting in 2027 decreases this relative uncertainty to under 6%. We find that pre-impact occultation observations combined with post-impact occultations would have yielded substantially higher signal-to-noise ratios on the heliocen- tric deflection. Additionally, pre-impact occultations would have also enabled a statistically significant β⊙ estimate using only one additional occultation in September 2023. Therefore, we conclude that future asteroid deflection missions would greatly benefit from both pre- and post-deflection occultation measurements to help assess the resulting orbital changes.