Observations in support of the DART mission: Understanding the Didymos-Dimorphos binary system

The binary near-Earth asteroid (65803) Didymos is the target of NASA’s DART (Double Asteroid Redirection Test) mission, the first demonstration of asteroid deflection by a kinetic impactor. The DART spacecraft will impact Dimorphos (the secondary in the Didymos system) in late September 2022 and modify its orbit through momentum transfer. Since 2015, the Observations Working Group has been obtaining photometric lightcurves of the system in order to understand the baseline, unperturbed orbital period of the secondary. We were tasked with characterizing the Didymos-Dimorphos system properties with sufficient accuracy to determine the time of impact and to measure the post-impact change in the Dimorphos orbital period to within 7.3 seconds. This measurement goal is a small, but observable fraction of the current orbital period of the satellite (Porb=11.92 hours). Due to our extensive lightcurve observing effort, Didymos is now the best understood binary near-Earth asteroid. We are using our current knowledge of the system to design a series of observations in 2022 to determine the post-impact orbital period, observe the ejecta at the time of impact and in the weeks following, and obtain spectra to improve our understanding of the composition of the system. I will discuss our recent lightcurve observations (2020-2021), our current understanding of the state of the system, possible outcomes of the impact, and our preliminary plans for pre- and post-impact observations later this year.

Speaker: Cristina Thomas Denney, Northern Arizona University