Anticipating the DART Impact: Orbit Estimation of Dimorphos Using a Simplified Model

Abstract We used the times of occultations and eclipses between components 65803 Didymos binary system observed in its light curves from 2003 to 2021 estimate orbital parameters Dimorphos relative Didymos. employed a weighted least-squares approach modified Keplerian orbit model order accommodate effects nongravitational forces such as YORP that could cause linear change mean motion over time. period mutual at epoch 2022 September 26.0 TDB, day DART impact, is 11.921 487 ± 0.000028 hr (1 ? ) changing rate (5.0 1.0) × 10 ?18 rad s ?2 ). The formal 3 uncertainty phase during planned Double Asteroid Redirection Test (DART) mission 5.°4. Observations July September, few months days prior should provide modest improvements reduce it about 4.°2. These results, generated using relatively simple model, are consistent with those more sophisticated Scheirich & Pravec, which demonstrates reliability our method adds confidence these mission-critical results.