Dimorphos orbit determination from mutual events photometry

Abstract

The NASA Double Asteroid Redirection Test (DART) spacecraft successfully impacted the Didymos-Dimorphos binary asteroid system on 2022 September 26 UTC. We provide an update to its pre-impact mutual orbit and estimate the post-impact physical and orbital parameters, derived using ground-based photometric observations taken from July 2022 to February 2023. We found that the total change of the orbital period was $-33.240\pm 0.072$ min. (all uncertainties are 3$\sigma$). We obtained the eccentricity of the post-impact orbit to be $0.028\pm 0.016$ and the apsidal precession rate of $7.3\pm 2.0$ deg./day from the impact to 2022 December 2. The data taken later in December to February suggest that the eccentricity dropped close to zero or the orbit became chaotic approximately 70 days after the impact. Most of the period change took place immediately after the impact but in a few weeks following the impact it was followed by additional change of $-27_{-58}^{+19}$ seconds or $-19\pm 18$ seconds (the two values depend on the approach we used to describe the evolution of the orbital period after the impact -- an exponentially decreasing angular acceleration or an assumption of a constant orbital period, which changed abruptly some time after the impact, respectively). We estimate the pre-impact Dimorphos-Didymos size ratio was $0.223\pm 0.012$ and the post-impact is $0.202\pm 0.018$, which indicates a marginally significant reduction of Dimorphos' volume by ($9\pm 9)\%$ as the result of the impact.

31 pages, 7 figures

References in corpus (5)

• Successful Kinetic Impact into an Asteroid for Planetary Defense
• Orbital Period Change of Dimorphos Due to the DART Kinetic Impact
• The Excited Spin State of Dimorphos Resulting from the DART Impact
• The binary near-Earth asteroid (175706) 1996 FG3 - An observational constraint on its orbital evolution
• The Dimorphos Boulder Swarm

Cited by in corpus (8)

• The Dynamical State of the Didymos System Before and After the DART Impact
• The Hera Radio Science Experiment at Didymos
• The Yarkovsky effect on the long-term evolution of binary asteroids
• Delivery of DART Impact Ejecta to Mars and Earth: Opportunity for Meteor Observations
• The binary Yarkovsky effect on the primary asteroid with applications to singly synchronous binary asteroids
• HyperScout-H: the hyperspectral imager for the ESA Hera mission
• A change of the rotation period of asteroid (65803) Didymos caused by the DART impact
• In-flight calibration of ESA Hera's HyperScout-H imager