Orbital and Physical Characterization of Asteroid Dimorphos Following the DART Impact

0585247 - ASÚ 2025 US eng J - Journal Article
Naidu, S.P. - Chesley, S.R. - Moskovitz, N. - Thomas, C. - Meyer, A.N. - Pravec, Petr - Scheirich, Peter - Farnocchia, D. - Scheeres, D.J. - Brozovic, M. - Benner, L. A. M. - Rivkin, A. S. - Chabot, N. L.
Orbital and Physical Characterization of Asteroid Dimorphos Following the DART Impact.
The Planetary Science Journal. Roč. 5, č. 3 (2024), č. článku 74. E-ISSN 2632-3338
R&D Projects: GA ČR(CZ) GA20-04431S
Institutional support: RVO:67985815
Keywords : near-Earth objects * asteroid satellites * asteroid dynamics
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 3.4, year: 2022
Method of publishing: Open access

The Double Asteroid Redirection Test (DART) mission impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos, on 2022 September 26 UTC. We estimate the changes in the orbital and physical properties of the system due to the impact using ground-based photometric and radar observations, as well as DART camera observations. Under the assumption that Didymos is an oblate spheroid, we estimate that its equatorial and polar radii are 394 +/- 11 m and 290 +/- 16 m, respectively. We estimate that the DART impact instantaneously changed the along-track velocity of Dimorphos by2.63 +/- 0.06 mm s-1. Initially, after the impact, Dimorphos's orbital period had changed by32.7 minutes +/- 16 s to 11.377 +/- 0.004 hr. We find that over the subsequent several weeks the orbital period changed by an additional 34 +/- 15 s, eventually stabilizing at 11.3674 +/- 0.0004 hr. The total change in the orbital period was33.25 minutes +/- 1.5 s. The postimpact orbit exhibits an apsidal precession rate of 6.7 +/- 0.degrees 2 day-1. Under our model, this rate is driven by the oblateness parameter of Didymos, J 2, as well as the spherical harmonics coefficients, C 20 and C 22, of Dimorphos's gravity. Under the assumption that Dimorphos is a triaxial ellipsoid with a uniform density, its C 20 and C 22 estimates imply axial ratios, a/b and a/c, of about 1.3 and 1.6, respectively. Preimpact images from DART indicate Dimorphos's shape was close to that of an oblate spheroid, and thus our results indicate that the DART impact significantly altered the shape of Dimorphos.
Permanent Link: https://hdl.handle.net/11104/0353511