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Libration and Orbit Period Variation in Didymos Following the DART Impact

Presentation #113.03 in the session “Didymos: Throwing DARTs”.

Published onOct 03, 2021
Libration and Orbit Period Variation in Didymos Following the DART Impact

The DART spacecraft will impact Dimorphos, the secondary in the Didymos binary asteroid system, to demonstrate the validity of a kinetic impactor in deflecting a potentially hazardous asteroid. The impact will perturb the binary asteroid’s angular momentum, causing the secondary to begin librating in its orbit. Due to the spin-orbit coupling characteristic of binary asteroid systems, the libration will have an effect on Dimorphos’s orbit, causing the orbit period to fluctuate over time. The non-constant orbit period is driven by two modes, a short-period and a long-period, each with significant amplitudes on the order of tens of seconds and periods on the order of days and months, respectively. Impacts with a larger angular momentum transfer result in a larger libration amplitude and greater variations in the non-constant orbit period. Furthermore, the post-impact dynamics are also dependent on the size of Dimorphos and the initial configuration of the binary system relative to a synchronous equilibrium. The non-constant orbit period offers both a challenge and an opportunity to the DART mission: the oscillations will make measuring the orbit period to a high degree of accuracy more difficult, but can help constrain the libration state and momentum transfer of the impact.

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