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According to eyes on the solar system, Dimorphos is tidally locked to Didymos.

If DART impact direction is perfectly aligned with Dimorphos center of mass, all of the momentum transfers into orbital period shortening, and none of it into disturbing Dimorphos' rotation rate.

As SE - stop firing the good guys correctly pointed out, even if rotation is not changed by impact at first, orbital period is, and it will change rotation rate ultimately.

Was DART planned to hit dead center the most accurately so that most energy slows Dimorphos without changing at first its rotation rate? Or was a ratio of impact energy dedicated to create a bigger rotational perturbation, by purposefully missing the center of mass' bullseye?

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    $\begingroup$ Will point to the Planetary Science Journal special issue on "The DART and Hera Missions and the Didymos System Pre-arrival" where there are several papers (all open access) on the dynamics and the overview paper (Rivkin et al 2021) $\endgroup$ Sep 29 at 14:00
  • $\begingroup$ I will try and find the resource, but I recall there being a moderate declination angle (~30°) between DART's arrival and Didymos' orbital plane, so some energy is lost to changing its plane $\endgroup$ Sep 29 at 23:34
  • $\begingroup$ This was a technology demonstration mission. No organization ever had hit an asteroid with a spacecraft at a somewhat high velocity before. It's not surprising that a demo mission such as this aimed for dead center. $\endgroup$ Oct 3 at 6:35
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    $\begingroup$ One would think they aimed for center simply because that maximizes the probability of hitting the thing. Nobody knows with any real certainty how these sorts of objects react to being hit (that's the point of the mission!), I would assume they just wanted to hit the thing and collect the resulting data. Then, on future missions, you can start testing theories like "hitting it here with x velocity and y angle will result in z changes to orbit trajectory". $\endgroup$
    – eps
    Oct 5 at 23:03

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