Are satellites moved to keep them aligned? Are they at risk of becoming unusable from the small, but measurable changes to Earth's rotation?
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5$\begingroup$ Geosynchronous satellites already maneuver regularly to cancel out a wide variety of different gravity effects on much shorter timescales. Search on the term "station keeping" for more details, as in space.stackexchange.com/questions/40673 space.stackexchange.com/questions/43570 space.stackexchange.com/questions/28297 space.stackexchange.com/questions/36465 space.stackexchange.com/questions/26269 space.stackexchange.com/questions/4764 space.stackexchange.com/questions/37441 space.stackexchange.com/questions/33169 $\endgroup$– Ryan CCommented Oct 8, 2022 at 0:02
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$\begingroup$ @RyanC question is about changes in Earth's rotational speed, not about loss of station-keeping $\endgroup$– uhohCommented Oct 9, 2022 at 21:22
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$\begingroup$ @uhoh and the answer is that this is just one more miniscule unmodeled perturbation among many , which are all handled in passing without difficulty by the same ordinary station keeping efforts that are used to deal with much larger sources of error. $\endgroup$– Ryan CCommented Oct 10, 2022 at 18:07
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$\begingroup$ @RyanC so why close the question as a duplicate of a question about stable equilibrium points when the answer to this question his here on this page and not there? Why point future readers away to a different page instead of to DavidHammen's excellent answer right here on this page? It seems to me that the answer-blocking close voting of this question is unproductive and deleterious rather than helpful. $\endgroup$– uhohCommented Oct 10, 2022 at 21:41
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The very small changes in the Earth's rotation rate pale in comparison to the much larger perturbations that geosynchronous satellites experience from the Earth's non-uniform gravitational field, gravitational perturbations from the Moon and the Sun, and non-gravitational perturbations (radiation pressure) from the Sun.
In addition to the above, the ability of a geosynchronous satellite to hold its position is imperfect. Because of those perturbations and the not quite perfect control, geosynchronous satellites are assigned a longitude band in which they must operate, as opposed to exactly hovering over a specific point. The tiny changes in the Earth's rotation rate is yet another perturbation that geosynchronous satellites must accommodate to stay within their assigned bands, but this is a tiny perturbation, essentially in the noise.
answered Oct 9, 2022 at 8:59