Watching this video 2024 solar eclipse shadow seen from space by satellites and space station of a satellite capturing video footage of moon's shadow on Earth during eclipse.

The accelerated footage shows the solar panel tracking the sun and also some oscillation of the solar panel, what causes that oscillation?

How are panels actuated on satellites that require stable attitude?


1 Answer 1


If you observe the linkage angles and visual overlap of the various components, you can see that there is some form of automated movement, extending the panel. The scissors joint at the main body slowly closes.

Allowing for the time-lapse/speedup aspect of the video, the movement appears as a wobble. One might expect there to be some latitude allowed for out-of-plane movement that is exaggerated by the time-lapse.

If that portion of the video is not time-lapse, I think the extension of the panel may still account for the wobble.

  • $\begingroup$ is this due to some mechanical backlash from scissor actuating motor? $\endgroup$
    – user19132
    Apr 10 at 15:52
  • 2
    $\begingroup$ Just about anything that moves has backlash and it's cumulative. Of course, everything has inertia as well. A command to extend the scissors mechanism followed by a stop command will create a bit of bobble. This could be amplified by the bearings or bushings at the pivot points. I believe unless one locates an engineer who designed and tested the mechanism, it's going to be conjecture. $\endgroup$
    – fred_dot_u
    Apr 10 at 17:09
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    $\begingroup$ Since the torque is applied to both the panel and the body of the Starlink satellite, they both move. There may be some lag before the attitude control system re-adjusts the pointing of the body of the spacecraft, and there may be some digital processing that keeps the image of the Earth from revealing this motion. All together, those could also potentially result in this visual behavior in the final, processed video. $\endgroup$
    – uhoh
    Apr 10 at 20:03
  • $\begingroup$ @user721108 Starlink satellites are for communications. They don't have dish antennas, they use phased arrays which can be electronically steerable at very high speed without any mechanical motion. For satellites with fixed-beam antennas like the older communications satellites up in geostationary orbits, they do rotate the panels but slowly and very smoothly - once a day. And they have stabilized the total angular momentum so that the body of the spacecraft always points towards Earth while the panels always point towards the Sun. $\endgroup$
    – uhoh
    Apr 10 at 20:32
  • 3
    $\begingroup$ I don't think the scissor thing is extending, it is just rotating so the space inside appears smaller. $\endgroup$ Apr 11 at 1:46

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