I read somewhere that flexible arrays tend do waver when a satellite is rotated so it would make Earth observing satellites have 'fuzzy' pictures. But I also read that Hubble used a flexible array for its panels, which suggests that's a non issue.

Are there mission cases where flexible arrays are a problem? If not, is the choice to use flexible vs rigid a matter of $$ or is there something else?

  • 2
    $\begingroup$ Note in space there's no air resistance to extinguish any harmonic motion quickly. It takes a long time for vibrations/oscillations to dissipate as heat in the vibrating material. It's why any tether/rope based systems misbehave terribly too. $\endgroup$
    – SF.
    Jan 15, 2020 at 17:56
  • 1
    $\begingroup$ rigid are cheaper and lighter (hence cheaper) and more robust (hence less redundancy (hence cheaper and lighter (hence cheaper))). However they do take up more space (which means you lose space for you payload, which means it's less cost effective, or require folding mechanisms, which add weight, complexity and reliability concerns $\endgroup$
    – user20636
    Jan 15, 2020 at 18:21

1 Answer 1


Your assumption that flex arrays were a non-problem for Hubble is incorrect.

The original arrays "jittered" every time the 'scope entered or left eclipse, causing problems for the pointing system.

It was so bad that the arrays were completely swapped out for redesigned ones on the first servicing mission, and then replaced by stiffer ones on a later servicing mission. (thanks to JCRM for reminding me of the 1st replacement)

The Solar Array-Induced Disturbance of the Hubble Space Telescope Pointing System

original arrays

enter image description here

Image reference

Current, stiffer arrays

enter image description here

Image reference

  • $\begingroup$ wasn't the first set of replacements flexible as well? which suggests the problem wasn't so bad they were swapped. However, when they were replaced the second time they were replaced with "more robust" rigid ones which alleviated the jitter problem problem $\endgroup$
    – user20636
    Jan 15, 2020 at 16:57
  • $\begingroup$ further information -- IIRC, it was the failure to recover the first set of panels which led to the third set being rigid (no point accepting the problems with flex if you didn't get the benefits) $\endgroup$
    – user20636
    Jan 15, 2020 at 17:04
  • $\begingroup$ Actually, the first set of replacements was also redesigned to fix the jitter problem. "Initial flight data following the HST refurbishment mission in December 1993 indicated that the redesigned solar arrays considerably reduced the disturbances of the pointing control system." (from the reference) The first ones were...bad. $\endgroup$ Jan 15, 2020 at 17:27
  • $\begingroup$ Yes, they were, as explained in the link. But in both cases they were replaced because they reached the end of their design life. So the jitter problem was bad enough to cause a redesign, but not bad enough to cause them to be replaced. So yes, they were a problem, but not necessarily as bad a problem as your wording suggests. The revised flexible panels "survived" servicing missions 2 and 3 (a & b) after all. $\endgroup$
    – user20636
    Jan 15, 2020 at 18:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.