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(Phys Org2)   Hubble's refusing to get on the orbital cart   (phys.org) divider line
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909 clicks; posted to STEM » on 21 Jun 2022 at 12:05 PM (15 weeks ago)   |   Favorite    |   share:  Share on Twitter share via Email Share on Facebook



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2022-06-21 11:31:56 AM  
But remember, god is watching you touch yourself

/keep on keeping on Hubble, I met the guy who fixed your mirror
 
2022-06-21 12:29:38 PM  
So, what is the plan when the time does come? Does it have enough go juice left to de-orbit? If the gyros all fail and it cannot orient itself, can it still be maneuvered?
 
2022-06-21 12:50:23 PM  
From googling "hubble gyroscope":

The Status of Hubble's Gyros
Gyros have limited lifetimes and need to be replaced periodically. Currently, three of the six gyros are working.
In 2005 Hubble began operating in two-gyro mode. With two useable spare gyros, Hubble's operating life can be extended and thus Hubble's science observations can continue uninterrupted until SM4.

History of Gyro Replacement
Four new gyros were installed on Hubble in 1993 and all six gyros were replaced in 1999. During SM4 in 2008, astronauts will replace all six gyros, which are nearing the end of their projected useful life.

2022-2008= 14 year old gyros, which "near the end of their projected useful life" at 9 years.  And this isn't like the Mars rovers, space probes that need gyros die when the gyros wear out.  I think once they get down to two they'll have to send it down to Point Nemo in the Pacific Ocean (it is the point furthest from land and not even on the shipping lanes).
 
2022-06-21 1:09:06 PM  

whitebuffaloburgers: So, what is the plan when the time does come? Does it have enough go juice left to de-orbit? If the gyros all fail and it cannot orient itself, can it still be maneuvered?


No. The spacecraft itself has no propulsion, the servicing missions would raise its orbit before release. Pointing is by a combination of reaction wheels and magnetic torquers, the latter used mostly to desaturate the reactions wheels when needed. The original plan was to return the spacecraft via a shuttle flight, but with the Shuttle gone, that's now impossible.

The last servicing mission installed a capture mechanism (basically, a docking port) that would allow another spacecraft to attach and deorbit it. A controlled reentry is better because they can make sure it doesn't hit anything - the mirror, in particular, is likely to survive reentry mostly intact, so dropping it into the South Pacific Ocean would be nice. They could, theoretically, attach a booster to raise the orbit for now and have it hang on to lower the orbit later, but that would affect pointing.

When HST deorbits naturally is uncertain, because solar activity affects the atmosphere and changes the drag the telescope encounters. Worst case is in 2028, best case is in 2041.

The Nancy Grace Roman Space Telescope will take over from HST at visible wavelengths, but it's a wide field scope. JWST is shortly going to completely supplant it, but is near/mid-IR, not visible.

I'm unaware of a mission to directly replace HST as a narrow-view optical observatory, but that doesn't mean it doesn't exist....it means I'm not aware. There are a lot of space observatories in the works.
 
2022-06-21 1:20:38 PM  
It's something in orbit that still works. It's a medium orbit, so it's not getting in anybody's way. We're not putting up bus sized satellites for spy work every few months like in the 1980s anymore. It's easier to put a bunch of cube sats to do that work.
 
2022-06-21 4:22:18 PM  

wildcardjack: It's something in orbit that still works. It's a medium orbit, so it's not getting in anybody's way. We're not putting up bus sized satellites for spy work every few months like in the 1980s anymore. It's easier to put a bunch of cube sats to do that work.


Easier yes, but not better.  There's a LOT of debris up there, and deploying new satellites by the dozens/hundreds isn't doing anything to curtail that trend.
 
2022-06-21 4:30:17 PM  

wildcardjack: It's something in orbit that still works. It's a medium orbit, so it's not getting in anybody's way. We're not putting up bus sized satellites for spy work every few months like in the 1980s anymore. It's easier to put a bunch of cube sats to do that work.


For astronomy, aperture is everything, for optical astronomy, aperture area is everything squared, which is why JWST had that complicated deployment sequence, so they could get that large a mirror into space.
 
2022-06-22 1:26:54 PM  
Mmm, now I'm hungry for gyros.
 
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