It's amazing how much redundancy was built into those out-of-touch systems, 30 years ago.
However, the number of backup units is finite, so let's hope the now-operating system can last for several more decades.
>> Hubble’s operators initially thought a memory module was at fault but switching to one of three backup modules produced the same error.
Apparently Hubble has 4 memory modules which are switchable! I'd love to see how that works. Actually, I'd be fascinated to get a walkthrough of the overall architecture. It might give insights for how we keep business continuity by first accepting that hardware and software will fail.
Fig 5-10 is the Data Management Subsystem
https://asd.gsfc.nasa.gov/archive/sm3a/downloads/sm3a_media_...
Concerning the computers:
- First they had a DF-224 flight computer and a
- Science Instrument Control and Data Handling (SI C&DH)
Initially DF-224 between missions got installed a coprocessor:
https://asd.gsfc.nasa.gov/archive/hubble/a_pdf/news/facts/Co...
During another servicing mission they replaced it with something called the Advanced Computer with Intel 80486:
https://asd.gsfc.nasa.gov/archive/hubble/a_pdf/news/facts/FS...
There are some 50,000 lines of code in the C and Assembly programming languages. https://www.nasa.gov/pdf/327688main_09_SM4_Media_Guide_rev1....
They also have a Help Desk...
"Welcome to the Hubble Space Telescope Help Desk"
"There's a backup module, with an override command to activate it, but it won't work with the system down. You'll have to use the manual override switch - on the telescope."
I found one discussion from 7 years ago
“… I think we should start a more extensive national unmanned space program. For example, if the Hubble, or its replacement, needs to be fixed, we should have an unmanned answer, for instance.”
Plus you'd still need spare parts. Why would I build a robot to swap parts, when I can simply put all of the spare parts into the telescope and swap over to them electronically?
Also, the vision is that robots can build on Mars, for example.
“Simply” means fund the research. My comment was from 7 years ago.
We also need the robots here on earth for dangerous tasks
We’d make impressive progress over each decade with more effort.
What if the system that swaps parts fails?
Send up another [improved] robot. These missions are less costly than human missions. We get to iterate more often
Says who? And how? This seems like an unsubstantiated claim.
Launching to space is severely constrained by the mass you can bring up. You can send up multiple robots compared to the mass needed for all the food, life support ect, for a single person.
So again, [citation needed]. We don't have, and are no where close to, general purpose miniature lightweight robots, after all.
Touche. At least you can send another robot!
But in reality, the ideal system is probably a combination of built-in redundancy / spares for parts that can work that way; and then robots for the kinds of things that are too complicated to have a built-in failover.
The other thing to remember was that Hubble was designed in an era that the Space Shuttle was meant to make manned missions to repair / upgrade commonplace. My understanding is that this was actually done at least once to Hubble (maybe more? I forget); but unfortunately for Reasons, NASA turned out to be incapable of resisting cutting corners which put people's lives at risk (Challenger, Colombia). A system designed today would be designed assuming that it would be robots or nothing.
https://www.nasa.gov/mission_pages/hubble/servicing/index.ht...
Huble was never meant for this, if you look at all the systems present on ISS for automated docking, none of that is on Hubble. Access to modules inside Hubble was never meant for robots with very limited dexterity either. Being able to do something like that would be a huge feat of engineering in my opinion (and extremely expensive).
I am fairly certain it would be faster and cheaper to just build a new one from scratch.
And even if you managed to make a robot to service Hubble, it then would only be able to service Hubble and nothing else. JWT for example is completely different.
On the long term you are right that this is a capability we need, but this needs to be taken into consideration while building the telescope/satellite/whatever: automated docking mechanism, standard ports and dimension of parts etc. etc.
So the idea is that you don't need to specialize it to the thing it's meant to work on, because it works on whatever a human works on. A similar idea drove a lot of the DARPA Robotics challenge, with its emphasis on being able to drive a normalish vehicle, open a door, climb a ladder, use a regular power tool, etc.
Anyway, I think the state of the art for all this is still pretty far away, which is why the instinct is to assume we're talking about something specialized.
Yes, that's exactly what I thought. If we are talking about AGI + human level robotic dexterity, then the use of "simply" becomes even funnier.
It was also never meant for humans with less limited dexterity.
I recall one of the Hubble servicing missions I watched on NASA TV, in which they had to bolt a special adapter plate over a cover, unscrew over a hundred tiny non-captive screws (which the adapter plate was designed to catch, so they wouldn't float away), and only then could they open that cover. That part of the telescope clearly wasn't designed to be serviced in space.
Edit:saw the comment somewhere that it is 15 years.
It would make sense to start working on a replacement for Hubble, even if that means it'll be ready in 20 years.
At a minimum you're outside of "smallsat" size range. Even building a lot of them the precision manufacturing of the optics and steering systems require a lot of ground based testing, calibration, and qualification. Between the size and precision even your "cheap" Hubble's aren't all that cheap.
The second problem is terrestrial telescopes have gotten really good and are far cheaper for any given mirror size. Their instrumentation doesn't have nearly the same mass restrictions and can be swapped out routinely.
Space telescopes make sense when their mission requires them to be space based like observing wavelengths that don't reach the surface of Earth.
The general problem of repairing Hubble robotically is unlikely to be solvable within the lifetime of the telescope, but future devices could be designed with that in mind.
Is the answer is that NASA doesn't know how to build them anymore? Or that it's not politically feasible?
"Just" is being extensively overused in this thread.
When operating multiple devices to improve reliability, diversity is one point.
JWST has a docking port for a future robotic servicing mission.
Nancy Grace Roman (formerly WFIRST) space telescope has grappling points on the spacecraft for robotic servicing.
The NRO did donate two unlaunched telescopes to NASA in 2012 (with optics present but sans electronics), which still have not yet been retrofitted and launched.