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IIRC the hard part with this thing is the lenses. I wonder how hard it would be for astronauts to swap an SSD if it came to that.

by aqme28 4y ago

re-actor 4y ago
No currently available spacecraft can make the trip and service JWST, it's also not really intended to be serviced.
- hoseja 4y ago
  Spaceship might (Elon time) fly this August.
  - danpalmer 4y ago
    It's "Starship", and it's unlikely to be able to get to where the JWST is in the next few years due to needing to be refuelled in orbit. Plus they have no payload bay design. Then there's the robotics necessary for doing a repair, or human-rating Starship, either of which is years worth of time.
    - hoseja 4y ago
      Oh yea. Much less memorable than BFS.
- queuebert 4y ago
  Spitballing here ... could we de-orbit it back to Earth with what propellant remains? Then fix whatever and refill the propellant?
  - brokenmachine 4y ago
    The sunshield had a complicated unfurling sequence, I very much doubt they could fold it back up while still in orbit.
patmorgan23 4y ago
JWST is not serviceable. If the ssd dies, then it's dead. There's no replacing it.
- zimpenfish 4y ago
  > If the ssd dies, then it's dead. Presumably they could operate in a reduced mode where it does live transmission of the data when it's in contact with Earth?
  - Sporktacular 4y ago
    Depends if the sensor readout is slower than 28 Mb/s.
    - zimpenfish 4y ago
      If it generates, at most, 57GB per day[1], assuming 22h operation (2h for transmission), the sensors are generating 2.6GB/h or about 750kB/sec which is just about 6Mb/s (unless my math is wonky.) [1] "JWST can produce up to 57 GB each day (although that amount is dependent on what observations are scheduled)."
      - Sporktacular 4y ago
        That is the average rate over a day. If storage is not available to buffer it, then a sensor's peak readout rate could easily exceed the transmission rate.
        Sporktacular 4y ago
        Edit: Which apparently it does, which is why the SSD can ingest up to 48 Mb/s to be read out more slowly later (https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-solid-state-recorder https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-s...).
        4y ago
317070 4y ago
The JWST is about three times further than the furthest a human has ever been from earth, which was on the moon. So, it would be __really__ hard for astronauts to swap an SSD.
- Aperocky 4y ago
  It's much easier to get there and fix JWST than it is to land on the moon though. Because the landing part was the hardest and take more delta V than actually getting to JWST. Not to mention going back from moon surface.
  - martinskou 4y ago
    Didn’t JWST use some kind of grivitational breaking to stop at the LGPoint? A manned mission would require much more fuel to shorten the time of the trip and fuel for returning.
- beached_whale 4y ago
  I think the engineering that would go into a mission to do maintenance/repair would be quite valuable and help with many other missions. It’s far enough to be far, but not so far that other factors like communication is extremely delayed. Getting that far out of LEO has a huge set of new challenges, I assume, we should be able to learn about.
sp332 4y ago
Maybe we could send up a data buffer with a high-bandwidth, short-range radio.
dotnet00 4y ago
Even if a crewed spacecraft could be sent to it (honestly not that crazy given JWST's predicted lifespan of 20 years. Starship should be crew rated in 10 years at most and if not, Orion could be sent with some sort of expanded service module for the trip) the issue would be that docking to or even approaching the telescope is extremely risky. You don't want to fire any thrusters in its direction to avoid damaging the sunshield or the mirrors, but of course to slow down at it you would need to do that at some point. If the SSD failed and a constant connection to Earth cannot be maintained, the more realistic solution would probably be to launch a satellite to a high orbit to maintain permanent connectivity with JWST which can act as a store-and-forward relay, effectively replacing the SSD without having to actually go to the telescope.

IIRC the hard part with this thing is the lenses. I wonder how hard it would be for astronauts to swap an SSD if it came to that.

by aqme28 4y ago

IIRC the hard part with this thing is the lenses. I wonder how hard it would be for astronauts to swap an SSD if it came to that.

re-actor 4y ago

No currently available spacecraft can make the trip and service JWST, it's also not really intended to be serviced.

hoseja 4y ago
Spaceship might (Elon time) fly this August.
- danpalmer 4y ago
  It's "Starship", and it's unlikely to be able to get to where the JWST is in the next few years due to needing to be refuelled in orbit. Plus they have no payload bay design. Then there's the robotics necessary for doing a repair, or human-rating Starship, either of which is years worth of time.
  - hoseja 4y ago
    Oh yea. Much less memorable than BFS.
queuebert 4y ago
Spitballing here ... could we de-orbit it back to Earth with what propellant remains? Then fix whatever and refill the propellant?
- brokenmachine 4y ago
  The sunshield had a complicated unfurling sequence, I very much doubt they could fold it back up while still in orbit.

patmorgan23 4y ago

JWST is not serviceable. If the ssd dies, then it's dead. There's no replacing it.

zimpenfish 4y ago
> If the ssd dies, then it's dead. Presumably they could operate in a reduced mode where it does live transmission of the data when it's in contact with Earth?
- Sporktacular 4y ago
  Depends if the sensor readout is slower than 28 Mb/s.
  - zimpenfish 4y ago
    If it generates, at most, 57GB per day[1], assuming 22h operation (2h for transmission), the sensors are generating 2.6GB/h or about 750kB/sec which is just about 6Mb/s (unless my math is wonky.) [1] "JWST can produce up to 57 GB each day (although that amount is dependent on what observations are scheduled)."
    - Sporktacular 4y ago
      That is the average rate over a day. If storage is not available to buffer it, then a sensor's peak readout rate could easily exceed the transmission rate.
      - Sporktacular 4y ago
        Edit: Which apparently it does, which is why the SSD can ingest up to 48 Mb/s to be read out more slowly later (https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-solid-state-recorder https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-s...).
        4y ago

317070 4y ago

The JWST is about three times further than the furthest a human has ever been from earth, which was on the moon. So, it would be __really__ hard for astronauts to swap an SSD.

Aperocky 4y ago
It's much easier to get there and fix JWST than it is to land on the moon though. Because the landing part was the hardest and take more delta V than actually getting to JWST. Not to mention going back from moon surface.
- martinskou 4y ago
  Didn’t JWST use some kind of grivitational breaking to stop at the LGPoint? A manned mission would require much more fuel to shorten the time of the trip and fuel for returning.
beached_whale 4y ago
I think the engineering that would go into a mission to do maintenance/repair would be quite valuable and help with many other missions. It’s far enough to be far, but not so far that other factors like communication is extremely delayed. Getting that far out of LEO has a huge set of new challenges, I assume, we should be able to learn about.

sp332 4y ago

Maybe we could send up a data buffer with a high-bandwidth, short-range radio.

dotnet00 4y ago

Even if a crewed spacecraft could be sent to it (honestly not that crazy given JWST's predicted lifespan of 20 years. Starship should be crew rated in 10 years at most and if not, Orion could be sent with some sort of expanded service module for the trip) the issue would be that docking to or even approaching the telescope is extremely risky. You don't want to fire any thrusters in its direction to avoid damaging the sunshield or the mirrors, but of course to slow down at it you would need to do that at some point. If the SSD failed and a constant connection to Earth cannot be maintained, the more realistic solution would probably be to launch a satellite to a high orbit to maintain permanent connectivity with JWST which can act as a store-and-forward relay, effectively replacing the SSD without having to actually go to the telescope.