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Isn't that exactly the point of saying we should deploy more, cheaper per unit, devices? Sure some of the money went to R&D but the question is not can be it b

Isn't that exactly the point of saying we should deploy more, cheaper per unit, devices? Sure some of the money went to R&D but the question is not can be it be used on a future telescope, it's will it be used? I suspect if someone wants to launch another telescope today they would look at JWST and largely say they need to start over because it doesn't make sense to start with a 20-year-old design.

fogof 5y ago
Well maybe the point is that it's simply not possible to even design a telescope like this without a huge activation energy of R&D costs. If we had deployed more, cheaper devices, it might be the case that those devices, even taken together, would not have given us the information that JWST will. Take the sunshield - the huge tarp-looking thing that you always see below the telescope itself. My understanding is that this is critical for JWST to see in the deep infrared, since otherwise heat will interfere with the imaging. Probably a lot of money was spent on the development of this. But if that money had just been spent on 20 other telescopes, none of them would have been able to capture that part of the infrared spectrum that JWST will.
- asmithmd1 5y ago
  The original sin is the lack of will to make the Webb nuclear powered. Since it is solar powered, it has to be in the sun. Since it has to be in the sun, it needs a huge shield. Since it is solar powered, it must be passively cooled to save power. Since it is passively cooled, it needs the science experiment - 5 layer shield deployed with 50 different pulleys, cables, telescoping poles and who knows what else. The power limit also requires that science data be downloaded with an experimental 26Ghz radio that only the three 100' diameter Deep Space Network dishes can receive. The projected science data download will require using the DSN for 8 hours a day, everyday for 5-10 years. They should have started over using nuclear power and then they would have had a chance.
  - fogof 5y ago
    This is good thinking. However, it seems that Earth doesn't quite eclipse the sun from L2, so it might have been complicated anyway. My calculations tell me this is not true for Mars though. The next time we do this, we should send it to the L2 of Mars.
  - CamperBob2 5y ago
    Arguably, this thing should have been installed on the far side of the Moon, with a relay orbiter to get data back to Earth. Then it could be serviced. (Of course the "dark side" isn't actually dark when the Sun hits it, so that would limit the available observing time.)
    - wcoenen 5y ago
      The near and far side of the moon spent the same amount of time in darkness, so there's no advantage gained by putting it on the far side. Edit: I just realized this idea comes from radio telescopes. Those would actually benefit from sitting on the far side of the moon, because that way they'd be shielded from the radio emissions of human civilization. That concept doesn't transfer to visible light or IR telescopes though.
      - CamperBob2 5y ago
        The moon is tidally-locked, so the near side always faces Earth. It'd be a good place for a spy satellite, maybe, but less desirable for any kind of sensitive astronomical instrument. The Earth might as well be as big as the Sun from the perspective of the IR instrumentation on JWT. They'd prefer to keep it entirely out of their field of view, which is why it's being positioned at L2. Placing the telescope on the far side of the moon would have the same effect at least part of the time, and we'd potentially be able to carry out maintenance and upgrades in the future.
  - Denvercoder9 5y ago
    > Since it has to be in the sun, it needs a huge shield. I don't think there's any place in the solar system you can put things so that they won't be in the sun. If you're going to be in the sun anyway, better use it.

fogof 5y ago

Well maybe the point is that it's simply not possible to even design a telescope like this without a huge activation energy of R&D costs. If we had deployed more, cheaper devices, it might be the case that those devices, even taken together, would not have given us the information that JWST will. Take the sunshield - the huge tarp-looking thing that you always see below the telescope itself. My understanding is that this is critical for JWST to see in the deep infrared, since otherwise heat will interfere with the imaging. Probably a lot of money was spent on the development of this. But if that money had just been spent on 20 other telescopes, none of them would have been able to capture that part of the infrared spectrum that JWST will.

asmithmd1 5y ago
The original sin is the lack of will to make the Webb nuclear powered. Since it is solar powered, it has to be in the sun. Since it has to be in the sun, it needs a huge shield. Since it is solar powered, it must be passively cooled to save power. Since it is passively cooled, it needs the science experiment - 5 layer shield deployed with 50 different pulleys, cables, telescoping poles and who knows what else. The power limit also requires that science data be downloaded with an experimental 26Ghz radio that only the three 100' diameter Deep Space Network dishes can receive. The projected science data download will require using the DSN for 8 hours a day, everyday for 5-10 years. They should have started over using nuclear power and then they would have had a chance.
- fogof 5y ago
  This is good thinking. However, it seems that Earth doesn't quite eclipse the sun from L2, so it might have been complicated anyway. My calculations tell me this is not true for Mars though. The next time we do this, we should send it to the L2 of Mars.
- CamperBob2 5y ago
  Arguably, this thing should have been installed on the far side of the Moon, with a relay orbiter to get data back to Earth. Then it could be serviced. (Of course the "dark side" isn't actually dark when the Sun hits it, so that would limit the available observing time.)
  - wcoenen 5y ago
    The near and far side of the moon spent the same amount of time in darkness, so there's no advantage gained by putting it on the far side. Edit: I just realized this idea comes from radio telescopes. Those would actually benefit from sitting on the far side of the moon, because that way they'd be shielded from the radio emissions of human civilization. That concept doesn't transfer to visible light or IR telescopes though.
    - CamperBob2 5y ago
      The moon is tidally-locked, so the near side always faces Earth. It'd be a good place for a spy satellite, maybe, but less desirable for any kind of sensitive astronomical instrument. The Earth might as well be as big as the Sun from the perspective of the IR instrumentation on JWT. They'd prefer to keep it entirely out of their field of view, which is why it's being positioned at L2. Placing the telescope on the far side of the moon would have the same effect at least part of the time, and we'd potentially be able to carry out maintenance and upgrades in the future.
- Denvercoder9 5y ago
  > Since it has to be in the sun, it needs a huge shield. I don't think there's any place in the solar system you can put things so that they won't be in the sun. If you're going to be in the sun anyway, better use it.