Now is a good time to talk about James webb Space Telescope.

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Deep Science, Oct 16, 2021.

  1. Deep Science Registered Member

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    James webb space telescope is very well known for its capabilities and at the same time it is also very well known for its delays. People have been waiting for its launch for nearly a decade now. Finally it is on its way to get launched. It has now reached French Guiana. Now it is a good time to recall about its capabilities and the gains that NASA is going to make after it will be launched.
     
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  3. Deep Science Registered Member

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  5. exchemist Valued Senior Member

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  7. Yazata Valued Senior Member

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    It's become something of a myth. It's been coming any-day-now for as long as anyone can remember.

    It's certainly needed, since Hubble is ancient, sputtering and running on fumes. I just saw reports that it's shut down again due to some kind of computer problems. (Shut it off and turn it back on again, that's how I fix electronics.)

    It is to be launched by a French Ariane rocket. These have been experiencing problems of their own (with payload fairing deploy I believe), although the problems are said to have been rectified. They just launched two large communications satellites on the first Ariane after a lengthy standdown a couple of days ago and the launch was very successful. (I watched the Arianespace live-stream.)

    We can be certain that the JWST people were watching that launch very closely.

    I'm a little concerned about the JWST because it just looks fragile to me, the way that it unfolds itself like origami. And being a very large (6.5 meter) reflecting telescope, all of its parts have to end up very precisely aligned and situated. JWST costs billions and there's only one, so if it's lost or it fails, the whole project is done. The anxiety as it launches and deploys will be through the roof.

    I believe that apart from improved optical resolution, it will have improved infrared performance, compared to Hubble. Astronomers are very interested in exploiting that. The infrared wavelengths that JWST will concentrate on are blocked by the Earth's atmosphere and Hubble isn't optimized to view them. But there are lots of interesting infrared objects out there, from accretion disks, to distant red stars (dwarves and giants), to distant high-redshift objects. Infrared might possibly make brown dwarves more visible. (I wonder if there are lots of these failed not-quite-stars out there between the stars whose luminosity we can see.

    JWST will end up situated in an interesting spot as well, the Earth's L2 Lagrange point. JWST will be much further from the Earth than the Moon (about 930,000 miles from Earth) at a point in the opposite direction from the Sun on a straight line between the Earth and the Sun. Generally speaking, an object a million miles further from the Sun than the Earth will orbit the Sun more slowly than the Earth. But at the L2 point, the additional gravity of the Earth pulls the L2 object faster so that the point represents a stable station-keeping spot relative to the Earth and the Sun.

    Why place the JWST way out there? Because the Earth and the Sun both occupy a fixed position in the sky relative to the telescope which can put out a parasol-like shield to block out both and not have to worry about constantly moving it. An infrared telescope is very sensitive to heat and both Earth and especially the Sun radiate heat. But at L2 the Sun is always on the opposite side of the Earth, so the Earth blocks the Sun and the parasol blocks the Earth and whatever solar infrared gets past Earth. It's a good spot for space telescopes that want to escape solar interference.

    Here's an 11 year old page that explains the orbital mechanics stuff very well. (The age of the page indicates how long the JWST project has been brewing.)

    https://www.nasa.gov/topics/universe/features/webb-l2.html

    James Webb Space Telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency.
     
    Last edited: Oct 26, 2021
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  8. Yazata Valued Senior Member

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  9. Yazata Valued Senior Member

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    Inspections confirm that JWST wasn't damaged when a clamp unexpectedly gave way sending vibrations through the space observatory. An anomaly review board was held today and they concluded that JWST appears to be healthy and the December 22 launch date is still on.

    OK was given today to begin fueling the JWST which will take about 10 days.

    https://blogs.nasa.gov/webb/2021/11...elescope-on-track-for-targeted-dec-22-launch/
     
  10. orcot Valued Senior Member

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    I wished they didn't launch on christmas, those folks need their holidays and I wouldn't want a rushed job because people wanted to go home to their families or be drunk having celebrated chrismtas eve.
    ideally they would launch the week afther new year.
    These might sound like silly excuses but they are very human excuses
     
  11. sideshowbob Sorry, wrong number. Valued Senior Member

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    I would imagine that most people involved in such a launch would be excited about it miles beyond any excitement about Christmas.
     
  12. orcot Valued Senior Member

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    Most people don't like to work on holidays, some drink, some are lonely some are thinking abouth other things. It's bad practise. But I'm sure the fuel is corroding the fuel tanks so they have to launch or more expenses have to be made.
    I hope we will get to see a succesful launch. That said it will take quit some time to get into position and to get properly cooled down. So not much will be hapening for some time.
     
  13. Yazata Valued Senior Member

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    I wish that they weren't launching so early my (California) time. Launch window is 4:20 to 4:52 AM PST, 7:20 to 7:52 AM EST, 9:20 to 9:52 Kourou time, 12:20-12:52 PM UTC and 1:20-1:52 PM Paris time, all on December 25. It isn't entirely certain that the launch will get off then, since thunderstorms have been happening every day and are predicted for Christmas too. (It's the tropics.)

    https://twitter.com/Arianespace/status/1473406135185154053

    Chris Gebhardt of nasaspaceflight.com in Kourou, French Guiana in front of the huge French Ariane 5 rocket that will (hopefully) hurl the JWST out beyond the Moon's orbit to L2 Christmas morning.

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    Last edited: Dec 23, 2021
  14. Yazata Valued Senior Member

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    Last edited: Dec 24, 2021
  15. Yazata Valued Senior Member

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    Here's a great webpage that will help you track where JWST is on its long trip to L2 and how its unfolding and deployment is going, plus lots of great photos and videos.

    https://jwst.nasa.gov/content/webbLaunch/whereIsWebb.html

    Jonathan McDowell has this more technical chart showing all the steps before JWST is up and running. It is more complicated than just rocketing it out to L-2 (a million miles away) and unfolding it. Everything has to be precisely aligned, thermal characteristics have to be measured and adjusted for, and each scientific instrument has to be brought online one by one. That will take six months!

    https://planet4589.org/space/misc/webb/time.html

    Livestream of the launch here

    [video=youtube]
     
    Last edited: Dec 25, 2021
  16. Yazata Valued Senior Member

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    T - 30 minutes - "the board is green" - no problems so far
     
  17. geordief Valued Senior Member

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    What ,it is now?

    ,(got the stream,thanks,)
     
  18. geordief Valued Senior Member

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    See it lost altitude for a while as part of the predicted course
     
  19. geordief Valued Senior Member

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    Seems to have gone well
    Everyone is congratulating each other now.
     
  20. Yazata Valued Senior Member

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    JWST has separated from the upper stage. It's on the planned trajectory on its way to the L-2 Lagrange point. The Ariane 5's part of the show is over, perfectly performed. The next thing is 300 or more unfolding steps as the JWST assembles itself like a giant piece of origami. That will take about a month. It will be six months before the whole thing is aligned and all of the scientific instruments are online, calibrated and ready.

    But so far, so good. It's off.
     
  21. geordief Valued Senior Member

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    Marvelous,fingers criss-crossed

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  22. mathman Valued Senior Member

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    When it is in place and working wold be a better time to talk about it.
     
  23. James R Just this guy, you know? Staff Member

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    Getting it into place is an engineering and scientific challenge in itself, so it's interesting. If all goes to plan, we'll be hearing a lot more from this telescope once it starts taking science data. In the meantime, the ambition of the whole project and the technical aspects ought to be enough to spark interest from those who are into that kind of thing.
     

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