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Thread: Jwst Telescope Launch

  1. #16
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    Final side of the primary mirror was successfully deployed this morning. NASA had a simulation based on real life sensor data being sent during the event. Even knowing I was watching a simulation it was exciting to watch. Lots of stuff left to do but the sunscreen and mirror deployments were huge milestones. Proposed first pictures this summer if all goes well.
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  2. #17
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    Quote Originally Posted by Michael Weber View Post
    Final side of the primary mirror was successfully deployed this morning. NASA had a simulation based on real life sensor data being sent during the event. Even knowing I was watching a simulation it was exciting to watch. Lots of stuff left to do but the sunscreen and mirror deployments were huge milestones. Proposed first pictures this summer if all goes well.
    I watched that too. The entire deployment was so complex I was on edge since the launch. It was exciting to see the last big piece lock into place and to hear the step-by-step details about the motors and latching. Anyone wanting to be impressed might read abd watch the videos on the making of the mirror segments on this page:
    https://www.webb.nasa.gov/content/ob...ors/index.html
    Amazing.

    Now for mirror alignments then off to L2. By golly, this thing might actually work!!

    Another thing: I found a wonderful video on the why Lagrange points work.


  3. #18
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    Quote Originally Posted by Tom M King View Post
    The Hubble problems were not due to dumb mistakes, or scientists. It was due to Managers pushing sticking to a budget, and deadlines. The Scientists knew chances were not great, especially when testing is cut short.

    This time, they took what time they needed, and spent more money than the managers and politicians wanted to spend.

    When deciding what to do about fixing the Hubble, my friend took in a 12-1/2" mirror that he and I had hand ground when we were teenagers. It was better than what they had. He got put on the team that developed the fix.

    Chances are a Lot better this time, even for a more complicated instrument.
    Sorry, I have to disagree. Perkin-Elmer ground the primary mirror to the wrong curvature, because the technicians overseeing the grinding miscalibrated the optics guiding the grinding, and then ignored data from a calibration check system when it aprised them of their error. The budget and deadline mentality could well be blamed for the fact that the mistake wasn't detected before launch (NASA skipped some testing that would have been usual for such a system), but the screw-up itself was not managerial, it was the technical people on the manufacturing front. They just did the job wrong.

    To their credit, they did it wrong so precisely that it proved possible to fix in place.
    Last edited by Steve Demuth; 01-08-2022 at 8:36 PM.

  4. #19
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    Quote Originally Posted by mike stenson View Post
    In every product I've been involved with that have had problems upon release, those problems were the results of management focusing on delivery time and budget. Without exception. We also knew, every time, that there would be issues.
    You've led a charmed technical life, in that case. Engineers make mistakes and ignore warnings like any human being. The I-35 bridge collapse in Minneapolis in 2007, for example, was traced to improperly specified components in the original design. They weren't undersized to save money, the engineers just calculated the load requirements wrong.

  5. #20
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    nahhhh it was mis ground on purpose so that hubble was first used to take hi res imaging of earth
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  6. #21
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    The NASA page on the Hubble mirror error: https://www.nasa.gov/content/hubbles-mirror-flaw

  7. #22
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    Quote Originally Posted by Mike Soaper View Post
    nahhhh it was mis ground on purpose so that hubble was first used to take hi res imaging of earth
    A Kodak Brownie would have been enough. After all, the earth is flat.
    Never, under any circumstances, consume a laxative and sleeping pill, on the same night

  8. #23
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    I just talked to my friend who was in charge of developing the detectors on it. He retired from NASA soon after they hauled it off for testing, but still is in touch, and he's going to be in on seeing the first images.

    He says everything is working as it should. The one thing you might not hear about why it's taking time to get ready, is that it still has a lot of heat to give off. It's a slow go radiating heat off in a vacuum, so every half of it's temperature it gives off, the next half takes 16 times as long. In other words, as it gets colder, the longer it takes to get more cold.

    He's going to forward me the images as soon as he gets them.

  9. #24
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    So NASA chose a not too bright and not to dim star to use to focus the 18 segments. It started here

    webb_before_alignment.jpg

    and has progressed to here

    91B2572B-7812-41C0-B872-8061B5C193D6.jpeg

    Adding to what Tom King mentioned about the operating temperature, it will cool passively to -380 degrees F but cryocooler(s) will cool the infrared detectors down further to almost -450 degrees F or close to absolute zero. Necessary so any residual heat from the instruments do not affect the extreme infrared spectrum they are looking for. BTW the 18 segments have to be aligned within a faction of the wave length of light. Less than 1/10,000 the thickness of a human hair.
    Last edited by John K Jordan; 02-27-2022 at 7:04 AM.

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