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NASA Space

The James Webb Space Telescope Has Emerged From the Freezer (arstechnica.com) 72

The James Webb Space Telescope has emerged from a large vacuum chamber that was home to temperatures of just 20 degrees Celsius above absolute zero. Scientists have reviewed the data and given the instrument a clean bill of health. "We now have verified that NASA and its partners have an outstanding telescope and set of science instruments," said Bill Ochs, the Webb telescope project manager at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "We are marching toward launch." Ars Technica reports: The $10 billion telescope underwent tests inside Chamber A at Johnson Space Center, which was built in 1965 to conduct thermal-vacuum testing on the Apollo command and service modules. Beginning in mid-July, after the telescope was cooled down to a temperature range of 20 to 40 Kelvin, engineers tested the alignment of Webb's 18 primary mirror segments to ensure they would act as a single, 6.5-meter telescope. (They did). Later, they assessed the fine guidance system of the telescope by simulating the light of a distant star. The Webb telescope was able to detect the light, and all of the optical systems were able to process it. Then, the telescope was able to track the "star" and its movement, giving scientists confidence that the Webb instrument will work once in space. Webb still has a ways to go before it launches. Now that project scientists know that the optic portion of the instrument can withstand the vacuum of space, and the low temperatures at the Earth-Sun L2 point it will orbit in deep space, they must perform additional testing before a probable launch next year.
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The James Webb Space Telescope Has Emerged From the Freezer

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  • L2 is dark (Score:4, Interesting)

    by FeelGood314 ( 2516288 ) on Tuesday January 16, 2018 @03:11AM (#55936927)
    L2 is in the earth's shadow. It will orbit around L2 in such a way that it is never in the earth's shadow but also so that it's sun shield will block light from the earth, the moon and the sun. It will also be about 6 times further from the earth than the moon.
    • Re:L2 is dark (Score:5, Informative)

      by Anonymous Coward on Tuesday January 16, 2018 @03:39AM (#55936997)

      L2 is quite dark because most sunlight is blocked. But in fact, there is still direct sunlight at the exact L2 point.

      This is because L2 is only in the Earth’s penumbra, not its umbra. Put another way, viewed from L2 the Earth only eclipses a large central region of the Sun. The outer parts of the Sun’s disc are still directly viewable, forming a hollow disc (donut) of light around the Earth.

      In order to receive no direct light from the Sun it would need to substatially closer to the Earth so that it is within the umbra (forming a cone volume shape).

      If Earth were a larger planet then the L2 point would be darker with no direct sunlight.
      Of course, indirect light via the Earth’s atmosphere or moonlight would still partially illuminate L2.

      • If only I had Mod Points
      • If Earth were a larger planet then the L2 point would be darker with no direct sunlight.

        Is it? If Earth were a larger planet then the L2 point would be farther, assuming similar Earth density.

      • If Earth were a larger planet then the L2 point would be darker with no direct sunlight.

        It would likely also be more massive in which case the L2 point would be further from the planet which may put it back in the light again. :-)

      • by elistan ( 578864 )
        It's worth noting that the JWST will orbit the L2 point, not sit still in it. The orbit will be 800,000 km in radius [stsci.edu], which is larger than the Moon's orbit around the Earth. Anybody out there good enough with geometry to say whether the JWST will be in the penumbra or not?
  • I gotta say (Score:5, Funny)

    by 93 Escort Wagon ( 326346 ) on Tuesday January 16, 2018 @03:26AM (#55936957)

    “The James Webb Space Telescope has emerged from the freezer” is one of the worst secret recognition codes I’ve heard in a long time. People are going to notice that one!

    • Has there been an end-to-end test of the imaging system? That was neglected (for cost reasons) on a previous space telescope and it proved to be a false economy.
    • by Nidi62 ( 1525137 )

      “The James Webb Space Telescope has emerged from the freezer” is one of the worst secret recognition codes I’ve heard in a long time. People are going to notice that one!

      Still better than "James Webb Space Telescope has a long mustache" or "Images my heart with a monotonous languor".

  • It was out of the freezer before Christmas. My wife works at JSC and we waited in line for 4 hours to see it back on Dec. 20.
  • ... to its final orbit (and been commissioned and been tested and is sending back science data). And then Iâ(TM)ll worry that itâ(TM)s running out of its consumables too quickly or its gyroscopes are failing at a higher than predicted rate.

    These multi-billion dollar space science projects always put me on edge, especially one like this which is so far from earth that there are no easy repair scenarios such as the one that saved Hubble. Too bad that it wonâ(TM)t be unfolded and tested in LEO

    • These multi-billion dollar space science projects always put me on edge, especially one like this which is so far from earth that there are no easy repair scenarios such as the one that saved Hubble.

      If we never go beyond repair range it's going to take an awfully long time to do anything useful in space. Gotta take some risks sooner or later.

      Anyway, hereâ(TM)s hoping that Elon can bring the cost of space flight down by a factor of ten or more so a repair mission to L2 wouldnâ(TM)t be prohibitively expensive.

      I think a better idea is to learn to make things that don't need repair missions. Harder task to be sure but necessary if we really want to explore our solar system in a serious way.

      • Everything is eventually going to run out of propulsion gas for maneuvering, no matter how big you make the tank.

        • Everything is eventually going to run out of propulsion gas for maneuvering, no matter how big you make the tank.

          What is your point exactly? Should we have not sent the Voyager probes because they can't maneuver anymore? Missions don't have to last forever and it's certainly possible to design robotic refueling missions for those where refueling is appropriate. What we shouldn't do is design spacecraft such that they need unnecessary amounts of servicing. Hubble is a great spacecraft but it required more servicing than it really should have. Limiting ourselves only to missions where servicing is comparatively easy

    • So trolling with idiot goddamned smartquotes is a thing now?
      And I take it the canonical retort is "stop posting from your iphone".
  • by Anonymous Coward

    ... And then it will be blown to smithereens by a faulty launch vehicle.

    • I'm also worried about how many eggs are going into one basket here. It's gonna really, really suck if this thing blows up, or has a little programming glitch that causes it to enter the wrong orbit.

  • by Eloking ( 877834 ) on Tuesday January 16, 2018 @11:22AM (#55939017)

    The James Webb Space Telescope has emerged from a large vacuum chamber that was home to temperatures of just 20 degrees Celsius above absolute zero. Scientists have reviewed the data and given the instrument a clean bill of health.

    I guess 20 Kelvin was too "scientific" to be used instead of "20C above absolute zero".

  • How do they test it for surviving the 9G ascent?

"Everything should be made as simple as possible, but not simpler." -- Albert Einstein

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