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The James Webb Space Telescope

MacNut

macrumors Core
Original poster
Jan 4, 2002
22,193
8,677
CT
The successor to Hubble won't launch for another 2 years but they just uncovered the huge 18 mirrors.

Hubble is the size of a school bus, Webb is the size of a tennis court.
http://www.nasa.gov/feature/goddard/2016/james-webb-space-telescopes-golden-mirror-unveiled
 

monokakata

macrumors 68000
May 8, 2008
1,913
423
Ithaca, NY
Let's hope they point it the right way, and set the focus to infinity, this time.
Hubble's issues weren't quite that simple. For a look at Hubble from the inside, check out this excellent book:

http://www.amazon.com/Hubble-Wars-A...F8&qid=1461856466&sr=8-1&keywords=hubble+wars

written by a high-up insider. It's interesting and on some levels, depressing (quality control, for example), and then the mad political/scientific scramble when it became clear that the primary mirror had been incorrectly ground.

One thing that's always stuck in my mind was that Hubble was subject to vibrations when its solar panels hit direct sunlight. This hadn't been anticipated. Yet, as Chaisson points out, in the same building but on the other side of an impenetrable security wall, were engineers who not only were completely aware of that problem, but had solved it -- the spy satellite guys, who had already made many Hubble-class telescopes that pointed down, not up. The two groups could not talk to each other.
 
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OLDCODGER

macrumors 6502a
Jul 27, 2011
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388
Lucky Country
Hubble's issues weren't quite that simple. For a look at Hubble from the inside, check out this excellent book:

http://www.amazon.com/Hubble-Wars-A...F8&qid=1461856466&sr=8-1&keywords=hubble+wars

written by a high-up insider. It's interesting and on some levels, depressing (quality control, for example), and then the mad political/scientific scramble when it became clear that the primary mirror had been incorrectly ground.

One thing that's always stuck in my mind was that Hubble was subject to vibrations when its solar panels hit direct sunlight. This hadn't been anticipated. Yet, as Chaisson points out, in the same building but on the other side of an impenetrable security wall, were engineers who not only were completely aware of that problem, but had solved it -- the spy satellite guys, who had already made many Hubble-class telescopes that pointed down, not up. The two groups could not talk to each other.

Infighting aside, the HST was rushed into service (from a ten year mothballing) - after Big Bird One suddenly failed. And, coincidentally, the focal point of the primary mirror was fine - if pointed towards Earth.

Make of that what thou wilt.
 
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SandboxGeneral

Moderator emeritus
Sep 8, 2010
26,482
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Detroit
I saw this on NASA's Twitter the other day. Such a beautiful telescope. I'm really looking forward to seeing what it sees.
 
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obeygiant

macrumors 601
Jan 14, 2002
4,041
3,878
totally cool
The team behind NASA’s upcoming James Webb Telescope has a new problem to deal with — falling of screws and washers from the spacecraft element that is meant to carry and provide support functions for the operation of the multi-billion dollar space observatory.

During the recent set of environmental testing at Northrop Grumman facility in Southern California, technicians found the fallen parts under the spacecraft bus and its sunshield, SpaceNews reported. The craft and its parts are critical for the success of the mission, but the issue does not relate to optical and other instruments packed with the telescope.

The problem was revealed by NASA's JWST program director Greg Robinson at the National Academies’ Space Studies Board on May 3.

“Right now we believe that all of this hardware — we’re talking screws and washers here — come from the sunshield cover,” Robinson told the news outlet. “We’re looking at what this really means and what is the recovery plan.”

The five-layer sunshield of the craft is nearly as big as a tennis court and is made from a heat-resistant material called Kapton. Its sole job is to keep the telescope in shade and protect it from its own as well as external light and heat.

The fallen screws came to the technicians' notice a few days ago after the spacecraft was moved from one chamber to another. It had completed acoustic testing and was slated to undergo vibration tests in the second chamber. Apart from this, Robinson did not reveal too many details about the fault in question, but he did reiterate the importance of the testing phase which could bring problems like these into the light.

“It’s not terrible news, but it’s not good news, either,” he added.

That said, it is worth noting that this is not the first glitch witnessed by James Webb Space Telescope prior to its launch. Earlier, the telescope was set to lift-off in spring 2019, but due to tears in the sunshield of its spacecraft, leaks in propulsion thruster valves, and other technical glitches, the space agency pushed back the launch timeline by almost a year to May 2020. It even chartered an independent review board to keep a track on mission progress, assess launch readiness and identify the needs to ensure its success.

The review will be completed by the end of May and the agency will provide the report to Congress in June. According to Robinson, the report could have an impact on the tentative launch date, but the latest glitch encountered is unlikely to bring a change in the scheduled launch timeline. This is primarily because they curated this revised schedule with enough margin to bear glitches like these and follow it.

“I still believe we’ll go in 2020, in roughly the same timeframe that we talked about, unless this problem takes longer than we expect,” he added. link
We will have to wait another year for launch. I can't wait to see what kinds of images this telescope gets.
 
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Anonymous Freak

macrumors 603
Dec 12, 2002
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And, coincidentally, the focal point of the primary mirror was fine - if pointed towards Earth.

A long-disproven rumor. The focal point was set incorrectly because the measuring tool was badly calibrated. The person who set it forgot to add the thickness of the tool itself. It had nothing to do with "focusing on Earth vs. space" - Hubble's gyroscopes can't swing the satellite fast enough to track a point on the Earth - so aligning the mirrors for Earth-pointing wouldn't have made any sense.
 
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OLDCODGER

macrumors 6502a
Jul 27, 2011
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Lucky Country
A long-disproven rumor. The focal point was set incorrectly because the measuring tool was badly calibrated. The person who set it forgot to add the thickness of the tool itself. It had nothing to do with "focusing on Earth vs. space" - Hubble's gyroscopes can't swing the satellite fast enough to track a point on the Earth - so aligning the mirrors for Earth-pointing wouldn't have made any sense.

OK, that's the third version of events leading to failure. I am still intrigued by the timeline, given the outbreak of war in the Middle East and the failure of Big Bird One.
 
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