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Posted on 04/10/2009 7:10:43 AM PDT by alnitak
The first mirror segment that will fly on the James Webb Space Telescope, built by Northrop Grumman Corporation, has completed its first series of cryogenic temperature tests in the X-ray and Cryogenic Facility at the Marshall Space Flight Center in Huntsville, Ala.
...
Engineers will measure how the mirror changes shape going from room temperature to cryogenic (frigid) temperatures, as the metal expands and contracts. They can model these changes to some extent, but not perfectly. The mirrors will be polished to about 100 nanometers (a human hair is approximately 60,000 to 120,000 nanometers) accuracy at room temperature, based on the expected changes. Then it will be cooled down to cryogenic temperatures and engineers will measure the mirror's surface, creating a "hit map" of unexpected changes.
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(Excerpt) Read more at sciencedaily.com ...
Very cool IMO.
Very hard to build structure to withstand launch and resist distortion during orbit,with temperatures near 0 degrees Kelvin. Lots of challenging engineering going on in JWST with exotic composite materials and the like, especially at such grand scale.
Whew! For a moment there I thought the nutjob U.S. Senator from Virginia was getting a space telescope named after him.
Are they going to put the whole optical assembly together on the ground and make sure the focus is correct before putting it into space this time?
I hoped they learned a GOOD lesson from Hubble. Do NOT skimp on testing on the ground, even if it seems expensive. It’s a heck of a lot more expensive to have to send someone up into space to fix it.
Heh, I didn’t see your question before I posted my comment, but it seems we were thinking the SAME thing!
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Bump!
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