Those cryonically-tested mirrors reflect well on James Webb.
Here's a #ThrowbackThursday to when #NASAWebb's flight mirrors were undergoing cryogenic testing @NASA_Marshall!
Testing took place in a huge, helium-cooled vacuum chamber, which took Webb's mirrors from room temperature all the way down to -379 degree F, or -228 degrees C! 
pic.twitter.com/Tx0qBIutkU
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Wasn't this supposed to launch last year? When is it going to happen?
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Eventually cause delays
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What is the temperature maintained when a human is in there??
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What's the plan for cooling when helium reserves run out?
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While the testing chamber is helium-cooled in order to simulate space, Webb won't use helium to cool its mirrors. The mirrors will stay cool by being in the shade of Webb's sunshield, which will always face the Sun & block heat. More on the sunshield: https://www.jwst.nasa.gov/content/observatory/sunshield.html …
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Which would be the first exoplanet observed by James Webb telescope?
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