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The Chamber of Secrets

Ok, this chamber isn’t really a secret, though maybe you didn’t know it existed? Here are a few clues as to its idenity. It is absolutely enormous. It was used during the Apollo era… and a Transformers ™ movie…

View of Chamber A
Image Credit: NASA/JSC

Chamber A at NASA Johnson
Image Credit: NASA/Robert Markowitz & Bill Stafford.

… and is now going to be used to test the James Webb Space Telescope (JWST)!

NASA's Webb "Pathfinder Telescope" Successfully Completes First Super-Cold Optical Test
Image credit: NASA/Chris Gunn

Any guesses?

Ok, here’s the answer. The chamber is question is called “Chamber A” and it’s a thermal vacuum chamber, which basically means it can be used to create a near-vacuum similar to the one in space. (Fun fact: “The air in the chamber weighs 25 tons, about 12 1/2 Volkswagen Beetles; when all the air is removed the mass left inside will be the equivalent of half of a staple,” said Ryan Grogan, JWST Chamber A project engineer at NASA Johnson.)

Also we can control the temperature inside Chamber A – this ability is particularly important to JWST because JWST needs to be very, very cold. This because its instruments and mirrors are primed to be sensitive to the faint infrared light (heat) from things billions of light years away. Any other heat sources could swamp these faint signals. To keep the telescope cool, it will orbit the Sun from a million miles away and use a giant sunshield to keep the heat and light of the Earth, Sun, and Moon blocked from the telescope. JWST needs to operate at chilly temps of less than 50 K (-370 F) in space – so while the telescope is still on the ground, we need thermal vacuum chambers like Chamber A to test it in.  Thanks to recent upgrades, temperatures in Chamber A can now drop all the way down to 11 Kelvin – that is, 11 degrees above absolute zero.

We have a smaller thermal vacuum chamber at NASA Goddard, in which we have tested JWST’s instrument module, but the whole, fully-assembled telescope itself is so big, it won’t fit inside.

Enter Chamber A.

Currently, a piece of test hardware called the pathfinder is sitting in Chamber A with two test mirrors on it. JWST just successfully wrapped up tests of the testing procedures that will be used on the flight hardware! It’s really important that when our flight hardware shows up for testing, that our test equipment is working perfectly, and the test procedures themselves have all been vetted. (You can read more about the tests on this news feature.)

JWST Pathfinder in front of Chamber A
Image Credit: NASA/Chris Gunn

The next step happens at NASA Goddard, where we’ll be mounting the flight mirrors onto the recently arrived flight telescope structure. After the mirrors are attached, we’ll also mount the flight instrument module to the telescope structure – and then the whole telescope will be bound for NASA Johnson and Chamber A for tests, and one step closer to space! (You can view more images of Chamber A on JWST’s Flickr account.)

Chamber A with COCOA and JWST
This is what the flight telescope will look like when it’s in Chamber A. Image Credit: NASA Johnson

Here is a video feature about Chamber A and how JWST will use it:


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