James Webb Space Telescope completes cryotest of all flight mirrors, and passes

Redondo Beach, CA--The last six primary mirror segments and the secondary mirror that will fly on NASA's James Webb Space Telescope (JWST)—built by Northrop Grumman—have passed their final cold test.

Redondo Beach, CA--The last six primary mirror segments and the secondary mirror that will fly on NASA's James Webb Space Telescope (JWST)—built by Northrop Grumman—have passed their final cold test. The company is leading JWST design and development for NASA's Goddard Space Flight Center (Greenbelt, MD).

This milestone concludes testing on the telescope's individual mirror segments and represents the culmination of a years-long process that broke new ground in manufacturing and testing large space-qualified mirrors. It also signifies that the company can build a large, deployable telescope for space with 18 beryllium mirrors that operate as one, says Scott Willoughby, vice president and Webb program manager, Northrop Grumman Aerospace Systems.

Completed at the X-ray & Cryogenic Facility at NASA's Marshall Space Flight Center (Huntsville, AL), a 10-week test series chilled the primary mirror segments to -379°F. During two test cycles, telescope engineers took extremely detailed measurements of how the mirror's shape changes as it cools. Cryotesting verifies that the mirror will respond as expected to the extreme temperatures of space.

Teammate Ball Aerospace performed a comparable test on the secondary mirror, which presented a unique testing challenge because it is the only mirror that is convex, with a surface that curves or bulges outward. It involved a special test and more complex optical measurements.

For more information, including a video, please visit www.jwst.nasa.gov/videos_mirror1.html.

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