#cryogenic testing

NASA’s James Webb Space Telescope sits inside Chamber A at NASA’s Johnson Space Center in Houston after having completed its final cryogenic testing on Nov. 18, 2017.

Since many materials change shape when they change temperature, a test team from Ball Aerospace worked together with NASA engineers at Marshall’s X-ray and Cryogenic Facility (XRCF) to cool the mirror segments down to the temperature Webb is experiencing in deep space, -400 degrees Fahrenheit (-240 degrees Celsius).

Cryogenic testing of the primary mirror segments began in at Marshall’s XRCF by Ball Aerospace in 2009.

The change in mirror segment shape due to the exposure to these cryogenic temperatures was recorded by Ball Aerospace Engineers using a laser interferometer. This information, together with the mirrors, traveled back to California for final surface polishing at Tinsley. The mirrors’ final polish was completed in June of 2011.

By the end of 2013, all the flight primary mirror segments, as well as the secondary and tertiary mirrors would be at Goddard. The mirrors were stored in special protective canisters in the cleanroom, awaiting the arrival of the flight telescope structure.

Inside a massive clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland the James Webb Space Telescope team used a robotic arm to install the last of the telescope’s 18 mirrors onto the telescope structure.

James Webb Space Telescope Mirror Seen in Full Bloom

Once the mirrors were completed, the science instruments were integrated into the telescope. While at Goddard, the telescope also underwent environmental testing – both acoustic and vibration – to ensure it would be able to withstand the rigors of launch. That successfully completed, the telescope was sent off to NASA Johnson in Houston, Texas, for tests of the optics and instruments at cryogenic temperatures. NASA Johnson’s Chamber A is the only thermal vacuum chamber NASA has that is large enough for Webb!

The Lunar Environment Structural Test Rig (LESTR) is a crucial tool in NASA’s preparations for future lunar missions, specifically designed to simulate the incredibly challenging thermal and vacuum conditions experienced during the Moon’s long nights. This innovative rig allows scientists and engineers to rigorously test materials, electronics, and even entire spacecraft components at…

From NASA Image of the Day; February 2, 2018:

Observations From -369.7 Degrees Fahrenheit

Taken from inside Chamber A at the Johnson Space Center in Houston in September 2017 while the combined optical and science instrument element of the James Webb Space Telescope was undergoing cryogenic testing, the temperature at the time this image was taken was approximately 50 kelvins (about -369.7 degrees Fahrenheit/-223.2 degrees Celsius). The camera that captured this image was placed inside the chamber to measure the telescope’s alignment, but engineers also used it to monitor the black DuPont™ Kapton® covering that outlines Webb’s primary mirror. Engineers used this and other images to assess the material’s slack as the telescope shrank ever so slightly in the extreme cold of the chamber.

Once Webb is fully deployed and in orbit at the second Lagrange point (L2), this Kapton® “wreath” around the primary mirror will block unwanted light from behind the telescope from interfering with its observations. There are five so-called "Lagrange Points" - areas where gravity from the Sun and Earth balance the orbital motion of a satellite. Putting a spacecraft at any of these points allows it to stay in a fixed position relative to the Earth and Sun with a minimal amount of energy needed for course correction.

In the photo, you can see each of Webb’s 18 hexagonal primary mirror segments, though the ones further from the camera quickly fade into darkness. The bright elements in the photo — the “stars” that seem to envelope Webb within the chamber — are targets that were used to measure extremely precise movements of the telescope as it cooled. Those targets appear so bright because this photo had a very long exposure time.

Webb’s combined optical and science instrument element completed cryogenic testing inside the chamber in November 2017.

James Webb Telescope ‘Pathfinder’ Replica Completes First Cryogenic Optics Test

The ‘Pathfinder’ enters Chamber A at NASA’s Johnson Space Center. Image Credit: NASA/Chris Gunn If there is one mantra that drives the development of space mission projects, it’s ‘test, test, test’. Before every successful manned or robotic mission has ever flown to space countless man-hours were devoted for extensive and rigorous testing on the ground in order to ensure that every piece of…