NASA’s James Webb Space Telescope sits in front of the door to Chamber A, a giant thermal vacuum chamber operating below the extremely cold 50 K (-223° C or -370° F).
The space telescope will soon be moved into the chamber, located at NASA’s Johnson Space Center, where it will spend a hot Houston summer undergoing tests at sub-freezing cryogenic temperatures. The telescope will operate below an extremely cold 50 K (-223° C or -370° F) in space, so NASA is simulating those conditions on the ground, ensuring the optics and instruments will perform perfectly after launch.
In space, the telescope itself must be kept extremely cold, in order to be able to detect the infrared light from faint and very distant objects. To protect the telescope from external sources of light and heat (like the sun, Earth, and moon) as well as from heat emitted by the observatory itself, a five-layer, tennis court-sized sunshield acts like a parasol providing shade.