This thermal vacuum chamber exposes spacecraft components and other payloads to the environmental conditions they will experience once in space. The chamber has massive mechanical vacuum pumps, which are essentially large versions of the vacuum cleaners people use at home. To augment those, the chamber uses cryopumps to ensure that the hard vacuum of space is simulated in the test chamber. The cryopumps use liquid nitrogen to condense remaining gases out of the chamber once the mechanical pumps have done their work.
The two types of pumps work together to eliminate all but the tiniest trace of air in the chamber, down to about a billionth of Earth’s normal atmospheric pressure.
To simulate the hot and cold extremes possible in space, the thermal vacuum chamber can reach temperatures in a 600-degree range from 302 F all the way down to minus 310 F (hence the "thermal" vacuum chamber). The cylindrical chamber is 40 feet tall and 27 feet wide.