A thermal-vacuum chamber that simulates strong sunlight, as well as the temperatures and vacuum experienced in space. The chamber is used to examine and adjust a spacecraft's thermal-control system. The STV at NASA's Johnson Space Center is among the world's largest, and the only one of its size that can simulate thermal conditions present near the planet Venus. The chamber is constructed of stainless steel and is 26 m tall and 8.2 m in diameter, with a door that is 7.6 m wide.

The Cassini spacecraft was tested there for 18 days while suspended from the chamber's walls by steel cables. This was under a solar simulator and in a temperature of −185° C.