November 21, 2017
JOHNSON SPACE CENTER, HOUSTON, Texas. On November 18, NASA unsealed the 40-metric-ton doors of a cryogenic test chamber at the Johnson Space Center, marking the end of a 100-day cryogenic test phase for the James Webb Space Telescope, to make sure that the telescope's sensitive instruments will work as expected in the cold, airless environment of space. The cryogenic test phase was an important step toward the launch and operation of the telescope, which is considered to be a replacement for the Hubble Space Telescope.