NASA has unsealed the 40-tonne doors of a 12-meter diameter cryogenic test chamber at the Johnson Space Center in Houston, Texas. The unsealing signalled the end of a 100-day test phase for the James Webb Space Telescope, to make sure that the sensitive instruments will work as expected in the cold, airless environment in space. The cryogenic test phase was a significant step towards the launch and operation of the telescope, which is considered to be a replacement for the Hubble Space Telescope.
Bill Ochs, project manager for the James Webb Space Telescope said, "After 15 years of planning, chamber refurbishment, hundreds of hours of risk-reduction testing, the dedication of more than 100 individuals through more than 90 days of testing, and surviving Hurricane Harvey, the OTIS cryogenic test has been an outstanding success. The completion of the test is one of the most significant steps in the march to launching Webb."
The crew responsible for testing the spacecraft continued through the planned tests, even as Hurricane Harvey raged in and around the facility. Although some instruments were previously tested in smaller cryogenic chambers, this was the first time that the optics and instruments were tested at the same time. The 18 gold-plated hexagonal mirrors on the telescopes worked together as a single reflective surface during the test.
The air was first pumped out of the chamber, a process that took a week. After that, the whole chamber was cooled to temperatures that telescope is expected to work at. The telescope will now be integrated with the spacecraft, which together will form the observatory. Further tests will be conducted on the entire observatory, including flight and deployment testing. Construction of the telescope was completed in November 2016.
In May 2017, NASA completed environmental tests on the telescope, to make sure that the sensitive instruments on board the telescope would not be damaged during the launch sequence.
The telescope was originally scheduled for launch in late 2018, but NASA has postponed the date to early 2019 because additional time was needed to integrate all the elements of the telescope. Once in operation, the James Webb Space Telescope will be the largest observatory in space.
The James Webb Space Telescope is expected to answer many pending questions for astronomers, including why Pluto has a colder atmosphere than predicted, look for potential signs of life in the seven rocky exoplanets in orbit around an ultracool dwarf star in the TRAPPIST-1 system, and identify pairs of runaway stars.