NASA’s James Webb Space Telescope has finally completed its testing series, which lasted nearly 100 days. It was tested in the cryogenic vacuum chamber, where temperatures drop more than 100 degrees below the freezing point. NASA scientists called the end of the critical test stage on Saturday when they unsealed the 40-ton door of Chamber A. The end of the test stage means the James Web Space Telescope is ready to launch.

James Webb Space Telescope
By NASA [Public domain], via Wikimedia Commons
Scientists closed the door of the vault on July 10 to begin conducting the test on the telescope’s optics and instruments while simulating conditions of interstellar space. The scientists used liquid nitrogen and cold gaseous helium to prepare the frigid temperature for the telescope’s testing. NASA said that the telescope needs to be in a cold environment to spot infrared light from objects that are far away.

The operating temperature of the James Webb Space Telescope and its instruments is around 40 Kelvin, which is equivalent to about -387 Fahrenheit. Moreover, the mid-infrared instrument, also known as MIRI, uses a cryo-cooler which keeps it below 7 Kelvin, which is -447 degrees Fahrenheit.

The tests conducted in the summer were supposed to show how the optical telescope and integrated science instrument module work in the cold vacuum. The scientists also tested the 18 gold primary mirror segments to see whether they act as one mirror. The team tested the telescope using thermal sensors and specialized cameras which can track the temperature and physical position of the components as they were moving. Even Hurricane Harvey didn’t interrupt the testing of the James Webb Space Telescope.

“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,” said Bill Ochs, project manager for the James Webb Space Telescope at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in a statement. “The completion of the test is one of the most significant steps in the march to launching Webb.”

After the scientists closed the vault on July 10 and removed the air, they started cooling it down on July 20. The cooling process lasted about 30 days. After the chamber was cold enough, the telescope stayed in a cryo-stable state for 30 more days. The scientists started warming up the vault on September 27, and then they started letting air back in. On November 18, the doors were unsealed.

“With an integrated team from all corners of the country, we were able to create deep space in our chamber and confirm that Webb can perform flawlessly as it observes the coldest corners of the universe,” said Jonathan Homan, project manager for the James Webb Space Telescope’s cryogenic testing at Johnson, in a statement on NASA’s website. “I expect [Webb] to be successful, as it journeys to Lagrange point 2 [after launch] and explores the origins of solar systems, galaxies, and has the chance to change our understanding of our universe.”