NASA’s James Webb Space Telescope began a nearly 100-day cryogenic test in a giant chamber in Texas last month.
Components of the Webb have previously endured similar tests to ensure they would function in the cold environment of space. Now all of those components are being tested together in the giant thermal vacuum known as Chamber A at NASA’s Johnson Space Centre in Houston.
Vacuum pumps remove nearly 100% of the air from the chamber. Temperatures are cooled in Chamber A by coursing liquid nitrogen and cold gaseous helium through plumbing on the shrouds, which act as heat exchangers. That process drops the temperatures in the chamber to simulate conditions in space where the Webb telescope will orbit.
Paul Geithner, Webb’s deputy project manager - technical of NASA Goddard said, “Of course the chamber stays under vacuum and the cryogens are flowed through the shroud plumbing to radiatively cool everything inside the chamber.”
The testing is critical because these instruments must operate at around -387 Fahrenheit (-232.8 degrees Celsius or 40 Kelvin). This is 260 Fahrenheit (126.7 degrees Celsius) colder than any temperature ever recorded on Earth’s surface.
In Chamber A, the telescope will be cooled down so temperatures are steady and change very little with time, and then warmed up to room temperature or “ambient” conditions.
During the testing period, scientists and engineers will monitor the telescope with temperature sensors and cameras in Chamber A.
Gary Matthews, an engineer on the Webb telescope at Goddard said, “As far as monitoring goes, there are many thermal sensors that monitor temperatures of the telescope and the support equipment. We also have some specialised camera systems that allow us to know the physical position of the hardware inside the chamber. That allows us to monitor how the Webb moves as it gets colder. Finally, there is a whole host of optical equipment that we will use to understand the performance of the telescope.”
Once the end-to-end cryo-optical testing is complete at NASA Johnson this autumn, the telescope will journey to Northrop Grumman in Redondo Beach, California, where it will be integrated with the spacecraft and sunshield, thus forming the James Webb Space Telescope observatory. Once there, it will undergo more tests called “observatory-level testing.” This testing is the last exposure to a simulated launch environment before flight and deployment testing on the whole observatory.
The James Webb Space Telescope is the world’s most advanced space observatory. This engineering marvel is designed to unravel some of the greatest mysteries of the universe, from discovering the first stars and galaxies that formed after the big bang to studying the atmospheres of planets around other stars. It is a joint project of NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA).