The doors are sealed, and our next critical testing milestone has begun! At this very moment, the James Webb Space Telescope’s spacecraft and sunshield, known together as the Spacecraft Element are locked inside a thermal vacuum chamber at Northrop Grumman’s space park in Redondo Beach, California. Special chambers like these help technicians and engineers to test Webb’s hardware in similar conditions to what it will experience while in space.

Thermal vacuum testing is designed to ensure that Webb can function electronically while experiencing varying hot and extremely frigid temperatures while in orbit nearly a million miles away.

Shown in this video, #Webb is so large that engineers had to suspend it in the air, and lower it into a subterranean prep area to be bottom-loaded into the thermal vacuum chamber. Once complete, thermal vacuum testing puts Webb one big step closer to full integration into its final form later this year.