James Webb’s MIRI Instrument Reaches Its Chilly Operating Temperature

During the cooling process, the MIRI team had to face one of their most daunting challenges yet – getting through the “pinch point.” This is where the instrument is taken from a temperature of 15 kelvins down to 6.4 kelvins — which is a difficult stage for the cooler. That’s because this is the temperature when the cooler has the hardest time removing heat from the system, so there had to be a carefully choreographed progression of adjusting values and the compressor based on the cooler’s flow rate and temperature (via NASA blogs).

To make sure they were ready for this challenge, the team practiced the operations in advance, here on Earth. “We spent years practicing for that moment, running through the commands and the checks that we did on MIRI,” said MIRI project scientist, Mike Ressler of JPL. “It was kind of like a movie script: Everything we were supposed to do was written down and rehearsed. When the test data rolled in, I was ecstatic to see it looked exactly as expected and that we have a healthy instrument.”

Thanks to these preparations, MIRI reached its 6.4-kelvin temperature goal and the researchers were able to perform checks to show it was working as expected. With the instrument chilled and ready, the team is expected to calibrate by taking test images of stars, ahead of science operations later this summer.