A while ago, we provided an update on the optical alignment of the different instruments of the JWST to its telescope, with the exception of one – the Mid-Infrared Instrument or MIRI – because of the cold temperature needed. Here is more information on how exactly it will get down to its 7 Kelvin operating temperature.
Cold helium gas has been flowing over the instrument, but that’s only enough to get it down to 15 Kelvin. To finish cooling, MIRI has its own cryocooler, which takes the helium gas and squeezes it. The gas cools as it expands out of the cooler, cooling the MIRI instrument with it. This cooling is necessary to see exoplanets with temperatures thought to be similar to Earth. MIRI has four coronagraphs to precisely separate these planets from their host stars and characterize their atmospheres’ chemical makeup.