“For the past two weeks, the cooler has been circulating cooled helium through the MIRI optical line, which will allow us to cool it to -258.15 degrees Celsius. Soon, the cryogenics will face their toughest days of mission,” said Konstantin Benanen and Brett Naylor, cooling specialists at NASA’s Jet Propulsion Laboratory. (JPL-Caltech), by turning on the cryogenic valves, it will redirect the helium and force it to constrict the flow. “As the gas expands as it exits the restriction, it will get colder, bringing the operating temperature of the MIRI detectors below -266.15 degrees Celsius.”

In fact, at any temperature higher than this, the photodetectors will be effectively “blind”. Since they are tuned to operate at mid-infrared frequencies, there is no other option for them to operate. For this reason, the MIRI is installed outside the metal grille where the telescope’s lenses are also located – incredibly heated by absorbing sunlight, but in this way the instrument is thermally insulated.

“Cooling this instrument is one of Webb’s last big challenges before our team can truly relax, and getting past that point is a very important step in this challenge,” said Alistair Glass and Macarena Garcia-Marin, both MIRI calibration experts, when the time is right, the coolant will be It extracted nearly all of the heat from 100 kg of MIRI metal, the remnants of the orbital day of its launch.

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