There seemed to be some news about the James Webb Space Telescope (JWST) every few days earlier this year, but we have not heard so much from the revolutionary observatory recently. This is because it was relaxing – literally. The telescope cannot begin to engage in science until its instruments have reached the correct operating temperature. NASA now reports that Webb’s coldest instrument has reached the desired temperature, marking another step towards its full operation. Unlike Hubble, JWST was designed to look at the mid-infrared part of the electromagnetic spectrum. Any incorrect heat, either from ground sources or from the sun, could ruin such observations. This is why the spacecraft was developed at Lagrange Earth-Sun L2, outside the Moon’s orbit. A few months ago, Webb successfully developed its sunscreen, allowing the interior to cool to the desired temperature, just above zero. NASA says Webb’s average infrared instrument (MIRI) has reached a temperature of just 7 Kelvin (-266 Celsius, -447 Fahrenheit). Initially, MIRI and other telescope instruments struck 90 Kelvin exactly the size of a tennis court. To get it to where it is at the moment, the team turned on the spacecraft’s electric cryopreser. To get there, the refrigerator had to successfully pass the “sting point”, a range of around 15 Kelvins where the refrigerator’s ability to remove heat is at an all-time low. Several time-critical valve and compressor functions were activated sequentially to bridge the gap and get the observatory to where it is now. All four of Webb’s scientific instruments are infrared, so they need to be kept cool. However, MIRI is special. Because it is designed to scan longer infrared wavelengths, it is more sensitive to a phenomenon known as dark current. This is a tiny electric current generated by atomic vibration. Dark current may appear as a legitimate signal to detectors, but keeping them cool mitigates the effect. That’s why the MIRI has to be colder than the rest of the telescope and at 6.4 Kelvin, it’s exactly where it needs to be. Previously, NASA completed the alignment and stacking of the telescope’s multifaceted mirror, and now the team can begin calibrating MIRI. This includes taking pictures of familiar objects to confirm the functions and functionality of the instrument. Other media must go through similar operations. It was a pleasure to see Webb passing one milestone after another, especially after so many years of delays on Earth. When fully functional, Webb will be able to look back at the dawn of the universe where objects are too dim to see even Hubble. It could also be vital for exploring exoplanets, which are equally dim signals next to stars. NASA expects the first scientific operations to begin this summer. Read now:
