The Webb Space Telescope is completing the last step before deployment.

Weber's mid-infrared imager (MIRI) is in the final stage of cooling, which is a prerequisite for telescope calibration step 7.

Near infrared instruments (NIRCam, NIRSpec, FGS-NIRISS) have reached the passive cooling temperature of their target range of 34 to 39 Kelvin. However, its mid-infrared (5-28 microns) detector needs to be below 7 Kelvin to detect photons with longer wavelength. Such a low temperature can't be achieved by passive heat dissipation, so Weber brought an innovative refrigerator to actively cool the detector.

This refrigerator uses helium to transfer heat from MIRI's optical components and detectors to the warm side of the sun visor. In order to manage the cooling process, MIRI is also equipped with heaters to protect its sensitive parts from the risk of freezing. Weber's team has begun to gradually adjust the refrigerator and these heaters to ensure the slow, controlled and stable cooling of the instrument. Soon, the research team will completely turn off the heater of MIRI, so that the working temperature of the instrument will drop below 7 Kelvin (-447 degrees Fahrenheit, or -266 degrees Celsius).

MIRI has a camera and a spectrometer, which can see the light in the infrared region of the electromagnetic spectrum, and the wavelength is longer than what we can see with our naked eyes. MIRI covers the wavelength range of 5 to 28 microns. Its sensitive detectors will enable it to see distant galaxies, newly formed stars, faint comets and red-shifted light from objects in the Kuiper Belt. MIRI's camera will provide wide field of vision and broadband imaging, which will continue to amaze astrophotography, which makes Hubble telescope so attractive. The spectrometer will achieve a medium resolution spectrum and provide new physical details of distant objects it will observe. MIRI has three arsenic-doped silicon (Si:As) detector arrays. The camera module provides a wide-field broadband image, and the spectrometer module provides a medium-resolution spectrum in a smaller field of view than the imager.

One of the most challenging requirements of cryogenic coolers is low vibration. The vibration level needs to be very low to prevent jitter (induced jitter) of optical elements and blurred images generated. The pulse tube refrigeration in CCA precooler and Joule-Thomson effect refrigeration in CHA have no moving parts. The only moving parts in the cryocooler are two horizontally opposed piston pumps with two cylinders in CCA. As the finely balanced and adjusted horizontally opposed pistons move in an almost perfect opposed manner, the vibration is largely cancelled out, thus being minimized.