NASA’s Space Telescope Enters Another Critical Phase And Needs To Literally Chill-Out

With much of the initial setup and fine-tuning out of the way, the James Webb Space Telescope's (JWST) instruments have been cooling down, but one instrument in particular needs a cryocooler in order to really chill out. While the other instruments need to reach about 34 to 39 kelvins in order to be operational, the Mid-Infrared Instrument (MIRI) needs to be much colder.

JWST has been essentially chilling out over the majority of the last three months. Its instruments have been cooling down by radiating their thermal energy into the vastness of space. However, there is one instrument that needs a cryocooler to obtain an even more frigid temperature than the others.

The MIRI instrument has been cooling down over the last couple of weeks with the aid of a specialized cryocooler, which circulates cold helium gas around the MIRI optical bench. This helps MIRI to reach a frigid temperature of about 15 kelvins before the cryocooler reaches a critical point in the cooling process referred to as the "pinch-point".

The "pinch-point" is when the cryocooler is transitioning through a range of temperatures near 15 kelvins, which is when its ability to remove heat is at its lowest. During this precarious time, a number of the time-critical valve and compressor operations will occur in rapid succession, while at the same time being adjusted as indicated by the MIRI cryocooler temperature and flow rate measurements. The challenging aspect of this process is that while the cooling ability improves as the temps get colder, if the cooling is not immediately achieved MIRI will start warming.

Once the cryocooler is able to get past the remaining heat loads and help MIRI to reach an operating temperature of around 7 kelvins, it will (hopefully) settle into its lower-power steady science operation state for the rest of the mission. Cryocooler specialists extensively tested the equipment in the cryocooler testbed at NASA's Jet Propulsion Laboratory (JPL), Goddard Space Flight Center, and Johnson Space Center before launching of JWST.

MIRI incorporates both a camera and a spectrograph in order to see light in the mid-infrared region of the electromagnetic spectrum, which includes wavelengths human eyes are incapable of seeing. It covers a wavelength range of 5 to 28 microns, and will detect redshifted light of distant galaxies, newly forming stars, and vaguely visible comets along with objects in Kuiper Belt.

The infrared instrument is vital to JWST being able to unveil astronomical targets ranging from nearby nebulae, to distant interacting galaxies, with an accuracy and sensitivity far beyond what has been captured up to this point. Therefore, being able to get the instrument to its optimal operating temperature is crucial.

Top Image Credit NASA