James Webb telescope's coldest instrument reaches operating temperature

The James Webb Space Telescope will be able to see the first galaxies after the Big bang, but first it needs to be cold. On April 7, the final operating temperature of the Mid-Infrared Instrument was 7 kelvins.

MIRI dropped to about 90 kelvins when it was in the shade of the sun shield. An electric powered cryocooler was required to drop to less than 7 kelvins. The team passed a particularly challenging milestone last week when the instrument went from 15 kelvins to 6.4 kelvins.

Analyn Schneider, project manager for MIRI at NASA's Jet Propulsion Laboratory in Southern California, said that the team was both excited and that they had poured a lot of hard work into developing the procedure for the pinch point. It was a textbook execution of the procedure, and the cooler performance is even better than expected.

The low temperature is necessary because all four of the instruments detect the same wavelength of light. Stars hidden in dust and planets outside our solar system emit light. Other warm objects, including his own electronics and optics hardware, do the same. The four instruments are cooled down to suppress the emissions. It needs to be even colder than the other three instruments to detect the longer wavelength of the IR.

Dark current, or electric current, is created by the vibrating of atoms in the detectors, so they need to be cold. The false impression that the detectors have been hit by light from an external source is caused by dark current. Astronomers want to find the real signals. Since temperature is a measurement of how fast the atoms in the detector are vibrating, reducing the temperature means less vibration and less dark current.

It needs to be colder than the other instruments to fully remove the effect of dark current. The dark current goes up by a factor of 10 when the instrument temperature goes up.

Scientists began a series of checks to make sure the detectors were working as they were supposed to. Like a doctor looking for a sign of illness, the MIRI team looks at the data and gives the instrument a series of commands to execute the tasks. The integration of the MIRI and the cooler to the rest of the observatory was the culmination of work by scientists and engineers at multiple institutions.

Mike Ressler, project scientist for MIRI at JPL, said that they spent years practicing for that moment. When the test data came in, I was happy to see that we have a healthy instrument.

There are still more challenges that the team will have to face. When the instrument is at operating temperature, team members will take test images of stars and other known objects that can be used for calibration and to check the instrument's operations and functions. The team will conduct these preparations with the other three instruments.

I am immensely proud to be part of this group of highly motivated, enthusiastic scientists and engineers drawn from across Europe and the U.S.

More information: For more information about the Webb mission, visit: https://www.nasa.gov/webb Citation: James Webb telescope's coldest instrument reaches operating temperature (2022, April 13) retrieved 13 April 2022 from https://phys.org/news/2022-04-james-webb-telescope-coldest-instrument.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.