James Webb Telescope’s latest instrument reaches ultra-low operating temperature

(ORDO NEWS) — The James Webb Space Telescope passed a new milestone – literally – during months of calibration for deep space observations.

The latest instrument aboard the $10 billion James Webb Space Telescope has finally reached operating temperatures just above absolute zero.

Successful cooling ensures that the observatory can explore space objects in infrared light, NASA’s Jet Propulsion Laboratory (JPL) in California, which is leading the US work on an instrument called the Mid-Infrared Instrument (MIRI), said Wednesday (April 13).

Since its launch on December 25, 2021, the telescope has been cooling, bringing it to the cold temperatures needed to accurately detect infrared light, which shows up as heat.

MIRI should be at a temperature just below 7 degrees Kelvin, which is equivalent to minus 266 degrees Celsius. And the complex cooling procedures went very well, thanks to a lot of experience.

“We’ve spent years preparing for this moment, following the commands and checks we did on MIRI,” Mike Ressler, MIRI Project Scientist at JPL, said in a statement.

“It was like a movie script: Everything we had to do was recorded and rehearsed. When the test data came in, I was delighted that everything looked exactly as expected and that we had a healthy instrument.”

The temperature milestone is a key moment in Webb’s multi-stage six-month commissioning period to align mirrors and prepare instruments for deep space observations.

As the telescope cools, constant adjustments must be made as components sometimes behave differently when the temperature drops. But so far, the commissioning of Webb is going almost according to plan.

A key challenge for MIRI was a stage called “pinching point” during which the tool went from a slightly higher temperature of 15 Kelvin (minus 285 degrees Celsius) to a final ultra-cold operating temperature. This “pinch point” is a transition zone during which the cryocooler needed to bring the Webb to its final temperature

“The MIRI chiller team has done a great job developing the pinch point procedure,” Analine Schneider, MIRI Project Manager at JPL, said in the same statement.

“The team was both excited and nervous before the start of a critical operation. As a result, the procedure was carried out to the highest standard, and the performance of the cooler was even better than expected.”

To make sure MIRI is behaving correctly, the team plans to take more test shots of stars and other objects to check the instrument’s calibration and performance. Calibration of the mirrors and three other Webb instruments is also ongoing, as the telescope team aims to complete their work around June.

NASA said it will hold a “key decision meeting” at the end of the alignment, when the telescope can successfully focus light on each instrument, to confirm that the alignment process is complete. Then the final commissioning will follow.

If all goes according to plan, the first science program is expected to start around June, with the operational science program starting in mid-2023.


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