sci22002 — Announcement

Webb Commissioning Update

29 April 2022

-By Bethany Downer -

Everyone is growing eager for more Webb updates as commissioning continues and we get closer to the Early Release Observations in a few months’ time. Meanwhile, here is a summary of some significant milestones achieved by Webb in the past few weeks. 

Verification of the on-orbit functionality of all Webb’s near-infrared instruments started while they were still cooling down to their operating temperature. On 3 March the European team overseeing the NIRSpec instrument announced the successful completion of the initial checks of all internal mechanisms.

On 16 March it was shared that following the completion of critical mirror alignment steps, the Webb team expects that the observatory’s optical performance will be able to meet or exceed the science goals the observatory was built to achieve. This was delightful news, following the completion of the stage of alignment known as ‘fine phasing’ on 11 March. Every optical parameter that has been checked and tested has been performing to, or above, expectations. The team also found no critical issues and no measurable contamination or blockages to Webb’s optical path. The observatory is able to successfully gather light from distant objects and deliver it to its instruments without issue! With the fine phasing stage of the telescope’s alignment complete, the team had fully aligned Webb’s primary imager, NIRCam, to the observatory’s mirrors.

At this time, the NIRCam telescope alignment evaluation image was shared with the general public and was circulated widely to much excitement online. While the purpose of this image was to focus on the bright star at the centre (2MASS J17554042+6551277) for alignment evaluation, Webb's optics and NIRCam are so sensitive that galaxies and stars in the background were also visible. A NIRCam selfie was also shared and enjoyed by the public; it was created using a specialised pupil imaging lens inside the instrument, as it was designed to take images of the primary mirror segments instead of images of the sky. All of Webb’s 18 primary mirror segments were proudly shown collecting light from the same star in unison.

On 1 April Webb's mirror alignment on NIRCam was successfully extended to the rest of the instruments to create the most accurate and focused image possible across Webb's entire field of view. The early secondary mirror coarse corrections were so successful that the fine corrections in the first iteration of Phase Six were unnecessary as a result of detailed planning and effective teamwork.

On 13 April we were delighted to share that Webb's MIRI instrument had successfully reached its operating temperature below 7 kelvins (minus 266 degrees Celsius), known as the ‘pinch point’! 

Yesterday, on 28 April, we shared that alignment of the telescope is now complete! After full review, Webb has been confirmed to be capable of capturing crisp, well-focused images with each of its instruments (you can see the engineering images here). The observatory is now ready to move ahead with instrument commissioning. 

We are getting closer and closer to science operations with each update! To stay up to date on Webb’s commissioning progress, we invite you to follow and engage with it on our social media pages:



Bethany Downer
ESA/Webb Chief Science Communications Officer

About the Announcement



Webb Alignment Evaluation Image
Webb Alignment Evaluation Image

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