The James Webb Space Telescope takes a selfie and takes a big step towards its first ‘real’ image – Techdoxx

Deepak Gupta February 11, 2022
Updated 2022/02/11 at 8:37 PM

A device as complex as the James Webb Space Telescope takes a while to get up and running, so although it entered orbit late last month, it is still working on its startup process. Today’s milestone is big, with Webb spotting his first star, 18 times. And it took a selfie to celebrate.

As you probably know if you’ve seen the coverage of this massive orbital telescope over the many years of its development, assembly and deployment, the Webb is basically a collection of 18 honeycomb-shaped mirrors that help you capture large amounts of infrared light from your chosen target.

But each of these mirrors (plus the secondary mirror on the front and many other components) needs to be fine-tuned so that the image reflected in it matches and overlaps with that of the others.

“We know that the primary mirror segments aren’t aligned, so they actually act like 18 separate telescopes, and we expect to see 18 separate images, one for each mirror, which are a little blurry at this point because they’re not aligned for anything focused,” he said. Lee Feinberg, manager of optical elements at Webb, in a NASA video that explains it all better than I ever could.

Think of it like the cartoons where a character wakes up after being knocked out and sees the world in double or quadruple, then gradually lines up those images. In this case, of course, the telescope is in the middle of space, so the best (and pretty much only) thing to safely observe is the stars.

The team needed a star that was distinct and not surrounded by others of similar brightness. They chose one called HD 84406 in the constellation Ursa Major, on the cosmic bear’s neck. For those of us who are more familiar with Ursa Major, if you look at the two stars that make up the top of Ursa Major, HD 84406 is approximately an equal distance to the right along that line.

Pointed in the general direction of the HD 84406, Webb took 10 images each in 156 slightly different directions, resulting in 1,560 photos and 54 gigabytes of raw data.

Image credits: NASA

“This initial search covered an area the size of the full moon because the segment points could be scattered across the sky,” said Marshall Perrin, Webb team scientist, in a NASA press release. ” And we found light from all 18 segments very close to the center at the beginning of this search! This is a great starting point for mirror alignment.”

After six hours of processing, they were able to locate the same star on each of the telescope’s 18 mirrors and assemble them into an image (at the top) that shows how the array needs to be realigned. As Perrin noted, it is entirely possible that one or more of them were much further from the center, necessitating a longer and more intensive mirror correction procedure. But they’re all clustered close to the center, which means the mirror deployment went very well.

This isn’t the Webb’s only onboard camera system, and it’s not the only setup process by far. It will be a while before we get the first “real” image, but today’s success shows that the IR camera and primary mirrors are working as planned – though not yet at full capacity.

Fortunately, another instrument was functional enough to get the most crucial content: a selfie.

Image credits: NASA

We’ll be covering important steps like this one, but if you want to keep track of Webb’s every move, keep an eye on the blog dedicated to mission.

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