James Webb Space Telescope (JWST)

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Webb telescope spots its first star—and takes a selfie
https://phys.org/news/2022-02-webb-tele ... elfie.html

The first picture sent back of the cosmos is far from stunning: 18 blurry white dots on a black background, all showing the same object: HD 84406 a bright, isolated star in the constellation Ursa Major.

Star light, star bright, the James Webb Space Telescope has seen its first star (though it wasn't quite tonight)—and even taken a selfie, NASA announced Friday.

The steps are part of the months-long process of aligning the observatory's enormous golden mirror that astronomers hope will begin unraveling the mysteries of the early Universe by this summer.

The first picture sent back of the cosmos is far from stunning: 18 blurry white dots on a black background, all showing the same object: HD 84406 a bright, isolated star in the constellation Ursa Major.

But in fact it represents a major milestone. The 18 dots were captured by the primary mirror's 18 individual segments—and the image is now the basis for aligning and focusing those hexagonal pieces.

The light bounced off the segments to Webb's secondary mirror, a round object located at the end of long booms, and then to the Near Infrared Camera (NIRCam) instrument—Webb's main imaging device.
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Webb team brings 18 dots of starlight into hexagonal formation
https://phys.org/news/2022-02-webb-team ... gonal.html
by Alise Fisher, NASA
The James Webb Space Telescope team continues to make progress in aligning the observatory's mirrors. Engineers have completed the first stage in this process, called "Segment Image Identification." The resulting image shows that the team has moved each of Webb's 18 primary mirror segments to bring 18 unfocused copies of a single star into a planned hexagonal formation.

With the image array complete, the team has now begun the second phase of alignment: "Segment Alignment." During this stage, the team will correct large positioning errors of the mirror segments and update the alignment of the secondary mirror, making each individual dot of starlight more focused. When this "global alignment" is complete, the team will begin the third phase, called "Image Stacking," which will bring the 18 spots of light on top of each other.

"We steer the segment dots into this array so that they have the same relative locations as the physical mirrors," said Matthew Lallo, systems scientist and Telescopes Branch manager at the Space Telescope Science Institute. "During global alignment and Image Stacking, this familiar arrangement gives the wavefront team an intuitive and natural way of visualizing changes in the segment spots in the context of the entire primary mirror. We can now actually watch the primary mirror slowly form into its precise, intended shape!"
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Re: James Webb Space Telescope (JWST)

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Webb turns those 18 separate star images into a single unified star. Next comes even better focus.
It’s coming together! Engineers for the James Webb Space Telescope have now completed two more phases of the seven-step, three-month-long mirror alignment process. This week, the team made more adjustments to the mirror segments along with updating the alignment of its secondary mirror. These refinements allowed for all 18 mirror segments to work together — for the first time — to produce one unified image.

As you can see in the image above, this view of the star HD 84406 shows one image instead of the 18 views – one from each segment – that we saw earlier this week. NASA engineers say that after future alignment steps, the image will be even sharper.
Image
https://www.universetoday.com/154683/we ... ore-154683
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James Webb Space Telescope Aligning Its Mirrors
March 14, 2022 by Brian Wang
https://www.nextbigfuture.com/2022/03/j ... rrors.html
In recent weeks, the James Webb Space Telescope team successfully captured starlight through each of Webb’s 18 mirror segments. They refined and stacked those 18 individual dots of light on top of one another to form an initial alignment image of a single star. Since then, in stages of alignment called “coarse phasing” and “fine phasing,” engineers have made smaller adjustments to the positions of Webb’s 18 primary mirror segments so they act as a single mirror, producing a sharp and focused image of a single star.

NASA will hold a virtual media briefing at noon EDT Wednesday, March 16, to provide an update on the James Webb Space Telescope’s mirror alignment. The briefing will air live on NASA TV, the NASA app, and the agency’s website.
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James Webb: 'Fully focused' telescope beats expectations
Source: BBC

Engineers say they have now managed to fully focus the $10bn observatory on a test star. The pin-sharp performance is even better than hoped, they add.

To get to this stage, all of Webb's mirrors had to be aligned to tiny fractions of the width of a human hair.

But the agency cautions that a lot of work still lies ahead before the telescope can be declared operational.

Lee Feinberg, the Nasa engineer who has led the development of Webb's optical elements, described the release of the first properly focused image as phenomenal.
Read more: https://www.bbc.com/news/science-environment-60771210
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James Webb telescope's coldest instrument reaches operating temperature
https://phys.org/news/2022-04-james-web ... ument.html
by NASA's Goddard Space Flight Center
NASA's James Webb Space Telescope will see the first galaxies to form after the Big Bang, but to do that, its instruments first need to get cold—really cold. On April 7, Webb's Mid-Infrared Instrument (MIRI)—a joint development by NASA and ESA (European Space Agency)—reached its final operating temperature below 7 kelvins (minus 447 degrees Fahrenheit, or minus 266 degrees Celsius).

Along with Webb's three other instruments, MIRI initially cooled off in the shade of Webb's tennis-court-size sunshield, dropping to about 90 kelvins (minus 298 F, or minus 183 C). But dropping to less than 7 kelvins required an electrically powered cryocooler. Last week, the team passed a particularly challenging milestone called the "pinch point," when the instrument goes from 15 kelvins (minus 433 F, or minus 258 C) to 6.4 kelvins (minus 448 F, or minus 267 C).

"The MIRI cooler team has poured a lot of hard work into developing the procedure for the pinch point," said Analyn Schneider, project manager for MIRI at NASA's Jet Propulsion Laboratory in Southern California. "The team was both excited and nervous going into the critical activity. In the end it was a textbook execution of the procedure, and the cooler performance is even better than expected."
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