Four-and-a-half months after the launch of the James Webb Space Telescope for Christmas, engineers have achieved an almost perfect alignment of its complex optical system, laying the groundwork for final instrument calibration and the release of the first scientific images in July, officials said Monday.
“I’m pleased to announce that the alignment of the telescope has been completed with even better performance than we expected,” said Michael McAlwayne, a Webb scientist at NASA’s Goddard Space Flight Center.
“In principle, we have achieved a perfect alignment of the telescope. There is no adjustment of the telescope’s optics that would lead to material improvements in our scientific performance.”
Two images of the same star field in the Great Magellanic Cloud, a small satellite galaxy on the Milky Way. The photo on the left is from NASA’s now retired Spitzer Space Telescope, while the one on the right is from the James Webb Space Telescope. Spitzer, equipped with a 3-foot-wide main mirror, was the largest infrared telescope launched before Webb. By comparison, Webb’s segmented mirror is 21.5 feet in diameter. NASA / ESA / CSA / STScI
Test images showing razor-sharp stars were released on April 18, and a new image was unveiled on Monday showing two views of a star field in the Great Magellanic Cloud, a satellite galaxy in the Milky Way. One image was taken by the much smaller, retired Spitzer Space Telescope, and the other by the Webb or MIRI medium-infrared instrument.
Spitzer’s image shows blurred stars with hints of nebula. But the view of the Web shows crystal clear, precise stars and clearly defined clouds and threads stretching into the field of view.
“From a kind of intellectual point of view, you can estimate that Webb images will be better because we have 18 (mirror) segments, each of which is larger than the single segment that made up the mirror of the Spitzer telescope,” said Marcia Rique. , principal investigator of the nearby infrared camera of the Web or NIRCAM.
“Only when you really see the image it delivers do you really internalize it and go, wow!” Just think what we will learn! Spitzer taught us a lot, but it’s like a whole new world. It’s just incredibly beautiful. “
Scientists and engineers now plan to spend the next two months carefully testing and calibrating Webb’s four scientific tools, collecting test images and spectra to test 17 different modes of operation before launching scientific observations on Cycle 1 this summer.
But first, the team plans to present a series of “early release observations” or EROs, mind-boggling images of spectacular astronomical targets that will show Webb’s scientific abilities and help justify its $ 10 billion cost in the process.
The list of potential targets is a top secret, but NASA plans to reveal selected ERO images and spectra in mid-July.
“Their goal is to demonstrate … to the world and to the public that Webb is fully operational and gives excellent results,” said Klaus Pontopidan, a Webb project scientist at the Space Telescope Science Institute in Baltimore. “It’s also an opportunity to celebrate the beginning of many years of Webb science.”
He said the goals selected by a panel of experts would showcase all four scientific tools, “to highlight all of Webb’s scientific topics … from the early universe, to time galaxies, to the life cycle of stars and other worlds.” “
Impression of the space telescope artist James Webb with its labeled main components. NASA
Webb is designed to capture dim light from the first generations of stars and galaxies that formed after the Big Bang 13.8 billion years ago, light that has been stretched into the infrared region of the spectrum since the expansion of space itself.
Computer, improve! Compare the same goal – seen by Spitzer & in Webb calibration images. Spitzer, NASA’s first Infrared Large Observatory, has led the way to a larger main mirror and improved Webb detectors to see the infrared sky even more clearly: pic.twitter.com/g941Ug2rJ8
– NASA Webb Telescope (@NASAWebb) May 9, 2022
To achieve its razor-focused focus, Webb’s secondary mirror and the 18 hexagonal segments of its 21.3-foot-wide main mirror, each equipped with ultra-precise tilt drives, had to be aligned with nanometer precision. an iterative process that effectively combines 18 reflected rays into one point.
To detect the stretched infrared light from the first stars and galaxies, Web must work within a few degrees of absolute zero, an achievement made possible by the fragile five-layer canopy that unfolded flawlessly shortly after launch.
Since then, mirrors and instruments have cooled to about 390 degrees Fahrenheit, while MIRI, equipped with a high-tech “cryocooler” to improve its ability to observe longer wavelengths, has reached minus 449 degrees, just 6 degrees. -up. absolute zero.
“Overall, the observatory’s performance is phenomenal,” McAlwein said. “It simply came to our notice then. At this point, we characterize and calibrate both the observatory and the scientific instruments.
“From my point of view, there are always risks ahead, but I am very confident that we will reach the finish line here and have a great scientific mission with huge scientific discoveries over the next few months. So I’m just super excited to be in this moment. “
More William Harwood
Bill Harwood has covered the U.S. space program on a full-time basis since 1984, first as head of Cape Canaveral’s United Press International bureau and now as a consultant to CBS News. It covered 129 space shuttle missions, each interplanetary flight since Voyager 2 flew over Neptune, and dozens of commercial and military launches. Based at the Kennedy Space Center in Florida, Harwood is a dedicated amateur astronomer and co-author of “Communication Test: The Last Flight of the Shuttle Columbia.”
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