March 25, 2023

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The James Webb Space Telescope is finally ready to do science — and it's seeing the universe more clearly than even its engineers had hoped.

The James Webb Space Telescope is finally ready to do science — and it’s seeing the universe more clearly than even its engineers had hoped.

NASA is set to release the first images captured by the James Webb Space Telescope on July 12, 2022. It will mark the beginning of the next era in astronomy as Webb – the largest space telescope ever built – begins to collect scientific data that will help answer questions about the first moments to the universe and allow astronomers to study the exoplanets in greater detail than ever before. But it took nearly eight months of travel, setup, testing and calibration to make sure these most valuable telescopes are ready for prime time. Marcia Rickey, an astronomer at the University of Arizona The scientist responsible for one of the four webcams explains what she and her colleagues were doing to operate the telescope.

1. What has happened since the telescope was launched?

After the successful launch of the James Webb Space Telescope on December 25, 2021, the team began the long process of moving the telescope to its final orbital location, opening the telescope and — as everything cooled — calibrating the cameras and sensors on board.

The launch was as smooth as a missile launch can happen. One of the first things my NASA colleagues noticed was that the telescope had more fuel left on board than expected for future adjustments to its orbit. This will allow Webb to work longer From the initial goal of the mission, which is 10 years.

The first task during Webb’s month-long journey to his final position in orbit was to open the telescope. This continued without any hitches, starting with Spread the sunscreen with a white joint Helps cool the telescope, followed by alignment of the mirrors and triggering of the sensors.

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As soon as the sun shield was opened, our team began monitoring temperatures Four cameras and spectrophotometers on boardwaiting for them to reach temperatures low enough so we can start testing both 17 different modes the tools can operate.

NIRCam on Webb was the first tool to go online and helped align 18 mirror clips.
NASA’s Goddard Space Center / Wikimedia Commons

2. What did you test first?

The cameras on Webb cooled just as the engineers had expected, and the first instrument the team turned on was the near-infrared camera — or NIRCam. NIRCam is designed to study Dim infrared light from the oldest stars or galaxies in the universe. But before it could do that, NIRCam had to help align 18 individual segments of a Web mirror.

Once the NIRCam cooled to 280 degrees Fahrenheit, it was cold enough to begin detecting light reflected off the Webb mirror clips and producing the telescope’s first images. The NIRCam team was ecstatic when the first scans arrived. We were in business!

These pictures showed that the mirror clips were They all refer to a relatively small area of ​​the skyThe compatibility was much better than the worst-case scenario we had planned.

Webb’s precision-guidance sensor also came into play at this time. This sensor helps keep the telescope firmly pointed at the target – just like image stabilization in consumer digital cameras. Using the star HD84800 as a reference point, I helped my NIRCam teammates connect to align mirror segments until they were nearly perfect, Much better than the minimum required for a successful mission.

3. What sensors came alive after that?

As the mirror alignment wrapped up on March 11, the near-infrared spectrometer – NIRSpec – and the near-infrared imager and slit spectrometer – NIRISS – finished cooling off and joined the party.

NIRSpec is designed to measure The strength of different wavelengths of light Coming from the target. This information can reveal the composition and temperature of distant stars and galaxies. NIRSpec does this by looking at the target object through an aperture that blocks other light.

NIRSpec has multiple slots that allow it to do this See 100 items at once. Team members began testing the position of the multiple targets, instructed the hatches to open and close, and confirmed that the slots were responding correctly to commands. Future steps will measure and verify exactly where the cracks are pointing Multiple targets can be observed simultaneously.

NIRISS is a non-slitting spectrophotometer that will also refract light into its various wavelengths, but is better at Observe all things in the field, not just the things on the crevices. It has several modes, including two that are specifically designed to study exoplanets that are particularly close to their parent stars.

So far, device checks and calibrations have continued smoothly, and the results show that both NIRSpec and NIRISS will provide better data than engineers expected before launch.

Two images show a tangled web of stars and dust, but the image on the right is much clearer.

The MIRI camera, image on the right, allows astronomers to see the dust clouds incredibly clearly compared to previous telescopes such as the Spitzer Space Telescope, which produced the image on the left.
NASA/JPL-Caltech (left), NASA/ESA/CSA/STScI (right)/FlickrAnd the CC BY

4. What was the last tool you run?

The last tool to boot on Webb was the mid-infrared instrument, or MIRI. MIRI is designed to capture images of distant or newly formed galaxies as well as small, faint objects such as asteroids. This sensor detects the longest wavelengths of Webb’s instruments and must be kept at 449 degrees Fahrenheit – just 11 degrees Fahrenheit above absolute zero. If it’s warmer, the detectors will only pick up heat from the device itself, not the interesting stuff in space. MIRI . has Its cooling systemwhich needed more time to become fully operational before the device could be commissioned.

Radio astronomers have found hints that galaxies exist exactly Hidden in dust and undetectable by telescopes like Hubble which capture wavelengths of light similar to those visible to the human eye. The extremely cold temperatures allow MIRI to be incredibly sensitive to light in the mid-infrared range that can pass through dust more easily. When this sensitivity is combined with Webb’s large mirror, it allows MIRI to do so These dust clouds penetrate and reveal stars and structures In such galaxies for the first time.

5. What’s next for Webb?

As of June 15, 2022, all Webb tools are up and running and have taken their first images. In addition, four imaging modes, three time-series modes, and three spectral modes were tested and approved, leaving only three modes.

On July 12, NASA plans to Release a collection of humorous notes Describes Web capabilities. These images will show off the beauty of Webb’s images and will also give astronomers a real taste of the quality of the data they will get.

After July 12, the James Webb Space Telescope will begin working full time on its science mission. The detailed timeline for next year has yet to be released, but astronomers around the world are eagerly awaiting the recovery of the first data from the most powerful space telescope ever built.