James Webb’s mirrors are perfectly aligned, what’s up?

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[EN VIDÉO] One minute to understand the deployment of the James-Webb space telescope
After launching into space on December 25, 2021, the James Webb Space Telescope will travel for 29 days to the Lagrange L2 point, 1.5 million kilometers from Earth. During this period, the JWST will deploy its instruments gradually, in order to be operational when it arrives at the site.

He Nasa announced on Thursday, April 28 that the lineup of mirrors of the James-Webb is now complete. After a general overhaul, all teams unanimously concluded that the James Webb Space Telescope is fully capable of making observations and images with each of the instruments.

It took months to align the mirrors, according to a procedure which had seven stages. It started with a rough lineup to make sure the received light reaches the focal point. As a reminder, the main mirror of the James-Webb is so wide – six meters in diameter – that it has had to be folded to fit everything into the fairing of the rocket. Ariadne 5 who sent him into space last Christmas.

It was after a final series of iterations that the alignment procedure finally ended

The procedure then continued with the alignment of each of the eighteen hexagonal sections of the primary mirror as well as the secondary mirror. The goal was to be able to stack the received images for each section into one. To continue, the teams perfected the positions of the different sections of the primary mirror and then ensured that the optical path was optimal for each of the instruments. It was after a final series of iterations that the alignment procedure finally ended.

We remind you that all operations have been done automatically remotely and with the utmost caution! In fact, we can’t launch a first aid operation since telescopes as NASA has done on several occasions with Hubble using the space shuttle, or as proposed by the Chinese space agency through placement the future Xuntià space telescope the same orbit than theirs Space station. Other way roundthe James-Webb is much farther than the lower orbit, 1.5 million kilometers from Earth, a Lagrange point L2 of the Earth-Sun system.

The alignment of NASA’s James-Webb Space Telescope has already been completed. © Nasa

It’s time to test instruments!

At the end of the mirror alignment phase, the James-Webb is fully operational. However, he is not yet ready to do science. There is still a lot of testing to be done with the instruments. This new preparation phase is expected to take two more months, according to NASA, for scientific operations to begin in July.

From now on, the corrections to the mirrors will be very minimal, that is, very small adjustments. The telescope is already perfectly focused light in each of them, with optical performance “ beyond the most optimistic predictions of engineers according to NASA. However, teams will check the alignment of the mirrors every two days and apply corrections if necessary. In addition, during the various tests of the upcoming instruments, the telescope will make many observations, which will allow engineers to confirm their proper operation.

Each of the four scientific instruments is extremely complex. During the rehearsals there will be a ballet of the different combinations they may have in order to see if the lentils, sensors, masks, filter wheels and other equipment work properly. There are many calibrations in the program.

In fact, the teams responsible for its instrument have been testing for weeks now, taking advantage of the images they may receive about mirror alignment operations. But some instruments had to be put in special conditions to work well. This is the case with the Mirim instrument provided by Cnes, which had to be cooled to only seven degrees above absolute zero, ie -266 ° Celsius. This is ideal for eliminating any noise in an infrared signal and is essential for obtaining data that meets the expectations of scientists.

The four instruments will be used to observe the infrared universe. NIRCam is a wide field camera watching wavelengths between 0.6 and 5 microns. NIRSpec is your partner spectrometer to analyze infrared signals from compact sources and distant galaxies. Mirim observes in the middle infrared (between 5 and 28 microns), which is interesting for analyzing interstellar clouds composed of gas and dust. Finally, NIRISS is a secondary instrument that can do spectra great field.

The James-Webb Space Telescope aligns its mirrors

Article by Daniel Christianpublished March 7, 2022

This is a scenario for any telescope, be it your niece’s or the most powerful space telescope ever sent into history. Ever since James-Webb managed to capture his first photonsthe teams are following this long three-month process that will end in the spring.

A month ago, NASA announced that the NIRCam instrument (infrared camera), the main image of the James-Webb, detected its first rays of light. This means that the rays have traveled all the way through the telescope, guided by the different mirrors of structure. Since, the NASA team began aligning the 18 sections of the primary mirror.

The work is extremely accurate, considering the scientific requirements of the American space telescope. To imagine this, you have to imagine that if the primary mirror is the size of the United States, each section would be the size of Texas, and you would have to adjust its height to an accuracy of 3.8. centimeters!

The process has seven phases. In late February, the team completed phases two and three. These two phases consisted of fine-tuning the alignments of each section and the secondary mirror, and then stacking the received images for each section into a single image.

The fourth phase has begun

These are now “thick” alignments before moving on to phase five, which involves perfecting the position of the sections of the primary mirror. These two phases should last several weeks. The next step will be to align the mirrors with the fields of view of scientific instruments. Finally, the final phase will consist of final corrections iteratively. Thus, according to NASA, the telescope it will be operational in the spring, but will have to wait until the end of the summer to have the highest quality.

While waiting for phase five, NASA did announcement that the team of spectrograph in James-Webb’s upcoming European Infrared NIRSpec has successfully verified three essential mechanisms for the proper functioning of the instrument.

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