Huge step for James Webb: these 18 images are united in one

Stages 2 and 3 of the alignment of the 18 segments of the James Webb Space Telescope have been successfully completed. Now a star can be captured as a single object, and not 18 different images.

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This is a great achievement for the development of the James Webb Space Telescope. The NASA just announced that phases 2 and 3 of the process of aligning the segments of the mirror went very well, this February 25, 2022. From now on, the image of a star can be observed as a single object, and not 18 different objects as was the case so far.

• Phase two consisted of segment alignment : it was necessary to make precise adjustments at the level of the mirrors so that the images are sharper. We see it on this gif broadcast on Twitter by NASA: it’s as if the “focus” had been done: the luminosity seems more restricted and less impasto: the image is better drawn.

• Phase three is called “image stacking” and it clearly the most visible: it is now a question of bringing together these 18 images of the same object, in a single one. ” To put all the light in one place, each segment image must be stacked, one on top of the other. In the image stacking step, we move the individual segment images so that they fall precisely in the center of the field to produce a unified image “says NASA.

Aligning James Webb mirrors takes 3 months in total

The alignment of James Webb’s mirrors is a very complex and very long process: NASA has three months just to complete these seven different stages.

« The telescope commissioning process will take much longer than previous space telescopes because Webb’s main mirror consists of 18 individual mirror segments that must work together as a single high-precision optical surface. “, can we read on the site from NASA.

Now that the third step is over, it now remains:

• Stage 4, the “grainy phasing” : even if the images have been stacked and the light is placed in the same place, ” the segments still act as 18 small telescopes rather than a single large one. They must therefore be aligned with each other “with an accuracy less than the wavelength of light”, explains NASA.
• Step 5, precise phasing: which makes it possible to correct and more precisely adjust the alignment of the segments.
• Step 6where one aligns the mirror to the other instruments
• Step 7where one flush out the last errors possible in mirror adjustment.

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