Webb continues on its way to becoming a focused observatory. The team successfully worked through the second and third phases of a total of seven mirror alignment phases. With the completion of these two phases, called Segment Alignment and Image Stacking, the team will now begin making smaller adjustments to the positions of the Webb mirrors.
This hexagonal image array captured by the NIRCam instrument shows the progress made through the segment alignment phase, further aligning the 18-segment primary mirror segment and the secondary mirror using precise movements required by the ground. Credit: NASA/STScI
After transferring what used to be 18 scattered points of starlight into Webb’s distinctive hexagonal formation, the team refined the image of each mirror segment by making slight adjustments, while also changing the alignment of the secondary Webb mirror. Completing this process, known as Segment Alignment, was an essential step before light from all the mirrors interfered so they might work in unison.
This gif shows the “before” and “following” images of the segment alignment, when the team corrected the large positioning errors of their primary mirror segments and updated the secondary mirror alignment. Credit: NASA/STScI
Once segment alignment was achieved, the focused points reflected by each mirror were stacked on top of each other, delivering photons of light from each segment to the same location on the NIRCam sensor. During this process, called Image Stacking, the team activated groups of six mirrors at a time and instructed them to reset their light to overlap, so that all the points of starlight overlapped each other.
During this phase of the alignment known as image stacking, the individual cross-sectional images are moved so that they are precisely in the center of the field to produce a uniform image instead of 18. In this image, all 18 segments are on top of each other. other. After further alignment steps, the image will be clearer. Credit: NASA/STScI
said Lee Feinberg, director of the Webb Optical Telescope Element at[{” attribute=””>NASA’s Goddard Space Flight Center. “Years of planning and testing are paying dividends, and the team might not be more excited to see what the next few weeks and months bring.”
Although Image Stacking put all the light from a star in one place on NIRCam’s detector, the mirror segments are still acting as 18 small telescopes rather than one big one. The segments now need to be lined up to each other with an
The team is now beginning the fourth stage of mirror alignment, known as coarse gradient, in which NIRCam is used to capture light spectra from 20 separate pairs of mirror segments. This equipment helps identify and correct vertical offsets between mirror segments, or small differences in their heights. This will make the single point of starlight gradually more intense and focused over the next few weeks.
