James Webb Space Telescope reached another milestone in mirror alignment. The team completed Segment Alignment and successfully completed the second and third phases.
Completed Segment Alignment
NASA shared an earlier photo taken by the James Webb Space Telescope. While the moment was remarkable, the quality of the image was not. It showed a mosaic of 18 random stars, created by reflecting light back from Webb’s misaligned secondary. This would be the starting point for the team to focus their efforts on aligning the dots.
NASA explains that the team was faced with two challenges: First, confirm that NIRCam could collect light from celestial objects and secondly, identify starlight from the same star in each one of the 18 primary mirror segments.
The second and third stages of the seven-stage process are complete. Now the Webb telescope’s hexagonal signature hexagonal formation of 18 scattered dots is more refined and aligned. Segment Alignment, also known as Segment Alignment by NASA, was an important step before overlapping all mirrors light so they can work together.
Focus Stacking 18 Segments
NASA claims that Segment Alignment is achieved when the focused dots reflected from each mirror segment are stacked on top and combined at the same spot on the Webb’s NIRCam sensor. The team activated six sets of mirrors simultaneously and instructed them to repoint their lights to overlap until all the starlight was over each other.
This is the result: The image below shows significant progress compared to the state of Webb’s images less than a month earlier.
Lee Feinberg, manager of the optical telescope element for Webb at NASA’s Goddard Space Flight Center says, “We still have work ahead, but we are becoming increasingly satisfied with the results we see.” “Years spent planning and testing are paying off, and the team couldn’t be more excited for what the next few months and weeks bring.”
Although the segments have been properly aligned they still act as individual telescopes, rather than one large one. This is the final intent. NASA states that the segments must be aligned with each other at a distance of less than one wavelength of light.
Phase four of seven is called Coarse Phasing. Here, the NIRCam will capture light spectra of 20 pairs of mirror segments using the NIRCam.
NASA explained that “[Coarse Phasing] assists the team to identify and correct vertical displacement among the mirror segments, as well as small differences in their heights,” NASA says. This will allow the single dot in starlight to become sharper and more focused over the next weeks.