The James Webb Space Telescope team made another progress in aligning the observatory’s mirrors. The team has completed the first stage in this process. It is called “Segment Image Identification.” The resulting image shows that the team has moved each of Webb’s 18 primary mirror segments to bring 18 unfocused copies of a single star into a planned hexagonal formation.
The team has now begun the second phase of alignment, with the image array complete. The second phase of alignment is called “Segment Alignment.” The team will correct large positioning errors of the mirror segments and update the alignment of the secondary mirror, during this stage. This has made each individual dot of starlight more focused. The team will begin the third phase, when this “global alignment” is complete. The third phase is called “Image Stacking”. It will bring the 18 spots of light on top of each other.
Matthew Lallo, systems scientist and Telescopes Branch manager at the Space Telescope Science Institute said that they will steer the segment dots into this array. So, they will have the same relative locations as the physical mirrors. This familiar arrangement gives the wavefront team an intuitive and natural way of visualizing changes in the segment spots in the context of the entire primary mirror, during global alignment and Image Stacking. Scientists can actually watch the primary mirror slowly form into its precise, intended shape.