James Webb Space Telescope Discovery

Webb Mirror Alignment Continues Successfully (Post-Global Alignment Image)

Webb continues on its path to becoming a focused observatory. The team has successfully worked through the second and third out of seven total phases of mirror alignment. With the completion of these phases, called Segment Alignment and Image Stacking, the team will now begin making smaller adjustments to the positions of Webb’s mirrors. After moving what were 18 scattered dots of starlight into Webb’s signature hexagonal formation, the team refined each mirror segment’s image by making minor adjustments, while also changing the alignment of Webb’s secondary mirror. The completion of this process, known as Segment Alignment, was a key step prior to overlapping the light from all the mirrors so that they can work in unison. Once Segment Alignment was achieved, the focused dots reflected by each mirror were then stacked on top of each other, delivering photons of light from each segment to the same location on NIRCam’s sensor. During this process, called Image Stacking, the team activated sets of six mirrors at a time and commanded them to repoint their light to overlap, until all dots of starlight overlapped with each other. In this image: This hexagonal image array captured by the NIRCam instrument shows the progress made during the Segment Alignment phase, further aligning Webb’s 18 primary mirror segments and secondary mirror using precise movements commanded from the ground. Credit: NASA/STScI Tags: test image engineering image Completed Segment Alignment
To complete the first stage of alignment, the team moved the primary mirror segments to arrange the dots of starlight into a hexagonal image array (bottom). Each dot of starlight is labeled with the corresponding mirror segment that captured it. Credits: NASA (top); NASA/STScI/J. DePasquale
This early Webb alignment image, with dots of starlight arranged in a pattern similar to the honeycomb shape of the primary mirror, is called an “image array.” Credit: NASA/STScI/J. DePasquale