Webb Telescope Reaches Major Milestone: All its Light is in One Place
upstart writes:
Webb Telescope reaches major milestone: All its light is in one place:
Today, NASA shared an image indicating that it had successfully completed the image alignment stage of commissioning the James Webb Space Telescope. The Webb's primary mirror is composed of 18 individual segments, and, as of today's update, all of those segments are aligned so that a single star shows up as a single object. While there are still several more focusing steps required, the path to commissioning the telescope keeps getting shorter.
[...] Earlier this month, however, tweaks to the mirrors created a hexagonal array of smears that replicated the arrangement of the primary mirror segments. Today's announcement saw the segments shifted so that each of the smears was partly focused and moved to the center of the secondary mirror. The result? The star that's being imaged for this process is now a single dot at the center of the telescope's field of view.
NASA isn't done just yet, however. Although all the images are in the same place, they're simply superimposed there. The ultimate goal is to have the segments behave as a single mirror, which requires more careful focusing. To do so, engineers will image the spectra of the light, looking for slight shifts of the image locations at different wavelengths. From that, it's possible to figure out which way the mirrors must be shifted to fine-tune the mirror segments.
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