NASA releases first image from an in-focus Webb telescope
NASA releases first image from an in-focus Webb telescope
Distant galaxies come into focus as Webb is on track to meet or exceed expectations.
Today, NASA announced that it has successfully completed two further steps to align the mirrors of the Webb telescope. The resulting performance indicates that Webb will meet or exceed its design goals. "So far, we're finding that the performance is as good [as] or better than our most optimistic projections," said Lee Feinberg, the Webb optical telescope element manager.
The announcement was accompanied by a spectacular image that showed a sharp focus on the target star and included many in-focus galaxies in the backdrop.
Get in line
The Webb telescope's primary mirror is made up of an array of 18 individual segments that, once properly aligned, will act as a single large mirror. The initial steps of mirror alignment involved identifying the images from each segment and bringing those images together at a single point. That work was completed back in February. At this point, the light was all gathered in one place, but it wasn't necessarily taking an equal path from each segment, meaning the segments weren't acting as a single mirror.
Marshall Perrin, the Webb optical telescope element manager, said that the individual segments were microns away from being properly aligned. The final alignment would take the segments to a precision on the nanometer scale—"a few hundred atomic diameters is the level of precision we need here," Perrin said.
And we apparently have it. "We have now achieved what's called the diffraction limited alignment of the telescope," Perrin said. "The images are focused together as finely as the laws of physics allow. This is as sharp an image as you can get from a telescope this large."
"At no point in that process did we have any technical issues with the telescope—the biggest [surprise] is just how closely it matched the models and predictions from the ground," Perrin said. "Honestly, the team was giddy at times looking at this data."
More to come
At this point, the mirror is aligned to the telescope's primary instrument, the Near-Infrared Camera. The telescope, however, has four additional instruments, and the next few steps will see alignment with each of the remaining instruments so that the mirrors are positioned to perform well with all the hardware. In addition to NASA's ability to tweak the positioning, shape, and curvature of the segments, the secondary mirror and the instruments themselves can be shifted to ensure an alignment.
Final tweaking may take place after this process is complete, but after that, nothing will be left other than the ongoing calibration needed to keep everything aligned. According to NASA, the alignment process is expected to be complete by early May at the latest.
From there, the science can begin—Jane Rigby of Webb operations said that a full year of science observations has already been planned out. Everyone involved with Webb will admit that a few high-priority science targets that are expected to produce aesthetically beautiful images have been chosen, but nobody has said what those are yet.
For now, everyone is focused on the galaxies that have come into view behind the star being used for alignment. And researchers are hugely relieved that the process has gone well. As Rigby put it, "There are days on this project where, if things didn't work, we would have gone home." Instead, the whole process has gone forward smoothly.
Tom Zurbuchen, the administrator of NASA's Science Mission Directorate, said, "All the worries I had, they're all behind us now."
MMW
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