The James Webb Space Telescope has despatched again its first photos, a “selfie” displaying the 18 hexagonal segments of its 6.5-metre (21.3-foot) major mirror and 18 matching, misaligned views of a star close to the bowl of the Big Dipper. And that’s precisely what they had been hoping to see within the preliminary phases of a fancy mirror alignment course of.
“This amazing telescope has not only spread its wings, but it has now opened its eyes,” stated Lee Feinberg, Webb optical parts supervisor.
A mosaic displaying all 18 blurry reflections exhibits their present post-launch alignment and can function a information for engineers, commanding actuators on the again of every phase, to ultimately goal all of the beams on the similar level to supply sharply targeted mild to Webb’s 4 science devices.
So far, Feinberg stated, the work has gone easily, however “I want to caution … that it’s still very early.”
“We don’t have detailed evaluations of everything at this point,” he advised reporters throughout a teleconference on 11 February. “But from our preliminary evaluations, everything is matching the models as well as we would expect the models to work at this point.”
Webb’s mirrors and its 4 devices are nonetheless cooling all the way down to the ultra-low, near-absolute-zero temperatures required to detect the faint infrared mild emitted from the primary stars and galaxies to kind within the wake of the Big Bang.
But one of many devices, the Near Infrared Camera – NIRCam – already is chilly sufficient for its detector to register the sunshine of a goal star in Ursa Major referred to as HD 84406.
“As planned, we pointed the telescope at a bright, isolated star, and we found and identified 18 spots for the 18 primary mirror segments,” Feinberg stated. “At this level, we’ve been capable of analyse a number of engineering photos that assist us perceive the alignments and the mirrors themselves.
“And we don’t see anything of concern. This is the first time we’re getting data on mirrors that are actually at zero gravity and using starlight to illuminate the primary mirror. And again, so far the data is matching our models and expectations.”
Engineers anticipated the mirror segments to be misaligned by as much as a millimetre at first of the alignment course of. To ensure that the goal star may very well be seen by all 18, greater than 1,500 photos had been taken over a area of the sky the scale of a full moon.
As it turned out, all 18 photos had been clustered inside the first 10 p.c of the search space, indicating the telescope got here via launch with the anticipated coarse alignment.
Over the following a number of weeks, engineers will transfer the segments in tiny increments, verify the alignment after which alter them once more as wanted in an iterative course of designed to maneuver the mirrored beams to the middle of Webb’s optical axis. The purpose is to stack, or merge, them right into a single beam, attaining the razor-sharp focus of a single 6.5-metre mirror.
After that, Webb’s science devices will likely be examined and calibrated, setting the stage for the primary science observations within the June timeframe.
