The James Webb Space Telescope is already fully deployed, in its definitive orbit and at temperatures close to those of operation. But it will be months before mission controllers manage to line up the 18 hexagonal segments of their mirror to work as one.
The NASA published on Friday the first image generated with the NIRCam near-infrared camera, which will be used to calibrate the Webb telescope. It might look like a blurry photo of an array of stars, but it is light from the same star reflected 18 times by the mirror segments.
Scientists pointed Webb at the star HD 84406 in a process that began on February 2. This isolated star in the Ursa Major constellation was chosen because it is easily identifiable and has no similarly bright objects nearby, which helped reduce background interference.
Webb tracked the star at 156 different positions and used NIRCam’s 10 detectors to generate a total of 1,560 images. Mission controllers received more than 54 gigabytes of data and mosaicked it as a reference to start mirror alignment.
The image above shows only the central part of the original mosaic, which is over 2 billion pixels, but the light from all 18 segments was concentrated on this central fragment, which matches the expectations of scientists and is an excellent starting point for the alignment process.
NASA engineers and optics experts will use this image to determine the positions of each segment of the mirror behind the telescope deployment and obtain functional alignment for scientific operations.
The scientists used also a pupil lens inside the NIRCam instrument to get a selfie from the 18 mirror segments. These types of images will only be captured during the alignment process, so they will be the last photos that we see from the telescope itself.
The NIRCam is one of the four scientific instruments aboard the Webb. It is designed to operate at -233 ºC, but it is currently at a higher temperature, so its images still have visual artifacts. As the telescope continues to cool and its mirrors align, Webb images will be clearer, more detailed and complex. The first scientific images from the telescope are expected arrive this summer.
