The James Webb Space Telescope opens his eyes and offers us a selfie

A selfie of the James Webb Space Telescope (JWST) in orbit. Photo credit: NASA

Mirror, my beautiful mirror, who is the most beautiful?

Incredible! A selfie of the James Webb Space Telescope taken from its orbit around Lagrange Point L2.

There are no technical cameras or telescopic arms on the JWST board but I was hoping to see one or two images of the new space telescope once in orbit.

This is done and this is the NIRCam device that created this image for a special lens designed to capture the elements of the primary mirror. It is a configuration that is not used for scientific observation but is used exclusively at the calibration and alignment stages.

In this case, the part of the mirror that looks bright in this image is directed towards one star, the others are not perfectly aligned. This is a way to measure the current quality of alignment and prepare for the future.

For the NASA team involved in this work, this exceptional figure indicates that we are nearing the end of an important JWST verification phase.

Mirror effect, in 18 copies so as not to lose the answer …

A new constellation of 18 stars? A second image published by NASA shows a strange constellation seen through the NIRCam instrument and helps to understand how the alignment of the mirror elements is verified.

HD84406 - Big Dipper - NIRCam - JWST - James Webb Space Telescope - Calibration and Alignment - Primary Mirror - 18 Segment - NASA - First Picture - First Picture

HD 84406: Ursa Major has seen an isolated star in the constellation
The NIRCam instrument of the James Webb Space Telescope during its operation
Calibration and alignment of primary mirrors. Photo credit: NASA

Can you recognize Big Dipper? No? That’s normal … it’s a single star in 18 copies. This mosaic comes from the reflection of the same star by a part of the primary mirror.

The Star HD 84406 was chosen because it is relatively isolated, making it easy to detect in images.

The following image is an annotated version to identify each part of the primary mirror that made the mosaic the brightest spots of the same star. According to NASA, the results are consistent with what was expected at this stage of the alignment.

HD84406 - Big Dipper - NIRCam - JWST - James Webb Space Telescope - Calibration and Alignment - Primary Mirror - 18 Segment - NASA - First Picture - First Picture

HD 84406: Ursa Major has seen an isolated star in the constellation
The NIRCam instrument of the James Webb Space Telescope during its operation
Calibration and alignment of primary mirrors. Image Mosaic Annotation Version.
Photo credit: NASA

Within a few months, 18 bright points should overlap: the mirror parts would be fully aligned: JWST would be able to begin its scientific mission.

In the meantime, these calibration activities make it possible to “run in” the new telescope, all ground systems, and the determination of the parties participating in the in-flight adoption: to receive this virtual constellation of 18 stars from February 2, JWST brings 156 times the star HD 84406 across the moon’s equivalent area. Noticed. The 10 detectors of the NIRCAM instrument obtained 1560 images representing 54 gigabytes of raw data. The operation lasted a total of more than 24 hours.

Cold up front!

Obviously the directional calculations and the initial alignment of the primary mirror were quite good: the target star was seen in all 18 mirrors with less than 16 faces.

The image presented here is a very small extract of a large mosaic of about 2 billion pixels.

NIRCam was chosen for this purpose for two reasons:

  • S.A relatively wide field, suitable for such “thick pointing”.
  • Ability to operate safely at higher temperatures than other instruments, although this deviation from the rated temperature creates artwork in the figure.

The James Webb Space Telescope will gradually reach its nominal cryogenic temperature. The first images after the complete calibration of the three instruments should be released this summer.

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