1.5 million kilometers from the Earth
the JWST progresses
towards its commissioning. To align his mirrors, he created a unique mosaic with the NIRCam instrument to look for the star HD 84406… And a surprise selfie, to keep us waiting during the long weeks of calibration.
Everything is in place to make us dream!
Mirror, my beautiful mirror…
This is the big step that remains to be completed before having the most powerful space telescope ever designed: the alignment of its 18 mirrors to form a single assembly 6.5 m in diameter! The task is difficult, even if the micromotors that manage the settings all respond to commands.
Alignment, also known as collimation, is a very long process, the first step of which has just been completed: taking photos to form a mosaic and very precisely identifying the current position of the mirrors relative to each other. . Meticulous work for the NIRCAM instrument, which required a lot of images: 1560 shots spread over 25 hours for 5 billion pixels and 54 GB of data! The shared and commented image only represents the center.
I will give you 18 times the stars
The result, which is not visually revolutionary, should not even have been presented to the public… But under pressure from social networks and many American media who demanded this “first image”, NASA published the mosaic, documented with the results of the different mirrors.
At the time of writing this article, the collimation process has already started: one by one, the mirrors are moved to first reform their “honeycomb” geometry (which allows them to be centered with respect to each other). others). Then they will be aligned so that the star HD 84406, which serves as a calibration target, is a single bright point whose light, well documented elsewhere, is most faithfully retransmitted to the four instruments. The process will take around 100 days and is going exactly as planned so far.
Selfie Grain
Never stingy with a little communication surprise, the agencies responsible for the Webb telescope have also published an astonishing selfie! NIRCam has several lenses, including this one which is only used during calibration and which allows the observation of the 18 primary mirrors.
We can clearly see in this photograph, taken with one of the segments aligned on a light source (not the Sun, it is fortunately far behind the telescope), that the other mirrors are slightly off axis. The same image in a few weeks may show beam coherence… But until then, patience for us and for the scientific teams: their tool is almost ready.
Source: NASA
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