Re:James Webb telescope's coldest instrument reaches operati...
by nomel on Tuesday April 19, 2022 @02:08PM
(#31086650)
I don't see anything that suggests a laser is being used in space. At 1:24 in the video, it says starlight is used. Only stars are mentioned in the press releases: https://www.universetoday.com/154623/heres-exactly-how-engin...
On the ground, you can easily place a laser in an optically identical position as a star (near infinity). In space, I don't think this would be possible, since it would require that the laser, and the optics that would be required, would all be within a fraction of a wavelength of the true optical path. In the end, you would still need to align to a star anyways.
Interferometry works just fine with starlight.
> To measure the shape of the Webb telescope’s primary mirror, engineers use a test device called an interferometer, which shines a laser down onto the mirror.
The next phase you’re referring to also uses a laser, but this time it’s shone off the mirrors into the actual scientific observation sensors, hence they describe it as being used as a source of artificial starlight.