We’ve just seen the first up-close view of the James Webb Space Telescope hard at work in deep space.
A special lens within the telescope’s near-infrared camera (NIRCam) instrument allowed engineers to take a look at Webb’s mirror alignment and to generate a cool view of the telescope, all at the same time. Engineers now also have the assurance that NIRCam is successfully receiving light, which is crucial for its ultimate goal of helping to image objects in space.
“I think pretty much the reaction [to the selfie] was, ‘Holy cow,’ ” Lee Feinberg, Webb optical telescope element manager at NASA Goddard Space Center, said of his team’s reaction to the selfie during a media update about the spacecraft’s first images Friday (Feb. 11).
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“Even when we tested in Houston, we didn’t have starlight illuminating the primary mirror in this configuration. So this was actually a new thing for us,” Feinberg said, clarifying that testing on Earth was performed with lighting diodes.
The new NIRCam view, he noted, “wowed the team, and that’s one of the reasons I think people wanted to share it.”
Bonus image! When it’s time to focus, sometimes you need to take a good look at yourself.This “selfie” taken by Webb of its primary mirror was not captured by an externally mounted engineering camera, but with a special lens within its NIRCam instrument. #UnfoldTheUniverse pic.twitter.com/XtzCdktrCAFebruary 11, 2022
NIRCam is capable of taking images of the 18 primary mirror segments, and it generated the selfie for engineering and alignment purposes, NASA said on its blog Friday (Feb. 11). The image shows a bright mirror segment pointing to a bright star, while the others are not yet aligned in that direction. Engineers are moving the mirrors into alignment for eventual science observations in a few months.
“NIRCam will be used throughout nearly the entire alignment of the telescope’s mirrors,” NASA said of the alignment process. “It is, however, important to note that NIRCam is operating far above its ideal temperature while capturing these initial engineering images, and visual artifacts can be seen in the mosaic.”
As Webb continues to cool, the “artifacts” will lessen and the telescope will be better primed to do its work, NASA added. The telescope is designed to work in infrared (heat-seeking) wavelengths and thus needs to be quite cool to accomplish this work.
Webb’s position at a Lagrange point keeps it far away from the heat of the sun and the Earth, and a sunshield prevents light from falling accidentally on the telescope’s instruments or optics.