Webb telescope: First part of the fine adjustment successful

The next milestone: The James Webb Space Telescope has completed another important step. The 18 partial areas of its 6.20 meter large primary mirror are now aligned and adjusted to such an extent that a first sharp image is created. This ensures the function of the first of four optical instruments of the telescope, as announced by NASA. Now comes the fine-tuning to the three remaining instruments.

The James Webb Space Telescope is the largest and most expensive instrument ever launched into space – and by far the most complicated. Because its mirrors and the sun shield could only be unfolded in space in a complex and multi-step process. Since the telescope arrived at its place of work, Lagrange point 2, 1.5 million kilometers away from us, the 18 mirror segments and optics have been adjusted – precision work down to a few nanometers.

First light from the mirror to the NIRCam

Now NASA also reports a first important success with the fine adjustment: The 18 segments of the primary mirror are now so well aligned that the Webb telescope delivered the first sharp picture. “We aligned and focused the telescope on a star and its performance exceeds all expectations,” says Ritva Keski-Kuha of NASA’s Goddard Space Flight Center. “Now we know that we built the telescope correctly.”

With this first step of fine adjustment, the optical path from the large primary mirror of the telescope via the secondary and tertiary mirror is now concrete up to the Near-Infrared Camera (NIRCam). This instrument is the main camera of the Webb telescope and is specially designed to image objects in the near-infrared range in great detail. A whole array of tiny apertures makes it possible to selectively cover or focus on individual image areas.

Sharp image

The first recordings of a test star resulted in a clear image in which the radiation of the 18 mirror segments in the NIRCam is almost perfect superimposed on the overall picture. Even the galaxies in the background of the test shot are already sharp. This means that the first of the space telescope’s four optical instruments has now proven to be functional – to the great relief of the NASA team.

“More than 50 years ago, the Webb team began planning and building the most powerful telescope ever put into space,” said NASA Administrator Thomas Zurbuchen. “A bold optical design was developed to meet the ambitious scientific goals. Now we can say that this design will deliver.”

Webb Telescope Passes First Alignment Milestone.© James Webb Space Telescope (JWST)

What Happens Next

As a next step, the optical paths to the remaining three telescope instruments will also be adjusted and tested over the next six weeks – the Near-Infrared Spectrograph, the Mid-Infrared Instrument and the Near InfraRed Imager and Slitless Spectrograph. This part of the fine-tuning should be completed by early May. This will be followed by around two months in which the functions of the individual scientific instruments will be tested. The James Webb telescope will then send the first real images back to earth in early summer.

Source: NASA

18. March 2022

– Nadja Podbregar

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