Webb Space Telescope Reaches Alignment Milestone – Optical Performance at or Above Expectations

Webb Space Telescope Mirror Alignment

Webb mirror alignment animation. Credit: NASA

Following the completion of critical mirror alignment steps, the NASA/ESA/CSA James Webb Space Telescope team expects that Webb’s optical performance will be able to meet or exceed the science goals the observatory was built to achieve.

On 11 March, the Webb team completed the stage of alignment known as “fine phasing.” At this key stage in the commissioning of Webb’s Optical Telescope Element, every optical parameter that has been checked and tested is performing at, or above, expectations. The team also found no critical issues and no measurable contamination or blockages to Webb’s optical path. The observatory is able to successfully gather light from distant objects and deliver it to its instruments without issue.

Although there are months to go before Webb ultimately delivers its new view of the cosmos, achieving this milestone means the team is confident that Webb’s first-of-its-kind optical system is working as well as possible.

Webb Telescope Alignment Evaluation Image

While the purpose of this image was to focus on the bright star at the center for alignment evaluation, Webb’s optics and NIRCam are so sensitive that the galaxies and stars seen in the background show up. At this stage of Webb’s mirror alignment, known as “fine phasing,” each of the primary mirror segments have been adjusted to produce one unified image of the same star using only the NIRCam instrument. This image of the star, which is called 2MASS J17554042+6551277, uses a red filter to optimize visual contrast. Credit: NASA/STScI

With the fine phasing stage of the telescope’s alignment complete, the team has now fully aligned Webb’s primary imager, the Near-Infrared Camera, to the observatory’s mirrors.

Over the next six weeks, the team will proceed through the remaining alignment steps before final science instrument preparations. The team will further align the telescope to include the Near-Infrared SpectrographMid-Infrared Instrument, and Near InfraRed Imager and Slitless Spectrograph. In this phase of the process, an algorithm will evaluate the performance of each instrument and then calculate the final corrections needed to achieve a well-aligned telescope across all science instruments. Following this, Webb’s final alignment step will begin, and the team will adjust any small, residual positioning errors in the mirror segments.

Webb NIRCam Alignment Selfie

This new “selfie” was created using a specialized pupil imaging lens inside of the NIRCam instrument that was designed to take images of the primary mirror segments instead of images of the sky. This configuration is not used during scientific operations and is used strictly for engineering and alignment purposes. In this image, all of Webb’s 18 primary mirror segments are shown collecting light from the same star in unison. Credit: NASA/STScI

The team is on track to conclude all aspects of Optical Telescope Element alignment by early May, if not sooner, before moving on to approximately two months of science instrument preparations. Webb’s first full-resolution imagery and science data will be released in the summer.

Webb is the world’s premier space science observatory and once fully operational, will help solve mysteries in our Solar System, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it.

Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).

For more on this major milestone, see NASA’s $10 Billion Webb Space Telescope Reaches Huge Milestone.

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