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. Credits: NASA/STScI
Following the completion of critical mirror alignment steps, NASA’s 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 March 11, 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.
“More than 20 years ago, the Webb team set out to
build the most powerful telescope that anyone has ever put in space and came up
with an audacious optical design to meet demanding science goals,” said Thomas
Zurbuchen, associate administrator for NASA’s Science Mission Directorate in
Washington. “Today we can say that design is going to deliver.”
While some of the largest ground-based telescopes on
Earth use segmented primary mirrors, Webb is the first telescope in space to
use such a design. The 21-foot, 4-inch (6.5-meter) primary mirror – much too
big to fit inside a rocket fairing – is made up of 18 hexagonal, beryllium
mirror segments. It had to be folded up for launch and then unfolded in space
before each mirror was adjusted – to within nanometers – to form a single
mirror surface.
“In addition to enabling the incredible science that
Webb will achieve, the teams that designed, built, tested, launched, and now
operate this observatory have pioneered a new way to build space telescopes,”
said Lee Feinberg, Webb optical telescope element manager at NASA’s Goddard
Space Flight Center in Greenbelt, Maryland.
NASA’s Webb Reaches
Alignment Milestone, Optics Working Successfully. Credits: NASA's Goddard
Space Flight Center
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.
“We have fully aligned and focused the telescope on a star, and the
performance is beating specifications. We are excited about what this means for
science,” said Ritva Keski-Kuha, deputy optical telescope element manager for
Webb at NASA Goddard. “We now know we have built the right telescope.”
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. Credits: NASA/STScI
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 Spectrograph, Mid-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.
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 program led by NASA with its partners at ESA (European Space Agency) and the Canadian Space Agency.
For more information about the Webb mission, visit: https://www.nasa.gov/webb
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