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.
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.”
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.
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