NASA expects that, following the completion of the vital mirror alignment steps, the James Webb Space Telescope will succeed in its operation.
What have the completed stages revealed?
On 11 March 2022, the Webb telescope 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.
Furthermore, the team also discovered that there were no critical issues, no measurable contamination, and no blockages to Webb’s optical path. Thus, 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, and achieve the milestone it was set out to, 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,” explained Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in Washington. “Today we can say that design is going to deliver.”
What is the James Webb Space Telescope?
Some of the largest ground-based telescopes on Earth use segmented primary mirrors. However, the James Webb Space Telescope is the first telescope in space to employ such a design.
The 21-foot, 4-inch (6.5-metere) primary mirror – much too big to fit inside a rocket – is made up of 18 hexagonal and beryllium mirror segments. It had to be folded up for launch and then unfolded in space before each mirror was adjusted – to within nanometres – 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,” observed 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,” added Ritva Keski-Kuha, deputy optical telescope element manager for Webb at NASA Goddard. “We now know we have built the right telescope.”
What are the next steps for the telescope?
Over the next six weeks, the team will proceed through the remaining alignment stages before proceeding with the final science instrument preparations.
Researchers will further align the telescope to include the Near-Infrared Spectrograph, Mid-Infrared Instrument, Near InfraRed Imager, and Slitless Spectrograph. In this phase of the process, an algorithm will evaluate the performance of each instrument and 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 Webb Telescope team is on track to conclude all aspects of Optical Telescope Element alignment by early May 2022, 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 leading space science observatory and once fully operational, it will help solve mysteries in our solar system, allow scientists to look beyond into distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it.
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