March 16, 2022, was a huge milestone for NASA’s James Webb Space Telescope (JWST): the alignment process of the telescope’s mirrors has finally been completed successfully and it produced the first unified, aligned, and bright image of a single star. NASA announces JWST’s optics are working as expected. The space telescope was reported to be “fully focused”.
The James Webb Space Telescope (JWST) was launched on December 25, 2021, at 12:20 UTC from Ariane Launch Complex No. 3 (ELA 3) at Guiana Space Centre in Kourou, French Guiana. An Ariane 5 heavy-lift space launch vehicle (the launch was designated Ariane flight VA256) put this Class-A payload into space.
On February 3, 2022, NASA has announced that the telescope detected its first photons.
On February 11, 2022, the JWST took its first photo of a single star (we saw multiple stars on that first photo, but the image was actually a mosaic of 18 images of the same star, HD 84406). The space telescope also took its first selfie that day.
JWST operates in a halo orbit (a periodic, three-dimensional orbit near one of the L1, L2, or L3 Lagrange points, see notes 1), circling around a point in space known as the Sun-Earth L2 Lagrange point (see notes 1), approximately 1,500,000 km (930,000 mi) beyond Earth’s orbit around the Sun.
Video: JWST Reaches Alignment Milestone, Optics Working Successfully
The official James Webb Space Telescope (JWST) channel has published a video:
Press release by NASA: James Webb Space Telescope Reaches Alignment Milestone, Optics Working Successfully
Following the completion of critical mirror alignment steps, NASA’s James Webb Space Telescope team expects that JWST’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 JWST’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 the JWST 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, JWST’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. JWST’s first full-resolution imagery and science data will be released in the summer.
1. Lagrange Points
In celestial mechanics, the Lagrangian points are positions in an orbital configuration of two large bodies where a small object affected only by gravity can maintain a stable position relative to the two large bodies.
The Lagrange points mark positions where the combined gravitational pull of the two large masses provides precisely the centripetal force required to orbit with them. There are five such points, labeled L1 to L5, all in the orbital plane of the two large bodies. The first three are on the line connecting the two large bodies and the last two, L4 and L5, form an equilateral triangle with the two large bodies. The two latter points are stable, which implies that objects can orbit around them in a rotating coordinate system tied to the two large bodies.
- Press release: “NASA’s James Webb Space Telescope (JWST) Reaches Alignment Milestone, Optics Working Successfully” on the NASA website
- “The James Webb Space Telescope (JWST) has taken its first aligned image of a star. Here’s how it was done.” on The Conversation website
- James Webb Space Telescope on Wikipedia