Updated 5:55 p.m. Eastern with comments from post-deployment press conference.
WASHINGTON — The primary mirror of NASA’s James Webb Space Telescope unfolded into place Jan. 8, completing the major steps in the post-launch deployment of the giant observatory.
Controllers issued commands to deploy an assembly called the starboard primary mirror wing, containing 3 of the 18 segments of the primary mirror. The wing was folded against the side of the spacecraft for launch, and over the course of about three hours a motor moved it into position and it was then locked into place. A similar wing on the other side of the primary mirror moved into place Jan. 7.
The deployment of the two mirror wings marked the end of the major deployments of the space telescope that started shortly after its Dec. 25 launch on an Ariane 5. Those efforts, which included deployment of the primary and secondary mirrors, its large sunshade and other devices such as a solar panel and antenna, took place without any major problems.
“The last two weeks have been totally amazing,” Bill Ochs, program manager for JWST at NASA’s Goddard Space Flight Center, told controllers in the mission operations center after the mirror wing latched into place.
He thanked both the team of engineers who oversaw the deployment as well as those at Goddard and Northrop Grumman, the prime contractor for the mission, who stowed the spacecraft into its launch configuration last year. “If they hadn’t done it perfectly, these last two weeks would not have gone as well as they had.”
“It’s not as easy as it looks,” Ochs said at a later press conference, stating that, in retrospect, the mission went through the “exact right amount” of testing, engineering audits and changes to the design. “The fact that it looked easy just emphasizes that we did all the right things leading up to this moment.”
The deployments mark only the end of one phase of the commissioning of the $10 billion space telescope. Over the next several months engineers will align the optics of the telescope mirrors as well as check out the observatory’s four instruments. The spacecraft itself will perform a maneuver on approximately Jan. 23 to enter a halo orbit around the Earth-sun L-2 Lagrange point, 1.5 million kilometers from Earth. JWST is scheduled to be ready to start science operations about six months after launch.
Lee Feinberg, optical telescope element manager for JWST at Goddard, said at the briefing that the mirrors will not be fully aligned until about four months into the mission. “We expect them to be very misaligned” at first, he said, with a meticulous process to get the mirrors aligned to within a fraction of a wavelength. “It’s a little bit of a long process, but at the end of it we expect to see an image of a star that looks like a star.”
“This telescope is not ready out of the box. The first images are going to be ugly,” said Jane Rigby, JWST operations project scientist at Goddard. She said NASA doesn’t plan to release those images, waiting until the telescope is fully aligned and the instruments ready. “We want to make sure that the first images that the world sees, that humanity sees from this telescope do justice to this $10 billion telescope.”
Project officials noted before the launch of JWST that there were 344 single-point failures with the spacecraft, primarily associated with the deployment system. Mike Menzel, mission systems engineer for JWST at Goddard, says that, with the main deployments completed, all but 49 of those failures have been retired. “These 49 are typical for all missions,” he said, like the spacecraft’s propulsion system and instruments. In some cases, he added, those failures would only affect certain science goals, and not the overall mission itself.
He also said that the accurate launch of the spacecraft should extend its life by reducing the propellant it has to use to reach L-2. “We have quite a bit of fuel margin right now relative to 10 years,” the planned science lifetime of the mission. “Roughly speaking, it’s around 20 years of propellant.” NASA previously stated that the accurate launch would “significantly” extend its lifetime, but had not given a figure before now.
Despite the work ahead, NASA officials celebrated the milestone of completing deployments. “While the journey is not complete, I join the Webb team in breathing a little easier and imagining the future breakthroughs bound to inspire the world,” NASA Administrator Bill Nelson said in a statement. “Each feat already achieved and future accomplishment is a testament to the thousands of innovators who poured their life’s passion into this mission.”
Thomas Zurbuchen, NASA associate administrator for science, noted on a NASA TV telecast of the final deployment steps that he had not shaved since the launch, a move he compared to the “playoff beards” that professional athletes grow. He intended the beard to grow until JWST was completely deployed.
As the final mirror wing folded into place, he said he was confident that beard would not be around much longer. “I fully expect to shave today.”