The James Webb Space Telescope’s primary mirror is “all deployed, all together”

On Saturday, NASA made history.

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webb mirror unfolding
Northrop Grumman

The James Webb Space Telescope is now, finally, a fully deployed telescope. On January 8, 2022, NASA made history by successfully unfolding the telescope’s primary mirror — the largest of its kind ever sent into space.

What’s new — NASA’s flagship observatory successfully unfolded the starboard wing of the honey-comb-like beryllium and gold mirror at 10:28 a.m. Eastern. The starboard wing is the final piece of the spacecraft to unfold from its compact launch configuration. The mission team confirmed the primary mirror is fully latched — in other words, fully deployed — at around 1.18 p.m. Eastern on January 8. The latching process took several hours to complete, featuring 20 motor movements and multiple checks along the way, each of which represents its own milestone.

To do it, the team first had to successfully fire 178 release pins — all 178 had to work perfectly to unfold the mirror. The final four pins were particularly critical, as they released the restraints that had held Webb’s mirror in place during launch.

Thomas Zurbuchen, the associate administrator at NASA, described himself as “emotional,” following the deployment in a live broadcasting Saturday. He added: “I fully expect to shave today.” Zurbuchen had held off on shaving his beard until the telescope was “all deployed, all together,” he says in the broadcast.

The space agency began live coverage of the mirror deployment at 9:30 a.m. Eastern Saturday. During the coverage, while mission scientists swigged iced coffee and bopped to Anita Ward’s “Ring My Bell,” NASA showed a simulation of the telescope as it deployed. This marks the last stage of a metamorphosis which saw the telescope emerge like a butterfly from a chrysalis once it is situated in its home at Lagrangian Point 2 (L2).

The unfolding, via Twitter.

For astronomers such as Heidi Hammel, an interdisciplinary scientist on the project who has been involved with the telescope since the early 2000s, it felt pretty good to see that final mirror wing swing and lock into place, capping an incredibly successful sequence of deployments that began right after launch on Christmas Day, 2021.

“It’s just going so smoothly, I think all of us are waiting for the first shoe to drop, or something, you know? So knock on wood,” Hammel tells Inverse. “I think this just shows you that all the testing, all of the troubleshooting, all of the modeling that took so long on the ground is paying off.”

Why it matters — The James Webb Space Telescope now has its power, navigation, communication, and light-focusing capabilities intact and in a position to do science — but we will still need to wait another five months or so for that.

One problem James Webb may soon be able to solve is a “chicken-and-egg problem,” as Zurbuchen explained in the broadcast: Namely, how black holes and galaxies evolve, and whether their development is intertwined.

How Webb will enter orbit around L2


The James Webb Space Telescope: Journey to L2

The telescope’s long journey through space was preceded by an even longer trip through time, beginning with its birth as an idea in the early 1980s. And while headlines during its decade’s-long development often focused on the many delays and cost of the roughly $10 billion space telescope, the measured pace also ensured engineers had the time to test everything as much as possible.

After all, no one has tried anything remotely like this telescope before. Without human hands in space to assemble it, the telescope was built to unfold independently.

“This was a crazy thing to do to take this massive telescope and fold it up and put it in a rocket,” Hammel says. “Normally, you build a telescope and launch it as is. We’ve just never done one of these where you've got the mirrors folded up, for heaven’s sake.”

This animation shows one of the mirrors swinging into position.


The telescope is currently more than 600,000 miles away — it has some way to go before it reaches its destination of Lagrangian Point 2, or L2, about one million miles from Earth. It will be far from human reach — too far for a repair mission/

There are still myriad small tests it needs to complete before it is safe to start scientific observations, like:

  • Turning heaters on and off
  • Unlatching and then focusing all 18 hexagonal beryllium of the primary mirror
  • Tuning, testing, and commissioning all of the telescope’s instruments

JWST’s recent milestones— After myriad delays, the observatory safely launched from French Guiana aboard a European Space Agency Ariane 5 rocket on December 25, 2021. It immediately began the long series of deployments necessary to fully unfold into a working space telescope.

Within hours of launch, the telescope had successfully deployed its solar panels, high gain antenna, and conducted the first of three planned course correction burns.

NASA later confirmed the launch and burns were made so precisely that Webb would retain more propellant than initially thought, which could extend its operational life beyond the hoped-for 10 years.

Since then, the James Webb Space Telescope has successfully deployed and pulled taut its five-layered sun shield, which is essential for keeping the heat and light of our Sun away from the telescope’s exquisitely sensitive infrared instruments. On January 5, the telescope completed one of the most crucial deployments, that of its secondary mirror, without which the telescope would be effectively blind.

“I was so nervous about that all day,” Hammel recalls. “But it all worked great!”

Webb folded up prior to launch in French Guiana.


And now the primary mirror is fully deployed, too. The telescope could have functioned without the starboard wing of the primary mirror had the full deployment failed, but it would not have had the same light-gathering power, or been able to see as deep into the cosmos. In this case, it would have been similar to a person having a small scratch on their eye — you’d still be able to see, just not as clear in some areas, according to NASA engineer Julie Van Campen, who participated in Saturday’s broadcast.

“These are all the big moves to get the telescope created into an actual functioning telescope,” Hammel explains.

Whatever else happens, astronomers know they’ll “have the full power of the telescope, focusing light into the instruments,” she adds.

What’s next for the James Webb Space Telescope

There’s still a lot left for NASA to do before JWST can start performing any science, beginning with finishing its journey to and entering orbit around L2, a point where the Earth and Sun’s gravity cancel out, allowing it to move around our star with Earth permanently at its back.

Hammel likens it to completely remodeling a kitchen. The telescope is now at the point where the new walls are up, the counters and cabinets are in, but the plumbing, electricity, and appliances still need to be hooked up and checked out.

“The telescope is now structurally complete,” she says, but “substitute photons for water and instruments for plumbing, and we still need to get all those other things done as well.”

The James Webb Space Telescope is due to reach L2 on January 25, where it will begin a long “commissioning” period, as Hammel puts it in a recent blog post.

The next few months for JWST.

AURA / S. Lifson

Each primary mirror segment can and must be adjusted so that the mirror functions as a whole, and then finely tuned to generate sharp images on the telescope’s instruments. The instruments themselves must be cooled to minus 388 degrees Fahrenheit and then aligned and calibrated. Proper operation and focus will depend on gravity, temperature, and the mirrors’ individual calibrations.

All told, it will likely be sometime in the summer before the telescope can finally turn its eyes toward the universe.

“None of us are going to really breathe the big sigh of relief until we’re all fully focused and all of our instruments are demonstrating that they’re working,” Hammel says.

Editor’s note: This is an unfolding story and it will be updated as needed.

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