Lee Feinberg was on vacation, and he deserved it. It was late May, and Feinberg, a manager at NASA’s Goddard Space Flight Center, had spent “an incredibly tense several months” leading the effort to carefully deploy the mirrors on the world’s newest and most powerful space telescope, making sure that each of the gold-coated tiles—18 in all, arranged in a honeycomb shape—was properly aligned. The success of the ambitious observatory, designed to capture the sharpest images of the most distant stars and galaxies, depended on it. So when the work was done, and the process had unfolded beautifully, Feinberg went to Spain with his wife and two children. It was supposed to be his first vacation in 20 years that wouldn’t get interrupted by the James Webb Space Telescope. “This was my big trip to go and finally relax,” Feinberg told me. Unfortunately, the universe doesn’t care if you’re out of the office.
That week, a particle of dust struck one of Webb’s mirrors. It was tiny, smaller than a grain of sand—less than a few tenths of a millimeter—but even tiny things travel at astounding speeds out in space.
Everyone on the Webb project knew something like this would happen to the telescope after it launched in December. Space is full of fast-moving bits of rock called “micrometeoroids,” which routinely and unavoidably smack into spacecraft in orbit. When astronauts brought home one of the Hubble Space Telescope’s cameras after 16 years in space, the once-unblemished hardware was covered with hundreds of little impact marks. Such cosmic bombardment degrades a space observatory’s performance over time, so, like other space hardware, Webb’s mirrors were designed to withstand meteorite strikes over many years. And the team predicted what kinds of impacts the telescope would experience. By the time Feinberg left for Spain, five months after Webb’s launch in December, four micrometeoroids had already hit the mirrors.
But this one, in May, was different—email-your-boss-on-vacation different. Feinberg, determined to unplug, had left his work phone at home in Maryland, but a colleague reached him on his personal email with the news: The latest impact was larger than any of their models had predicted. It had knocked one of the mirrors out of its pristine alignment and left behind a small dent in the glossy hardware. “Okaaay,” Feinberg said. Then he logged back on.
As in many non-space-related moments in life, even when you know something unpleasant might happen, you might still wince when it does. “Webb got launched like a beautiful new car, and after you go to the parking garage a few times, there’s going to be a few dings,” Marcia Rieke, an astronomer at the University of Arizona who leads one of Webb’s instrument teams, told me. (And though you might tell yourself it’s not a big deal … it still kind of is.) The “car,” in this case, is a $10 billion observatory meant to peer deeper into the universe than any other observatory in history has, and that orbits Earth four times farther away than the moon, too far for astronauts to make repairs. The engineers and scientists in charge of Webb have kept constant watch over their precious machine since it left Earth, especially as the observatory deployed itself, uncurling piece by piece. But in some sense, they’ve had to let the telescope go. Let it exist out there in the cold depths, where it will catch the faint light of the distant stars and galaxies, but also, occasionally, get dinged by roving specks of rock—including some larger than they ever expected.
Engineers are now working to readjust and fine-tune the affected mirror. They can’t completely cancel out the effects of the damage on future data, but they can minimize them. The telescope is still performing “well above expectations,” NASA said in a statement last week. The space agency is still on track to publicly release the mission’s first official images.
The question of how much cosmic bombardment Webb can withstand is now more open-ended than it once was, though. NASA has convened a special team of engineers to rework their predictions for the micrometeoroid environment and what that means for Webb’s mirrors. Feinberg, who is back at work, said that this and future impacts won’t meaningfully worsen Webb’s performance more than expected.
Engineers had prepared for this reality by conducting a series of tests on Earth, including throwing micrometeoroid-style projectiles at sample versions of the telescope’s mirrors. They couldn’t re-create the speed of an actual micrometeorite—a zoomy 20 to 30 kilometers, or 12 to 19 miles, a second—but they got as close as they could, testing at 7 kilometers, or 4 miles, per second, Feinberg said. The team fleshed out their models with data from other spacecraft that have resided where Webb does, in a special orbit known as L2, about 1 million miles away from Earth. And they came up with protocols for maneuvering the telescope to protect its mirrors from known meteor showers.
The first micrometeoroid strike—which occurred sometime before March, before the mirrors were fully aligned—was just one more reminder that this mission that scientists and engineers had worked on for more than 25 years on Earth was now, really and truly, where it belonged—“our ‘oh yeah, that’s right, we have a telescope that’s out in space’ moment,” as Jane Rigby, an astrophysicist at NASA and Webb’s project scientist for operations, put it to me. The next few hits lined up with the team’s expectations, occurring about once a month, Rigby said. They detected the impacts through the software that maintains and monitors the position of each mirror, making sure that the segments work in tandem. Then came the big one—the one that NASA said was “beyond what the team could have tested on the ground.”
The Webb team has already made one fix, smoothing out what Rigby described as some “bumpiness” in the affected mirror. Further adjustments will require unstacking the mirrors and then realigning them again, the process that was completed earlier in the spring, just before Feinberg went on vacation. Some of the damage is “correctable,” Rigby said. “Some of it we’re just going to have to live with.” Even with the new blemish, the mirrors are performing beautifully, she said. Webb was designed with a hefty budget for micrometeoroid impacts, and the latest strike “was a very small portion of our margin,” Feinberg said. “This won’t prevent us from doing amazing science consistently for a long period of time.”
NASA, ever the optimist, has found a way to spin the latest micrometeoroid damage into something positive. “Webb’s tremendous size and sensitivity make it a highly sensitive detector of micrometeorites,” a recent press release read. “Over time Webb will help improve knowledge of the solar system dust particle environment at L2, for this and future missions.” And sure, that could be a nice perk. But Webb wasn’t designed to study cosmic dust; it was meant to observe the primordial light that illuminated the cosmos just after the Big Bang, to help us answer very existential questions about how everything around us came to be. And mission managers must now take into account what the latest turn of events could mean for future observations. “How do we maximize the science return over the lifetime of the mission?” Rigby said. “Do we need to make any changes to our operations?”
As for the bigger-than-anticipated micrometeoroid impact, “we still don’t quite know what to make of it,” Rigby said. “Is this a really rare thing, and it’ll be a couple of years before we get another one this big?” They may never see another one like this again, Feinberg said, or they may encounter more. They need a few more months—and more encounters with micrometeoroids—to collect enough data to recalibrate their predictions. So far, four of Webb’s mirrors have been hit by these little bits and pieces of the solar system; one of those mirrors has been struck twice. Many years from now, all 18 of the mirrors might be covered in tiny craters, the marks of a well-worn space telescope that ably fulfilled its mission. The people who work on Webb are probably hoping that the universe eases up on those micrometeoroids just a bit. (And, if the tiny rocks have to ding the telescope, could they at least do it when the engineers aren’t on PTO?) “We are all going to cross our fingers that this one particular big one was just bad luck,” Rieke said.