NASA’s new powerful space observatory, the James Webb Space Telescope, got pelted by a larger than expected micrometeoroid at the end of May, causing some detectable damage to one of the spacecraft’s 18 primary mirror segments. The impact means that the mission team will have to correct for the distortion created by the strike, but NASA says that the telescope is “still performing at a level that exceeds all mission requirements.”
NASA’s James Webb Space Telescope, or JWST, is the agency’s incredibly powerful next-generation space telescope, designed to look into the farthest reaches of the Universe and see back in time to the stars and galaxies that formed just after the Big Bang. It cost NASA nearly $10 billion to build and more than two decades to complete. But, on Christmas Day 2021, the telescope finally launched to space, where it underwent an extremely complex unfolding process before reaching its final destination roughly 1 million miles from Earth.
Since its launch, JWST has already been hit by at least four different micrometeoroids, according to a NASA blog post, but all of those were small and about the size of what NASA expected the observatory to encounter. A micrometeoroid is typically a small fragment of an asteroid, usually smaller than a grain of sand. The one that hit JWST in May, however, was larger than what the agency had prepared for, “likely less than .1 millimeter,” a NASA spokesperson told The Verge in an email. NASA admits that the strike, which occurred between May 23rd and May 25th, caused a dimple in the mirror and a “marginally detectable effect in the data,” which engineers are continuing to analyze.
NASA expected JWST to get hit by tiny space particles during its lifetime; fast-moving specks of space rock are just an inescapable feature of the deep space environment. In fact, NASA designed the telescope’s gold-coated mirrors to withstand strikes by tiny space debris over time. The space agency also did a combination of simulations and ground testing with mirror samples to determine how to best strengthen the mirrors to withstand micrometeoroid impacts. However, NASA says that the models they used for these simulations didn’t have a micrometeoroid this large, and it was “beyond what the team could have tested on the ground.”
Still, this doesn’t come as a total surprise. “We always knew that Webb would have to weather the space environment, which includes harsh ultraviolet light and charged particles from the Sun, cosmic rays from exotic sources in the galaxy, and occasional strikes by micrometeoroids within our solar system,” Paul Geithner, technical deputy project manager at NASA’s Goddard Space Flight Center, said in a statement.
Engineers do have the capability to also maneuver JWST’s mirror and instruments away from showers of space debris, if NASA can see them coming. The problem, though, was that this micrometeoroid was not part of a shower, so NASA considers it an “unavoidable chance event.” Still, the agency is forming an engineering team to come up with ways to potentially avoid or lessen the effects of micrometeoroid strikes of this size. And since JWST is so sensitive, the telescope will also help NASA get a better understanding of just how many micrometeoroids there are in the deep space environment.
Despite the strike, NASA remained optimistic in its post about JWST’s future. “Webb’s beginning-of-life performance is still well above expectations, and the observatory is fully capable of performing the science it was designed to achieve,” according to the blog. Engineers can also adjust the impacted mirror to help cancel out the data distortion. The mission team has done this already and will continue to tinker with the mirror over time to get the best results. It’s a process that will be ongoing throughout JWST’s planned five to 10 years of life as new observations are made and events unfold. At the same time, NASA warns that the engineers will not be able to completely cancel out the impact of the strike.
NASA engineers had to build JWST to be incredibly robust since the telescope is on its own out in space. Unlike its predecessor, the Hubble Space Telescope, which is currently in orbit around Earth, JWST was not designed to be serviceable. That means if something significant breaks on the spacecraft, engineers will have to troubleshoot a way to fix it from the ground. There’s no capability at the moment to send humans or a robotic spacecraft to give JWST a tune-up. That means JWST will have to live with its slightly damaged mirror until the end of its mission, and NASA expects the spacecraft to get hit by even more debris over time.
In the meantime, the strike doesn’t appear to be impacting JWST’s schedule. In fact, the news of this micrometeoroid comes just a month before a huge milestone for the mission. After spending the last few months finely calibrating JWST’s instruments and delicately aligning the spacecraft’s mirrors, the mission team is set to unveil the first full-color images from JWST on July 12th. NASA won’t say what the images will be, but they should be spectacular.
Update June 9th, 4PM ET: This post was updated to include additional information from NASA about the size of the impact.