NASA’s powerful new space telescope is hit by a larger-than-expected micrometeoroid

NASA’s powerful new space observatory, the James Webb Space Telescope, was hit by a larger-than-expected micrometeoroid in late May, causing some detectable damage to one of the spacecraft’s 18 primary mirror segments. The impact means the mission team will have to correct the distortion created by the attack, but NASA says the telescope “is still operating 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 peer into the far reaches of the Universe and look back in time to the stars and galaxies that formed shortly after the Big Bang. It cost NASA nearly $10 billion to build and over two decades to complete. But on Christmas Day 2021, the telescope was finally launched into space, where it underwent an extremely complex unfolding process before reaching its final destination some 1 million kilometers from Earth.

Since its launch, JWST has been hit by at least four different micrometeoroids, according to a NASA blog post, but all were small and about the size of what NASA expected the observatory to find. A micrometeoroid is typically a small fragment of an asteroid, usually smaller than a grain of sand. What hit JWST in May, however, was larger than what the agency had prepared, though the agency did not specify its exact size. NASA admits that the attack, which took place between May 23 and 25, had a “marginally detectable effect on the data” and that engineers are continuing to analyze the effects of the impact.

NASA expected the JWST to be hit by tiny space particles during its lifetime; fast-moving space rock particles are just one inescapable feature of the deep space environment. In fact, NASA designed the telescope’s gold-coated mirrors to resist impacts from small space debris over time. The space agency also did a combination of simulations and ground tests with mirror samples to determine how best to strengthen the mirrors to withstand micrometeoroid impacts. However, NASA says the models they used for these simulations did not have such a large micrometeoroid and were “beyond what the team could have tested on the ground”.

Still, this isn’t a total surprise. “We always knew that Webb would have to contend with the space environment, which includes harsh ultraviolet light and charged particles from the Sun, cosmic rays from exotic sources in the galaxy, and occasional micrometeoroid attacks within our solar system,” Paul Geithner, deputy technical manager of NASA’s Goddard Space Flight Center project, in a statement.

JWST’s primary mirror under test on Earth
Image: NASA

Engineers also have the ability to maneuver the JWST’s mirror and instruments away from showers of space debris, if NASA can see them coming. The problem, however, was that this micrometeoroid was not part of a shower, so NASA considers it an “inevitable chance event”. Still, the agency is forming an engineering team to find ways to potentially prevent or lessen the effects of attacks by micrometeoroids of this size. And because the JWST is so sensitive, the telescope will also help NASA better understand how many micrometeoroids exist in the deep space environment.

Despite the strike, NASA remained optimistic in its post about the future of the JWST. “Webb’s early-life performance is still well above expectations, and the observatory is fully capable of performing the science it was designed for,” according to the blog. Engineers can also adjust the affected mirror to help cancel out data skew. The mission team has already done this and will continue to fiddle with the mirror over time for the best results. It is a process that will be ongoing over the JWST’s planned five to 10 years of life, as new observations are made and events unfold. At the same time, NASA warns that engineers will not be able to completely cancel the impact of the attack.

NASA engineers had to build the JWST to be incredibly robust, as the telescope is alone in space. Unlike its predecessor, the Hubble Space Telescope, which is currently in orbit around Earth, the JWST is not designed to be serviceable. This means that if something significant breaks on the spacecraft, engineers will have to figure out a way to fix it from the ground. There is currently no capability to send humans or a robotic spacecraft to adjust the JWST. That means the JWST will have to live with its mirror slightly damaged until the end of its mission, and NASA expects the spacecraft to be hit by even more debris over time.

Meanwhile, the strike doesn’t appear to be affecting JWST’s schedule. In fact, news of this micrometeoroid comes just a month before a major milestone for the mission. After spending the past few months calibrating the JWST’s instruments and delicately aligning the spacecraft’s mirrors, the mission team is expected to reveal the first color images of the JWST on July 12. NASA won’t say what the images will be, but they should be spectacular.

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