The Webb Telescope Has Been Hit By Something. Here’s What It Means For Science

NASA’s James Webb Space Telescope (JWST) has been hit by a micrometeoroid, which has damaged one of the 18 beryllium-gold segments that makes up its main 6.5-meter mirror.

It happened between May 23 and 25 according to NASA with the result being a “marginally detectable effect in the data.” Its C3 segment is thought to have been impacted by small dust particles.

Is it serious? It appears not—despite the impact knocking the telescope slightly out of alignment. Webb “recently sustained an impact to one primary mirror segment,” said Thomas Zurbuchen, Associate Administrator at NASA’s Science Mission Directorate, in a tweet† “After initial assessments, the team found the telescope is still performing at a level that exceeds all mission requirements.”

He added that micrometeoroid strikes are an unavoidable aspect of operating in space.

Webb—a $10 billion space telescope that sees in the infrared part of the spectrum—launched on Christmas Day in 2021 and has since February been orbiting the L2 point about a million miles/1.6 million kilometers from Earth. Its “first light” images are due to be published on July 12. They’re expected to be a dazzling demonstration of just what the world’s most advanced space observatory ever is capable of.

Analysis and measurements are ongoing, said NASA, but it doesn’t look like those initial images—or the science program that will follow—will be greatly affected. That’s because engineers have been able to adjust its 18 mirrors to correct for the damaged segment.

“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,” said Paul Geithner, technical deputy project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We designed and built Webb with performance margin—optical, thermal, electrical, mechanical—to ensure it can perform its ambitious science mission even after many years in space.”

That includes dust-sized particles flying at extreme velocities, though this impact was larger than was modeled when Webb was being built, NASA said. However, it added that Webb’s initial performance is still well above expectations.

It’s not the first time Webb has been struck. “Since launch, we have had four smaller measurable micrometeoroid strikes that were consistent with expectations and this one more recently that is larger than our degradation predictions assumed,” said Lee Feinberg, Webb optical telescope element manager at NASA Goddard. “We will use this flight data to update our analysis of performance over time and also develop operational approaches to assure we maximize the imaging performance of Webb to the best extent possible for many years to come.”

Although the recent impact is classed as an “unavoidable chance event” Webb’s engineers are able to maneuver it to protect the optics from known meteor showers.

Wishing you clear skis and wide eyes.

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