A micrometeoroid that hit the Webb Space Tthe telescope in late May caused permanent damage to the spacecraft, according to a Report of the Space Telescope Science Institute.
The report was released last week by NASA and the European and Canadian space agencies. It described the scientific performance of the telescope until July 12, 2022, the day when first images from the telescope were made public and included an exciting first look of the planet Jupiter as seen by Webb.
According to analysis, the impact “exceeded pre-launch damage expectations for a single micrometeoroid”. The Webb team is currently investigating how to predict and mitigate future impacts.
Micrometeoroids are pieces of rockk flying in space. In orbit Earth, these rocks can reach spee from up to 22,000 miles per hour and are a regular hazard to astronauts, satellites and spacecraft.
At the beginning of Junea NASA statement said a micrometeoroid had hit one of the hexagonal mirrors of the Webb telescope between May 23 and May 25; the new report estimates that the impact actually happened between May 22 and May 24.
“We always knew 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 strikes in our solar system,” said said Paul Geithner, technical assistant project manager at NASA’s Goddard Space Flight Center, in June Release.
The Webb telescope mirrors were meticulously aligned to produce high resolution images of very faint light sources in the distant universe. The recent report compared ground-based measurements of the optical quality of the mirror segments to the current quality of the telescope; they found a significant error in segment C3.
Because the C3 segment is just one of 18 hexagonal mirrors that make up the telescope’s main mirror, damage from micrometeoroids is relatively small at the full telescope, the report says.
Despite the damage, the team’s initial assessment indicates that Webb “should meet its optical performance requirements for many years to come.” With the precise launch of the telescope, it is expected to be operational for 20 years and will spend its entire tenure at L2, a point in space approximately millions of miles from Earth.
The big unknown, the team said, is the rate of mirror degradation by micrometeoroids; in other words, how many more harmful space particles than expected will hit the $10 billion observatory. At the time of the June statement on the May impact event, the team detected four micrometeoroid strikes that matched their expectations for such events, but the larger event is cause for concern. If Webb is more susceptible to micrometeoroid impacts than scientists predictedits mirrors will degrade sooner than expected.
It is possible that the team hijack Webb’s optics micrometeoroid strikes to protect his mirrors down the line, but for that to happen, strikes must be anticipated. Webb was severely delayed here on Earth, but for an observatory that launched and commissioned without issue, it was only a matter of time before space threw a snowball at Webb’s scientists.
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