Scorpius the Allfather said

So it supposedly suffered significant uncorrectable damage and yet "Despite this, Webb’s team has determined the overall impact on the telescope is small. Engineers were able to realign Webb’s segments to adjust for the micrometeoroid’s damage." So how significant was it?

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A micrometeoroid struck the James Webb Space Telescope between May 22 and 24, impacting one of the observatory's 18 hexagonal golden mirrors. NASA had disclosed the micrometeoroid strike in June and noted that the debris was more sizeable than pre-launch modeling had accounted for. Now, scientists on the mission have shared an image that drives home the severity of the blow in a report(opens in new tab) released July 12 describing what scientists on the mission learned about using the observatory during its first six months in space.

Happily, in this case the overall effect on Webb was small. That said, the report outlines the investigation and modeling that engineers are undertaking to assess the long-term effects of micrometeroids on Webb.

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Alternatively, it may be that Webb is "more susceptible to damage by micrometeoroids than pre-launch modeling predicted," the team wrote. Modeling is ongoing to estimate the hazardous population of micrometeoroids and to figure out remedies, such as restricting pointing direction.

One remedy could be minimizing the amount of time Webb points directly into its orbital direction, "which statistically has higher micrometeoroid rates and energies," the team wrote.

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Main mirror performance is assessed by how much it deforms starlight, according to Astronomy magazine(opens in new tab), and measured using what scientists call wavefront error root mean square. When Webb's mission began, the affected C3 segment had a wavefront error of 56 nanometers rms (root mean square), which was in line with the 17 other mirror portions.

Post-impact, however, the error increased to 258 nm rms, but realignments to the mirror segments as a whole reduced the overall impact to just 59 nm rms. For the time being, the team wrote Webb's alignment is well within performance limits, as the realigned mirror segments are "about 5-10 nm rms above the previous best wavefront error rms values."

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