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Journalism of Courage
The James Webb Space Telescope has already been struck by many micrometeoroids since its launch in December 2021 and continues to function without any major impediments. While the space telescope was engineered to withstand bombardment from these dust-sized particles, Webb teams have developed a plan to minimise future impacts.
It hasn’t yet been a year since Webb was launched but since then, its golden primary mirror has been hit by 14 measurable micrometeoroids, averaging about one to two per month. The optical errors resulting from all but one impact were within what Webb teams had expected and “budgeted” for.
One of the impacts was higher than expectations and prelaunch models but even after that, the optical performance of the telescope is twice as good as requirements, according to Mike Menzel, NASA’s Webb lead mission systems engineer.
After the high-energy impact observed in May, NASA convened a working group of expert’s from the agency’s Webb team, the manufacturer of the telescope’s mirror, the Space Telescope Science Institute, and the NASA Meteoroid Environment office. The team analysed this impact and concluded that it was a rare statistical event with the micrometeoroid having a high impact energy and hitting a particularly sensitive location on the mirror.
Nonetheless, the team decide that future observations should be planned to face away from what is known as the ‘micrometeoroid avoidance zone’ to minimise future impacts of that magnitude.
“Micrometeoroids that strike the mirror head-on (moving opposite the direction the telescope is moving) have twice the relative velocity and four times the kinetic energy, so avoiding this direction when feasible will help extend the exquisite optical performance for decades,” said Lee Feinberg, Webb optical telescope element manager, in a NASA statement.
But according to Feinberg, this does not mean that Webb will be unable to observe some parts of the sky. Instead, observations of certain objects will be made more safely at a different time of the year when Webb is at a different location in its orbit. Some observations will still be done in the micrometeoroid zone if they are time critical.
This new micrometeoroid avoidance zone will be implemented during Webb’s second year of science, which is dubbed “Cycle 2.”
