The James Webb Space Telescope (JWST) is an international space observatory for the twenty-first century that was launched on December 25, 2021. It is envisioned as the premier observatory of the 2020s, combining the largest mirror ever used on a near-infrared space telescope with a suite of technologically advanced instruments from around the world.
Micrometeoroid strikes are an unavoidable aspect of spacecraft operation. NASA’s James Webb Space Telescope was designed to withstand constant bombardment from these dust-sized particles moving at high speeds in order to continue producing groundbreaking science far into the future.
“We’ve had 14 measurable micrometeoroid hits on our primary mirror, averaging one or two per month, as expected. All but one of these caused optical errors that were well within our budget and expectations when we built the observatory” Webb lead mission systems engineer Mike Menzel at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “One of these was higher than our expectations and prelaunch models; however, our current optical performance is still twice as good as our requirements even after this event.”
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.
Lee Feinberg
To ensure all parts of the observatory continue to perform at their best, NASA convened a working group of optics and micrometeoroid experts from NASA Goddard’s Webb team, the telescope’s mirror manufacturer, the Space Telescope Science Institute, and the NASA Meteoroid Environment Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
After thorough analysis, the team concluded the higher-energy impact observed in May was a rare statistical event both in terms of energy and in hitting a particularly sensitive location on Webb’s primary mirror. To minimize future impacts of this magnitude, the team has decided that future observations will be planned to face away from what is now known as the “micrometeoroid avoidance zone.”
“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 at NASA Goddard.
This does not mean that these areas of the sky cannot be observed, only that observations of those objects will be more safely made at a different time in the year when Webb is in a different location in its orbit. Observations that are time critical, such as solar system targets, will still be done in the micrometeoroid avoidance zone if required. This adjustment to how Webb observations are scheduled will have a long-term statistical benefit.
The team will implement the micrometeoroid avoidance zone starting with Webb’s second year of science, or “Cycle 2.” More information and guidance for Cycle 2 is available on JWST Observer News.
