How can micrometeorites damage James Webb?

The Webb’s mirror was designed to withstand the intense bombardment of dust-sized particles flying at extreme speeds in the environment of micrometeorites in its L2 Sun-Earth orbit.

A segment of the 6.5-meter primary mirror of the James Webb Space Telescope suffered a fortuitous and larger-than-expected impact from a micrometeorite 1.5 million kilometers from Earth. The impact occurred between May 23 and May 25. Early evaluations indicate that the telescope’s performance far exceeds mission requirements, despite a marginally detectable effect on the data. Extensive testing and measurements are ongoing. During long and productive missions in space, any spacecraft will experience numerous micrometeorite impacts. This is an unavoidable aspect of space operations.

A durable mirror

The Webb Mirror was designed to withstand the intense bombardment of dust-sized particles (micrometeorites) flying at extreme speeds in the micrometeorite environment in its L2 Sun-Earth orbit. To better understand how to harden the observatory to operate in orbit, engineers combined simulations and real-world impact tests on sample mirrors. According to NASA, the final impact was much larger than the team could have modeled and tested on the ground. According to Paul Geithner, deputy technical director for projects at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, Webb encountered strong ultraviolet light and charged particles from the Sun,

Performance margins

“In order for Webb to be able to accomplish its ambitious scientific mission even after many years in space, experts have designed and built it with performance margins (optical, thermal, electrical, mechanical). Webb’s optics were kept cleaner than necessary on the ground thanks to the hard work of the launch site crews; this improves reflectivity and performance, and therefore overall sensitivity. Through this and other margins, Webb’s scientific abilities are resilient to the degradation of his scientific abilities over time. In addition, Webb’s ability to sense the position of mirrors and adjust them allows him to partially correct impact results. It is possible to undo some of the distortion by adjusting the position of the affected segment.

Adjustment of mirrors

By doing so, any impact is minimized, but not all degradation is neutralized. This adjustment, the first of its kind, has already been made to repair the recently affected segment of C3, and further mirror adjustments are planned. In response to future events, these steps will be repeated as necessary as part of telescope monitoring and maintenance. A protection maneuver can be used to protect Webb while he is in orbit. In this maneuver, the flight team intentionally moves the optics away from known meteor showers before they occur. Since the most recent impact had nothing to do with a meteor shower, it is now considered an unavoidable chance event.

Mitigate future impacts

In response to this impact, a team of engineers was formed to find ways to mitigate future impacts caused by micrometeorite fragments. As the telescope’s initial performance was better than expected, the team will collect valuable data over time and work with micrometeorite forecasting experts at NASA’s Marshall Space Flight Center to make better predictions about future performance. . . Webb’s extraordinary size and sensitivity make it a very sensitive micrometeorite detector; Eventually, Webb will provide insight into the dust particle environment of L2 for future missions as well.

Webb’s operations schedule was unaffected by the recent impact, with the team continuing to review instrument observing modes and prepare for the launch of new Webb images and science operations.