NASA revealed(Opens in a new window) this week that the $10 billion James Webb Space Telescope was struck by micrometeoroids in late May, though engineers aren’t all that worried about it.
Micrometeoroids are usually fragments from comets, according to NASA(Opens in a new window); they’re small but travel at speeds of nearly 8,000 meters per second. That could leave quite the mark, but NASA says Webb was designed to survive(Opens in a new window) these types of collisions and is still operational following an “impact to one of its primary mirror segments.”
“After initial assessments, the team found the telescope is still performing at a level that exceeds all mission requirements despite a marginally detectable effect in the data,” says Thaddeus Cesari, a Strategic Communications Specialist at NASA’s Goddard Space Flight Center. “Thorough analysis and measurements are ongoing.”
As Cesari notes, “impacts will continue to occur throughout the entirety of Webb’s lifetime in space; such events were anticipated when building and testing the mirror on the ground.”
Prior to launch, the mirror in question underwent a series of computer simulations and lab-based tests to make sure it could withstand “dust-sized particles flying at extreme velocities,” Cesari says. Last month’s impact, however, was “larger than was modeled, and beyond what the team could have tested on the ground.”
This is actually Webb’s fifth micrometeoroid impact, though the previous four were much smaller. NASA says it put together a team of engineers who will study how to mitigate the effects of large micrometeoroid hits.
“We always knew that Webb would have to weather the space environment,” says Paul Geithner, technical deputy project manager at Goddard. “We designed and built Webb with performance margin—optical, thermal, electrical, mechanical—to ensure it can perform its ambitious science mission even after many years in space.”
All sensitive components on Webb feature “micrometeoroid armor,” Geithner says. “When micrometeoroids do strike, most are so small that they totally disintegrate upon impact, even when they hit something thin like thermal blankets or a sunshield membrane. Critical wires and electronics are shielded behind even more robust metal ‘armor’ or inside metal boxes.”
Flight teams can prepare for strikes by moving Webb’s optics; they can also adjust mirror positions to make “partial corrections” after an impact. “This most recent hit…is currently considered an unavoidable chance event,” Cesari says.
The world’s largest and most complex space science observatory—named after former NASA Administrator James E. Webb—took off on Dec. 25, 2021 and reached orbit a month later. In March, it produced its first unified image of a distant star, using all 18 mirrors across the craft. Its first full-color images and spectroscopic data are expected by July 12.