The James Webb Space Telescope barely had a chance to get to work, and it once whisked a micrometeoroid to its sensitive primary mirror.
The NASA-built space observatory reached its final destination, L2 orbit, a million miles from Earth, in late January.
In a statement, NASA said the impact occurred in late May. Although the impact is greater than anything NASA has modeled and “beyond what the team could have tested in the field”, the space agency said the telescope continues to operate at levels higher than expected. The telescope has been hit four times since launch.
James Webb’s main mirrors make up the golden array that takes up much of the telescope’s body. These 18 gold-plated mirrors are carefully aligned at the nanometer scale to reflect infrared light back to James Webb’s cameras, a process that took scientists months to complete from ground control.
The C3 mirror, which took the hit, will need to be adjusted to counter distortion and noise resulting from impact.
“Engineers have already made a first such adjustment for the recently affected C3 segment, and planned additional mirror adjustments will continue to refine this correction,” NASA said. Micrometeoroid impacts like this are “considered an unavoidable chance event,” the agency said.
Micrometeoroids are small – often less than a millimeter – but they move so quickly relative to spacecraft orbiting Earth that they can cause craters visible to the naked eye. Space debris of this size has a typical impact velocity of 10 km/s (22,369 mph), while meteoroids, generally considered larger than a grain of rice, strike at double the velocity.
Spacecraft like James Webb are designed to withstand these types of impacts, but there are limits to what can be done to minimize them above a certain scale, especially when it comes to rocks traveling 6 to 12 miles per second. Herein likes the bright spot for NASA scientists, who are used to dealing with mission-altering issues.
“Because of this impact, a team of specialist engineers was formed to research ways to mitigate the effects of further micrometeoroid impacts of this magnitude,” NASA said.
In addition to protecting James Webb, NASA wants to use the telescope to better understand the dust and micrometeoroids lashing the solar system, particularly at point L2 where the telescope is located. L2 is considered a “sweet spot” for galactic observation, and other space agencies plan to deploy missions to the same area.
To those concerned that this impact will delay or hinder Webb’s work — and to those eagerly awaiting the first images slated for release in July — NASA said the schedule is still on schedule. ®