The James Webb Space Telescope, which began its operations last week, has suffered considerable damage to its primary mirror due to a micrometeoroid impact. This was revealed in a report released by the mission teams after NASA released the first 'deepest images of the universe' on July 12. The document is a characterisation of Webb's performance from the commissioning phase which began one month after its launch on December 25. 

How damaged is the Webb telescope?

In the document released last week, the engineers reported a total of six micrometeoroid strikes, five of which did minimal damage to Webb's primary mirror. The telescope has a primary mirror which is composed of 18 small hexagonal segments plated with gold and beryllium. While Webb was able to absorb the first five strikes, the sixth one "which hit segment C3 in the period 22—24 May 2022 UT caused significant uncorrectable change in the overall figure of that segment", the engineers wrote in their report. 

However, the report highlighted that the said six strikes sustained by Webb were recorded by wavefront sensing as opposed to the NIRCam pupil imaging, which can detect impacts below the threshold detectable by wavefront sensing. NIRCam is short for the Near-Infrared Camera, one of Webb's four instruments, and according to the mission team, it detected a total of 19 minor impacts between February 23 and May 26.

How did the impacts affect Webb's performance?

These strikes, however, have failed to harm Webb's performance as the telescope is exceeding expectations in terms of its performance. What's more, is that the telescope might end up lasting a decade more than the previously estimated lifespan of ten years at the most. 

For a spacecraft in outer space, getting bombarded with these micrometeorites is inevitable, be it the International Space Station (ISS). Considering Webb's location at the second Lagrange Point, which is 1.5 lakh kilometres from Earth, threats from small space rocks are amplified. The NASA team further admitted that the constant impacts would certainly take a toll on the primary mirror. "At present, the largest source of uncertainty is long term effects of micrometeoroid impacts that slowly degrade the primary mirror", the document further read.