Webb telescope struck by bigger-than-expected micrometeroid
Artist’s concept of the Webb space telescope. It launched in December 2021. In June 2022, NASA announced that a larger-than-expected micrometeoroid strike has scarred a segment of the telescope’s primary mirror. So far, it appears that the telescope will continue to function as expected. That’s a relief because a fix would have been tough; the telescope orbits at the L-2 point, which is four times the moon’s distance from Earth. Image via Northrop Grumman/ Canadian Space Agency.
Webb in micrometeoroid strike
NASA announced on Wednesday, June 8, 2022, that a micrometeoroid strike in late May 2022 scarred one of the major mirror segments of the James Webb Space Telescope — Hubble’s successor. Micrometeroids were expected to strike Webb’s operators. But the power of this particular strike – the 5th recorded since the instrument launched – was greater than its operators had anticipated. NASA engineers have stated that the instrument will need to be adjusted to compensate for the unanticipated early damage. Meanwhile, NASA reported in a blog post:
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. Thorough analysis and measurements are ongoing.
Is it planned to replace the mirror segment? No, and there most likely will not be. The damage doesn’t appear to be great enough for such a drastic step. And the telescope is orbiting the Earth-sun system at the L-2 point, which is a million miles (1.6 million km) away from Earth.
Micrometeoroid impacts expected
The title of NASA’s June 8 blog post, announcing the micrometeoroid strike, is Webb: Engineered to Endure Micrometeoroid Impacts. According to the report, Lee Feinberg, Webb optical telescope element manager at NASA Goddard, said:
With Webb’s mirrors exposed to space, we expected that occasional micrometeoroid impacts would gracefully degrade telescope performance over time. Since launch, we have had four smaller measurable micrometeoroid strikes that were consistent with expectations, and this one more recently that is larger than our degradation predictions assumed.
We will use this flight data to update our analysis of performance over time and also develop operational approaches to assure we maximize the imaging performance of Webb to the best extent possible for many years to come.
The current strike, according to Webb’s operators, took place between May 23 and May 25.
Designed to be tough
Engineers designed the Webb telescope to be tough. Indeed, it underwent complete testing to mimic the conditions it will face beyond Earth’s moon’s orbit. According to NASA, Webb is designed to withstand a lifetime of damage while remaining operational. According to NASA’s blog post, Paul Geithner, technical deputy project manager at NASA’s Goddard Space Flight Center, “
We always knew that Webb would have to weather the space environment, which includes harsh ultraviolet light and charged particles from the sun, cosmic rays from exotic sources in the galaxy, and occasional strikes by micrometeoroids within our solar system. 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.
Compensating for micrometeoroid strike
Since the engineers anticipated damage of this type to Webb, ground-based controllers are able to somewhat compensate. They can achieve this by relocating the mirror segment, for example. NASA said:
Engineers have already performed a first such adjustment for the recently affected segment C3, and additional planned mirror adjustments will continue to fine tune this correction. These steps will be repeated when needed in response to future events as part of the monitoring and maintenance of the telescope throughout the mission.
1st Webb science results to be released July 12
The current period is a stressful one for those operating the Webb. The instrument is currently undergoing six months of preparation before primary data collection can begin. On July 12, 2022, the first full-color photographs from the telescope will be revealed.
Significantly, that day should mark the beginning of a new era in our understanding of the cosmos around us. According to Eric Smith, Webb program scientist at NASA Headquarters in Washington,
As we near the end of preparing the observatory for science, we are on the precipice of an incredibly exciting period of discovery about our universe. The release of Webb’s first full-color images will offer a unique moment for us all to stop and marvel at a view humanity has never seen before.
These images will be the culmination of decades of dedication, talent, and dreams – but they will also be just the beginning.
Technicians prepare the Webb telescope for launch back in December 2021. Under the ring in the floor sits the Ariane 5 rocket that blasted it to space for its journey to L2. The 2nd Lagrangian point in space is where gravitational forces and a body’s orbital motion balance each other in the Earth-sun system. At L2, an object may “hover” relatively effortlessly. However, L2 is a long way away, over 1 million miles (1.5 million km) behind Earth as seen from the sun. That’s around four times the distance between the Earth and the Moon. ESA provided the image.
Bottom line: A micrometeoroid strike slightly damaged one of the segments of the Webb telescope’s primary mirror. Thankfully, the instrument is still performing beyond mission parameters. Its first full-color images will be released July 12, 2022.