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See how a new $10 billion telescope will come to life in space
01:57 - Source: CNN

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One of the 18 golden segments of the James Webb Space Telescope’s giant mirror was hit by a micrometeoroid in May, according to an update from NASA. But don’t worry – the space observatory is still on track to share its first high-resolution, full-color images on July 12.

A micrometeoroid is a particle in space that is smaller than a grain of sand. Earth’s atmosphere is hit by millions of meteoroids and micrometeoroids on a regular basis, but most are vaporized when they hit the atmosphere, according to NASA.

But spacecraft don’t have a protective bubble of atmosphere around them, so it’s almost impossible to avoid these impacts.

The Webb telescope sustained such an impact between May 23 and 25, but “the telescope is still performing at a level that exceeds all mission requirements despite a marginally detectable effect in the data,” according to the Webb team.

The team is continuing to analyze and assess what happened and how it may affect the telescope’s performance. It’s also likely the first of many such experiences that Webb will have over its time in space.

Preparing for impact

When the telescope and its massive mirror were being built and tested on Earth, engineers made sure that the mirror could survive the micrometeoroid environment the spacecraft would experience in its orbit about a million miles from Earth at a point called L2, where dust particles are accelerated to extreme velocities.

Webb was put through its paces while on Earth, and the team used both simulations and test impacts on mirror samples to understand what it would face.

The May impact event was larger than anything the team tested or would have been able to model while Webb was still on the ground.

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NASA/JPL-Caltech; NASA/ESA/CSA/STScI

Webb telescope's sharp views of the universe will change astronomy

“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,” said Paul Geithner, technical deputy project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in a statement.

“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.”

Fortunately, each hexagonal mirror segment is fully adjustable, and the impacted segment has already been adjusted to lessen some of the distortion. This is something engineers can continue to do in the future as they monitor Webb’s mirror for any signs of degradation in the space environment.

Webb’s flight team already turns the spacecraft’s mirror away from known events, like meteor showers, to protect the telescope’s optics. But this impact, which wasn’t part of a meteor shower, was unforeseen and “an unavoidable chance event,” according to NASA.

“As a result of this impact, a specialized team of engineers has been formed to look at ways to mitigate the effects of further micrometeoroid hits of this scale,” according to a release from the agency.

Looking ahead

The Webb team will work closely with micrometeoroid prediction experts at NASA’s Marshall Space Flight Center in Huntsville, Alabama. And Webb will be able to help NASA scientists learn more about the dust environment of the solar system at this orbit point, which can assist with preparing for future missions.

Engineering images of sharply focused stars in the field of view of each instrument demonstrate that the telescope is fully aligned and in focus. For this test, Webb pointed at part of the Large Magellanic Cloud, a small satellite galaxy of the Milky Way, providing a dense field of hundreds of thousands of stars across all the observatory's sensors. The sizes and positions of the images shown here depict the relative arrangement of each of Webb's instruments in the telescope's focal plane, each pointing at a slightly offset part of the sky relative to one another. Webb's three imaging instruments are NIRCam (images shown here at a wavelength of 2 microns), NIRISS (image shown here at 1.5 microns), and MIRI (shown at 7.7 microns, a longer wavelength revealing emission from interstellar clouds as well as starlight). NIRSpec is a spectrograph rather than imager but can take images, such as the 1.1 micron image shown here, for calibrations and target acquisition. The dark regions visible in parts of the NIRSpec data are due to structures of its microshutter array, which has several hundred thousand controllable shutters that can be opened or shut to select which light is sent into the spectrograph. Lastly, Webb's Fine Guidance Sensor tracks guide stars to point the observatory accurately and precisely; its two sensors are not generally used for scientific imaging but can take calibration images such as those shown here. This image data is used not just to assess image sharpness but also to precisely measure and calibrate subtle image distortions and alignments between sensors as part of Webb's overall instrument calibration process.
Engineering images of sharply focused stars in the field of view of each instrument demonstrate that the telescope is fully aligned and in focus. For this test, Webb pointed at part of the Large Magellanic Cloud, a small satellite galaxy of the Milky Way, providing a dense field of hundreds of thousands of stars across all the observatory's sensors. The sizes and positions of the images shown here depict the relative arrangement of each of Webb's instruments in the telescope's focal plane, each pointing at a slightly offset part of the sky relative to one another. Webb's three imaging instruments are NIRCam (images shown here at a wavelength of 2 microns), NIRISS (image shown here at 1.5 microns), and MIRI (shown at 7.7 microns, a longer wavelength revealing emission from interstellar clouds as well as starlight). NIRSpec is a spectrograph rather than imager but can take images, such as the 1.1 micron image shown here, for calibrations and target acquisition. The dark regions visible in parts of the NIRSpec data are due to structures of its microshutter array, which has several hundred thousand controllable shutters that can be opened or shut to select which light is sent into the spectrograph. Lastly, Webb's Fine Guidance Sensor tracks guide stars to point the observatory accurately and precisely; its two sensors are not generally used for scientific imaging but can take calibration images such as those shown here. This image data is used not just to assess image sharpness but also to precisely measure and calibrate subtle image distortions and alignments between sensors as part of Webb's overall instrument calibration process.
NASA/STScI

The James Webb Space Telescope is fully aligned and ready to observe the universe

“With Webb’s mirrors exposed to space, we expected that occasional micrometeoroid impacts would gracefully degrade telescope performance over time,” said Lee Feinberg, Webb optical telescope element manager at NASA Goddard, in a statement.

“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.”

Webb has already exceeded expectations since launching in December, and the telescope is preparing for the beginning of science operations.

Webb will be able to peer inside the atmospheres of exoplanets and observe some of the first galaxies created after the universe began by observing them through infrared light, which is invisible to the human eye.