Nasa’s James Webb Space Telescope damaged after being crushed by space rocks, images show

Nasa’s James Webb Space Telescope damaged after being crushed by space rocks, images show

Damage to the main mirror of the James Webb Telescope from a micrometeorite strike in May is worse than expected, according to new images revealed in a new report.

A paper published Tuesday on the academic preprint server arxiv.org detailing Webb’s performance during telescope commissioning found that most micrometeorite impacts on Webb’s Large Mirror resulted in negligible damage, but an impact occurred in mid-May even left the telescope. with permanent damage.

“The single micrometeoroid impact that occurred between May 22-24, 2022 UT exceeded pre-launch damage expectations for a single micrometeoroid triggering further investigation and modeling by the JWST project,” the report said. report.

Unlike the Hubble Space Telescope, which houses the main mirror the telescope uses to collect light and focus light on scientific instruments in a cylindrical case, Webb’s 6.5-meter-diameter segmented mirror is exposed to space. . But given Webb’s orbit around Lagrangian Point 2, or L2, a region of space about 1 million miles from Earth, scientists expected Webb to encounter potentially dangerous micrometeorites about once. per month.

During the commissioning period from late January to June, while ground controllers were calibrating, aligning and testing Webb’s mirrors and instruments, the main mirror suffered a total of six micrometeorite impacts.

Of those strikes, five caused little damage, causing less than 1 nanometer root mean square of wavefront error (RMS), a technical way of describing how much Webb’s mirror distorts starlight that the mirror collects. Most of the distortion added by these five keystrokes can be corrected out of the mirror, since the 18 hexagonal segments that make up its face can be individually and finely adjusted.

But the sixth strike, which hit a mirror segment labeled C3, did more damage that can be fully remedied. This micrometeorite strike increased the wavefront error of the segment from 56 nanometers to 178 nanometers after correction by adjusting the segment.

However, because each mirror segment is adjustable, damage to the C3 segment could be compensated for and did not compromise the resolution of Webb’s main mirror as a whole, according to the report. The total wavefront error for the whole mirror has increased by about 9 nanometers due to the striking.

“It is not yet clear whether the May 2022 hit on the C3 segment was a rare event (i.e. an unlucky early hit by a high kinetic energy micrometeoroid that statistically could not occur only once in several years),” the report states, “or whether the telescope might be more susceptible to damage from micrometeoroids than pre-launch modeling predicted.

The report goes on to note that the Webb Project team is considering actions to mitigate future micrometeorite impacts, such as limiting the amount of time the telescope can be pointed in known directions to expose the mirror to a higher likelihood of impacts. of micrometeorites.

Preserving the long-term health of the Webb Telescope is a top priority for NASA and astronomers around the world.

After more than 20 years and $10 billion spent in development, the space telescope was launched atop an Ariane 5 rocket on Christmas Day. This launch was more accurate than expected, saving Webb considerable propellant he would have used to correct his trajectory after launch, and almost doubling the observatory’s expected operational life – as long as space rocks don’t spoil its optics.

“Prior to launch, JWST was expected to carry propellant for at least 10.5 years of the mission lifetime,” the report said. “Now that JWST is in orbit around L2, it is clear that the remaining thruster will last over 20 years of the mission lifetime.”

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