Scientists report that damage to the James Webb Space Telescope (JWST) caused by a micrometeoroid impact in late May 2022 may be more severe than previously believed.
A group of scientists evaluated the performance of the space telescope throughout its commissioning phase in a new report released last week following Webb's amazing first photographs.
They reported problems that “cannot be corrected” as well as a “small effect on the telescope throughput, which is not yet measurable.”
Writing about the projected lifetime of the Webb telescope the report said: “At present, the largest source of uncertainty is long term effects of micrometeoroid impacts that slowly degrade the primary mirror.”
As previously stated, the main 6.5-meter mirror of Webb is composed of 18 beryllium-gold segments. Small dust particles impacted one of them, designated C3, between May 23 and May 25, 2022.
Webb has been impacted by five more, smaller micrometeoroids since its launch. Approximately one small incident per month was foreseen by engineers before launch.
Thomas Zurbuchen, the Associate Administrator of NASA's Science Mission Directorate, tweeted after the C3 impact, “After initial assessments, the team found the telescope is still performing at a level that exceeds all mission requirements,”
The current research, however, reveals that the damage to the C3 section may be more severe than previously believed.
“Of the six micrometeoroid strikes detected thus far through wavefront sensing, five had negligible effects,” reads the report. Wavefront sensing refers to the aberrations found in Webb’s optics. “By contrast, the micrometeoroid which hit segment C3 in the period 22—24 May 2022 UT caused a significant uncorrectable change in the overall figure of that segment.”
Moreover, the report said that this event “exceeded prelaunch expectations of damage for a single micrometeoroid, triggering further investigation and modelling by the JWST Project.”
The engineers who constructed Webb are aware that its mirrors and sunshield would inexorably deteriorate over time due to micrometeoroid strikes, even though it may have enough propellant to endure for 20 years – a decade longer than originally anticipated.
It is also anticipated that charged particles would eventually harm Webb's detectors, while its sunshield and ingenious five-layer insulation will deteriorate due to space weathering.
Webb has a harder time avoiding micrometeoroid hits since its mirror is exposed to space. Any spacecraft would always meet micrometeoroids, according to the paper, which describes "six localised surface deformations on the primary mirror that are attributed to impact by micrometeoroids.”
Was the "C3 impact" a random event?The study said, "“It is not yet clear whether the May 2022 hit to segment C3 was a rare event or whether the telescope may be more susceptible to damage by micrometeoroids than pre-launch modelling predicted,"
The researchers will now analyse the micrometeoroid population in Webb's neighborhood, how hits harm beryllium-gold mirrors, and how it prevents further impacts.
According to the paper, minimising time spent staring in the direction of orbital motion, which has statistically higher micrometeoroid rates and energies, might be a potential solution.
Reference(s): Research Paper(pdf)
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