Yes, a small rock particle struck the Webb telescope. No, the mission is not doomed.
You may have seen headlines claiming that the James Webb Space Telescope, the most powerful observatory ever built, has sustained permanent damage. That’s an excerpt from a new 55-page report describing the instrument’s outstanding scientific performance over the past six months, as engineers prepared and tested its unprecedented cosmic-viewing capabilities.
Overall, the Webb telescope is in excellent condition. Here’s what you should know about the observatory’s current state, which will revolutionize our understanding of the universe.
NASA and its collaborators, the Canadian Space Agency and the European Space Agency, concluded that Webb is “fully capable of achieving the discoveries for which it was built,” even after a speeding micrometeoroid (a small, often dust-sized rock particle) hit and caused a “significant uncorrectable change” to one of the telescope’s 18 gold-coated hexagonal mirrors.
Most importantly, they expect Webb to outperform expectations. “Moreover, almost everywhere, the science performance of JWST exceeds expectations,” Webb’s scientists wrote.
“JWST’s science performance has exceeded expectations.”
Why is Webb expected to outperform? Its mirrors are cleaner than what is required to meet its lofty scientific goals. Its guidance system, which locks onto and tracks targets, is superior. Furthermore, its overall performance in clearly viewing objects exceeds requirements.
As if that weren’t enough good news, Webb’s scientists have determined that it has enough finite fuel aboard to power the mission for the next 20 years. (In order to reach its outpost 1 million miles from Earth, the telescope used less propellant than planned.) NASA had hoped the instrument would last five years, and the agency was initially relieved to learn it could operate with sufficient propellant for more than ten years.
Six micrometeoroids were detected during the six months that scientists prepared the $10 billion telescope for its much-anticipated science operations. They did, in fact, anticipate one hit per month. “Inevitably, any spacecraft will encounter micrometeoroids,” according to the report. Five of the six hits had negligible effects.
However, the impact between May 22 and 24 was strong enough to cause a “significant uncorrectable change” in one of Webb’s 18 hexagonal mirror segments, as previously stated (segment C3). Fortunately, the observatory’s mirror, which collects faint light from the faraway cosmos, is quite large, measuring more than 21 feet across. This means that the majority of the telescope is unaffected.
“However, because only a small portion of the telescope area was affected, the effect was small at the full telescope level,” Webb’s scientists wrote.
What’s more, after the strike, Webb engineers worked to make slight adjustments to the mirror’s alignment, which limited any small imaging errors. “Webb’s ability to sense and adjust mirror positions allows for partial impact correction,” NASA previously stated. “Engineers can cancel out a portion of the distortion by adjusting the position of the affected segment.”
Only time will tell whether this impact was unusual or if it was more common than Webb scientists estimated.
“It is not yet clear whether the May 2022 hit to segment C3 was a rare event (i.e. an unlucky early strike by a high kinetic energy micrometeoroid that statistically may occur only once every few years), or whether the telescope may be more vulnerable to micrometeoroid damage than pre-launch modeling predicted,” the report concluded.
If it is discovered that Webb is more vulnerable to damage, NASA and its Webb partners can consider reducing the amount of time the telescope spends peering in directions where there are more micrometeoroids flying through space, or pointing the telescope away during certain meteor showers.
For the time being, however, the telescope is poised for success.
“JWST has begun the first of many years of scientific discovery with revolutionary capabilities,” the report concluded.