Space rock that smashed into NASA’s James Webb Space Telescope in May caused more damage than previously thought, report reveals
NASA‘s new super space telescope suffered more damage than first thought when it was hit by a space rock in May, a new report has revealed.
The $10 billion (£7.4 billion) observatory’s primary mirror was permanently altered when it was impacted by the single micrometeorite, NASA has revealed, although it won’t affect Webb’s ability to take mesmerising images like the first official ones released last week.
Analysis of the telescope during its commissioning phase revealed that five of the six micrometeorite strikes to its big mirror between January and June caused negligible damage.
However, an impact to a mirror segment labelled C3 in mid-May left the telescope with more damage that can be fully corrected for.
‘The single micrometeorite impact that occurred between 22 — 24 May 2022 UT exceeded prelaunch expectations of damage for a single micrometeoroid triggering further investigation and modelling by the JWST Project,’ the report read.
The commissioning period was a painstaking process which began shortly after Webb reached space and lasted until just a few weeks ago, when ground controllers successfully completed the calibration, alignment, and testing of the telescope’s mirrors and instruments.
During that time, five micrometeoroid strikes caused little damage equating to less than 1 nanometer of wavefront error root mean square (RMS), which is a technical way to describe how much Webb’s mirror distorts the starlight the mirror collects.
Most of the distortion added by these impacts can be corrected out of the mirror because the 18 hexagonal segments that make it up can be individually and finely adjusted.
However, the sixth one raised the wavefront error of the segment from 56 nanometers to 178 nanometers after correction by adjusting the segment.
This damage to the C3 segment could still be compensated for, however, and did not compromise the resolution of Webb’s primary mirror as a whole.
The report added: ‘The micrometeoroid which hit segment C3 in the period 22—24 May 2022 UT caused significant uncorrectable change in the overall figure of that segment.
‘However, the effect was small at the full telescope level because only a small portion of the telescope area was affected.’
Micrometeoroid strikes are a problem for Webb because its 21ft (6.5m) diameter mirror is exposed to space, unlike its predecessor Hubble.
But due to its orbit 1 million miles (1.5 million km) from Earth, at a point called the second Lagrange point or L2, experts only expected Webb to encounter potentially hazardous micrometeorites about once per month.
Webb’s primary mirror consists of 18 hexagonal segments of gold-plated beryllium metal, and measures 21 feet 4 inches (6.5 metres) in diameter. It is supported by three shallow carbon fibre tubes, or struts, that extend out from the primary mirror
Webb’s infrared capabilities allow it to ‘see back in time’ to the Big Bang, which happened 13.8 billion years ago. Light waves move extremely fast, about 186,000 miles (300,000 km) per second, every second. The further away an object is, the further back in time we are looking. This is because of the time it takes light to travel from the object to us
Spectacular: Pictured is the first image from the James Webb Space Telescope, showing SMACS 0723, a galaxy cluster billions of light-years from Earth
‘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 might occur only once in several years),’ the report read, ‘or whether the telescope may be more susceptible to damage by micrometeoroids than pre-launch modelling predicted.’
The Webb team are now looking at what can be done to mitigate future micrometeorite strikes, including potentially limiting how long the telescope is pointed in directions known to expose the mirror to a higher probability of these impacts.
Last week Webb’s dazzling, unprecedented images of a ‘stellar nursery’, dying star cloaked by dust and a ‘cosmic dance’ between a group of galaxies were revealed to the world for the first time.
It put an end to months of waiting and feverish anticipation as people across the globe were treated to the first batch of a treasure trove of images that will culminate in the earliest ever look at the dawn of the universe.
Webb’s infrared capabilities mean it can ‘see back in time’ to within a mere 100-200 million years of the Big Bang, allowing it to snap pictures of the very first stars to shine in the universe more than 13.5 billion years ago.
Its first images of nebulae, an exoplanet and galaxy clusters triggered huge celebration in the scientific world, on what was hailed a ‘great day for humanity’.
Researchers will soon begin to learn more about the galaxies’ masses, ages, histories and compositions, as Webb seeks to explore the earliest galaxies in the universe.
A report was published on the academic preprint server arxiv.org.
