But the direct hit on a mirror surprised NASA and is still being analyzed. Details of the micrometeoroid strike were revealed by NASA in a dedicated Webb blog post.
“Between May 23 and 25, NASA’s James Webb Space Telescope suffered an impact on one of its main mirror segments,” said NASA’s Webb blog. “After initial evaluations, the team found that the telescope still performed at a level that exceeded all mission requirements despite a marginally detectable effect in the data.”
The mirror’s 18 segments can be individually adjusted in response to meteoroid impacts such as this, NASA said.
“By adjusting the position of the affected segment, engineers can undo some of the distortion…although not all of the degradation can be undone this way,” the NASA blog said. “Engineers have already made a first such adjustment for the recently affected segment…and additional planned mirror adjustments will continue to refine this fix.”
The exact size of the micrometeoroid is not known. It may have been no bigger than a grain of sand, said Heidi Hammel, a planetary astronomer long involved with the telescope. and will use it to study our solar system. Even something so small can cause damage due to the lightning speed at which the telescope orbits the sun and periodically collides with a random particle.
It was a known danger, because although he is alone in space, it is not as empty as it seems.
“There is no loss of science at all from this event. … This telescope is out there in space – we knew there would be tiny impacts on it. We were just surprised that one hit so soon,” Hammel said.
She said scientists had anticipated such an impact every five years or so, on average.
This extraordinarily complex observatory, billed as the long-awaited successor to the still-functioning Hubble Space Telescope, orbits the sun in a position that keeps it about 1 million miles from Earth. It’s too remote for astronauts to visit, and it’s not designed to be repaired or to replace instruments.
The Webb has been going through a “commissioning” phase for months as its instruments are calibrated and the 18 gold-plated hexagonal mirrors are lined up to function as a single massive mirror about 21 feet in diameter.
So far, NASA has only reported success.
“Astronomers are giddy with how good things are going (but also nervous not to jinx it, yes we can be superstitious too) and eager to start doing science!” University of Chicago astrophysicist Michael Turner said in an email.
The telescope, folded in on itself at launch last year, bloomed over the course of several days as its sprawling sunshade opened and the mirrors unfolded. The telescope traveled for 29 days to reach its outpost, an orbital position known as L2 where other telescopes operated safely and offered scientists data on the frequency of micrometeoroids.
“During construction of the telescope, engineers used a mix of simulations and actual test impacts on sample mirrors to get a clearer idea of how to fortify the observatory for in-orbit operation. more recent was greater than what had been modeled and beyond what the team could have tested in the field,” said NASA’s Webb blog.
The Webb is unlike most telescopes: it’s wide open, with the mirrors exposed rather than tucked into a tube. The telescope is designed to observe the universe at infrared wavelengths that are outside Hubble’s detection range.
This requires extremely cold mirrors and instruments, this is why the mirrors are oriented away from the Earth and the sun at all times. NASA said images of “first light” will be released on July 12, but did not say what they will show.
However, it has already produced the image of a star, used to focus mirrors. In the background of this image are many galaxies whose light was emitted billions of years ago, and it has delighted astronomers who expect Webb to see further into space (and in the past) than Hubble, launched in 1990.
The Webb has multiple objectives, including the study of the first light in the universe, emitted a few hundred million years after the big bang. It will also examine the evolution of galaxies and study objects in our own solar system, including small icy bodies that orbit the sun far beyond the orbit of Neptune.