In his new home far from Earth, the James Webb Space Telescope may not be as lonely as it seems.
The space pocket of the telescope is not a total void, and now the inevitable has passed, with a small piece of rock, a micrometeorite, colliding with one of Webb’s mirror segments.
But don’t panic. The engineers who built the telescope are well aware of the rigors of space, and Webb has been carefully designed to withstand them.
“We always knew that Webb should withstand the space environment, which includes harsh ultraviolet light and charged particles from the Sun, cosmic rays from exotic galaxy sources, and occasional micrometeoroid shocks within our Solar System,” says the engineer. technician. the project director Paul Geithner of NASA’s Goddard Space Flight Center
“We have designed and built Webb with a range of performance (optical, thermal, electrical, mechanical) to ensure that it can carry out its ambitious scientific mission even after many years in space.”
Webb’s position in L2. (NASA)
Webb occupies a region 1.5 million kilometers (just under 1 million miles) from Earth called L2.
This is known as the Lagrange or Lagrangian point, where the gravitational interaction between two orbiting bodies (in this case, the Earth and the Sun) is balanced by the centripetal force of the orbit to create a stable pocket where low-mass “parked” objects can be found to reduce fuel consumption.
This is very useful for science, but these regions can pick up other things as well.
Jupiter, for example, has swarms of asteroids that share its orbit at two of the Lagrange points it shares with the Sun. Other planets also have asteroids at their Lagrange points, though far less than Jupiter.
It is not clear exactly how much dust L2 has collected, but it would be absurd to expect that the region would not have collected any dust at all.
Thus, Webb was specifically designed to withstand the bombardment of dust-sized particles traveling at extremely high speeds. Webb’s design not only involved simulations, but engineers conducted impact tests on mirror samples to understand what the effects of the space environment might be and try to mitigate them.
Impacts can move mirror segments, but the telescope has sensors to measure the positions of the mirrors and the ability to adjust them, to help correct any distortion that may occur.
Mission control here on Earth can also send adjustments to Webb to place the mirrors where they should be. Its optics can even move away from previously known meteor showers.
And Webb was built with massive margins of error, so the expected physical degradation over time will not bring the mission to a premature end.
Orbital debris impact damage to Hubble panels returned to Earth after a service mission. (NASA)
It is likely to be in a better position than Hubble, which, in low Earth orbit, has been subject not only to micrometeorite impacts, but to a constant bombardment of space debris.
Unlike Hubble, however, the distance to Webb means that technicians will not be able to physically visit or make repairs. (Not that Hubble received the service recently; the last such mission was in 2009 and will not receive another).
The micrometeoroid that struck the telescope between May 23 and 25 was a random event. The impact, however, was greater than expected, meaning that it represents an opportunity to better understand the L2 environment and try to find strategies to protect the telescope in the future.
“With Webb mirrors on display in space, we expected the occasional impact of micrometeoroids to gracefully degrade the telescope’s performance over time,” says Webb Optical Telescope Element Manager Lee Feinberg of NASA Goddard.
“Since the launch, we’ve had four times smaller measurable micrometeoroids that were consistent with expectations, and this one more recently is larger than our degradation predictions assumed.
“We will use this flight data to update our performance analysis over time and also develop operational approaches to ensure that we maximize Webb’s image performance to the best extent possible for many years to come.”
Webb’s first full-color, spectroscopic images are yet to arrive on July 12, 2022. We can’t wait.