Sand grain-sized space rock pierces $800 million Gaia telescope’s shield

Space is a harsh environment, even for the most advanced spacecraft. The European Space Agency’s (ESA) Gaia telescope—on a mission to map a billion stars in our Milky Way galaxy—recently encountered some significant operational hurdles.

A micrometeoroid struck the space telescope in April, causing damage to Gaia’s protective covering.

This could threaten the space telescope performance, which has been reportedly built at the cost of over $800 million.

Space rock and energetic particles from Sun

Millions of these tiny micrometeoroids on Earth burn up harmlessly in the atmosphere. But Gaia faces a different reality. Stationed 1.5 million kilometers away at the L2 Lagrange point, it’s far beyond our planet’s protective shield. These impacts are a known hazard, and Gaia’s design incorporates safeguards to endure them.

Usually, these tiny rocks aren’t a problem. But this time, one came in quickly and hit at just the wrong angle.

It punched a small hole in Gaia’s shield. This hole lets in a tiny bit of sunlight, just a billionth the strength of sunlight on Earth. Even a small amount of light can mess with Gaia’s highly sensitive instruments.

While engineers were dealing with the micrometeoroid issue, another issue surfaced. Gaia’s strong billion-pixel camera uses charge-coupled devices (CCDs), which are unique light detectors.

These convert the light it sees into electrical signals the spacecraft can understand.

The ESA engineers noticed one of Gaia’s 106 CCDs had malfunctioned. Each CCD is designed for a particular task, and the broken one affects the sensor’s capacity to confirm star detection.

“Without this sensor to validate its observations, Gaia began to register thousands of false detections,” the ESA release noted.

The exact cause of the CCD’s electronic failure is unclear, but it coincided with a severe solar storm that caused auroral light displays across some parts of the globe.

Gaia was only supposed to last about six years in space, but it’s been up there for almost twice that long. In recent years, Gaia has been able to withstand radiation.

ESA highlights that this recent extreme event might have pushed it to its limits.

How ESA tackled the issue

The engineers from various centers, Airbus Defence and Space, and other experts came together to tackle these problems. They couldn’t physically repair Gaia from 1.5 million kilometers away, so the solution involved software. By adjusting how Gaia’s software recognizes stars, they were able to drastically minimize the number of erroneous detections caused by both stray sunlight and the CCD problem.

“Gaia typically sends over 25 gigabytes of data to Earth every day, but this amount would be much, much higher if the spacecraft’s onboard software didn’t eliminate false star detections first,” explained Edmund Serpell, Gaia spacecraft operations engineer at ESOC, in the press release.

Serpell added: “Both recent incidents disrupted this process. As a result, the spacecraft began generating a huge number of false detections that overwhelmed our systems. However, by carefully modifying the threshold at which Gaia’s software identifies a faint point of light as a star, we have been able to dramatically reduce the number of false detections generated by both the straylight and CCD issues.”

While the immediate issues are under control, Gaia’s mission remains delicate. The unpredictable nature of space may pose future issues for its aging hardware.

The Gaia space observatory was launched in 2013. It has been working to create an accurate three-dimensional map of the Milky Way and beyond. Furthermore, it captures information on the stars’ motion, brightness, temperature, and composition. This comprehensive approach might aid scientists in understanding the origin, structure, and evolutionary history of our galaxy.