In April, Gaia was hit at high speed by a tiny particle smaller than a grain of sand. Earth is constantly bombarded by so-called micrometeoroids, but they burn up in the atmosphere. Because Gaia is located 1.5 million kilometers from our planet—far beyond Earth’s protective atmosphere—it often gets hit by micrometeoroids.
Normally a space telescope can handle this quite well, but in this case the particle hit at high speed at exactly the wrong angle, damaging Gaia’s protective shield. This created a hole through which sunlight could “sneak in”, disturbing the very sensitive sensors.
While Gaia’s technicians were working on this problem, another one emerged: One of the space telescope’s more than a hundred CCD sensors, which convert light into electrical signals, had failed. This was a crucial sensor for detecting stars. As a result, Gaia began recording thousands of false detections. The disruption is suspected to have been caused by the Sun’s big explosion last spring.
Experts from ESA and the space telescope’s manufacturer, Airbus Defence and Space, have been working closely in recent months to solve the resulting problems. Of course, with a space telescope 1.5 million kilometres away, no parts can be replaced, but in this case the worst problems – stray light and false detections – can be circumvented with the help of software modifications. In fact, technicians have taken the opportunity to refocus the optics of the two telescopes that make up Gaia.
