Gaia star mapping mission hit by micrometeoroid and solar storm – Sky & Telescope

The European Space Agency's Gaia mission, now in operation for a decade, is in the process of mapping the positions and velocities of More than a billion stars in the Milky Way. It is is not easy In achieving this feat in space, Gaia has recently faced two major obstacles, but the spacecraft is now fully operational again.

In April, a micrometeoroid smaller than a grain of sand blew through the protective shroud of Gaia’s telescope, allowing occasional unwanted scattered light to hit its detectors. While the mission is no stranger to micrometeoroids, this one came at high speed and at the wrong angle.

In May, a key sensor failed — part of the observatory’s billion-pixel CCD camera. It was supposed to help Gaia confirm it was observing a star. Without that sensor, the detectors began recording thousands of erroneous readings.

Sensor degradation occurred just after a massive solar ejection. shocked On May 10, Earth's space weather environment surprised observers with an aurora at low latitudes around the world. Although Gaia's hardware is designed to withstand space radiation, the spacecraft is aging and the storm tested its limits.

The key problem with both scattered light and CCD sensor failure is that the spacecraft can generate many more false positive Detections (seeing a star where there isn't one) can overload the system. The mission usually sends back more than 25 gigabytes of data each day, but it would be much more if the onboard computer didn't filter out the fake stars first.

Since ESA engineers cannot physically reach the spacecraft to repair it, they came up with a software-based solution. By simply changing the threshold at which the software reports that a faint point of light is a star, the system can reduce the number of false detections even without the sensor. This solution has minimal scientific impact.

“The solution to keep Gaia running in the end is to have minimal impact on scientific performance,” Prusti says. “It is good to note that Gaia was able to perform scientific measurements at all times. The solution to the problems was to prevent false positives from being stored in memory and transmitted over the network.”

These problems even gave ESA engineers an unexpected opportunity to reorient the twin optical systems on board Gaia, a first since the mission began. Now, engineers report that the mission is sending back some of the highest-quality data of the entire mission.

Gaia: 10 years and counting

Launched in late 2013, Gaia has long since outgrown its nominal five-year mission, having recently reached 10 years in space. Its top science priority is astrometryor the precise measurement of the positions of stars in the sky. It also takes stellar spectra, measuring the radial velocitythe speed at which stars are traveling toward or away from us.

The mission has revolutionized astronomy with its measurements of stars in the Milky Way, including our understanding of the history of our galaxy and the birth and evolution of stars themselves. Not only is the mission helping astronomers determine stellar distances, but the observations have also revealed quasars, exoplanets and asteroids.

Gaia's home is in the orbit of the Sun and the Earth.₂ Lagrange point, 1.5 million kilometres from Earth. The probe orbits around this point, as do the James Webb Space Telescope and ESA's Euclid mission (the orbits of the various probes differ, so there is no risk of collisions).

“Gaia’s operations are nominal and the spacecraft can cope with micrometeoroids and the normal solar wind without any problems,” says Gaia project scientist Timo Prusti (ESA). “The events a few months ago that caused the problems that have now been resolved were quite exceptional.”

However, he acknowledges that aging hardware played a role: “(The problems) could also be related (to the fact) that Gaia has already been 'bombarded' during (its) more than 10 years in space. That's about four years longer than the engineering requires.”

“These issues with the spacecraft and the upcoming launch… are not related,” Prusti says. Gaia’s next data catalog (known as DR4) includes data from the mission’s early years and will be released around mid-2026, he says.

“The impact of these issues needs to be addressed in Gaia’s fifth data release,” he notes. “Further calibration work will be required, but this is within the normal procedures already in place for Gaia.”

It's great to see a mission crisis turn into an opportunity. Gaia may be aging, but the pioneering mission is far from out of the woods.