Farewell to Gaia, the spacecraft that mapped the Milky Way

After more than a decade of charting the stars with extraordinary precision, the European Space Agency’s Gaia spacecraft has completed its mission. 

On March 27, mission controllers at ESA’s European Space Operations Center (ESOC) powered down Gaia for the last time, sending the spacecraft into a carefully planned solar orbit that will keep it far from Earth for at least a century.

Though Gaia’s systems are now silent, its scientific impact is just beginning to unfold.

A decade of galactic discovery

Launched in 2013, Gaia set out to map the Milky Way with a level of detail never before achieved. Over the years, it recorded the positions, motions, distances, and physical properties of nearly two billion stars. 

The resulting data has revolutionized our understanding of galactic structure and evolution, and provided insight into everything from black holes and exoplanets to asteroids, comets, and distant galaxies.

“Gaia’s extensive data releases are a unique treasure trove for astrophysical research, and influence almost all disciplines in astronomy,” said Gaia Project scientist Johannes Sahlmann.

The mission’s legacy is already profound. It revealed the remnants of ancient galactic mergers, discovered new star clusters, and enabled the most accurate visualisation of the Milky Way’s appearance from the outside. 

Even with the spacecraft now decommissioned, its data releases will continue. A fourth major data release is scheduled for 2026, with a final “legacy” catalogue expected after 2030.

Challenge of powering down spacecraft

Gaia was designed to survive the hazards of space – radiation storms, micrometeoroid impacts, and lost contact with Earth. Redundant systems ensured it could restart itself and resume operation after nearly any disruption. That resilience made powering it down especially delicate.

“Switching off a spacecraft at the end of its mission sounds like a simple enough job,” said Spacecraft Operator Tiago Nogueira. “But spacecraft really don’t want to be switched off.”

To prevent any chance of Gaia reactivating, the team at ESOC developed a precise decommissioning sequence. They carefully disabled its instruments and subsystems, one by one. 

The team also deliberately corrupted its software, ensuring that even if Gaia’s solar panels catch sunlight again, it won’t resume transmission.

Keeping Gaia at a safe distance

“I was in charge of corrupting Gaia’s processor modules to make sure that the onboard software will never restart again,” said Spacecraft Operations Engineer Julia Fortuno. 

“I have mixed feelings between the excitement for these important end-of-life operations and the sadness of saying goodbye to a spacecraft I have worked on for more than five years.”

Before shutting it down completely, Gaia’s thrusters were fired one last time, nudging it away from the second Lagrange point (L2), its long-time observing post, and into a retirement orbit around the Sun. 

That move ensures Gaia will stay at a safe distance from Earth – more than 10 million kilometers – for the next century or more.

The enduring legacy of Gaia

Although Gaia’s instruments are now quiet, the spacecraft’s contributions to science will echo for decades. ESA missions already in orbit, such as Euclid, rely on Gaia’s star maps for accurate orientation. 

The upcoming PLATO mission, designed to search for exoplanets, will build on Gaia’s detailed stellar data to target stars that are most likely to host planets.

Gaia also spent its final weeks in service conducting technology tests. Engineers examined how its micropropulsion system had aged after more than ten years in space – data that could prove invaluable for future missions such as ESA’s LISA observatory, which will detect gravitational waves using similar propulsion.

But the mission’s farewell also carried a deeply human element. As a symbolic gesture, the names of around 1,500 people who worked on Gaia were written into its onboard memory, overwriting parts of the backup software. 

Personal farewell messages were also added, allowing the spacecraft to carry a lasting tribute from its team as it drifts silently through the solar system.

Saying goodbye, but not letting go

ESA has long emphasized responsible spacecraft disposal, and Gaia’s deactivation reflects that commitment. Still, for the scientists and engineers who worked on it, the moment was bittersweet.

“We will never forget Gaia, and Gaia will never forget us,” said Gaia Mission Manager Uwe Lammers.

The spacecraft may no longer be gathering data, but its legacy is secured. Gaia has charted a new path for galactic exploration – one that future astronomers will follow for generations.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–