European Space Agency Bids Farewell to Gaia Mission
The ESA launched Gaia in December 2013 to build a 3D map of "more than a thousand million stars throughout our Milky Way galaxy and beyond." The spacecraft hitched a ride to space via a Soyuz-STB/Fregat-MT launch vehicle, which injected Gaia into the Sun-Earth Lagrange point 2, where Earth's and the Sun's gravitational pulls are balanced. Since then, Gaia has orbited the Sun at the same pace as Earth, collecting star data in unprecedented detail since the completion of its three-month post-launch calibration.
Gaia is known for having created the largest and most precise 3D map of the Milky Way to date. According to the ESA, it significantly surpassed its scientific goal by "racking up more than three trillion observations of about two billion stars. " It has also contributed to the discoveries of exoplanets, black holes, quasars, and neighbor galaxies outside our own. Though the spacecraft was only supposed to last a little over five years, it remained functional for more than double that time.
Credit: ESA/Gaia/DPAC, Milky Way impression by Stefan Payne-Wardenaar
But a decade-plus of continuously adjusting a spacecraft's positioning and movements burns fuel, and in January, it became clear that Gaia didn't have much time left. The ESA planned a series of technology tests and data downlinks to ensure the transmission of Gaia's last findings, then sent the spacecraft into its heliocentric "retirement" orbit far from Earth's gravitational influence. This would ensure the passive spacecraft wouldn't interfere with active missions in Gaia's original stomping grounds.
On March 27, the Gaia team deactivated and powered off Gaia's instruments and subsystems. They then corrupted the spacecraft's onboard software before deactivating Gaia's communication subsystem and central computer. The ESA notes that personal farewell messages from the mission team were written into Gaia's memory prior to its retirement.
"We will never forget Gaia, and Gaia will never forget us," mission manager Uwe Lammers said.
Though Gaia will never communicate with Earth again, a wealth of scientific findings are yet to come. In 2026, the Gaia team will publish Gaia Data Release 4, a 500TB trove of data covering the mission's first five and a half years. This data will expand Gaia's binary star catalog, as well as its list of exoplanets and "wobbling" stars. Gaia's findings also inform the ESA's Euclid mission and its upcoming Plato mission, ensuring the beloved spacecraft will benefit science for years to come.
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