The ESA announced that Gaia’s primary mission was coming to an end. The spacecraft’s fuel is running out and the sky-crawling phase of its mission is over. This revolutionary mission made it possible to carry out more than three thousand billion observations on two billion objects, mainly stars.
ESA launched Gaia in December 2013. It is a astrometry mission that measures the positions, movements and distances of stars with extreme precision. He created the largest and most precise 3D map of space ever made, including around a billion objects, mostly stars but also quasars, comets, asteroids and planets.
Gaia’s mission lasted twice as long as expected and its data changed astronomy. It serves as the basis for many new discoveries and knowledge about the Milky Way. Astronomy and astrophysics would be far behind where they are today without Gaia. Regular readers of Universe Today have frequently encountered his data.
“Today marks the end of scientific observations and we celebrate this incredible mission which has exceeded all our expectations, lasting almost double its originally planned lifespan,” said Carole Mundell, ESA’s science director. “The trove of data collected by Gaia has given us unique insight into the origin and evolution of our galaxy, the Milky Way, and has also transformed astrophysics and solar system science in ways that we have not yet fully appreciated. Gaia builds on unique European excellence in astrometry and will leave a lasting legacy for future generations.
Gaia has not always had it easy at its position at the Sun-Earth Lagrange point L2, about 1.5 million kilometers from Earth. In April 2024, a tiny micrometeorite smaller than a grain of sand impacted, punching a tiny hole in the satellite’s protective cover. The hole let a tiny bit of sunlight into the spacecraft, disrupting its sensors. In May 2024, a solar storm struck and the device suffered an electronic malfunction that resulted in an excessively high number of false detections. In both cases, Gaia recovered and continued normal operations.
Gaia has three instruments that allow it to be so precise. Its astrometric instrument (ASTRO) determines the position of stars in the sky. By measuring the same stars multiple times in different years, Gaia can measure a star’s position and proper movement.
Gaia’s Radial Velocity Spectrometer (RVS) measures the Doppler shift of a star’s absorption lines. This reveals the star’s speed along Gaia’s line of sight.
The Photometric Instrument (BP/RP) provides information on the color of stars, allowing astronomers to measure critical stellar characteristics such as mass, chemical composition and temperature.
These instruments worked together to create the largest and most accurate map of the Milky Way ever made.
Among its other achievements, Gaia has captured with pinpoint precision the orbits of more than 150,000 asteroids, precise enough to discover possible moons. He also discovered a new type of black hole revealed only by its gravitational influence on nearby stars.
Even though its scientific operations are completed, it still has data to provide.
“After 11 years in space and surviving micrometeorite impacts and solar storms, Gaia has finished collecting scientific data. Now all eyes are on preparing for the next data releases,” says Johannes Sahlmann, Gaia project scientist.
“This is the version of Gaia that the community has been waiting for, and it’s exciting to think that it only covers half of the data collected.”
Antonella Vallenari, Vice-President of DPAC, Istituto Nazionale di Astrofisica (INAF), Padua, Italy.
Version 4 (DR4) of Gaia data is expected in 2026. The volume and quality of data has increased with each DR. DR 4 is expected to contain 500 terabytes of data covering the first 5.5 years of the mission, corresponding to the originally planned duration of the mission.
“This is the version of Gaia that the community has been waiting for, and it’s exciting to think that it only covers half of the data collected,” says Antonella Vallenari, vice president of DPAC based at the Istituto Nazionale di Astrofisica (INAF), Astronomical Observatory of Padua, Italy. “Even though the mission has now stopped collecting data, we will be able to continue business as usual for many years to come as we make these incredible datasets ready for use.” »
The data release will feature, among other things, more binary stars and exoplanets.
The final release of Gaia data, DR5, will be expected in a few years. “Over the coming months, we will continue to connect every drop of data from Gaia, and at the same time, the processing teams will accelerate their preparations for the fifth and final major data release at the end of this decade, covering the entire of version 10.5. years of mission data,” says Rocio Guerra, Gaia’s science operations team leader based at ESA’s European Space Astronomy Center (ESAC) near Madrid, Spain.
Although the fuel that allows it to point with such precision is almost gone, Gaia is not yet on the verge of extinction. It still has enough fuel for approximately 15 days of operations. Instead of using his last 15 days to take more astrometric measurements, he will carry out technological tests.
“The Gaia spacecraft was built using a wide range of technologies that were combined to create a single machine operating in a very stable environment,” explains the ESA. “The stability of the spacecraft is essential for scientific observations. These technological tests would have disrupted the spacecraft for an extended period and therefore could not have been carried out during the normal scientific observation campaign.
These tests will teach engineers more about Gaia’s instruments and allow engineers to study their behavior as well as that of the spacecraft as a whole. The goal is to improve calibrations for future versions of Gaia data. They will also inform the design of the next mission.
“Some Gaia technologies have already been reused, for example mirror-drive electronics and cold gas thrusters from EUCLID,” the ESA writes. Other future missions like Lisa will require extreme precision, and the results of these tests can help them achieve it.
Once its tests are completed, Gaia will be placed in a heliocentric orbit, far from the influence of Earth. By the end of March 2025, it will be passivated to avoid any potential damage or disruption to other spacecraft.
Although the mission will end, Gaia’s data will be used for decades. So, in that sense, it will endure.