Gaia

Gaia, the Global Astrometric Interferometer for Astrophysics, is a European Space Agency astronomical observatory mission. Its goal is to create the largest, most precise three-dimensional map of the Milky Way by surveying about 1% of the galaxy's 100 billion stars.

Dec 19, 2013: Launch

Jan 8, 2014: Achieved operational orbit

Jul 25, 2014: Mission operations began

Sep 14, 2016: ESA released its first dataset from Gaia

Apr 25, 2018: ESA released a second dataset from Gaia

Gaia is a European space observatory whose goal is to chart a three-dimensional map of the Milky Way galaxy in order to reveal the composition, formation and evolution of the galaxy.

More specifically, Gaia provides high-quality measurements to produce a stereoscopic and kinematic census of about 1 billion stars in our galaxy (about 1% of the total) and the Local Group, the group of galaxies that includes the Milky Way.

Launched by a Russian Soyuz rocket, the Fregat upper stage pushed Gaia into a 109 × 109-mile (175 × 175-kilometer) Earth orbit, and then fired again for a long burn into a 214 × 598,200-mile (344 × 962,690-kilometer) orbit at a 15-degree inclination.

On Jan. 8, 2014, Gaia entered its operational orbit around the Sun-Earth L2 Lagrange point, about 932,000 miles (1.5 million kilometers) from Earth, when its engine fired to boost the spacecraft into a 163,000 × 439,000-mile (263,000 × 707,000-kilometer) halo orbit with a period of 180 days.

After four months of calibration, alignment and focusing of its telescopes, Gaia began its five-year mission July 25, 2014.

In its observation mode, Gaia spins once every six hours, sweeping its two telescopes across the entire sky and focusing the light it gathers onto a single digital camera—the largest flown in space—with nearly a billion pixels (106 CCDs each with 4,500 × 1,996 pixels).

It will observe a billion stars an average of 70 times each over five years. In September 2014, ESA announced that Gaia had discovered its first supernova, Gaia14aaa, some 500 million light-years from Earth.

A minor anomaly—“a stray light problem”— was detected shortly after launch that might degrade the quality of some of the results, especially for the faintest stars, but ESA scientists are confident they can compensate for the problem.

In August 2015, Gaia completed its first year of science observations, during which it recorded 272 billion positional or astrometric measurements, 54.4 billion photometric data points, and 5.4 billion spectra.

On Sept. 14, 2016, ESA released its first dataset from Gaia that included positions and G magnitudes for about one billion stars based on observations from July 25, 2014, to Sept. 16, 2015.

On April 25, 2018, ESA released a second dataset that included the positions for approximately 1.7 billion stars, as well as a measure of their overall brightness at optical wavelengths. Final Gaia results in the form of complete datasets are not expected to be publicly available until the early 2020s.

Besides its primary goal of mapping stars, Gaia also carries out observations of known asteroids within our solar system, providing data on the orbits and physical properties of these bodies.

NASA Space Science Data Coordinated Archive

Mission website

Mission extension

Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.