spacecraft with Milky Way in background

Artist's impression of the Gaia spacecraft. Credit: ESA

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 one per cent of the galaxy's 100 billion stars.

  • Gaia will detect and very accurately measure the motion of each star in its orbit around the center of the galaxy.

  • Each of the 1 billion stars that Gaia studies will be observed an average of 70 times over five years to create a record of the brightness and position of each star over time.

Launch Date Dec. 19, 2013 | 09:12:18 UT
Launch Site CSG / ELS pad
Launch Vehicle Soyuz-Fregat (Soyuz-ST-B / Fregat-MT SoyuzST-B no. E15000-004/104, Fregat-MT no. 1039)
Destination Sun–Earth L2 Lagrange Point
Type Orbiter
Status Operational
Agency European Space Agency
Alternate Names Global Astrometric Interferometer for Astrophysics


  • Attempting to create the largest, most-precise 3-D map of our galaxy, the Milky Way.

Key Dates

Launch: Dec.19, 2013 | 09:12:18 UT

Achieved Operational Orbit: Jan. 8, 2014

Mission Operations Began: July 25, 2014

stars and dust clouds in the milky way galaxy
Gaia's all-sky view of our Milky Way Galaxy and neighboring galaxies, based on measurements of nearly 1.7 billion stars. The map shows the total brightness and color of stars observed by the ESA satellite in each portion of the sky between July 2014 and May 2016. Credits: ESA/Gaia/DPAC; Map: CC BY-SA 3.0 IGO

In Depth

Objective(s): Sun–Earth L2 Lagrange Point

Spacecraft Mass: 4,473 pounds (2,029 kilograms)

Mission Design and Management: The Gaia spacecraft is controlled from the European Space Operations Centre (ESOC, Darmstadt, Germany) using the Cebreros (Spain), New Norcia (Australia), and Malargüe (Argentina) ground stations.

Science operations are conducted from the European Space Astronomy Centre (ESAC, Villafranca del Castillo, Spain).

Scientific Instruments:

1. astrometric instrument (ASTRO)

2. photometric instrument

3. radial velocity spectrometer (RVS)

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 positional and radial velocity measurements to produce a stereoscopic and kinematic census of about one billion stars in our galaxy (about 1% of the total) and the Local Group.

Launched by a Russian Soyuz, 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 × 598,189 mile (344 × 962,690-kilometer) orbit at 15.0° inclination.

On January 8, 2014, Gaia entered its operational orbit around the Sun-Earth L2, about 932,059 miles (1.5 million kilometers) from Earth, when its engine fired to boost the spacecraft into a 163,421 × 439,311 mile (263,000 × 707,000-kilometer) halo orbit around L2 with a period of 180 days.

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

In its observation mode, Gaia spins slowly (once every 6 hours), sweeping its two telescopes across the entire sky and focusing the received light simultaneously 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 each of its billion stars an average of 70 times over five years. In September 2014, ESA announced that Gaia had discovered its first supernova, Gaia14aaa, some 500 million lightyears away 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 that mitigation schemes will compensate for the problem.

In August 2015, Gaia completed its first year of science observations, during which it had 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.

Additional Resources

NASA Space Science Data Coordinated Archive​

Mission website


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

Mission extension

Solar System News