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Gaia is a cornerstone mission in the science programme of the European Space Agency (ESA) and a major project for astrophysics for the next two decades. Launched in December 2013, the spacecraft systematically observes the full sky in order to map the celestial objects with an unprecedented accuracy.


Gaia measures the 3D position, velocity and physical properties of 1.7 billion stars within our Galaxy making it possible to study in details its structure, kinematics, origin and evolution. Gaia also makes a census and characterizes more than 600 000 quasars, nearly one million nearby galaxies, as well as thousands of previously unknown objects such as dwarf planets and asteroids in the Solar system, brown and white dwarf stars, exoplanet or supernovae. Gaia has an essential contribution in the determination of the extragalactic distance scale and in fundamental physics.

  • Gaia at ESA :
  • Gaia-France :
  • French coordination : David Katz, GEPI, Observatoire de Paris, david.katz [at]
  • Local Contact : Caroline Soubiran, caroline.soubiran [at ]

Gaia data are provided in a form of a public catalogue containing the astrometric and photometric parameters of each measured object, their physical properties as well as spectroscopic data for the brightest stars. The catalogue can be queried through a dedicated web site at or through the VizieR interface at CDS. The second Gaia data release has been published in April 2018. The third Gaia data release is expected in 2020-2021.

Involvement of OASU

The OASU is involved in several tasks of the ANO4 observation service: acquisition of auxiliary data for the Gaia spectroscopy, coordination of ground-based follow-up activities for the acquisition of auxiliary data, morphological characterization of extragalactic objects. The OASU also contributes to the validation of the successives data releases before their publication.

The OASU is also involved in the ANO1 observation service for the definition of the Gaia optical reference system. In Bordeaux the tasks are (1) the acquisition and analysis of VLBI data of the most appropriate radiosources for the alignment of the Gaia frame and the radio frame ICRF (International Celestial Reference Frame), (2) the detection of disturbance host galaxies around quasars that would affect the reference frame, (3) the identification of quasars possibly affected by gravitational lenses.


The Gaia observation service is within the framework of Data Processing Analysis Consortium (DPAC) in charge of developing the data processing pipeline and producing the Gaia catalogues. The DPAC involves about 450 researchers and engineers in more than 100 laboratories and organisms in 23 countries. France is the largest contributor with about one hundred scientists in 7 OSUs and a data processing centre at CNES in Toulouse.