Gaia is a pioneering ESA astronomy mission set to revolutionise our view of the Galaxy with a precise and detailed stereoscopic survey of the billion brightest celestial objects. High-accuracy astrometry will allow Gaia to exactly pinpoint the position of a star and to measure its movement across the sky, whilst spectroscopic measurements will allow the radial velocity to be determined. Gaia will also gather photometric data, measuring the brightness of a star in a few dozen colours. This array of data will reveal a moving, three-dimensional Milky Way map of unprecedented scope and precision, as well as providing profiles of the physical properties of each star, including luminosity, surface gravity, temperature and elemental composition. Selected as an ESA Cornerstone mission in 2000, Gaia is currently set to launch in late 2011.
Gaia continues a European tradition for pioneering astrometry, building on expertise generated by the first space-based astrometry mission, Hipparcos. By surveying all celestial bodies down to the very faint magnitude 20, Gaia will take in a representative fraction of the Milky Way’s population, providing scientists with the data to tackle unanswered questions about our home galaxy, potentially revealing its formation history, current state and future evolution. This catch-all survey will naturally include stars in short-lived phases of stellar evolution, and numerous binary and multiple stars, as well as several thousand brown dwarfs and extra-solar planets. Gaia will also map out our immediate neighbourhood in great detail, detecting hundreds of thousands of minor Solar System bodies.
Beyond the Milky Way, Gaia will observe extra-galactic objects like supernovae and quasars, and resolve many distant galaxies. Advanced processing and analysis will translate Gaia’s raw data into the mission’s final product: the Gaia Catalogue, an extensive galactic census, rich in scientific content. The unprecedented accuracy and unbiased nature of this full-sky survey will prove valuable, even revolutionary, to a huge range of scientific disciplines besides galaxy studies; Gaia’s wealth of data will eventually inform and invigorate scientific areas as diverse as stellar life cycles, dark matter distribution and general relativity. As a complete sky survey without pre-programmed targets, the discovery potential of Gaia is also profound. The nature of the Gaia mission leads to the acquisition of an enormous quantity of complex, extremely precise data, representing the multiple observations of a billion diverse objects by a ‘double vision’ instrument that is spinning and precessing. The Gaia data challenge - processing raw satellite telemetry into valuable science products - is therefore a huge task in terms of expertise, effort and dedicated computing power.
A large pan-European team of expert scientists and software developers known as DPAC (Data Processing and Analysis Consortium) is responsible for the processing of Gaia‘s data with the final objective of producing the Gaia Catalogue. François Mignard, Team leader of the Gaia team at OCA, is Chair Manager of the DPAC.