Gaia is an ESA cornerstone astrometric mission that was launched in 2013, whose main goal is to provide absolute astrometry that is a 100 times more accurate than its predecessor Hipparcos. It will target much fainter objects down to a magnitude G ∼ 21 mag, thus providing a catalogue of two billion objects covering the entire sky.
The ambition of Gaia is to provide a homogeneous census of the positions, parallaxes, and proper motions for as much as 1% of the stars in the Milky Way. Gaia will be able to measure high precision parallaxes with uncertainties of the order of 0.01 mas at G ∼ 21 mag, (at the end of the mission).
Gaia is also equipped with a spectrograph, to measure line-of-sight velocities of millions of stars of various spectral types, down to G ∼ 16-17 mag.
OATo is leading the Italian participation to Gaia and is scientific advisor to the Torino data processing center at ALTEC spa, which is one of the six main processing centers in Europe.
Before the launch, OATo provided the Initial Gaia Source List. At the moment, the activities range from the fundamental instrumental calibrations, providing a model for the Astrometric Focal plane and calibrating the Basic Angle Monitoring on board, to the treatment of non-single star solutions for the detection and characterization of exoplanets. In particular, the OATo team is responsible of the definition of an independent astrometric solution that will act as a validation unit for the final catalogue. In addition, OATo researchers have been prominent in the scientific exploitation of initial data releases.
The mission was formally approved by ESA in 2000, as part of its Horizon 2000 Plus program. Launch occurred successfully in December 2013. The nominal 5-years of Gaia observations were completed in July 2019, but the onboard fuel reserve is expected to keep Gaia operational until 2024.