ESA's billion-star surveyor Gaia, launched on December 19, 2013, and in routine science operations since July 25, 2014, will release the first mission data on September 14, 2016. Gaia is designed to map more than 1 billion stars in our Galaxy, and to provide positions, parallaxes and proper motions at an unprecedented accuracy level, far below a milliarcsecond.
These accuracies can only be achieved after a complex data processing that requires observations taken throughout the 5-year nominal mission. For this reason, the final Gaia results will not be available until the early 2020s, but a number of early releases have been foreseen, based on increasingly longer stretches of observations.
The first Gaia data release, which will be available online on September 14, will include the positions and G magnitude for about one billion stars using observations taken between July 25, 2014 and September 16, 2015.
In addition, for a subset of data – about 2 million stars in common between the Tycho-2 Catalogue and Gaia – there will be a five-parameter astrometric solution, giving the positions, parallaxes, and proper motions for those objects. This is referred to as the Tycho-Gaia Astrometric Solution (TGAS).
Photometric data for RR Lyrae and Cepheid variable stars that were observed frequently during a special scanning mode that repeatedly covered the ecliptic poles will also be made public.
The announcement of the date for this first Gaia data release was made today by Anthony Brown, Chair of the Gaia Data Processing and Analysis Consortium (DPAC) Executive, during the GREAT Network Science Symposium at the European Week of Astronomy and Space Science held in Athens, Greece. DPAC is a large pan-European team of expert scientists and software developers, including a contribution from ESA, that has been given the task of preparing for and producing the Gaia catalogs.