Launched on 19 December 2013, Gaia reached its nominal operating position on January 15, 2014. The spacecraft orbits around the L2 Lagrangian point which is located 1.5 million kilometers beyond the Earth, along the Sun-Earth line in the direction opposite to the Sun which is 100 times farther away.
To achieve its science mission for the next 5 years, Gaia will slowly rotate scanning with its two telescopes the whole sky and focusing the light on a common focal plane where operates a billion pixels digital camera – the largest that has ever flown in space. Most of the parts of the sky will be observed more than 70 times. Sophisticated software will determine with unprecedented accuracy the positions of about one billion stars in the Milky Way (nearly 1% of all stars). This will allow us to measure their motion in the Galaxy, for many of them in three dimensions. This ambitious “inventory” of the Milky Way stellar population, is expected to greatly enrich our knowledge about the initial formation and subsequent dynamical and chemical evolution of the Galaxy, about the star formation and composition and the stellar evolution.
The Gaia instruments will observe also other objects of the Milky Way, as asteroids and stars of nearby galaxies. Also it is expected to observe a million or more unresolved galaxies (as point sources) in the nearby Universe and hundreds of thousands of distant quasars. The mission will realize a series of tests of General Relativistic light bending by the Sun and major planets.
The National Observatory of Athens (NOA) actively participates in the mission since 2006. Two researchers of the Institute of Astronomy, Astrophysics, Space Applications and Remote Sensing, Dr. I. Bellas-Velidis and Dr. A. Dapergolas, along with researchers of the University of Athens, form the Greek team of Data Processing and Analysis Consortium (DPAC), an international consortium of about 400 scientists and engineers that is responsible for the processing and analysis of the mission’s data. The objective of the Greek team is the classification and parameterization of the unresolved galaxies. For this purpose, its members develop specialized software for automatic processing of galaxies spectra. The system is based on artificial intelligence algorithms and “education” with spectral templates. The group is also responsible for the creation and providing to other groups libraries of such templates. The libraries are based on synthetic spectra created applying evolutionary models of galaxies and on real observed spectra.
Currently there are carried out the necessary checks of the satellite systems and the instruments in-orbit commissioning is expected to be completed in May. The software developed by researchers of the Greek team will be fully operational by September 2014 for the first real application within the DPAC’s ground-based pipeline. The final database with the results of Gaia observations is expected to be completed after five cycles of processing and will be issued in 2022.