Gaia is a space observatory of the European Space Agency (ESA) designed for astrometry. The mission aims to construct a 3D space catalog of approximately 1 billion astronomical objects, mainly stars (approximately 1% of the Milky Way population) brighter than 20 G magnitude, where G is the Gaia magnitude passband between about 400 and 1000 nanometres light wavelengths. Additionally Gaia is expected to detect thousands to tens of thousands of Jupiter-sized planets beyond the Solar System, 500,000 quasars and tens of thousands of new asteroids and comets within the Solar System. The spacecraft will monitor each of its target stars about 70 times over a period of five years.