Tags: Artificialsatellite, Satellite.
Gaia is an unmanned space observatory of the European Space Agency (ESA) designed for astrometry. The mission aims to compile a 3D space catalogue of approximately 1 billion astronomical objects (approximately 1% of the Milky Way population) brighter than 20 G magnitudes where G is the Gaia magnitude passband between about 400 and 1000 nanometres light wavelengths. Successor to the Hipparcos mission it is part of ESA’s Horizon 2000 Plus long-term scientific program.