Launched on 19 December 2013, the Gaia satellite has been designed for an ultra-precise European science astrometry mission. Its objective is to plot the stars on heaven’s canopy. Its payload, comprised of two almost identical telescopes, is a flagship of optoelectronic technology, the last word in astrophysical sciences. An achievement that is not unknown to the Liège Space Centre (CSL) and the astronomers of the University of Liège.

Gaia, the latest of the ESA’s (European Space Agency) space observatories, is now in its operational orbit around an equilibrium virtual point in space beyond the Earth on the Sun-Earth axis, known as L2 (Lagrange point 2). Around this L2 point, the strength of the gravitational forces due to the Sun and Earth equals the centrifugal force acting on the satellite. From this thermally stable orbital position, the Gaia observatory’s pair of telescopes will have access to an unrestricted view of a few percent of the Milky Way, enabling us to gain better knowledge of the celestial mechanics, understand the stellar dynamics, and discover the workings of the galactic machine. This astrometry mission is to characterise, with unequalled precision, a billion stars (i.e. 1% of them) in our galaxy in relation to their position, distance, movement, brightness, variability, multiplicity... And, in addition, to gather new data concerning the asteroids in the solar system, the exoplanets in the universe, quasars, black holes, brown dwarfs, binary stars, gravitational lenses, etc.

Europe, the champion in astrometry

Gaia is a complex 2 ton satellite built by Astrium (currently Airbus Defence & Space). It was successfully launched on 19 December 2013 by a Soyuz rocket from the Guiana Space Centre. During the first five months of 2014, the ESA will check that the optoelectronic instrument (mirrors, onboard software, etc.) on the Gaia observatory is working properly. The Liège SME Amos supplied Astrium with two of the four mirrors on each telescope. During the final quarter of 2012, Gaia’s hypersensitive twin telescopes were placed in the Focal 6.5 simulator at CSL so they could undergo thermal tests in vacuum, have their performance calibrated and receive their final qualification. If the tests in orbit go well, the astrometric observatory will be declared operational in May-June 2014 and will begin to scan the entire canopy of heaven. The data will then be made available to the community of astronomers and astrophysicists.

Gaia : New technology to see the Milky Way Our Galaxy is made up of a hundred billion stars. To truly understand its evolution we need to know exactly where we stand in this mass of constantly moving and changing celestial objects. To do this, Astrometry, the science of measuring the position, distance and movement of stars around us, is just about to take a giant leap forward with the launch of ESA's new space telescope, Gaia. Gaia will make it possible to measure a billion stars of our Milky way.