In order to achieve these objectives, Gaia has these goals: Determine the position, parallax and annual proper motion of 1 billion stars with an accuracy of about 20 microarcseconds (μas) at 15 mag, and 200 μas at 20 mag. Determine the positions of stars at a magnitude of V = 10 down to a precision of 7 μas—this is equivalent to measuring the position to within the diameter of a hair from 1000 km away—between 12 and 25 μas down to V = 15, and between 100 and 300 μas to V = 20, depending on the colour of the star. The distance to about 20 million stars will thus be measured with a precision of 1% or better, and about 200 million distances will be measured to better than 10%. Distances accurate to 10% will be achieved as far away as the Galactic Center, 30,000 light-years away. Measure the tangential speed of 40 million stars to a precision of better than 0.5 km/s. Derive the atmospheric parameters (effective temperature, line-of-sight interstellar extinction, surface gravity, metallicity) for all stars observed, plus some more detailed chemical abundances for targets brighter than V = 15. Measure the orbits and inclinations of a thousand extrasolar planets accurately, determining their true mass using astrometric planet detection methods. More precisely measure the bending of starlight by the Sun's gravitational field, predicted by Albert Einstein's General Theory of Relativity and first detected by Arthur Eddington during a 1919 solar eclipse, and therefore directly observe the structure of spacetime. Potential to discover Apohele asteroids with orbits that lie between Earth and the Sun, a region that is difficult for Earth-based telescopes to monitor since this region is only visible in the sky during or near the daytime. Detect up to 500,000 quasars. Spacecraft Gaia was launched by Arianespace, using a Soyuz ST-B rocket with a Fregat-MT upper stage, from the Ensemble de Lancement Soyouz at Kourou in French Guiana on 19 December 2013 at 09:12 UTC (06:12 local time). The satellite separated from the rocket's upper stage 43 minutes after launch at 09:54 UTC. The craft headed towards the Sun–Earth Lagrange point L2 located approximately 1.5 million kilometres from Earth, arriving there 8 January 2014. The L2 point provides the spacecraft with a very stable gravitational and thermal environment. There it uses a Lissajous orbit that avoids blockage of the Sun by the Earth, which would limit