The array is made up of 106 charge coupled devices (CCDs), which are an advanced type of image sensor. Made by the UK's e2v Technologies, each rectangular CCD is a little smaller than a credit card in area, although thinner than a human hair in thickness. Throughout the month of May, technicians at Astrium France precisely joined the CCDs together into a 0.5 x 1-meter (1.6 x 3.3-foot) seven-row flat mosaic. While 102 of the sensors are assigned to star detection, the other four will check the image quality and angle of the Gaia spacecraft's twin telescopes, used to obtain 3D stereoscopic images of the stars.
Along with much of the rest of the spacecraft, the array's support structure is made from ceramic-like silicon carbide. Not only is the material lightweight, but it also resists deformation caused by temperature changes. This quality will prove important, as the array will be kept at a temperature of -110C (-166F) once in use, to increase its sensitivity. The combined weight of the array and its structure is just 20 kilograms (44 lbs).
When launched in 2013, the Gaia spacecraft will end up parked at the Earth-Sun L2 Lagrange point, which is a spot 1.5 million kilometers (932,057 miles) behind the earth, when viewed from the sun. At that location, the earth's orbital motion balances out gravitational forces to form a stable point in space. The spacecraft will then spin, in order to take in the view through its telescopes. Along with mapping the location of the stars, the array will also record their color, composition and intensity.
