Toulouse, France--A 0.5 x 1.0 m mosaic detector was assembled at the facility of prime contractor Astrium France for the European Space Agency's (ESA's) Gaia space mission. The detector is part of the largest digital camera ever built for a space mission, and has been mosaicked together from 106 separate charge coupled devices (CCDs) developed for the Gaia mission by e2v Technologies (Chelmsford, England). Each of the 106 detectors is a little smaller than a credit card at 4.7 x 6 cm, but thinner than a human hair.
The resulting "billion-pixel array" will serve as the super-sensitive ‘eye’ of ESA’s Galaxy-mapping Gaia mission. While the naked human eye can see several thousand stars on a clear night, Gaia will map a billion stars within our own Milky Way Galaxy and its neighbors during its five-year mission from 2013, charting their brightness and spectral characteristics along with their three-dimensional positions and motions.
The completed mosaic is arranged in seven rows of CCDs. The main array comprises 102 detectors dedicated to star detection. Four others check the image quality of each telescope and the stability of the 106.5º angle between the two telescopes that Gaia uses to obtain stereo views of stars. In order to increase the sensitivity of its detectors, the spacecraft will maintain their temperature of minus 110ºC.
Gaia’s CCD support structure, like much of the rest of the spacecraft, is made of silicon carbide (SiC). First synthesised as a diamond substitute, SiC has the advantage of low weight: the entire support structure with its detectors weighs only 20 kg.
Gaia will operate 1.5 million kilometers behind the earth, when looking from the sun, where Earth’s orbital motion balances out gravitational forces to form a stable point in space. As the spinning Gaia’s two telescopes sweep across the sky, the images of stars in each field of view will move across the focal plane array, divided into four fields variously dedicated to star mapping, position and motion, color and intensity, and spectrometry.
SOURCE: European Space Agency; www.esa.int/export/esaSC/SEMQ9V6TLPG_index_0.html
