Super-sensitive space camera takes shape

Gaia

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12 July 2011

The largest digital camera ever built for a space mission has recently been completed after many weeks of hard work. Made up of 106 separate electronic detectors, the resulting “billion-pixel array” will serve as the super-sensitive “eye” of ESA’s Galaxy-mapping Gaia mission.

Whereas the unaided human eye can see several thousand stars on a clear night, Gaia will study a billion stars within our own Milky Way galaxy. During a 5-year mission, starting in 2013, it will send back the best data yet about the positions and motions of these stars, as well as their brightness.

Gaia camera array

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In order to detect stars up to a million times fainter than the eye can see, Gaia will carry an array of charge coupled devices (CCDs), which are advanced versions of chips used in everyday digital cameras. Developed in the UK, these rectangular detectors are a little smaller than a credit card, each one measuring 4.7 x 6 cm, but thinner than a human hair!

The 0.5 x 1.0 metre mosaic was assembled at the Toulouse facility of Gaia’s main contractor, Astrium France. Technicians carefully fitted together each CCD, leaving only a 1 mm gap between them. Working in double shifts in strict clean-room conditions, they added an average of four CCDs per day, finally completing their task on 1 June.

The completed array is like a small tiled area, arranged in seven rows. When in orbit, the detectors will be kept at a temperature of –110ºC to increase their sensitivity. Gaia will operate 1.5 million km away, on the night side of Earth. As it spins, Gaia’s two telescopes will sweep across the sky, studying each star in detail when it moves across their field of view.