Billion pixel Gaia camera starts to take shape06 Jul 2011 Another milestone in the development of Gaia, ESA's ultra-sensitive space astrometry mission, was passed on 1 June when the 106 electronic detectors of its billion pixel camera were assembled like a large mosaic for the first time.
These rectangular detectors, each measuring 6 × 4.7 cm, with a thickness of only a few tens of microns, are precisely fitted together on the CCD support structure (CSS). The gap between each CCD package is about 1 millimetre. Made of silicon carbide, a material that provides remarkable thermal and mechanical stability, the CSS weighs about 20 kg. The overall CCD mosaic, a key part of the complete focal plane assembly, measures 1 × 0.5 metres.
Over the past few weeks, technicians from the mission's prime contractor, Astrium France, have been carefully bolting and aligning each of the CCDs onto the support structure at the company's facility in Toulouse. Working in double shifts inside a Class 100 clean room, the rectangular focal plane mosaic has grown at a rate of about four CCDs per day.
"The mounting and precise alignment of the 106 CCDs is a key step in the assembly of the flight model focal plane assembly," said Philippe Garé, ESA's Gaia Payload Manager. As the two telescopes of the spinning Gaia spacecraft sweep across the sky, the images of stars in each field of view will move across the focal plane array. They will be detected first by the star mapper CCDs. Each of the two strips of seven CCDs detects star images only from its assigned telescope. The confirmed star images will then move across a block of 62 astrometric field CCDs, where they are assigned tracking 'windows' and given a precise time stamp by a rubidium atomic clock.
Finally, the star images enter the spectroscopic field where a spectrograph only allows light in the narrow band of 847 to 874 nm. The filtered light is then dispersed over 1100 pixels to detect characteristic spectral lines in this band. Subsequent analysis on the ground enables stellar velocities in the radial (line-of-sight) direction to be calculated, based on the red or blue shifts of the spectral lines. Located 1.5 million km from Earth, Gaia will operate at a temperature of minus 110°C (163.15 K). This low temperature will be maintained by passive thermal control, including the cold radiator on the focal plane assembly and a giant sunshade attached to the top of the spacecraft. "In parallel to the assembly of the CSS, Astrium is working on the cold radiator and the proximity electronics module. We are aiming to bring together all three parts of the focal plane assembly by October of this year," noted Garé. ContactPhilippe Garé Giuseppe Sarri Timo Prusti
Last Update: 06 Jul 2011
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Assembly of the Gaia CCD array (flight model) 
Gaia optical bench and telescopes 
