- Gaia mission set for launch in 2013
- Will carry a billion-pixel digital camera
- Will map 1 billion stars in the Milky Way
THE LARGEST DIGITAL CAMERA ever built for a space mission has been painstakingly pieced together from 106 separate electronic detectors. The resulting “billion-pixel array” will serve as the super-sensitive ‘eye’ of the European Space Agency’s (ESA) 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 Milky Way galaxy and its neighbouring galaxies over the course of its five-year mission from 2013.
It will chart their brightnesses and spectral characteristics along with their three-dimensional positions and motions.
A key step
In order to detect distant stars up to a million times fainter than the eye can see, Gaia will carry 106 charge coupled devices (CCDs)—advanced versions of the chips found within standard digital cameras.
Developed for the mission by e2v Technologies of Chelmsford, UK, these rectangular detectors are a little smaller than a credit card, each one measuring 4.7 x 6cm but thinner than a human hair.
The 50 x 100cm mosaic has been assembled at the Toulouse facility of Gaia prime contractor, Astrium France.
Technicians spent much of May carefully fitting together each CCD package on the support structure, leaving only a 1mm gap between them. Working in double shifts in strict cleanroom conditions, they added an average four CCDs per day, finally completing their task on June 1.
“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.
A cool view
The completed array is arranged in seven rows of CCDs. The main part comprises 102 detectors dedicated to star detection, while four others will check the image quality of each telescope and the stability of the 106.5º angle between the two telescopes that Gaia will use to obtain stereo views of stars.
In order to increase the sensitivity of its detectors, the spacecraft will maintain their temperature at a chilly –110ºC. The following video shows how Gaia’s heatshield will unfurl to protect it from the Sun:
Gaia’s CCD support structure, like much of the rest of the spacecraft, is made of silicon carbide (SiC )—a ceramic-like material, extraordinarily resistant to deformation under temperature changes.
First synthesised as a diamond substitute, SiC has the advantage of low weight—the entire support structure with its detectors is only 20 kg.
Targets near and far
Scheduled for launch in 2013, Gaia’s three-dimensional star map will help to reveal the composition, formation and evolution of the Milky Way, sampling 1% of our galaxy’s stars.
Gaia will also study large numbers of other celestial bodies, from minor bodies in our own Solar System to more distant galaxies and quasars near the edge of the observable Universe.
Adapted from information issued by ESA. Images courtesy ESA / Astrium / C. Carreau.
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