Eye of Gaia: Billion-pixel camera to map Milky Way

Jul 06, 2011
A total of 106 CCDs make up Gaia's focal plane. Technicians from Astrium France, the Gaia mission's prime contractor, are seen bolting and aligning the CCDs onto their support structure, at the company's facility in Toulouse. The structure (the gray plate underneath the CCDs) weighs about 20 kg and is made of silicon carbide, a material that provides remarkable thermal and mechanical stability. Gaia's CCDs are provided by e2v Technologies of Chelmsford, UK. Each CCD measures 4.7x6 cm, with a thickness of only a few tens of microns. Precisely fitted together on the support structure, the gap between adjacent CCD packages is about 1 mm. Credit: Astrium

The largest digital camera ever built for a space mission has been painstakingly mosaicked together from 106 separate electronic detectors. 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 and its neighbours over the course of its five-year mission from 2013, charting their brightness and spectral characteristics along with their three-dimensional positions and motions.

In order to detect up to a million times fainter than the eye can see, Gaia will carry 106 charge coupled devices (CCDs), advanced versions of chips 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 4.7x6 cm but thinner than a human hair.

The 0.5x1.0 m 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 1 mm gap between them. Working in double shifts in strict cleanroom conditions, they added an average four CCDs per day, finally completing their task on 1 June.

"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.

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 -110º Celsius.

Gaia's CCD support structure, like much of the rest of the spacecraft, is made of silicon carbide – a ceramic like material, extraordinarily resistant to deforming 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.

Gaia will operate at the Earth–Sun L2 Lagrange point, 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, colour and intensity and spectrometry.

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 should also sample 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.

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User comments : 15

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poof
1.3 / 5 (4) Jul 06, 2011
Why stereo? Everything at infinity is flat.
Honor
1 / 5 (1) Jul 06, 2011
well that's good cause you cant see infinity.
jbeale
5 / 5 (1) Jul 06, 2011
Gaia uses two telescopes but "stereo" is a poor choice of words; the fields of view do not overlap at any moment in time. However, the sum total of frames taken (over years!) from both angles as the spacecraft rotates are matched and combined later to determine an ensemble of star positions very accurately.
eachus
5 / 5 (1) Jul 06, 2011
The telescopes share a common focal plane, which means that you have two star fields 106.5 degrees apart overlapping on the sensor array. This means that as Gaia revolves around the sun it will get many images O(70) for the five year planned mission. The stereo effect is from rotation (with the Earth around the sun, so images will be from a baseline of over 2 AU.

The shared images from the two telescopes will help when it comes to very subtle effects--like the gravity of Jupiter and Saturn. (One set of images acts as a reference when sorting out distortions in the other image and vice-versa.) A lot of computation is required to get any useful information, but as long as you are planning ahead, might as well use it.
omatumr
1.8 / 5 (10) Jul 06, 2011
Gaia's three-dimensional star map will help to reveal the composition, formation and evolution of the Milky Way,"


That's great news!

If ESA has the money and the determination to perform honest science. That opportunity will soon vanish for ESA and other government research programs if integrity isn't restored to government-funded research/

Untrustworthy climate science is widely blamed for destroying Western economies, and the public is increasingly suspicious that government research funds will produce only more government propaganda.

See the unfolding story of IPCCs alteration of Forster & Gregorys climate results:

http://judithcurr...results/

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
Deesky
3.7 / 5 (10) Jul 06, 2011
Untrustworthy climate science is widely blamed for destroying Western economies

No, untrustworthy climate change deniers and right wing-nut shills are destroying some Western economies.
RobertKarlStonjek
1 / 5 (1) Jul 07, 2011
Does it double as a cell phone ?? ....just asking :)
lengould100
4.4 / 5 (7) Jul 07, 2011
Untrustworthy climate science is widely blamed for destroying Western economies
Talk about untrustworty, Oliver, how about your statements on this forum?
Dummy
1 / 5 (1) Jul 07, 2011
Can't wait for this one.
Pkunk_
2.3 / 5 (3) Jul 08, 2011
On another note , its nice to see the ESA doing some really great space science.
As NASA is gutted and allowed to slowly decay into yet another US coldwar relic , ESA is where the future really seems to lie for serious astronomical research.
Shootist
1 / 5 (2) Jul 13, 2011
Untrustworthy climate science is widely blamed for destroying Western economies
Talk about untrustworty, Oliver, how about your statements on this forum?


Don't play evil Sagan to Oliver's Velikovsky.
jsdarkdestruction
2.3 / 5 (3) Jul 25, 2011
Oliver is a convicted child molester too. so he's good at lying, his whole life he lied and pretended to be a respectable/honorable person while molesting all of his children multiple times each over a period of years.
poof
not rated yet Jul 31, 2011
Oliver is a convicted child molester too. so he's good at lying, his whole life he lied and pretended to be a respectable/honorable person while molesting all of his children multiple times each over a period of years.


wtf.
jsdarkdestruction
1 / 5 (1) Aug 01, 2011
If you mean wtf does that have to do with anything we are discussing, it has nothing to do with it. Just like olivers little climate change conspiracy theory he rants about on topics that dont have the slightest thing to do with climate change. He repeatdly questions acientists integrity and says they are all in on the scheme and they are all not credible (normally because neutron repulsion wasnt taken into account*rolls eyes*)So I simply follow suit and show olivers credibility is not what he tries to claim it is. If a man lies about molesting his children his whole life it should effect if you consider his unsupported data that he cant answer any questions about when asked credible. If you mean it as "wtf, thats messed up that oliver did that" then i will agree, nothing i can think of would ever excuse dr manuels treatment of his own children.
FrankHerbert
0.7 / 5 (50) Aug 01, 2011
Shootist,

Did you seriously just call Carl Sagan evil? You were being sarcastic, correct?

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