The "billion-pixel array" created by a mosaic of 106 separate electronic detectors like those used in digital cameras will allow Gaia to map a billion stars within our own Milky Way galaxy during its five-year mission set for launch in 2013, an ESA release said Wednesday.
It will be able to detect distant stars up to a million times fainter than the eye can see, the release said.
Technicians spent much of May carefully fitting together the 160 detectors, each about the size of a credit card but thinner than a human hair, on a support structure.
Working in double shifts in strict clean room conditions, they installed an average four of the detectors per day, finally completing their task in early June.
"The mounting and precise alignment of the 106 [detectors] is a key step in the assembly of the flight model focal plane assembly," Philippe Gare, ESA's Gaia payload manager, said.
Gaia will operate at nearly a million miles from the Earth, creating a three-dimensional star map that will help to reveal the composition, formation and evolution of the Milky Way.