What do you need to map a billion stars? A billion-pixel camera certainly helps.
Scientists hope to glean more clues about the origin and evolution of the universe, and in particular our own galaxy, when a camera of this incredible scale -- fitted to the Gaia space telescope -- is launched Thursday.
Gaia, which is due to lift off from French Guyana, has been tasked with mapping the Milky Way in greater detail than ever before.
Designed and built by Astrium for the European Space Agency (ESA), the makers say the telescope is so sensitive that it could measure a person's thumbnail from the Moon, or to put it another way, detect the width of a human hair from 1,000km (620 miles) away.
The mission's aim is to build a three-dimensional picture of our galaxy, measuring precise distances to a billion stars. Even this is a small fraction of the Milky Way, as astronomers believe there are at least 100 billion stars in our galaxy.
Astrium says Gaia is also expected to log a million quasars beyond the Milky Way, and a quarter of a million objects in our own solar system, including comets and asteroids.
"It can do it with incredible accuracy. It's the biggest camera ever put into space," said Ralph Cordey, head of science and exploration at Astrium.
He said the spacecraft cost 400 million euros ($549 million) to build, but the total cost of the mission would come to 740 million euros ($1.02 billion) when the expense of the launch and running the mission for its projected five-year lifetime are included.
If successful, Gaia will add to the knowledge gained from NASA's Hubble Space Telescope, which is still in operation, and ESA's Hipparcos satellite, which gathered data until 1993.