A European probe that will map more than a billion stars in 3D is set to revolutionise astronomy, according to scientists, who have announced the start of its launch countdown.
British scientists and engineers have played key roles in the design and construction of the two billion pound spacecraft, called Gaia.
The two-tonne robot is due to be blasted into orbit on a Russian Soyuz rocket from the European space port in French Guiana on December 19.
The mission, which will last five years, is designed to discover thousands of previously unknown objects, including exploding stars, planets orbiting other suns and nearby asteroids.
It will also pinpoint many millions of stars in our galaxy, the Milky Way, with unparalleled precision and aims to yield clues about mysterious dark matter and dark energy.
Gaia will operate from a stable location one-and-a-half-million kilometres from the Earth known as the L2 Lagrangian point.
Situated with the Earth between it and the Sun, the spacecraft will be perfectly placed to observe the wider universe.
As it spins slowly, two telescopes will sweep across the entire sky and simultaneously focus their light on the largest digital camera ever flown in space.
The flood of data produced by the mission will be enough to fill more than 30,000 CD ROMs.
Britain's principal Gaia investigator Professor Gerry Gilmore, from Cambridge University, said: 'The results from Gaia will revolutionise our understanding of the cosmos as never before.
'Our understanding of what's out there has been driven by looking at what we can see. We've never had a genuine opportunity to look at everything, to know what's there, and to know where they are in relation to each other.
'We don't even know how much we don't know - there are sure to be objects out there that don't even have names yet, since we don't yet realise how strange they are.
'There are literally hundreds of questions like this - why is the universe the way it is? Where did the Milky Way come from? What's it really made of? Exactly how much does it weigh? How did it get to be like it is?
British universities and companies won around £67 million worth of contracts from the European Space Agency to build key components of the spacecraft, including its camera sensors and micro-propulsion system.
A state-of-the-art processing centre at Cambridge will sift and digest massive amounts of raw data from the probe.
Dr Floor van Leeuwen, manager of Gaia data processing in the UK, said: 'The sensors on board the spacecraft will be able to detect objects so faint the human eye would have to be nearly 4,000 times more powerful to see them.
Gaia will help scientists investigating two of astronomy's greatest mysteries, Dark Matter and Dark Energy.
Dark matter is an invisible substance that glues galaxies together, yet cannot be detected other than by observing its gravitational effects.
DarkeEnergy is a strange propulsive force that appears to be hard-wired into the fabric of space itself and is causing galaxies to fly apart at an accelerating rate.
The probe will also be able to detect far-off solar systems with their own families of planets, and, closer to home, spot potentially threatening asteroids whose orbits reach out as far as Earth.