Largest space telescope is ready to… observe.

PhysOrg has the skinny on ESA’s Gaia telescope and its quest to catalogue a billion stars:

Gaia will be able to discern objects up to 400,000 times dimmer than those visible to the naked eye. The positional accuracy of its measurements are akin to measuring the width of a human hair at a distance of 500 km.

The process will involve scanning each part of the sky an average of 70 times over its five-year mission lifetime, which means scanning the entire sky twice every 63 days, once through each of the two telescopes, making it a powerful tool for spotting time-evolving phenomena such as binary systems, supernovae, and exoplanets. Compared to Hipparcos, Gaia will be able to measure 500 times the number of stars, extending to objects 1000 times dimmer than the dimmest that Hipparcos could catalogue.

The technology that makes this possible is the largest camera ever launched into space – 940 million pixels. That is why a lot of effort before launch was on figuring out exactly how to get the huge amount of data Gaia will produce back down to Earth.