When out of sight of land, they used a sextant and took bearings from celestial objects to determine their position.

FORBES: DEDuced Reckoning is Assembling the Mosaic!

NASA's Kepler telescope is permanently on the lookout for celestial objects of interest, and its latest discovery is a small one.

ENGADGET: NASA's Kepler telescope spies smallest planet to date, no aliens

The idea is that Gaia's two telescopes will focus the stars on to the end of the array, and as these celestial objects then scan across the CCDs their positions and individual properties will be logged.

BBC: A billion pixels for a billion stars

Putting even the highest-resolution bacteria-based cam to shame, the new 4-inch-square CCD features an array of 10, 560 x 10, 560 pixels, and was developed in conjunction with Semiconductor Technology Associates to aid the U.S. Naval Observatory's Astrometry Department in precisely determining the position and motion of celestial objects.

ENGADGET: DALSA ships 111 megapixel CCD