Tracking the stars -- and Earth

This was a neat photo from ESA today. Pretty much every single spacecraft carries one or more "star trackers," cameras or sensors designed to provide information on the spacecraft's position and orientation based upon the observed positions of known stars. Even after millennia of technological development, we still rely upon celestial navigation! This photo comes from a new-generation star tracker of very small mass (less than half a kilogram) on an ESA spacecraft designed to test new technologies. The photo, which of course includes stars, also serendipitously contains the curve of Earth and its thin, hazy atmosphere, the bubble in which all known life breathes.

More information here. Thanks to Daniel Fischer for the link.