Earth at Night
This new global view of Earth's city lights is a composite assembled from data acquired by the Suomi National Polar-orbiting Partnership (NPP) satellite. The data was acquired over nine days in April 2012 and 13 days in October 2012. It took 312 orbits to get a clear shot of every parcel of Earth's land surface and islands. This new data was then mapped over existing Blue Marble imagery of Earth to provide a realistic view of the planet.
—NASA's Earth Observatory/NOAA/DOD