Figure 1.

Remote imagery of artificial light at night. (a) Monthly composite satellite image of night-time light from the Visible Infrared Imaging Radiometer Suite (VIIRS) day/night band (DNB). NASA Earth Observatory image, using Suomi NPP VIIRS data provided by NOAA National Geophysical Data Center. (b) Photograph of the Iberian Peninsula at night from the International Space Station showing Spain and Portugal. Image courtesy of the Earth Science and Remote Sensing Unit, NASA Johnson Space Center (http://eol.jsc.nasa.gov).