Differential Photometry Study of the European Light Emission to the Space

Abstract

In the comparison of light pollution between two countries, there are some difficulties because of geographical, cultural and economical differences. The trouble is even worse considering all different systems of outdoor lighting. As first step, to contrast light pollution between countries, a group of close nations have been chosen with different population densities, size, built surface, etc. As a parameter to compare the emission of each country, the NOAA’s images (DMSP Satellite, OLS “VIS” band 0.40-1.10 um) flux were used and NASA’s software World Wind were employed to solve distortion problem of the Mercator projection. This software allow to draw frontiers over countries, so it is possible to make a particular study of them. In these images all illuminated regions are saturated, so the number of counts don’t represent the flux emitted from that region, although that number is proportional to region’s area. As it is known the area of each country it is possible to calculate the density of illuminated area per person and proportion of illuminated territory. These parameters allow to compare the aspect of the country from space. This parameter is very influenced by population’s density, so it is interesting to compare it with other parameters as urban surface, population density, street lamp density. etc. In this study we show some conclusions of the possible roots of the differences found between countries’ illumination.