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P. Cinzano, F. Falchi (Universita di Padova), C. D. Elvidge (NOAA National Geophysical Data Center)
The world-wide problem of increasing light pollution is assessed through the development of global maps of the distribution of zenith sky brightness with a resolution of approximately 1 km. These maps are produced using satellite imagery which provides photometrically calibrated data over the surface of the Earth at night, combined with a model of light scattering in the atmosphere to calculate the sky brightness from a given location. High resolution upward flux data have been obtained from the Operational Linescan System carried by the Defense Meteorological Satellite Program satellite, an oscillating scan radiometer with low-light visible and thermal infrared imaging capabilities. Light propagation in the atmosphere was computed at sea level based on the modeling technique introduced by Garstang which account for Earth curvature, double scattering and extinction. The Atlas reveals that light pollution of the night sky is not confined, as commonly believed, to developed countries, but rather appears to be a global-scale problem in the world. A correlation with a digital density population map shows that 99% of the U.S. population and two-thirds of the world population live in areas where the night sky is over the threshold to be considered polluted. Furthermore, some 70% of the population of the U.S. cannot see the Milky Way from where they live. Projections for the future show an increasingly bleak picture for preserving views of the night sky. Urgent action is needed to protect the remaining dark sites throughout the world and to take back the night sky for future generations. The International Dark-Sky Association (IDA) is supporting world-wide the battle against light pollution.
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