London Shines at Night


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Billions of people will see London through a wide array of filters and lenses during the 2012 Olympic Games and Paralympic Games, but none of those views will look quite like this nighttime snapshot from the Suomi National Polar-orbiting Partnership (NPP) satellite.

The image shows London and southern Great Britain as it appeared on the night of March 27, 2012. Although most of the events in the 2012 Olympics will be held in the London area, several other cities and towns will host events, including sailing in Portland Harbour, rowing and canoeing at Eton Dorney, and cycling and mountain biking at Hadleigh Farm.

The image was acquired by the Visible Infrared Imaging Radiometer (VIIRS) on Suomi NPP, which includes a “day-night band” similar to images collected by the Operational Linescan System (OLS) flown on U.S. Defense Meteorological Satellite Program satellites.

The day-night band observes light in a range of wavelengths from green to near infrared and uses light intensification to enable the detection of dim signals, according to Chris Elvidge, who leads the Earth Observation Group at the National Oceanic and Atmospheric Administration’s National Geophysical Data Center and works on the VIIRS team.

The night views of Earth are more than just a novelty. “Nighttime lights are the least ambiguous remote sensing observation, indicating the presence and magnitude of human activities and the density of development,” said Elvidge. Seeing Earth’s night lighting has practical applications in studying human populations, economic activity, habitat fragmentation and encroachment, and energy use. “We can actually look at cities and tell you how much energy is emanating from them,” Miller added, “something pretty useful for energy consumption studies.”

Other scientists use the nighttime views to choose sites for astronomical observatories, study the impact of nocturnal lighting, and to monitor power outages and natural disasters. In meteorology, the combination of VIIRS nighttime views and thermal imaging is valuable for things like differentiating high clouds from low clouds from fog banks.

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