Night-time views of India and surrounding areas in 2016. Credit: NASA
The National Aeronautics and Space Administration (NASA) scientists have just released the first new global map of earth at night since 2012, providing a clear and composite view of the patterns of human settlement across the Earth.
Satellite images of Earth at night have always triggered curiosity among people and they are also an important tool for economic, social science and environmental research projects. These beautiful images show how humans have shaped the planet and lit up the darkness.
Visible Infrared Imaging Radiometer Suite (VIIRS)—the first satellite instrument to make quantitative measurements of light emissions and reflections—detects photons of light reflected from Earth's surface and atmosphere in 22 different wavelengths. It helps researchers to distinguish the intensity, types and the sources of night lights over several years.
New technology, added benefits
After a gap of five years since night-time images were released, the NASA is now equipped with more accurate night-time environmental products. The team is now automating the processing so that users get to see night-time imagery within hours of acquisition. This can help in short-term weather forecasting and disaster response.
"Thanks to VIIRS, we can now monitor short-term changes caused by disturbances in power delivery, such as conflict, storms, earthquakes and brownouts," says Earth scientist Miguel Román of NASA’s Goddard Space Flight Center in Greenbelt. "We can monitor cyclical changes driven by reoccurring human activities such as holiday lighting and seasonal migrations. We can also monitor gradual changes driven by urbanisation, out-migration, economic changes and electrification. The fact that we can track all these different aspects at the heart of what defines a city is simply mind-boggling."
The night lights images are clearer and more accurate than what the researchers from the National Oceanic and Atmospheric Administration and NASA had released in 2012.
The team examined different ways light is radiated, scattered and reflected by land, atmospheric and ocean surfaces and the main challenge encountered in nighttime satellite imaging is the varying phases of the moon, which changes the amount of light shining on Earth. Similarly, seasonal vegetation, clouds, snow and ice cover, and even faint atmospheric emissions change the way light is observed in different parts of the world.
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