“NOAA’s National Weather Service is continuing to explore the use of the day-night band,” said Mitch Goldberg, program scientist for NOAA’s Joint Polar Satellite System, JPSS. If the pixel is very dark, the signal will be strongly amplified. If a pixel is very bright, a low-gain mode prevents the pixel from oversaturating. The day-night band goes further, however, to ensure that each pixel collects the right amount of light. Unlike a camera that captures a picture in one exposure, the day-night band produces an image by repeatedly scanning a scene and resolving it as millions of individual picture elements or pixels. “Even after 20 years, I'm always amazed at what city light images show us about human activity.” Elvidge has studied nighttime lights data since 1992, with satellite images far less precise than the news ones. “Nothing tells us more about the spread of humans across the Earth than city lights,” said NOAA’s Chris Elvidge. In the new images, the first things to capture the eye are the planet’s cities. But the “day-night band” of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on the Suomi NPP satellite is equipped with advanced technology that extends the view of Earth's atmosphere and surface into the nighttime hours.

Many of today’s satellites are equipped to look at Earth during the day, when they can observe relatively bright objects - especially those illuminated by the sun.

Earth night view from space