"The use of the day-night band by the National Weather Service is growing," said Mitch Goldberg, program scientist for NOAA's Joint Polar Satellite System. For example, the NOAA Weather Service's forecast office in Monterey, Calif., is now using VIIRS day-night band images to improve monitoring and forecasting of fog and low clouds for high air traffic coastal airports like San Francisco. According to Goldberg, VIIRS images were used on Nov. 26, the Monday after Thanksgiving, to map the dense fog in the San Francisco Bay area that resulted in flight delays and cancellations.
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 pixels. Then, the day-night band reviews the amount of light in each pixel. If it is very bright, a low-gain mode prevents the pixel from oversaturating. If the pixel is very dark, the signal is amplified.
"It's like having three simultaneous low-light cameras operating at once and we pick the best of various cameras, depending on where we're looking in the scene," Miller said. The instrument can capture images on nights with or without moonlight, producing crisp views of Earth's atmosphere, land and ocean surfaces.
"The night is nowhere as dark as we might think," Miller said. And with the VIIRS day-night band helping scientists to tease out information from human and natural sources of nighttime light, "we don't have to be in the dark anymore, either."
"The remarkable day-night band images from Suomi NPP have impressed the scientific community and exceeded our pre-launch expectations," said James Gleason, Suomi NPP project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.