Satellite reveals new views of earth at night

December 5, 2012
This image of the continental United States at night is a composite assembled from data acquired by the Suomi NPP satellite in April and October 2012. The image was made possible by the satellite's "day-night band" of the Visible Infrared Imaging Radiometer Suite (VIIRS), which detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe dim signals such as city lights, gas flares, auroras, wildfires and reflected moonlight. Credit: NASA Earth Observatory/NOAA NGDC

(—Scientists unveiled today an unprecedented new look at our planet at night. A global composite image, constructed using cloud-free night images from a new NASA and National Oceanic and Atmospheric Administration (NOAA) satellite, shows the glow of natural and human-built phenomena across the planet in greater detail than ever before.

Many satellites are equipped to look at Earth during the day, when they can observe our planet fully illuminated by the sun. With a new sensor onboard the NASA-NOAA Suomi National Polar-orbiting Partnership (NPP) satellite launched last year, scientists now can observe Earth's atmosphere and surface during nighttime hours.

The new sensor, the day-night band of the Visible Radiometer Suite (VIIRS), is sensitive enough to detect the nocturnal glow produced by Earth's atmosphere and the light from a single ship in the sea. Satellites in the U.S. Defense have been making observations with low- for 40 years. But the VIIRS day-night band can better detect and resolve Earth's night lights.

The new, higher resolution composite image of Earth at night was released at a news conference at the meeting in San Francisco. This and other VIIRS day-night band images are providing researchers with valuable data for a wide variety of previously unseen or poorly seen events.

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This new global view and animation of Earth’s city lights is a composite assembled from data acquired by the Suomi NPP satellite. The data was acquired over nine days in April 2012 and 13 days in October 2012. It took 312 orbits to get a clear shot of every parcel of Earth's land surface and islands. This new data was then mapped over existing Blue Marble imagery of Earth to provide a realistic view of the planet. Credit: NASA Earth Observatory/NOAA NGDC

"For all the reasons that we need to see Earth during the day, we also need to see Earth at night," said Steve Miller, a researcher at NOAA's Colorado State University Cooperative Institute for Research in the Atmosphere. "Unlike humans, the Earth never sleeps."

The day-night band observed Hurricane Sandy, illuminated by moonlight, making landfall over New Jersey on the evening of Oct. 29. Night images showed the widespread that left millions in darkness in the wake of the storm. With its night view, VIIRS is able to detect a more complete view of storms and other weather conditions, such as fog, that are difficult to discern with infrared, or thermal, sensors. Night is also when many types of clouds begin to form.

Composite map of the world assembled from data acquired by the Suomi NPP satellite in April and October 2012. Credit: NASA Earth Observatory/NOAA NGDC

"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 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- band images from Suomi NPP have impressed the scientific community and exceeded our pre-launch expectations," said James Gleason, Suomi NPP project scientist at 's Goddard Space Flight Center in Greenbelt, Md.

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2.3 / 5 (3) Dec 05, 2012
Why are we wasting so much energy at night?

I get pissed off from all the man-made light at night, because you can't even go outside with binoculars or a telescope and look at the stars.

They've installed street lights where I live, even though I'm in a rural area, and it's stupid to have a thousand watt light every hundred yards in the middle of nowhere, when anyone driving down the street has headlights anyway. Figure that per mile of street and it's like 17,000 watts per mile, or 204 kilowatt-hours per mile per night. ya think that's a big enough waste of money and energy?

Maybe we should find an more efficient way to waste things?!

It's ridiculous.
not rated yet Dec 06, 2012
The light smog makes most trouble for scientists, like the astronomers. The observations at large telescopes can be ruined even with lights of single car.

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