NASA just published some lovely photos of planet Earth at night, showing the many ways night images can be used for science, including seeing where people live, monitoring black-outs, viewing natural events, and even watching the Aurora lights. The images are made possible by a new sensor, the day-night band of the Visible Infrared Imaging Radiometer Suite (VIIRS), which can detect even the dim glow of a single ship in the middle of the ocean.
Scroll through to see these beautiful, interesting images and learn about the technology used to capture them.
“Nighttime light is the most interesting data that I’ve had a chance to work with. I’m always amazed at what city light images show us about human activity.” says Chris Elvidge, who leads the Earth Observation Group at NOAA’s National Geophysical Data Center, on NASA’s Flickr set titled “Black Marble”.
NASA states that Elvidge’s research group “has been approached by scientists seeking to model the distribution of carbon dioxide emissions from fossil fuels and to monitor the activity of commercial fishing fleets. Biologists have examined how urban growth has fragmented animal habitat. Elvidge even learned once of a study of dictatorships in various parts of the world and how nighttime lights had a tendency to expand in the dictator’s hometown or province.”
This image of the area near Delhi, India shows how NASA’s satellite technology has progressed and just how excellent the Visible Infrared Imaging Radiometer Suite (VIIRS) really is. “For comparison,” writes NASA, “the lower image shows the same area one night earlier, as observed by the Operational Line Scan (OLS) system on a Defense Meteorological Satellite Program (DMSP) spacecraft.”
While the OLS has been a successful sensor, it uses older technology and, as is made clear by the image, has a much lower resolution than VIIRS. VIIRS is 10 to 15 times better than OLS.
It is incredible to see exactly where we live when the maps are illuminated by our homes and street lights. Here, the Nile River Valley and Delta is aglow. Approximately 97% of Egypt’s population lives along this section of the Nile, made obvious by the sparkling lights.
“The city lights resemble a giant calla lily, just one with a kink in its stem near the city of Luxor. Some of the brightest lights occur around Cairo, but lights are abundant along the length of the river. Bright city lights also occur along the Suez Canal and around Tel Aviv. Away from the lights, however, land and water appear uniformly black. This image was acquired near the time of the new Moon, and little moonlight was available to brighten land and water surfaces,” writes NASA.
NASA notes that while city lights at night help to track where people live, it’s not the be-all-end-all method, as evidenced by this image showing the contrast between a glowing South Korea and a dark North Korea. Even though North Korea has about half the number of people that South Korea has, it has just a tiny fraction of lights.
“Worldwide, South Korea ranks 12th in electricity production, and 10th in electricity consumption, per 2011 estimates. North Korea ranks 71st in electricity production, and 73rd in electricity consumption, per 2009 estimates,” states NASA.
Not only are the satellites useful for tracking the lighted activity of humans, but it can also track the lights of natural phenomena like the aurora australis, or southern lights. Here is a night view of the aurora over Antartica’s Queen Maud Land and the Princess Ragnhild Coast.
The satellites help scientists researching the Arctic as well, taking images during the polar darkness of the autumn of 2012 so scientists could see the behavior of sea ice after summer melts.
To do this, NASA states, “Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite can see in the dark. The VIIRS “day-night band” detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe signals such as gas flares, auroras, wildfires, city lights, and reflected moonlight. The day-night band takes advantage of moonlight, airglow (the atmosphere’s self-illumination through chemical reactions), zodiacal light (sunlight scattered by interplanetary dust), and starlight from the Milky Way. By using these dim light sources, the day-night band can detect changes in clouds, snow cover, and sea ice. The VIIRS day-night band offers a unique perspective because once polar night has descended, satellite sensors relying on visible light can no longer produce photo-like images. And although passive microwave sensors can monitor sea ice through the winter, they offer much lower resolution.”
The satellites can also track occurrences like wild fires, such as these burning in Siberia, helping to track the progress of the blazes even through the night.
