NASA has released an update of its popular Earth at Night composite imagery. The last global composite of the earth’s night lights was created in 2003. The latest release of nighttime imagery has been greatly improved through the use of the Suomi National Polar-orbiting Partnership (NPP) satellite which was launched in October of 2011. This satellite contains a low-light sensor called the Visible Infrared Imaging Radiometer Suite (VIIRS). This new technology allows the satellite to capture night lights with a six fold increase in spatial resolution and 250 times better resolution of lighting levels (dynamic range) than with previous satellite imagery captures. This means that illumination from individual street lamps and isolated fishing boats can be captured. The imagery has also captured what is known as airglow, this is the faint glow the night sky emits, meaning even in the absence of man made lights, the night sky is never completely dark.
The satellite was named for satellite meteorology pioneer Verner Suomi. NPP flies in a polar orbit at an altitude of 824 kilometers (512 miles) above the surface of the earth. The satellite circles the earth 14 times per day, and captures imagery from any given point on the earth twice per day.
The imagery captures a multitude of light sources. Particularly around dense urban areas, man made light sources dominate. Oil and gas wells burn against dark backgrounds. Natural light sources emanate from wildfires and volcano activity. Auroras create light shows in the polar regions. Moonlight and starlight reflect light off bodies of water, snow, clouds, and deserts as well as airglow.
Aside from the fascinating aspects of viewing the intensity of lights against the darkened earth, measurements of the night view of earth have other applications. Chris Elvidge, a NOAA scientists state, “Nothing tells us more about the spread of humans across the Earth than city lights.” “City lights provide a fairly straightforward means to map urban versus rural areas, and to show where major population centers are and where they are not,” says William Stefanov of the International Space Station program. The data will also be used for weather forecasting. According to Mitch Goldberg, program scientist for NOAA’s Joint Polar Satellite System, “The very high resolution from VIIRS data will take forecasting weather events at night to a much higher level.”
The data to create the view of the earth at night was pulled from the Suomi NPP satellite over nine days in April 2012 and 13 days in October 2012 and involved 312 orbits of the earth in order to capture a cloud free and clear image of every place on earth. NASA has a gallery of night light imagery for viewing and downloading. Here are some select images.
Night time lights are not just restricted to areas of high human population density. The sparsely populated area of Northwestern North Dakota is ablaze with the light from oils wells where the Bakken shale formation exists. Lights in this area come from the lights associated with oil drilling as well as burning of natural gas that has bubbled to the surface in a practice known as flaring.