The true color imagery from the Suomi NPP satellite's Visible Infrared Imaging Radiometer Suite (VIIRS) instrument, used in this dataset, is like looking at a picture of Earth. However, this imagery is not photography. It uses three of the instrument's 21 channels to create photorealistic images of the planet. The images are made from combining three color channels: red, green and blue (called "RGB"). Since the VIIRS channels 5, 4 and 3 are sensitive to the red, green and blue wavelengths of light, respectively, they can be combined to create these types of images. Combining other bands, or the same ones in different combinations, results in a completely different image. These types of RGB composites are used for many applications, such as differentiating snow/ice from cloud, ash/smoke from cloud, or even the boundaries between warm and cold air masses.
The VIIRS true color images are processed at 750 meters per pixel and are available on a daily basis, with a year's worth of images on Science On a Sphere. With this true color real-time view of the Earth, the current state of vegetation and sea ice concentration can be seen. Changes over the course of the year can also be observed. The diagonal streaks that can sometimes be seen across the oceans are called sunglint, which is the result of sunlight reflecting off the ocean surface at the same angle as the field of the view of the satellite sensor.
Science On a Sphere
