The advanced low light band of the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite is providing some really beautiful and informative new Earth imaging opportunities. This “day-night” band detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe various types of dim light. One important application of this technology is the observation of winter polar phenomena. A couple of interesting examples have been published this year by the NASA Earth Observatory.
Sea ice development
Following the record breaking low Arctic sea ice during the summer of 2012, scientists are now particularly interested in following the redevelopment of Arctic ice during the 2012/2013 winter. This is challenging, though, because winter in the Arctic comes with darkness. Fortunately, the VIIRS day-night band can take advantage of low light sources, including moonlight, glow from chemical reactions in the atmosphere, light scattered by interplanetary dust, and starlight, to provide relatively high resolution (0.74-km pixel) images during Arctic winter. Steve Miller of the Cooperative Institute for Research in the Atmosphere at Colorado State University notes, “We can observe areas where there is ice melt and reformation, where there’s clear water and ships can pass through.” Ted Scambos of the National Snow and Ice Data Center at the University of Colorado agrees, “Things start changing rapidly in the late fall: sea ice formation and snow cover extent at the highest latitudes. This lets us see rapid-growth areas in detail.”
A more ephemeral polar phenomenon has also been captured in astonishing VIIRS day-night images. The sensor is able to detect the light from aurorae, which are beautiful natural lights displays common to high latitude regions. Aurorae are caused by energetic charged particles originating in the magnetosphere colliding with gases of the upper atmosphere.