Nighttime Satellite Images and Hank Brandli
October 13, 2007
The photomontage above shows snow cover under the light of the full Moon over central Asia, as captured by visible sensors on the Defense Meteorological Satellite Platform (DMSP). Hank Brandli, who passed away last month, was a pioneer in analyzing DMSP images and promoting their utility. He broadened the field of satellite meteorology by incorporating satellite images taken at night, both when the Moon is full, as above, or when it's absent from the nighttime sky, thus allowing aurora, city lights, wildfires, and gas flares to be readily identifiable.
DMSP satellites observe the Earth in visible light at night as well as during the day. When the illumination source is the Sun, a solid-state detector is used, and at night, when the Moon is out, a special photomultiplier tube is used. Despite the fact that light levels under full sunlight are between five and six orders of magnitude greater than under full moonlight, features having a high albedo, like snow and ice, are bright enough to reflect light even at low levels of brightness; therefore, they're quite easy to see under moonlit skies. This is evident to anyone who has ever been outside at night when the ground is snow covered and the full Moon is high in the sky. Images acquired on March 24, 1978.