Cities at night through NASA astronauts' lens on ISS

BEIJING, Aug. 5 -- Astronauts aboard the International Space Station are treated to a spectacular view of cities on Earth lit up at night. But the relative speed of the space station meant any photos taken at night were blurred. In late 2002 and early 2003, however, astronaut Don Pettit, part of Expedition 6, constructed a device called a barn-door tracker using spare parts from around the space station. This moves the camera to compensate for the movement of the Space Station relative to the Earth below, resulting in clearer images.

Since then, a few other crew members have mastered night photography. In late 2007 to early 2008, Expedition 16 Flight Engineer Dan Tani took images of cities with a longer, 400 mm lens.

City lights provide sharp boundaries that delineate the densest concentrations of people, allowing us to assess the effect of urbanisation on the Earth’s ecosystems. Transport corridors and major commercial developments jump out.
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