Explanation:
This remarkably complete
view of Earth at night is a composite
of cloud-free, nighttime images.
The images were collected during April and October 2012
by the Suomi-NPP satellite from polar orbit about 824 kilometers
(512 miles) above the surface using
its Visible Infrared Imaging Radiometer Suite
(VIIRS).
VIIRS offers greatly improved resolution and sensitivity compared to
past global nightlight detecting instrumentation
on DMSP satellites.
It also has advantages
compared to cameras on the International
Space Station.
While the space station passes over the same point on Earth
every two or three days, Suomi-NPP passes
over the same point twice a day at about 1:30am and 1:30pm
local time.
Easy to recognize here,
city lights identify major population centers,
tracking the effects of human activity and influence across the globe.
That makes
nighttime
images of our fair planet among the most interesting
and important
views from space.
