Much of the information contained in this image came from a single
remote-sensing device-NASA’s Moderate Resolution Imaging Spectroradiometer, or
MODIS. Flying over 700 km above the Earth onboard the Terra satellite, MODIS
provides an integrated tool for observing a variety of terrestrial, oceanic, and
atmospheric features of the Earth. The land and coastal ocean portions of these
images are based on surface observations collected from June through September
2001 and combined, or composited, every eight days to compensate for clouds that
might block the sensor’s view of the surface on any single day. Two different
types of ocean data were used in these images: shallow water true color data,
and global ocean color (or chlorophyll) data. Topographic shading is based on
the GTOPO 30 elevation dataset compiled by the U.S. Geological Survey’s EROS
Data Center. MODIS observations of polar sea ice were combined with observations
of Antarctica made by the National Oceanic and Atmospheric Administration’s
AVHRR sensor—the Advanced Very High Resolution Radiometer. The cloud image is a
composite of two days of imagery collected in visible light wavelengths and a
third day of thermal infra-red imagery over the poles. Global city lights,
derived from 9 months of observations from the Defense Meteorological Satellite
Program, are superimposed on a darkened land surface map.
