Abstract:
The NASA Blue Marble features a series of consistently processed datasets
(land, sea ice and clouds)from TERRA Moderate Resolution Imaging
Spectroradiometer (MODIS) and related datasets (topography, land cover, city
lights), all at the 1km resolution. They all originate from processing of this
sensor's data through the years 2000-2001 and originate in the final version
from January 2002.
... 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.
This layer is in the Lambert Azimuthal Equal Area projection.
[From: http://earthobservatory.nasa.gov/Newsroom/BlueMarble/ ] 
