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Since about 1960, remote sensing techniques and space 
technology has advanced very rapidly. The National Aeronautics 
and Space Administration (NASA) Earth Resources program began in 
1963 with an extensive series of air and space-borne remote 
sensing experiments using various sensors that might have even 
tual space applications. 
-1 Systems 
A multispectral terrain photography experiment from space 
was successfully completed by the Apollo 9 mission in 1969. 
An important conclusion from this experiment was that multi- 
spectral imagery is not only helpful but virtually mandatory on 
orbital missions, because of the great variety of terrain, 
vegetation and weather conditions encountered in orbital photo 
graphy. (Lowman, 1969) 
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In an effort to provide man with an inventory of the earth’s 
natural resources, to monitor man-made and natural changes on 
the surface of the earth, and to provide information on ways to 
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protect, conserve and wisely use the resources, NASA placed into 
orbit the Earth Resources Technology Satellite (ERTS-1) on July 23, 
1972. The overview of large areas of Earth provided by ERTS 
data satisfies a world-wide need for information of a type never 
before available. 
In many countries of Asia, Africa and South America, the 
work of geoscientists is restricted by a lack of detailed topo 
graphic and geologic maps that cover the whole country. Some 
countries do have detailed maps, but because of security regu 
lations (in need of drastic revision), they are not accessible 
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to scientists. Aerial surveying for every country is above all 
a giant financial and political problem. 
ERTS-1 data provides the geoscientist with excellent infor 
mation about the whole planetary surface without any political 
boundaries and limitations. It is now possible for geoscientists 
from any part of the world to begin meaningful study of our 
planet Earth. 
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THE ERTS-1 SYSTEM AND IMAGERY 
A short description of the orbital characteristics and the 
operational parameters selected for the satellite should provide 
here the necessary background information. 
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The 891-kg. ERTS-1 spacecraft orbits the earth 14 times 
each day, viewing a strip of surface 185 km. wide, from a 
910-km.-high, sun-synchronous, near-polar orbit. In this orbit, 
it gives global coverage once every 18 days. The satellite 
passes any particular place on the earth from 80 degrees N. 
to 80 degrees S. in a south-southwesterly direction at about