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| Remote Sensing |
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| The cameras used on Landsat satellites are extremely complex. They use a process called remote sensing, in which the cameras scan the earth to look for different patterns of radiation. The Landsat cameras view the earth both in visible light, and also in infrared
radiations. A single Landsat picture taken from a height of about 900 km shows a ground area of some 35,000 square kilometers. Landsat pictures are converted into a stream of electrical pulses and beamed down from the satellites to earth. By studying these false color
pictures the scientists are able to make many interesting observations. They
have been used for many applications to assist oceanographers, geologists,
foresters, etc. They enable observers to follow the movement of the ice-caps
near the poles and of the sand dunes of the desert. The flow of water in the
rivers and oceans may also be observed. |
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| Remote sensing satellites use Sun-synchronous
orbits. The data collected by remote sensing satellites has been used for
many practical purposes. They are useful in showing areas of diseased and
healthy vegetation. Healthy plants appear red. Young plants show bright red
while those ready for harvesting appear dark red. Plants affected by drought and disease can be identified by the different color of their images compared with the dark red of healthy vegetation. A number of Seasat Satellites are also launched to examine the resources of oceans and the properties of major river estuaries (a wide tidal mouth of a river). Satellite photographs are also useful to the environmental scientists enabling major sources of pollution in both the air and water to be absorbed. Deep, clear water appears perfectly black but polluted water shows as faint grey-green haze in the image. The most significant feature of this technology is that it makes possible the repetitive surveys of vast areas in a very short time even if the areas are inaccessible. |
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