S'COOL: Earth Observing Satellites
Satellites carrying instruments in Earth orbit allow us to look at clouds over the entire Earth. Satellites can be in several different types of orbit, depending on what part of the Earth is of most interest. Satellites obtain information by remote sensing so that their results have to be interpreted carefully. Also, instruments must be extensively tested to calibrate what they see. Our eyes and brain together make a perfectly calibrated sensor, because we have learned through years of experience of looking at clouds. An instrument in space, on the other hand, has no such experience. It merely reacts to the energy it receives according to the state of all its hardware at that time. If there are losses in the hardware the result we get will be too dim (like a computer screen that needs to be brightened). Calibration tells us how much we need to brighten the measurements in order to reproduce what was really there.There is a nice website about satellites at the Tech Museum of Innovation.
Further reading on satellites can be found at http://oea.larc.nasa.gov/PAIS/Satellites.html.
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