Daniel K. / Physics 338 / April 17, 1997
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Without satellites we would be lost. We wouldn't know what the weather is going to be tomorrow. We wouldn't know what the world looked like. Without satellites we wouldn't even know how to travel. Satellites really help us out in every day life and we depend on them.


In the mid-1970's, a team of scientists in America identified 25 crops growing in almost 9000 fields in California's Imperial Valley, without even being near the valley. The thing that made it possible for them to name the crops, which included lettuce and tomatoes, were pictures taken by a satellite that had passed over the valley at an altitude of 570 miles. These Earth satellites can pick out particular crops and monitor their health. They can detect pollution, such as oil slicks at the sea, and they can help geologists to find oil and minerals.


Scientists can often obtain much more information when they take pictures at a wide range of wavelengths. Landsat takes photographs of the ground at seven different wavelengths. Three are visible: blue, green, and red. The other four are infrared or near-infrared wavelength's which are invisible to the human eye. These different color bands allow scientists to tell one kind of terrain or vegetation from another. When Landsat scientists look at all color bands, they can detect a distinct "fingerprint" for each type of plant, which is brighter when viewed at some wavelengths and darker at others. Satellites using infrared photography can also help to establish the dryness of a region. The amount of water in a plant's leaves determines the amount of infrared radiation that it reflects. This help's farmers to control irrigation and to predict droughts. The birds eye view of satellite pictures can see faults in rocks that are not visible from the ground. By seeing these features, geologists can figure out where there are likely to be seams in mineral or oil deposits.


We are no longer at the mercy of unexpected weather patterns that kill hundreds of people, as our weather satellites warn us of impending disasters. Farmers and foresters benefit from satellites, as they receive reports about river flooding and forest fires. Our future itself is more secure as we need NASA's warnings about the depleting ozone layer.


Everyday, in many ways, the space program serves us and makes our lives better. For instance, satellites surrounding the globe allows the United States to link up with other countries and people in an instant. It is impossible for us now to contemplate not being able to reach relatives on a foreign continent or not seeing international news " live".


Artificial satellites are a manufactured object that continually orbits the earth or some other body in space. Most artificial satellites orbit the earth. People use them to study the universe, help forecast the weather, transfer telephone calls over the oceans, assist in the navigation of ships and aircraft's, monitor crops and other resources and observe movements of military equipment on the ground. Artificial satellites also have orbited the moon, the sun, Venus, and Mars. Such satellites mainly gather information about the bodies they orbit.


Satellites are used for both exploration and communication. Exploratory satellites are equipped with instruments to measure the density, temperature and ionization of the upper atmosphere, cosmic radiation, the number and size of micrometeorites, and the strength and direction of the geomagnetic field. Weather satellites photograph the earth regularly in visible and infrared light, and they provide data to weather stations on earth, thus enabling the forecasting of weather conditions around the world. Navigation satellites allow positions at sea to be determined with an accuracy of up to 10 m, and they also aid navigation by locating ice and mapping ocean currents. SARSAT ( Search and Rescue Satellite System) monitors distress calls from ships and aircraft by means of a network of three U.S. satellites and two belonging to the former Soviet Union.


In conclusion, now you see that satellites are extremely vital in the world. They are used in identifying crops, finding natural resources, warning us of storms and forecasting weather, communicating with other countries and the navigating of ships. We are so used to having all this technology at our fingertips that it is hard to imagine what our society would be like without it.


Meore, Jeffrey, "Satellites"- The World Book Encyclopedia Volume 17, 1997 edition

Readers Digest, How in the World, USA June 92, pg. 170-175

"Satellite, Artificial" Encarta 95 CD-ROM. Funk and Wagnalls, 1994

Students Lehigh High in Coopersburg, Pa, "Is the US Space Program Worth It's Price Tag " Science World", Feb. 25, 1994 V50 N10 Pg.13