199 lines
7.3 KiB
Plaintext
199 lines
7.3 KiB
Plaintext
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(word processor parameters LM=8, RM=78, TM=2, BM=2)
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Taken from KeelyNet BBS (214) 324-3501
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Sponsored by Vangard Sciences
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PO BOX 1031
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Mesquite, TX 75150
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August 3, 1990
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Courtesy of NASA BBS at 205 895-0028
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A R T I F I C I A L S A T E L L I T E S
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An artificial satellite is a manmade "moon." It circles the
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Earth in space along a path called an orbit. An artificial satellite
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may be designed in almost any shape such as a ball, drum, or box.
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It does not have to be streamlined because there is little or no
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air where it travels. Most satellites measure only a few feet
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across; some, such as Echo balloons, may be 100 feet or more in
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diameter. A satellite's size and shape depend on its purpose.
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Artificial satellites stay in space for varying lengths of time.
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The lifetime of each satellite depends on its size and distance from
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Earth.
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When a satellite swings close to Earth, it runs into air which
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slows it. To stay in orbit, a satellite must maintain a certain
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speed.
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If it slows below this speed, it plunges into the atmosphere and
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burns due to friction. The gradual slowing of a satellite by air is
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called decay.
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Large, light satellites in low orbits decay rapidly. Small,
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heavy ones in high orbits decay slowly. The six inch Vanguard I
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orbits more than 400 miles above the Earth and will orbit for
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hundreds of years.
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Every satellite carries some kind of radio transmitter. One kind
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is called a radio beacon which sends signals that enable engineers
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to track the satellite.
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Another kind of transmitter sends scientific information gathered
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by the satellite's instruments. This sending of information is
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called telemetry.
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Some satellites carry equipment to receive signals. Engineers
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beam signals to these satellites to turn the instruments on and off.
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Most satellites stop functioning long before they fall to Earth.
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Their batteries go dead, or their electronic equipment breaks down.
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They become "silent" and are of no further use. Many silent
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satellites are circling the Earth.
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Artificial satellites may be classified according to their
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purpose: weather, communication, navigation, earth resource,
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scientific, or military satellites.
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Page 1
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Weather, or meteorological, satellites help scientists to
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forecast and study weather. The first of these was called TIROS.
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These satellites carry television cameras that take pictures of
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the Earth's surface showing how the clouds move through the
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atmosphere. They also show snow and ice. By studying the pictures,
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weathermen can discover and inform people of approaching weather
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conditions.
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Communication satellites make it possible to send radio messages,
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telephone calls, and television programs between distant parts of
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Earth. These satellites are classified passive or active depending
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on the way they operate.
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Passive communication satellites act as a mirror for radio waves.
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A sending station on Earth beams waves to the satellite, the waves
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bounce off the satellite, and return to Earth.
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They reach a receiving station perhaps thousands of miles from
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the sending station. Active satellites receive signals from sending
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stations, amplify them, and send them back to Earth.
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Navigation satellites help pilots and sailors find their exact
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positions in all kinds of weather. Navigators can use it to find
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their position much as they would use a star. But instead of looking
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at the satellite, they listen to its radio signals.
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Resource satellites are used to monitor Earth's natural
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resources. This series include such satellites as Landsat and
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Seasat. Scientific satellites carry a variety of instruments around
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the world.
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Some instruments measure radiation; other instruments called
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magnetometers measure the Earth's magnetic field. Satellites that
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explore the upper parts of the atmosphere by beaming radio waves
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down into the atmosphere and then measure the reflected signals are
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called topside sounders.
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Orbiting observatories are the largest and most complicated of
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the scientific satellites. The U.S. uses three types: geophysical,
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solar, and astronomical. The orbiting geophysical observatory
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explores space near Earth, and scientists use it to study how the
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Earth's magnetic field affects energy coming from the sun.
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The orbiting solar observatory studies the sun by measuring
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radiation that cannot get through the Earth's atmosphere. The
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orbiting astronomical observatory looks deep into space at stars and
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galaxies measuring rays that never reach Earth.
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The U.S. builds and launches some scientific satellites in
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cooperation with other countries. The first international satellite,
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Ariel, carried instruments built by British scientists. The topsider
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sounder, Alouette, was designed and built by Canadian engineers and
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launched by the U.S.
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Military satellites are used for communication and navigation.
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Reconnaissance satellites can photograph enemy ground forces.
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Warning satellites can guard against surprised missile attacks.
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Page 2
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They can discover a missile launch by measuring the heat of the
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missile rocket exhaust. Since 1963, the U.S. has kept Vela
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satellites in space to detect any "sneak testing" of nuclear bombs
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in space by other nations.
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----
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NASA Fact Sheet, ARTIFICIAL SATELLITES, Dec. 1984 (36F585) MSFC
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--------------------------------------------------------------------
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If you have comments or other information relating to such topics as
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this paper covers, please upload to KeelyNet or send to the Vangard
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Sciences address as listed on the first page. Thank you for your
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consideration, interest and support.
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Jerry W. Decker.........Ron Barker...........Chuck Henderson
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Vangard Sciences/KeelyNet
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--------------------------------------------------------------------
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If we can be of service, you may contact
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Jerry at (214) 324-8741 or Ron at (214) 484-3189
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--------------------------------------------------------------------
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FINIS
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Page 3
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