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global communication satellites : eyes & ears in the sky

 Even since Sputnik 1 was launched by the USSR in 1957 the idea of satellites in the sky orbiting the earth has been an integral part of global communication development. Without satellites we would not have many of the things we take for granted now like GPS navigation, weather information, science research – astronomy, geophysics, mapping, for news transmissions and of course for their former use in the cold war as military spy technology. More recently they have been used as Internet relay stations.  The technique for staying in Earth orbit goes back to the physics of Newton. Earth’s gravity as he knew exerts a force on all objects, however the further an object is from the surface of the earth the less effect gravity has on it. If an object is traveling at a fast enough speed above the earth it will tend to follow the curvature of he earth, and providing it is high enough it will not fall from the sky but stay in Orbit. To achieve this a satellite must be at least 300 km high and be traveling at 8000 meters per second. (The ISS orbits between 330km – 435km above the Earth, the Hubble Space Telescope orbits at 559 km)To stay in a geostationary orbit, over a fixed point on the earths surface it must be directly over the equator. It must also be able to match its speed with the rotation of the earth, but be far enough away from the surface of the earth to reduce the force of gravity pulling it back. This is achieved when a satellite is approx 36,000km away from the surface of the earth then it can be slowed down to match the rotation speed of the earth.  When you can place 3 geostationary satellites in fixed positions around the earth you can relay information around the globe, and this was the beginning of the Comsats a communication satellite revolution which began in 1962 when Telstar relayed the first tv program.  ]Satellites   & COMSATS communication satellites in particular have played a huge role in connecting the world. 

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