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Satellites
A Satellite Orbiting The Earth
Satellites are objects that goes around, or orbits, something else.e.g the earth is a satellite of the sun, and the moon is a satellite of the earth.In everyday speech, satellite usually means an un-manned artificial object that orbits the earth.The very first satellite was a shinny metal ball about 1 meter across, weighing in at 83 kg.It had four long antennae for sending radio signals from it's radio beacon.Sputnik 1 orbited the earth at heights of 100-300 km and stayed in space for six months. Then it gradually fell back to earth and burned up in our atmosphere as the first artificial shooting star. Types of orbit: Low earth orbit: The space shuttle and most other launchers take their pay-loads into low earth orbits (LEO). This is roughly circular, between 150-500 km above the earth and the usual orbit for space craft. Elliptical orbit: Many survey satellites need to be close to earth, to get a good view.If a satellite tried to orbit earth in a circular path at a low height, it would be pulled back by gravity.The lop-sided, elliptical orbit (EO) swings far away from the planet (the apogee of the orbit) and then comes in close (the perigee) for surveying. Geosynchronous orbit: Many communications satellites and navigational satellites boost to a very wide, circular orbit 36,000 km from earth.The satellite speeds along at 11,000 k/ph.But the planet below is turning, and the two speeds match. from the earth's surface, the satellite seems to stay in the same place.
There are other satellites all on display at the science museum in London!!
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