How do Satellites Stay up in Space?

A satellite orbiting the earth is rather like a chestnut being whirled on the end of a piece of string. The centrifugal force of its motion forces it outwards, but the earth’s gravity (or string) keeps it from moving away.

A satellite continues to circle the earth because there is no air in space to stop it moving. It will carry on orbiting for ever unless it moves near the earth and the upper atmosphere drags on the satellite and slows it down.

Satellites move in ellipses rather than circles. The nearest point to earth is called the perigee, and the farthest, the apogee.

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Satellites can be placed in orbits moving over the equator or over the Poles, or at any other angel around the earth.

How are Satellites Recovered from Space?

Although  satellites  can remain  in space orbiting  the earth  for ever, it is  useful to have  ways  of getting them back to earth unharmed so  as to recover scientific information or animals making  experimental spaceflights.

Reconnaissance satellites that take photographs of the earth’s surface can eject capsules that are able to re-enter the earth’s atmosphere with the photographs aboard. An aircraft with a special scoop chases the capsule as it descends beneath its parachute after re-entry, and captures the capsule before it falls to the ground.

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Recovering a satellite capsule

What are Satellites used for?

Satellites have many uses. Communications satellites bounce radio signals from one continent to another, making world-wide TV and telephone services possible. Scientific satellites measure conditions in space, and observe the sun, planets and stars form space.

Weather satellites send back pictures of the earth’s weather, making weather forecasting much more accurate. Other satellites aid navigation and air traffic control, and the latest earth resources satellites are able to detect the presence of oil deposits, shoals of fish, and even diseased crops at an early stage in a disease.

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1. Tiros weather satellite 2. Sputnik 1, a Russian scientific satellite that was the first satellite to orbit the earth in 1957 3. Early Bird communications satellite

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