Uses of Satellites

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e.g. Hubble Space Telescope

A telescope orbiting the Earth. An astronomy satellite's vision is not clouded by the gases that make up the Earth's atmosphere, so it gives clearer pictures than telescopes on Earth.

Astronomy satellites study stellar phenomenona like black holes, quasars, and distant galaxies. These are not to be confused with space exploration satellites, which also study these phenomena - see below .

Astronomy satellites have many different applications:

• they can be used to make star maps
• they can be used to study mysterious phenomena such as black holes and quasars
• they can be used to take pictures of the planets in the solar system
• they can be used to make maps of different planetary surfaces

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e.g. Polar

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e.g. Anik E

A type of satellite used for communications on Earth by allowing radio, television, and telephone transmissions to be sent live anywhere in the world.

Before satellites, transmissions were difficult or impossible at long distances. The signals, which travel in straight lines, could not bend around the round Earth to reach a destination far away. They had to be reflected off layers in the atmosphere and mountain ranges etc. caused shadow areas.

Because communications satellites are in orbit, the signals can be sent instantaneously into space and then redirected to another satellite or directly to their destination.

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e.g. Navstar

A type of satellite that gives ships and aircraft their coordinate positions on the Earth.

Navigation satellites were developed in the 1950s, and they rely on the doppler effect to calculate the position of vessels emitting a radio signal. Navigation satellites are also widely used by the military.

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e.g. Kennan, Big Bird, Lacrosse

Reconnaissance satellites are used to spy on other countries. They provide intelligence information on the military activities of foreign countries.

These satellites can even detect missile launches or nuclear explosions in space.

Reconnaissance satellites can pick up and record radio and radar transmissions while passing over a country and they can be used as an orbital weapon by placing warheads on a low orbit satellite to be launched at a ground target.

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e.g. Radarsat

Remote sensing is observing and measuring our environment from a distance. Remote sensing satellites are usually put into space to monitor resources that are important for humans. For example, remote sensing satellites might track animal migration, locate mineral deposits, watch agricultural crops for weather damage, or see how fast the forests are being cut down.

All of these things can be done best from space because a satellite in orbit can normally take photographs of large expanses of land all over the world. Since these satellites are able to take photographs and observe areas all over the globe, the satellite is able to monitor areas in which the climate is very harsh, or which are nearly impossible tor reach by land.

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e.g. Cospas-Sarsat

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e.g. Galileo

Space exploration satellites are not really satellites at all; they are actually space probes. A satellite is defined as something that is orbiting something else (usually a planet), but space probes don't do that - instead they travel deep into the solar system. However, they are similar to orbiting satellites in design and function.

On their journeys, space probes send back detailed pictures and other data of faraway planets and other stellar phenomena. Space exploration satellites are responsible for many of astronomy's most important achievements. Jupiter's rings, for example, were discovered by a space exploration satellite.

Space exploration satellites must be built to last because it takes so long for the satellites to reach their destinations. Space exploration satellites are different from astronomy satellites (see above) because they do not operate from Earth orbit; they are actually sent out into deep space on their own.

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e.g. Meteosat