[Communications] [Relay Stations] [Footprints]


This is a communications satellite called EchoStar 3. It's used to send TV signals to homes in North America. Today, there are more than 100 communications satellites orbiting Earth.

Relay Stations

Communications satellites act as relay stations in space. People use them to bounce messages from one part of the world to another. These messages can be telephone calls, TV pictures, or even Internet connections like the one you're using now.


Communications satellites like EchoStar are in geosynchronous orbit (from geo = Earth + synchronous = moving at the same rate). That means that the satellite always stays over one spot on Earth. The area on Earth that it can "see" is called the satellite's "footprint." Here is one footprint that covers all of Africa. A person in Africa can use this satellite to communicate with anyone else in Africa.

We can also use satellites as a relay system to send signals anywhere on Earth. Here you can see the overlapping footprints of four different satellites. If you wanted to send a signal from Africa to Southeast Asia, you could bounce, or relay, the signal using more than one satellite.

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Communication Satellites