r 2 Traditional Transmission Media Satellites are launched into specific orbits to cover the parts of the earth for which coverage is desired. Control segment- - The control segment defines the frequency spectrum over which satellites operate and the types of signaling techniques used between the ground station and the satellite to control those communications. Ground segment-The ground segment is the earth station-the antenna designs and the access techniques used to enable multiple conversations to share the links up to the satellite. The ground segment of satellites contin- ues to change as new technologies are introduced. Satellite Orbits Another important factor that affects the use and application of satellites is the orbits in which they operate. As shown in Figure 2.6, there are three major orbits: geosynchronous orbit (GEO), middle earth orbit (MEO), and low earth orbit (LEO). The majority of communications satellites in use are GEOs. GEO Satellites A GEO satellite is launched to 22,300 miles (36,000 km) above the equator. A sig- nal from such a satellite must travel quite a distance; as a result, there is a delay of 0.25 seconds in each direction, SO from the time you say, "Hello, how are you?" to the time that you hear the person's response, "Fine," there is a 0.5-second delay, which results in somewhat of a stilted conversation. Many data applications, espe- Figure 2.6 Satellite orbits Satellite cially those that involve entertainment, such as games, cannot perform with a delay this great. GEO satellites have the benefit of providing the largest footprint of the satellite types. Just three GEO satellites can cover the entire world, but the delay factor in getting to that orbit inhibits its use with the continuously growing range of real- time applications that are very sensitive to delay. The fact that it is launched at such a high orbit also means that a GEO satellite requires the most power of all the satellite systems. And because the trend in satel- lites has been to deliver more data as well as i