SatCom systems on earth and in the sky

Different satellite communication systems and earth stations

All the satellite communication system stations on earth are the ground segments of these complex communication systems. The signals are sent to the ground stations and then, the most common next step is a connection between the stations and the end-user’s terminal using a terrestrial network.

Interestingly, there are some cases where there is no central ground station but instead the end-user’s terminal is directly connected to the satellite system which means that it is basically functioning as the ground station of the system. There are two main factors that affect the size of the earth station.

One is the amount of information being passed through them, and the other is the type of information for which the stations are being used (for example, telephone, television or data). Some ground segments send and receive information while others only receive.

The orbit of satellite communication systems

The orbit is the trip that the satellite takes around the earth. It can form different shapes. There are two specific satellite orbits that are considered most efficient and useful and so they are the orbits of choice. The one widely used with Russian satellites is an elliptical orbit inclined at an angle of 64° in relation to the equatorial plane. This orbit is particularly useful for satellite communication systems for mobile communication.

While orbiting in the ellipse, the satellite moves faster when it is closer to earth and slower when it is further away. Where the ellipse is closest to earth it is called the perigee and where it is furthest from earth it is called the apogee. The other useful orbit is the circular low earth orbit.

The altitude is several hundred kilometers and does not change. Because this orbit guarantees worldwide long-term coverage, it is the best orbit for observation satellites. During the hours when the communications satellite needs to be in use, it must be visible to the region which will be using it.

This amount of time can vary from a few hours a day to full 24-hour periods. When the period of function of the satellite communication system is not continuous, it is best that the hours are repeated at the same time every day.

The orbit of satellites is an extremely complex topic and is affected by many different factors, including the shape of the earth’s surface.