Satellite Communications (Satcom)
Reliable worldwide communications can also be achieved through use of the INMARSAT marine satellite system. This network functions as a joint effort by in ternational communication companies utilizing a series of satellites providing coverage in the major shipping areas of the world. Each participating nation or company maintains earth stations that link their particular normal telephone network with the satellite being used. In the United States, Comsat General is the prime operator.
The system utilizes a total of six satellites in geosynchronous orbits.
The satellites cover the Atlantic, Pacific, and Indian oceans with one primary satellite and 1 backup satellite per area. The system provides 339 channels to the user transmitting between 1636.5 MHz and 1645.0 MHz and receiving on frequencies between 1535.0 and 1543.5 MHz. The system is capable of communications by voice, data (coded information relayed over voice communication lines), and telex.
The users select the satellite to be used by the area they are located in.
Once the satellite is selected, the position of the user is entered into the satcom unit so the parabolic antenna can be oriented to the selected satellite. The user can select any earth station or system desired, depending on where the communication link is required.
Satcom is a very reliable and easy system to use. The communications are very clear and comparable to land line reception. Of all the systems integrated into land communication networks, satcom is the most expensive to use.
