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CHAPTER 4
INTRODUCTION TO SATELLITE COMMUNICATIONS
LEARNING OBJECTIVES
Upon completion of this chapter you will be able to:
1. Describe the basic operation of the two types of satellites.
2. Describe the basic components of an operational satellite system.
3. Describe the function of earth terminal equipment.
4. Describe the basic signal flow of a typical shipboard receive-only system.
5. Describe the basic signal flow of a typical shipboard transceiver system.
6. Describe the advantages of satellite communications in terms of capacity, reliability,
vulnerability, and flexibility.
7. Describe the limitations of satellites in terms of power, receiver sensitivity, and availability.
HISTORY OF SATELLITE COMMUNICATIONS
The first artificial satellite was placed in orbit by the Russians in 1957. That satellite, called Sputnik,
signaled the beginning of an era.
The United States, who was behind the Russians, made an all-out effort to catch up, and launched
Score in 1958. That was the first satellite with the primary purpose of communications.
The first regular satellite communications service was used by the Navy in 1960. The moon was used
to bounce teletypewriter signals between Hawaii and Washington, D.C. During the early 1960s, the Navy
used the moon as a medium for passing messages between ships at sea and shore stations. This method of
communications proved reliable when other methods failed.
Military satellite communications technology was at a low level until 1965. At that time high quality
voice transmissions were conducted between a satellite and two earth stations. That was the stepping
stone to the Initial Defense Communications Satellite Program (IDCSP), which will be covered later in
this chapter.
Experience with satellite communications has demonstrated that satellite systems can satisfy many
military requirements. They are reliable, survivable, secure, and a cost effective method of
telecommunications. You can easily see that satellites are the ideal, if not often the only, solution to
problems of communicating with highly mobile forces. Satellites, if properly used, provide much needed
options to large, fixed-ground installations.
For the past fifty years, the Navy has used high-frequency (hf) transmissions as the principal method
of sending messages. In the 1970s, the hf spectrum was overcrowded and "free" frequencies were at a
