nched and placed in a specific type of orbit around the globe. In 1945, scientist and author Arthur C. Clarke first proposed that satellites in orbit around the earth could be used for communication purposes. (The Geosynchronous Earth Orbit described below is sometimes called the Clarke orbit in honor of the author’s suggestion.) The first satellite successfully launched and implemented in space was a Russian artificial satellite, roughly the size of a basketball. This satellite, launched in the late 1950’s, simply transmitted a short Morse code signal repeatedly. Today, there are hundreds of satellites circling the globe serving many diverse purposes such as communications, weather tracking and reporting, military functions, photo and video imaging, and global positioning information. Satellites communicate with the earth by transmitting radio waves between the satellites and earth-bound reception stations. The wavelengths of the radio wave frequencies are determined by the location of the satellite in space as described below. The signals transmitted between the earth and satellites are sent and received by various sized antennas known as satellite dishes, typically located near the earth-station receivers. Signals being sent from Earth to the satellites are referred to as uplinks, whereas the signals emanating from the satellites are called downlinks. The range of coverage area on earth that the frequencies can reach is known as the satellite’s footprint. (See Figure 1 below.) Radio waves transmitted to (and from) satellites usually involve traveling over large distances which creates relatively long propagation delays since the speed of transmission is limited by the speed of light. Figure1.Three commonly used satellite frequency bands are C, Ku, and Ka, with C and Ku being the most frequently used in today’s satellite systems. C-band transmissions occupy the 4 to 8 GHz frequency range, whereas Ku...
