Figure 1-4. A satellite orbit.
LEARNING EVENT 13: PASSIVE COMMUNICATIONS SATELLITE SYSTEM
1. Passive satellite. The passive satellite system shown in Figure 1-5 on page 1-24 illustrates how the satellite
furnishes a reflecting surface at which both stations aim their highly directional antennas. It is called a passive
satellite because it merely reflects the signals; it does not receive nor does it transmit a signal for
communications purposes. As the satellite passes overhead, the radio waves bounce off the reflecting surfaces
and are effectively scattered in many directions. The resulting received signal is a very weak replica of the
transmitted signal.
2. The satellite. The satellite shown in Figure 1-6 on page 1-24 is a balloon fabricated of aluminum-vapor-
coated polyester film 0.00005 of an inch thick (about half the thickness of the cellophane wrapping on a
cigarette package). It is 100 feet in diameter, with a reflecting surface of 31,000 square feet. At the time of
launch it is folded up in the nose of a rocket. After the rocket places the nose cone into orbit, compressed gas
expands the balloon to its full size.
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