b. Since the surface of the passive satellite is a very good reflector, it will relay a signal of any type without
changing the characteristics of that signal. In other words, the satellite will not cause any reduction in
bandwidth of the signal.
c. The passive type of satellite offers no discrimination to frequency. However, other conditions not
associated with the satellite impose a frequency limitation.
d. The round surface of the satellite creates no directional effects. The reflected signal can be received at
any location where the satellite can be seen.
e. The spherical shape of the satellite causes the radio signals to be reflected equally in all directions from
the hemisphere facing the ground radiating antenna. Therefore, the received signal level is very weak--weaker
than the signal from most active satellites.
f. The sphere may lose its shape in a short time after launching because of possible meteoroid
bombardment of the surface. When this happens, the sign strength may change and the signal loses quality. It
is therefore believed that this type of satellite will have a relatively short useful life.
g. The ground tracking systems are very complex.
h. The Doppler effect is not a major problem because, as the passive satellite in its orbit moves toward the
ground receiver, the increase in frequency resulting from this movement exactly compensates for the decrease
in frequency as the satellite moves away from the ground transmitter. Similarly, there is a compensating action
when the satellite moves away from the receiver and toward the transmitter.
i. Except for a low-power beacon radio transmitter used in tracking, there is normally no equipment in this
type of satellite.
2. Real-time repeater system.
a. Since the type of satellite used in this system amplifies the signal, a relatively strong signal can be
received any time the satellite is in view. Very little power is required by the satellite amplifier to deliver a
relatively strong signal to the ground station because of the small power loss in LOS communication.
b. The relatively strong received signal provides an accurate aiming point for the ground tracking stations.
c. In the real-time repeater system there is no delay in message transmission.
d. The number of communication channels and, consequently, the bandwidth are limited by the
characteristics of the equipment installed in the satellite.
e. The frequency of transmission is a fixed value and cannot be varied.
1-29
SS0031
Previous Page
