Summary communications, equipment, and theory. A PASSIVE SATELLITE is one that reflects radio signals back to earth. An ACTIVE SATELLITE is one that amplifies the received signal and retransmits it back to earth. REPEATER is another name for an active satellite. The UP LINK is the frequency used to transmit a signal from earth to a satellite. The DOWN LINK is the frequency used to transmit an amplified signal from the satellite back to earth. ">

Custom Search
 SUMMARY Now that you have completed this chapter, a short review of what you have learned will be helpful. The following review will refresh your memory of satellite communications, equipment, and theory. A PASSIVE SATELLITE is one that reflects radio signals back to earth. An ACTIVE SATELLITE is one that amplifies the received signal and retransmits it back to earth. REPEATER is another name for an active satellite. The UP LINK is the frequency used to transmit a signal from earth to a satellite. The DOWN LINK is the frequency used to transmit an amplified signal from the satellite back to earth. A SYNCHRONOUS ORBIT is one in which the satellite moves or rotates at the same speed as the earth. An ASYNCHRONOUS ORBIT is one where the satellite does not rotate or move at the same speed as the earth. A NEAR SYNCHRONOUS ORBIT is one in which the satellite rotates close to but not exactly at the same speed as the earth. PERIGEE is the point in the orbit of a satellite closest to the earth. APOGEE is the point in the orbit of a satellite the greatest distance from the earth. The ANGLE OF INCLINATION is the angular difference between the equatorial plane of the earth and the plane of orbit of the satellite. INCLINED ORBITS are orbits where there is some amount of inclination. These include equatorial and polar orbits. An EQUATORIAL ORBIT is an orbit that occurs when the plane of a satellite coincides with the plane of the earth at the equator. A POLAR ORBIT is an orbit that has an angle of inclination of or near 90 degrees. A MEDIUM ALTITUDE ORBIT is an orbit from 2,000 to 12,000 miles above the earth. The rotation rate of the earth and satellite are quite different, and the satellite moves quickly across the sky. An ECLIPSE is when the satellite is not in view or in direct line of sight with the sun. This happens when the earth is between them. An EPHEMERIS is a table showing the precalculated position of a satellite at any given time. PROGRAMMED TRACKING uses known satellite orbital parameters to generate antenna pointing angles. AUTOMATIC TRACKING is done by the equipment comparing the direction of the antenna axis and the direction of the received signal. HAND OVER is the period of time for one earth terminal to yield control to another as a satellite moves out of its area of coverage. SATELLITE-SUN CONJUNCTION is when the satellite and sun are close together and the noise from the sun prevents or hampers communications. A SATELLITE ECLIPSE is an eclipse where the rays of the sun don't reach the satellite. This prevents recharging of the solar cells of the satellite and decreases the power to the transmitter. The ZONE OF MUTUAL VISIBILITY is where the satellite can be seen by both the up- and down-link earth terminals.