Spaceborne communications increase the effectiveness of military operations. The Department of Defense
is engaged in the development of new communications techniques and systems, including some that are
space based. As the use of space continues its march forward, vital new opportunities for national defense
will continue to materialize. This will improve the survivability of our strategic communications against
nuclear and electronic attack.
More information on satellite communications can be found in Navy publication NTP 2, Navy
Satellite Operations. This publication was written to concisely explain the role of the Navy in the Defense
Communications Satellite Program. It also issues procedures for effective, coordinated use of available
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
A SYNCHRONOUS ORBIT is one in which the satellite moves or rotates at the same speed as the
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.