Satellite Communications Glossary

Access Technique.  The access technique is the method in satellite communications by which a number of user terminals makes use of the shared bandwidth available in a channel between the Earth station and the satellite.

Aloha.  Aloha is a multiple-access technique n satellite communications by which a number of user terminals can access the shared RF channel between the Earth station and the satellite.

Angle of Inclination.  The angle of inclination of the orbit is defined as the angle of the orbital plane to the equatorial plane, which is at 0° inclination.

Antenna Subsystem.  The antenna subsystem is a critical part of the spacecraft design. If the spacecraft antenna can be very large, we do not have to worry about generating so much power on board to achieve the required power density at Earth-station antennas.

Arab Satellite Communications Organisation (ARABSAT).  The Arab Satellite Communications Organisation was set up by approximately 20 Arab states in 1976 to provide telecommunications and television links.

Ascending Node.  The ascending node of the orbit is the point where the orbit crosses the equatorial plane going from south to north.

Asia Cellular Satellite (ACeS).  ACeS is a satellite-based mobile communications servicing Asia with mobile phone communications, as well as an interface with public switched telephone networks. The ACeS system provides wireless voice, Internet access, paging services, facsimile and data transmission.

Atmospheric Absorption Loss.  In satellite communications, atmospheric Absorption loss results from the absorption of the Earth-satellite signals as they pass through the Earth's atmosphere.

Attitude and Orbit Control Subsystem (AOC).  The path of the satellite through space is called its orbit; the orientation of the satellite in space is called its attitude. Control of the orbital path is required to ensure that the satellite is in the correct location in space to provide the services required of it. Attitude control is essential on the spacecraft to prevent the satellite from tumbling in space and to ensure that the antennas remain pointed at a fixed point on the Earth’s surface. These functions are the responsibility of the Attitude and Orbit Control Subsystem.

Azimuth.  The azimuth is the angle between the line of longitude through the Earth station and the direction of the subsatellite point.

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