CHAPTER 25 SATELLITE COMMUNICATIONS # DEFINITIONS TERMS. Satellite. 1) A celestial body that orbits around a planet.

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1 CHAPTER 25 SATELLITE COMMUNICATIONS # DEFINITIONS TERMS 1) A celestial body that orbits around a planet. Satellite 2) Man-made satellites that orbit earth, providing a multitude of communication functions to a wide variety of consumers, including military, governmental, private and commercial subscriber. Communications Satellites 3) A satellite radio repeater which a satellite may have many. Consists of : input Bandlimiting device (BPF) input low-noise amplifier (LNA) frequency translator low level amplifier output bandpass filter Transponder 4) It consists of one or more satellite space vehicles, a ground-based station to control the operation of the system, and a user network of earth stations that provides the interface facilities for the transmission and reception of terrestrial communications traffic through the satellite system. Satellite System 5) It includes control mechanism that support the payload operation. Bus 6) The actual user information conveyed through the system. Payload Prepared By : MARY JANE R. ROGELIO 187

2 7) A type of satellite wherein it simply bounces signals from one place to another. Passive Reflector 8) A natural satellite of Earth, visible by reflection of sunlight having a slightly elliptical orbit. Moon 9) Used by passive satellites for tracking and ranging purposes. Radio Beacon Transmitters 10) Launched by Russia, the first active earth satellite in It transmitted telemetry for 21 days. Sputnik I 11) A type of satellite capable of receiving, amplifying, reshaping, regenerating and retransmitting information. Active Satellite 12) Satellite launched by U.S., it transmitted telemetry information for nearly five months. Explorer I 13) Satellite launched by NASA in 1958, a 150-pound conical-shaped satellite. It was the first artificial satellite used for relaying terrestrial communications. Score 14) The first active satellite to simultaneously receive and transmit radio signals. Telstar I 15) Launched in 1963, and was used for telephone television, facsimile and data transmission and accomplished the first successful transatlantic video transmission. Telstar II 16) Launched in February 1963, was the first attempt to place a geosynchronous satellite into orbit. Syncom I Prepared By : MARY JANE R. ROGELIO 188

3 17) It was the first commercial telecommunications satellite. It launched from Cape Kennedy in 1965 and used two transponders. Also called as Early Birds.It stands for International Telecommunications Satellite. Intelsat I 18) Domestic satellite launched by former Soviet Union in It means lighting. Molya 19) A German astronomer who discovered the laws thatgoverns satellite motion. Johannes Kepler 20) It may be simply stated as: The planets move in ellipses with the sun at one focus The line joining the sun and the planet sweeps out equal intervals of time. The square of the time of revolution of a planet divided by the cube of its mean distance from the sun gives a number that is the same for all planets. Kepler s Law 21) The point in an orbit closest to earth Perigee 22) The point in an orbit farthest from the earth. Apogee 23) It states that the square of the periodic time of orbit is proportional to the cube of the mean distance between the primary and the satellite. Harmonic Law 24) High-altitude earth-orbit satellites operating primarily in the 2-GHz to 18 GHz frequency spectrum with orbits Satellite 22,300 miles above earth s surface. Geosynchronous Satellite Prepared By : MARY JANE R. ROGELIO 189

4 Advantages of Geosynchronous Satellite: It remain almost stationary in respect to a given earth station. Available to earth within their shadows 100% of the time. No need to switch from one geosynchronous satellite to another as they orbit overhead The effects of Doppler shift are negligible Disadvantages of geosynchronous Satellite: It requires sophisticated and heavy propulsion device onboard to keep them in a fixed orbit Much longer propagation delays Requires higher transmit power and more sensitive receivers because of the longer distances and greater path loss. High precision spacemanship is required. 25) The angle between the earth s equatorial plane and the orbital plane of a satellite measured counter clockwise at the point in the orbit where it crosses the equatorial plane traveling from south to north called the ascending node. Angle of Inclination 26) The point where the polar or inclines orbit crosses the equatorial plane travelling from north to south Descending Node 27) The line joining the ascending and descending node Line of Nodes 28) It is when the satellite rotates in an orbit directl above the equator, usually in a circular path. Equatorial Orbit Prepared By : MARY JANE R. ROGELIO 190

5 29) It is when the satellite rotates in path that takes over the North and the South poles in an orbit that is close to earth and passes over and very close to both the North and South Poles. Polar Orbit 30) The noise power normalized to a 1 Hz bandwidth, or the noise power present in a 1Hz bandwidth Noise Density 31) It identifies the system parameters and is used to determine the projected carrier-to-noise ratio and energy Bit-to-noise density ratio at both the satellite and earth station receivers for a given modulation scheme. Link Budget Prepared By : MARY JANE R. ROGELIO 191