Presentation on theme: "Introduction A satellite is an object that orbits or revolves around another object. For example, the Moon is a satellite of Earth, and Earth is a satellite."— Presentation transcript:
1IntroductionA satellite is an object that orbits or revolves around another object. For example, the Moon is a satellite of Earth, and Earth is a satellite of the Sun.They are highly specialized wireless receiver/transmitters that are launched by a rocket and placed in orbit around the Earth.
2NEED OF SATELLITE COMMUNICATION In early 1960’s, the American Telephone n Telegraph Company (AT&T) released studies indicating that a few powerful satellites of advanced design could handle more traffic than the entire AT&T long-distance communication network. The cost was also not too much with respect to long-distance communication network.Satellite systems offer more flexibility then submarine cables, buried underground cables, line-of-sight microwave radio or optical fiber systems.
3SATELLITEA body which revolves around another body of preponderant mass and which has a motion primarily and permanently determined by the force of attraction of that other body. ORa satellite is any object that orbits or revolves around another object. For example, the Moon is a satellite of Earth, and Earth is a satellite of the Sun.
4SATELLITE COMMUNICATION A satellite communications system uses satellites to relay radio transmissions between earth terminals.A telecommunications service provided via one or more satellite relays and their associated uplinks and downlinks.
5UPLINK & DOWNLINK FREQUENCIES A typical operational link involves an active satellite and two or more earth terminals. One station transmits to the satellite on a frequency called the UP-LINK frequency (6 or 14GHz). The satellite then amplifies the signal, converts it to the DOWN-LINK frequency (4 or 12GHz), and transmits it back to earth. The signal is next picked up by the receiving terminal.
6SATELLITE ELEMENTSThere are 2 parts common to all satellites, they are,Payload &The bus
7HISTORY OF SATELLITES 1956 First Trans-Atlantic Telephone Cable: TAT-1 1957 Sputnik: Russia launches the first earth satellite.1960 1st Successful DELTA Launch Vehicle1961 Formal start of TELSTAR, RELAY, and SYNCOM Programs1962 TELSTAR and RELAY launched1963 SYNCOM launched1964 INTELSAT formed1965 COMSAT's EARLY BIRD:1969 INTELSAT-III series provides global coverage1972 ANIK: 1st Domestic Communications Satellite (Canada)1974 WESTAR: 1st U.S. Domestic Communications Satellite1975 INTELSAT-IVA: 1st use of dual-polarization1975 RCA SATCOM: 1st operational body-stabilized comm. satellite1976 MARISAT: 1st mobile communications satellite1976 PALAPA: 3rd country (Indonesia) to launch domestic comm. satellite1979 INMARSAT formed.1988 TAT-8: 1st Fiber-Optic Trans-Atlantic telephone
8TYPES OF SATELLITEPassive Satellite.Active Satellite.
9PASSIVE SATELLITEA satellite that only reflects signals from one Earth station to another, or from several Earth stations to several others. ORAn Earth satellite intended to transmit radio communication signals by reflection.
10ACTIVE SATELLITEA satellite carrying a station intended to transmit or retransmit radio communication signals.It performs signal processing functions such as amplification, regeneration, frequency translation, and link switching, to make the signals suitable for retransmission.Sputnik1 was the first active satellite launched.
11GEOSTATIONARY SATELLITE Geostationary satellites r satellites that orbit in a circular pattern with an angular velocity equal to that of earth.they remain in a fixed position in respect to a given point on earth and available to all earth stations withi their shadow 100% of the timeThey require sophisticated and heavy propulsion devices on board to keep them in a fixed orbit.Syncom I launched in feb 1963, was the first attempt then ,SyncomII, syncomIII
12FOOTPRINTSThe area on Earth that geo satellites can "see" is called the satellite's "footprint." Here is one footprint that covers all of Africa. A person in Africa can use this satellite to communicate with anyone else in Africa.We can also use satellites as a relay system to send signals anywhere on Earth. Here you can see the overlapping footprints of four different satellites. If you wanted to send a signal from Africa to Southeast Asia, you could bounce, or relay, the signal using more than one satellite.
14LOW EARTH ORBITWhen a satellite circles close to Earth we say it's in Low Earth Orbit (LEO)Satellites in LEO are just miles high.B/c they orbit so close to Earth, they must travel very fast so gravity won't pull them back into the atmosphere.Satellites in LEO speed along at 17,000 miles per hour.They can circle Earth in about 90 minutes.
15A Low Earth Orbit is useful because its nearness to Earth. can capture very detailed images of Earth's surface.
16POLAR ORBITA Polar orbit is a particular type of Low Earth Orbit. The only difference is that a satellite in polar orbit travels a north-south direction, rather than the more common east-west direction.Polar orbits are useful for viewing the planet's surfaceweather satellites, are almost always in polar orbit. No other orbit gives such thorough coverage of Earth.
17GEOSYNCHRONOUS EQUATORIAL ORBIT A satellite in geosychonous equatorial orbit (GEO) is located directly above the equator, exactly 22,300 miles out in space.a satellite in GEO always stays directly over the same spot on Earth.
18ELLIPTICAL ORBITA satellite in elliptical orbit follows an oval-shaped path.One part of the orbit is closest to the center of Earth (perigee) and the other part is farthest away (apogee).A satellite in this orbit takes about 12 hours to circle the planet.Like polar orbits, elliptical orbits move in a north-south direction