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 of the Sun.

• They are highly specialized wireless receiver/transmitters that are launched by a rocket and placed in orbit around the Earth.

NEED OF SATELLITE NEED OF SATELLITE COMMUNICATIONCOMMUNICATION

In early 1960’s, the American Telephone n Telegraph In early 1960’s, the American Telephone n Telegraph Company (AT&T) released studies indicating that a few Company (AT&T) released studies indicating that a few powerful satellites of advanced design could handle more powerful satellites of advanced design could handle more traffic than the entire AT&T long-distance communication traffic than the entire AT&T long-distance communication network. The cost was also not too much with respect to network. The cost was also not too much with respect to long-distance communication network.long-distance communication network.

Satellite systems offer more flexibility then submarine Satellite systems offer more flexibility then submarine cables, buried underground cables, line-of-sight cables, buried underground cables, line-of-sight microwave radio or optical fiber systems.microwave radio or optical fiber systems.

SATELLITESATELLITE

A body which revolves A body which revolves around another body of around another body of preponderant mass and preponderant mass and which has a motion which has a motion primarily and permanently primarily and permanently determined by the force of determined by the force of attraction of that other attraction of that other body. OR body. OR a satellite is any object a satellite is any object that orbits or revolves that orbits or revolves around another object. For around another object. For example, the Moon is a example, the Moon is a satellite of Earth, and satellite of Earth, and Earth is a satellite of the Earth is a satellite of the Sun. Sun.

SATELLITE SATELLITE COMMUNICATIONCOMMUNICATION

A satellite A satellite communications system communications system uses satellites to relay uses satellites to relay radio transmissions radio transmissions between earth terminals. between earth terminals.

A telecommunications A telecommunications service provided via one service provided via one or more satellite relays or more satellite relays and their associated and their associated uplinks and downlinks. uplinks and downlinks.

UPLINK & DOWNLINK UPLINK & DOWNLINK FREQUENCIESFREQUENCIES

A typical operational link involves an active A typical operational link involves an active satellite and two or more earth terminals. One satellite and two or more earth terminals. One station transmits to the satellite on a frequency station transmits to the satellite on a frequency

called the UP-LINK frequency (6 or 14GHz). The called the UP-LINK frequency (6 or 14GHz). The satellite then amplifies the signal, converts it to satellite then amplifies the signal, converts it to the DOWN-LINK frequency (4 or 12GHz), and the DOWN-LINK frequency (4 or 12GHz), and

transmits it back to earth. The signal is next transmits it back to earth. The signal is next picked up by the receiving terminal. picked up by the receiving terminal.

SATELLITE ELEMENTSSATELLITE ELEMENTS

There are 2 parts common to all satellites, they There are 2 parts common to all satellites, they are,are,

Payload &Payload &

The busThe bus

1956 First Trans-Atlantic Telephone Cable: TAT-1 1956 First Trans-Atlantic Telephone Cable: TAT-1 1957 Sputnik: Russia launches the first earth satellite. 1957 Sputnik: Russia launches the first earth satellite. 1960 1st Successful DELTA Launch Vehicle 1960 1st Successful DELTA Launch Vehicle 1961 Formal start of TELSTAR, RELAY, and SYNCOM Programs 1961 Formal start of TELSTAR, RELAY, and SYNCOM Programs 1962 TELSTAR and RELAY launched 1962 TELSTAR and RELAY launched 1963 SYNCOM launched 1963 SYNCOM launched 1964 INTELSAT formed 1964 INTELSAT formed 1965 COMSAT's EARLY BIRD: 1965 COMSAT's EARLY BIRD: 1969 INTELSAT-III series provides global coverage 1969 INTELSAT-III series provides global coverage 1972 ANIK: 1st Domestic Communications Satellite (Canada) 1972 ANIK: 1st Domestic Communications Satellite (Canada) 1974 WESTAR: 1st U.S. Domestic Communications Satellite 1974 WESTAR: 1st U.S. Domestic Communications Satellite 1975 INTELSAT-IVA: 1st use of dual-polarization 1975 INTELSAT-IVA: 1st use of dual-polarization 1975 RCA SATCOM: 1st operational body-stabilized comm. satellite 1975 RCA SATCOM: 1st operational body-stabilized comm. satellite 1976 MARISAT: 1st mobile communications satellite 1976 MARISAT: 1st mobile communications satellite 1976 PALAPA: 3rd country (Indonesia) to launch domestic comm. satellite 1976 PALAPA: 3rd country (Indonesia) to launch domestic comm. satellite 1979 INMARSAT formed. 1979 INMARSAT formed. 1988 TAT-8: 1st Fiber-Optic Trans-Atlantic telephone 1988 TAT-8: 1st Fiber-Optic Trans-Atlantic telephone

HISTORY OF SATELLITESHISTORY OF SATELLITES

TYPES OF SATELLITETYPES OF SATELLITE

Passive Satellite.Passive Satellite.

Active Satellite.Active Satellite.

PASSIVE SATELLITEPASSIVE SATELLITE

A satellite that only reflects signals from one A satellite that only reflects signals from one Earth station to another, or from several Earth Earth station to another, or from several Earth stations to several others. ORstations to several others. OR

An Earth satellite intended to transmit radio An Earth satellite intended to transmit radio communication signals by reflection.communication signals by reflection.

ACTIVE SATELLITEACTIVE SATELLITE

A satellite carrying a station A satellite carrying a station intended to transmit or intended to transmit or retransmit radio retransmit radio communication signals. communication signals. It performs signal processing It performs signal processing functions such as functions such as amplification, regeneration, amplification, regeneration, frequency translation, and link frequency translation, and link switching, to make the signals switching, to make the signals suitable for retransmission.suitable for retransmission.Sputnik1 was the first active Sputnik1 was the first active satellite launched.satellite launched.

GEOSTATIONARY GEOSTATIONARY SATELLITESATELLITE

Geostationary satellites r satellites that orbit in a circular Geostationary satellites r satellites that orbit in a circular pattern with an angular velocity equal to that of earth. pattern with an angular velocity equal to that of earth.

they remain in a fixed position in respect to a given point they remain in a fixed position in respect to a given point on earth and available to all earth stations withi their on earth and available to all earth stations withi their shadow 100% of the time shadow 100% of the time

They require sophisticated and heavy propulsion devices They require sophisticated and heavy propulsion devices on board to keep them in a fixed orbit. on board to keep them in a fixed orbit.

Syncom I launched in feb 1963, was the first attempt Syncom I launched in feb 1963, was the first attempt then ,SyncomII, syncomIII then ,SyncomII, syncomIII

FOOTPRINTSFOOTPRINTSThe area on Earth that geo satellites The area on Earth that geo satellites can "see" is called the satellite's can "see" is called the satellite's "footprint." Here is one footprint that "footprint." Here is one footprint that covers all of Africa. A person in covers all of Africa. A person in Africa can use this satellite to Africa can use this satellite to communicate with anyone else in communicate with anyone else in Africa. Africa. We can also use satellites as a relay We can also use satellites as a relay system to send signals anywhere on system to send signals anywhere on Earth. Here you can see the Earth. Here you can see the overlapping footprints of four overlapping footprints of four different satellites. If you wanted to different satellites. If you wanted to send a signal from Africa to send a signal from Africa to Southeast Asia, you could bounce, or Southeast Asia, you could bounce, or relay, the signal using more than one relay, the signal using more than one satellite. satellite.

TYPES OF ORBITSTYPES OF ORBITS

LEOLEO

POLAR POLAR

GEOGEO

ELLIPTICALELLIPTICAL

LOW EARTH ORBITLOW EARTH ORBITWhen a satellite circles When a satellite circles close to Earth we say it's in close to Earth we say it's in Low Earth Orbit (LEO)Low Earth Orbit (LEO) Satellites in LEO are just Satellites in LEO are just 200 - 500 miles high.200 - 500 miles high. B/c they orbit so close to B/c they orbit so close to Earth, they must travel Earth, they must travel very fast so gravity won't very fast so gravity won't pull them back into the pull them back into the atmosphere. atmosphere. Satellites in LEO speed Satellites in LEO speed along at 17,000 miles per along at 17,000 miles per hour.hour. They can circle Earth in They can circle Earth in about 90 minutes.about 90 minutes.

A Low Earth Orbit is useful because its nearness to Earth.

can capture very detailed images of Earth's surface.

POLAR ORBITPOLAR ORBIT

A Polar orbit is a particular type A Polar orbit is a particular type of Low Earth Orbit. The only of Low Earth Orbit. The only difference is that a satellite in difference is that a satellite in polar orbit travels a north-south polar orbit travels a north-south direction, rather than the more direction, rather than the more common east-west direction.common east-west direction.Polar orbits are useful for Polar orbits are useful for viewing the planet's surface viewing the planet's surface weather satellites, are almost weather satellites, are almost always in polar orbit. No other always in polar orbit. No other orbit gives such thorough orbit gives such thorough coverage of Earth. coverage of Earth.

GEOSYNCHRONOUS GEOSYNCHRONOUS EQUATORIAL ORBITEQUATORIAL ORBIT

A satellite in geosychonous equatorial orbit (GEO) is located A satellite in geosychonous equatorial orbit (GEO) is located directly above the equator, exactly 22,300 miles out in space. directly above the equator, exactly 22,300 miles out in space. a satellite in GEO always stays directly over the same spot on a satellite in GEO always stays directly over the same spot on Earth. Earth.

ELLIPTICAL ORBITELLIPTICAL ORBITA satellite in elliptical orbit A satellite in elliptical orbit follows an oval-shaped path. follows an oval-shaped path. One part of the orbit is closest One part of the orbit is closest to the center of Earth (perigee) to the center of Earth (perigee) and the other part is farthest and the other part is farthest away (apogee).away (apogee). A satellite in this orbit takes A satellite in this orbit takes about 12 hours to circle the about 12 hours to circle the planet. planet. Like polar orbits, elliptical Like polar orbits, elliptical orbits move in a north-south orbits move in a north-south directiondirection