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Prepared by:

Kartik.k

07S11A1281

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An artificial satellite is a manufactured objectthat continuously orbits Earth or some other bodyin space.

Artificial satellites also have orbited the moon,the sun, asteroids, and the planets Venus, Mars,and Jupiter. Such satellites mainly gatherinformation about the bodies they orbit.

Artificial satellites differ from natural satellites,natural objects that orbit a planet. Earth's moonis a natural satellite.

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scientific research

weather

navigation Earth observing

military

communications

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In terms of altitude satellite are

classified as:

1) Low earth orbit satellite

2) Middle earth orbit satellite

3) Geostationary earth orbit satellite

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LEO:Low Earth Orbitsatellites have a small area ofcoverage. They are positioned in an orbit

approximately 3000km from the surface of the earth They complete one orbit every 90 minutes The large majority of satellites are in low earth

orbit The Iridium system utilizes LEO satellites

(780km high) The satellite in LEO orbit is visible to a point on

the earth for a very short time

MEO:Medium Earth Orbitsatellites have orbitalaltitudes between 3,000 and 30,000 km. They are commonly used in navigation systems

such as GPS

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GEO:Geosynchronous (Geostationary) Earth Orbit

satellites are positioned over the equator. Theorbital altitude is around 30,000-40,000 km

They complete one orbit every 24 hours. Thiscauses the satellite to appear stationary withrespect to a point on the earth, allowing onesatellite to provide continual coverage to a givenarea on the earth's surface

One GEO satellite can cover approximately 1/3of the worlds surface

They are commonly used in communication

system

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Geostationary orbits are primarily usedfor two functions:

Weather monitoring

Telecommunications & Broadcasting

Commercial growth is focused on:

DTH TV (Direct To Home: Sky TV)

Phone, Fax, Video, Data services

Mobile Communications

Digital Radio

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It is also possible for satellites to

communicate with other satellites

Communication can be by microwave orby optical laser

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Two stations on earth want to communicationthrough Radio broadcast but are too far away to useconventional means.

The two stations can use a satellite as a relaystation for their communication one earth stationsends transmission to the satellite. This is called a

uplink.

The satellite transponder converts the signal andsends to the second earth station. This is called a

downlink.

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Downlink The link from a satellite down to one or more

ground stations or receivers

Uplink The link from a ground station up to a satellite.

Some companies sell uplink and downlinkservices to

television stations, corporations, and to othertelecommunication carriers.

A company can specialize in providing uplinks,downlinks, or both.

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When using a satellite forlong distancecommunications, thesatellite acts as a repeater.

An earth station transmitsthe signal up to the satellite(uplink), which in turnretransmits it to the

receiving earth station(downlink).

Different frequencies areused for uplink/downlink.

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24 satellites

6 orbiting planes

55 degree inclination

20200 km above Earth

12 hours of orbit

5 hours view in horizon

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Some applications of GPS include:

Aircraft navigation

Marine navigation

Driving

SurveyingFarming

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Can reach over large geographical area

Flexible (if transparent transponders)

Easy to install new circuits

Circuit costs independent of distance

Broadcast possibilities Temporary applications (restoration)

Niche applications

Mobile applications (especially "fill-in")

Terrestrial network "by-pass" Provision of service to remote or underdeveloped areas

User has control over own network

1-for-N multipoint standby possibilities

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Large up front capital costs (space segment andlaunch)

Terrestrial break even distance expanding (now

approx. size of Europe) Interference and propagation delay

Congestion of frequencies and orbits

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Telephony

Satellite Television and radio

Amateur radio

Satellite broadband

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QUERIES????

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THANK YOU