Satelite Coomm

8/13/2019 Satelite Coomm

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CONTENTS : Whats mean by satellite ?

History of Satellites :

Layer Of Atmosphere :

Generalized communication system :

What are the components of a satellite?

How Satellites Work ?

How do satellite stay in orbit ?

Why satellite are launched 36,000 Km from centre of earth ?

Types of bands :

Types of orbits :

Global position system :

Advantages And Disadvantages Of satellite :

Uses of satellite :

References :


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whats mean by sateLLIte

Passive Satellites Active satellites

I. Natural satellites

II. artificial satellites.

A passive satellite only

reflects received signals

back to earth.

Ex.moon is a natural

Active satellites are

complicated structureshaving a processing

equipment called

Transponder .

An active satellite acts as aREPEATER

A Satellite is a solid object which revolves around some body due

to the effect of gravitational forces OR

a satellite is an object which has been placed into orbit byhuman endeavour.


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History of Satellites :

First satellite that was used

for communication purpose inINDIA was -

ARYABHATTA (19 April1975)

The first geostationary

communication satellite -SYNCOM 3(19 Aug 1963).

Father of geostationarycommunication satellite is

-HAROLD ROSEN

(Aircraft engineer)

The world's first artificial satellite is the Sputnik 1

was launched in 1957


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Layer Of Atmosphere :

TROPOSPHERE

STRATOSPHERE

MESOSPHERE

THERMOSPHERE

EXOSPHERE


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What are the components ofa satellite?

Many satellites are

powered by

rechargeable batteries.

Small thrusters provide

attitude i.e. stabilizethe satellite's position

in space.


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How Satellites Work :

I. A Earth Station sendsmessage in GHz range(Uplink).

II. Satellite Receive andretransmit signalsback. (Downlink)

III. Difference betweenDownlink and Uplinkfrequency is

2GHz.


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Why geostationarysatellite are launched 36,000km from the center of theearth?

1.Gravitational force=

attraction between any twoobjects, given by

2.Centrifugal force=an

outward-directed force that

normally balances the inward-

directed centripital forceThere are two relevant

forces involved in this problem


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Equate that 2 eqn=

i.e.

The tangential

velocity of the

satellite (vs) is

related to itsorbital period, T

so,

Eqating that 2

eqn=

As we know

Then T=? and sqaring

We know:

G= 6.67 x 10-11Nm2kg-2

me= 5.97 x 1024kg

e= 7.29 x 10-5rad s-1

Hence, substituting

the above constants

into

gives:

R = 35,786 km for center of

earth

Near about 36,000 km.


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C-band : C-band is the most

common frequencyspectrums used by

todays satellite.

C-band satellite

transmissions occupy

the 4 to 8 GHz

frequency range.

C-band antenna is

approximately 2-3

meters in diameter


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Ku-band :

Ku-band satellitetransmissions occupy the 13 to

18 GHz frequency range.

Ku-band antennas can be as

small as 18 inches in diameter

These very high frequency

transmissions mean very small

wavelengths and very small

diameter receiving antennas.


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TYPES OF ORBITSLow-Earth-Orbit LEOs)Medium-Earth-Orbit MEOs)Geostationary GEOs)


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Low-Earth-Orbit LEO) Altitude (600-1000 KM)

satellite gives it a better signal

strength

Advantages:

Reduces transmission

delay

Disadvantages:

Smaller coverage area.

Shorter life span (5-8 yrs.)


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Little LEOs Applications 0.8 GHz range

Small, low-cost

Used for short

communications.


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Middle-Earth-Orbiting MEO)MEOs orbits between the altitudes

of 8,000 - 20,000 km above the earth.

MEO satellites have a larger

coverage.

These orbits are primarily reserved

for communications satellites that

cover the North and South Pole.

MEOs are placed in an elliptical (oval-shaped) orbit.


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Geosynchronous-Earth-OrbitGEO)

From the ground level the

satellite appears fixed.

GEO satellites have a 24

hour view of a

particular area.

Coverage to 40% of area Of

planet by this satellite


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The Global Positioning

System :

EQUATORIAL ORBIT :

POLAR CIRCULAR ORBIT :

INCLINED ORBIT :

EACH SATELLITE COVER 40AREASATELLITE MAKES AN ANGLEOF 120 WITH EACH OTHER.


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ADVANTAGES ANDDISADVANTAGES OF SATELLITEADVANTAGES :

DISADVANTAGES :

Make repeatedobservations over a givenarea .

At a time satellites observe alarger coverage

Minimum Satellite lifetimeis about 10-15 years.

Poor spatial resolution in

the polar regions.

Launching satellites into

orbit is costly.


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Uses of satellite: IT IS USED FOR LONG DISTANCE COMMUNICATION.

IT IS SPEEDY AND RELIABLE.

IT IS USED FOR WEATHER FORECASTING.

(study of atmosphere ,rain ,sunshine at any placeat perticular time)

IT IS USED FOR TRANSMIT T.V. SIGNAL OVER LARGE DISTANCECOMMUNICATION.

POLAR SATELLITE IS USED FOR REMOTE SENSING.


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REFERENCES : http://en.wikipedia.org/wiki/Geosynchronou

s_satellie

Geostationary Satellite(Author- Louis

E.Frenzel)

(Edition- Third)

(Publication- Tata McGraw-Hill)

http://web.mit.edu/invent/iow/rosen.html


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>>BY SWAPNIL G. THAWARE

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Satelite Coomm