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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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