introduction to satellite
DESCRIPTION
hiee guyes this is swapnil thaware here i uploaded slide for your knowledge if you want more detail msg me on fb or mail i will help you thanking you and slideshare.comTRANSCRIPT
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CONTENTS : What’s 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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what’s mean by sATELLITE ?
Passive Satellites Active satellitesI. Natural satellites II. artificial satellites.• A passive satellite only
reflects received signals back to earth.
• Ex.moon is a natural satellite of earth
• Active satellites are complicated structures having a processing equipment called Transponder .
• An active satellite acts as a REPEATER
A Satellite is a solid object which revolves around some body due
to the effect of gravitational forces ORa satellite is an object which has been placed into orbit by human endeavour.
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History of Satellites :
• First satellite that was used for communication purpose in INDIA was -ARYABHATTA (19 April 1975)
• The first geostationary communication satellite -SYNCOM 3(19 Aug 1963).
• Father of geostationary communication 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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INFORMATION
SOURCE
Uses of informa
tion
TRANNSMITTE
R
ReceiverChannel
1 2 3 4
1= Message signal.
2 = tranmitted signal.
3 = received signal.
4 = message signal.
Generalized communication system :
NOISE OCCUR
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What are the components of a satellite?
• Many satellites are powered by rechargeable batteries.
• Small thrusters provide attitude i.e. stabilize the satellite's position in space.
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How Satellites Work :
I. A Earth Station sends message in GHz range (Uplink).
II. Satellite Receive and retransmit signals back. (Downlink)
III. Difference between Downlink and Uplink frequency is
2 GHz.
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Why geostationary satellite are launched
36,000 km from the center of the earth?
• 1.Gravitational force= attraction between any two objects, given by
• 2.Centrifugal force=an outward-directed force that normally balances the inward-directed centripital force
There 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 its orbital period, T so,
Eqating that 2 eqn=
As we know
Then T=? and sqaring
We know:G = 6.67 x 10-11 Nm2kg-2
me = 5.97 x 1024 kgwe = 7.29 x 10-5 rad s-1
Hence, substituting the above constants into
gives:
R = 35,786 km for center of earthNear about 36,000 km.
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How do satellites stay in orbit?
Satellites stay in orbit due to the balance of two factors:
i. Velocity andii. Gravitational pull
between the Earth and the satellite.
Satellites never fall into the Earth this because Earth is round and curves.
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Satellite Frequency Bands :
There is a inverse relationship between frequency and wavelength.
• Different kinds of satellites use different frequency bands.
• L–Band: 1 to 2 GHz, • S-Band: 2 to 4 GHz• C-Band: 4 to 8 GHz• X-Band: 8 to 13 GHz• Ku-Band: 13 to 18 GHz• K-Band: 18 to 28 GHz• Ka-Band: 28 to 40 GHz
As wavelength increases (and frequency decreases), larger antennas (satellite dishes) are necessary to gather the signal.
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C-band :• C-band is the most common frequency spectrums used by today’s 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 satellite
transmissions 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 ORBITS
Low-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-Orbit (GEO)
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 40% AREA
SATELLITE MAKES AN ANGLE OF 120 WITH EACH OTHER.
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ADVANTAGES AND DISADVANTAGES OF
SATELLITE: ADVANTAGES :
DISADVANTAGES :• Make repeated
observations over a given area .
• At a time satellites observe a larger coverage
• Minimum Satellite lifetime is 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 place at perticular time)
• IT IS USED FOR TRANSMIT T.V. SIGNAL OVER LARGE DISTANCE COMMUNICATION.
• POLAR SATELLITE IS USED FOR REMOTE SENSING.
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REFERENCES :
• http://en.wikipedia.org/wiki/Geosynchronous_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