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2. 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 :
3. what’s 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 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 OR
a satellite is an object which has been placed into orbit by
human endeavour.
4. 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
7. 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.
8. 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.
9. 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
10. 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 kg
we = 7.29 x 10-5 rad s-1
Hence, substituting
the above constants
into
gives:
R = 35,786 km for center of
earth
Near about 36,000 km.
11. How do satellites stay in orbit?
Satellites stay in orbit
due to the balance of
two factors:
i. Velocity and
ii. Gravitational pull between
the Earth and the satellite.
Satellites never fall into the
Earth this because Earth is
round and curves.
12. Satellite Frequency Bands :
There is a inverse relationshi
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.
13. 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
14. 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.
18. 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.
19. 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
20. The Global Positioning
System :
EQUATORIAL ORBIT :
POLAR CIRCULAR
ORBIT :
EACH SATELLITE COVER 40%
AREA
SATELLITE MAKES AN ANGLE
OF 120 WITH EACH OTHER.
21. 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.
22. 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.