INTRODUCTION TO SATELLITE

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 :

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.

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

Layer Of Atmosphere :
 TROPOSPHERE :
STRATOSPHERE :
MESOSPHERE :
THERMOSPHERE :
EXOSPHERE :

INFORMA
TION
SOURCE
Uses of
informa
tion
TRANN
SMITT
ER
Receiv
erChannel
1 2 3 4
1= Message signal.
2 = tranmitted signal.
3 = received signal.
4 = message signal.
Generalized communication
system :
NOISE OCCUR

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.

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.

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

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.

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.

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.

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

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.

TYPES OF ORBITS
Low-Earth-Orbit (LEOs)
Medium-Earth-Orbit (MEOs)
Geostationary (GEOs)

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.)

Little LEOs Applications
 0.8 GHz range
 Small, low-cost
 Used for short
communications.

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.

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

The Global Positioning
System :
EQUATORIAL ORBIT :
POLAR CIRCULAR
ORBIT :
EACH SATELLITE COVER 40%
AREA
SATELLITE MAKES AN ANGLE
OF 120 WITH EACH OTHER.

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.

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.

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

INTRODUCTION TO SATELLITE

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INTRODUCTION TO SATELLITE