By
Muhammad Zubair Khan Qureshi
CONTENTS
1. Introduction
2. Orbit
3. Kepler’s Laws
4. Elements of Satellite Communications
5. Advantages of Satellites
6. Disadvantages of Satellites
7. Applications
9. First Satellite Launchings by Country
10. Conclusion
1.INTRODUCTION
 Satellite is a microwave repeater in the space
 There are about 750 satellites in space, most of them
are used for communication
 They are used for wide area coverage of earth’s surface
 Transmission delay is about 0.3 sec
 Transmission cost is independent of distance
Ref: [1]
MEANING OF “SATELLITE”
 The word “Satellite” is originated from the Latin word
“Satellit” – meaning an attendant, one who is
constantly hovering around and attending to a
“master” or a big man
 For our own purposes however a satellite is simply any
body that moves around another (usually much larger)
one in a mathematically predictable path called an
“Orbit”
COMPONENTS OF A SATELLITE
Ref: [3]
COMMUNICATION SATELLITE?
 A satellite is an object that orbits another large object
like planet
 A communication satellite is a station in space that is
used for telecommunication, radio and television
signals
 The first satellite with radio transmitter was sent to
space in 1957
COMMUNICATION SATELLITE
Ref: [4]
THE ORIGIN OF SATELLITE
 The concept of using object in space to reflect signals
for communication was proved by Naval Research Lab
in Washington D.C. when it use the Moon to establish
a very low data rate link between Washington and
Hawaii (in late 1940’s)
Data Rate: Number of bits that are conveyed or processed per unit of time
Ref: [5]
 Russia also started to enter the space age by
successfully launching SPUTNIK – the first spacecraft
to orbit the earth (in Oct, 1957)
THE ORIGIN OF SATELLITE (contd..)
 The American followed by launching an experimental
satellite EXPLORER in 1958
 In 1960 two satellite were deployed “ECHO” and
“COURIER”
 In 1963 – SYNCOM
 In 1965 – INTELSAT & MOLNYA – which provides
video (Television) and voice (Telephone)
WHY USE SATELLITE?
 Satellite communication is just one example of
wireless communication systems
 Familiar examples of wireless systems are all around us
 i.e; radio, television-broadcasting, mobile & cordless
telephones
 These systems rely on a network of ground-based
transmitters and receivers and for this reason they are
often referred to as “Terrestrial” systems
Terrestrial: Refers to things related to land or the planet Earth
Ref: [6]
WHY USE SATELLITE? (contd..)
 One major use of satellites familiar to everyone is
“Satellite Television Broadcasting”
Ref: [7]
WHY USE SATELLITE? (contd..)
 Other applications of satellite communications
include;
1-High Speed Internet
2-Telephony The working or use of telephones Ref: [8]
3-Networks for multinational businesses
Ref: [9]
HOW DO SATELLITES WORK?
 A Satellite is basically a self-contained communication
system with the ability to receive signals from Earth
and to retransmit those signals back with the use of a
I will discuss about “Satellite
Transponder
Transponder” in later slides
HOW DO SATELLITES WORK?
 Two stations on Earth want to communicate through
radio broadcast but are too far away to use
conventional means
 The two stations can use a satellite as a relay station for
their communication
 One Earth Station sends a transmission to the satellite
 This is called “UPLINK”
HOW DO SATELLITES WORK contd..
Ref: [10]
HOW DO SATELLITES WORK contd..
 The Satellite Transponder converts the signal and sends it
down to the second earth station.
 This is called “DOWNLINK”
 Satellite Transponder: Ref: [13]
 The series of interconnected units that form a
communications channel between the receiving and the
transmitting antennas
 Transponder (short for Transmitter-Responder)
 Also called “Brain of Satellite”
 Purpose:
 It is mainly used in satellite communication to transfer
the received signals
HOW DO SATELLITES WORK contd..
Ref: [10]
EARLY SATELLITES
 TELSTAR
 Allowed live transmission across the Atlantic
 SYNCOM
 First Geosynchronous Satellite
Ref: [11]
Geosynchronous Satellite: With an orbital period the same as the Earth's rotation period
Ref: [11]
Ref: [12]
EARLY SATELLITES (contd...)
 Top view animation of Earth satellite in a geostationary
orbit
I will discuss about “Difference
between Geosynchronous and
Geostationary Satellites” in later
slides
Difference between Geosynchronous
and Geostationary Satellites





Features of Geostationary Satellite
The orbit is circular
The orbit is in equatorial plane i.e. directly above the
equator and thus inclination is zero
The angular velocity of the satellite is equal to angular
velocity of earth
Period of revolution is equal to period of rotation of earth.
Finish one revolution around the earth in exactly one day
i.e. 23 hours, 56 Minutes and 4.1 seconds
There is ONLY one geostationary orbit.
Ref: [26]
Difference between Geosynchronous
and Geostationary Satellites






Features of a Geosynchronous Satellite
The orbit is NOT circular
The orbit is NOT in equatorial plane i.e. directly above
the equator, it’s in inclined orbit
The angular velocity of the satellite is equal to angular
velocity of earth
Period of revolution is equal to period of rotation of
earth
Finish one revolution around the earth in exactly one day
i.e. 23 hours, 56 Minutes and 4.1 seconds
There are many geosynchronous orbits
Ref: [26]
Difference between Geosynchronous
and Geostationary Satellites
Ref: [24]
Ref: [25]
2.ORBITS
Ref: [15]
o A satellite orbits the Earth in one of two
basic types of orbit
 Circular Satellite Orbit:
Distance from the Earth remains the same at all
times
Ref: [17]
v=average speed, a=average acceleration
Ref: [14]
 Elliptical Satellite Orbit:
The elliptical orbit changes the distance to the Earth
CONCEPT OF ORBITS
Ref: [16]
SATELLITE ORBITS DEFINITIONS
 Geocentre:

When satellites orbit the Earth, either in a circular or elliptical
orbit, the satellite orbit forms a plane that passes through the
centre of gravity or geocentre of the Earth
 Direction of Rotation around the Earth:
There are two ways in which a satellite orbit may be categorized:
 POSIGRADE: The rotation around the earth is said to be
posigrade when it rotates in the same direction as the rotation
of the Earth.
 RETROGRADE: The rotation around the earth is said to be
retrograde when it rotates in the opposite direction to the
rotation of the Earth
Ref: [16]
HOW SATELLITE STAYS IN ORBIT?
 A satellite stays in orbit because the gravitational pull
of the earth is balanced by the centripetal force of the
Ref: [18]
revolving satellite
Ref: [19]
HOW SATELLITE STAYS IN ORBIT?
 Centripetal Force:
 A center seeking force which means that the force is always directed
toward the center of the circle
Ref: [20]
3.ORIGIN OF PLANETRY LAWS
 Derived 3 laws based
upon his observations
of planetary motion
Sir. Johannes Kepler
KEPLER’S FIRST LAW
 “Planets move around the Sun in ellipses, with the Sun
at one focus”
Ref: [21]
KEPLER’S SECOND LAW
 “The line connecting the Sun to a planet sweeps
equal areas in equal times”
Ref: [21]
KEPLER’S THIRD LAW
 Kepler's third law quantifies the observation that more
distant orbits have longer periods. Unlike Kepler's first
and second laws that describe the motion
characteristics of a single planet, the third law makes a
comparison between the motion characteristics of
different planets.
 STATEMENT SAYS:
 “The square of the orbital period of a planet is
proportional to the cube of the mean distance from
the Sun”
Ref: [21]
KEPLER’S THIRD LAW contd…
Near Orbit
Distant Orbit
Distant Orbit 1
revolution = Near
Orbit 2
revolutions
Ref: [21]
4.ELEMENTS OF SATELLITE
COMMUNICATIONS
 The basic elements of a communication satellite
service are divided between;
1. Space Segment
2. Ground Segment
 The space segment consists of the spacecraft and
launch mechanism
 The ground segment comprises the earth station
and network control center of entire satellite system
SPACE SEGMENT
 Space segment consist of a satellite in suitable orbit
 Space segment classified on the basis of orbit
 LEO (Low Earth Orbit)
 MEO (Medium Earth Orbit)
 GEO (Geostationary or Geosynchronous Earth Orbit)
Ref: [22]
SATELLITE ORBIT ALTITUDES
Start Range=35786 km & above
35786 km
18000 km
Start Range=8000 km End Range=18000 km
8000 km
1500 km
500 km
Start Range=500 km End Range=1500 km
Ref: [22]
GROUND SEGMENT
 The ground segment of each service has distinct
characteristics
Services are;
 FSS (Fixed Service Satellite)
 Example: Point-to-Point Communication
 BSS (Broadcast Service Satellite)
 Example: Satellite Television/Radio
 Also called Direct Broadcast Service (DBS)
 MSS (Mobile Service Satellite)
 Example: Satellite Phones
LOW EARTH ORBIT (LEO)
 LEO satellites are much closer to the earth then GEO
satellites
 ORBITAL RANGE: From 500 to 1500 KM above the
earth’s surface
 LEO satellites don’t stay in fixed position relative to the
surface, and are only visible for 15 to 20 minutes each
pass
 A network of LEO satellite is necessary for LEO
satellites to be useful
ADVANTAGES OF LEO
 A LEO satellite’s communication to earth compared to
a GEO satellite gives it a better signal strength and less
of a time delay, which makes it better for POINT-TOPOINT communication
 A LEO satellite’s smaller area of coverage wastes less
bandwidth
DISADVANTAGES OF LEO
 As network of LEO satellites is needed for making it
useful, which can be costly
 LEO satellites have to compensate for Doppler shifts
cause by their relative movement
 Atmospheric drag (i.e; air-resistance) effects LEO
satellites, causing gradual orbital decay (i.e; decrease
in altitude)
The Doppler effect (or Doppler shift) is the change in frequency of a wave (or other
periodic event) for an observer moving relative to its source.
Ref: [27]
MEDIUM EARTH ORBIT (MEO)
 MEO satellites are above the LEO satellites and below




the GEO satellites
ORBITAL RANGE: Between 8000 KM and 18000 KM
above the earth’s surface
Similar to LEO satellites in functionality
MEO satellites are visible for much longer periods of
time than LEO satellites, usually between 2 to 8 hours
MEO satellites have larger coverage area then LEO
satellites
ADVANTAGES OF MEO
 A MEO satellite’s longer duration of visibility and
wider footprint means fewer satellites are needed
in a MEO network than a LEO network
DISADVANTAGES OF MEO
 A MEO satellite’s distance gives it a longer time delay
and weaker signal than a LEO satellite, though not as
bad as a GEO satellite
GEOSTATIONARY EARTH ORBIT
(GEO)
 GEO satellites are above LEO and MEO satellites
 ORBITAL RANGE: 35786 KM above the earth’s
surface
 Objects in Geostationary Orbit revolve around the
earth at the same speed as the earth rotates. This
means GEO satellites remain in the same position
relative to the surface of the earth
ADVANTAGES OF GEO
 A GEO satellite’s distance from earth gives it a large
coverage area, almost a fourth of the earth’s surface
 GEO satellites have a 24 hours view of a particular area
 These factors make it ideal for satellite broadcast
and other multipoint applications
DISADVANTAGES OF GEO
 GEO satellite’s distance also cause it to have both a
comparatively weak signal and a time delay in the
signal, which is bad for point-to-point
communication
 GEO satellites, centered above the equator, have
difficulty broadcasting signals to near polar
regions
5.ADVANTAGES OF SATELLITES
OVER TERRESTRIAL
COMMUNICATION
 The coverage area of a satellite greatly exceeds that of a
terrestrial system
 Transmission cost of a satellite is independent of the
distance from the center of the coverage area
 Satellite to Satellite communication is very precise
 Higher Bandwidths are available for use
6.DISADVANTAGES OF SATELLITE
COMMUNICATION
 Launching satellites into orbit is costly
 Satellite Bandwidth is gradually becoming used up
(i.e; weak)
 There is a larger propagation delay in satellite
communication than in terrestrial communication
MAJOR PROBLEMS FOR SATELLITES
1.
2.
3.
4.
5.
Positioning in orbit
Stability
Power
Communications
Harsh Environment
7.APPLICATIONS
Ref: [23]
APPLICATIONS contd…
 TELEPHONY:
 Fixed points -> earth station -> satellite ->
earth stations -> fixed points
 TELEVISION AND RADIO:
 e.g; Direct Broadcast Satellite (DBS) & Fixed Service
Satellite (FSS)
 MOBILE SATELLITE TECHNOLOGY:
 Special antenna called “Mobile Satellite Antenna”
 No matter where or how this antenna is mounted on
APPLICATIONS contd…
 RADIO:
 Radio Broadcast
 Low Earth Orbits
 INTERNET:
 High Speed
 Useful for far away places
 MILITARY:
 Uses Geostationary Satellites
 e.g; The Defense Satellite Communications
9.FIRST SATELLITE LAUNCHINGS BY
COUNTRY
CONCLUSION
 Every thing has advantages and disadvantages but as a
whole, satellites remain the best utilization used for
communications due to their speed and other
advantages mentioned in this presentation
Communication Satellites bring the world to you
Anywhere and Any Time
REFERENCES
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[1]- http://www.iconshock.com/networking-icons/
[2]- http://www.integ-europe.com/
[3]- http://www.gma.org/surfing/sats.html
[4]- http://www.intelsatgeneral.com/resources/satellite-basics
[5]- http://en.wikipedia.org/wiki/Bit_rate
[6]- http://en.wikipedia.org/wiki/Terrestrial
[7]- http://electronics.howstuffworks.com/satellite-tv1.htm
[8]- http://en.wikipedia.org/wiki/Telephony
[9]- http://business.hughesnet.com/business-broadband
[10]- http://www.radio-electronics.com/info/satellite/communications_satellite/communications-satellite-technology.php
[11]- http://en.wikipedia.org/wiki/Geosynchronous_satellite
[12]- http://cryptome.org/echelon-ep-fin.htm
[13]- http://en.wikipedia.org/wiki/Transponder_%28satellite_communications%29
[14]- http://www.physicsclassroom.com/calcpad/circgrav
[15]- http://blogs.discovermagazine.com/badastronomy/2012/10/16/space-leap-of-faith/#.VTuwJJP-nQJ
[16]- http://www.radio-electronics.com/info/satellite/satellite-orbits/satellites-orbit-definitions.php
[17]- http://imgarcade.com/1/elliptical-orbit-animation/
[18]- http://www.slideshare.net/gupshupcornercomm/pakistani-chat-roomschatroomgupshupcornersatellitelec1
[19]- http://quest.nasa.gov/space/teachers/rockets/principles.html
[20]- http://www.regentsprep.org/regents/physics/phys06/bcentrif/lrsmlv.gif
[21]- http://www.phy6.org/stargaze/Kep3laws.htm
[22]- http://en.wikipedia.org/wiki/List_of_orbits
[23]- https://www.viasat.com/enterprise-satellite-networks/linkstar-system
[24] - http://www.sccs.swarthmore.edu/users/05/shupe/orbits.html
[25] - http://www.mpoweruk.com/satellites.htm
[26] - http://www.gktoday.in/geostationary-and-geosynchronous-orbits/
[27] - http://en.wikipedia.org/wiki/Doppler_effect