Topic 2 Satellite System Elements

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Topic 2
SATELLITE SYSTEM 
ELEMENTS
COURSE LEARNING OUTCOME
1. Analyze the performance of satellite and radar in communication 
system by using designated concept and formula (C4, PLO4)
2. Demonstrate continuous learning ability while engaging new 
technical knowledge on assigned essay questions (A3, PLO12) 
CONTENT OUTLINE
2.1 Understand satellite system elements
2.2 Apply the understanding of satellite system element
2.3 Understand types of earth station
2.4 Apply the understanding of earth station
2.5 Understand satellite organizations
2.6 Apply the understanding of satellite services
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SATELLITE SYSTEM 
A satellite communications system can be broadly divided into two
segments a ground segment and a space segment. The space segment
will obviously include the satellites, but it also includes the ground
facilities needed to keep the satellites operational, these being
referred to as the tracking, telemetry, and command (TT&C)
facilities. In many networks it is common practice to employ a
ground station solely for the purpose of TT&C.
The equipment carried aboard the satellite also can be classified
according to function. The payload refers to the equipment used to
provide the service for which the satellite has been launched. The
bus refers not only to the vehicle which carries the payload but also
to the various subsystems which provide the power, attitude control,
orbital control, thermal control, and command and telemetry
functions required to service the payload.
In a communications satellite, the equipment which provides the
connecting link between the satellite s transmit and receive antennas
is referred to as the transponder. The transponder forms one of the
main sections of the payload, the other being the antenna
subsystems.
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Two basic elements in satellite systems are:
Space segment
The satellites: receives, amplifies, and retransmits the signals back to 
earth. 
Earth Segment
Uplink transmitter station : transmits signals to the satellite.
Downlink receiving station: receives the signals from satellite
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SPACE SEGMENT
The subsystems present in space segment are called as space
segment subsystems. Following are the space segment subsystems:
1. Propulsion subsystem
2.Thermal control subsystem
3. Power supply subsystem
4.Telemetry, tracking and command (TT&C) subsystem
5.Attitude and orbit control subsystem
6. Payload subsystem
7.Antenna subsystem
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Space Segment Subsystems
Mechanical structural subsystem provides the framework for
mounting other subsystems of the satellite and also an interface
between the satellite and the launch vehicle.
Propulsion subsystem is used to provide the thrusts required to
impart the necessary velocity changes and transfer orbit of the
satellite, such as those required for station keeping.
Thermal control subsystem is essential to maintain the satellite
platform within its operating temperature limits for the type of
equipment on board the satellite.
The Power Subsystems consists of solar panels and backup
batteries that generate power when the satellite passes into the
Earth's shadow.
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Attitude and Orbit Control Subsystems: The attitude and orbit
control subsystem consists of small rocket thrusters that keep the
satellite in the correct orbital position and keep antennas positioning
in the right directions.
Telemetry, tracking and command (TT&C) subsystem:
Monitors the on-board equipment operations, transmits equipment
operation data to the earth control station, and receives the earth
control station's commands to perform equipment operation
adjustments.
Payload subsystem :The basic payload in the case of a
communication satellite is the transponder and antenna, which acts
as a receiver, an amplifier and a transmitter.
Antennas : used for both receiving signals from ground stations as
well as for transmitting signals towards them. There are a variety of
antennas available for use on board a satellite. The final choice
depends mainly upon the frequency of operation and required gain.
Typical antenna types used on satellites include horn antennas,
center-fed and offset-fed parabolic reflectors and lens antennas.
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BASIC BLOCK DIAGRAM 
OF SATELLITE SUBSYSTEM
The subsystems present in space segment are called as space
segment subsystems.
Following are the space segment subsystems:
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A satellite system is composed of the spacecraft (bus) and payload(s)
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Payload Subsystem
The main functions of the payload subsystem:
• To capture the signal transmitted by the earth station. Also
capture as little interference as possible.
• To amplify the received signal.
• To change the frequency of the signal from the uplink to the
down-link (e.g. 14 to 11 GHz).
• To provide the power required for down-link transmission.
Transponder
A satellite transponder is a circuit on a satellite that receives,
modulates, amplifies and re-transmits an uplinked signal.
A satellite may consist of many transponders (i.e. a communication
satellite has about 12 or more transponders) - operating on different
frequencies and providing different services.
When a waveform travels over cable or through the air, it loses
energy. An amplifier or a repeater receives a low-energy waveform
and increases its power to send it farther on its journey. The word
transponder comes from a combination of the words transmit and
respond.
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Block Diagram OfTransponder
Function at each blocks:
Receiving antenna- receive up link signal from earth station
LNA – choose and amplified uplink signal
Local oscillator – to produce LO, 2 GHz.
Mixer – combine the uplink signal and local oscillator to produce
down link signal
HPA (power amplifier) – amplified down-link signal
Retransmitting antenna– transmit down link signal to earth
station
Up linking signal and down linking signal - as carrier signal
from satellite in any information or data
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Satellite Antenna
The antenna subsystem is one of the most critical components of
the spacecraft design because of some problem such as satellite
antennas on board the spacecraft cannot be prohibitively large as
large antennas are difficult to mount.
Large antennas also cause structural problems as they need to be
folded inside the launch vehicle during the launch and orbital
injection phase and are deployed only subsequent to the satellite
reaching the desired orbit.
All satellites need a variety of antennas. These include an
omnidirectional antenna, which is an isotropic radiator, a global or
Earth coverage antenna, a zone coverage antenna and antennas that
produce spot beams.
The omnidirectional antenna is used for TT & C operations during
the phase when the satellite has been injected into its parking orbit
until it reaches its final position. Unless the high gain directional
antennas are fully deployed and oriented properly, the
omnidirectional antenna is the only practicable means of establishing
a communication channel for tracking, telemetry and command
operations.
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Satellite Antenna
The antenna parameter are following:
• Gain
• Effective isotropic radiated power (EIRP)
• Beam width
• Bandwidth
• Polarization
• Aperture
Types of satellite antenna
There is a large variety of antennas having varied features and
characteristics. Those types that are relevant to satellite applications
will be described before.
Four main types of antennas are used on spacecraft.
• Wire antennas (monopoles and dipoles).
• Horn antennas.
• Reflector antennas.
• Array antennas.
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EARTH SEGMENT
Types Of Earth Station
TRANSMIT ONLY
The Earth Station 
can transmit signalonly towards the 
satellite.
These stations is 
used in data 
collection systems.
RECEIVE ONLY
The Earth Station can 
only receive the signal 
from a satellite but not 
transmit anything 
towards the satellite.
These stations are 
mostly used in CATV 
(community antenna TV 
systems)
astro
TRANSMIT &
RECEIVED
The Earth Station 
can transmit signal 
for satellite as well as 
can receive the signal 
from the satellite.
These stations are 
used for two way 
communication like 
telephony.
Ground station
The earth segment of satellite communication system mainly consists 
of two earth stations, transmitting earth station and receiving earth 
station.
The transmitting earth station transmits the information signals to 
satellite. Whereas, the receiving earth station receives the 
information signals from satellite. Sometimes, the same earth station 
can be used for both transmitting and receiving purposes.
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Earth Station
Designing of an Earth station depends not only on the location of 
earth station but also on some other factors. The location of earth 
stations could be on land, on ships in sea and on aircraft. The 
depending factors are type of service providing, frequency bands 
utilization, transmitter, receiver and antenna characteristics., 
Some earth stations also called ground station.
A high directive and a high gain antenna is necessary at the earth 
station , because the losses over the long path is very high.
The signals power reaching back to the earth station from satellite is 
very small, therefore at receiving end a parabolic dish antenna 
provides a high gain and thus amplify the signal power. 
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Earth Station Transmitter
• The binary (digital) information enters at base band equipment 
of earth station from terrestrial network. Encoder includes error 
correction bits in order to minimize the bit error rate.
• Up converter performs the frequency conversion of modulated 
signal to higher frequency (Convert IF to RF microwave). This 
signal will be amplified by using High power amplifier. The earth 
station antenna transmits this signal.
Earth Station Receivers
• The earth station antenna receives downlink signal, a low-level 
modulated RF signal. The received signal will be having less signal 
strength. ow Noise Amplifier (LNA) is used to amplify this signal.
• RF signal can be down converted to the Intermediate Frequency 
(IF) value.
• The decoder produces an error free binary information by 
removing error correction bits and correcting the bit positions if 
any.
• This binary information is given to base band equipment for 
further processing and then delivers to terrestrial network.
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Block Diagram of Earth Station Transmitter
Block Diagram of Earth Station Receivers
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SATELLITE ORGANIZATIONS
There have three main satellite organizations such as:
• International Satellite Organizations
• Regional Satellite Organizations
• Domestic Satellite Organizations
International Satellite Organizations
Two major international satellite organizations:
1. International Telecommunications Satellite Organizations 
(INTELSAT)
2. International Maritime Satellite Organizations (INMARSAT)
Examples of various international satellite systems are New Skies 
Satellites, PanAmSaT, INTERSPUTNIK and COSPAS-SARSAT
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INTELSAT
The INTELSAT Organization was established in 1964 to handle the
myriad of technical and administrative problems associated with a
world wide telecommunication system.
The international regions served by INTELSAT are divided into :
• the Atlantic Ocean region (AOR),
• the Pacific Ocean Region (POR), and
• the Indian Ocean region (IOR).
For each region, satellites are positioned in geo-stationary orbit
above the particular Ocean, where they provide a transoceanic
telecommunication route.
In addition to providing trans oceanic routes, the INTELSAT satellites
are used for domestic services within any given country and regional
services between countries. Two such services are vista for
telephony and Intelnet for data exchange.
INTELSAT provides telecommunication services in the space
segment only. It also approves and sets standards for the earth
station terminals
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Regional Satellite Organizations
To deliver telecommunications and broadcasting services to a 
number of countries in a region for meeting their domestic and 
regional telecommunications and broadcasting requirements rather 
than having separate domestic system for each of these countries.
Some of the regional Satellite Systems include :
• EUTELSAT - providing video & data services to Europe, Middle 
East, Africa and large parts of Asian & American continents , 
• ARABSAT – provide satellite comm. Services to the Middle East, 
Africa and large parts of Europe,
• ASIASAT, MEASAT– providing satellite services to the Asia 
Pacific region
• ACeS (asia celular satellite) – providing services to Asia. Provide 
fully digital and optional data services throughout Asia
• Thuraya – provides mobile comm. Services to the Middle East, 
North & central Africa, Europe, Central Asia and the Indian 
subcontinent
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Domestic Satellite (DOMSAT)
Domestic satellites are used to provide various telecommunication 
services with in a country. 
Some countries with their own domestic satellite communications 
systems are:
• Canada (Anik F series)
• United States of America (Wester, SBS, Etc.)
• USSR (a series of Molniya Satellites)
• India (INSAT)
• Brazil (Brazilsat)
• Mexico (Morelos)
• China (Chinasat)
• Japan (CS, BS)
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SATELLITE SERVICES
The services of satellite communication can be classified into One-
way satellite communication link service and Two-way satellite
communication link service.
In one-way satellite communication link service, the information can
be transferred from one earth station to one or more earth stations
through a satellite. It provides both point to point connectivity and
point to multi point connectivity. For example:
• Broadcasting satellite services like Radio, TV and Internet
services.
• Space operations services like Telemetry, Tracking and
Commanding services.
• Radio determination satellite service like Position location
service.
In two-way satellite communication link, the information can be
exchanged between any two earth stations through a satellite. It
provides only point to point connectivity. Such as:
• Fixed satellite services like Telephone, Fax and Data of high bit
rate services.
• Mobile satellite services like Land mobile, Maritime and Aero
mobile communication services.
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Operational Frequencies
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Fixed Satellite Services (FSS)
Satellites providing Fixed-Satellite Services (FSS) transmit radio
communications between ground Earth stations at fixed locations.
Satellite-transmitted information is carried in the form of radio-
frequency signals. Any number of satellites may be used to link these
stations. Earth stations that are part of fixed-satellite services
networks also use satellite news gathering vehicles to broadcast
from media events, such as sporting events or news conferences.
In addition, FSS satellites provide a wide variety of services including
paging networks and point-of-sale support, such as credit card
transactions and inventory control.
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Broadcasting satellite service (BSS)
A radiocommunication service in which signals transmitted or
retransmitted by space stations are intended for direct reception by
the general public. In the broadcasting-satellite service, the term
"direct reception" shall encompass both individual reception and
community reception.
Mobile satellite service (MSS)
Mobile satellite services (MSS)refers to networks of
communications satellites intended for use with mobile and portable
wireless telephones.
There are three major types: AMSS (aeronautical MSS), LMSS (land
MSS), and MMSS (maritime MSS).
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Navigational Satellite Services
A satellite navigation or satnav system is a system that uses satellites
to provide autonomous geo-spatial positioning. It allows small
electronic receivers to determine their location (longitude, latitude,
and altitude/elevation) to high precision (within a few metres) using
time signals transmitted along a line of sight by radio from satellites.
The system can be used for navigation or for tracking the position of
something fitted with a receiver (satellite tracking).
The signals also allow the electronic receiver to calculate the current
local time to high precision, which allows time synchronization.
Satnav systems operate independently of any telephonic or internet
reception, though these technologies can enhance the usefulness of
the positioning information generated.
A satellite navigation system with global coverage may be termed a
global navigation satellite system (GNSS), oldest US Global
Positioning System (GPS), the Russian GLObal Navigation Satellite
System(GLONASS) and the European GALILEO system.
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Meteorological Satellite Service
The weather satellite is a type of satellite that is primarily used to
monitor the weather and climate of the Earth. Satellites can be polar
orbiting, covering the entire Earth asynchronously, or geostationary,
hovering over the same spot on the equator.
Meteorological satellites see more than clouds and cloud systems.
City lights, fires, effects of pollution, auroras, sand and dust storms,
snow cover, ice mapping, boundaries of ocean currents, energy flows,
etc., and other types of environmental information are collected
using weather satellites.
Weather satellite images helped in monitoring the volcanic ash cloud
from Mount St. Helens and activity from other volcanoes such as
Mount Etna. Smoke from fires in the western United States such as
Colorado and Utah have also been monitored.
Other environmental satellites can detect changes in the Earth's
vegetation, sea state, ocean color, and ice fields.
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Measat 3a/3b/5
MEASAT (Malaysia East Asia Satellite) is the name of a line of
Malaysian communications satellites owned and operated by
MEASAT Satellite Systems Sdn. Bhd. (formerly Binariang Satellite
Systems Sdn. Bhd.).
In 2006, the MEASAT satellite network consists of three
geostationary satellites designed and built by Boeing Satellite
Development Center (formerly Boeing Satellite Systems). MEASAT-1
and MEASAT-2 were launched in 1996 and MEASAT-3 in 2006.
The MEASAT-1 and 2 satellites were designed to provide 12 years of
both direct to user television service in Malaysia and general
communications services in the region from Malaysia to the
Philippines and from Beijing to Indonesia.
With the launch of MEASAT-3, the coverage extends to 70% of the
world’s population . With the two high-powered Boeing 376HP
communications satellites provided regional C-Band coverage and
pioneered the use of Ku-Band in the high rain fall South East Asia
region.
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The communication satellite used consist of several applications
which is telephony, satellite television and radio, mobile satellite
technology, amateur radio, satellite broadband and also military
communications. Another function is satellite broadband. It has been
used to connect to the Internet via broadband data connections in
Malaysia.
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SUMMARY/RECAP
• Satellite system elements
• Types of earth station
• satellite organizations
• Satellite services
• MEASAT satellite
REFERENCES
1. Anil K. Maini, Varsha Agrawal, Satellite Technology: Principles and
Applications
2. Satellite Communication System Engineering, Louise J. Ippolito,
2009, John Wiley & Son Ltd, (Ebook)
3. Satellite Communication, 4th edition, Dennis Roddy, 2006, Mc-
Graw Hill (Ebook)
4. Fundamentals of satellite communication system,
http://vsagar.com/2011/12/10/fundamentals-of-satellite-
communication-system/
5. Satellite Communications, 
http://share.pdfonline.com/8a5f48fc99564b94bd0bbfaa3281373d
/Satellite%20Comm-LecIII.htm
6. Satellites
https://www.courses.psu.edu/aersp/aersp055_r81/satellites/satel
lites.html