The document provides an overview of satellite communication techniques for military aircraft. It discusses that while currently used UHF satellite communication is inexpensive and simple to install, it has limited capacity and is prone to interference. SHF and EHF satellite techniques offer increased bandwidth and capabilities like adaptive antennas. The document then discusses various components of satellite communication systems like different frequency bands used, types of satellites including GEO and LEO, advantages of satellite communication over terrestrial networks, and applications.

1. ABSTRACT
This paper outlines some of the techniques being developed to provide affordable, reliable
satellite communications suitable for a wide range of military aircraft, from agile platforms
such as jets and helicopters to surveillance, tanker and transport aircraft. It also gives an
overview of airborne SHF (Super High Frequency) and also EHF (Extremely High
Frequency) satcom techniques. Although presently used UHF (Ultra High Frequency)
satellite communication are relatively simple to install and comparatively inexpensive,
suffer from very limited capacity and are prone to multipath and unintentional interference
due to their poor antenna selectivity. Whereas, the SHF satcoms offer significantly
increased bandwidth for high data rates or increased use of spread-spectrum techniques,
together with localized (spot) coverage and adaptive antenna techniques - for nulling
unwanted signals or interference.
In popular usage, the term 'satellite' normally refers to an artificial satellite.
A satellite orbiting at an altitude of 22,300 miles would require exactly 24 hours to orbit
the earth. Hence such an orbit is called "geosynchronous" or "geostationary."
Both radio and television frequency signals can propagate directly from transmitter to
receiver.
The downlink may either be to a select number of ground stations or it may be broadcast
to everyone in a large area.
The amount of power, which a satellite transmitter needs to send out, depends a great deal
on whether it is in low earth orbit or in geosynchronous orbit.
One of the biggest differences between a low earth satellite and a geosynchronous satellite
is in their antennas.
We say that transmitters are only 10 or 15% efficient.
The ACTS concept involves a single, rather complicated, and expensive geosynchronous
satellite. An alternative approach is to deploy a "constellation" of low earth orbiting
satellites.
It will be necessary to mass-produce communications satellites, so that they can turn out
quickly and cheaply
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2. CONTENTS
S NO. Chapter page no
1 Introduction 3
2 History of Satellite Communication 4
3 Components & Working of Satellite Communication
5
4 Different Frequency Bands used in Satellite Communication
12
5 Types of Satellites
12
6 Why Satellites for Communications?
14
7 Advantage of Satellite Communication
16
8 Disadvantage of Satellite Communication
17
9 Application
17
10 Future Satellite Communication 20
11 Conclusion
21
Recent Indian Space Missions
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3. Chapter 1
Introduction
A Satellite is a solid object which revolves around some heavenly body due to the
effect of gravitational forces which are mutual in nature. We can categorize satellites in
two types, namely Passive Satellites and Active satellites. Passive satellites are not like
active satellites. Even a moon can be a passive satellite. Thus passive satellites are relay
stations in space. A passive satellite can be further subdivided into two types, namely
Natural satellites and artificial satellites. A moon is a natural satellite of earth. But
spherical balloon with metal coated plastic serve as artificial satellites.
Active satellites are complicated structures having a processing equipment called
Transponder which is very vital for functioning of the satellite. These transponders serve
dual purpose i.e. provides amplification of the incoming signal and performs the
frequency translation of the incoming signal to avoid interference between the two
signals.
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4. Chapter 2
History of Satellite Communication
 USSR launched the first artificial earth satellite, Sputnik in 1957.
 US launched the first GEO satellite, Relay-1 in 1962.
 First trans pacific TV traffic distribution in 1963.
Satellite Communication in the Early Internet
 First satellite packet radio network in 1970.(ALOHAnet).
 Satellites connected the American continent and UK in 1975.(SATNET).
 First demonstration of interconnection between ARPANET, SATNET and PRNET in
1977.
 First TCP specification was released in 1982.
Satellite Communication in India
The first satellite that was used for communication purpose in INDIA was ARYABHATTA and
it was launched in 19th
April.1975. It was made and assembled by an organization called
Indian Space Research Organization (ISRO). In the year 1981, a satellite named APPLE was
launched in space which was the first Indian Experimental communication satellite. The
unique feature of it was that it was a three axis stabilization geosynchronous satellite and
weighed around 645 kg. The term APPLE is an abbreviation for Ariane Passenger Payload
Experiment. It consisted of a (6/4 Ghz) processing equipment called Transponder. Various
experiments were carried out with APPLE, [SITE, STEP (Other satellite telecommunication
experiment projects)] and the results obtained from these experiments provided an impetus
for Govt. of India to have its own multipurpose Geosynchronous Earth Orbit satellite under
INSAT (Indian National Satellite) program. The first satellite INSAT-1A was launched in the
year 1982 which was under this INSAT program, but this effort went in vain as the power
house of this satellite consisting of solar cells did not operate properly( failed to open) and
this satellite was unused latter on. The average electrical power required by INSAT-1 was
approximately 1000W and was provided by the power house subsystem of the satellite. The
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5. payload was one C-band transponder and two S-band transponders. Later succession of
INSAT-1 series was launched like INSAT-1B, INSAT-C and INSAT-D. After this due to the
success of the first generation satellites, INSAT-2 series was launched viz. INSAT-2A, INSAT-
2B, INSAT-2C, INSAT-3D and INSAT-2E which provided variety of services.
Chapter 3
Components & Working of Satellite Communication
Basic component of satellite communication
The term Satellite communication is very frequently used, but what is satellite
communication? It is simply the communication of the satellite in space with large
number of earth stations on the ground. Users are the ones who generate baseband
signals, which is processed at the earth station and then transmitted to the satellite
through dish antennas. Now the user is connected to the earth station via some
telephone switch or some dedicated link. The satellite receives the uplink frequency and
the transponder present inside the satellite does the processing function and frequency
down conversion in order to transmit the downlink signal at different frequency. The
earth station then receives the signal from the satellite through parabolic dish antenna
and processes it to get back the baseband signal. This baseband signal is then
transmitted to the respective user via dedicated link or other terrestrial system.
Previously satellite communication system used large sized parabolic antennas with
diameters around 30 meters because of the very faint and weak signals received. But
nowadays satellites have become much stronger, bigger and powerful due to which
antennas used have become automatically smaller in size. Thus the earth station
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6. antennas are now not large in size as the antennas used in olden days. A satellite
communication system operates and works in the millimeter and microwave wave
frequency bands from 1 Ghz to 50 Ghz. There are various frequency bands utilized by
satellites but the most recognized of them is the uplink frequency of 6 Ghz and the
downlink frequency of 4 Ghz. Actually the uplink frequency band is 5.725 to 7.075 Ghz
and the actual downlink frequency band is from 3.4 to 4.8 Ghz. The major components of
a Satellite Communication system is spacecraft and one or more earth earths.
THE EXCITING COMPONENTS OF SATELLITE i.e ITS SUBSYSTEMS
• Attitude & orbit control system:
This subsystem comprises of rocket motors that keeps the correct orientation of the
satellite in space by moving it back to the correct orbit. Various external forces cause to change
the parking position of the satellite. The primary factors are gravitational forces of sun, moon
earth and also other planets of solar system. Other factors include solar pressure on the
antennas and solar sails, which is present on the body of the satellite. All these factors are
hugely responsible for misbalancing of the satellite and also responsible for changing the
parking position of the satellite. Apart from this the earth’s magnetic field is also playing a major
role in changing the parking position of satellite. The earth’s magnetic field generates eddy
currents in the metallic structure of the satellite as the satellite moves through the magnetic
field. Thus the body of the satellite gets rotated called as wobble of the satellite.
Remedy for Misbalancing of the satellite: station keeping:
It is a method of periodically accelerating the satellite in the opposite
direction against the forces acting on the body of the satellite like gravitational forces,
eddy currents etc. in order to maintain the correct orientation of satellite in space and
maintaining its orbit. The two most common methods employed to keep the satellite
stable in orbit are: spin stabilization and three axes body stabilization.
• TTC and M SUBSYSTEMS:
These subsystems are found partly on the satellite and partly on the earth stations. Data
obtained from the sensors present on the spacecraft are sent by the Telemetry systems
through telemetry link to the controlling earth stations. The telemetry system monitors
the condition of the spacecraft. Furthermore the Tracking system is present on the earth
station which is all concerned about range, azimuth angles and elevation angles of the
spacecraft by providing necessary information on it. There are various techniques used
for tracking of satellite:
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7. 1.Velocity and acceleration sensors on the satellite can be used to establish the
change in orbit.
2. Doppler shift of the telemetry carrier from the earth station or beacon transmitter
may be measured to determine the rate at which the range is changing.
3.Ranging tones may be used for range measurement.
 POWER SUBSYSTEM:
This is required to run satellite’s housekeeping and communication system. The block
diagram of the power subsystem is shown as:
Solar panels generate direct current which is used to operate different subsystems. The
batteries like Nickel-Cadmium batteries are charged by the DC power by employing the
battery chargers. The stabilized low voltage is supplied to power various subsystems
which are generated by the voltage regulator circuits. A dc to dc converter circuit
generates high voltage dc which is used for operating the traveling wave tube amplifiers.
Generation of ac from dc is done by dc to ac inverter circuits for running ac devices.
• PROPULSION SUBSYSTEM
This subsystem can also be called as a reaction control subsystem. It is carried by the
satellite in the GEO orbit. The dominant functions of it are:
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8. · It helps the spacecraft to move to its assigned position in orbit and also helps to
maintain it in that position.
· It is also used to maintain the direction of spin axis attitude control against the
perturbation forces.
The main components of propulsion subsystem are: Low thrust actuators, High
thrust motors eg: apogee kick motor, Apogee boost motor and finally Perigee
kick motor. Low thrust actuators are further classified as Chemical
thrusters andElectrical thrusters. These thrusters are used for attitude and orbit
corrections. Moreover the Electric thrusters are mainly of two types 1.> Plasma
thrusters 2.>Ion thrusters.
• SPACECRAFT ANTENNA (subsystem)
Antenna subsystem is also an essential component of satellite system. Basically four
main type of antennas are used: these are Monopoles and dipoles (wire antennas)
which are mainly used in VERY HIGH FREQUENCY AND ULTRA HIGH FREQUENCY to
provide communication for TTC and M subsystem. 2.> Horn antennas are mainly used at
microwave frequencies. Horns are actually used as feeds for reflector. 3.> Array
antennas are actually phased array antennas which are used on satellites to form
multiple beams from single aperture. 4> Reflector antennas are commonly used for
earth station antennas and the most widely employed shape of it is the paraboloid with a
feed placed at its focus. The patterns for different satellite antennas are shown as:
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9. • THE KEY ELECTRONIC EQUIPMENT IN A SATELLITE OR TRANSPONDERS:
It is the key electronic component in a satellite. The transmitter receiver combination in
a satellite is known as a Transponder. It performs two major functions 1.> It provides
amplification of the signal thus providing a gain of around 110dB. 2> It also does the
frequency down conversion or frequency translation of the uplink signal in order to
avoid interference between the received and the transmitted signal.
Types of Transponders: 1. Bend pipe type Transponder 2. Regenerative type Transponder.
Bend pipe type transponders are also called conventional type transponders.
Diplexer (acting as a two-way microwave gate) is the device which is responsible or
used by the satellite for both receiving the uplink signal and transmitting the downlink
signal. The frequency down conversion is done in the carrier processor. Amplification of
the weak received signal is done in the front end. The downlink frequency is brought to
a sufficient power level by amplification by the power amplifier such as Traveling Wave
tube. The carrier processing equipment determines whether the transponder is of
conventional or regenerative type
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10. Regenerative Transponders: The regenerative transponder is one where there is
provision for detection and demodulation process. The main advantages for these kind
of transponders are:
· The signal to noise ratio is improved.
· These are simpler and more flexible to implement.
· At low baseband frequency the amplification is easier to obtain in case of
regenerative type.
Types of multi channel transponder systems:
• Broadband system
• Dual channelized system.
The various frequency translation schemes in use:
FOR CONVENTIONAL TRANSPONDERS
• RF-RF Translation:
This is a single mixer system. The diagrams of it is shown below:
• RF-IF-RF translation schemes:
This is a double conversion scheme using a single stable oscillator. This
kind of translation scheme provides two advantages over RF-RF conversion
scheme: 1. The process of carrier filtering is done at the IF band. 2. Before the
return transmitted signal the uplink carriers can be easily removed. The diagram
of it is shown below:
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11. FOR REGENERATIVE TRANSPONDERS
The two common schemes are:
• IF Remodulation scheme:
In this technique the uplink RF spectrum is first translated down to low
IF band , which is then modulated on to return RF.
• Demodulation- Remodulation scheme:
The remodulation removes the uplink noise and interference from return
modulation.
SATELLITE LAUNCH VEHICLES:
Satellites are launched into its orbit by the satellite launch vehicles. These
satellite launch vehicles are basically multistage rockets. It is classified into two types:
• Expendable launch vehicle (ELV)
eg: Ariane, Delta etc. These vehicles get destroyed in space and it also
carries more than one satellite with it.
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12. • Reusable launch vehicle (RLV).
Also known as space transportation system (STV) eg: Space shuttle. In
case of these satellites the vehicle will return back to the earth after leaving the
satellite in space. Thus they can be reused again and again.
Components of Launch vehicle:
• Propulsion system.
• Auto piloting system
• Aerodynamic structure
• Interactive steering subsystem
DIFFERENCE OF COMMUNICATION SATELLITE FROM COMMUNICATION RELAY:
• For communication satellites the range is much higher than that of communication
relay. Communication Satellite can cover up to several thousand kilometers.
• For communication satellite the uplink and the downlink frequency is the same.
But for communication satellites the uplink and the downlink frequencies are
different in order to avoid interference.
Chapter 4
Different Frequency Bands used in Satellite Communication:
• Ultra high frequency band (UHF).
• C-Band.
• X-Band.
• Ku-Band
• Ka-Band
Such as----
L–Band: 1 to 2 GHz, used by MSS
S-Band: 2 to 4 GHz, used by MSS, NASA, deep space research
C-Band: 4 to 8 GHz, used by FSS
X-Band: 8 to 12.5 GHz, used by FSS and in terrestrial imaging, ex: military and
meteorological satellites
Ku-Band: 12.5 to 18 GHz: used by FSS and BSS (DBS)
K-Band: 18 to 26.5 GHz: used by FSS and BSS
Ka-Band: 26.5 to 40 GHz: used by FSS
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13. Chapter 5
Types of Satellites
Geostationary Earth Orbit (GEO)
These satellites are in orbit 35,863 km above the earth’s surface along the
equator.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 earth.
 Advantages
 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 hour view of a particular area.
 These factors make it ideal for satellite broadcast and other multipoint
applications
 Disadvantages
 A 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.
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14.  GEO satellites, centered above the equator, have difficulty broadcasting
signals to near polar regions
Low Earth Orbit (LEO)
LEO satellites are much closer to the earth than GEO satellites, ranging from 500 to 1,500
km above the 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
satellites is necessary for LEO satellites to be useful.
Advantages
 A LEO satellite’s proximity 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 to point
communication.
 A LEO satellite’s smaller area of coverage is less of a waste of bandwidth.
Disadvantages
 A network of LEO satellites is needed, which can be costly
 LEO satellites have to compensate for Doppler shifts cause by their relative
movement.
 Atmospheric drag effects LEO satellites, causing gradual orbital deterioration.
Medium Earth Orbit (MEO)
A MEO satellite is in orbit somewhere between 8,000 km and 18,000 km above the earth’s
surface. MEO satellites are 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 a larger coverage area than LEO satellites.
Advantage
 A MEO satellite’s longer duration of visibility and wider footprint means fewer
satellites are needed in a MEO network than a LEO network.
Disadvantage
 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.
Astronomical satellites are satellites used for observation of distant planets, galaxies, and
other outer space objects.
Communications satellites are artificial satellites stationed in space for the purposes of
telecommunications using radio at microwave frequencies. Most communications satellites
use geosynchronous orbits .
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15. Earth observation satellites are satellites specifically designed to observe Earth from
orbit, similar to reconnaissance satellites but intended for non-military uses such as
environmental monitoring, meteorology, map making etc.
Navigation satellites are satellites, which use radio time signals transmitted to enable
mobile receivers on the ground to determine their exact location. The relatively clear line of
sight between the satellites and receivers on the ground, combined with ever-improving
electronics, allows satellite navigation systems to measure location to accuracies on the
order of a few meters in real time.
Space stations are man-made structures that are designed for human beings to live on in
outer space. A space station is distinguished from other manned spacecraft by its lack of
major propulsion or landing facilities instead, other vehicles are used as transport to and
from the station. Space stations are designed for medium-term living in orbit, for periods of
weeks, months, or even years.
Weather satellites are satellites that primarily are used to monitor the weather and/or
climate of the Earth.
Chapter 6
Why Satellites for Communications?
We had, of course, been able to do transatlantic telephone calls and
telegraph via underwater cables for almost 50 years. At exactly this time, however, a new
phenomenon was born. The first television programs were being broadcast, but the greater
amount of information required transmitting television pictures required that they operate
at much higher frequencies than radio stations.
A typical television station would operate at a frequency of 175 MHz. As a result, television
signals would not propagate the way radio signals did.
Both radio and television frequency signals can propagate directly
from transmitter to receiver. This is a very dependable signal, but it is more or less limited
to line of sight communication. The mode of propagation employed for long distance radio
communication was a signal, which traveled by bouncing off the charged layers of the
atmosphere (ionosphere) and returning to earth. The higher frequency television signals
did not bounce off the ionosphere and as a result disappeared into space in a relatively
short distance. This is shown in the diagram below
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16. Radio Signals Reflect Off the Ionosphere; TV Signals Do Not.
Low Earth-Orbiting Communications Satellites:
In 1960, the simplest communications satellite ever conceived was
launched. It was called Echo, because it consisted only of a large (100 feet in diameter)
aluminized plastic balloon. Radio and TV signals transmitted to the satellite would be
reflected back to earth and could be received by any station within view of the satellite.
Echo Satellite
Unfortunately, in its low earth orbit, the Echo satellite circled the
earth every ninety minutes. This meant that although virtually everybody on earth would
eventually see it, no one person, ever saw it for more than 10 minutes or so out of every 90
minute orbit. In 1958, the Score satellite had been put into orbit. It carried a tape recorder,
which would record messages as it passed over an originating station and then rebroadcast
them as it passed over the destination. Once more, however, it appeared only briefly every
90 minutes - a serious impediment to real communications. In 1962, NASA launched the
Telstar satellite for AT&T.
Telstar's orbit was such that it could "see" Europe" and the US simultaneously
during one part of its orbit. During another part of its orbit it could see both Japan and the
U.S. As a result, it provided real- time communications between the United States and those
two areas - for a few minutes out of every hour.
Geo-synchronous Communications Satellites:
The solution to the problem of availability, of course, lay in the use
of the geo-synchronous orbit. In 1963, the necessary rocket booster power was available
for the first time and NASA launched the geo-synchronous satellite, Syncom 2. For those
who could "see" it, the satellite was available 100% of the time, 24 hours a day. The
satellite could view approximately 42% of the earth. For those outside of that viewing area,
of course, the satellite was NEVER available.
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17. Launching stages of a GEO
Chapter 7
Advantage of Satellite Communication
 Wide coverage
 Almost one third of the earth except the polar regions is visible from a
geostationary satellite. It is, therefore, possible to cover wide geographical
area irrespective of intervening terrain using a single satellite. Satellite media
is the only alternative for remote areas inaccessible through terrestrial
routes.
 By suitable design and configuration of earth station equipment, satellite
links can be used for thin and heavy traffic routes in a cost effective manner.
 Suitable for both Digital and Analog Transmission
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18.  Same satellite can be used for both digital and analog communication links.
Satellite is transparent to the type of service being provided.
 High Quality
 Satellite links are designed high quality of performance. The links are free
from atmospheric disturbances and fading. As only one repeater is involved,
the reliability is very high.
• Flexibility
 In terrestrial links, the topology of the network gets tied down to the
installed equipment. On the other hand, a satellite can be accessed from any
point on the earth from where it is visible. The earth stations can be relocated
and reconfigured providing complete flexibility of operation and utilisation of
the satellite capacity.
• Quick Provision of Services
 Compared to the terrestrial links, earth stations can be installed in much
shorter period and, therefore, services can become available faster.
• Mobile and Emergency Communication
 An earth station can be mounted on a vehicle to provide mobile
communication services. Using small air liftable earth station terminals,
telecommunication services can be extended to any location in emergency
Chapter 8
Disadvantage of Satellite Communication
The disadvantages of satellite communication:
 Launching satellites into orbit is costly.
 Satellite bandwidth is gradually becoming used up.
 There is a larger propagation delay in satellite communication than in terrestrial
communication.
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19. Chapter 9
Application
 Traditional Telecommunications
Since the beginnings of the long distance telephone network, there has been a
need to connect the telecommunications networks of one country to another. This has been
accomplished in several ways. Submarine cables have been used most frequently. However,
there are many occasions where a large long distance carrier will choose to establish a
satellite based link to connect to transoceanic points, geographically remote areas or poor
countries that have little communications infrastructure. Groups
like the international satellite consortium Intelsat have fulfilled much of the world's need
for this type of service.
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20.  Cellular
Various schemes have been devised to allow satellites to increase the
bandwidth available to ground based cellular networks. Every cell in a cellular network
divides up a fixed range of channels which consist of either frequencies, as in the case of
FDMA systems, or time slots, as in the case of TDMA. Since a particular cell can only operate
within those channels allocated to it, overloading can occur. By using satellites which
operate at a frequency outside those of the cell, we can provide extra satellite channels on
demand to an overloaded cell. These extra channels can just as easily be, once free, used by
any other overloaded cell in the network, and are not bound by bandwidth restrictions like
those used by the cell. In other words, a satellite that provides service for a network of cells
can allow its own bandwidth to be used by any cell that needs it without being bound by
terrestrial bandwidth and location restrictions.
 Television Signals
Satellites have been used for since the 1960's to transmit broadcast television
signals between the network hubs of television companies and their network affiliates. In
some cases, an entire series of programming is transmitted at once and recorded at the
affiliate, with each segment then being broadcast at appropriate times to the local viewing
populace. In the 1970's, it became possible for private individuals to download the same
signal that the networks and cable companies were transmitting, using c-band reception
dishes. This free viewing of corporate content by individuals led to scrambling and
subsequent resale of the descrambling codes to individual customers, which started the
direct-to-home industry. The direct-to-home industry has gathered even greater
momentum since the introduction of digital direct broadcast service.
 C-band
C-Band (3.7 - 4.2 GHz) - Satellites operating in this band can be spaced as
close as two degrees apart in space, and normally carry 24 transponders operating at 10 to
17 watts each. Typical receive antennas are 6 to 7.5 feet in diameter. More than 250
channels of video and 75 audio services are available today from more than 20 C-Band
satellites over North America. Virtually every cable programming service is delivered via C-
Band.
 Ku-Band
• Fixed Satellite Service (FSS)
Ku Band (11.7 - 12.2 GHz) - Satellites operating in this band can be spaced as
closely as two degrees apart in space, and carry from 12 to 24 transponders that operate at
a wide range of powers from 20 to 120 watts each. Typical receive antennas are three to six
feet in diameter. More than 20 FSS Ku-Band satellites are in operation over North America
today, including several "hybrid" satellites which carry both C-Band and Ku-Band
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21. transponders. PrimeStar currently operates off Satcom K-2, an FSS or so-called "medium-
power" Ku-Band satellite. AlphaStar also uses an FSS-Ku Band satellite, Telestar 402-R.
• Broadcasting Satellite Service (BSS)
Ku-Band (12.2 - 12.7 GHz) - Satellites operating in this band are spaced nine
degrees apart in space, and normally carry 16 transponders that operate at powers in
excess of 100 watts. Typical receive antennas are 18 inches in diameter. The United States
has been allocated eight BSS orbital positions, of which three (101, 110 and 119 degrees)
are the so-called prime "CONUS" slots from which a DBS provider can service the entire 48
contiguous states with one satellite. A total of 32 DBS "channels" are available at each
orbital position, which allows for delivery of some 250 video signals when digital
compression technology is employed.
 DBS
DBS (Direct Broadcast Satellite) -The transmission of audio and video signals
via satellite direct to the end user. More than four million households in the United States
enjoy C-Band DBS. Medium-power Ku-Band DBS surfaced in the late 1990s with high
power Ku-Band DBS launched in 1994.
 Marine Communication
In the maritime community, satellite communication systems such as
Inmarsat provide good communication links to ships at sea. These links use a VSAT type
device to connect to geosynchronous satellites, which in turn link the ship to a land based
point of presence to the respective nations telecommunications system.
 Spacebourne Land Mobile
Along the same lines as the marine based service, there are VSAT devices which can be used
to establish communication links even from the world's most remote regions. These
devices can be hand-held, or fit into a briefcase. Digital data at 64K ISDN is available with
some (Inmarsat).
 Satellite Messaging for Commercial Jets
Another service provided by geosyncronous satellites are the ability for a passenger on an
airbourne aircraft to connect directly to a landbased telecom network.
 Global Positioning Services
Another VSAT oriented service, in which a small apparatus containing the ability to
determine navigational coordinates by calculating a triangulating of the signals from
multiple geosynchronous
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22.  APPLICATION OF SATELLITES IN POWER SYSTEMS
Smart grid
Local breaker backup in transmission line
Above 1000mw generation plant use VSAT communication for protection and generation
Climate change study for Wind/Tidal/Solar power plants
SCADA, RTU
Fault finding in HVDC/HVAC transmission line using GPS
Satellite remote sensing for assessment of nuclear power plants environment
Chapter 10
Future Satellite Communication:
The nature of future satellite communications systems will depend on the
demands of the market place the costs of manufacturing, launching, and operating
various satellite configurations; and the costs and capabilities of competing systems -
especially fiber optic cables, which can carry a huge number of telephone
conversations or television channels. In any case, however, several approaches are
now being tested or discussed by satellite system designers.
One approach, which is being tested experimentally, is the
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23. "switchboard in the sky" concept. NASA's Advanced Communications Technology
Satellite (ACTS) consists of a relatively large geosynchronous satellite with many
uplink beams and many downlink beams, each of which covers a rather small spot on
the earth. However, many of the beams are "steer able". The ACTS satellite is also
unique in that it operates at frequencies of 30 GHz on the uplink and 20 GHz on the
downlink. It is one of the first systems to demonstrate and test such high frequencies
for satellite communications
The ACTS concept involves a single, rather complicated, and expensive
geosynchronous satellite. An alternative approach is to deploy a "constellation" of low
earth orbiting satellites. By planning the orbits carefully, some number of satellites could
provide continuous contact with the entire earth, including the poles. By providing relay
links between satellites, it would be possible to provide communications between any two
points on earth, even though the user might only be able to see any one satellite for a few
minutes every hour. Obviously, the success of such a system depends critically on the cost
of manufacturing and launching the satellites.
 more onboard processing capabilities,
 more power, and
 larger-aperture antennas
 LASER Communications
Chapter 11
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24. Conclusion:
The use of satellite technology, particularly in the use of communications satellites has
grown rapidly in the past thirty years. Each day more and more uses for the satellites are
being discovered. Feeding this is the rapid advancement of technology that allows the quick
implementation of these uses.
Communications satellites will not only help out a person in distress but allow a person
walking the street in Manhasset N.Y. USA to use their cellular phone to speak with someone
in China. More and more satellites are being launched each year to support new and
growing uses for business, military and communication needs. Satellite communications
will continue in the right direction, UP.
By going through the above we came to know that satellite is mostly responsible for:
 Telecommunication transmission
 Reception of television signals
 Weather forecasting
 Electrical power systems
This is very important in our daily life.
References
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25.  IEEE Communications Magazine • May 2015
 www.google.com
 www.wikipedia.com
 www.satellitemarkets.com
 www.britannica.com/EBchecked/topic/524891/satellite-communication
 C. Sacchi et al., “Towards the Space 2.0 Era,” Guest Editorial, IEEE Commun.
Mag., Part 1, Feature Topic on Satellite Communications and Networking:
Emerging Techniques and New Applications, Mar. 2015.
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