Satellite communication systems provide telecommunication, television broadcasting, and data services globally. Geostationary satellites are used for services like DTH television and VSAT, while non-geostationary satellite constellations enable mobile communication services. Transponders on satellites receive and transmit signals, and different types like transparent and regenerative transponders process signals in various ways. Regional satellite systems provide coverage for specific geographic areas, while national systems like INSAT serve domestic communication needs.

2. Communication-related Applications of
Satellites
• Telecommunication satellites provide a varied range of services mainly
including television broadcasting, international telephony and data
communication services, most of these services being multipurpose in
nature.
• GEO satellites in point-to-multipoint configuration are employed for
satellite TV applications.
There are primarily two types of satellite television distribution systems,
namely the television receive-only (TVRO) and the direct broadcasting
satellite (DBS) systems.
• Satellites also provide data communication services including data,
broadcast and multimedia services such as data collection and broadcasting,
image and video transfer, voice, internet, two-way computer interactions
and database inquiries.

3. Geostationary Satellite Communication
Systems
• These satellites were used for international, regional and domestic
telephone and video distribution services. Some of the important
geostationary satellite missions include Intelsat, Inmarsat, Telstar
• The most important applications of geostationary communication
satellites in the current scenario include DTH satellite television
broadcasting services and VSAT services.

4. Non-geostationary Satellite Communication
Systems
• Non-geostationary satellite communication systems are emerging to
provide mobile communication services as well as other services like
messaging, video, fax and data communication.
• Constellations of satellites orbiting in LEO or MEO orbits can provide
global mobile communication services

11. Payloads

12. Transponder
• The device on board the satellite that performs the amplification and
frequency conversion is referred to as a transponder and is the main
payload of any communication satellite.
• Transponders may be broadly classified into two types depending
upon the manner in which they process the signal:
1. Transparent or bent pipe transponders
2. Regenerative transponders

13. Transparent or Bent Pipe Transponders

14. Regenerative Transponders
• Regenerative transponders are those in which some onboard
processing is done and the received signal is altered before
retransmission
• These repeaters are also called digital processing repeaters as they use
various digital techniques like narrowband channel selection and
routing, demodulation, error correction, reformatting of data, etc., for
processing the received signal.

15. Satellite versus Terrestrial Networks
• Broadcast property – wide coverage area
• Wide bandwidth – high transmission speeds and large transmission
capacity
• Geographical flexibility – independence of location
• Easy installation of ground stations.
• Uniform service characteristics.
• Immunity to natural disaster
• Independence from terrestrial infrastructure.
• Cost aspects – low cost per added site and distance insensitive costs

16. Disadvantages of Satellites with Respect to
Terrestrial Networks
• Transmission delay
• Echo effects
• Launch cost of a satellite.

17. Satellite Telephony

18. A Typical Satellite TV Network

19. Direct Broadcasting Satellite (DBS) Services

20. Satellite Radio
• A satellite providing high fidelity audio broadcast services to the broadcast
radio stations is referred to as a satellite radio and is a major revolution in
the field of radio systems.
• Sound quality is excellent in this case due to a wide audio bandwidth of 5–
15 kHz and low noise provided over the satellite link. Satellite radio like the
satellite TV employ GEO satellites and the network arrangement for the
satellite radio is more or less identical to that used for TV broadcasting.
• Usingpoint-to-multipoint connectivity, the audio signals from various music
channels, news and sports
centres are transmitted by the satellite to a conventional AM or FM radio
station.

21. Regional Satellite Systems
• Regional satellite missions were established with the aim of
strengthening the communication resources of the countries belonging
to the same geographical area.
• Some of the regional satellite systems include Eutelsat, Arabsat,
AsiaSat, Measat, ACeS (Asia cellular satellite), Thuraya, etc.
•
EUTELSAT operates a fleet of satellites that provide communication
services to Europe, theMiddle East, Africa and large parts of the Asian
and American continents.

22. • Arabsat satellites provide satellite communication services to the Middle
East, Africa and large parts of Europe.
• The AsiaSatellite Telecommunications Company Limited (AsiaSat) and
Measat systems are Asia’s regional satellite operators, providing
satellite services to the Asia Pacific region.
•
ACeS is another satellite-based regional communication system providing
services to Asia. It provides fully digital video, voice and data services
throughout Asia.
• The Thuraya system provides mobile communication services to the Middle
East, North and Central Africa, Europe, Central Asia and the Indian
subcontinent

23. EUTELSAT (European Telecommunication
Satellite Organization)
• The EUTELSAT organization was formed in the year 1977 to commission the design and
construction of satellites and to manage the operation of regional satellite communication services
in Europe.
• The first communication satellite to be launched by EUTELSAT was the orbital test
satellite (OTS) in the year 1978, which carried out link tests with small Earth stations with the help
of a powerful antenna on board the satellite.
•
The ECS satellite programme was renamed the Eutelsat satellite programme.
• Eutelsat satellites provide television, telephony and data transmission
services on a regional basis.
• The more advanced satellites in this series also provided specific
services like business communication services and mobile communication services.
• In addition to
the Eutelsat satellites, other series of satellites, namely the Hot Bird, Eurobird and Atlantic Bird
series, were launched to expand the horizon of the services offered and the coverage area of the
satellites of the EUTELSAT organization.

24. National Satellite SystemS
• National satellite systems, also referred to as domestic satellite systems,
provide services to a particular country.
• National satellite systems were originally established by developed
countries like the USA, USSR and Canada to serve their country’s
population according to their specific needs.
•
Today, in addition to these developed countries, some developing nations
like India, China, Japan, etc., also have their own national satellite systems.
• Some of the domestic satellite systems include Galaxy, Satcom, EchoStar
and Telestar of the USA, Brasilsat of Brazil, INSAT of India, Optus of
Australia and Sinosat of China

25. INSAT (Indian National Satellite)
• Owned by the Indian Department of Space, named the Indian Space
Research Organization (ISRO),INSAT is one of the largest domestic
communication satellite networks in the world, providing services in
the areas of telecommunications, television broadcasting, mobile
satellite services and meteorology including disaster warning.
• INSAT is a joint venture of the Department of Space (DOS),
Department of Telecommunications (DOT), Indian Meteorological
Department (IMD), All India Radio (AIR) and Doordarshan.
• Making a modest beginning with the launch of INSAT-1A in
1982, the INSAT satellite programme has come a long way today.

26. • INSAT-1A belonged to the INSAT-1 series, further comprising INSAT-
1B, 1C and 1D satellites.
The INSAT-1 series was followed by INSAT-2 and INSAT-3 series of
satellites.
• They were super ceded by the INSAT-4 series of satellites.