1. Subject Name: SATELLITE COMMUNICATION Subject Code: 10EC662
Prepared By: Mrs. Savitra T.
Department: ECE
Date : 1/03/2015
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2. OVERVIEW OF SATELLITE COMMUNICATION
UNIT 1
OVERVIEW OF SATELLITE COMMUNICATION
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3. Topics covered
INTRODUCTION
FREQUENCY ALLOCATION
INTELSAT
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4. Satellites are used for large number of purpose. For eg:
INTRODUCTION:
The use of satellites in communication systems is very much use full for everyday life, as is evidenced by the many homes which are equipped with antennas/dishes, used for reception of satellite TV.
Satellite is an artificial object which has been intentionally placed into orbit. Such objects are sometimes called as Artificial satellite.
Satellites are used for large number of purpose. For eg:
Military & civilian earth observation satellites,
Communication satellites,
Navigation satellites,
Weather satellites,
Research satellites and so on.
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5. Satellite orbits vary greatly, depending on the 11/13/2018purpose of the satellite & are classified in a no of ways. For eg:
1. Low earth orbit
2. Polar orbit
3. Geostationary orbit
Satellites are usually semi-independent computer-controlled systems. Satellite subsystems attend many tasks such as power generation, thermal control, telemetry, attitude control & orbit control.
Satellites for an essential part of telecommunication carrying large amounts of data & telephone traffic in addition to TV signals.
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6. Satellites offer a number of features which are usually not readily available with other means of communication.
Since very large areas can be visible from a satellite, so that it can form a start point of comm. Net linking together many users simultaneously & uses who may be widely separated geographically
This feature helps to communicate with remote areas which are difficult to access by other means.
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7. To provide a general overview of satellite systems,
A feature of any satellite system is that the cost is distance insensitive. i.e, cost is same for any of the distance (short/long distances). Hence, satellite communication is economical if it is in continuous use & the cost is reasonably spread over a large number of users.
To provide a general overview of satellite systems,
The 3- different types of applications are briefly described here,
The largest international s/m (Intelsat)
The domestic satellite communication s/m (Domsat) in USA
U.S National oceanographic & atmospheric administration (NOAA) series of polar orbitrary satellite used for environmental monitory & search & rescue.
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8. FREQUENCY ALLOCATION:
FREQUENCY ALLOCATION:
Fixed satellite service (FSS) : Provides links for existing telephone networks & transmitting signals to cable companies for distribution over cable.
Broadcasting satellite services(BSS): For direct broadcast to home (Direct to home-DTH) ( Direct broadcast satellite-DSS).
Mobile satellite service(MSS): Include land mobile, aeronautical mobile, maritime mobile.
Navigational satellite services(NSS): Includes global positioning systems.
Meterological satellite services(MSS): provide a search & rescue service.
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9. Freg range(GHz) Band designation
VHF= used for certain mobile & navigational services & for data transfer from weather satellite
Vhf
L= used for mobile sat. services & navigation system S
C=(4-6 GHz widely used) for fixed satellite service X
Ku=(12-14GHz widely used) for direct broadcast.
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10. The C band is used for the many of the applications, but since it has very low capacity and C band is crowded and also because of its terrestrial interferences, it can not be used in DBS services. Instead of C band, the Ku band is used.
In the case of Ku band, rain is the only one problem though it has higher capacity and is less crowded. The bandwidth for C and Ku band are 0.5GHz.
User one who uses possibly 1m antenna, they will C band and the users who uses smaller 10 to 20 inches of antenna which uses Ku band.
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11. For international traffic, INTELSAT covers 3-main regions they are,
Intelsat stands for international telecommunications satellite. The organization was established in1964 & as the current status it has over 140 countries as the member of it & more than 40 investing entities
These satellites are in geostationary orbit ,i.e, they appear to be stationary in relation to the earth.
For international traffic, INTELSAT covers 3-main regions they are,
Atlantic ocean region (AOR)
Indian ocean region (IOR)
Pecific ocean region (POR)
For each of these regions, satellites are placed in geostationary orbit above the particular ocean, where they provide transoceanic telecommunication route.
The intelsat /A series was launched over a period from The construction is similar to that for the 5& 5A/5B series.
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12. In 1973, the name was changed and there were 80 signatories
In 1973, the name was changed and there were 80 signatories. Intelsat provides service to over 600 Earth stations in more than 149 countries, territories and dependencies. By 2001, INTELSAT had over 100 members. It was also this year that INTELSAT privatized and changed its name to Intelsat.
Since its inception, Intelsat has used several versions (blocks) of its dedicated Intelsat satellites. INTELSAT completes each block of spacecraft independently, leading to a variety of contractors over the years. Intelsat’s largest spacecraft supplier is Space Systems/Loral, having built 31 spacecraft (as of 2003), or nearly half of the fleet.
The network in its early years was not as robust as it is now. A failure of the Atlantic satellite in the spring of 1969  threatened to stop the Apollo 11 mission; a replacement satellite went into a bad orbit and could not be recovered in time;  
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13. Advantages & disadvantages of satellite communication : Advantages:
NASA had to resort to using undersea cable telephone circuits to bring Apollo's communications to NASA during the mission. Fortunately, during the Apollo 11 moonwalk, the moon was over the Pacific Ocean, and so other antennas were used, as well as INTELSAT III, which was in geostationary orbit over the Pacific.
Advantages & disadvantages of satellite communication :
Advantages:
Flexible
Easy to install new circuits.
Circuit costs independent of distances.
Broadcast possibilities.
Mobile applications provision of services to remote or underdeveloped areas
User has control over own network.
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14. A. Large up front capital costs (space segment & launch)
Disadvantages:
A. Large up front capital costs (space segment & launch)
B. Terrestrial breaks even distance expanding
C. Interference & propagation
D .Congestion of frequencies & orbit
Sat communication systems are cost insensitive. Distance doesn’t come into the equation. All users can connect at the same time no matter where they are, because distance doesn’t affect of connections.
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15. Summary :
The satellite are the communication equipments, used to capture huge information. They can be able to connect remote areas which are geographically apart from each other. The satellites are of two types, natural and artificial satellites. We studied frequency allocation for the satellites for different types of applications as different frequency ranges with specific band designations. Here the uplink and downlink frequency bands will be different for each applications. There are different types of satellites, in that we covered the evolution of intelsat from 1965 to till now.
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