Satellite

Best ppt. for satellite communication

1. Satellite Communications Technical Seminar BY Saroj Sah Hindustan University, C hennai

2. Contents Introduction Working principle Types of satellite Applications Advantage/Disadvantage Recent Development Conclusion

3. SATELLITE A satellite is a moon, planet or machine that orbits a planet or star. For example, Earth is a satellite because it orbits the sun. Likewise, the moon is a satellite because it orbits Earth. Usually, the word "satellite" refers to a machine that is launched into space and moves around Earth or another body in space.

4. Satellite Orbits Synchronous orbit It lies in the equatorial plane of the earth. This orbit is most useful orbit for communication purposes. b. Polar orbit c. Inclined orbit The path along which satellite moves in the space around earth are called orbits. A Satellite can move in three types of orbits namely:- a. . b . . c . .

5. Perigee : Nearest point on the orbit of a satellite from earth. Inclination: It is determined by the angle it makes with the equator. Characteristics of orbit are Apogee: Farthest point on the orbit of a satellite from earth.

6. The synchronous orbit is further classified into Geostationary Orbit : An orbit in which a satellite appears stationary relative to any point on earth. A satellite in such an orbit is at an altitude of approximately 35,786 km (22,236 mi) above mean sea level. An object in such an orbit has an  orbital period equal to the Earth's rotational period and thus appears motionless, at a fixed position in the sky, to ground observers. Communication satellites and   Weather satellites are often placed in geostationary orbits. Geosynchronous Orbit : A Satellite whose period of revolution equals to period of rotation of earth about its axis. In this, Satellite has 24 hours non-equatorial orbit. If a Satellite has a time period of 24 hours, then height of Satellite above earth may be determined about 35800km.

7. Geostationary Orbit :

8. Geosynchronous Orbit

9. Brief overview of orbits

10. Satellite Repeater The antenna can simply be pointed at the satellite and remain in a fixed position. With this arrangement, continuous communications are possible. Approximately 40% of the earth’s surface can be accessed from such a satellite. Hence, three such synchronous satellites are required to cover the entire earth. Three synchronous Satellite are placed in such a way to provide 100% earth coverage.

11. Types of Satellite Natural : Such as the moon orbiting around the earth Artificial: The international space station orbiting the earth A. B .

12. Communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunications signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Communications satellites are used for television, telephone , radio , internet, and military applications. There are over 2,000 communications satellites in Earth’s orbit , used by both private and government organizations.

13. Satellite Architecture and Organization

14. Block diagram of satellite

15. The major subsystem of satellite are Solar panels: They charge the batteries and supply the electric power for the spacecraft. 2. Communication subsystems: This is a set of transponders that receive the uplink signals and transmit them to the earth. 3. Telemetry , tracking and command subsystem: It monitors onboard conditions such as temperature and battery voltage and transmit them to ground station for analysis. 4. Attitude control subsystem: It provides stabilization in orbit and senses change in orientation 5. Propulsion subsystem: The jet thrusters and apogee kick motor (AKM) are part of propulsion subsystem and are commanded from ground.

16. Applications

17. Advantages of satellite 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.

18. Disadvantage 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 . Major problems for satellites Positioning in orbit Stability Power Communications Harsh Environment

19. Satellite Transmission Bands C Band are mostly used. It’s capacity is low and terrestrial interference is problem. In Ku band, rain interference is the problem. In Ka band, equipment needed to use the band is very expensive . Frequency Band Downlink Uplink C 3.7-4.2 GHz 5.92-6.42 GHz Ku 11.7-12.2 GHz 14.0-14.5 GHz Ka 17.7-21.2 GHz 27.5-31.0 GHz

20. Recent Developments

21. Recent Developments

22. Recent Developments

23. Conclusion Satellites remain the best utilization used for communications due to their speed and other advantages mentioned in this presentation.

24. Reference : https://en.wikipedia.org/wiki/Communications_satellite http://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-a-satellite-58.html http://science.howstuffworks.com/satellite7.htm http://www.space.com/24839-satellites.html http://www.jpl.nasa.gov/jplhistory/early/ firstsatellites.php http://ocw.mit.edu/courses/aeronautics-and-astronautics/16-851-satellite-engineering-fall-2003/lecture-notes/ l21satelitecomm2_done.pdf http://www2.nict.go.jp/wireless/spacelab/lasersatellitetech/icsos/icsos2012/pdf/1569604601. pdf

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