Introduction to satellite Communications

1. Introduction to satellite Communications Lecture (11) Dr. Hassan Yousif

2. What is a satellite? Satellite is an object launched to orbit earth or another celestial body. Dr. Hassan Yousif

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4. How it works Dr. Hassan Yousif

5. Features of Satellites: Providing global coverage. • Carrying large amount of traffic • For satellite systems the cost is “distance insensitive” • Remote sensing(pollution, weather, search and rescue) Dr. Hassan Yousif

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7. How it launches • Anything on the surface of the Earth at the equator is already moving at 1670 kilometers per hour.  • If you look at two spots on one line from pole to pole, one spot on the equator and the other halfway to the pole, each will make a complete revolution in 24 hours and return to where it was. But since the Earth's shape is round, and the widest point is at the equator the spot on the equator would have to go more miles in that twenty four hours. • That means that the land is moving faster at the equator than any other place on the surface of the Earth. • The land at the equator is moving 1670 km per hour, and land halfway to the pole is only moving 1180 km per hour, so launching from the equator makes the spacecraft move almost 500 km/hour faster once it is launched. Dr. Hassan Yousif

8. Applications • Traditionally • weather satellites • radio and TV broadcast satellites • military satellites • satellites for navigation and localization (e.g., GPS) • Telecommunication • global telephone connections • backbone for global networks • connections for communication in remote places or underdeveloped areas • global mobile communication •  satellite systems to extend cellular phone systems (e.g., GSM or AMPS) Dr. Hassan Yousif

9. Advantages of Satellites • The advantages of satellite communication over terrestrial communication are: • 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. Dr. Hassan Yousif

10. Disadvantages of Satellites • 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. Dr. Hassan Yousif

11. Satellite-Related Terms • Earth Stations – antenna systems on or near earth • Uplink– transmission from an earth station to a satellite • Downlink – transmission from a satellite to an earth station • Transponder – electronics in the satellite that convert uplink signals to downlink signals Dr. Hassan Yousif

12. Satellite System Elements Space Segment Satellite Coverage Region Earth Stations SCC TT&C Ground Station Ground Segment Dr. Hassan Yousif

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14. Space Segment • Satellite Launching Phase • Transfer Orbit Phase • Deployment • Operation • TT&C - Tracking Telemetry and Command Station • SSC - Satellite Control Center: • OCC - Operations Control Center • SCF - Satellite Control Facility Provides link signal monitoring for Link Maintenance and Interference monitoring. • Retirement Phase Dr. Hassan Yousif

15. Satellite Subsystems • Communications • Antennas • Transponders • Common Subsystem (Bus Subsystem) • Telemetry/Command (TT&C) • Satellite Control (antenna pointing, attitude) • Propulsion • Electrical Power • Structure • Thermal Control Dr. Hassan Yousif

16. Satellite Services • Fixed Service Satellites (FSS) • Example: telephone system, Sat to Cable • Broadcast Service Satellites (BSS) • Example: Satellite Television/Radio Also called Direct Broadcast Service (DBS). • In Europe called DTH • Mobile Service Satellites (MSS) • Include land mobile, maritime mobile, and aeronautical mobile. • Navigational satellite services i.e. GPS • Meteorological satellite services i.e. Weather and rescue service Dr. Hassan Yousif

17. Frequency Allocationsfor Satellite Services • To facilitate frequency planning, the world is divided into three regions: • Region 1: Europe, Africa • Region 2: North and South America and Greenland • Region 3: Asia, Australia, and the southwest Pacific Dr. Hassan Yousif

18. Intelsat 10 at 68.5º E Africa footprint. Dr. Hassan Yousif

19. Telestar 12 footprint Dr. Hassan Yousif

20. NileSat footprint Dr. Hassan Yousif

21. Services provided by satellites: • Fixed satellite service (FSS), telephone network • Broadcasting satellite service (BSS ), DTH • Mobile satellite services ( MSS), land, maritime • Navigational satellite services (NSS), GPS • Meteorological satellite services (MSS), SARS Dr. Hassan Yousif

22. Frequency band designations Dr. Hassan Yousif

23. ITU Frequency Band Designation Dr. Hassan Yousif

24. Intelsat V Dr. Hassan Yousif

25. Intelsat VI Dr. Hassan Yousif

26. An Earth Observation Sat (EOS) Dr. Hassan Yousif

27. A communication sat. Dr. Hassan Yousif

28. Important Terminologies • Apogee (point of farthest approach) • Perigee (point of closest approach) • Line of Apsides • Ascending node • Descending node • Line of nodes • inclination Dr. Hassan Yousif

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30. Apogee & Perigee heights The Length of the radius vectors at the apogee and perigee: ra = a (1 + e) rp = a (1 - e) Dr. Hassan Yousif

31. Example (2-1) Calculate the apogee and perigee heights for a satellite orbit, given that e = 0.0011501 a=7192.3 Km. Assume that the mean earth radius is 6371 Km. Dr. Hassan Yousif

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34. Types of Satellites: • INTELSAT(international Telecom. Satellite) • GEO, AOR+IOR+POR+IAR • DOMSAT(domestic Satellite) • GEO • Polar Orbiting Satellites • Sun synchronous, ascending pass, descending pass Dr. Hassan Yousif

35. The evolution of Intelsat satellite Dr. Hassan Yousif