1. 1.
Overview of Satellite Systems

2. Contents • What is satellite communication • The Origin of Satellite
• Elements of Satellite Communication
• Key input data
• Early Satellite Systems
• System Design Considerations
• Major Problems for Satellite
• Limitation for Satellites
• Advantages of Satellite
• Different Applications
• Frequency Allocation & Regulatory Aspects

3. What is Satellite Communication…
• A communication satellite is basically an
electronic communication package placed in orbit whose prime objective is to initiate or assist another through space.
• Satellite communication is one of the most
impressive spin-offs from the space programs and has made a major contribution to the pattern of international communication.
• The information transferred most often
correspondence to voice (telephone), video (Television) and digital data.

4. Cont...
• Communication satellite are off-course only one means of telecommunication transmission. The traditional means include copper wire and microwave point- to-point links. Newer techniques involves use of optics either point-to-point infrared or fiber optics.

5. The origin of satellite
• The concept of using object in space to reflect signals for communication was proved by Naval Research Lab in Washington D.C. when it use the Moon to establish a very low data rate link between Washington and Hawaii in late 1940’s.
• Russia started the Space age by successfully launching SPUTNIK the first artificial spacecraft to orbit of the earth, which transmitted telemetry information for 21 days in Oct
• America followed by launching an experimental satellite EXPLORER In 1958.
• In 1960 two satellite were deployed “Echo” & “Courier”
• The first commercial GSO (Geosynhronous Orbit)
(Intelsat & Molnya) in 1965 provided video (Television)
and voice (Telephone) for their audience

6. Elements of Satellite Communications
• The basic elements of a communication satellite service are divided between;
•Space Segment
•Ground Segment
• The space segment consist of the spacecraft & launch mechanism and ground segment comprises
the earth station and network control center of entire
satellite system.

7. Satellite Communications System
Uplink
Down Link
In door Unit
IDU RFT
RFT IDU RF
Transmit Earth Station
Receive Earth Station

8. Concept Transponder Earth station(site B) Earth station (site A)
downlink
downlink
uplink
uplink
Earth station(site B)
Earth station (site A)

9. Propagation Delay
Single Hop 270 ms
Double Hop 540 ms

10. Ground Station _ Anatomy
Interfacility Link
IFL
Indoor Unit
Outdoor Unit
Antenna
(IDU)
(ODU)
Sub-System
70/140 C/Ku MHz

11. Satellite Services
• The ITU has grouped the satellite services in to three main groups
• Fixed Satellite Services (FSS)
• Broadcast Satellite Services (BSS)
• Mobile Satellite services (MSS)

12. Space Segment
• Space segment consist of a satellite in suitable orbit.
• Space segment classified on the basis of orbit;
-LEO (Low Earth Orbit)
-MEO (Mid Earth Orbit)
-HEO (Highly Elyptical Orbit)
-GEO & GSO

13. Ground Segment
• The ground segment of each service has distinct characteristics.
• Services like;
• FSS (Fixed Sat. Serv.)
• BSS (Broadcast Sat. Serv.)
• MSS(Mobile Sat. Serv.)
-Maritime, Aeronautical & Land base
• DBS (Direct Broadcast Satellite)
• Etc.

14. Satellite Footprints
Satellites beam their signal in a straight path to the earth. The satellite focus these microwaves signals onto the specified portions of the earth’s surface to most effectively use the limited power of their transponders. These focused signals create unique beam patterns called “footprints.”
Types of footprints:
- Global beam footprint
- Hemispheric Beam Footprint
- Zone Beam Footprint

15. Satellite Footprints

16. Satellite Footprints

17. Satellite Footprints

18. Satellite Footprints

19. Key Input Data... Bands: Beams: C-Band ( ) Ku-Band ( ) Global ( )
Hemi ( )
Zone ( )
Spot ( )

20. National and Regional Systems
1 Anik, Canada
6 Telecom, France
11 Asiasat, East Asia 12 CS, Japan
2 Morelos, Mexico
7 Kopernikus, Germany 8 Italsat, Italy
3 Panamsat, Americas
13 Palapa, Indonesia
4 Brasilsat, Brazil
9 Arabsat, Arab League
14 Aussat, Australia
5 Eutelsat, Europe
10 Insat, India

21. Early Satellites Satellite Launching Date Country/Organization Type
Height (miles)
Comments
RELAY
1962
USA/RCA & NASA
Active Duplex
4.2/1.7 GHz satellite designed to
carry telephone signals.
SYNCOM
1963
USA/NASA
Active Duplex
Geostationary First Geostationary communication
satellite used to transmit television
signals from the Tokyo Olympics.
MOLNIYA
1965
U.S.S.R
Active Duplex
High altitude
First Soviet communication satellite
elliptical
used a high altitude elliptical orbit.
EARLY
1965
INTELSAT/COMSAT
Active
Geostationary First commercial communication
BIRD
satellite; served the Atlantic ocean
region; capacity to carry 240 voice channels
INTELSAT 2
1966
INTELSAT/COMSAT
Active
Geostationary First multiple access commercial
satellite with multidestination capability
INTELSAT 3
1968
INTELSAT/COMSAT
Active
Geostationary
3 generation designed to carry 1200
voice circuits

22. Early Satellites
Satellite Launching Date Country/Organization Type Height (miles)
Comments
Explorer 1958 USA/NASA Broadcast 110 to 920
Very short life; Noted for re-broadcasting an on-board
taped message from president Eisnhour
ECHO 1960 USA/NASA Passive 1000
100-Foot diameter plastic balloon with an aluminum coating which reflect radio signals
COURIER 1960 Department of defense Store & Repeat
First radio repeater satellite. It accepted and stored upto 360,000 teletype words as it passed
overhead and then broadcast to ground stations further along the orbit; only operated for 17 days.
TELSTAR 1962 USA/AT&T Active Duplex
First satellite to receive and transmit simultaneously; Operated in 4/6
GHz band

23. Early Satellites Satellite Launching Date Country/Organization
Type Height (miles) Comments
INTELSAT INTELSAT/COMSAT
Active Geostationary COMSAT’s 4th generation;
designed to carry voice circuits.
ANIK Canada/Telesat
Active Geostationary World’s first domestic satellite; 5000
voice circuits capacity.
WESTAR 1974 USA/Western Union
Active Geostationary First US domestic satellite

24. Early Satellites • US Navy bounced messages off the moon
• ECHO 1 “balloon” satellite - passive
• ECHO 2 - 2nd passive satellite
• All subsequent satellites used active communications

25. ECHO 1 •
Photo from NASA

26. Early Satellites • Relay • Telstar • Syncom 2 - 4000 miles orbit
-Allowed live transmission across the Atlantic
• Syncom 2
- First Geosynchronous satellite

27. TELSTAR •

28. SYNCOM 2 •

29. Asiasat 2

30. Satellite Visibility

31. Contents • When are satellites visible?
• Factors Affecting the satellite visibility
• Orbit & Altitude Inclination
• Earth Shadow
• Ground Track
• Other factors

32. Limit of Visibility • When Are Satellites Visible?
• Whether or not a satellite is visible to a given observer is dependent upon many factors such as observer location, time of day, satellite altitude, and sky condition. Knowing these details may aid an observer in determining the most favorable times for sightings and is most certainly necessary

33. Factors Affecting Satellite Visibility
• Orbit Altitude And Inclination
• Earth's Shadow
• Ground Track
• Other Factors

34. Orbit Altitude & Inclination
• GEO (~36000 km)
• MEO (~15000 km)
• LEO (~2000 km)
• HEO

35. Earth's Shadow
• The Earth's shadow must also be considered. When shadowed, a satellite is naturally not visible. Such events are dependent upon the satellite's altitude, inclination, the time of year, and the observer's
location

36. Ground Track • Precession of course is not simply a question of
watching for a given satellite at the same time each night. Few satellites have an orbital period which is a simple fraction of one day, the geostationary satellites being the obvious exception. The orbital period is dictated by the satellite's altitude. The higher the altitude, the further it has to travel around the Earth.
• Many satellites in low Earth orbit go through a similar cycle of visibility. The cycle varies with orbital inclination, altitude, and observer location.

37. Other Factors
• Satellite suffers greater air resistance the lower its orbit. This bleeds off the orbital energy, lowering the orbit yet further as the satellite begins to brush the upper atmosphere.
• The forces on the satellite due to the Earth (and Moon, Sun, etc.) vary throughout its orbit giving rise to continual change in the orbit.