1. Communication Satellite

2. References
Joe Montana, “Introduction to Satellite Communication,” George Mason University,
Tanenbaum, Computer Networks, 4th edition, Prentice Hall.

3. Important Milestones (1950’s) Putting the pieces together
1957 First man-made satellite launched by former USSR (Sputnik, LEO).
1958 First US satellite launched (SCORE). First voice communication established via satellite (LEO, lasted 35 days in orbit after batteries failed).

4. Sputnik - I

5. Important Milestones (1960’s) First satellite communications
1960 First passive communication satellite launched into space (Large balloons, Echo I and II).
1962: First non-government active communication satellite launched Telstar I (MEO).
1963: First satellite launched into geostationary orbit Syncom 1 (comms. failed).
1964: International Telecomm. Satellite Organization (INTELSAT) created.
1965 First communications satellite launched into geostationary orbit for commercial use Early Bird (re-named INTELSAT 1).

6. ECHO I

7. Telstar I

8. Intelsat I

9. Important Milestones (1970’s) GEO applications development
1972 First domestic satellite system operational (Canada). INTERSPUTNIK founded.
1975 First successful direct broadcast experiment (one year duration; USA-India).
1977 A plan for direct-to-home satellite broadcasting assigned by the ITU in regions 1 and 3 (most of the world except the Americas).
1979 International Mobile Satellite Organization (Inmarsat) established.

10. Important Milestones (1980’s) GEO applications expanded
1981 First reusable launch vehicle flight.
1982 International maritime communications made operational.
1983 ITU direct broadcast plan extended to region 2.
1984 First direct-to-home broadcast system operational (Japan).
1987 Successful trials of land-mobile communications (Inmarsat).
Global mobile communication service extended to land mobile and aeronautical use (Inmarsat)

11. Important Milestones (1990’s):
- Several organizations propose the use of non-geostationary (NGSO) satellite systems for mobile communications.
- Continuing growth of VSATs* around the world.
- Spectrum allocation for non-GEO systems.
- Continuing growth of direct broadcast systems. DirectTV created.
1997:
- Launch of first batch of LEO for hand-held terminals (Iridium).
- Voice service telephone-sized desktop and paging service pocket size mobile terminals launched (Inmarsat).
1998: Iridium initiates services.
1999: Globalstar Initiates Service.
2000: ICO initiates Service. Iridium fails and system is sold to Boeing.
* VSAT - Very Small Aperture Terminal - small, software-driven earth stations (typically 3-6 feet) used for the transmission of data, video, or voice via satellite.

12. Iridium

13. Communication Satellites Classified Based on Main orbit types
Geostationary Satellites
Medium-Earth Orbit Satellites
Low-Earth Orbit Satellites

14. Main orbit types GEO 36,000 km MEO 5,000 – 15,000 km LEO 500 -1000 km

15. Communication Satellites
Communication satellites and some of their properties, including altitude above the earth, round-trip delay time and number of satellites needed for global coverage.

16. Satellite Altitude (km)
Coverage vs. Altitude
Satellite Altitude (km)

17. LEO, MEO and GEO Orbit Periods

18. Minimum Delay for two hops

19. GEO (GEOSTATIONARY ORBIT)
In the equatorial plane
Orbital Period = 23 h 56 min s = one Sidereal Day (defined as one complete rotation relative to the fixed stars)
Satellite appears to be stationary over a point on the equator to an observer
Radius of orbit, r, = 42, km
NOTE: Radius = orbital height + radius of the earth
Average radius of earth = 6, km

20. Characteristic of Communication Satellite on the GEO
Synchronize to the earth's rotation period.
T=23h 56min 4.091s
Orbit altitude
H=36,000km
One satellite can cover 40% of the earth
All the surface of the earth can be covered by three satellites.
Fixed propagation delay
D=250msec~270ms

21. GEO Satellite Applications
Current
GEO Satellite Applications
Broadcasting - mainly TV at present
DirecTV, PrimeStar, etc.
Point to Multi-point communications
VSAT, Video distribution for Cable TV
Mobile Services
Motient (former American Mobile Satellite), INMARSAT, etc.

22. Satellite Navigation: GPS by MEO Satellite System
GPS is a medium earth orbit (MEO) satellite system
GPS satellites broadcast pulse trains with very accurate time signals
A receiver able to “see” four GPS satellites can calculate its position within 30 m anywhere in world
“You never need be lost again”
Every automobile and cellular phone will eventually have a GPS location read-out

23. LEO (Low-Earth Orbit) Satellites Iridium
(a) The Iridium satellites from six necklaces around the earth.
(b) 1628 moving cells cover the earth.

24. LEO Satellites in year 2000
Several new systems are just starting service
Circular or inclined orbit with < 1400 km altitude
Satellite travels across sky from horizon to horizon in minutes
Earth stations must track satellite or have omni-directional antennas
Constellation of satellites is needed for continuous communication.
Handoff needed.

25. Satellite System Elements
Space Segment
Satellite
Coverage Region
Earth Stations
SCC
TT&C Ground Station
Ground Segment

26. Space Segment Satellite Launching Phase Transfer Orbit Phase
Deployment
Operation
TT&C - Tracking Telemetry and Command Station: Establishes a control and monitoring link with satellite. Tracks orbit distortions and allows correction planning. Distortions caused by irregular gravitational forces from non-spherical Earth and due to the influence of Sun and Moon forces.
SSC - Satellite Control Center, a.k.a.:
OCC - Operations Control Center
SCF - Satellite Control Facility
Provides link signal monitoring for Link Maintenance and Interference monitoring.
Retirement Phase

27. Ground Segment Collection of facilities, users and applications.
FSS – Fixed Satellite Service
MSS – Mobile Satellite Service
Earth Station = Satellite Communication Station (air, ground or sea, fixed or mobile).

28. Communication Satellites (2)
The principal satellite bands.

29. Current Trends in Satellite Communications
Bigger, heavier, GEO satellites with multiple roles
More direct broadcast TV and Radio satellites
Expansion into Ka, Q, V bands (20/30, 30/50, 46/56 GHz)
Massive growth in data services fueled by Internet
Mobile services:
May be broadcast services rather than point to point
Make mobile services a successful business?