Fatima Tufail Khizer Zulfiqar Yasir Chowdhrey Tarique Ali Abdulrafay.
1 Satellite Communications BY ZULFIQAR ALI ARAIN.
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Transcript of 1 Satellite Communications BY ZULFIQAR ALI ARAIN.
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Satellite Communications
BY
ZULFIQAR ALI ARAIN
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Important Milestones (before 1950)Putting the concepts together
1600 Tycho Brache’s experimental observations on planetary motion.
1609-1619 Kepler’s laws on planetary motion
1926 First liquid propellant rocket lauched by R.H. Goddard in the US.
1927 First transatlantic radio link communication
1942 First successful launch of a V-2 rocket in Germany.
1945 Arthur Clarke publishes his ideas on geostationary satellites for worldwide communications (GEO concept).
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V2 Rocket
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Important Milestones (1950’s)Putting the pieces together
1956 - Trans-Atlantic cable opened (about 12 telephone channels – operator).
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).
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Sputnik - I
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Explorer - I
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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).
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ECHO I
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Telstar I
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Intelsat I
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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.
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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).
1989-90 Global mobile communication service extended to land mobile and aeronautical use (Inmarsat)
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Important Milestones (1990’s)
1990-95: - 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.
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Iridium
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INTRODUCTION TO ORBITS
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Main orbit types:
LEO 500 -1000 km
GEO 36,000 km
MEO 5,000 – 15,000 km
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USEFUL ORBITS 1: GEOSTATIONARY ORBIT
In the equatorial planeOrbital Period = 23 h 56 min. 4.091 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, = 42,164.57 km
NOTE: Radius = orbital height + radius of the earth
Average radius of earth = 6,378.14 km
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USEFUL ORBITS 2:
Low Earth Orbit (>250 km); T 92 minutesPolar (Low Earth) Orbit; earth rotates about 23o each orbit; useful for surveillanceSun Synchronous Orbit(example, Tiros-N/NOAA satellites used for search and rescue operations)8-hour and 12-hour orbitsMolniya orbit (Highly Elliptical Orbit (HEO); T 11h 38 min; highly eccentric orbit; inclination 63.4 degrees
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Orbital Velocities and Periods
Satellite Orbital Orbital Orbital System Height (km) Velocity (km/s) Period
h min s
INTELSAT 35,786.43 3.0747 23 56 4.091
ICO-Global 10,255 4.8954 5 55 48.4
Skybridge 1,469 7.1272 1 55 17.8
Iridium 780 7.4624 1 40 27.0
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Coverage vs. Altitude
Satellite Altitude (km)
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LEO, MEO and GEO Orbit Periods
0.0
5.0
10.0
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20.0
25.0
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0 5000 10000 15000 20000 25000 30000 35000 40000
Altitude [km]
Ho
urs
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Minimum Delay for two hops
0.0
50.0
100.0
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200.0
250.0
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0 5000 10000 15000 20000 25000 30000 35000 40000
Altitude [km]
De
lay
[ms
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F1
(GravitationalForce)
v (velocity)
Why do satellites stay moving and in orbit?
F2
(Inertial-Centrifugal Force)
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Current Developments and Future Trends
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Bigger, heavier, GEO satellites with multiple roles
More direct broadcast TV and Radio satellites
Expansion into Ka, Q, V bands (20/30, 40/50 GHz)
Massive growth in data services fueled by Internet
Mobile services: May be broadcast services rather than point to pointMake mobile services a successful business?
Current Trends in Satellite Communications
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Growth requires new frequency bands
Propagation through rain and clouds becomes a problem as RF frequency is increased
C-band (6/4 GHz) Rain has little impact 99.99% availability is possible
Ku-band (10-12 GHz) Link margin of 3 dB needed for 99.8% availability
Ka-band (20 - 30 GHz) Link margin of 6 dB needed for 99.6% availability
The Future for Satellite Communications – 1
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Low cost phased array antennas for mobiles are needed
Mobile systems are limited by use of omni-
directional antennas
A self-phasing, self-steering phased array
antenna with 6 dB gain can quadruple the
capacity of a system
Directional antennas allow frequency re-use
The Future for Satellite Communications - 2