08tl satellite history and some diagam

8/7/2019 08TL satellite history and some diagam

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Satellite Communications

BY

ZULFIQAR ALI ARAIN


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Important Milestones (before 1950)

Putting the concepts together

1600 Tycho Braches experimental observations on planetary motion.

1609-1619 Keplers 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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Sputnik - I


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Explorer - I


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Important Milestones (1960s)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 (1970s)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 (1980s)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 (1990s)

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 sizemobile 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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USEFULORBITS1:

GEOSTATIONARYORBIT

In the equatorial plane

Orbital Period = 23 h 56 min. 4.091 s

= one Sidereal Day(definedas one complete rotation relative to the fixedstars)

Satellite appears to be stationaryover a

point on the equator to an observerRadius 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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USEFULORBITS2:

Low Earth Orbit (>250 km); T } 92 minutes

Polar (Low Earth) Orbit; earth rotates about23o each orbit; useful for surveillance

Sun Synchronous Orbit(example, Tiros-N/NOAA satellites used for search and rescueoperations)

8-hour and 12-hour orbits

Molniya 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 GEOOrbit Periods

0.0

5.0

10.0

15.0

20.0

25.0

30.0

0 5000 10000 15000 20000 25000 30000 35000 40000

Altitude [km]

Hours


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Minimum Delay for two hops

0.0

50.0

100.0

150.0

200.0

250.0

300.0

0 5000 10000 15000 20000 25000 30000 35000 40000

Altitude [km]

Delay[ms]


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F1(Gravitational

Force)

v (velocity)

Why do satellites stay moving

and in orbit?

F2

(Inertial-Centrifugal

Force)


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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 point

Make 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 increasedC-band (6/4 GHz) Rain has little impact

99.99% availability is possible

Ku-band (10-12 GHz) Link margin ofu 3 dB needed

for 99.8% availability

Ka-band (20 - 30 GHz) Link margin ofu 6 dB needed

for 99.6% availability

The Future for Satellite

Communications 1


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Low cost phased arrayantennas for mobiles are

neededMobile 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

08tl satellite history and some diagam

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