Introduction to satellite Communications Lecture (11) 9/17/2015 1 Dr. Hassan Yousif

Introduction to satellite Communications

Lecture (11)

04/19/23 1Dr. Hassan Yousif

What is a satellite?

Satellite is an object launched to orbit earth or another celestial body.



How it works

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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)



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.


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)

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.04/19/23 9Dr. Hassan Yousif

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.


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


Satellite System Elements

12

Space Segment

Satellite

TT&C Ground Station

Ground Segment

Earth Stations

Coverage Region

SCC

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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 Phase1404/19/23 Dr. Hassan Yousif

Satellite Subsystems

• Communications– Antennas– Transponders

• Common Subsystem (Bus Subsystem)– Telemetry/Command (TT&C)– Satellite Control (antenna pointing,

attitude)– Propulsion– Electrical Power– Structure– Thermal Control


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


Frequency Allocationsfor Satellite Services

• To facilitate frequency planning, the world is divided into three regions:Region 1: Europe, AfricaRegion 2: North and South

America and GreenlandRegion 3: Asia, Australia, and the

southwest Pacific


Intelsat 10 at 68.5º E Africa footprint.


Telestar 12 footprint


NileSat footprint


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


Frequency band designations


Frequency Frequency range range (GHz)(GHz)

BandBand ServiceServiceFrequency Frequency

range range (GHz)(GHz)

BandBand

0.1 – 0.30.1 – 0.3 VHFVHFNavigation/ Navigation/

WeatherWeather18 – 2718 – 27 KK

0.3 – 10.3 – 1 UHFUHF 27 – 4027 – 40 KaKa

1 – 21 – 2 LL MobileMobile 40 – 7540 – 75 VV

2 – 42 – 4 SS 75 – 11075 – 110 WW

4 – 84 – 8 CC FSSFSS110 - 300110 - 300

mmmm

8 -128 -12 XX 300 - 3000300 - 3000 μμmm

12 – 1812 – 18 KuKu DBS/ FSSDBS/ FSS

ITU Frequency Band Designation

Frequency Frequency rangerange

banband d namnamee

Frequency Frequency rangerange

banband d namnamee

3-30 KHz3-30 KHz VLFVLF 30-300 MHz30-300 MHz VHFVHF

30-300 KHz30-300 KHz LFLF 300-3000 300-3000 MHzMHz

UHFUHF

300-3000 300-3000 KHzKHz

MFMF 3-30 GHz3-30 GHz SHFSHF

3-30 MHz3-30 MHz HFHF 30-300 GHz30-300 GHz EHFEHF04/19/23 23Dr. Hassan Yousif

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Intelsat V

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Intelsat VI

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An Earth Observation Sat (EOS)

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A communication sat.

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Important Terminologies

1. Apogee (point of farthest approach)2. Perigee (point of closest approach)3. Line of Apsides4. Ascending node5. Descending node6. Line of nodes7. inclination

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Apogee & Perigee heights

The Length of the radius vectors at the apogee and perigee:

ra = a (1 + e)

rp = a (1 - e)

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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



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


The evolution of Intelsat satellite

Early birdIntelsat

VIntelsat

VIIntelsat

VII

First Launch 1965 1980 1989 1992

Satellite mass in orbit (kg) 38.5 900 1870 1425

Prime Power (W) 40 1200 2200 3900

Number of transponders 2 30 48 36

Total Bandwidth (MHz) 50 21372137 35203520

Telephone Channel capacity: All Analog All Digital

480 3300180,000

48000270,000

38000200,000


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Introduction to satellite Communications Lecture (11) 9/17/2015 1 Dr. Hassan Yousif