Satellite Communications

Introduction

Satellites are specifically made fortelecommunication purpose.

They are used formobile applications such as communication to ships, vehicles, planes hand-held terminals and TV and radio broadcasting

Satellites are specifically made fortelecommunication purpose.

They are used formobile applications such as communication to ships, vehicles, planes hand-held terminals and TV and radio broadcasting

Introduction

They are responsible for providing theseservices to an assigned region (area) on theearth.

The power and bandwidth of these satellitesdepend upon the preferred size of thefootprint, complexity of the traffic controlprotocol schemes and the cost of groundstations.

They are responsible for providing theseservices to an assigned region (area) on theearth.

The power and bandwidth of these satellitesdepend upon the preferred size of thefootprint, complexity of the traffic controlprotocol schemes and the cost of groundstations.

Introduction

A satellite works most efficiently when thetransmissions are focused with a desiredarea.

When the area is focused, then the emissionsdont go outside that designated area andthus minimizing the interference to the othersystems. This leads more efficient spectrumusage

A satellite works most efficiently when thetransmissions are focused with a desiredarea.

When the area is focused, then the emissionsdont go outside that designated area andthus minimizing the interference to the othersystems. This leads more efficient spectrumusage

Introduction

Satellites antenna patterns play an importantrole and must be designed to best cover thedesignated geographical area (which isgenerally irregular in shape).

Satellites should be designed by keeping inmind its usability for short and long termeffects throughout its life time.

Satellites antenna patterns play an importantrole and must be designed to best cover thedesignated geographical area (which isgenerally irregular in shape).

Satellites should be designed by keeping inmind its usability for short and long termeffects throughout its life time.

Introduction

The earth station should be in a position tocontrol the satellite

If it drifts from its orbit it is subjected to anykind of drag from the external forces.

The earth station should be in a position tocontrol the satellite

If it drifts from its orbit it is subjected to anykind of drag from the external forces.

BASICS Satellites orbit around the earth. Depending on the application, these orbitscan be circular or elliptical.

Satellites in circular orbits always keep thesame distance to the earths surface followinga simple law:

Satellites orbit around the earth. Depending on the application, these orbitscan be circular or elliptical.

Satellites in circular orbits always keep thesame distance to the earths surface followinga simple law:

BASICS The attractive force Fg of the earth due to gravityequalsmg (R/r) 2 The centrifugal force Fc trying to pull the satellite awayequalsmr2 The variables have the following meaning: m is the mass of the satellite; R is the radius of earth with R = 6,370 km; r is the distance of the satellite to the centre of theearth; g is the acceleration of gravity with g = 9.81 m/s2; is the angular velocity with = 2f, f is thefrequency of the rotation.

The attractive force Fg of the earth due to gravityequalsmg (R/r) 2 The centrifugal force Fc trying to pull the satellite awayequalsmr2 The variables have the following meaning: m is the mass of the satellite; R is the radius of earth with R = 6,370 km; r is the distance of the satellite to the centre of theearth; g is the acceleration of gravity with g = 9.81 m/s2; is the angular velocity with = 2f, f is thefrequency of the rotation.

BASICS To keep the satellite in a stable circular orbit,the following equation must hold:

Fg = Fc i.e., both forces must be equal. Solving the equation for the distance r of thesatellite to the centre of the earth results inthe following equation:

The distance r = (gR2/(2f)2)1/3

To keep the satellite in a stable circular orbit,the following equation must hold:

Fg = Fc i.e., both forces must be equal. Solving the equation for the distance r of thesatellite to the centre of the earth results inthe following equation:

The distance r = (gR2/(2f)2)1/3

BASICS The distance r = (gR2/(2f)2)1/3

From the above equation it can be concludedthat the distance of a satellite to the earthssurface depends on its rotation frequency.

The distance r = (gR2/(2f)2)1/3

From the above equation it can be concludedthat the distance of a satellite to the earthssurface depends on its rotation frequency.

BASICS Important parameters in satellitecommunication are the inclination andelevation angles.

Important parameters in satellitecommunication are the inclination andelevation angles.

BASICS The inclination angle is defined between theequatorial plane and the plane described bythe satellite orbit.

An inclination angle of 0 degrees means thatthe satellite is exactly above the equator.

If the satellite does not have a circular orbit,the closest point to the earth is called theperigee.

The inclination angle is defined between theequatorial plane and the plane described bythe satellite orbit.

An inclination angle of 0 degrees means thatthe satellite is exactly above the equator.

If the satellite does not have a circular orbit,the closest point to the earth is called theperigee.

BASICS

BASICS

APPLICATIONS OF SATELLITES

Weather Forecasting Certain satellites are specifically designed to monitorthe climatic conditions of earth. They continuously monitor the assigned areas of earthand predict the weather conditions of that region. This is done by taking images of earth from thesatellite. These images are transferred using assignedradio frequency to the earth station. Earth Station: its a radio station located on the earthand used for relaying signals from satellites. These satellites are exceptionally useful in predictingdisasters like hurricanes, and monitor the changes inthe Earth's vegetation, sea state, ocean color, and icefields.

Certain satellites are specifically designed to monitorthe climatic conditions of earth. They continuously monitor the assigned areas of earthand predict the weather conditions of that region. This is done by taking images of earth from thesatellite. These images are transferred using assignedradio frequency to the earth station. Earth Station: its a radio station located on the earthand used for relaying signals from satellites. These satellites are exceptionally useful in predictingdisasters like hurricanes, and monitor the changes inthe Earth's vegetation, sea state, ocean color, and icefields.

Radio and TV Broadcast These dedicated satellites are responsible formaking 100s of channels across the globeavailable for everyone.

They are also responsible for broadcasting livematches, news, world-wide radio services.

These satellites require a 30-40 cm sized dishto make these channels available globally.

These dedicated satellites are responsible formaking 100s of channels across the globeavailable for everyone.

They are also responsible for broadcasting livematches, news, world-wide radio services.

These satellites require a 30-40 cm sized dishto make these channels available globally.

Military Satellites These satellites are often used for gatheringintelligence, as a communications satelliteused for military purposes, or as a militaryweapon.

A satellite by itself is neither military nor civil. It is the kind of payload it carries that enablesone to arrive at a decision regarding itsmilitary or civilian character.

These satellites are often used for gatheringintelligence, as a communications satelliteused for military purposes, or as a militaryweapon.

A satellite by itself is neither military nor civil. It is the kind of payload it carries that enablesone to arrive at a decision regarding itsmilitary or civilian character.

Navigation Satellites The system allows for precise localization world-wide, and with some additional techniques, theprecision is in the range of some meters.

Ships and aircraft rely on GPS as an addition totraditional navigation systems.

Many vehicles come with installed GPS receivers. This system is also used, e.g., for fleetmanagement of trucks or for vehicle localizationin case of theft.

The system allows for precise localization world-wide, and with some additional techniques, theprecision is in the range of some meters.

Ships and aircraft rely on GPS as an addition totraditional navigation systems.

Many vehicles come with installed GPS receivers. This system is also used, e.g., for fleetmanagement of trucks or for vehicle localizationin case of theft.

Global Telephone One of the first applications of satellites forcommunication was the establishment of internationaltelephone backbones. Instead of using cables it was sometimes faster tolaunch a new satellite. But, fiber optic cables are still replacing satellitecommunication across long distance as in fiber opticcable, light is used instead of radio frequency, hencemaking the communication much faster (and of course,reducing the delay caused due to the amount ofdistance a signal needs to travel before reaching thedestination.).

One of the first applications of satellites forcommunication was the establishment of internationaltelephone backbones. Instead of using cables it was sometimes faster tolaunch a new satellite. But, fiber optic cables are still replacing satellitecommunication across long distance as in fiber opticcable, light is used instead of radio frequency, hencemaking the communication much faster (and of course,reducing the delay caused due to the amount ofdistance a signal needs to travel before reaching thedestination.).

Global Telephone Using satellites, to typically reach a distanceapproximately 10,000 kms away, the signalneeds to travel almost 72,000 kms, that is,sending data from ground to satellite and(mostly) from satellite to another location onearth.

This causes substantial amount of delay andthis delay becomes more prominent for usersduring voice calls.

Using satellites, to typically reach a distanceapproximately 10,000 kms away, the signalneeds to travel almost 72,000 kms, that is,sending data from ground to satellite and(mostly) from satellite to another location onearth.

This causes substantial amount of delay andthis delay becomes more prominent for usersduring voice calls.

Connecting Remote Areas Due to their geographical location manyplaces all over the world do not have directwired connection to the telephone network orthe internet (e.g., researchers on Antarctica)or because of the current state of theinfrastructure of a country.

Here the satellite provides a completecoverage and (generally) there is one satellitealways present across a horizon.

Due to their geographical location manyplaces all over the world do not have directwired connection to the telephone network orthe internet (e.g., researchers on Antarctica)or because of the current state of theinfrastructure of a country.

Here the satellite provides a completecoverage and (generally) there is one satellitealways present across a horizon.

Global Mobile Communication The basic purpose of satellites for mobile

communication is to extend the area of coverage. Cellular phone systems, such as AMPS and GSM (and

their successors) do not cover all parts of a country. Areas that are not covered usually have low population

where it is too expensive to install a base station. With the integration of satellite communication,

however, the mobile phone can switch to satellitesoffering world-wide connectivity to a customer.

The basic purpose of satellites for mobilecommunication is to extend the area of coverage.

Cellular phone systems, such as AMPS and GSM (andtheir successors) do not cover all parts of a country.

Areas that are not covered usually have low populationwhere it is too expensive to install a base station.

With the integration of satellite communication,however, the mobile phone can switch to satellitesoffering world-wide connectivity to a customer.

Global Mobile Communication Satellites cover a certain area on the earth. This area istermed as a footprint of that satellite. Within the footprint, communication with thatsatellite is possible for mobile users. These users communicate using a Mobile-User-Link(MUL). The base-stations communicate with satellitesusing a Gateway-Link (GWL). Sometimes it becomes necessary for satellite to createa communication link between users belonging to twodifferent footprints. Here the satellites send signals to each other and thisis done using Inter-Satellite-Link (ISL).

Satellites cover a certain area on the earth. This area istermed as a footprint of that satellite. Within the footprint, communication with thatsatellite is possible for mobile users. These users communicate using a Mobile-User-Link(MUL). The base-stations communicate with satellitesusing a Gateway-Link (GWL). Sometimes it becomes necessary for satellite to createa communication link between users belonging to twodifferent footprints. Here the satellites send signals to each other and thisis done using Inter-Satellite-Link (ISL).

FREQUENCY ALLOCATION FOR SATELLITE Allocation of frequencies to satellite services isa complicated process which requiresinternational coordination and planning. Thisis done as per the InternationalTelecommunication Union (ITU). To implementthis frequency planning, the world is dividedinto three regions:

Allocation of frequencies to satellite services isa complicated process which requiresinternational coordination and planning. Thisis done as per the InternationalTelecommunication Union (ITU). To implementthis frequency planning, the world is dividedinto three regions:

FREQUENCY ALLOCATION FORSATELLITE

Region1: Europe, Africa and Mongolia Region 2: North and South America andGreenland

Region 3: Asia (excluding region 1 areas),Australia and south-west Pacific.

Within these regions, the frequency bands areallocated to various satellite services. Some ofthem are listed below.

Region1: Europe, Africa and Mongolia Region 2: North and South America andGreenland

Region 3: Asia (excluding region 1 areas),Australia and south-west Pacific.

Within these regions, the frequency bands areallocated to various satellite services. Some ofthem are listed below.

FREQUENCY ALLOCATION FORSATELLITE

Fixed satellite service: Provides Links for existing TelephoneNetworks used for transmitting television signals to cablecompanies Broadcasting satellite service: Provides Direct Broadcast tohomes. E.g. Live Cricket matches etc Mobile satellite services: This includes services for:

Land Mobile Maritime Mobile Aeronautical mobile Navigational satellite services : Include Global Positioningsystems Meteorological satellite services: They are often used toperform Search and Rescue service

Fixed satellite service: Provides Links for existing TelephoneNetworks used for transmitting television signals to cablecompanies Broadcasting satellite service: Provides Direct Broadcast tohomes. E.g. Live Cricket matches etc Mobile satellite services: This includes services for:

Land Mobile Maritime Mobile Aeronautical mobile Navigational satellite services : Include Global Positioningsystems Meteorological satellite services: They are often used toperform Search and Rescue service

FREQUENCY ALLOCATION FORSATELLITE

Below are the frequencies allocated to these satellites: Frequency Band (GHZ) Designations: VHF: 0.1-0.3 UHF: 0.3-1.0 L-band: 1.0-2.0 S-band: 2.0-4.0 C-band: 4.0-8.0 X-band: 8.0-12.0 Ku-band: 12.0-18.0 (Ku is Under K Band) Ka-band: 18.0-27.0 (Ka is Above K Band) V-band: 40.0-75.0 W-band: 75-110 Mm-band: 110-300 m-band: 300-3000

Below are the frequencies allocated to these satellites: Frequency Band (GHZ) Designations: VHF: 0.1-0.3 UHF: 0.3-1.0 L-band: 1.0-2.0 S-band: 2.0-4.0 C-band: 4.0-8.0 X-band: 8.0-12.0 Ku-band: 12.0-18.0 (Ku is Under K Band) Ka-band: 18.0-27.0 (Ka is Above K Band) V-band: 40.0-75.0 W-band: 75-110 Mm-band: 110-300 m-band: 300-3000

FREQUENCY ALLOCATION FORSATELLITE

Based on the satellite service, following are thefrequencies allocated to the satellites:

Frequency Band (GHZ) Designations: VHF: 0.1-0.3 ---Mobile & Navigational Satellite Services L-band: 1.0-2.0 --- Mobile & Navigational Satellite

Services C-band: 4.0-8.0 --- Fixed Satellite Service X band:8.0-12.0 --- Military Satellite Service Ku-band: 12.0-18.0 --- Direct Broadcast Satellite

Services

Based on the satellite service, following are thefrequencies allocated to the satellites:

Frequency Band (GHZ) Designations: VHF: 0.1-0.3 ---Mobile & Navigational Satellite Services L-band: 1.0-2.0 --- Mobile & Navigational Satellite

Services C-band: 4.0-8.0 --- Fixed Satellite Service X band:8.0-12.0 --- Military Satellite Service Ku-band: 12.0-18.0 --- Direct Broadcast Satellite

Services

What is a Satellite ? A celestial body In astronomical term, e.g. moon A space vehicle launched by humans and orbits theearth or another celestial body In aerospace terms

Communication Satellite provides communicationand other services to variety of consumers It is amicrowave repeater in the sky A satellite radio repeater is called a transponder A satellite may have one to many transponders

A celestial body In astronomical term, e.g. moon A space vehicle launched by humans and orbits theearth or another celestial body In aerospace terms

Communication Satellite provides communicationand other services to variety of consumers It is amicrowave repeater in the sky A satellite radio repeater is called a transponder A satellite may have one to many transponders

What is a Satellite Systems ? A Satellite System may consist of :

one or more satellite space vehicles, a ground based control earth station, and a network of user earth stations that provides theinterface facilities for the transmission and reception ofterrestrial communications traffic through the satellitesystems.

Transmissions to and from the satellites arecategorized as either bus or payload.

The payload is the actual user information conveyedthrough the system.

The bus includes control mechanisms that supportthe payload operation

A Satellite System may consist of : one or more satellite space vehicles, a ground based control earth station, and a network of user earth stations that provides theinterface facilities for the transmission and reception ofterrestrial communications traffic through the satellitesystems.

Transmissions to and from the satellites arecategorized as either bus or payload.

The payload is the actual user information conveyedthrough the system.

The bus includes control mechanisms that supportthe payload operation

Why Satellites for Communications? Greater Coverage Relatively Larger Capacity Faster Deployment Lower Cost Solution for many scenarios

Greater Coverage Relatively Larger Capacity Faster Deployment Lower Cost Solution for many scenarios

Passive and Active Satellites

Passive Satellite Simplest type of satellite is a passive reflector It simply bounces signals from one place to another. It reflects signals back to earth as there are no gain

devices on board to amplify or modify the signals Moon became the first passive satellite in 1954 when

the U.S Navy successfully transmitted the first messageover an Earth-to-moon-to-Earth communicationsystem.

But moon proved to be unreliable communicationsatellite as it is above the horizon only half of thetime and its position relative to earth is constantlychanging.

Simplest type of satellite is a passive reflector It simply bounces signals from one place to another. It reflects signals back to earth as there are no gain

devices on board to amplify or modify the signals Moon became the first passive satellite in 1954 when

the U.S Navy successfully transmitted the first messageover an Earth-to-moon-to-Earth communicationsystem.

But moon proved to be unreliable communicationsatellite as it is above the horizon only half of thetime and its position relative to earth is constantlychanging.

Active Satellite It is capable of receiving, amplifying,reshaping, regenerating and retransmittingthe information

Has sophisticated electronic equipment on-board.

It is capable of receiving, amplifying,reshaping, regenerating and retransmittingthe information

Has sophisticated electronic equipment on-board.

Advantage of Passive Satellite No sophisticated electronic equipment onboard.

Radio beacon transmitters are required fortracking and ranging purposes.

A beacon is a continuously transmitted un-modulated carrier that an earth station canlock on to and use to determine the exactlocation of a satellite so the earth station canalign its antennas.

No sophisticated electronic equipment onboard.

Radio beacon transmitters are required fortracking and ranging purposes.

A beacon is a continuously transmitted un-modulated carrier that an earth station canlock on to and use to determine the exactlocation of a satellite so the earth station canalign its antennas.

Disadvantage of Passive Satellite Inefficient use of transmitted power

As little as 1 part in every 1018 of an earthstations transmitted power is actuallyreturned to earth station receiving antennas

Inefficient use of transmitted power

As little as 1 part in every 1018 of an earthstations transmitted power is actuallyreturned to earth station receiving antennas

TYPES OF SATELLITES(BASED ON ORBITS)

Geostationary or geosynchronous earth orbit (GEO)

GEO satellites are synchronous with respect toearth.

Three satellites are sufficient. footprint is covering almost 1/3rd of the Earth Circular Orbits Lifetime expectancy of these satellites is 15years

GEO satellites are synchronous with respect toearth.

Three satellites are sufficient. footprint is covering almost 1/3rd of the Earth Circular Orbits Lifetime expectancy of these satellites is 15years

Three conditions which lead togeostationary satellites

1) The satellite should be placed 37,786 kms(approximated to 36,000 kms) above thesurface of the earth.

2) These satellites must travel in the rotationalspeed of earth, and in the direction of motionof earth, that is eastward.

3) The inclination of satellite with respect toearth must be 0 degrees.

1) The satellite should be placed 37,786 kms(approximated to 36,000 kms) above thesurface of the earth.

2) These satellites must travel in the rotationalspeed of earth, and in the direction of motionof earth, that is eastward.

3) The inclination of satellite with respect toearth must be 0 degrees.

Geostationary or geosynchronous earth orbit(GEO)

Geostationary satellite in practice is termed asgeosynchronous as there are multiple factorswhich make these satellites shift from theideal geostationary condition.

Geostationary satellite in practice is termed asgeosynchronous as there are multiple factorswhich make these satellites shift from theideal geostationary condition.

Geostationary or geosynchronousearth orbit (GEO)

1) Gravitational pull of sun and moon makesthese satellites deviate from their orbit.

2) These satellites experience the centrifugalforce due to the rotation of Earth, makingthem deviate from their orbit.

3) The non-circular shape of the earth leads tocontinuous adjustment of speed of satellitefrom the earth station.

1) Gravitational pull of sun and moon makesthese satellites deviate from their orbit.

2) These satellites experience the centrifugalforce due to the rotation of Earth, makingthem deviate from their orbit.

3) The non-circular shape of the earth leads tocontinuous adjustment of speed of satellitefrom the earth station.

Applications

These satellites are used For TV and radio broadcast, For weather forecast and also, as backbones for the telephone networks.

These satellites are used For TV and radio broadcast, For weather forecast and also, as backbones for the telephone networks.

Disadvantages of GEO

Northern or southern regions of the Earth (poles) havemore problems receiving these satellites due to thelow elevation Shading of the signals is seen in cities due to highbuildings limit transmission quality.

The transmit power needed is relatively high whichcauses problems for battery powered devices

Northern or southern regions of the Earth (poles) havemore problems receiving these satellites due to thelow elevation Shading of the signals is seen in cities due to highbuildings limit transmission quality.

The transmit power needed is relatively high whichcauses problems for battery powered devices

Disadvantages of GEO The biggest problem for voice and also datacommunication is without having any handovers,the signal has to at least travel 72,000 kms.

Due to the large footprint, either frequenciescannot be reused or the GEO satellite needsspecial antennas focusing on a smaller footprint.

Transferring a GEO into orbit is very expensive.

The biggest problem for voice and also datacommunication is without having any handovers,the signal has to at least travel 72,000 kms.

Due to the large footprint, either frequenciescannot be reused or the GEO satellite needsspecial antennas focusing on a smaller footprint.

Transferring a GEO into orbit is very expensive.

Low Earth Orbit (LEO) satellites These satellites are placed 500-1500 kmsabove the surface of the earth.

As LEOs circulate on a lower orbit, hence theyexhibit a much shorter period that is 95 to 120minutes.

LEO systems try to ensure a high elevation forevery spot on earth to provide a high qualitycommunication link.

These satellites are placed 500-1500 kmsabove the surface of the earth.

As LEOs circulate on a lower orbit, hence theyexhibit a much shorter period that is 95 to 120minutes.

LEO systems try to ensure a high elevation forevery spot on earth to provide a high qualitycommunication link.

Low Earth Orbit (LEO) satellites Using advanced compression schemes, transmissionrates of about 2,400 bit/s can be enough for voicecommunication. LEOs even provide this bandwidth formobile terminalswith Omni-directional antennas using low transmitpower in the range of 1W. The delay for packets delivered via a LEO is relativelylow (approx 10 ms). The delay is comparable to long-distance wired connections (about 510 ms). Smaller footprints of LEOs allow for better frequencyreuse, similar to the concepts used for cellularnetworks. LEOs can provide a much higher elevation in PolarRegions and so better global coverage.

Using advanced compression schemes, transmissionrates of about 2,400 bit/s can be enough for voicecommunication. LEOs even provide this bandwidth formobile terminalswith Omni-directional antennas using low transmitpower in the range of 1W. The delay for packets delivered via a LEO is relativelylow (approx 10 ms). The delay is comparable to long-distance wired connections (about 510 ms). Smaller footprints of LEOs allow for better frequencyreuse, similar to the concepts used for cellularnetworks. LEOs can provide a much higher elevation in PolarRegions and so better global coverage.

Applications - LEO

These satellites are mainly used in remotesensing and providing mobile communicationservices

These satellites are mainly used in remotesensing and providing mobile communicationservices

Disadvantages - LEO Many satellites needed if global coverage is to bereached 50200 or even more satellites in orbit. The short time of visibility with a high elevationrequires additional mechanisms for connectionhandover between different satellites. The high number of satellites combined with thefast movements resulting in a high complexity ofthe whole satellite system.

Many satellites needed if global coverage is to bereached 50200 or even more satellites in orbit. The short time of visibility with a high elevationrequires additional mechanisms for connectionhandover between different satellites. The high number of satellites combined with thefast movements resulting in a high complexity ofthe whole satellite system.

Disadvantages - LEO Short lifetime of about five to eight years dueto atmospheric drag and radiation from innerVan Allen belt1

Assuming 48 satellites and a lifetime of eightyears, a new satellite would be needed everytwo months.

Short lifetime of about five to eight years dueto atmospheric drag and radiation from innerVan Allen belt1

Assuming 48 satellites and a lifetime of eightyears, a new satellite would be needed everytwo months.

Medium Earth Orbit (MEO) satellites MEOs can be positioned somewhere betweenLEOs and GEOs, both in terms of their orbitand due to their advantages anddisadvantages.

Using orbits around 10,000 km, the systemonly requires a dozen satellites which is morethan a GEO system, but much less than a LEOsystem.

MEOs can be positioned somewhere betweenLEOs and GEOs, both in terms of their orbitand due to their advantages anddisadvantages.

Using orbits around 10,000 km, the systemonly requires a dozen satellites which is morethan a GEO system, but much less than a LEOsystem.

Medium Earth Orbit (MEO) satellites These satellites move more slowly relative tothe earths rotation allowing a simpler systemdesign

Satellite periods are about six hours.

Depending on the inclination, a MEO cancover larger populations, so requiring fewerhandovers.

These satellites move more slowly relative tothe earths rotation allowing a simpler systemdesign

Satellite periods are about six hours.

Depending on the inclination, a MEO cancover larger populations, so requiring fewerhandovers.

Disadvantages - MEO Again, due to the larger distance to the earth,delay increases to about 7080 ms.

The satellites need higher transmit power andspecial antennas for smaller footprints.

Again, due to the larger distance to the earth,delay increases to about 7080 ms.

The satellites need higher transmit power andspecial antennas for smaller footprints.

Sun- Synchronous Orbits satellites

These satellites rise and set with the sun.

Their orbit is defined in such a way that theyare always facing the sun and hence theynever go through an eclipse.

These satellites rise and set with the sun.

Their orbit is defined in such a way that theyare always facing the sun and hence theynever go through an eclipse.

Hohmann Transfer Orbit This is an intermediate orbit having a highlyelliptical shape.

It is used by GEO satellites to reach their finaldestination orbits.

This orbit is connected to the LEO orbit at thepoint of perigee forming a tangent and isconnected to the GEO orbit at the point ofapogee again forming a tangent.

This is an intermediate orbit having a highlyelliptical shape.

It is used by GEO satellites to reach their finaldestination orbits.

This orbit is connected to the LEO orbit at thepoint of perigee forming a tangent and isconnected to the GEO orbit at the point ofapogee again forming a tangent.

Prograde orbit This orbit is with an inclination of less than90.

Its direction is the same as the direction asthe rotation of the primary (planet).

This orbit is with an inclination of less than90.

Its direction is the same as the direction asthe rotation of the primary (planet).

Retrograde orbit This orbit is with an inclination of more than90.

Its direction is counter to the direction ofrotation of the planet

This orbit is with an inclination of more than90.

Its direction is counter to the direction ofrotation of the planet

Polar Orbits This orbit passes above or nearly above bothpoles (north and south pole) of the planet oneach of its revolution.

Therefore it has an inclination of (or very closeto) 90 degrees.

This orbit passes above or nearly above bothpoles (north and south pole) of the planet oneach of its revolution.

Therefore it has an inclination of (or very closeto) 90 degrees.

Examples

INTELSAT International Telecommunication Satellite: Created in 1964 Over 140 member countries More than 40 investing entities Early Bird satellite in 1965 Six (6) evolutions of INTELSAT satellites between 1965-87 Geostationary orbit Covers 3 regions:

Atlantic Ocean Region (AOR), Indian Ocean Region (IOR), and Pacific Ocean Region (POR)

International Telecommunication Satellite: Created in 1964 Over 140 member countries More than 40 investing entities Early Bird satellite in 1965 Six (6) evolutions of INTELSAT satellites between 1965-87 Geostationary orbit Covers 3 regions:

Atlantic Ocean Region (AOR), Indian Ocean Region (IOR), and Pacific Ocean Region (POR)

U.S DOMSATS Domestic Satellite: In geostationary orbit Over 140 member countries Direct-to-home TV service Three (3) categories of U. S. DBS system: high power, medium, and low power. Measure in equivalent isotropic radiated power (EIRP). The upper limit of EIRP:

High power (60 dBW), Medium (48 dBW), and Low power (37 dBW).

Domestic Satellite: In geostationary orbit Over 140 member countries Direct-to-home TV service Three (3) categories of U. S. DBS system: high power, medium, and low power. Measure in equivalent isotropic radiated power (EIRP). The upper limit of EIRP:

High power (60 dBW), Medium (48 dBW), and Low power (37 dBW).

Polar Orbiting Satellites These satellites follow the Polar Orbits. An infinite number of polar orbits cover northand south polar regions.

Weather (ultraviolet sensor also measureozone level) satellites between 800 and 900km

National Oceanic and AtmosphericAdministration (NOAA) operate a weathersatellite system

These satellites follow the Polar Orbits. An infinite number of polar orbits cover northand south polar regions.

Weather (ultraviolet sensor also measureozone level) satellites between 800 and 900km

National Oceanic and AtmosphericAdministration (NOAA) operate a weathersatellite system

Polar Orbiting Satellites The system uses both geostationaryoperational environment satellite (GOES) andpolar operational environment satellite (POES)

Search and rescue (SAR) satellite: Cospas-Sarsat.

The system uses both geostationaryoperational environment satellite (GOES) andpolar operational environment satellite (POES)

Search and rescue (SAR) satellite: Cospas-Sarsat.

History & Background of Satellites-I 1957 Sputnik I(USSR),First active satellite, Transmittedtelemetry info for 21 days In same year, Explorer I(US),transmitted telemetry info for 5months 1958,NASAs Score, first artificial satellite used for relayingterrestrial communications. 1960, Echo-1(US), a Passive Satellite 1962, AT&T Telstar 1, LEO satellite, First active satellite tosimultaneously transmit and receive radio signals,damaged by radiation 1963, Telstar 2,electronically similar to Telstar 1 exceptmore radiation resistant, accomplished first successfulvideo transmission

1957 Sputnik I(USSR),First active satellite, Transmittedtelemetry info for 21 days In same year, Explorer I(US),transmitted telemetry info for 5months 1958,NASAs Score, first artificial satellite used for relayingterrestrial communications. 1960, Echo-1(US), a Passive Satellite 1962, AT&T Telstar 1, LEO satellite, First active satellite tosimultaneously transmit and receive radio signals,damaged by radiation 1963, Telstar 2,electronically similar to Telstar 1 exceptmore radiation resistant, accomplished first successfulvideo transmission

History & Background of Satellites-II 1963,Syncom I-First attempt to place a geosynchronous satellite intoorbit, lost during orbit injection 1963,1964-Successful launches of Syncom II, Syncom III (linkedJapan and USA), Syncom III was used to broadcast 1964 OlympicGames from Tokyo Meanwhile in 1961,US President defined U.S policy in regard tosatellite communications and showed interest to develop a singleworldwide system. ITU was asked to examine aspects of space communication forwhich international co-operation is required. As a result commercial investment started in an internationalsatellite organization called Intelsat(International SatelliteOrganization) by 12 interested countries. By 2000, Intelsat had 143member countries

1963,Syncom I-First attempt to place a geosynchronous satellite intoorbit, lost during orbit injection 1963,1964-Successful launches of Syncom II, Syncom III (linkedJapan and USA), Syncom III was used to broadcast 1964 OlympicGames from Tokyo Meanwhile in 1961,US President defined U.S policy in regard tosatellite communications and showed interest to develop a singleworldwide system. ITU was asked to examine aspects of space communication forwhich international co-operation is required. As a result commercial investment started in an internationalsatellite organization called Intelsat(International SatelliteOrganization) by 12 interested countries. By 2000, Intelsat had 143member countries

History & Background of Satellites-II Intelsat I(called Early Bird) was the first commercialtelecommunications satellite in geo-synchronous orbit in 1965. Between 1966 and 1987,Intelsat launched series of satellitesdesignated as Intelsat II, III,IV,V,VI. Within 10 years, Intelsat was self-supporting and since it was notallowed to make profit, it began returning substantial revenues toits members. Four basic service categories of Intelsat are:

International public switched telephonyBroadcastingPrivate line/business networksDomestic/regional communications

Intelsat I(called Early Bird) was the first commercialtelecommunications satellite in geo-synchronous orbit in 1965. Between 1966 and 1987,Intelsat launched series of satellitesdesignated as Intelsat II, III,IV,V,VI. Within 10 years, Intelsat was self-supporting and since it was notallowed to make profit, it began returning substantial revenues toits members. Four basic service categories of Intelsat are:

International public switched telephonyBroadcastingPrivate line/business networksDomestic/regional communications

History & Background of Satellites-III USSR launched first regional satellite system, Molniya,of highlyelliptic orbit(HEO) in 1965 Canada was the first country to build a national telecommunicationsystem using GEO satellites called Anik in 1974. 1970s and 1980s saw rapid deployment of GEO satellites forinternational, regional and domestic telephone traffic and videodistribution. Inmarsat (International Maritime Satellite Organization) hasprovided services to ships and aircrafts for decades. Implementation of LEO and MEO satellite system for mobilecommunication has proven to be costly and has smaller systemcapacity Satellite navigation systems, notably GPS, have revolutionizednavigation and surveying

USSR launched first regional satellite system, Molniya,of highlyelliptic orbit(HEO) in 1965 Canada was the first country to build a national telecommunicationsystem using GEO satellites called Anik in 1974. 1970s and 1980s saw rapid deployment of GEO satellites forinternational, regional and domestic telephone traffic and videodistribution. Inmarsat (International Maritime Satellite Organization) hasprovided services to ships and aircrafts for decades. Implementation of LEO and MEO satellite system for mobilecommunication has proven to be costly and has smaller systemcapacity Satellite navigation systems, notably GPS, have revolutionizednavigation and surveying

History & Background of Satellites-IV Satellite Communication Organizations

International Organizations such as Intelsat,Inmarsat, Intersputnik, Eutelsat, RASCOM

Many regional organizations in Africa, Asia, Europeand North-America

Experimental Organizations such as ApplicationTechnology Satellite (ATS)

Satellite Communication Organizations International Organizations such as Intelsat,Inmarsat, Intersputnik, Eutelsat, RASCOM

Many regional organizations in Africa, Asia, Europeand North-America

Experimental Organizations such as ApplicationTechnology Satellite (ATS)

Application Technology Satellite (ATS) Launched on Nov 05, 1967, for TV and DataTransfer Experiments, NASA Approved Users,Provide emergency communications duringnatural disasters

Launched on Nov 05, 1967, for TV and DataTransfer Experiments, NASA Approved Users,Provide emergency communications duringnatural disasters