Satellite Space Satellite Space SegmentSegment

Communication FrequenciesCommunication FrequenciesFrequency Band (GHz)Frequency Band (GHz)

BandBand UplinkUplink CrosslinkCrosslink DownlinkDownlink BandwidthBandwidth========================================================================CC 55..99--66..44 33..77 –– 44..22 00..55XX 77..99--88..44 77..2525--77..7575 00..55KuKu 1414--1414..55 1111..77--1212..22 00..55KaKa 2727--3030 1717--2020 ____

3030--3131 2020--2121 ____

QQ ______ 4040--4141 11..004141--4343 22..00

VV 5050--5151 ________ ________ 11..00(ISL)(ISL) 5454--5858 33..99

5959--6464 55..00

Satellite SegmentsSatellite Segments

A satellite communications system can be A satellite communications system can be broadly classified into broadly classified into 2 2 segments:segments:

Space Segment: includes the sat. and Space Segment: includes the sat. and ground facilities (TT&Cground facilities (TT&C-- tracking, telemetry tracking, telemetry & Command)& Command)

Earth Segment: consists of the transmit and Earth Segment: consists of the transmit and receive earth stations.receive earth stations.

The Payload & BusThe Payload & Bus The equipment carried aboard the sat. can The equipment carried aboard the sat. can

be classified to:be classified to: The Payload: the equipment used to provide The Payload: the equipment used to provide

the service for which the sat. has been the service for which the sat. has been launched.launched.

The Bus: refers to the vehicle as well as the The Bus: refers to the vehicle as well as the subsystems that provide the power, attitude subsystems that provide the power, attitude control, orbital control, thermal control, control, orbital control, thermal control, command and telemetry functions required command and telemetry functions required to service the payloadto service the payload

The Satellite Power SupplyThe Satellite Power Supply

The primary electrical power for electronic The primary electrical power for electronic equipments is obtained from solar cells. equipments is obtained from solar cells.

Individual cells can generate only small Individual cells can generate only small amounts of power amounts of power arrays of cells in arrays of cells in seriesseries--parallel connection are requiredparallel connection are required

Power Supply: HS Power Supply: HS 376 376 Sat.Sat.

216216xx660 660 cm diam.cm diam. The outer cyl. is telescoped The outer cyl. is telescoped

over the inner during launch over the inner during launch sequencesequence

940 940 W dc power that may W dc power that may drop to drop to 760 760 W after W after 10 10 years.years.

During eclipse, During eclipse, 2 2 NickelNickel--cadmium longcadmium long--life batteries life batteries are used with are used with 830 830 W (W (16 16 h h recharge time)recharge time)

Power Supply: Aussat B Power Supply: Aussat B –– Optus B Optus B HigherHigher PowersPowers cancan bebe

achievedachieved withwith solarsolar panelspanelsinin rectangularrectangular solarsolar sailssails..

SolarSolar SailsSails areare foldedfoldedduringduring launchlaunch phasephase

TheThe fullfull complementcomplement ofofsolarsolar cellscells isis exposedexposed totothethe sunlight,sunlight, andand thethe sailssailsareare arrangedarranged toto rotaterotate tototracktrack thethe sunsun higherhigherPowerPower ((22--66 kW)kW)

Sun Eclipses for GEOSun Eclipses for GEO

Spring and Autumnal Equinoxes: eclipses daily Spring and Autumnal Equinoxes: eclipses daily about about 72 72 min min 23 23 days before and after equinoxdays before and after equinox

Attitude ControlAttitude Control

The attitude: refers to the sat. orientationThe attitude: refers to the sat. orientation Attitude control is required for antenna Attitude control is required for antenna

alignmentalignment Disturbance torques can alter the attitudeDisturbance torques can alter the attitude Usually on board even it can be on earthUsually on board even it can be on earth Passive (spin) and Active methods (gas jets Passive (spin) and Active methods (gas jets

and momentum wheels)and momentum wheels)

Attitude RPW Axes:Attitude RPW Axes:Roll, Pitch and Yaw Roll, Pitch and Yaw

Spin StabilizationSpin Stabilization

Spinner Sats: use the angular momentum of its spinning body Spinner Sats: use the angular momentum of its spinning body to provide roll and yaw stabilization: (to provide roll and yaw stabilization: (5050--100 100 rev/min) rev/min)

Momentum Wheel StabilizationMomentum Wheel Stabilization

ThreeThree AxisAxis SatsSats:: thethebodybody remainsremains fixedfixedrelativerelative toto EarthEarthsurfacesurface whilewhile ananinternalinternal subsystemsubsystemprovidesprovides rollroll andand yawyawstabilizationstabilization

Station KeepingStation Keeping

GEO Sats are to be kept in its correct orbital GEO Sats are to be kept in its correct orbital slotslot

Equatorial ellipticity causes Sats to drift Equatorial ellipticity causes Sats to drift slowly along orbit to one of stable points : slowly along orbit to one of stable points : 7575oo E and E and 105105oo W W jets are used to jets are used to compensate and pulsed every compensate and pulsed every 22--3 3 weeks weeks (east(east--west station keeping maneuvers)west station keeping maneuvers)

Station KeepingStation Keeping GEOGEO driftdrift alsoalso InIn

latitudelatitude duedue toto sunsunpullpull ((00..8585oo /year/year inininclination)inclination)

JetsJets areare pulsedpulsed totocorrectcorrect inclinationinclinationtoto zerozero (north(north--southsouth stationstationkeepingkeepingmaneuvers)maneuvers)

TheseThese maneuversmaneuversareare commandedcommandedfromfrom thethe TT&CTT&C

Thermal ControlThermal Control

SatellitesSatellites areare subjectsubject toto largelarge thermalthermalgradientsgradients::11)) OneOne sideside towardtoward sun,sun, thethe otherother intointo spacespace..22)) HeatHeat fromfrom equipmentsequipments

33)) HeatHeat fromfrom groundground

MirrorsMirrors andand isolatorsisolators areare usedused

TT&CTT&C

TT&CTT&C performsperforms severalseveral routineroutine functionsfunctions::11)) telemetrytelemetry:: attitudeattitude infoinfo..22)) environmentalenvironmental:: magmag.. FiledFiled intensityintensity33)) spacecraftspacecraft infoinfo:: temperature,temperature, powerpower supply,supply,etcetc

SpecificSpecific FrequenciesFrequencies werewere assignedassigned forfor TT&CTT&C

EncryptionEncryption isis implementedimplemented toto protectprotect fromfromunauthorizedunauthorized commandscommands

TranspondersTransponders TransponderTransponder:: thethe seriesseries ofof interconnectedinterconnected unitsunits

whichwhich formsforms aa singlesingle communicationscommunications channelchannelbetweenbetween thethe receivereceive andand transmittransmit antennaantenna..

SomeSome unitsunits maymay bebe commoncommon toto aa numbernumber ofoftransponderstransponders

Antenna LNA DownConverterMixer+LO

+BPFHPAAntenna

LNALNA-- Low Noise Amplifier HPALow Noise Amplifier HPA-- High Power AmplifierHigh Power Amplifier

The Wideband ReceiverThe Wideband Receiver

Polarization and Frequency ReusePolarization and Frequency Reuse

AdditionalAdditional commcomm.. ChannelsChannels cancan bebe achievedachievedusingusing polarizationpolarization discriminationdiscrimination andand FrequencyFrequencyReuseReuse

TheThe transpondertransponder isis consideredconsidered asas anan RFRF--toto--RFRFrepeaterrepeater

PolarizationPolarization DiscriminationDiscrimination cancan bebe obtainedobtained bybymakingmaking thethe carrierscarriers havinghaving thethe samesame frequencyfrequencybutbut withwith differentdifferent inin polarizationpolarization

FrequencyFrequency ReuseReuse cancan bebe alsoalso obtainedobtained usingusing spotspotbeambeam antennasantennas

Polarization DiscriminationPolarization Discrimination ForFor circularcircular:: leftleft--hand/righthand/right--handhand circularcircular (LHC/RHC)(LHC/RHC) ForFor LinearLinear:: Horizontal/VerticalHorizontal/Vertical WithWith spotspot beambeam antennasantennas andand XPDXPD ,, thethe bandwidthbandwidth

canecane bebe doubleddoubled twicetwice:: 00..55 22 GHzGHz

The Antenna SubThe Antenna Sub--systemsystem

TheThe antennasantennas carriedcarried aboardaboard provideprovide thethe dualdual functionsfunctionsofof Uplink/DownlinkUplink/Downlink RX/TXRX/TX operationsoperations

AntennasAntennas rangerange fromfrom omindirectionalomindirectional (dipole(dipole type)type) totohighlyhighly directionaldirectional antennasantennas requiredrequired forfor telecomtelecom.. andandTVTV purposespurposes..

DirectionalDirectional beamsbeams areare usuallyusually producedproduced byby meansmeans ofofreflectorreflector--typetype antennas,antennas, thethe paraboidalparaboidal reflectorreflector beingbeingthethe mostmost commoncommon..

The Antenna SubThe Antenna Sub--systemsystem

WideWide beamsbeams forfor globalglobal coveragecoverage areare producedproduced bybysimplesimple hornhorn antennaantenna atat 66//44 GHzGHz..

TheThe samesame feedfeed hornhorn cancan bebe usedused toto TXTX andand RXRX carrierscarrierswithwith thethe samesame frequencyfrequency (Diplexer),(Diplexer), alsoalso XPDXPD cancan bebeusedused..

SimpleSimple biconicalbiconical dipoledipole antennaantenna isis usedused forfor trackingtrackingandand controlcontrol signalssignals..

Antenna Examples: Horn FeedersAntenna Examples: Horn Feeders

AntAnt.. ExamplesExamples:: ParabolicParabolic ReflectorsReflectors

AntAnt.. ExamplesExamples:: DoubleDouble ReflectorsReflectors

3232 mm diameterdiameter ((256256 ton)ton) VeryVery narrownarrow beambeam withwith

calibrationcalibration HeatHeat isis requiredrequired toto

avoidavoid snowsnow attenuationattenuation

AntAnt.. ExEx.. :: CC bandband GEOGEO AntennaAntenna

AntAnt.. ExamplesExamples:: MultifeedMultifeed reflectorreflector

Parabolic Gain & BeamwidthParabolic Gain & Beamwidth

2

DG I

TheThe gaingain ofof thethe paraboloidparaboloid reflectorreflector relativerelative totoisotropicisotropic radiatorradiator::

II-- apertureaperture efficiencyefficiency (typically(typically 00..5555)) -- wavelengthwavelength andand DD-- reflectorreflector diameterdiameter

TheThe 33--dBdB beamwidthbeamwidth inin degreesdegrees::

DdB 703

IntelSat IV Ant. SubIntelSat IV Ant. Sub--SystemsSystems

The Satellite FootprintsThe Satellite Footprints

FootprintFootprint::TheThe geographicalgeographicalrepresentationrepresentation ofof aaSatSat.. antennaantennaradiationradiation

11-- Global (Earth)Global (Earth)22-- HemisphericalHemispherical((2020%% ofof earthearth surface)surface)33--ZoneZone44-- SpotSpot

Mexican Moreles CoverageMexican Moreles Coverage

(C(C-- band)band) (K(K--band)band)

IntelSat V FootprintIntelSat V Footprint

The Wideband ReceiverThe Wideband Receiver

The Wideband ReceiverThe Wideband Receiver RedundantRedundant RXRX:: StandbyStandby

configurationconfiguration

FirstFirst StageStage isis thethe LowLow--NoiseNoise AmplifierAmplifier (LNA)(LNA)::

SomeSome TranspondersTransponders maymayincludeinclude IFIF stagestage similarsimilartoto AMRAMR // DMRDMRconfigurationsconfigurations

LNALNA (tunnel(tunnel diode,diode, FET)FET) AmplifierAmplifier:: BJTBJT @@ 44 GHzGHz andand FETFET @@ 1414 GHzGHz

The Input DeMultiplexerThe Input DeMultiplexer

The Input DeMultiplexerThe Input DeMultiplexer The input DeMUX separates the The input DeMUX separates the

broadband into transponder frequency broadband into transponder frequency channels.channels.

Odd/Even numbered groups provide Odd/Even numbered groups provide more frequ. Separation which reduces more frequ. Separation which reduces adjacent channel interference.adjacent channel interference.

The output from DeMUX is fed to a The output from DeMUX is fed to a power splitter which feeds the two power splitter which feeds the two separate chains of circulators.separate chains of circulators.

Channelizing is achieved using BPFs.Channelizing is achieved using BPFs.

BPF BPF 36 36 MHz BWMHz BW

The High Power Amplifier: HPAThe High Power Amplifier: HPA

The High Power Amplifier: HPAThe High Power Amplifier: HPA

HPA Provides the HPA Provides the output power for output power for each transponder each transponder channel.channel.

Each HPA is preceded by an input attenuator to permit Each HPA is preceded by an input attenuator to permit each amplifier to be adjusted to the desired level.each amplifier to be adjusted to the desired level.

The TravelingThe Traveling--Wave Tubes (TWT) are very common Wave Tubes (TWT) are very common devices for HPAs since it provides amplification over a devices for HPAs since it provides amplification over a wide range of bandwidth.wide range of bandwidth.

General Transponder Block DiagramGeneral Transponder Block Diagram

Canadian ANIKCanadian ANIK--D,ED,E

SSPA- Solid State Power Amplifier.

TWTA- TWT Amplifier

ANIKANIK

Canadian ANIKCanadian ANIK--EE

Canadian ANIKCanadian ANIK--EE11