卫星通信第7章改ppt课件.ppt

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1、2021/8/41Chapter7TheSpaceSegment7.1IntroductionSpacesegment:satellite,TT&Cequipmentcarriedaboardthesatellite(payload,bus)Bus:vehiclecarryingthepayload,power,attitudecontrol,orbitalcontrol,thermalcontrol,commandandtelemetry.Payload:transponder(connectingthetransmitandreceiveantenna),antenn

2、asubsystem.Satellitecommunicationsystem:groundsegmentspacesegment2021/8/42Chapter7TheSpaceSegment7.1Introduction2021/8/43Chapter7TheSpaceSegment7.2PowerSupplyTheprimaryelectricalpowerforoperatingtheelectronicequipmentisobtainedfromsolarcells.Solarcellpanel(Spin-Stabilized760W-940W;Three-A

3、xisStabilized2kW-6kW)Duringthelaunchsequence,outercylinderistelescopedovertheinnerone.Rectangularsolarsailsarefolded.2021/8/44Chapter7TheSpaceSegment7.3AttitudeControlTheattitudeofasatellitereferstoitsorientationinthespace.Attitudecontrol:ensurethatdirectionalantennaspointintheproperdirec

4、tions,isdifferentfromstationkeeping(orbitposition)Attitudecontrolinstruments:infraredsensors(horizondetector)Attitudemaneuver(机动):SatelliteAttitudeAdjustmentControllingtorques:passiveattitudecontrol,Activecontrolpassiveattitudecontrol:spinstabilizationandgravitygradientstabilization(inter

5、actionofsatellitewiththegravitationalfieldofcentralbody).Activecontrol:momentumwheels(飞轮),electromagneticcoilsandmassexpulsion(gasjetsandionthrusters(离子推进器))2021/8/45Chapter7TheSpaceSegment7.3AttitudeControl2021/8/46Chapter7TheSpaceSegment7.3AttitudeControlThethreeaxes:roll(滚动),pitch(俯仰)a

6、ndyaw(偏航)(RPY)axes.Allthreeaxespassthroughthecenterofgravityofthesatellite.Foranequatorialorbitmovementabouttherollaxismovestheantennafootprintnorthandsouth;movementaboutthepitchaxismovestheantennafootprinteastandwest;movementabouttheyawaxisrotatestheantennafootprint.2021/8/47Chapter7TheS

7、paceSegment7.3AttitudeControl7.3.1SpinningsatellitestabilizationBeachievedwithcylindersatellites.ForGEOsatellites,thespinaxisisparalleltotheN-Saxisofearth.ImpulsetypethrustersorjetscanbeusedtoincreasethespinrateagainandtoshifttheaxisbacktoitscorrectN-Sorientation.Fo