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1、SpacecrafttrackingLucianoIessDipartimentodiingegneriameccanicaeaerospazialeUniversitàLaSapienza,Rome,ItalyTopics•RadioscienceexperimentswithplanetaryprobesoAtmospheres,ringsoSolarcorona,ionospheresoCelestialmechanicsandplanetarygeodesyoRelativisticgravity•Spacecraftcommunication
2、andtrackingsystems–Anoverview•Doppler(rangerate)[hands-onactivity]•Range•Angular(VLBI/deltaDOR)Uplink-Telecommand•Enableshighprecisionradio-metricmeasurementsfornavigationandradioscience(2-and3-way)•Sendcommandstoasatellite–Housekeepingandinstrumentscommands(maneuvers,batterycon
3、trols,instrumentturn-on/off,etc.)–RFrelatedcommands(transmitteron/off,frequencybandsandmodulationselections,etc.)•Frequencybandsused–2025-2120MHz(S-band,lessandlessused)–7145-7235MHz(X-band,standard)–34.2-34.7GHz(Ka-band,futurefordeepspace)Downlink-Telemetry•Navigationandradiosc
4、ienceobservables•Telemetrydata–Satelliteparameters(housekeeping),payloaddata,scientificdata•Frequencybandsused–2200-2300MHz(S-band,oldstandard–emergencyuse)–8025-8400MHz(X-band,Earthexplorationsatellites)–8400-8500MHz(X-band,todaystandard)–25.5-27.0GHz(K/Ka-band,futurehighdatara
5、teEarthsatellites)–31.8-32.3GHz(Ka-band,frequentlyusedindeepspacemissions)Spacecraftcommunicationsystems•Antennas•Amplifiers•Transmitters•ReceiversTransponders•ChannelmodelEIRP•TheEquivalentIsotropicallyRadiatedPower(EIRP)istheapparentpowertransmittedtowardsthereceiver,productof
6、thepowersuppliedtotheantennaandtheantennagaininthereceiver’sdirectionrelativetoanisotropicantenna:EIRP=GP[W]TTwhereG=gainoftransmitterantennainthedirectionofreceiverTP=powersuppliedtoantennaTRosettaSpacecraftRosettaX-bandMGATransponders•Thetransponderislocatedinsidethespacecraft
7、.•Itisthecrucialcomponentofaradiolink•Itsfunctionistoreceivethetelecommandsataspecifiedfrequency(lockedbymeansofaPLL)andtoretransmitthetelemetrysignalatadifferentfrequencyviaacoherentturn-aroundratio(e.g.S-band240/221,X-band880/749,14/15Ka-band).•Aphase-lockedloopenablestheonboa
8、rdtrackingoftheuplinksignalanditscoherentretran
