The Marsadvancedradarforsubsurfaceandionosphericsounding(MARSIS)onMarsExpressisthefirst high-frequencysoundingradaroperatingfromorbitalaltitudessincetheApollo17LunarSounderflown in 1972.Theradaroperatesfromahighlyellipticalorbitbutacquiresdataonlyfromaltitudeslower than 1200km.Theperiapsisaltitudeis250km.ThisradarhasbeensuccesfullyoperatingsinceAugust 2005.Theradarisadualchannellow-frequencysounder,operatesbetween1.3and5.5MHz (MegaHertz)withwavelengthsbetween230and55minfreespaceforsubsurfacesounding and between0.1and5.5MHz(wavelengthsbetween3000and55m)forionosphericsounding. The subsurfacesoundercanoperateatoneortwo-frequencybandsoutoffouravailablebandsateither like orcrosspolarization.Thesubsurfacesoundingradartransmitsradiofrequency(RF)pulsesof250 ms duration througha40mdipoleantenna.Thereturnechoesarethenconvertedtodigitalformand temporarily storedonboardforsomedigitalprocessing.Asecondantenna,amonopole,provides receptionforthecross-polarizedreturnanditsdataareprocessedbyasecondchannel.Thisprocessing reduces thedatarateproducedbytheinstrumenttoratesallowedbythespacecraftcommunications channel.TheseprocessedreturnsarethensenttoEarthbythetelecommunicationssystemonthe spacecraft. Theadvancesindigitaldataacquisitionandprocessing,since1972,haveenabledthis techniquetobeusedinacompactspacecraftscienceinstrument..Thissounderhasobtainedreturns from severalkilometersbelowthesurfaceoftheMars.Theionosphericsounderoperatesataltitudes greaterthan800kminamodethatsweepstheentire0.1–5.5MHzrange.Duringionosphericsounding, the transmittersendsa91 ms toneat127pulsespersecondrate.Thefrequencysweeptakes7.3sto completethe0.1–5.5MHzrange.Operationalaspectsoftheinstrumentaredescribed,includingthe selectionoffrequencybandsandreceiveantennaselection,whicharebasedontheexpectedsolar zenithangle.Theprocessofdatatakeplanningaswellasdataarchivingaredescribed.Resultsofboth subsurfaceandionosphericsoundingarepresented.
The MarsexpressMARSISsounderinstrument / R., Jordan; Picardi, Giovanni; J., Plaut; K., Wheeler; D., Kirchner; A., Safaeinili; W., Johnson; Seu, Roberto; D., Calabrese; E., Zampolini; A., Cicchetti; R., Huff; D., Gurnett; A., Ivanov; W., Kofman; R., Orosei; T., Thompson; P., Edenhofer; O., Bombaci. - In: PLANETARY AND SPACE SCIENCE. - ISSN 0032-0633. - 57:(2009), pp. 1975-1986. [10.1016/j.pss.2009.09.016]
The MarsexpressMARSISsounderinstrument
PICARDI, Giovanni;SEU, Roberto;
2009
Abstract
The Marsadvancedradarforsubsurfaceandionosphericsounding(MARSIS)onMarsExpressisthefirst high-frequencysoundingradaroperatingfromorbitalaltitudessincetheApollo17LunarSounderflown in 1972.Theradaroperatesfromahighlyellipticalorbitbutacquiresdataonlyfromaltitudeslower than 1200km.Theperiapsisaltitudeis250km.ThisradarhasbeensuccesfullyoperatingsinceAugust 2005.Theradarisadualchannellow-frequencysounder,operatesbetween1.3and5.5MHz (MegaHertz)withwavelengthsbetween230and55minfreespaceforsubsurfacesounding and between0.1and5.5MHz(wavelengthsbetween3000and55m)forionosphericsounding. The subsurfacesoundercanoperateatoneortwo-frequencybandsoutoffouravailablebandsateither like orcrosspolarization.Thesubsurfacesoundingradartransmitsradiofrequency(RF)pulsesof250 ms duration througha40mdipoleantenna.Thereturnechoesarethenconvertedtodigitalformand temporarily storedonboardforsomedigitalprocessing.Asecondantenna,amonopole,provides receptionforthecross-polarizedreturnanditsdataareprocessedbyasecondchannel.Thisprocessing reduces thedatarateproducedbytheinstrumenttoratesallowedbythespacecraftcommunications channel.TheseprocessedreturnsarethensenttoEarthbythetelecommunicationssystemonthe spacecraft. Theadvancesindigitaldataacquisitionandprocessing,since1972,haveenabledthis techniquetobeusedinacompactspacecraftscienceinstrument..Thissounderhasobtainedreturns from severalkilometersbelowthesurfaceoftheMars.Theionosphericsounderoperatesataltitudes greaterthan800kminamodethatsweepstheentire0.1–5.5MHzrange.Duringionosphericsounding, the transmittersendsa91 ms toneat127pulsespersecondrate.Thefrequencysweeptakes7.3sto completethe0.1–5.5MHzrange.Operationalaspectsoftheinstrumentaredescribed,includingthe selectionoffrequencybandsandreceiveantennaselection,whicharebasedontheexpectedsolar zenithangle.Theprocessofdatatakeplanningaswellasdataarchivingaredescribed.Resultsofboth subsurfaceandionosphericsoundingarepresented.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
