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1、NASA'sAliceultraviolet(UV)spectrographaboardtheEuropeanSpaceAgency'sRosettacometorbiterhasdelivereditsfirstscientificdiscoveries.Rosetta,inorbitaroundcomet67P/Churyumov-Gerasimenko,isthefirstspacecrafttostudyacometupclose.AsAlicebeganmappingthecomet'ssurfacelastmonth,
2、itmadethefirstfarultravioletspectra1ofacometarysurface.Fromthesedata,theAliceteamdiscoveredthatthecometisunusuallydarkatultravioletwavelengths2andthatthecomet'ssurface--sofar--showsnolargewater-icepatches.Aliceisalsoalreadydetectingbothhydrogenandoxygeninthecomet'scom
3、a3,oratmosphere."We'reabitsurprisedatbothjusthowveryunreflectivethecomet'ssurfaceis,andwhatlittleevidenceofexposedwater-iceitshows,"saysDr.AlanStern,Aliceprincipalinvestigator4andanassociatevice5presidentoftheSouthwestResearchInstitute(SwRI)SpaceScienceandEngineeringD
4、ivision.DevelopedbySwRI,Aliceisprobingtheorigin,compositionandworkingsofthecomet,gainingsensitive,high-resolutioncompositionalinsightsthatcannotbeobtainedbyeitherground-basedorEarth-orbitalobservations.TheultravioletwavelengthsAliceobservescontainuniqueinformationabou
5、tthecompositionofthecomet'satmosphereandthepropertiesofitssurface."Asthemissionprogresses,wewillcontinuetosearchforsurfaceicepatchesandultravioletcolorandcompositionvariationsacrossthesurfaceofthecomet,"saysDr.LoriFeaga,Aliceco-investigatorattheUniversityofMaryland.Al
6、iceisoneofthreeinstrumentsfundedbyNASAflyingaboardRosetta.Alicehasmorethan1,000timesthedata-gatheringcapability6ofinstrumentsflownagenerationago,yetitweighslessthan4kilogramsanddrawsjust4watts7ofpower.AsisterAliceinstrumentwasdevelopedbySwRIandwaslaunchedaboardtheNewH
7、orizonsspacecrafttoPluto8inJanuary2006tostudythatdistantworld'satmosphere.ItwillreachPlutoinJuly2015.SwRIalsobuiltandoperatesRosetta'sIonandElectronSpectrograph(IES),anotherinstrumentwithminiaturizedelectronicsystems.Withamassof1.04kilograms,IESachievessensitivitycomp
8、arabletoinstrumentsweighingfivetimesmore.Toreachitscomettarget,theRosettaspacecraftexecutedfourgravityassists(threefromEarth
