ACS WFC CCD Radiation Test The Radiation Environment

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1、ACSInstrumentScienceReport00-09ACSWFCCCDRadiationTest:TheRadiationEnvironmentMichaelR.JonesSpaceTelescopeScienceInstituteMay15,2000ABSTRACTThespaceenvironmentisacomplex,orbitdependentphenomenon.Regardlessoforbit,theexternalsurfacesofaspacecraftwillbeex

2、posedtophotons,chargedparticlesandsolidparticlessuchasmicrometeoroids.Vehiclesinlowearthorbit(LEO)mustbedesignedtowithstandadditionalenvironmentalhazardssuchashyper-velocityimpactsbyman-madeorbitaldebrisanderosionofexternalsurfacesbynaturallyoccurringa

3、tomicoxygen.CCDdetectorsareparticularlyvulnerabletodamagebyionizingradiation.ThisdocumentsummarizesthemodelingandanalysisthatwasperformedtodeterminetheappropriateexposurelevelforgroundtestingoftheAdvancedCameraforSurveys(ACS)WideFieldChannel(WFC)Charge

4、-CoupledDevice(CCD)detector.1.IntroductionRadiationdamageeffectsinCCDimagershavebeenstudiedinthelaboratoryforupwardsof30years.Goodqualitylong-termmeasurementsoftheon-orbitdegradationofCCDdetectorsinthespaceenvironmenthavealsorecentlybecomeavailable.Gro

5、undtestdataandon-orbitmeasurementsareconsistentinshowingthatCCDimagersarehighlysusceptibletoradiationdamage.AcomprehensivediscussionofthetypesofradiationdamageknowntooccurinCCDsisbeyondthescopeofthisdocument.Excellentsurveypapersonthesubjectcanbefoundi

6、ntheliterature[1,2].Papersthatprovideanoverviewofthespaceradiationenvironmentandtheimpactofradiationonspacecraftsystemshavealsobeenpublished[3,4].Readerswhodesiretoexplorethesetopicsinmoredepthareencouragedtoreadthecitedreferences.Spacecraftinloweartho

7、rbitatallinclinationsareexposedtoelectronsandprotonstrappedintheVanAllenradiationbelts.Theaccumulatedexposuretotrappedparticlesis1dominatedbypassagethroughtheSouthAtlanticAnomaly(SAA).Unliketrappedradia-tion,exposuretosolarcoronalmassejection(CME)proto

8、nsisinclinationdependent.AvehicleinahighinclinationorbitwillbeexposedtoCMEprotonsasitfliesthroughthepolarauroralregionsofthegeomagneticfield.Forthelowinclination28.5degreeHSTorbit,attenuationbythegeomagneticfieldeffectivelyshieldsthespacec