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1、AnatomyofaCharge-CoupledDeviceChargecoupleddevicetechnologywasfirstdemonstratedin1969attheBellLaboratories.In1974,underthesponsorshipoftheNASAInstrumentandSensingTechnologyprogram,theJetPropulsionLaboratorybeganaprogramtoincreasethesizeofCCDarrays(thenlesstha
2、n100-by-100pictureelements,orpixels)andtolowertheirreadoutnoiselevels.Shor什ythereafter,theOfficeofSpaceScience(OSS)addedfunding,andby1978CCDarraysof5()()-by-500pixelshadbeenproduced,achievingnoiselevelsof10electronsrms(rootmeansquare).Afterthis,OSScontinuedth
3、edevelopmentofthe800-by-800arraysthatarecurrentlybeingusedbyGalileo(1989launch)andtheHubbleSpaceTelescope(1990launch).In1982,theNASAInstrumentandSensingTechnologyprogramsubstantiallyincreaseditsfundingand,combinedwithOSSAdvancedDevelopmentprogram,fundedthedev
4、elopmentofthesecondgenerationofCCDdetectors.Thesehaveyetlargerformats,lowernoise,improvedmanufacturingyield,andforthefirsttimeexcellentx-rayresponse.ThisworkcontinuedsuccessfullyandleddirectlytotheYohkohSoftX-rayTelescopethatissuccessfullyoperatinginorbit.Man
5、yfuturemissionsplantousethistechnology,includingtheCassiniImagingScienceSubsystem.ThesesecondgenerationCCD'ssurpasstheirpredecessorsinalmosteverycharacteristic.Theyhavelargerformats(1024-by-1024verses800-by-800),smallerpixels(12micronsverses15microns),lowerno
6、ise(2electronsverses10electronsrms),lowercost,andhigherreliability,thatthefirstgenerationCCD's.SuchanimprovedCCDflewontheSpaceShuttleaspartoftheJohnsonSpaceCentersElectronicStillCamera.OurmostrecentCCDtechnologyeffortshavebeenfocusedonunderstandingradiometric
7、accuracyforverysensitivemeasurements(suchassearchingforplanetsaroundotherstars)andonimprovingCCDresponseintheultravioletregionoftheelectromagneticspectrum.Charge-coupleddevices(CCDs)aresilicon-basedintegratedcircuitsconsistingofadensematrixofphotodiodesthatop
8、eratebyconvertinglightenergyintheformofphotonsintoanelectroniccharge.Electronsgeneratedbytheinteractionofphotonswithsiliconatomsarestoredinapotentialwellandcansubsequentlybetransferredacr
