modis和seaWifs数据使用.docx
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modis和seaWifs数据使用.docx
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modis和seaWifs数据使用
●Modis
MODIS(orModerateResolutionImagingSpectroradiometer)isakeyinstrumentaboardtheTerra(EOSAM)andAqua(EOSPM)satellites.Terra'sorbitaroundtheEarthistimedsothatitpassesfromnorthtosouthacrosstheequatorinthemorning,whileAquapassessouthtonorthovertheequatorintheafternoon.TerraMODISandAquaMODISareviewingtheentireEarth'ssurfaceevery1to2days,acquiringdatain36spectralbands,orgroupsofwavelengths(seeMODISTechnicalSpecifications).Thesedatawillimproveourunderstandingofglobaldynamicsandprocessesoccurringontheland,intheoceans,andintheloweratmosphere.MODISisplayingavitalroleinthedevelopmentofvalidated,global,interactiveEarthsystemmodelsabletopredictglobalchangeaccuratelyenoughtoassistpolicymakersinmakingsounddecisionsconcerningtheprotectionofourenvironment.
DesignConcept
TheMODISinstrumentprovideshighradiometricsensitivity(12bit)in36spectralbandsranginginwavelengthfrom0.4µmto14.4µm.Theresponsesarecustomtailoredtotheindividualneedsoftheusercommunityandprovideexceptionallylowout-of-bandresponse.Twobandsareimagedatanominalresolutionof250matnadir,withfivebandsat500m,andtheremaining29bandsat1km.A±55-degreescanningpatternattheEOSorbitof705kmachievesa2,330-kmswathandprovidesglobalcoverageeveryonetotwodays.
TheScanMirrorAssemblyusesacontinuouslyrotatingdouble-sidedscanmirrortoscan±55-degreesandisdrivenbyamotorencoderbuilttooperateat100percentdutycyclethroughoutthe6-yearinstrumentdesignlife.Theopticalsystemconsistsofatwo-mirroroff-axisafocaltelescope,whichdirectsenergytofourrefractiveobjectiveassemblies;oneforeachoftheVIS,NIR,SWIR/MWIRandLWIRspectralregionstocoveratotalspectralrangeof0.4to14.4µm.
Ahigh-performancepassiveradiativecoolerprovidescoolingto83Kforthe20infraredspectralbandsontwoHgCdTeFocalPlaneAssemblies(FPAs).Novelphotodiode-siliconreadouttechnologyforthevisibleandnearinfraredprovideunsurpassedquantumefficiencyandlow-noisereadoutwithexceptionaldynamicrange.AnalogprogrammablegainandoffsetandFPAclockandbiaselectronicsarelocatedneartheFPAsintwodedicatedelectronicsmodules,theSpace-viewingAnalogModule(SAM)andtheForward-viewingAnalogModule(FAM).Athirdmodule,theMainElectronicsModule(MEM)providespower,controlsystems,commandandtelemetry,andcalibrationelectronics.
Thesystemalsoincludesfouron-boardcalibratorsaswellasaviewtospace:
aSolarDiffuser(SD),av-grooveBlackbody(BB),aSpectroradiometriccalibrationassembly(SRCA),andaSolarDiffuserStabilityMonitor(SDSM).
ThefirstMODISFlightInstrument,ProtoFlightModelorPFM,isintegratedontheTerra(EOSAM-1)spacecraft.TerrasuccessfullylaunchedonDecember18,1999.ThesecondMODISflightinstrument,FlightModel1orFM1,isinegratedontheAqua(EOSPM-1)spacecraft;itwassuccessfullylaunchedonMay4,2002.TheseMODISinstrumentswillofferanunprecedentedlookatterrestrial,atmospheric,andoceanphenomenologyforawideanddiversecommunityofusersthroughouttheworld.
Component
TheMODISinstrumenthasbeendesignedanddevelopedsincetheEngineeringModel(EM)wascompletedinmid-1995.Sincethen,twospaceflightunits,theProtoflightModel(PFM)(aboardtheTerraSatellite),andtheFlightModel1(FM1)(aboardtheAquaSatellite)havebeencompletedandlaunched.TerrawaslaunchedonDecember18,1999,andAquawaslaunchedonMay4,2002.TheMODISinstruments—builttoNASAspecificationsbySantaBarbaraRemoteSensing—representthefinestinengineeringofspaceflighthardwareforremotesensing.
TheMODISinstrumentsweredesignedwiththefollowingsubsystemsandabilities.Followthehighlightedlinksformoretechnicaldescriptionsofeachsubsystem.
∙Atmospheric,land,andoceanimaginginasingleinstrument
∙1,000-m,500-m,and250-mresolutionspectralbands
∙Custom-tailoredspectralbandsfrom0.4to14.4µm;lowout-of-bandresponse
∙Opto-MechanicalSystem
∙Mainframe
∙Continuouslyrotatingdouble-sided ScanMirrorAssembly forlonglife
∙PassiveRadiativeCooler
∙Advanced FocalPlaneAssembly(FPA) technologyforunsurpassedsensitivity
∙OpticalBenchAssembly
∙OpticalSystemDescription
∙DoorAssemblies
oEarth-ViewingDoor
oSolar-ViewingDoor
oSpace-ViewingDoor
∙ElectronicsSystem
∙Space-ViewingAnalogModule
∙Forward-ViewingAnalogModule
∙MainElectronicsModule(MEM)
∙On-BoardCalibrationSystem
∙IRcalibrationeveryscanforlow1/fnoiseandhighaccuracy
∙Lowghosting,lowscatteroptics
∙On-board SolarDiffuser and SolarDiffuserStabilityMonitor(SDSM)
∙On-boardfull-aperture Blackbody(BB)
∙On-board SpectroradiometricCalibrationAssembly(SRCA)
Specifications
Orbit:
705km,10:
30a.m.descendingnode(Terra)or1:
30p.m.ascendingnode(Aqua),sun-synchronous,near-polar,circular
ScanRate:
20.3rpm,crosstrack
SwathDimensions:
2330km(crosstrack)by10km(alongtrackatnadir)
Telescope:
17.78cmdiam.off-axis,afocal(collimated),withintermediatefieldstop
Size:
1.0x1.6x1.0m
Weight:
228.7kg
Power:
162.5W(singleorbitaverage)
DataRate:
10.6Mbps(peakdaytime);6.1Mbps(orbitalaverage)
Quantization:
12bits
SpatialResolution:
250m(bands1-2)
500m(bands3-7)
1000m(bands8-36)
DesignLife:
6years
PrimaryUse
Band
Bandwidth1
Spectral
Radiance2
Required
SNR3
Land/Cloud/Aerosols
Boundaries
1
620-670
21.8
128
2
841-876
24.7
201
Land/Cloud/Aerosols
Properties
3
459-479
35.3
243
4
545-565
29.0
228
5
1230-1250
5.4
74
6
1628-1652
7.3
275
7
2105-2155
1.0
110
OceanColor/
Phytoplankton/
Biogeochemistry
8
405-420
44.9
880
9
438-448
41.9
838
10
483-493
32.1
802
11
526-536
27.9
754
12
546-556
21.0
750
13
662-672
9.5
910
14
673-683
8.7
1087
15
743-753
10.2
586
16
862-877
6.2
516
Atmospheric
WaterVapor
17
890-920
10.0
167
18
931-941
3.6
57
19
915-965
15.0
250
PrimaryUse
Band
Bandwidth1
Spectral
Radiance2
Required
NE[delta]T(K)4
Surface/Cloud
Temperature
20
3.660-3.840
0.45(300K)
0.05
21
3.929-3.989
2.38(335K)
2.00
22
3.929-3.989
0.67(300K)
0.07
23
4.020-4.080
0.79(300K)
0.07
Atmospheric
Temperature
24
4.433-4.498
0.17(250K)
0.25
25
4.482-4.549
0.59(275K)
0.25
CirrusClouds
WaterVapor
26
1.360-1.390
6.00
150(SNR)
27
6.535-6.895
1.16(240K)
0.25
28
7.175-7.475
2.18(250K)
0.25
CloudProperties
29
8.400-8.700
9.58(300K)
0.05
Ozone
30
9.580-9.880
3.69(250K)
0.25
Surface/Cloud
Temperature
31
10.780-11.280
9.55(300K)
0.05
32
11.770-12.270
8.94(300K)
0.05
CloudTop
Altitude
33
13.185-13.485
4.52(260K)
0.25
34
13.485-13.785
3.76(250K)
0.25
35
13.785-14.085
3.11(240K)
0.25
36
14.085-14.385
2.08(220K)
0.35
1 Bands1to19areinnm;Bands20to36areinµm
2 SpectralRadiancevaluesare(W/m2 -µm-sr)
3 SNR=Signal-to-noiseratio
4 NE(delta)T=Noise-equivalenttemperaturedifference
Note:
Performancegoalis30-40%betterthanrequired
●SeaWiFS
SeaWIFS(Sea-ViewingWideField-of-ViewSensor)wasasatellite-bornesensorthatwasdesignedtocollectglobaloceanbiologicaldata.Itsprimarymissionwastoquantifychlorophyllproducedbymarinephytoplankton(microscopicplants).
Instrument
SeaWiFSwastheonlyscientificinstrumentonGeoEye'sOrbView-2(AKASeaStar)satellite,andwasafollow-onexperimenttotheCoastalZoneColorScanneronNimbus7.LaunchedAugust1,1997onanOrbitalSciencesPegasussmallair-launchedrocket,SeaWiFSbeganscientificoperationsonSeptember18,1997andstoppedcollectingdataonDecember11,2010.,farexceedingitsdesignedoperatingperiodof5years.Thesensorresolutionis1.1 km(LAC),4.5 km(GAC).Thesensorrecordedinformationinthefollowingopticalbands:
Band
Wavelength
1
402-422nm
2
433-453nm
3
480-500nm
4
500-520nm
5
545-565nm
6
660-680nm
7
745-785nm
8
845-885nm
Theinstrumentwasspecificallydesignedtomonitoroceancharacteristicssuchaschlorophyll-aconcentrationandwaterclarity.Itwasabletotiltupto20degreestoavoidsunlightfromtheseasurface.Thisfeatureisimportantatequatoriallatitudeswhereglintfromsunlightoftenobscureswatercolour.SeaWiFShadusedtheMarineOpticalBuoyforvicariouscalibration.
TheSeaWiFSMissionisanindustry/governmentpartnership,withNASA'sOceanBiologyProcessingGroupatGoddardSpaceFlightCenterhavingresponsibilityforthedatacollection,processing,calibration,validation,archiveanddistribution.ThecurrentSeaWiFSProjectmanagerisGeneCarlFeldman.
ChlorophyllEstimation
Chlorophyllconcentrationsarederivedfromimagesoftheocean’scolor.Generallyspeaking,thegreenerthewater,themorephytoplanktonarepresentinthewater,andthehigherthechlorophyllconcentrations.Chlorophyllaabsorbsmoreblueandredlightthangreen,withtheresultingreflectedlightchangingfrombluetogreenastheamountofchlorophyllinthewaterincreases.Usingthisknowledge,scientistswereabletouseratiosofdifferentreflectedcolorstoestimatechlorophyllconcentrations.
Thevisiblecolorspectrumwithcorrespondingwavelengthsinnanometers
Manyformulasestimatechlorophyllbycomparingtheratioofbluetogreenlightandrelatingthoseratiostoknownchlorophyllconcentrationsfromthesametimesandlocationsasthesatelliteobservations.Thecoloroflightisdefinedbyitswavelength,andvisiblelighthaswav
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