elevatedto

Seediscussions,stats,andauthorprofilesforthispublicationat:https://www.
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net/publication/222427671AnoverviewoftheSeaWiFSprojectandstrategiesforproducingaclimateresearchqualityglobaloceanbio-opticaltimeseriesArticleinDeepSeaResearchPartIITopicalStudiesinOceanography·February2004DOI:10.
1016/j.
dsr2.
2003.
11.
001CITATIONS366READS3743authors,including:Someoftheauthorsofthispublicationarealsoworkingontheserelatedprojects:NASAOceanColorProjectViewprojectCharlesR.
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Deep-SeaResearchII51(2004)5–42AnoverviewoftheSeaWiFSprojectandstrategiesforproducingaclimateresearchqualityglobaloceanbio-opticaltimeseriesCharlesR.
McClain*,GeneC.
Feldman,StanfordB.
HookerCode970.
2,OfceforGlobalCarbonStudies,NASAGoddardSpaceFlightCenter,Greenbelt,MD20771,USAReceived1April2003;accepted19November2003AbstractTheSea-viewingWideField-of-viewSensor(SeaWiFS)ProjectOfcewasformallyinitiatedattheNASAGoddardSpaceFlightCenterin1990.
Sevenyearslater,thesensorwaslaunchedbyOrbitalSciencesCorporationunderadata-buycontracttoprovide5yearsofsciencequalitydataforglobaloceanbiogeochemistryresearch.
Todate,theSeaWiFSprogramhasgreatlyexceededthemissiongoalsestablishedoveradecadeagointermsofdataquality,dataaccessibilityandusability,oceancommunityinfrastructuredevelopment,costefciency,andcommunityservice.
TheSeaWiFSProjectOfceanditscollaboratorsinthescienticcommunityhavemadesubstantialcontributionsintheareasofsatellitecalibration,productvalidation,near-realtimedataaccess,elddatacollection,protocoldevelopment,insituinstrumentationtechnology,operationaldatasystemdevelopment,anddesktoplevel-0tolevel-3processingsoftware.
OneimportantaspectoftheSeaWiFSprogramisthehighlevelofsciencecommunitycooperationandparticipation.
ThisarticlesummarizesthekeyactivitiesandapproachestheSeaWiFSProjectOfcepursuedtodene,achieve,andmaintainthemissionobjectives.
TheseachievementshaveenabledtheusercommunitytopublishalargeandgrowingvolumeofresearchsuchasthosecontributedtothisspecialvolumeofDeep-SeaResearch.
Finally,someexamplesofmajorgeophysicalevents(oceanic,atmospheric,andterrestrial)capturedbySeaWiFSarepresentedtodemonstratetheversatilityofthesensor.
PublishedbyElsevierLtd.
1.
IntroductionTheSea-viewingWideField-of-viewSensor(SeaWiFS)wastheresultofapersistenteffortbytheoceanbiogeochemicalremotesensingcommu-nitytohaveanoperationalocean-colorsatellitefollowingthegreatsuccessoftheexperimentalNimbus-7CoastalZoneColorScanner(CZCS).
Planningactivities(Ocean-colorScienceWorkingGroup,1982;JointEOSAT/NASASeaWiFSWorkingGroup,1987)paralleledandsupportedtheargumenttoincludeglobalocean-colorob-servationsintheEarthObservingSystem(EOS;AsrarandDozier,1994;Kingetal.
,1999)thatultimatelyresultedintheModerateResolutionImagingSpectroradiometer(MODIS)ontheTerraandAquaplatforms.
ThestrategywastohaveSeaWiFSlaunchprecedetheMODISlaunchbyseveralyearstoinitiateaglobalocean-colortimeseriesinsupportoftheJointGlobalOceanARTICLEINPRESS*Correspondingauthor.
Fax:+1-301-286-0268.
E-mailaddress:charles.
r.
mcclain@nasa.
gov(C.
R.
McClain).
0967-0645/$-seefrontmatterPublishedbyElsevierLtd.
doi:10.
1016/j.
dsr2.
2003.
11.
001FluxStudy(JGOFS)processstudiesintheArabianSea,equatorialPacic,andSouthernOceanandtoprovideampletimetodesignandvalidatesensorcalibrationstrategiesandalgo-rithmsinpreparationfortheMODIStimeseries.
Inaddition,SeaWiFSwastobetherstinaseriesofUSandinternationalocean-colormissionsthatwouldeventuallyprovidealong-termrecordofoceanbiologicalandopticalpropertiesforclimateresearch.
In1990,theNASAGoddardSpaceFlightCenter(GSFC)initiatedacompetitiveocean-colordata-buyprocurementandestablishedaSeaWiFSProjectOfce(SPO).
Adata-buycontractwithOrbitalSciencesCorporation(OSC)wasnalizedin1991withanexpectedlaunchinmid-1993.
NASAwastohaveinsight,butnotoversight,intothespacecraftandsensordesign,construction,andtesting.
Underthecontract,OSCwasresponsibleforbuilding,launching,andoperatingthespacecraft.
Origin-ally,thespacecraftwascalledSeaSTAR,butitwasrenamedafterlaunchtoOrbView-2whenOrbitalImagingCorporation(ORBIMAGE)purchasedthespacecraftfromOSC.
Thepaymentschedulewasfront-endloadedsothatmostofthexedcostswerepaidatthecompletionofspecicmilestonesduringtheprelaunchsystemdevelop-mentandpostlaunchdataacceptancephases.
Afteracceptance,xedmonthlypaymentshavebeenmade,subjecttopenaltiesifthedataqualityislessthannominal(todate,nopenaltieshavebeenapplied).
NASA'sresponsibilitiesincludedsensorandonboardrecorderscheduling(sensortilting,solarcalibrations,lunarcalibrations,inter-nalsensortestsequences,andhigh-resolutiondatarecording),postlaunchsensorcalibration,derivedproductalgorithmdevelopment,dataacquisition[coarseresolutionglobalareacoverage(GAC)andne-resolutionlocalareacoverage(LAC)],dataprocessing,researchdataarchivalanddistribu-tion,andselectionofhigh-resolutionpicturetransmission(HRPT)stations.
Withtheseactiv-itiesinmind,theSPOwasorganizedatGSFCwithaprojectmanager,aprojectscientist,andprojectelementleaders,theelementsbeingDataCapture,MissionOperations(MO),InstrumentScience,Calibration,Validation,andDataProces-sing(DP).
Overtime,theInstrumentScience,Calibration,andValidationelementsweremergedtoformtheCalibrationandValidation(CV)element.
TheprelaunchphasewascharacterizedbyanunprecedentedlevelofcooperationbetweenNASA,OSC,andtheinstrumentsubcontractor,HughesSantaBarbaraResearchCenter,giventhatthecontractdidnotrequireahighdegreeofinteraction.
Infact,GSFCengineeringgroupsmademanyvoluntarycontributionstowardsresolvinganumberoftechnicalproblemswithspacecraftcomponentsandsubsystems,e.
g.
,ra-diationhardness,power,navigationandattitudecontrol,andtelemetry.
Throughouttheprelaunchphase,OSCdemonstratedarmresolvetoachievesuccess,evenatconsiderableexpensetothecompany.
Inaddition,NASAHeadquarterspro-videdsteadfastsupporttotheSPO.
Despitethebesteffortsofallparties,thelaunchscheduleslipped4years.
InAugust1997,theprelaunchphaseculminatedinaawlessPegasus-XLlaunch,andSeaWiFShasdeliveredacontinuousstreamofGACandLACdataofunprecedentedqualitysinceSeptember1997.
Theoriginalsciencegoalsandprojectobjectives,listedinTable1(Hookeretal.
,1992),weredenedtosupportquantitativeresearch.
TheinitialproductsuitewasverysimilartothatoftheCZCSandincludedtotalradiances(level1data),normalizedwater-leavingradiances,chlorophyll-a,diffuseattenuation(490nm),andcertainatmo-sphericcorrection-relatedparameters(level-2products),andbinnedandstandardmappedproductsatvarioustemporalresolutions(level-3products),e.
g.
,daily,8-day,andmonthly(Darzi,1998).
Theradiometricandchlorophyll-aaccuracygoalsarequiterigorousandhaveprovedchallen-gingtomeet.
Giventheaggressivelaunchsche-dule,calibrationandvalidationactivitiesweretobecoordinatedwiththoseoftheMODISOceansTeamthatwerealreadyunderway.
TheSPOalsosoughtthesciencecommunity'sinvolvementineachaspectoftheprogramtocapitalizeontheirexpertise,toexplorenewapplicationsofthedata,andtoensurethegreatestpossibleutilizationofthedataforEarthsystemscience.
TheSPObenetedgreatlyfromitscollaborationswiththeMODISOceansTeam,thesciencecommunityatARTICLEINPRESSC.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–426large,andtheSensorIntercomparisonandMergerforBiologicalandInterdisciplinaryOceanicStu-dies(SIMBIOS)program(FargionandMcClain,2002;McClainetal.
,2002)whichprovidedprocessingalgorithms,insitudatasets,andmuchguidance.
Thepurposeofthispaperistoreviewtheoriginalsciencegoalsandprojectobjectives,out-linetheapproachespursuedtoachievethem,andassess(asquantitativelyaspossible)theoveralllevelofsuccessinattainingthem.
Duringthe12-yearhistoryoftheSPO,anumberofinnovativeapproacheshavebeendevelopedinaddressingcertainproblems,e.
g.
,thelunartime-dependentcalibrationcorrection.
Insomecases,theSPOhasneededtoadjustitsapproachwheninitialstrate-giesprovedineffectiveortotakeadvantageofnewtechnology,e.
g.
,theevolutionofthedatasystemdesign.
Intheend,itishopedthattheSeaWiFSprogramcanbeusedasamodelforfuturemissionsandthattheinfrastructuretheSPOhelpedestablishcanbecontinuedandexpandedinanticipationoffuturemissionssuchastheNationalPolar-orbitingOperationalEnvironmen-talSatelliteSystem(NPOESS)PreparatoryProject(NPP).
2.
Projectphilosophy,functions,andapproachesBecauseSeaWiFSwasadata-buyratherthanastandardNASAmission,theSPOwasestablishedintheEarthScienceDirectorate(Code900)atGSFCwithalmostallelementsoftheSPObeingco-locatedandleadbyoceanscientists.
Byhavingscientistswithvestedinterestsinthedataaselementleaders,acommitmenttodataqualityanddataaccess,andafocusonresearchanddevelopmentineveryaspectofthemissionwasensured.
WhiletheSPOmanagersandelementleadershavebeencivilservants,themajority(roughly80–90%inthepostlaunchphase)oftheSPOpersonnelhavebeenon-sitecontractorsprovidedundersupportservicescontractsdened,competed,andnegotiatedbytheSPOmanage-ment.
ThishelpedensurethattheSPOreceivedthebestsupportpossible.
Nonetheless,trainingwasnecessary,asthemajorityofthecontractstaffARTICLEINPRESSTable1OriginalSeaWiFSprogramgoalsandprojectobjectives(Hookeretal.
,1992)SeaWiFSprogramgoalsSeaWiFSProjectOfceobjectives1.
Todeterminethespatialandtemporaldistributionsofphytoplanktonblooms,alongwiththemagnitudeandvariabilityofprimaryproductionbymarinephytoplanktononaglobalscale2.
Toquantifytheocean'sroleintheglobalcarboncycleandotherbiogeochemicalcycles3.
Toidentifyandquantifytherelationshipsbetweenoceanphysicsandlarge-scalepatternsofproductivity4.
Tounderstandthefateofuvialnutrientsandtheirpossibleeffectsoncarbonbudgets5.
Toidentifythelarge-scaledistributionandtimingofspringbloomsintheglobaloceans6.
Toacquireglobaldataonmarineopticalproperties,alongwithabetterunderstandingoftheprocessesassociatedwithmixingalongtheedgeofeddiesandboundarycurrents7.
Toadvancethescienticapplicationsofocean-colordataandthetechnicalcapabilitiesrequiredfordataprocessing,management,andanalysisinpreparationforfuturemissions.
1.
ToserveastheNASAliaisontoOSCfortheprocurementofSeaWiFSdatafortheoceanographicresearchcommunity2.
TofacilitatetheoperationandschedulingoftheSeaWiFSsensorsystem3.
Todevelopandvalidatealgorithmsforbio-opticalpropertiesandatmosphericcorrection4.
TocharacterizeandcalibratetheSeaWiFSsystemandtoassesson-orbitperformance5.
Toachieveradiometricaccuracytowithin5%absoluteand1%relative,water-leavingradiancetowithin5%absolute,andchlorophyll-aconcentrationtowithin35%overtherangeof0.
05–50.
0mgm36.
Tocollect,archive,andprocessrecordeddata,aswellasglobalmapsofbio-opticalpropertiesandchlorophyll-aconcentrationfortheresearchcommunity7.
Toprovidequalityassurancemonitoringof,andcoordinatecollectionof,directbroadcastdatabyNASA'sselectedLACreceivingstations8.
TosupporttheSeaWiFSScienceWorkingGroup(SWG).
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–427werefromothersciencedisciplines.
Forinstance,theCVelementconductedacomprehensiveliteraturereviewtofamiliarizethestaffwithallaspectsofocean-colorsatellitecalibrationandalgorithmdevelopment,aswellasthecommunitywithwhomtheywouldbeworking.
TheSPOhasbeencommittedtoanumberofspecicobjectives(listedbelow)relatedto,butnotexplicitlyidentiedin,theoverallSeaWiFSprogramobjectivesoutlinedinTable1.
ManyaspectsoftheSeaWiFSprogramwerearesultofthelessonslearnedfromtheproof-of-conceptCZCSprogramandincludethefollowing.
1.
Acomprehensivecalibrationandvalidationprogramspanningtheentiremission.
FortheCZCS,thepostlaunchcalibrationandvalida-tionprogramwassupportedforonlytherstyearand,therefore,didnotincludetimeseriesobservationstotracksensorperformance.
Inaddition,theeldprogramforalgorithmdevelopmentwaslimitedmainlytoareasnearNorthAmerica.
2.
Rapiduseraccesstodataproducts.
CZCSdatadidnotbecomegenerallyavailableuntiltheglobalreprocessingwascompleted(Feldmanetal.
,1989),severalyearsafterdatacollectionended.
3.
Availabilitytotheusercommunityofalowcostdataprocessingcapability.
TheNimbusProjectdidnotprovidedataprocessingtools,noteventotheNimbusExperimentTeam(NET).
Asaresult,individualgroupsindepen-dentlydevelopedtheirownsoftwaresuchasSEAPAK(McClainetal.
,1991a,b,1992a)andtheUniversityofMiamiDSPsoftware.
4.
Theabilitytoreprocesstheentiredatasetonaroutinebasis.
TheCZCSreprocessingrequiredtheentiredatasetbestagedonopticalmediafromover30,0009-tracktapes.
Thisprocessalonetookoverayeartocomplete.
Thevicariouscalibrationoftheentiredatasetrequiredprocessingthedatamanytimestogetconsistentresults(EvansandGordon,1994)andtookasimilaramountoftime.
Thenalprocessingandqualitycontroltookatleastanotheryear.
Recently,theCZCSdatawasreprocessed(atreducedresolution)byGreggetal.
(2002)tobeconsistentwiththethirdSeaWiFSreprocessingin2000.
5.
Theprocessingsystemmustbetightlycoupledtothescience.
NoneoftheNETmemberswerelocatedatGSFCwheretheprocessingwasbeingconducted.
NETmeetings(Acker,1994)providedopportunitiestoreviewresultsandadvisetheNimbusProject,butthesemeetingswererelativelyinfrequent.
WhilenoneoftheSPOstaffweremembersoftheNET,manyhadworkedextensivelywiththeCZCSdataandsomehadworkedcloselywiththeNETinthepostlaunchperiod.
Thus,therewasanunderstandingofwhatneededtobedonediffer-entlyinanoperationalsettingasopposedtoaproof-of-conceptscenario.
Specically,particularattentionwaspaidtothefollowingstrategies.
1.
Directcommunityinvolvementin,andawarenessof,allSPOactivities.
Thishasbeenaccom-plishedthroughopenprojectreviews,work-shops,calibrationanddataanalysisroundrobins,periodicprojectstatusreportsbroad-casttothecommunity(especiallyimportantintheprelaunchphase),annualscienceteammeetings,professionalconferencepresenta-tions,andsupportofaSeaWiFSboothatmajorUSconferences.
TheSPOhasreliedonthecommunitytoprovidetheatmosphericcorrectionandbio-opticalalgorithmsandmostoftheinsitudata(atmosphericandbio-optical)foralgorithmdevelopmentandpost-launchproductvalidation.
Tonalizethechlorophyll-aalgorithmbeforelaunch,aspe-cialworkshopinvolvinginsitubio-opticaldataprocessingandrealtimealgorithmcompar-isonswasconductedattheUniversityofCalifornia/SantaBarbara([91]O'Reillyetal.
,1998).
Duringeachofthefourreprocessings,theSPOactivelysoughtthecommunity'sinputbyhostingworkshopsandpostingdescriptionsandanalysesofproposedprocessingmodica-tionsonSPOWebsites.
2.
Rapidturnaroundandeasyaccesstodataproducts.
Thegoalwastoprocessthedataonasame-daybasiswithreleasetothesciencecommunityattheearliestpossibletimeallowedunderthedata-buycontract.
OneapproachARTICLEINPRESSC.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–428wastodesignthedataformatstobeself-describingwiththerelevantancillaryandcalibrationdatalescross-referencedandautomaticallydistributedwiththeasso-ciatedimagedatale.
Dataselectionwassimpliedwithon-lineimagebrowsing.
3.
Focusonafewkeygeophysicalproducts.
Thenumberofarchiveproductswaskepttoafairlysmallnumberofkeygeophysicalparameterswithoneproductperparameter.
Also,asinglesetofdataqualitymasksandagswasused.
Theproductsuitewasrevisitedateachreprocessingtoremoveproductsoflittleinterest(e.
g.
,CZCSpigment)andaddothers(e.
g.
,photosyntheticallyavail-ableradiation,PAR)basedoncommunityinput.
4.
Affordableuser-friendlyend-to-endprocessingtoolsforthemostcommoncomputersystemsusedbythesciencecommunity.
ThiswasconsideredessentialifthedataweretobefullyexploitedandresultedintheSeaWiFSDataAnalysisSystem(SeaDAS).
SeaDASwasprimarilysupportedunderseparatefundingfromtheNASAoceanbiogeochemistrypro-gram,buthasrequiredadditionalSPOinvol-vementandnancialsupport(hardware,systemadministration,andSeaWiFSsoftwaretechnicalsupport).
5.
Sciencequalitydatabytheendofthe90-daydataacceptanceperiodwithoccasionalreproces-sings.
TheCVelementimplementedacompre-hensivesetoftestandevaluationcriteriaandanalysissoftwarepriortolaunch.
Duringthepostlaunchdata-acceptanceperiod,allcriteriawerequantitativelyevaluated,andtherstreprocessingwasinitiatedimmediatelyafter-wards.
Threesubsequentreprocessingsincor-poratedcalibrationandalgorithmupdatestofurtherimprovethedataquality.
6.
FulldocumentationanddisclosureofSPOsupportedactivities,operationalalgorithms,sensorcharacteristics,etc.
TheSPOhassupportedafull-timetechnicaleditorsinceearlyintheprogramandhaspublishednearly70technicalreports,plusnumerousconferenceandjournalpapers.
Thesedocu-mentshavebeendistributedatthetimeofpublicationtoasubscriberlistofnearly500individuals.
7.
Arigorousscrutinyofallaspectsofocean-colorremotesensingtechnology,measurementscience,andalgorithmdevelopmentwithanemphasisoninnovationandimprovingthesciencecommunity'stechnicalinfrastructureandabilitytosupportocean-colorsatellitemissions.
Thishasbeenaccomplishedprimarilythroughactivitiessuchasthecalibrationanddataanalysisroundrobins,measurementpro-tocoldevelopment,insituinstrumenttechnol-ogydevelopment,andtheSeaWiFSBio-opticalArchiveandStorageSystem(SeaBASS).
Also,whiletheproject'sCVstaffneededtobefamiliarwithallprocessingalgorithmsandknowledgeableoftherelatedscienticlitera-ture,algorithmdevelopmentwaslefttothesciencecommunity,sotheSPOwouldbeimpartialinitsindependentimplementationandevaluationofalgorithms.
Oneexceptionisthelunarcalibrationalgorithmusedtotrackthesensor'sstability,whichwasdevelopedbySPOstaff.
Thismethodologycontinuestoberenedand,withrecentUSGeologicalSurveyhigh-resolutionreectancemodelsofthelunarsurface,mayprovideabsolutecalibrationsofthesensor.
8.
SPOexibility,evolution,andaccountabilityinitsapproachtoscienticandoperationaldevel-opmentactivities.
EachSPOelementmanagerwasgivencompletecontrolondeningthetechnicalapproach.
Asaresult,allelementsadoptedastrategyofcontinualevolutioninthetechnologiesandapproachestobepursued.
Forinstance,thedataprocessingelementhasannuallyexpandedandreplacedsystemstocontinuallyupgradewithnewtechnology.
Infact,theoriginalSPO-widecomputingdesignwasthreeUnixserversconnectedtoX-terminals.
Overtime,theX-terminalswerereplacedbyUnixworkstations,whichhaverecentlybeenreplacedbyPCLinuxsystems.
Toensurecommunicationbetweenelementsandwithmanagement,especiallyinthepre-launchphase,theSPOconductedperiodicopenreviews(roughlyevery6months)ofeachSPOelementwithmembersofthestaffgivingARTICLEINPRESSC.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–429overviewsofthecomponentstheywereresponsiblefordeveloping.
9.
Communitysupportanduserservices.
TheSPOsawthecommunityasavestedpartnerandrecognizedthatoverallsuccesswouldbelargelydeterminedbythecommunity'sattitudetowardstheSPO.
Withtheelementleadsbeingactivescientists,theyunderstoodthecommu-nity'sneeds.
ExamplesofsupportservicesincludeSeaDAS,near-real-timeimagesupport,andthepre-andpostlaunchSeaWiFSTechni-calReportSeries(STRS).
10.
Fiscalaccountabilityandopenness.
ThebudgetguidelinesfortheSPOandeachSPOelementwereestablishedwhentheSPOwasorganizedandapprovedbyNASAHeadquarters.
TheallocationsfortheSPOelementshavenotchangedsincethen,althoughsomeelementshavemergedovertime.
Eachelementmanagerwasgivencompletecontroloverthebudgetforthatelement,whichgavetheelementmanagertheabilitytoadjusthisbudgetprioritiesovertime,e.
g.
,manpower,hardware,universitygrants,internationalagreements,andcon-tracts.
TheSPOhasalwaysbeencommittedtooperatingwithinbudgetandnotrequestingadditionaloverguidefunding.
Becauseofthelaunchdelay,however,aone-timerequestforoverguidefundingwasmadeandapprovedinordertohaveatfundingduringtheopera-tionalphase.
11.
Newproductsandapplicationsbeyondoceanbiogeochemistry.
TheSPOhasstriventopromotetheusefulnessofSeaWiFSdatabyexploringnewocean,terrestrial,andatmo-sphericproducts,manyofwhicharepossiblebecausethesensordoesnotsaturate,evenoverbrightlandandclouds.
Afterthethirdreprocessingin2000,theSPObeganroutineproductionofanumberof''evaluation''products,e.
g.
,PARandcolordissolvedorganicmatter(CDOM),forthecommunitytoconsideraspotentialarchiveproducts.
Theevaluationproductswerederivedusingalgo-rithmsprovidedbythecommunity.
TheSPOhasworkedwithresearchersintheatmosphericandterrestrialsciencecommunitiestoprovideproductssuchasaerosolopticalthickness(AOT)andthenormalizeddifferencevegeta-tionindex(NDVI).
SubsetsovertheMODISlandvalidationsitesfortheentiremissionareavailableviatheSeaWiFSWebsite.
ExamplesofsuchinterdisciplinaryuseofthedataareBehrenfeldetal.
(2001),Wangetal.
(2000),andChouetal.
(2002).
12.
TightlycoupledandhighlyinteractiveSPOelements.
Itwasrecognizedthatallelementswereinterdependentandrequiredahighdegreeofcommunicationandmutualunderstanding.
Forexample,near-realtimequalitycontrolproceduresbytheCVelementwereembeddedinthedataprocessingsequenceandaffectedtheprocessingsystemdesignandthroughput.
Missionrequirements.
TheSeaWiFSprogramgoalsandprojectobjectives(Table1)wereconsideredtoberequirementsorcriteriaformissionsuccess.
13.
SPOfocusonmissiondeliverables.
Thestaffhasalwaysfocusedonimprovingservicestothecommunity,theaccuracyofthedataproducts,andoutreach.
TheSPOhaspurposelyavoidedcommittingprojectresourcestoinvestigationsofoceanorEarthscience,althoughstaffoccasionallyassistgroupsingettingaccesstodataproductsforspecicstudies.
ThefollowingsectionsoutlinetheactivitiesandaccomplishmentsoftheSPOorganizationalele-ments.
OneoftheimportantaspectsoftheSPOisthatallelementsareco-locatedallowingcontinualcommunicationbetweenthegroupsandthesharingofresources(personnelandequipment).
Co-locationalsohelpstheSPOtobeveryefcientintermsofdecisionmakingandoversightofSPOactivities.
Theorderofthesectionsreectthedataow,i.
e.
missionoperations,datacapture,calibrationandvalidation,dataprocessing,anddataarchivalanddistribution.
Fig.
1providesagraphicaldescriptionofthedatahandlingprocess.
2.
1.
MissionoperationsanddatacaptureThegoaloftheMOelementoftheSPOwastomaximizethecollectionofscienticallyusefuldatafromtheSeaWiFSinstrumentthroughacloseworkingcollaborationwiththeengineersandARTICLEINPRESSC.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4210missionplannersatORBIMAGE,theotherelementsoftheSPO,andtheglobalocean-colorcommunity.
WhileORBIMAGEisresponsiblefortheactualoperationsoftheOrbView-2spacecraftandSeaWiFSinstrument,NASAhastherespon-sibilityfor(a)SeaWiFSinstrumentcommandschedulingandonboardrecordermanagement;(b)navigation,includingpositiondetermination,attitudedeterminationandgeolocation(PattandGregg,1994;Pattetal.
,1997;Patt,2002);and(c)routinespacecraftandinstrumenthealthandsafetymonitoring.
ArepresentativedailySeaWiFSdatacollectionscheduleispresentedinFig.
2.
Toaccomplishthedataacquisitiontasksin-dicatedinFig.
2,NASAisresponsibleforprovidingORBIMAGEwiththespecicschedul-ingrequirementseachweekfordatacollectionbytheSeaWiFSinstrumentincludingdeningtheoperatingparameters(gain,tilt,start/stoptimes,targets),calibrationactivities(solar,lunar,time-delayintegration)andcoordinatingthedownlinkscheduleswiththeprimaryS-banddownlinksiteatNASAWallopsFlightFacility(WFF).
ORB-IMAGEintegratesNASA'sschedulingrequire-mentsintotheirroutinespacecraftoperationsschedulesthatarethenprovidedbacktotheMissionOperationsgroupfornalvericationbeforeuplinktothespacecraftbyORBIMAGE.
Specialrequirements—suchasspacecraftemer-gencies,downlinkschedulingconictsatWFFandrequestsforhighdatarateacquisitionoftelemetryinformationtohelpresolvepotentialspacecraftanomalies—arehandledonacase-by-casebasis.
Extensiveprelaunchend-to-endsystemtests,andregularpostlaunchcommunicationswithORB-IMAGE,includingjointannualreviews,haveresultedinasmooth,efcient,andmutuallybenecialcollaboration.
Overthe51/2yearsofoperation,therehavebeenapproximately20unscheduledsafe-haveneventsduetoonboardsystemanomaliesthathaveresultedinsomelossofsciencedata.
Duringtheseevents,theSeaWiFSinstrumentisstowed,andthemajorityoftheOrbView-2systemsareputintoa'protective'posturewaitingforasignalfromgroundcontrollerstoresumeroutineoperationsafterwhatevereventthattriggeredthesafe-havenisidentied,analyzed,andthecorrectiveactionsneededforfullrecoveryareexecuted.
Themajorityoftheseeventshavebeenassociatedwithsingle-eventupsetsinoneofthespacecraftelectronicsubsystems,andmostoftheseeventshavebeenARTICLEINPRESSFig.
1.
SeaWiFSdataowfromsatellitetodatauser.
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4211showntooccurwhilethespacecraftisyingthroughtheSouthAtlanticAnomaly,anareaeastofArgentinawheresolarparticleuxesareelevated.
Asknowledgeoftheseeventsdeveloped,andascondenceintherecoveryprocedureswasimproved,thedurationbetweentheonsetofsafe-haveneventsandfullrecoveryhasgreatlydecreasedsuchthatmosteventsarerecoveredwithin12h.
Inadditiontotheseunplannedevents,thespacecrafthasbeenintentionallyplacedintoaprotected,safe-havenpostureduringthepeakactivityperiodsofthepastfourLeonidmeteorshowersasaprecautionarymeasure.
Inspiteoftheseunplannedinterruptionstonormalopera-tions,however,morethan98.
5%ofthepotentiallyavailabledatahasbeensuccessfullyacquiredandprocessed.
TheMOelementworkswithORBIMAGEintrackingthehealthofthespacecraftandtheSeaWiFSsensor.
Eachconducttheirownevalua-tions.
TheMOelementcarriesoutregularanalysesofthespacecraftandinstrumenttelemetrywitheachdownlinkandpoststhisinformationontheWeb.
Dailyandlong-termplotsofthebehaviorofthemajoronboardsubsystemsincludingbatteryperformance,horizonsensorparameters(phaseandchord),telescopemotortemperatureandcurrent,sun-sensortelemetrytrends,andmomen-tumwheelperformancearetrackedandpermitcontinualassessmentofthehealthandsafetyofthespacecraftandinstrument.
Theseanalysesarealsocrucialinmaintainingfunctionalityandimprovingtheperformanceofthespacecraftovertime.
Manyoftheprelaunchconcernsaboutthelongevityofanumberofthespacecraftsystemswerecompletelyresolvedthroughtheseanalyses.
Plansforanextendedmissionbeyondtheoriginal5yearshaveusedthelong-termtrendanalysestoassessthepotentialviabilityofthespacecraftandinstrument.
Presently,thereisnoindicationofanysignicantdegradationinthespacecraftsubsystems.
Tomeetthemissiongeolocationaccuracygoal(lessthanonepixel),membersoftheSPOARTICLEINPRESSFig.
2.
SeaWiFSdataacquisitionon1January2002.
Illustratedarethestandard14orbitsofGACdatacollectedeachday(purpleshading),thespecichigh-resolutionLACtargets(blueshadingwithwiderswaths),dailytime-delayintegrationandsolarcalibrationdata(shortLACswathsathighsouthernlatitudescoloredred)andthetwoS-banddownlinkopportunities(red)overtheUSeastcoast.
TheGACdatacollectionistruncatedatscananglesof745.
ThelimitedonboardLACcoverage(B10minperday)isscheduledinadvancetocoverin-watercalibrationtargets(whiteelipsesorcircles),shipsofopportunitycollectingvalidationdata,thesolarcalibrationdata,andregionsofeitherspecicscienticinterest(whiteboxes;lowestpriority).
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4212developedanintimateworkingknowledgeofthespacecraftdesignandoperation,especiallytheattitudecontrolsystem(ACS).
OrbView-2hasarelativelysimpleACSthatconsistsofredundantsetsofsunandhorizonsensorsthatareusedtodeterminethepitch,roll,andyawofthespacecraft.
Moresophisticatedsatelliteshavestartrackersandgyroscopes.
TheACSsensorsprovideinputthatisusedtocontrolthemomentumwheelsandtorquerods(coilsthatworkofftheEarth'smagneticeld)thatadjustthespacecraftattitudetomaintainthesensoratanadirorientation.
MaintainingtheACSinanoptimalcongurationincludesperiodicadjustmentsofsomesensorparametersandnetuningofsensoralignments.
BilanowandPatt(2004)provideasummaryofsomeofthemajorSPOcontributionstothespacecraftACSsupport.
Inaddition,anautomatedtechniqueofislandtargetmatchingwasdeveloped(Pattetal.
,1997)andtheresultsarecontinuallyupdatedandpostedontheMissionOperationsWebsitewiththeresultingimprovementstothenavigationsoftwareincorporatedintotheoperationalandSeaDASnavigationproceduresasappropriate.
Overthelifeofthemission,anaverageofapproximately50islandtargetsperGACswathhavebeenacquiredandanalyzed.
Forthe1.
1kmHRPTdatathattheSPOroutinelyreceives,anaverageofmorethan100targetsperscenearematched,yieldinganaverageerrorof1.
03km,meetingthemission'sgeolocationrequirement.
TheSeaWiFSinstrumenthasanominalresolu-tionof1.
1kmatnadir,butbecauseoflimitationsinonboardstorageandtelemetrytechnologyintheearly1990s,itwasnotconsideredcosteffectivetostoreanddownlinktheglobal1-kmdataset.
Consequently,thefull-resolutiondataaresub-sampledbyeveryfourthpixelandeveryfourthline,andthisglobaldatasetisstoredonboardwithlimitedamountofhigh-resolutiondata.
Twiceperday,atapproximatelylocalnoonandmidnight,thespacecraftdownlinkstherecordeddataasitpassesoverWFF.
Tominimizesingle-pointfail-uresthatwouldresultinanirrecoverablelossofsciencedata,theSPOinstalleditsowndualSandL-bandreceivingstationatGSFCpriortolaunch.
ThisfullyautomatedreceivingstationservesastheprimaryL-bandreceivingstationfortheUSEastCoastandastheS-bandbackupfortheprimarystationatWFF.
Foranumberofreasons,includingconictsatWFFcausedbySpaceShuttleoperationsandantenna-relatedissues,thestationatGSFCfrequentlyservesastheprimarydatatelemetrysiteandhasnotmissedasingledownlink.
InadditiontothetwoNASAstations,theSPOcollaborateswithanetworkofapproximately124L-bandreceivingstationsaroundtheworldthatareafliatedwithuniversities,researchorganiza-tions,andotherspaceagenciestocollecttheLACdatathatarebroadcastasthespacecraftpassesoverthestationsseveraltimesperday.
ThevastmajorityofthesegroundstationsareindependentandarenotsupportedwithNASAfunds.
TheSPOprovidesthecoordinationbetweenthegroundstationsandORBIMAGEforreal-timedecryp-tionofthedatainsupportofresearchactivitiesordemonstrationprojectsandthroughNASA-pro-videdsoftware.
Thissoftwareisdistributedtothegroundstations,andfacilitatesthecollection,processing,archiveanddistributionofdatacollectedbythesestations.
Undertermsofthedata-buycontract,NASAisauthorizedtocollectanddecryptSeaWiFSdatainnear-realtimefromany12ofitsauthorizedreceivingstations(inadditiontothestationatGSFC)atanygiventime,whiletheremainingstationsareallowedtocollectSeaWiFSdata,butmustwaitatleast14daysbeforeORBIMAGEprovidesthemwiththeappropriatedecryptionkeys,whichallowsthemtoprocessthedata.
Atpresent,therearefourstationscoveringthecontinentalUSthathavebeengrantedpermanentreal-timelicenses,anequalnumberofinternationalstationshavelong-termoatinglicenses,andfourshort-termoatinglicensesareavailableat2-weekintervalstosupportspecicnear-shoreresearchactivitiesnotcoveredbytheexistingnear-real-timestationsorforship-basedreceivingstations.
ThesuccessofthisactivityisquiteremarkableandhasfarexceededtheinitialSPOgoalofcoordinatinganetworkof12receivingstationsasoutlinedinthecontract.
Todate,theSPOhasreceivedapproxi-mately128,000HRPTlesfrom88receivingARTICLEINPRESSC.
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McClainetal.
/Deep-SeaResearchII51(2004)5–4213stations.
LiketheGACandonboardLACdata,thesearequalitycontrolledandtransferredtotheGSFCDistributedActiveArchiveCenter(DAAC)fordistribution.
2.
2.
CalibrationandvalidationprogramAsoutlinedearlier,thescienticapplicationsofsatelliteocean-colordatarequireanextremelyhighradiometricaccuracyofboththesensorcalibrationandthederivedwater-leavingra-diances.
Becauseofthesestringentaccuracyrequirements,acomprehensivecalibration,valida-tion,andqualitycontrolprogramwasconceived(McClainetal.
,1992b,1996)fortheSeaWiFS,whichwouldcontinuethroughoutthemission.
Theprogramincludedsensorcalibrationandcharacterization(pre-andpostlaunch),bio-opticalalgorithmdevelopment,atmosphericcorrectionalgorithmdevelopment,postlaunchnear-real-timequalitycontrol,andaeldmeasurementprogramthatincludedsupportformooredbuoys(e.
g.
,theMarineOpticalBuoy,MOBY),oceanographicresearchcruises(e.
g.
,theCaliforniaCooperativeFisheriesInstitute,CalCOFIsurveys),andtimeseriesstations(e.
g.
,theBermudaAtlanticTime-seriesStation,BATS).
TheSeaWiFSCVelementhadabudgetprolethatpeakedataround$2millionperyearearlyintheprograminanticipa-tionofa1993launchanddeclinedby1997toasteadylevelofabouthalfofthepeakyearfunding.
TherationalewastotakeadvantageoftheMODISOceanTeamactivities,whichwerealsointheearlyphasesofdevelopment,andacceleratesomeoftheiractivities,e.
g.
,theatmosphericcorrectionalgorithm,withadditionalfundingtomeettheearlierSeaWiFSlaunchschedule.
For-tuitously,astheSeaWiFScalibrationandvalida-tionbudgetbegantorampdownwards,theSIMBIOSprogramwasinitiatedin1996asaresultofdroppingtheEOSColormission,aseconddata-buytofollowSeaWiFS,fromtheEOSprogram.
SIMBIOSincludedanumberofdatacollectioninvestigationsbyaseparatescienceteamandtheSIMBIOSProjectOfce,whichprovidedamuchmorediverseglobalbio-opticalandatmosphericdatasetthanwouldotherwisebeenavailable(McClainandFargion,1999;FargionandMcClain,2002).
TheamountofdataprovidedwasgreatlyincreasedbytheSIMBIOSProject'ssupportofbio-opticalandsunphoto-meterinstrumentpoolsanditsaugmentationoftheAerosolRoboticNetwork(AERONET;Hol-benetal.
,1998)with12coastalandislandsites.
Acriticalstepinachievingthenecessaryradianceaccuraciesistohaveawell-characterizedsatelliteinstrument.
Duringtheprelaunchphase,considerableattentionwasfocusedonthecalibra-tionandcharacterizationoftheSeaWiFSinstru-ment(Barnesetal.
,1994a,b;Johnsonetal.
,1999a).
Afterlaunch,abroad-basedeldprogramisrequiredforon-orbitcalibrationandproductvalidation.
TheseactivitiesduringtheCZCSerareliedexclusivelyonasmallnumberofshipandaircraftcampaigns,whichprovedtobeinadequatetosufcientlyquantifythedegradationintheCZCSinstrument(EvansandGordon,1994).
Itwasalsorecognizedthatthesensorcharacteriza-tionandelddatasetsmustbeinternallyconsistent,readilyavailable,andwellorganizedinordertoexpeditealgorithmdevelopmentandpostlaunchvalidation.
ThisledtotheSeaWiFSIntercalibrationRound-RobinExperiments(SIR-REX),thebio-opticalmeasurementprotocols,andthedevelopmentofSeaBASS(Hookeretal,1994;WerdellandBailey,2002),whichwassubsequentlyexpandedtoincludeatmosphericvalidationdataunderSIMBIOSsupport(Fargionetal.
,2001).
Inthepostlaunchphase,thecalibrationroundrobins,bio-opticalprotocoldevelopment,andSeaBASShavebeenlargelysupportedbytheSIMBIOSprogram.
WhiletheSPOpurposelyavoidedalgorithmdevelopment,itdidtaketheleadinorganizingandorchestratingacommunity-widealgorithmdevel-opmentandevaluationthroughaseriesofprelaunchworkshopssuchastheSeaWiFSBio-opticalAlgorithmMini-workshop(SeaBAM;O'Reillyetal.
,1998).
Summariesofeachwork-shopwerepublishedintheindexvolumesoftheprelaunchSTRS.
OncetheSIMBIOSprogramstarted,theannualSIMBIOSscienceteammeet-ingsprovidedaforumforsuchdiscussionsandtheneedfortheSPOtohostworkshopswassuper-ceded,exceptinspecialoccasions,e.
g.
,reproces-singworkshops.
Witheachreprocessing,boththeARTICLEINPRESSC.
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McClainetal.
/Deep-SeaResearchII51(2004)5–4214SPOandmembersoftheusercommunityhavesuggestedprocessingmodications,whichhavebeenopenlydiscussedandevaluatedwiththecommunityatlarge.
Forinstance,thechlorophyll-aalgorithmwasreplacedwiththethirdreproces-sing(O'Reillyetal.
,2000).
OneoftheMODISoceanteamactivitiesthatwasacceleratedfortheoriginalSeaWiFSlaunchschedulewasthedevelopmentoftheMOBY(Clarketal.
,1997).
MOBYwastobetheprimaryvicariouscalibrationsitefortheMODISandSeaWiFSmissionsandwasinitiatedundertheMODISprogram.
TheSPOprovidedsubstantialsupportforMOBYdevelopmentpriortolaunchthroughacontractwithMossLandingMarineLaboratory.
ContinuousMOBYdeploymentsanddatacollectionbeganinJuly1997,justbeforethelaunchofSeaWiFS.
Sincethen,nancialsupportfromtheSPOhasbeenforMOBYmaintenanceshiptime,albeitatamuchreducedlevelthanduringtheMOBYdevelopmentphase.
MOBYhasprovidedacontinuoustimeseriesofhighqualitywater-leavingradiancessincethesummerof1997.
ThestrategiesforusingMOBYhavedifferedsomewhatbetweentheMODISandSeaWiFS.
SeaWiFSisabletoviewthemoonmonthlyatthesamephaseangle,solunardataareusedtocharacterizethetimetrendsinthesensorrespon-sivity(Barnesetal.
,1999,2001)andMOBYdataareusedtoadjusttheprelaunchgains(Epleeetal.
,2001).
MODISisamorecomplexsystemandthelunarmeasurementsandsolardiffusermeasure-mentsanalyzedbytheMODIScharacterizationandsupportteam(MCST)arenotattheprecisionrequiredforocean-colorapplications,soMOBYdataareusedbytheMODISOceansTeamtonetunethetime-dependentcalibrationgainsprovidedbytheMCST.
BythethirdSeaWiFSreprocessingin2000(McClainetal.
,2000a,b),thestrategyforcali-bratingSeaWiFSon-orbitandforvalidatingproductswasfairlymatureandincorporatedavarietyofelementsshowninFig.
3.
Thestrategyincludedrigorousevaluationsofsensorperfor-mancecharacteristicsandcalibrationpriortolaunch,comparisonsofthepre-andpost-launchARTICLEINPRESSSeaWiFSCalibrationStrategyPreflightInstrumentCalibrationandCharacterization(1993-1994)PreflightInstrumentCalibrationRecertification(1997)SeaWiFSLaunchCalibrationRRandProtocolsDevelopmentOnboardCalibrations(timedependencycorrections)VicariousCalibrationandProductValidationTime-seriesEvaluationsSolarCalibrationforaTransfer-to-OrbitComparisonLunarCalibrations(monthly)SolarCalibrations(daily)MOBYCalibrations(bands1-6)Global8-dayClearWaterAnalysisInSituBio-opticalandAtmosphericDataComparisonsCommunity-wideactivitiestoensureconsistentdatafromvarioussourcesIndependenton-orbitcalibrationtestafteroperationsbeganin1997CompletesensorcalibrationandcharacterizationbySantaBarbaraResearchCenterpriortodeliveryofsensortoOSCRecalibrationbyNISTatOSCjustbeforelaunchFig.
3.
SeaWiFScalibrationandvalidationschemeshowingpre-andpostlaunchactivitiesandanalyses.
C.
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McClainetal.
/Deep-SeaResearchII51(2004)5–4215sensorcalibrations(theso-called''transfer-to-orbit''experiment),lunarandsolaranalysesofon-orbitsensordegradation,theMOBY-basedvicariouscalibrationadjustmentstotheprelaunchlaboratorycalibrationgainfactors,time-seriesanalysesofglobalnormalizedwater-leavingra-diancesLWN;atmosphericcorrectionepsilonvalues,andchlorophyllasadditionalsensorstabilityindicators,andmatch-upanalysisofsatellite-derivedversusinsitumeasuredvalues(bio-opticalandatmospheric)forproductvalida-tion.
TheapproachandresultsoftheCVelementhavebeenwelldocumentedintheSTRS,con-ferencepapers,andjournalarticlesasaresultoftheSPO'semphasisoninformationsharing,communityinfrastructuredevelopment,andac-countability.
AllthesedocumentshavebeendisseminatedtoaSPOdistributionlistofapproxi-mately500individuals,universities,andlibrariesandareavailableuponrequestfromtheSPO.
Summariesofresultshavebeenpublished(McClainetal.
,1998,2000a,b;HookerandMcClain,2000;Barnesetal.
,2001,Epleeetal.
,2001)andwillbeupdatedasnewresultsbecomeavailable,e.
g.
,theevaluationsofthefourthglobalreprocessingoftheentireSeaWiFSdataset.
TheoriginalSPOstrategywastorelysolelyoneldbio-opticalmeasurementsforalgorithmdevelopmentandvalidationcollectedbythecommunity,andfundingwasprovidedtoaugmentCalCOFI,BATS,andotherdatacollectionprograms.
Indeed,theoutsideresearchcommunityhasprovidedover50,000biologicalstationsandover5000discretesunphotometerobservations(plus94eldcampaignsofshadow-bandradio-meterdata)toSeaBASS.
Iteventuallybecameapparent,however,thatanumberofinsituinstrumentdesign,calibrationmetrology,mea-surementprotocol,anddataprocessingissuesanduncertaintiescouldnotbeaddressedbysimplyaugmentingongoingeldprograms.
Examplesincludemeasurementsinturbidwaterandproto-colsforabove-watermeasurementsofwater-leavingradiance.
Asaresult,aseparateSPOcapabilityfocusedonunderstandingandreducingtheuncertaintieswasinstituted.
Thenextthreesections—SeaWiFSseatruthdataaccuracycon-siderationsandadvancements;Fieldinstrumentdevelopmentandevaluation;andtheSeaWiFSProjecteldprogram—summarizeanumberofthesubsequentactivitiesandachievementsoftheSPO'seldmeasurementprogram.
Theseactivitiesareinterdependentandwereconductedinparallel,butpartitioningthematerialintothreesectionshelpsfocuseachdiscussion.
2.
2.
1.
SeaWiFSseatruthdataaccuracyconsiderationsandadvancementsEnsuringtheSeaWiFSradiometricretrievalsofwater-leavingradiancearewithin5%overthelifeofthemissionrequiresacontinuingcommitmenttoquantifyingtheuncertaintiesassociatedwiththespaceborneandinsituinstrumentation.
Thismeanstheindividualsourcesofuncertaintyfortheacquisitionofground-truthdatamustbeontheorderof1–2%,orwhatisreferredtomoregenerallyassimply''1%radiometry''.
Thesourcesofuncertaintyforthegroundtruthpartofthetotaluncertaintybudgethaveavarietyofsources:1.
Themeasurementprotocolsusedintheeld;2.
Theenvironmentalconditionsencounteredduringdatacollection;3.
Theabsolutecalibrationoftheeldradio-meters;4.
Theconversionoftheopticalmeasurements(in-waterandabovewater)togeophysicalparameters,e.
g.
,diffuseattenuationandwater-leavingradiances,usedinadataproces-singscheme;and5.
Thestabilityoftheradiometersintheharshenvironmenttheyaresubjectedtoduringtransportanduse.
TheSeaWiFSCVelementhassoughttosystem-aticallyidentifyandquantitativelyaddressasmanyissuesassociatedwithallvesourcesofuncertaintyaswasscallyfeasible.
Theseeffortsareoutlinedbelow.
FortheSPO,therststepintheprocessofcontrollinguncertaintiesinelddatawasestab-lishing,throughconsensusatacommunitywork-shop,andthenpublishingtheSeaWiFSOceanOpticsProtocols(MuellerandAustin,1992).
TheprotocolsareaworkinprogressandandwereinitiallyrevisedinMuellerandAustin(1995),but,ARTICLEINPRESSC.
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McClainetal.
/Deep-SeaResearchII51(2004)5–4216undertheSIMBIOSprogram,haveundergonesubstantialexpansions(Mueller,2000,2002,2003)byhavingthescienticcommunitydecidewhichscienticareaswouldbeupdated.
TheSPOhascontinuallyusedtheprotocolsastherequirementsforallground-truthobservations.
Theuncertaintyincalibrationsisthemostfundamental,becausealltheothersareonlyquantiableiftheradiometersareproperlycali-brated.
Tomaintaininternalconsistencybetweencalibrationsoftheinsitusensors(andtheSeaWiFSinstrumentitself),theSPOrequiredcalibrationtraceabilitytotheNationalInstituteofStandardsandTechnology(NIST)andimple-mentedanongoingseriesofSIRREXactivitiestoinvestigateandminimizecalibrationuncertainties.
IntheprogressionfromthersttothethirdSIRREX(Mueller,1993;Muelleretal.
,1994,1996;respectively),uncertaintiesinthetraceabilitytoNISTforintercomparisonsofspectrallampirradianceandsphereradianceimprovedfrom7–8%to1–2%.
ThefourththroughsixthSIRREXactivitiesfurtherinvestigatedlaboratoryandeldprotocols(Johnsonetal.
,1996,1999a,b;andRileyandBailey,1998,respectively),andshowedthatcalibrationsatanuncertaintylevelofapproxi-mately2%wereroutinelyachievableiftheoceanopticsprotocolswerecarefullyimplemented.
Thisculminatedinadetailedexperimenttoquantifymanysourcesofuncertaintiesnotthoroughlyinvestigatedduringpreviousactivitiesatasingle(commercial)calibrationfacility(Hookeretal.
,2002a).
SubsequentcalibrationexperimentshavebeensupportedbytheSPO(Zibordietal.
,2002a)andtheSIMBIOSprogram(Meisteretal.
,2002,2003).
OneoftheoriginalconceptstobetestedintheSIRREXactivitywastoverifythesourcesandcalibrationsetupproceduresatindividualcalibra-tionfacilitiesforbothspacecraftandinsituinstruments.
Todosorequiredanaccurate,stable,andportableradiometer,aso-calledtransferradiometer,designedspecicallyforSeaWiFScalibrationapplications.
TheSeaWiFSTransferRadiometer(SXR)wasdesignedandbuiltbyNISTaspartofanInteragencyAgreementwiththeSPO.
TheSXRhasbeenproventobeareliabletransferradiometer,withanuncertaintyatallmeasurementwavelengthsofapproximately1.
5%(Johnsonetal.
,1998a).
AfterrepeateduseinSIRREXactivities,theSeaWiFScalibration,andaninternationalintegratingspherecomparison(Johnsonetal.
,1997),theSXRwascommercia-lizedinlimitednumbersanddifferentversionsofthesamedesignarebeingusedinotherround-robinactivitiessupportedbySIMBIOS(acon-tinuationofSIRREX)andtheNASAEOScalibrationprogram.
Instrumentaldriftduetolterdeteriorationandphysicalstresses,whichcancauseshiftsintheopticalalignmentandelectricalcharacteristicsofadevice,mustbequantiedevenifaconcertedeffortismadetominimizetheseproblems.
Toaddressthisproblem,NISTwascontractedtojointlydevelopahighlystableportableeldsource,theSeaWiFSQualityMonitor(SQM;Johnsonetal.
,1998b;Hookeretal.
,1998).
PriortotheeldcommissioningoftheoriginalSQM,manyaspectsofsensorperformanceweremaintainedbytheinstrumentmanufacturerandwerenotroutinelymeasuredbytheindivi-dualinvestigator.
Therstoperationaldeploy-mentoftheSQMdemonstratedtheimportanceofindependentevaluationsofcommercialequip-ment.
Duringthatdeployment,largechangesintheresponsivityofsomeoftheradiometers(asmuchasapproximately25%overa1monthperiod)weredetected(HookerandAiken,1998).
TheSQMhasademonstratedcapabilityofmonitoringthestabilityoflightsensorstowithin1%intheeld(HookerandMaritorena,2000)andwassufcientlysuccessfultobecom-mercializedbytwodifferentcompanies(Hooker,2002).
Regardlessoftheperformanceofaninstrumentintheeld,theabsolutecharacterizationofasensorinthelaboratoryisthestartingpointforalmostallothersubsequentevaluations.
Aftertheconclusionofinvestigatinguncertaintiesinradio-metriccalibrations,theimmersionfactorsofirradiancesensorswereinvestigatedduringSIR-REX-8(Zibordietal.
,2002a),andwerefoundtobeasignicantsourceofuncertainty(morethan10%inthebluedomain,andapproximately2–6%inthegreenandredregions).
Theactivityalsoshoweditwaspossible,however,tomaintaina1%ARTICLEINPRESSC.
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McClainetal.
/Deep-SeaResearchII51(2004)5–4217uncertaintybudgetforcharacterizingimmersionfactors(Zibordietal.
,2004a),especiallywithnewprotocolsbasedonasmallerlaboratoryapparatusandmoretimeefcientprocedures(HookerandZibordi,2003a).
Inparticular,theCompactPortableAdvancedCharacterizationTank(Com-PACT)method,whichusesaverysmallwatervessel(3lversusasmuchas3000lfortraditionalmethods)providesthesignicantadvantageofaquality-assuredandreproduciblevolumeofpurewater(Zibordietal.
,2003).
Theuncertaintiesassociatedwithdataproces-singaretiedtotheprotocols,buttherearesubjectiveaspects,likethechoiceofthein-waterextrapolationinterval,whicharenotcompletelyresolvedbyasingleprotocol.
TherstSeaWiFSDataAnalysisRoundRobin(DARR-94)investi-gateddataprocessinguncertaintiesandshoweddifferencesincommonlyuseddataprocessingmethodsfordeterminingprimaryopticalpara-metersfrominsitulightdatawereabout3–4%oftheaggregatemeanestimate(Siegeletal.
,1995).
TheseresultsappliedprimarilytoCase-1waters,butissuesinturbidwatersremained.
ThefocusofthesecondDARR(DARR-00)wastodetermineiftheseresultscouldbeimproved(Hookeretal.
,2001).
Intermsofoverallspectralaverages,manyoftheDARR-00intercomparisonsweretowithin2.
5%,andiftheprocessingoptionsweremadeassimilaraspossible,agreementtowithinlessthan1%waspossible.
Theopticalparametersdonotaccountforallofthevalidationrequirements.
Forinstance,thedeterminationofchlorophyll-aconcentrationiscentraltotheSeaWiFSprogrampigmentobjectiveofagreementtowithin35%.
Aninitialintercom-parisonoffourlaboratoriesusingfourdifferenthighperformanceliquidchromatography(HPLC)methodsfordeterminingtotalchlorophyll-acon-centrationshowedtheoverallaccuracyofthefourmethodsinpredominantlymesotrophicwaterswaswithin8%(Hookeretal.
,2000a,Claustreetal.
,2004).
Subsequently,amoreextensivepigmentroundrobinofUSlaboratorieswasconductedbytheSIMBIOSProject(VanHeukelemetal.
,2002)andaninternationalroundrobinjointlysupportedbytheSeaWiFSandSIMBIOSProjectsisunder-way(Hookeretal.
,2003a).
2.
2.
2.
FieldinstrumentdevelopmentandevaluationAlthoughtheoriginalcalibrationandvalidationplanningdidnotconsiderinstrumenttechnologydevelopment,thelimitationsoftheexistingcom-merciallaboratoryandeldradiometersandinstrumentmonitoringdevicesforocean-colorremotesensingapplicationsbecameapparentfairlyearlyintheprogram.
Asaresult,theCVelementbeganinvestingininstrumentevaluationinanefforttoaccelerateinstrumentdesignimprovementsandtoidentifysubtleproblemsininstrumentperformanceandcharacterization.
Thisactivityiscloselytiedtothecalibrationroundrobinandmeasurementprotocolactivities.
Forexample,theresultsofSIRREX-8showedthattheimmersionfactorssuppliedbyacommer-cialmanufacturerweremorethan10%inerroratsomewavelengths(Zibordietal.
,2002a),andthereareotherexamplesoftheneedforindependentconrmationofperformancespecicationsintheliterature(e.
g.
,Mueller,1995,HookerandMar-itorena,2000).
Thisactivityhasledtoseveralimproveddesignsforbothabove-andin-watermeasurements.
Fig.
4isamosaicofsomeoftheseinstruments,andTable2providesinformationontheprogressionofdesignsforbothtypes.
Ineachcase,thebasicstrategywastomovetowardsmallerinstrumentpackagesandimprovedradiometricperformanceandmeasurementcongurationknowledge.
Also,forthein-watermeasurements,higherverticalresolutionandsmallersizewasagoal,sotheinstrumentscouldbeusedinmoreturbidwaterswhereverticalgradientsandinstrumentself-shadingcanbeproblematic.
Forexample,intheprogressionfromtheLoCNESStothemicro-NESS,thein-airweightwasreducedbyalmostafactorof6,thecross-sectionalareawasreducedbyalmostafactorof2,andthefull-scaledepthaccuracywasimprovedbyafactorof25.
ThemicroNESSandmicroSASinstrumentsnowpro-videhighlyaccuratemeasurementsofLWNandremotesensingreectance(Rrs)inCase-1andCase-2watersfromanystandarddeploymentplat-form.
Furthermore,asaresultofrigorousrene-mentstoabove-watermeasurementprotocols,recentcomparisonsofabove-andin-watermea-surementsnolongerdifferbyamethodologicalARTICLEINPRESSC.
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McClainetal.
/Deep-SeaResearchII51(2004)5–4218bias—theyagreetowithintheuncertaintyincalibratingtheradiometers(Hookeretal.
,2003b,Zibordietal.
,2004b).
2.
2.
3.
TheSeaWiFSprojecteldprogramTheinstrumentdevelopmentandevaluationactivitiesandmeasurementprotocolexperimentsdiscussedabovewerelinkedtoanextensiveeldprogram.
Theeldprogramrevolvedaroundthreeprimarysetsofeldstudies(collaborations).
TheseweretheBritishAtlanticMeridionalTransect(AMT;Aikenetal.
,2000)program(PlymouthMarineLaboratory),studiesfromtheAcquaAltaOceanographicTower(AAOT)intheNorthernAdriaticSea(theJointResearchCenter,JRC,inIspra,Italy),andvariouscruisesintheMediterra-neanSea,northwestAfricanupwelling,andSouthAfrica(Laboratoired'Oc!
eanographiedeVille-franche,LOV,inVillefranche-sur-Mer,France).
EachcollaborationwasformalizedwithaLetterofAgreement(LOA)betweenNASAandtheinternationalinstitution.
Table3providesasummaryofthemajoreldcampaignsinwhichtheSPOparticipated.
TheAMTcruisestookplaceonboardtheRoyalResearchShipJamesClarkRosswhenitsteamedbetweenEnglandandtheFalklandIslandsinsupportofBritishAntarcticSurvey(BAS)activ-itiesintheSouthernHemisphere.
Theodd-numbered,southboundcruisessampledtheborealautumnandaustralspring;whiletheeven-numbered,northboundcruisessampledtheborealspringandaustralautumn.
Becauseofthegeographicextentofthetransects(morethan100oflatitudeand50oflongitude),therepetitiveschedulingofthecruises(twoperyearlastingmorethan30dayseach),thediversityoftheenvironmentsencountered(oligotrophicgyrestoupwellingzonesandeutrophiccoastalregions),alongwiththeuseofthenewestradiometerdesigns(includingcalibrationmonitoringintheeldwiththeSQM),theAMTProgramwasaparticularlytimelyandsubstantialaccomplish-ment.
DeploymentsontheAMTcruisesweregreatlysimpliedbyhavingtheSeaWiFSPortableLaboratorysecuredtothedeckduringtheoperationsandstoredeitherintheUKortheFalklandIslandsbetweendeployments.
TheSPOalsoprovidedaconductivity–temperature–depth(CTD)systemwith30lbottlestoallowsufcientwatercollectioninhighlyoligotrophicwaters,whichwasusedonfouroftherstninecruisesfromSeptember1995toJune1999.
TheAMTopticalexperimentsweredesignedtocompareavarietyofdeploymenttechniquesusedtomeasuretheinsitulighteldandtoincremen-tallyimprovethemethodsandinstrumentationemployed.
Bothabove-andin-watersensorsandmethodswereevaluatedduringAMTcruises,butthelatterconstitutedthemajorityoftheeffort.
Theculminationofthein-waterexperimentswasademonstrationthattheinsitupartoftheSeaWiFSuncertaintybudget(3.
5%)couldbesatisedwithadedicatedeffortofrecurringcalibrations,stabilitymonitoring,andstrictadherencetotheoceanopticsprotocols(HookerandMaritorena,2000).
FieldexperimentswiththeJRCwereconductedattheAAOT,whichislocatedapproximately15kmsoutheastofthecityofVeniceinthenorthernAdriaticSea.
Thepotentialforusingoceanographictowers,asanalternativetobuoyorshipboardmeasurements,forocean-colorcalibra-tionandvalidationactivitiesisbeingrealizedattheAAOT(Zibordietal.
,1995).
Iftheobserva-tionsareperiodic(monthly),shortdeploymentsareeasilyaccomplishedwiththeformer(Zibordietal.
,2002b),andifamodularin-watersystemthatallowstheremovalofthelightsensorsinbetweenmeasurementcampaignsisused,themostdifcultaspectofmooredsystems—bio-foulingofthein-wateropticalsensors—canbecompletelyeliminatedandahigh-qualitytimeseriescanbeproduced(Berthonetal.
,2002).
Towersandresearchvesselsarenecessarilylargestructures,andtheprimaryadvantageoftheformeroverthelatterisstability.
Opticalinstru-mentscanbedeployedonatowerwithvirtuallynotiltandthesolarilluminationgeometry,whichisneededforanaccurateremovalofsuperstructureshadingeffectsonin-watermeasurements(Zibordietal.
,1999;Hookeretal.
,2002b;Doyleetal.
,2003),canbeaccuratelydetermined.
Thestabilityandabsenceofin-waterdatadegradation(nobio-foulingplustheuseofin-watercorrectionschemesforperturbativeeffectsoreasilyimplementedavoidancemetricsforabove-watermeasurements)ARTICLEINPRESSC.
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R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4220makesAAOTdeploymentsexcellentopportunitiesforabove-andin-waterintercomparisonstoexaminemanydifferentaspectsofmeasurementprotocols.
A1yearintercomparisonofwater-leavingradiancesderivedfromSeaPRISMandanin-watersystem,forexample,showedtheoverallspectralagreementwaswithin10%intheblue–greenchannels(Zibordietal.
,2002c).
Recentimprovementsintheabove-watermethodologythatincorporatebidirectionalcorrectionsandamoreaccuratemodelingofthesurfacereectance(Hookeretal.
,2003b),however,showatimeseriesofdatacanbeconstructedusinganautonomousabove-watersystemthathasanuncertaintyinkeepingwithcalibrationandvalidationuncertain-ties(Zibordietal.
,2004b).
AdditionaleldcampaignsconductedwiththeLaboratoired'Oc!
eanographiedeVillefranchehaveincludedtheProductivit!
edesSyst"emesOc!
eaniquesP!
elagiques(PROSOPE)deep-oceancruisetotheMediterraneanSeaandthenorthwestAfricanupwellingplusasatellitecalibrationcruisetotheBenguelaCurrentoffSouthAfrica(calledBEN-CAL;Barlowetal.
,2003).
Inaddition,theSeaWiFSandSIMBIOSProjectshavecontributedtothedevelopmentofanewtypeofopticalbuoycalledBou!
eepourl0acquisitiondeS!
eriesOptiques"aLongTerme(BOUSSOLE),whichwasoperation-allydeployedintheLigurianSeabetweenFranceandCorsica,andisbasedoncommercial-off-the-shelfsensors(AntoineandGuevel,2000).
CombiningthecarefulmetrologyestablishedduringAMTcruiseswiththeuniqueandwell-establishedcapabilitiesoftheLOVandJRCgroupsresultedinseveraladditionalnoteworthyaccomplishments:1.
Zibordietal.
(1999)measuredtheshadinginducedonin-wateropticalmeasurementsbyalargeoffshoretoweranddevelopedacorrec-tionschemeforthein-watersensors.
2.
Claustreetal.
(2002)demonstratedthatSaharandustdepositionreducedbluereec-tanceandenhancedgreenreectancecausinganomalouslyhighchlorophyllretrievals.
3.
HookerandMorel(2003)quantiedshipreectancecontaminationinabove-watermea-surementsandoutlinedmeasurementprotocolandqualitycontrolproceduresforretrievingdataaccuratetowithin5%.
4.
Hookeretal.
(2002b)conductedtherstrigorouscomparisonofabove-watermeasure-mentandin-watermeasurementmethods.
TheoverallintercomparisonofallmethodsacrossCase-1andCase-2conditionswasatthe9%levelforthespectralaverages.
5.
Hookeretal.
(2003c)mappedtheeffectofanoffshoretowerontheabove-watermethodandestablishedsamplingmetricstopreventdatadegradation(HookerandZibordi,2003b).
IfthesamplingmetricsarecombinedwiththeHookeretal.
(2003b)methodology,theabove-andin-waterdeterminationsofwaterleavingradiancesconvergetowithinthetotaluncer-taintiesinthemethods,about3%(ignoringenvironmentalvariability).
Inadditiontoimprovingtheradiometricreliabilityandaccuracyoftheopticalinstrumenta-tion,thedevelopmentprocessgreatlyincreasedtheamountofdatacollectedduringtheeldcam-paigns.
Forexample,iftheoff-the-shelfapproachofAMT-1isusedasareference,therewasapproximatelya100%increaseinthenumberofradiometricprolescollectedduringAMT-3,a600%increaseduringAMT-5,anda900%increaseduringAMT-7.
SomeoftheseincreasesweretheresultofefcienciesthatarealwaysARTICLEINPRESSFig.
4.
Acollageoftheprimaryabove-andin-wateropticalinstrumentsdevelopedtosupportSeaWiFScalibrationandvalidationeldcampaigns:(A)SeaOPS(theinsetmagnicationshowstheorientationofthethreeopticalsensors);(B)THOR(heldupright)withLoCNESSandminiNESS(ondeck)infrontoftheSeaWiFSPortableLaboratory;(C)microNESSbeingoperationallydeployedforthersttimefromaverysmall(lessthan5mlong)boat;(D)SeaSASconguredtopermittheintercomparisonofthreedifferentabove-watersensordesigns(includingtheprototypemicroSASsensor);(E)SUnSASwiththeDIR-10(directional)unit(thevertical,leftmostcylinder)andtheviewingapertureopen(a25.
4cmplaquecanbettedintotheaperturetoallowforalternativemeasurementprotocols);(F)microSASttedinsideacardanicgimbalandmountedattheendofanextensibledeploymentsystembuiltattheJRC;(G)SeaPRISMbeingoperationallydeployedattheAAOTafter1yearofeldtestingbytheJRC;and(H)eldtestingoftherstgimbaledsolarirradiancereferenceonaverysmallboat.
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4221ARTICLEINPRESSTable2SummaryofeldinstrumentsdevelopedwithsupportoftheSeaWiFScalibrationandvalidationprogramInstrumentCharacteristicsReferencesIn-wateropticalinstrumentsSeaWiFSOpticalProlingSystem(SeaOPS)*Luz;.
e;Edz;.
e;and*Es0;.
e;initially*Euz;.
eaddedlater*Winchandcranesystem(forlargeshipsandplatforms)with16-bitanalog-to-digital(A/D)conversionRobinsetal.
(1996)Aikenetal.
(1998)HookerandMaritorena(2000)SeaWiFSFree-FallingAdvancedLightLevelSensors(SeaFALLS)*Free-falling,24-bitA/Dconversion,integralunit(notmodular)Aikenetal.
(1998)Hookeretal.
(1999)HookerandMaritorena(2000)SeaWiFSSquareUnderwaterReferenceFrame(SeaSURF)andtheSeaWiFSBuoyantOpticalSurfaceSensor(SeaBOSS)*TwodifferentsurfacereferencesystemsthatcanbeoatedawayfromaplatformAikenetal.
(1998)HookerandLazin(2000)HookerandMaritorena(2000)Low-CostNASAEnvironmentalSamplingSystem(LoCNESS)*SameasSeaFALLS,butwithcheapercomponents(16-bitA/D)andmodularAikenetal.
(1998)Zibordietal.
(1999)Hookeretal.
(1999)HookerandMaritorena(2000)THOR*Luz;.
e;Edz;.
e;Euz;.
e*LongerthanSeaFALLS*BuiltforQ-factorstudiesHookeretal.
(1999)HookerandLazin(2000)Barlowetal.
(2003)miniNESS*SmallerthanLoCNESS*SuitableforsmallboatsHookeretal.
(1999)Hookeretal.
(2000b)Doyleetal.
(2003)microNESS*SmallerthanminiNESS*Suitableformoderatelyturbidandshallowwater*DigitalinterfacesHookeretal.
(2003c)Barlowetal.
(2003)Above-wateropticalinstrumentsSeaWiFSSurfaceAcquisitionSystem(SeaSAS)*Suitableforplatformsandlargeships*ManualpointingHookeretal.
,1999HookerandLazin(2000)Hookeretal.
(2002b)SeaWiFSShadowband(SeaSHADE)*RotatingshadowbandsunphotometerforattachmenttoirradiancereferencesensorsHookerandLazin(2000)Hookeretal.
(2003c)SeaWiFSUnderwaySurfaceAcquisitionSystem(SUnSAS)*Suitableforplatformsandsmallships*ManualpointingHookerandLazin(2000)Hookeretal.
(2000b)HookerandMorel(2003)MicroSurfaceAcquistionSystem(microSAS)*Suitableforverysmallships*GimbaledtoreduceplatformmotionHookeretal.
(2003b)Hookeretal.
(2003c)HookerandZibordi(2003b)SeaWiFSPhotometerRevisionforIncidentSurfaceMeasurement(SeaPRISM)*Stableplatformsonly*AERONETcompatiblewithautomatedsatellitedatatransmissionHookeretal.
(2000b)Zibordietal.
(2002c)Zibordietal.
(2004b)Thelistingsunderthein-waterandabove-watercategoriesareinchronologicalorderandrepresentsystematicimprovementsinradiometry,reductionsinsize,and,fortheabove-waterinstruments,moreaccuratepointingknowledge.
Thein-watersystemsmeasureupwellingradiance(Luz;l),downwellingirradiance(Edz;l),anddownwellingsurfaceirradiance(Es0;l;separately).
TheThree-HeadedOpticalRecorder(THOR)includesupwellingirradiance(Euz;l).
Theabove-waterinstrumentsmeasuresurfaceupwellingradianceandskyradiance.
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4222gainedfromrepeatinganyexerciseoverandoveragain,butthemajoritywerethedirectconse-quenceofmodifyingtheequipmentandmethodsused.
Thesemodicationsincludedacustom-builtdataacquisitioncapabilitytopermittherapidcollectionofradiometricdatafromthesimulta-neousdeploymentofmultipleinstruments.
2.
3.
DataprocessingsystemThedesignoftheSeaWiFSdataprocessingsystem(SDPS)incorporatedmanyofthelessonslearnedduringthedevelopmentandoperationoftheCZCSglobalreprocessing(Feldmanetal.
,1989).
TheinitialdesignwasaclosecollaborationbetweentheSPOandtheUniversityofMiamiRosenstielSchoolforMarineandAtmosphericSciences(RSMAS),withtheinvaluabletechnicalsupportfromSiliconGraphicsIncorporated(SGI).
Bydesigningthesystemtosatisfyanumberofwell-speciedrequirementsandthroughaprocessofrapidprototypedevelopmentandextensivetesting,andnewtechnologyevaluation,thesystemhasbeencontinuallymodiedtohandleadditionalrequirements(i.
e.
newproducts,algorithmrene-ments,increaseddatavolumes,andnewsatellitemissions)whilealsoimprovingthesystem'scap-abilitytomeettheoperationalmissionrequirementwithoutrequiringadditionalbudgetsupplementsoverwhathadoriginallybeenrequested.
Theoriginalobjectivewastohaveanabilitytoprocess10timesthereceiveddatavolumesoastohavetheabilitytoreprocesstheentiredatasetwithinareasonableamountoftimewithoutaffectingoperationalprocessing.
Asmentionedearlier,theoriginalSPO-widecomputingdesignwasthreeUnixserversconnectedtoX-terminals.
Evenduringtheprelaunchphase,thisstrategyprovedinadequatetomeetthecomputationalrequirementsandtheSPOreplacedtheX-term-inalswithworkstations.
Theapproachedworkedverywell,butwasexpensiveintermsofhardwareARTICLEINPRESSTable3AsummaryofthemajordeepoceanandcoastaleldcampaignsdirectlysupportedbytheSPOCampaignInvestigator(s)DatesStationsAMT-1S.
HookerandG.
MooreSep.
–Oct.
199525AMT-2G.
MooreandS.
HookerApr.
–May199624AMT-3S.
Hooker,J.
Aiken,andS.
MaritorenaSep.
–Oct.
199630AMT-4S.
HookerandS.
MaritorenaApr.
–May199756AAOTS.
HookerandG.
ZibordiJuly19976AMT-5S.
Hooker,J.
Aiken,andS.
MaritorenaSep.
–Oct.
199747AMT-6BG.
Moore,S.
HookerandS.
MaritorenaApr.
–May199830AMT-6S.
Hooker,J.
Aiken,andS.
MaritorenaMay–June199861SeaBOARR-98S.
HookerandG.
ZibordiJuly19986AMT-7S.
Hooker,J.
Aiken,andS.
MaritorenaSep.
–Oct.
199857AMT-8S.
HookerandS.
MaritorenaMay–June199952SeaBOARR-99S.
HookerandG.
ZibordiAugust19994PROSOPES.
Hooker,A.
Morel,andS.
MaritorenaSep.
–Oct.
199921Coastal-1S.
HookerandJ.
BrownFeb.
–Mar.
200017SeaBOARR-00S.
HookerApr.
–May200030ADRIA-2000S.
Hooker,J-F.
Berthon,andG.
ZibordiJuly200055Coastal-4S.
HookerandJ.
BrownFeb.
–Mar.
200129SeaBOARR-01S.
HookerandG.
ZibordiJune200118BOUSSOLES.
HookerandD.
AntoineJuly20017SeaBOARR-02S.
HookerandG.
ZibordiJune200215BENCALS.
Hooker,J.
Brown,J.
Aiken,andA.
MorelOctober200242TheSeaWiFSBio-OpticalAlgorithmRoundRobin(SeaBOARR)campaignsareassociatedwiththegeneralproblemofinvestigatinghowmethodologicalfactorsinuencethedatausedinbio-opticalalgorithms.
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4223andmaintenance.
Sincelaunch,relativelyinexpen-sive,yetpowerful,PC-basedLinuxsystemshaveemergedandaresystematicallyreplacingthestaff'sworkstations.
TheLinuxsystemsarealsobeingclusteredtoaugmenttheUnixserverstoincreaseoveralloperationalprocessingthroughputasHRPTstationdatavolumeandcalibrationandvalidationevaluationprocessingrequirementsgrow.
Inaddition,process-controlsoftwarehasevolvedfromrelyingsolelyonthecentralserverstobeingabletoutilizeallcomputerresourceswithintheSPO.
Theoriginalproductstobederivedfromtherawdatastream(Darzi,1998)includednavigatedcalibratedradiances(level-1),derivedgeophysicalproducts(level-2;normalizedwaterleavingra-diances,chlorophyll-a,CZCSpigment,diffuseattenuationat490nm,andcertainatmosphericparameters),binnedproductsonaxedgrid(level-3),andstandardmappedproducts.
Level-2productsincludedanumberofmasksandagsthatareusedtoidentifypixelsthatarenotprocessed(e.
g.
,clouds)orindicatesomespecialcircumstance,e.
g.
,shallowwater(McClainetal.
,1995).
Themaskandagsareincorporatedinthelevel-2productsandcanbeindividuallydisplayed.
Someagsareusedasexclusioncriteriaforlevel-3binning.
Changesinthepro-ductsuiteandthemasksandagshavebeeninstitutedatvariousreprocessings.
Forexample,theCZCSpigmentproducthasbeendiscontinued,andPARandNDVIhavebeenadded.
Also,afterthethirdreprocessing,asetofevaluationpro-ducts,e.
g.
,CDOM,wereincludedintheroutineprocessingstreamincollaborationwiththescientistsoutsidetheSPO.
EvaluationproductsaredisplayedonanevaluationproductWebsiteforconsiderationbythecommunity.
Oncethecommunityexpressessufcientinterestinapro-duct,itisgraduatedtoarchiveproductstatusaswasdonewithPAR.
NDVIissuppliedtoaterrestrialresearchgroupatGSFCwhoqualitycontroltheproductbeforesendingittotheDAAC.
BecausetheSDPSwasdesignedfromtheverystarttobeathoroughlyintegratedcomponentoftheSPO,drivenbyscience,dataqualityanddataavailabilityconsiderations(essentiallyabottoms-upapproachdesignedbyscientistsforscientists)ratherthanbyamorecomputerandinformationsystemapproach,i.
e.
atop-downapproach.
TheDPelementhastointeractwithalargenumberofgroupstobeabletocarryoutitsfunctions.
SomeoftheseareinternaltotheSPO(i.
e.
theotherelements),someinternaltoNASA,butphysicallyseparatedfromtheSPO(e.
g.
,DAAC,WFF)andothersoftenhalfwayaroundtheworld,suchastheremoteHRPTreceivingstationsthatcollectandprovidetheSPOwithcopiesoftheSeaWiFSdatatheyreceive.
2.
3.
1.
SystemrequirementsThevekeyfunctionsthatdrovethedesignoftheSDPSrequiredthatthesystemarethefollowing:Processlargevolumesofdatainatimelyfashion.
Byusingrealisticestimatesofprocessing/reproces-singrates,datahandlingrequirements,andthroughveryextensivesimulationofactualend-to-endsystemoperations,potentialbottlenecksinsystemthroughputwereidentiedandcorrectedpriortolaunch.
Theproductsandtheirvolumeswereknownandusedinthesystemdesign.
Theinstrument-andspacecraft-drivendelaysinlaunchweretakenadvantageofbytheSPOtosimulatefullmissionfunctionsfromdownlinktoDAACdistribution,dayinanddayoutforatleastonefullyearbeforelaunch.
Theend-to-endtestingwaspossiblebecausetheMOelementgeneratedsimulatedlevel-0datasets(Greggetal.
,1994).
Itcannotbeoveremphasizedhowabso-lutelycriticalthecomprehensiveprelaunchsystemtestsweretothegenerationofcrediblelevel-1,-2,and-3productsontherstdayofroutineoperations.
Requireaslittlehumaninterventionaspossible.
WhiletheinteractivequalitycontrolofeachandeverySeaWiFSdataproductwasakeydesignrequirement,theinteractionbetweenthesoftwaredevelopedbytheCVgrouptoperformthequalitycontrolandtheDPelementtodealwiththeoutcomeofthatprocesswasoptimizedthroughtheuseofshareddatabasetablesandprocedures.
BecausetheSPOhaddecidedveryearlyintheplanningprocesstomaintainitsownarchiveofthecompletemissiondata(inthiscasebothlevel-0ARTICLEINPRESSC.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4224andlevel-1a),algorithmtestingonlargedatasets,productvalidationsubsceneextractions,andreprocessingscouldproceedwithoutmanyofthecoordinationissuesthathaveimpededotherlargerandmorecomplexmissions.
Allowchangestotheprocessingmethodstobeeasilyimplemented.
Byacknowledgingthatasunderstandingoftheinstrumentandthescienceimproves,therewillbeaneedtomodifythealgorithmsandprocessingprocedures,andthesystemshouldbeabletoaccommodatethesechangesinastraightforwardmannerwithoutaffectingtheoperationalprocessing.
Bydesigningthesystemtohaveparalleldevelopmentandoperationalenvironments,changestothesystemprocedurescouldbeeasilyimplemented,thor-oughlytestedandevaluated,andmigratedintoproductionwithminimalimpact.
Permitmultipleprocessingstreams.
Itiscom-pletelyunrealistictodesignasatellitedataproces-singsystemwithoutprovidingfortheconcurrentprocessingofmultiplestreamsofdata.
FortheSDPS,thesystemwasscopedforaminimumofatleastthreesimultaneousandconcurrentprocessingstreamsforreal-timeoperationalprocessing,completemissionreprocessing,anddevelopmentandtestingprocessing.
Thisanalysisresultedinadesigngoalofbeingabletohavea10overallsystemcapacity(processtendaysofglobaldataperday).
Beeasilyunderstoodanddocumented.
MostinteractionswiththeSDPSarecarriedoutthroughaseriesofsimplegraphicaluserinterfaces(GUI)thatinteractdirectlywiththevariousdatabasesthatcontrolallsystemfunctionssothatevenverycomplexproceduressuchasredeninghowadataleshouldbeprocessed,whatdataproductsaretobeproduced,andatwhatstepintheprocessingeachdatagranuleresidesatanymomentisarelativelysimple,andeasytomanagetask.
ExtensiveWeb-baseddocumentationofallkeysystemcomponents,publicaccesstomostsystemsourcecode,andacomplete,onlinelogofsystem-relatedupdatesmaketheSDPSaveryopen,easilyunderstoodsystem.
Asademonstrationofthis,theentireSDPShasbeenportedtoatleasttwoothergroups(NationalOceanicandAtmosphericAd-ministrationandMODIS)toserve,inNOAA'scase,asanoperationalsystemtoprocessOcean-colorandTemperatureScanner(OCTS)dataandforMODIS,asaprototypedataprocessingsystemtodemonstratetheabilitytoprocessMODISdataoutsideoftheEarthObservingSystem(EOS)DistributedInformationSystem(EOSDIS)CoreSystem(ECS).
2.
3.
2.
SystemdesignThedesignphilosophythatwasusedtodeveloptheSDPSwasquitedifferentfrommostothermajorsatellitemissions.
Onceatop-levelsystemrequirementwasidentied,rapidprototypingofbasiccorefunctionswasusedtodevelopthekeycomponentsoftheSDPS.
Oncetheprototypefunctionhadenoughcapabilitytobetested,acomprehensiveevaluationofitwascarriedout,strengthsandweaknesseswereidentied,andrenementsweremadetoeventuallyconvergeonanalimplementation.
Asaresult,thefunction-alitydevelopedattheverybeginningoftheSeaWiFSprogramevolvedovertimetoincorpo-rateawiderangeofadditionalrequirements.
ThefourmajorcomponentsoftheSDPSarethe(1)database,(2)theServicesLayer,(3)theScheduler,and(4)theVisualDatabaseCookbook(VDC).
TheheartoftheSDPSisarelationaldatabasemanagementsystem(RDMS),whichprovidesallthecontrolling,scheduling,andcatalogingfunc-tionsforthesystem.
TheSDPSusesacommercialoff-the-shelfsoftware(COTS)standardquerylanguageserver(Sybase),butanyRDBMScanbeusedbecauseofthesystem'sdatabaseServicesLayer,whichcontainsallthevendor-specicdatabasefunctions.
IfitweredecidedtouseanotherRDMS,onlytheServicesLayerwouldneedtobeupdatedbecauseitshieldsalltheothersystemfunctionsfromanyRDMS-specicdepen-dencies.
TherearetwotypesofdatabaseswithintheSDPS:coredatabasesandmission-specicdatabases.
Thecoredatabasessupporttheproces-sing,cataloging,andadministrationfunctionswithintheSDPS,whiletheprocessingdatabase'sprimaryfunctionistoprovidecontrollingandschedulingfunctionsfortheSDPS.
Forscheduling,atablecalledtodolistisused.
Thistablecontainsrecordsthatdescribejobs(tasks)thatneedtobedoneforthecurrentday.
ARTICLEINPRESSC.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4225Thetask'sattributesdenethecharacteristicsofthejobsuchasitstype,whenitshouldberun,whichmachineitshouldrunon,anditsstatus.
Taskscanrunatsetintervalsoftime(monitortasks),ataspecictime(timedtasks),orbetriggeredbysomeevent(triggeredtasks).
TheSchedulermonitorstherecordsinthetodolisttable,andsubmitsjobstotheoperatingsystemattheappropriatetime.
Whenataskcompletes,successfullyorunsuccessfully,itrecordsitsstatusinthetodolisttable.
Atanypoint,anewtaskcanbeadded,unwantedtaskssuspendedordeleted,ortasksrescheduledthroughtheTaskEditorGUI.
Tasksnotcompletedonanygivendaymayberolledovertothenextdaywhenthesystemreconguresitselfeachnightatmidnight.
Forinstance,datatransfersbetweenremotereceivingstationsandtheSPOcanoftentakeseveralhoursdependingonthenetworklinks,sotasksnotcompletedatmidnightarecarriedoverandshowuponthenextday'stodolist.
Thisschemeworkswellforhigh-leveltasksandsimpleprocessing,butforlow-level,complexprocessing(multi-stepprocessingofSeaWiFSdatafromlevel-1throughlevel-3forexample),theVDCismoresuitable.
WhenaleisqueuedforVDCprocessing,anewrecordisinsertedintooneoftheprocessingcontroldatabasetables(the''activeproc''table)whereitwaitsinlineuntilalloftheancillarydataneededforprocessinghavebeenidentiedandstaged.
Oncethisoccurs,theleisadmittedintotheVDCandpassedalongtoanyofthesystemresourcesavailableforproces-sing.
OneofthekeydesignfeaturesoftheSDPSisitsdistributedprocessingenvironmentwithsystemallocationofany/allavailableresourcesrangingfromamultiprocessorSGItodesktopLinuxmachines.
Thesystemisscalableinsizeandisabletotakeadvantageofresourcesasneeded.
Forinstance,manyofthedesktopmachinesusedbySPOstaffareavailableforprocessingwheneithertheloadonthemissufcientlyloworwhentheyhavebeenidleforapredeterminedamountoftime.
Asimpleentryinoneofthedatabasetablescanaddorremovetheseresourcesfromtheavailablepool.
TheVDCusestwoabstractconcepts:avirtualcomputerprocessingunit(CPU)andarecipe.
AvirtualCPUisaworkspacedenedonamachinethatcanbeusedbytheVDC.
Thisworkspaceisoneortwodirectories,denedasinputandoutputbuffers,whichwillcontainallofthelesneededandproducedbytheindividualstepsoftheprocessing.
TheworkspacesaredenedinthehostsandresourcestablesandareallocatedandfreedautomaticallybytheVDC.
Dependinguponthecapabilitiesofeachcomputerdenedasaresource,multiplevirtualCPUscanbeallocatedonanygivenmachine.
Currently,theSPOhasapproximately90virtualCPUstocallontomeetitsprocessingneeds,althoughtheactualnumberofcomputersissignicantlyless.
TherearethreebasicfunctionsassociatedwiththeVDC:En-trance,Master,andExit.
TheEntranceprogramistheentrypointintotheVDC,anditmonitorstheentrancedirectoryfornewdatatoprocess,allocatesthenecessaryresources,readsthejobcommandle,stagesthedataforprocessing,andcreatesastreamrecordthatsignalstheVDCtobeginautomaticprocessing.
TheMasterprogramis,inasense,themastercheffortheVDC.
ItmonitorstheStreamstableforstreamrecordsthatarereadytobeprocessed,marksthemasbusy,andinvokestheprocessingjobsaccordingtothestepsoftheassignedrecipe.
Essentially,itmovesajobfromonesteptothenextuntilitiscompleted.
TheExitprogramisthenalstageoftheVDC.
ItmonitorstheStreamstableforstreamrecordsthathavecompletedprocessing,de-allocatestheresourcemakingitavailableforanotherjob,recordsthecompletiontime,deletestheinputdatale,andmarksthestreamrecordreadyfordeletion.
Arecipeisaprocessingschemethatconsistsofasetofsteps,eachstepperformingaseparatetask.
TheVDCinvokesthestepssequentially,justasachefwouldfollowacookingrecipe.
Therecipesaredenedinthe''recipelookup''andrecipestables.
Becausetherecipestepsaredesignedtoperformassmallasetoffunctionsaspossible,onestepintherecipetablecanbeusedbyalargenumberofdifferentprocessingscenarios.
Onestep,CPYVDC,doesnothingbutcopyalloftheinputdatales,ancillaryles,andparameterlesintotheprocessingdirectoryandisusedbymanydifferentrecipes.
ARTICLEINPRESSC.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–42262.
3.
3.
SystemevolutionThedesigngoalof10(forglobalGAC)processingwasmetatlaunchand,throughacombinationofprocessorandnetworkspeedadvances,additionalprocessors(mostlydesktopsystems),andprocesscontrolsoftwarethatdyna-micallyutilizesallavailablecomputingresourceswithintheSPO,thesystemhasrealizedthefollowingthroughputimprovements:secondre-processing(August1998),40;thirdreprocessing(May2000),130;fourthreprocessing(May2002),400.
Recentsystembenchmarksshowa3000throughputwhichtranslatestoacompleteregenerationofallthestandardarchiveproductsfortheentiremissioninlessthan1day.
2.
4.
DatadistributionUnderthecontractwithORBIMAGE,onlyauthorizedSeaWiFSresearchersmayhaveaccesstothedigitalSeaWiFSdataforresearchandeducationalpurposes,andtheSPOisresponsibleforprovidingtheDAACwithalistoftheseauthorizedresearchers.
DuringtheearlypartoftheSeaWiFSmission,researcherswererequiredtosubmitawrittenproposaltotheSPOforreview,andiftheintendeduseofthedatafellwithintheagreeduponactivitiesoutlinedinthecontract,thenthatresearcherwasaddedtothelistandtheDAACwasnotied.
Recently,thisprocesshasbeenstreamlinedthroughtheprovisionofanonlinerequestformwherepotentialSeaWiFSdatauserscansubmitalltherequiredinformationelectronically,andwhereafterreviewandap-proval,acceptancemessagesarepassedtotheDAACandtotheresearcher.
Thisprocessisgenerallycompletedonthesamedaythatthesubmissionismade.
Whilemostrequestsaregenerallyapproved,submissionsfromcommercialinterestsarereferreddirectlytoORBIMAGE.
Sincelaunch,therehasbeenanalmostconstantrateofincreaseinthenumberofauthorizedusers,whichnowexceeds2300.
TheoriginalcontractwithOrbitalSciencesprovidedNASAwith13real-timelicensesthatalloweddecryptionasthedatawerereceived.
AsidefromtheSPO,licensesweredistributedtostationsinMississippi,California,Alaska,andHawaii.
Thesesitescoulddistributereal-timedataforvalidationcruisesupportwithSPOpermission.
Toassistinvalidationeffortsandcruiseplanning,theSeaWiFSandSIMBIOSProjectsjointlydevelopedareal-timeusersupportWebsite,whichallowedtheusercommunitytoobtainoverightpredictionsandreal-timedataproductsforcruisesupportanddemonstrationstudies.
Asaresult,real-timedataproductshavebeenprovidedtonearly400eldcampaigns.
BecausetheSeaWiFSmissionwasconsideredtobeanearlycomponentofEOS,theofcialdataarchiveanddistributionfunctionswererequiredtobehandledbytheEOSDISVersion0DAAClocatedatGSFC.
TheDAACservesasthelong-termarchiveanddistributionfacilityforallSeaWiFSdataoncethedatahaspassedthe14-dayembargoperiod,becausethereisagreatdealofvaluablesciencethatneedstobeconductedusingreal-timeornear-real-timedata.
Inresponse,theSPOdevelopedanextensiveWeb-basedsetofuser-friendlybrowse,order,andimageanddatadistributiontoolstoservicethesciencecommu-nity'sneedforaccesstothisdatapriortoitbeingarchivedattheDAAC.
Inatypicalmonth,SeaWiFSsends60–80gigabytesofcompresseddatatotheDAACandtheDAACdistributesapproximately500–600gigabytes(compressedvolume),oraboutninetimesthearchivedvolume.
Ackeretal.
(2002)provideacomprehensivereviewoftheDAAC'sSeaWiFSproductdistributionstatistics.
2.
5.
OutreachOutreachhasmanyforms,severalofwhicharementionedabove,e.
g.
,near-real-timesupportservices.
OtheractivitieshavebeenfocusedonsimplyadvertisingtheSeaWiFSprogramandtheapplicationsofthedata.
TheSPOhasworkedcloselywiththeGSFCOfceofPublicAffairstoprovidecoverageofnewsworthyeventstothenewsmedia.
Also,fortherst3yearsafterlaunch,theSPOputmuchemphasisonhavingapresenceatallmajorEarthscience-relatedconferences(USandinternational)byprovidingpresentationsoraninformationboothtofamiliarizedifferentsectorsofthepotentialusercommunitywiththeARTICLEINPRESSC.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4227mission.
Twooutreachactivitieshavebeenparti-cularlyimportant,SeaDASandtheSTRS,whicharedescribedindetailbelow.
SeaDAS:OneofthelessonslearnedfromtheCZCSexperiencewastheneedfortheusercommunitytohaveanaffordableandeasy-to-usedataprocessingcapabilitysothattheremotesensingdataproductscouldbetailoredtotheirresearchandapplications.
Also,havingahands-oncapabilityallowstheusertobecomemuchmorefamiliarwiththeprocessing,helpsconnecttheresearchcommunitytoremotesensingtech-nologyandmethodologies,andallowstheusertointegratealternativealgorithmsandanalysisrou-tinesintothesoftware.
SeaDAS(Fuetal.
,1998;Baithetal.
,2001)wasanoutgrowthoftheSEAPAKsystem(McClainetal.
,1991a,b,1992a)andwasdesignedtomeetthisneed,al-thoughitwasnotconsideredaprojectrequirementanddidnothaveanexplicitbudgetline.
Thisbeingthecase,itwasfundedthroughtheNASAOceanBiogeochemistryProgramwithassistance(systemadministrationandequipment)fromtheSeaWiFSandSIMBIOSProjects.
ThisfundingsupportedtheSeaDASstaff,whichhasneverexceededthreefull-timeindividuals(usuallyonlytwo).
SeaDASdevelopmentwasinitiatedearlyonintheprelaunchphasewiththerstusertrainingclassesbeingheldin1994.
SeaDASisnotmeanttobeacomprehensiveanalysissystem,butisdesignedprimarilytoreplicatealltheoperationalprocessingproceduresandproducts(level-0throughlevel-3;GACandLAC)whileallowingkeyprocessingparameterstobevariedastheuserndsappropriate.
Todothiseffectively,SeaDAShasemphasizedproductdisplayfunctionalityanddiagnosticanalysesforevaluatingtheproducts.
ThesysteminitiallysupportedSiliconGraphicsandSunMicrosystemUnixworkstationsandwaslateradaptedtorunonPC-basedLinuxsystems.
TheInteractiveDataLanguage(IDL)isusedfortheuserinterface,displayfunctions,mapprojec-tions,andbasicstatisticalanalyses,whichallowsthesoftwarepackagetobeeasilyexpandedbyuserswhowritetheirownIDLroutines.
Arun-timelicenseisprovidedwithSeaDASforthosewhodonotplantowriteIDLroutines.
SeaDASisdistributedintwoforms,compiledexecutablecodeandsourcecode.
OneimportantbenetfromtheearlyprelaunchreleaseoftheSeaDASsourcecodewasthatitenabledtheusercommunitytoexaminethecodeandprovidefeedbacktotheSPO,e.
g,codingerrors,andrevisedornewfeatures.
Havingtheprocessingowdocumentedbeforelaunch(Darzi,1998)madetheprocessofreviewingthecodemucheasier.
SeaDASalsosupportstheprocessingofCZCS,OCTS,OceanScanningMultispectralImager(OSMI),andModularOpto-electricScanner(MOS)data,thedisplayofallMODISoceansproducts,andthegenerationofSeaWiFSNDVIelds.
SeaDAShasbeendown-loadedtomorethan500uniqueusersitesinover45countriessincethefourthreprocessingandreceivedthe2003NASASoftwareoftheYearAward.
SeaWiFSTechnicalReportSeries:AlthoughtheCZCSmissionandtheCZCSglobalreprocessingeffort(Feldmanetal.
,1989)providedmuchoftheblueprintforsettinguptheorganizationandresponsibilitiesoftheSPO,mostofthisimportantandusefulinformationwasoutsidethesubjectmatterofpeer-reviewedpublicationsandwasnotavailableinacentralizedlocation,i.
e.
itwasscatteredamongsttheoriginalparticipatingin-dividuals,institutes,andcompanies.
Insomecases,solutionprocessestoimportantproblemswereneedlesslyrepeated,becausetherelevantmaterial,althoughknowntoexist,wasnolongeraccessible.
TheSTRSwascreatedearlyinthedevelopmentphaseoftheSPOtoensureallthescientic,technical,andmission-relatedaccomplishmentsandapproachesweredocumentedandavailablefromatleastonesource.
Italsoprovidedapublishingforumformembersoftheglobalocean-colorcommunitycollaboratingwiththeSPO.
TheSTRSplacedahighpriorityonqualityandconsistency,and,therefore,standardizeddocumentformatting,nomenclature,andsymbols.
Indexvolumeswereincludedatregularintervalstoincludelistingsofcitations,symbols,updates,andcorrections.
TheSTRSconsistsof43pre-launchand29postlaunchvolumes,andhasbeenroutinelydistributedtonearly500scientists,institutes,libraries,andmarineinformationcen-tersthroughouttheworld.
Inaddition,theARTICLEINPRESSC.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4228postlaunchseriesisavailabletothegeneralpublicworldwideasdownloadablelesfromtheSeaWiFSWebsite(theprelaunchreportsareintheprocessofbeingconvertedtodownloadableles).
Hardcopiesofanyorallofthepre-andpostlaunchseriesareavailableuponrequestfromtheSPOorthetechnicaleditor(ElaineFirestone).
2.
6.
SeaWiFSreprocessingsanddataqualityimprovementsDuringtherst5yearsofSeaWiFSoperations,theSPOconductedfourreprocessings.
ThesewereinitiatedattherequestoftheCVelementwithinputfromtheusercommunitywhenimprove-mentsinthealgorithms,elddata,orsensorcharacterizationweredemonstratedtohaveasignicanteffectondataquality.
Thereproces-singswereprecededbyextensiveanalysisandevaluationwhichwassharedwiththeusercom-munityforcommentthroughworkshopsandWebsitesbeforenalapprovalwasgiventoreprocess.
Inaddition,eachreprocessingrequiredconsider-ablecoordinationbetweentheSPOelements,especiallytheCVandDPelements,aswellaswiththeDAAC.
TherstreprocessingwasexecutedinJanuary1998,shortlyafterdataacceptance,andincorpo-ratedanumberofcodingerrorcorrectionsandmask/agadjustmentsbasedontheinitialevalua-tionsofthedataproducts.
ItalsoincludedtheinitialvicariouscalibrationbasedonMOBYobservations.
Thesecondreprocessingwasexe-cutedinAugust1998afteritwasdeterminedthatsignicantdegradationinthenear-infrared(NIR)bandswasoccurring.
Themostimportantim-provementassociatedwiththesecondreprocessingwastheuseofthemonthlylunarimagestoestimatethetimedependenceofthesensorsensitivity(Barnesetal.
,1999).
Thethirdrepro-cessingwascompletedinJune2000andwasinitiatedtoaddressthecontinuingproblemofnegativewater-leavingradiancesincoastalareas.
ThisproblemwasaddressedbyincludingaNIRreectanceadjustmentintheatmosphericcorrec-tionmodel(Siegeletal.
,2000).
Also,anewchlorophyll-aalgorithmthatsequencedthroughasetofthreeband-ratiorelationships,theso-calledOC4V4algorithm,wasadopted(O'Reillyetal.
,2000).
TheothermajormodicationinthethirdreprocessingwastheswitchtotheSPO'scode(calledMSL12)fromtheoriginalRSMASlevel-2processingcode.
Summariesofalltheimprove-mentsassociatedwiththesecondandthirdreprocessingsareinMcClainetal.
(2000b).
Finally,thefourthreprocessingwascompletedinJune2002(Pattetal.
,2003)andincorporatedarevisedvicariouscalibrationbasedonrecalibrateddatafromoneoftheMOBYsystems,whichaccountedforstraylightintheMOBYspectro-meter.
AsubsequentcalibrationofthesecondoperationalMOBYsystemshowedonlyaslightdifferencefromthevaluesderivedfortherstsystem.
Also,arevisedNIRcorrectionthatincorporatesthebackscatteringmodelofGouldetal.
(1999)wasadopted.
Theseimprovementsfurtherreducedtheoccurrenceofnegativewater-leavingradiancesinturbidandcoastalwaters.
Thequalityofthedataproductsisevaluatedprimarilyonthecomparisonswithinsitudata(Baileyetal.
,2000;Werdelletal.
,2003)andLWNstabilityanalyses(EpleeandMcClain,2000).
TheLWNandchlorophyll-amatch-upcomparisonsbetweenthesatelliteretrievalsandinsitudatafromthefourthreprocessingindicateexcellentagreementovertheentirerangeofvaluesforallparameters(Fig.
5).
Forexample,theslopeandr2fortheLWN(412)is0.
992and0.
82,respectively,forover200matchupsspanningarangefromabout0.
1tonearly3.
0mWcm2mm1sr1.
Thisisparticularlyimportantbecausetheatmosphericcorrectionatthiswavelengthrequiresthegreatestextrapolationfromtheinfraredwavelengthsusedtoselecttheaerosolmodel.
ItisalsothemostdifcultwavelengthintheSeaWiFSbandsettodetermineaccurateinsituinstrumentcalibrationsbecauseoftherelativelysmallstandardcalibrationlampoutput.
Withretrievalsofthisquality,the412nmbandcannowbeusedfornewapplicationsandalgorithms,(e.
g.
,Siegeletal.
,2003),especiallyincoastalwaters,e.
g.
,discriminatingviablechlorophyllfromdegradationproducts(theorigi-nalpurposeforthe412nmband).
Forchloro-phyll-a,theslopeandr2are1.
03and0.
85,respectively,for262matchupsoverarangeof0.
03toaround20mgm3.
AsademonstrationofARTICLEINPRESSC.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4229stability,Fig.
6showstheannualcyclesofaveragedeep-water(>1000m)LWNvaluesfor1998–2003.
Theplotsshowthatthe510and555nmLWNvaluesareconstantandthatthe412,443,and490nmLWNvalueshaveregularseasonalpatternswithlittlevariationfromyeartoyear.
ThisstabilityinthederivedproductsisbasedsolelyonthelunarcalibrationsandisindependentoftheEarth-viewingdata.
TheseresultsandothersareavailablefromthereprocessingWebsiteanddetaileddescriptionsofthereprocessingandtherelatedanalysesarebeingdocumentedintheSTRS.
Finally,assumingtheSeaWiFSdatabuyendsinDecember2003,theSPOwillconductanalreprocessinginearly2004.
Asbefore,theSPOwillsolicittheusercommunity'sinputonalgorithmandproductimprovements,includingadditionalproductstobeaddedtothearchiveproductsuite.
3.
MajorgeophysicaleventscapturedbySeaWiFSDuringtherst5yearsofglobalobservations,agreatmanygeophysicaleventshavebeencapturedintheSeaWiFSdataset.
Theserangefromlocaleventssuchasanomalousphytoplanktonblooms(FloridaBay;thesouthwestFloridaDarkWaterObservationGroup,2002),volcaniceruptions(Mt.
Etna),wildres(westernUnitedStatesandARTICLEINPRESSFig.
5.
ComparisonsofinsituandsatelliteLWNandchlorophyll-avalues,i.
e.
,match-upcomparisons,afterthefourthreprocessing.
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4230ARTICLEINPRESSFig.
6.
Comparisonofannualcyclesofglobal8-daymeanLWNvaluesfordepthsgreaterthan1000mduringtheyears1998–2003.
Fig.
7.
Globalbiosphereseasonalcycle.
BecauseSeaWiFSGACdatacollectionincludesallsunlitportionsoftheorbit,includinglandmasses,itispossibletoderiveNDVIandotherterrestrialproductsfromSeaWiFS.
Forexample,Behrenfeldetal.
(2001)generatedglobaltimeseriesofmarineandterrestrialprimaryproductivityusingSeaWiFSdatashowingthatovertherst3yearsofdata,oceanproductivityincreasedinthepost-ElNinoocean,whileterrestrialproductivityremainedconstant.
Thisfour-panelgureshowsthe5-yearseasonalclimatologiesofoceanchlorophyll-aandterrestrialNDVI.
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4231CentralAmerica),andoods(USmid-AtlanticcoastafterHurricaneFloyd),toglobalphenom-enasuchasthe1997–1998ElNino-LaNina.
SeaWiFSdataalsoarebeingusedforfreshwaterstudies,e.
g.
,theGreatLakes(Leshtetal.
,2002).
Datafromthemissionhavebeenusedfrequentlybythenewsmedia,notonlybecauseofitseaseofaccessandrapidturnaround,butalsobecausetheSPOandtheGSFCPublicAffairsstaffmadeitahighprioritytoprovideinformationonnews-worthyevents.
Inthissection,animagegallerywithbriefdescriptions(captions)ofsomeoftheeventsofparticularinteresttothescienticcommunityareprovided.
Fig.
7showsthefourseasonalclimatologiesofoceanchlorophyll-aandNDVI.
Figs.
8–12aresequencedfromlocaltobasinscaleevents(seegurecaptionsfordescrip-tions).
FalsecolorimagesarecomposedofRayleighcorrectedcompositesofthe412,555,and670nmSeaWiFSbands.
4.
SummarySeaWiFSwastobetherstinacontinuousseriesofinternationalglobalocean-colormissionswhichwouldprovideahighqualityclimateresearchqualitytimeseriesofmarinebiologicalandopticalproperties.
Becauseofthelaunchslip,OCTSwastherstandprovided9monthsofglobalcoverage.
Fortunately,theSeaWiFSdatacollectionbeganshortlyaftertheendoftheOCTSdatarecordleavingonlya3-monthgap.
WhileSeaWiFSwasnotlaunchedearlyenoughtosupportmuchoftheJGOFSprogram,whichwasaprimaryrationaleforthemission,the4-yeardelaydidallowtheSPOtobuildmuchmorecomprehensivecapabilitieswithineachSPOele-ment,whichultimatelyallowedtheSPOtomeetitsprimarygoalsandobjectivesearlyintheprogram.
Additionally,becauseofitsbilineargaindesignandaccuratecalibration,SeaWiFShasproventobeanoutstandingtoolforterrestrialecologyandaerosolresearch.
SeaWiFSdidpre-cedetherstMODISinstrumentontheTerraplatformby2.
5yearsandthesecondontheAquaplatformbynearly5years,andwasinvaluableforMODISprelaunchpreparationsandpostlaunchvalidation.
SeaWiFSalsohasservedasimilarpurposeforanumberofotherocean-colormissionsincludingtheEuropeanMediumResolu-tionImagingSpectrometer(MERIS)andtheJapaneseGlobalImager(GLI).
Table4sum-marizessomeofthemostsignicantaccomplish-mentsoftheSeaWiFSprogramandunderscoresthepointthattheprogramhasachieved,evensurpassedinmostcases,itsoriginalobjectivesandgoals.
WithsupportfromtheSIMBIOSandMODISprograms,theSeaWiFSCVelementhasunder-takenaverycomprehensiveandcoordinatedeffort,thecomponentsofwhichmustbeconti-nuedinsometo-be-determinedmannerifprojectsliketheNPP/VisibleandInfraredImagingRadio-meterSuite(VIIRS)aretoprovideclimateARTICLEINPRESSFig.
8.
BeringSeacoccolithophoreblooms.
Duringthesummerandfallof1997,alargecoccolithophorebloompersistedintheeasternBeringSea(Vanceetal.
,1998).
SuchbloomsareveryunusualintheBeringSeaandcausedwidespreadstarvationofmarinebirdsandmammalsandalsoseverelyaffectedsherieswhichusetheadjacentAlaskanriversforspawning.
Thebloomreappearedthefollowingspringandwasvividlycapturedinthis25April1998SeaWiFSimage.
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4232research-qualitydataconsistentwithprecedingdatasetsfromSeaWiFSandMODIS.
Also,inthefuture,moreemphasiswillbeplacedonprovidingbroaderandmoreaccuratesuitesofproductsfromocean-colormissionsforcarboncycleresearchandcoastalzonemanagement,e.
g.
,primaryproduc-tivity,particulateorganiccarbon(POC),CDOM,calcite,andtotalsuspendedmatter(TSM).
Thesewillrequireneworimprovedalgorithmsand,insomecases,moreaccurateatmosphericcorrec-tions,especiallyoverturbidwaterandinareaswithabsorbingaerosols.
Moreaccuratemeasure-ments,especiallyinturbidwaters,willbeneces-sary.
Inaddition,someproductsalsomayrequirefuturemissionstomakeobservationsfurtherintotheultravioletwhereinstrumentcalibrationismorechallenging.
Thus,itiscriticalthatactivitiessuchasSeaBASS,thecalibrationroundrobin,theprotocoldevelopment,andtheinstrumentevalua-tionsanddevelopmentactivitiesbecontinuedaftertheSeaWiFSandSIMBIOSProjectsend.
Finally,theSeaWiFSmissionhasdemonstratedthatadata-buyapproachtoobtainingasciencequalitydatasetcansucceed,althoughsuccessdoesrequireadeterminationbyboththegovernmentandthecommercialpartnerstodeliverontheirrespectiveobligationsnomatterhowdifcultandcostlythetasksmaybe.
Successalsorequiresacommitmenttoworkopenlyandmaintaincom-municationsnomatterhowstressfulthecircum-stancesmaybe.
Clearly,thenumeroustechnicalproblemspriortolaunchandthenancialburdenonbothpartieswerechallengingtobearandbothpartieshadopportunitiestoterminatethemission.
Intheend,theresolvewasthere,solutionswerefound,SeaWiFSwaslaunched,andthecompletedatasetwasdelivered.
ThisachievementwasrecentlyacknowledgedwhentheSPOandOSCjointlyreceivedtheprestigiousPecoraAward,ajointawardfromNASAandtheDepartmentofInterior,forthemission'scontributionstoEarthscience.
AcknowledgementsTheauthorsacknowledgeanumberofindi-viduals,groups,andorganizationsfortheirARTICLEINPRESSFig.
9.
AsianandSaharandustevents.
BecauseonthebilineargaindesignofSeaWiFS,thesensordoesnotsaturateinanyofthebandsevenoverthebrightesttargets.
ThegureincludesexamplesofdusteventsoffNWAfrica(Saharandust)andoverAsia(Gobidust).
SaharandusthasbeentrackedusingSeaWiFSdataasfartothenorthwestasNewEngland.
Similarly,AsiandusteventshavebeentrackedacrossthePacictotheUSwestcoast(Husaretal.
,2001).
Thedetectionoflowlevelsofdustintheimagerycontinuestobeproblematicasitescapesthedustandcloudmasksresultinginarticiallyelevatedchlorophyllconcentrations.
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4233contributionstotheSeaWiFSprogram.
OSC,SantaBarbaraResearchCenter,andORB-IMAGEdeservespecialrecognitionforbuilding,launching,andmaintainingaspacecraftandinstrumentthathasworkedexceptionallywell.
SeveraldifferentGSFCengineeringgroupspro-videdcriticalassistancetoOSCindiagnosingproblemswiththespacecraft,launchvehicle,andinstrumentpriortolaunch.
Duringtheprelaunchphase,NASAHQseniormanagers,particularlyBillTownsend,DixonButler,andStanSnyder,weresteadfastintheirsupport.
Throughouttheprocessofgettingthemissionapprovedandlaunched,severalOceanBiogeochemistryProgramManagershaveassistedandrepresentedtheSPOatNASAHQ(MarlonLewis,GregMitchell,RobertFrouin,JimYoder,JanetCampbell,JohnMarra,ChuckTrees,andPaulaBontempi).
ScienceApplicationsInternationalCorporation(SAIC)anditssubcontractors(ScienceSystemsARTICLEINPRESSFig.
10.
2002NorthAtlanticspringbloom.
EarlyresultsfromtheCZCSglobalreprocessinghighlightedtheextentandmagnitudeofthespringbloom(Esaiasetal.
,1986;McClainetal.
,1990)andthebloomwasthesubjectoftherstJGOFSeldstudy.
OfthespringbloomsobservedbySeaWiFS,the2002bloomwasparticularlyintense.
Thissequenceofmonthlymeanchlorophyllcompositesillustratesthenorthwardmigrationofthe''greenwave,''azonalbandofhighbiologicalproductionthatresultsassolarilluminationincreasesoverthecourseofspringandsummerathigherlatitudes.
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4234andApplications,Inc.
,andFuturetechCorpora-tion)haveprovidedatalentedanddedicatedsupportstafffromthebeginningoftheSPO.
TheGSFCPublicAffairsOfce,particularlyWadeSisler,hasworkedvigilantlywiththeSPOtoquicklygetdataproductstothenewsmediaduringspecialgeophysicalevents.
Similarly,theGSFCVisualizationLaboratoryhasprovidedmanyexcellentvideosequencesforpressconfer-encesandspecialpresentations.
TheCVelementhasworkedcloselywithanumberofinternationalprograms,suchastheAMT,underLOAswithPlymouthMarineLaboratoryintheUnitedKing-dom(JimAiken,P.
I.
),theJointResearchCenterinIspra,Italy(GiuseppeZibordi,P.
I.
),andtheLaboratoired'Oc!
eanographiedeVillefrancheinVillefranche-sur-Mer,France(Herv!
eClaustre,DavidAntoine,andAndr!
eMorel,co-investiga-tors).
TheSPOisindebtedtoseveralmembersoftheMODISoceansteamwhohavemadeavarietyofmajorcontributionstotheSPOincludingWayneEsaias,DennisClark,BobEvans,HowardGordon,andKenCarder.
TheSPO'scollabora-tionswithNIST,mainlyCarolJohnson,hasbeeninvaluabletothecalibrationofnotonlytheSeaWiFSsensor,butalsoinsitudata.
WatsonGreggdeservesspecialrecognition,astheMissionOperationselementleaderfromthebeginningoftheSPOthroughdataacceptance.
Fourindivi-dualshaveservedasSPOManagers:BobKirkoversawtheearlyphasesoftheSPOthroughtheacceptanceoftheSeaWiFSinstrument;MaryCleaveguidedtheSPOthroughmuchofthespacecraftacceptanceandlaunch;ChuckMcClainARTICLEINPRESSFig.
11.
1997–1998ElNino-LaNina.
ThemostnoteworthyeventtodateduringtheSeaWiFSmissionwasthe1997–1998ElNino-LaNina,whichwasthemostintenseonrecord(McPhaden,1999).
TheequatorialPacicecosystemstransitionedfromextremelylowchlorophyllconcentrationsoverthewinterof1997–1998tothehighestconcentrationseverrecordedduringthesummerof1998(Chavezetal.
,1999;Murtuguddeetal.
,1999).
TheseextremesareillustratedintheJanuaryandJuly1998monthlycomposites.
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4235directedtheSPOthroughdataacceptanceandtherstthreereprocessings;andGeneFeldmanhasguidedtheSPOduringthefourthreprocessingandthenegotiationsfortheextendedSeaWiFSmis-sion.
Finally,theocean-colorresearchcommunityhasprovidedunwaveringsupportandassistanceARTICLEINPRESSFig.
12.
The1998LaNinaequatorialPacicbloomtimeseries.
WhiletheJuly1998monthlychlorophyllcompositeindicatesthearealextentofthebloomoveramonth'stime,thebloomwasactuallymovingeastwardrapidlyandwasmuchsmallerinsize(Struttonetal.
,2001).
Thisgureshowsfour8-daycompositesofSeaWiFSchlorophyllandthecorrespondingcompositesofseasurfacetemperature(SST)illustratingthehighcoherencebetweenthetwoeldsandthewavestructureassociatedwiththebloom.
C.
R.
McClainetal.
/Deep-SeaResearchII51(2004)5–4236totheSPOthroughouttheSeaWiFSprogramwhichhasbeenagreatencouragement.
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ARTICLEINPRESSTable4SummaryofmajorSeaWiFSprogramaccomplishments1.
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