ngac landsat future missions recommendations paper · ngac landsat future missions recommendations...

RECOMMENDATIONS FOR POSSIBLE FUTURE U.S. GLOBAL LAND DATA

COLLECTION MISSIONS BEYOND LANDSAT 9

AReportoftheNationalGeospatialAdvisoryCommitteeLandsatAdvisoryGroup

April2018

NGACLandsatFutureMissionsRecommendationsPaper April2018

NationalGeospatialAdvisoryCommittee(www.fgdc.gov/ngac) 1

RECOMMENDATIONSFORPOSSIBLEFUTUREU.S.GLOBALLANDDATACOLLECTIONMISSIONSBEYONDLANDSAT9 ExecutiveSummaryInAugustof2017,theU.S.GeologicalSurvey(USGS)requestedthattheLandsatAdvisoryGroup(LAG),asubcommitteeoftheNationalGeospatialAdvisoryCommittee,providerecommendationsinregardstopossiblefutureU.S.GlobalLanddatacollectionmissionsbeyondLandsat9,whichiscurrentlyplannedforalaunchinlate2020.TheUSGSaskedthattherecommendationsbesubmittedintimetosupportasignificantU.S.Governmentarchitecturereviewprocessanticipatedtostartinmid-2018,andthattherecommendationsconsider:

1. Capabilitiesthatarecomplementarytotheexpectedcapabilitiesofthecommercialremotesensingindustry,aswellastheEuropeanUnion’sCopernicusProgram,includingdiscussionofutilityandlimitationsforleveragingcubesatandsmallsattechnology,

2. TechnicalfeasibilityandapplicationvalueofenhancedcollectioncapabilitieswhilemaintainingcontinuitywithhistoricandcurrentLandsatsystemcapabilitiesandapplications,and

3. Opportunitiesforpublic--privatepartnerships(P3).

ThefollowingtextsummarizestheLandsatAdvisoryGroup’sfindingsandrecommendationsregardingthesetasks.Thefindingsandrecommendationsarenumberedaccordingtotherelevanttask(1-3above).Findings

1.a.Noneofthecurrentsmallsatorcubesatsatellitesystemsdeployedtodatehavethetechnicalcapabilitiesrequiredbythethousandsofresearchers,governmentagencies,NGOs,andcommercialcompanieswhorelyonLandsatcontinuityforresearchandoperationaldecisionmaking.WhilethesmallsatsandcubesatsmayexceedLandsatcapabilitiesinspatialresolutionand/orrevisittime,noneofthesesatellitescurrentlyhavesensorswiththeneededspectralbands,calibrationstability,orswatharearequiredbytensofthousandsofU.S.Landsatusers.

1b.Commercialsystemstodatehavetargetedahigherspatial/temporalresolutionmarketnichewhichisnotservedbygovernmentsystemswithfreeandopendatapoliciessuchasLandsat,Sentinel-2,GOES,orMODIS.

1c.UnlikeSentinelandLandsat,noneofthecommercialprovidersofferimageryworldwidewithoutuserestrictionsandatnocost,animportantconsiderationforresearchersandagenciesrelyingonLandsatandSentineltosupportoperationaldecisions.

1d.LandsatandtheCopernicusProgram’sSentinel-2multispectralbandsareverysimilarandcanbeusedincombinationwithoneanother.However,onlyLandsatprovidesmoderateresolutionthermalimagingcapabilities.

2a.PossibilitiesforenhancedcapabilitiesforfutureLandsatMissionswhilemaintainingcontinuityincludemaintainingcurrentLandsatcapabilitiesatlowercostbyleveragingemergingtechnologies,adoptingtheCopernicusacquisitionmodelforcostsavings,increasingtemporalandspatialresolutions,andimprovingLandsatspectralresolution.



3a.Public-privatepartnershipsaresuccessfulonlywhenthereisanon-governmentrequiredproductwithsufficientdemandtogeneratesignificantcommercialrevenuefortheprivatepartner,andthepublicpartneragreestonotmakethatproductfreelyavailable.

Recommendations

2a.TheU.S.GovernmentshouldaggressivelyinvestigaterapidlyemergingandincreasinglyproventechnologieswhichcouldgreatlyreducethecostofLandsatmissions.IncludedinthisinvestigationshouldbeconsiderationofsmallersatelliteswithLandsat8/9OperationalLandImager(OLI)-likeperformancealongwithfreeflyerthermalmissionstomaintaincontinuityinLandsatthermalmeasurements.Asatest,itisrecommendedthattheU.S.GovernmentconsiderplacingathermalsensoronadedicatedfreeflyercompanionsatellitetooneoftheexistingSentinel-2systems.Additionally,itisrecommendedthatastudybeundertakentodetermineifadditionalClouds,Aerosols,Vapors,Ice,andSnow(CAVIS)bandsorinputfromasuitableauxiliarylowerresolutionsatellite,couldbeusedtoreducecostsassociatedwithsensorsforradiometriccalibration.

2b.ToomanycriticalU.S.researchandoperationalprogramsrelyonU.S.leadershipinmoderateresolutionearthobservationsfortheU.S.tocedeitsleadershipinmoderateresolutionearthobservationstotheEuropeanUnion’sCopernicusProgram.MaintainingU.S.homeland,food,andenvironmentalsecurityarealldependentupontheLandsatprogram.However,theU.S.shouldcontinuetoworkcloselywiththeEuropeanUniontobetterharmonizetheLandsatandSentineldatasets,obtaineconomiesofscalewherepossibleandsharelessonslearned.TheCopernicusapproachofbuildingmultiplesatelliteconstellationsatonceandlaunchingthemovertimeshouldespeciallybeinvestigatedtoreducedevelopmentandacquisitioncostspersatellite.

2c.RegardingthecapabilitiesofLandsat10,itisrecommendedthat:

• TheLandsat10groundsampledistancebesetto10metersorlarger,soastoincreasecompatibilitywithSentinelsensors,ensurewiderswathwidths,increasecoverage,andreduceoverlapwithcommercialproviders.

• TheU.S.GovernmentshouldinvestigatethebenefitsandcostsofincreasingLandsatspectralresolution.

• FromthestandpointofcontinuitywithpreviousLandsatmissionsforchangemonitoringapplications,wideswathscanningsensorsareprobablypreferableinthattheyoffergreatersynopticity(simultaneouscollectionoflargeareas).

3a.TheU.S.Governmentshouldconductamarketstudytodetermineifsufficientdemandexiststosupportexplorationofthecreationofapublic-privatepartnershipwherethecontractorprovidestwoormoretiersofdata-onemeetingU.S.GovernmentLandsattechnicalrequirementsforopenandfreedistribution,andothersthatprovide“superior”datawhichissoldtousers,therebycreatingasufficientrevenuestreamtooffsetatleastsomeofthecostsofbuildingandoperatingthesystem.Ifthismodelispursued,theGovernmentmustensurethatthereisanequitablebalanceofriskbetweentheGovernmentanditsprivatesectorpartner.



Introduction

Formostofitslong45yearhistory1theLandsatdatahasbeenuniqueinprovidingfreeorlowcostmoderateresolution(10m-100m)multispectralimagerywithregular16dayglobalcoverage.USGS’sdecisionin2008tomakeLandsatdatafreelyavailabletothepublichassetglobalexpectationsfortheavailabilityoffreehigh-qualityimagery,andsparkedawaveofcommercialactivitybasedonthisopportunity.Providinganestimated$1.79billiondollars/yearofvaluetoU.S.governmental,commercial,academic,andnon-governmentalorganizations(Milleretal,2012),Landsathascontinuallybeen“thegoldstandardofremotesensingfromspace”(Castle,2012).CommercialU.S.satelliteimageanalysiscompaniesOrbitalInsight,DescartesLabs,SpaceKnow,GDACorporation,Esri,andU.S.commercialsatellitecompaniesDigitalGlobe(nowpartofMaxarTechnologies),Planet,AstroDigital,BlackSkyandothersallprovideLandsatimagerythroughtheirplatformsandoffervariouslevelsofvalue-addedproductsbasedontheLandsatpublicimagery.ThesuccessoftheLandsatprogramhasalsoinspiredsimilarnon-U.S.satellitesystems,primarilytheEuropeanSpaceAgency(ESA)CopernicusProgramSentinel-2satelliteconstellation,andanewgenerationofcommercialsatelliteconstellationsliketheRapidEyesmall-sat,SkyBoxsmall-satandDovecube-satconstellations(alldevelopedoracquiredbyPlanet),thatprovidehigherspatialresolutionandbettertemporalcoveragethanLandsat,thoughwithreducedspatialcoverageperimageandreducedspectralcapability.AnyfutureLandsatcapabilitiesmustbeconsideredwithinthisdynamicandcomplexmarket.InAugustof2017,theUSGSrequestedthattheLandsatAdvisoryGroup(LAG),asubcommitteeoftheNationalGeospatialAdvisoryCommittee,providerecommendationsinregardstopossiblefutureU.S.globallanddatacollectionmissionsbeyondLandsat9,whichiscurrentlyplannedforalaunchinlate2020.TheUSGSaskedthattherecommendationsbesubmittedintimetosupportasignificantU.S.Governmentarchitecturereviewprocessanticipatedtostartinmid-2018,andthattherecommendationsconsider:

• Capabilitiesthatarecomplementarytotheexpectedcapabilitiesofthecommercialremotesensingindustry,aswellastheEuropeanUnion’sCopernicusProgram2,includingdiscussionofutilityandlimitationsforleveragingcubesatandsmallsattechnology,

• TechnicalfeasibilityandapplicationvalueofenhancedcollectioncapabilitieswhilemaintainingcontinuitywithhistoricandcurrentLandsatsystemcapabilitiesandapplications,and

• Opportunitiesforpublic--privatepartnerships(P3).ThisreportfirstreviewscurrentLandsatcapabilitieswithinthecontextofexistinggovernmentandcommerciallyoperatedsatellites.ItnextdiscussespotentialfutureLandsatcapabilitiesgivenexpectedadvancesintechnologyandaneedtomaintaindatacontinuitywithpastandcurrentLandsatmissiondata.Thethirdsectionofthereportsummarizesdifferentmodelsforpublic-privatepartnershipsthatcouldpotentiallybeusedinfutureLandsatmissions.

1From1985to1992theU.S.governmentexperimentedwithcommercializingLandsatdata.Duringthisperiod,Landsatimagerywasexpensive($4400/scene)andusewaslicenserestricted.2Pleaseseehttp://ec.europa.eu/growth/sectors/space/copernicus/forindepthinformationregardingtheCopernicusProgram.



CurrentCapabilitiesRemotesensingsystemcapabilitiesaretypicallycategorizedbytechnicalcharacteristicssuchasareacoverage,spatialaccuracy,andspatial,spectral,andtemporalresolutions,aswellasorganizationalcharacteristicssuchaspricingandlicensing.ThissectionofthereportcomparescurrentLandsatcapabilitiestothoseofthespacebasedcommercialremotesensingindustry,aswellastheEuropeanUnion’sCopernicusProgramSentinel-2satellites.ItincludesadiscussionofutilityandlimitationsforleveragingcubesatandsmallsattechnologytomeetLandsatuserrequirements.Pleaseseehttp://learngis.maps.arcgis.com/apps/MapSeries/index.html?appid=f01fba8fa601497092a183d1a31788f7&entry=5foracomparisonofthesesystemstooneanother.Approximatecoststobuildandlaunchthesesystemsrangefrom$855millionforaLandsattypesatellite,$500-800millionforWorldviewsatellites,$250-300millionforaSentinel2satellite,severalmilliondollarseachforRapidEyeandSkyboxsmallsats,andlessthanamilliondollarsforaPlanetDovecubesat.AreaCoverageTherearetwosystem-levelapproachestocollectinglargeareas.Onecanemploywideswathscanningsensorsonarelativelysmallnumberofspacecrafttoachievesynopticcoverage,asisdoneinLandsatandSentinel-2.Whiletheseneedn’tbenearlyascostlyasLandsat8(giventhedecliningcostofsensorsandelectronics),theydotendtobemoreexpensiveonaper-satellitebasisthanthealternative,whichistoemployalargernumberofstaringarraysacrossaconstellation,similartoPlanet’sconstellation.Itisnotaforegoneconclusionwhichapproachismorecosteffectiveandbothshouldbeconsidered.However,fromthestandpointofcontinuitywithpreviousLandsatmissionsforchangemonitoringapplications,wideswathscanningsensorsareprobablypreferableinthattheyoffergreatersynopticity(simultaneouscollectionoflargeareas).SpatialResolutionSpatialresolutionisthesmallestspatialunitonthegroundthatthesensoriscapableofimagingwhichisusuallyexpressedasthelengthonthegroundofonesideofapixeltermedthesystem’sgroundsampledistance(GSD).Forthesamesizedsensor,highresolutionisinverselyproportionaltotheareacoverage,sohighresolutionstypicallyresultinsmallercoverage.SincethelaunchofLandsat4in1982,thespatialresolutionofLandsat’snon-thermalmultispectralsensorshasbeenmaintainedat30meters.Sentinel-2’smultispectralspatialresolutionsare10metersforRed,Green,Blue,andInfraredbandsand20or60metersfortheotherspectralbands.Conversely,commercialhighresolutionsystemshavemuchhigherspatialresolutions,withthehighestprovidedbyDigitalGlobe’sWorldview3and4satellitesat31centimeters.TemporalResolutionTemporalresolutionisexpressedintwoways:

1. Thetimeittakestocollecteverywhere,whichisthefrequencyofglobalrefresh,(orhowoftentheentireplanetisre-collected),or

2. Howoftenagivensiteanywherecanberevisited,whichisthefrequencyofrevisit.

Refreshandrevisitaredependentuponorbit,swathwidth,satellitepointabilityandconstellation.Bothshouldberepresentedbecauseeachisrelevanttodifferentusecases.BecauseLandsat



systemshavelimitedpointability,theirrefreshandrevisitarethesame–16daysforeachsatellitewhichtranslatesto8daysforthecombinedconstellationofLandsats7and8.AddingtheSentinel-2non-pointablesystemsresultsinarefreshandrevisitofevery3daysto5days.Alternatively,Planet’sDoveconstellationrefreshisdailywhileDigitalGlobe’sconstellationiseveryfewweeks.Ontherevisitmetric,Planet’snon-pointableconstellationisstilldaily,whileDigitalGlobe’sconstellationcanachieve~5revisits/daybecausethesatellitesarepointable.Figure1comparesLandsatandSentinel’sspatialandrevisittemporalresolutionswiththatofexamplecommercialsystems,Sentinel-2,otherlowerspatialresolutiongovernmentsystemssuchasNOAA’sGOESweathersatellites,andNASA’sMODIS.Thechartillustratesthatcommercialsystemstodatehavetargetedahigherspatial/temporalresolutionmarketnichewhichisnotservedbygovernmentsystemswithfreeandopendatapoliciessuchasLandsat,Sentinel-2,GOES,orMODIS.

Figure1.ComparisonofspatialandrevisittemporalresolutionofseveralEarthobservingsatellites.(Source:LandsatAdvisoryGroup) SpectralResolutionSpectralresolutionisdrivenbythefocalplaneofasensor,andsensorcalibration.Sensorfocalplanescanvaryconsiderablyincomplexity.Figures2and3comparethelocationandwidthofbandsofLandsats7,8,and9tothoseoftherecentlylaunchedEuropeanSentinel-2andmostoftheexistingandproposedsmallsatsandcubesats.Landsatisdistinguishedfromthecommercialsmallsatsandcubesatsbyitsinclusionofshortwaveinfrared(SWIR)3andthermalinfraredspectral

3ThoughDigitalGlobedoesincludeeight3.7meterresolutionSWIRbandsonitsWorldView-3satellite.



bandswhicharecriticalforapplicationssuchasvegetationidentification,cropandwaterusemonitoring,andforestmanagement.Mostofthenewsmallandcubesatellitescaptureimageryinonly1-4spectralbandsversesLandsat’s11bandsandSentinel-2’s12bands.Specifically,thesmallsatsandcubesatsonorbittodayareincapableofsensingenergyinthemiddleinfraredandthermalbands.Alternatively,theSentinel-2constellation’sspectralbandswerepurposelydesignedtobesimilartoLandsatbandssothatdatafromthesystemscanbesynergisticallycombined.Sentinel-2providesadditionalspectralcoveragecomparedtoLandsat,e.g.,inthe“rededge”betweenvisibleandnearinfrared(previouslyonlyavailableviatheRapidEyeconstellation,nowapartofPlanet’sconstellation).However,Sentinel-2doesnotprovideacapabilityforthermalinfraredimaging.

Figure2.ComparisonofthespectralandspatialresolutionsofLandsat7and8imageryversusthoseoftheSentinel-2constellation,andexistingandproposed,cubesatsandsmallsats.(Source:USGS)Thesignaltonoiseratio(SNR)oftheimageryisalsoimportanttoensuresuitableaccuracyinspectralmeasurements,especiallyinareasthataredark,suchasshadowsidesofmountainsandincloudshadow.BothLandsatandSentinel-2withtheirlargeopticsandaperturescancapturesufficientlighttoachievehighSNR.ImprovementsinsensorsensitivityenablethesmalleropticsthatfitintosmallsatstoachievesuitableSNRvaluessolongasthespatialresolutioniskeptlargerthan~10meters.AchievingsuitableSNRfromtheopticsofcubesatsisdoubtful,thoughthisisquiteachievablewithlargerclassesofsmallsats.Whilethenumberandwidthofspectralbandsisimportant,withoutradiometriccalibrationofthedatasensedinthosebands,satelliteimagesarelittlemorethanprettypictures.Formanyapplications(e.g.,landcovermapping,agriculturalanalysis,ormonitoringanyformofchangeinstateovertime)



radiometriccalibrationofthesensorsiscriticallyimportantandneededtosupportrobustspectralandtemporalanalysis.Properradiometriccalibrationenablesonetoderiveconclusionsfromsatelliteobservationswithconfidence,byavoidingthemanyfactorsthatcanintroducenoiseoruncertainty.CalibrationofLandsatandSentinelimageryisrigorouslyperformedandbackedupbyUSGSandESAscienceprograms.DigitalGlobealsohasarigorouscalibrationprogramandregularlyreportstheircalibrationmethodsandresultsatscientificconferences.However,manyoftheexistingandplannedcommercialsmallsatsandcubesatsdonothaverobustcalibrationprogramsandactuallyrelyonLandsatandSentinel-2imageryforcalibration,requiringsubstantialpost-collectionspectralcollaboration.ScientificgradeconcurrentobservationsfromLandsat8andSentinel-2arecurrentlynecessarytoextractfullvaluefromsmallandcubesatcommercialobservations.Intheory,thereisnothingpreventingafuturesmallsatfromincorporatingscientificgradecalibration,thoughthiscanbeacostdriver;evaluationoffutureLandsatdesignapproachesshouldconsiderthisalongwithitsassociatedcostsinthetradespace.Radiometriccalibrationofthesensorsisalsodependentonbeingabletoregularlycomparesensormeasurementsagainstacalibratedsource.Thiscanbeachievedbyusingonboardlampcalibration,whichincreasesthenumberofmovingpartsandcomplexityofthespacesystemorbyundertakingappropriatesatellitemaneuversthatenablethesatellitetoscancooperativegroundtargetsorobjectsofknownreflectancesuchasthemoonandstars.Asthesecrosscalibrationtechniqueshavebeenrefinedovertheyearsitmaynotbenecessaryforadvancedonboardlampcalibration,whichwouldhelpreducecosts.Aerosolsandwatervaporintheatmospherehavepotentiallythelargestimpactonthelightbeingobservedbyasatellite.Theyabsorbdifferentpartsoftheincomingsunlight,andagainabsorbportionsofthelightreflectedbackintospace.Removingtheseeffectsisknownasatmosphericcompensation.Themostaccurateapproachistomeasuretheseatmosphericcomponentsdirectlybyincorporatingtheappropriatespectralbandsinthesensor(albeitthesecanbeatlowerspatialresolutionthantheprimarysensorbands).ThisistheapproachtakenonDigitalGlobe’sWorldView-3satellite,whichincorporatesan11-band“Clouds,Aerosols,Vapors,Ice,andSnow”(CAVIS)sensortomaketheseatmosphericmeasurements.However,aslongasthemainsensorincludesred,green,blueandnear-IRbandswhoseabsolutespectralresponseiswellcalibrated,techniquesexisttoestimatetheatmosphericeffectswithreasonableaccuracy.Lowerresolutioncoastalaerosolandcirrusbandsalsoprovidesignificantvaluetodetermineatmosphericeffectsandtheexistenceofhigh-altitudeclouds.SpatialAccuracyForimagerytobeusefulinmappingapplications,itmustberegisteredtotheground.Landsat,SentinelandDigitalGlobesystemsallincludestarsensorsandgyroscopeswhichallowforprecisemeasurementsofthesatellitelocationandorientation.Conversely,smallsatsandcubesatstendtohavepoorintrinsicgeometricaccuracy(ontheorderof100meters)becausetheytypicallycannotaffordthecosttoincludehigheraccuracystarsensorsorgyros.Thiscanbecompensatedbyregisteringcubeandsmallsatimagerytoasuitablyaccuratelayer,solongastheimagehasenoughnon-cloudypixelsoverland.Suchglobalaccuratebaselayersnowexistandthisregistrationprocesscanbeautomated,especiallyforwiderswathwidths.Theresultingaccuracywilldependonsensorviewingangle,digitalelevationmodelaccuracyandsensorstability.Forprimarilynadir-pointingsensors,thefirsttwowillhavelimitedimpact.Aslongasthegroundpixelsizeofthesensorisgreaterthan10meters,thegeometricstabilityofthesensorisalsolikelytohavelittleeffect,sooverallaccuraciesof~10metersshouldbeachievablewithoutincludingthemoreadvancedstarsensorsandgyroscopes.



PricingandLicensingU.S.GovernmentciviliansatellitedataandEuropeanSentinel-2dataaredistributedtothepublicatnochargeandwithoutlicensingrestrictions.Commercialimageryusuallyhasuseandsharingrestrictionswhicharespelledoutinalicensetousetheimagery.Commercialsatelliteoperatorsalsousuallychargeforaccesstotheirimagery.LikeLandsat,allSentinel-2imageryismadepublicandhostedatcostincommercialcloud(AmazonWebServices[AWS]andGoogle),aswellasonmanycommercialservices.FindingsNoneofthecurrentsmallsatorcubesatsatellitesystemsdeployedtodatehavethetechnicalcapabilitiesrequiredbythethousandsofresearchers,governmentagencies,NGOs,andcommercialcompanieswhorelyonLandsatcontinuityforresearchandoperationaldecisionmaking.WhilethesmallsatsandcubesatsmayexceedLandsatcapabilitiesinspatialresolutionand/orrevisittime,noneofthesesatellitescurrentlyhavesensorswiththeneededspectralbands,calibrationstability,orswatharearequiredbythetensofthousandsofUSLandsatusers.Equallyimportant,unlikeSentinelandLandsat,noneofthecommercialprovidersofferimageryworldwidewithoutuserestrictionsandatnocost,animportantconsiderationforresearchersandagenciesrelyingonLandsatandSentineltosupportoperationaldecisions.Conversely,LandsatandtheCopernicusProgram’sSentinel-2multispectralbandsareverysimilarandcanbeusedincombinationwithoneanother.However,onlyLandsatprovidesmoderateresolutionthermalimagingcapabilities.EnhancedCapabilitiesforFutureLandsatMissionsWhilecurrentlyon-orbitsmallsatsandcubesatsareincapableofmeetingcurrentLandsatuserrequirements,decisionsregardingfutureLandsatcapabilitiesmustbemadewithinthecontextofcurrentandemergingtechnologyadvancements,aswellaschangesanticipatedintherapidlyevolvingmarketforbothgovernmentandcommerciallyprovidedsatelliteimagery.AsFigure3illustrates,thenumberofcommercialearthobservingsatellitesisprojectedtoquadrupleoverthenext10years.AstheU.S.GovernmentconsidersrequirementsforfutureLandsatsystems,theexistenceofSentinel-2andtheproliferationofcommercialsystemsofferopportunitiesfortechnologyinnovationandsynergies,yetalsopresentchallengesinensuringLandsatdatacontinuitywhilealsoavoidingcompetitionwithoperational,commercialcapabilitieswhichhavebecomeavailableinthelastdecade.Thefollowingsectionssummarizefourofthemostpromisingoptions,inorderofpriority,andliststheprosandconsofeach.



Figure3:Theprojectedgrowingsupplyofhighandveryhighresolutionsatelliteimagery.(Source:Euroconsult) Option1:MaintainCurrentLandsatCapabilitiesatLowerCostItwouldbeunconscionableforthenextLandsattonottakeadvantageofrapidlyemergingandincreasinglyproventechnicalinnovationswhichcouldgreatlyreducecostswhilemaintainingcontinuity.Opportunitiesdefinitelyexistforsubstantialsize,weight,powerandcostsavingsthroughadoptionofnewertechnologies,especiallyinsensorsandoverallspacecraftelectronics.Advancesinmicroelectronicsandsensors—drivenbothbyconsumerelectronicsandbyU.S.Governmentsponsoreddevelopments—haveenablednewclassesofspacemissions.WhilenoneofthedeployedsystemstodatehavecapabilitiesthatenvelopethoserequiredforLandsatcontinuity,therearemanyviableelements(bothatthecomponentlevelandthesystemdesignapproachlevel)thatcanbeappliedtodriveacosteffectiveLandsatsuccessor.Withmicroelectronicsperformancecontinuingtoimprovealongwithdecreasingsize,weight,andpower,thedriversforsatellitesizeareultimatelyitspayload(s)andthosesystemsthatscaletoaccommodatethepayload(e.g.,power,maneuvering).Forpassiveelectro-opticalremotesensing,thisisdrivenbytelescopeaperture,whichinturndrivesweight,thoughforresolutionsintheLandsatclassthisdoesnotbyitselfdriveweightabovethesmallsatclass.Asecondarydriverisfocalplanecomplexity.SensorstocollectallbandsthroughSWIRtomatchtheLandsat8/9OperationalLandImager(OLI)arerelativelyeasytoobtain.Siliconbaseddetectorscollectin



thevisibleportionofthespectrum,whilethosebasedonMerCad-Telluride(HgCdTe)cancollectshort-,mid-,orevenlong-waveinfrared.Sensorcostshavebeendecliningdramatically.Forexample,theWorldViewCAVISsensor(includingtelescope)wasbuiltforafewtensofmillionsofdollars,leveragingthesamescanningdetectorsasLandsat8andcapturingatotalof11spectralbandsfromvisiblethroughshortwaveinfrared.ToassuresuitabledeterminationofsurfacereflectanceeitheradditionalCAVISbandsatlowerresolutioncouldbeaddedtoLandsat.ImageryforaLandsatcontinuitymissionwithsuitableradiometricandgeometricaccuracyshouldbeachievableusingsmallersatellitesatalowercostthanaLandsat8/9OLIsensorassumingthepixelsizeiskeptto10metersoraboveandthesensorremainsnadirpointing.Otherchangesthatcouldreducecostsandsizearethereductioninthecomplexityandaccuracyofthestarsensorsusedforaccurategeoreferencingandon-boardlampsusedforsomecalibration.ThethermalIRsensoronLandsatisuniqueandthelackofathermalcapabilitywouldbeasignificantlosstoglobalearthobservationcontinuity.However,includingthermalinfraredimageryonasmallsatwithOLI-likeperformanceislikelytoconsiderablyincreasethecostofthesensoraswellassize,weightandpowerforcoolingthesensor.Technologyadvanceshavereducedthesize,weight,powerandcostofsatellitebuses,whichcreatemuchmoreopportunityfordisaggregatingsensorsinacost-effectivemanner(e.g.,separateOLIandThermalInfraredImagingSensor[TIRS]spacecraft).Thisisparticularlyhelpfulwhentherefreshraterequirementsofthedifferentsensingmodalitiesarenotthesame(e.g.,higherfrequencyrefreshonsomebandsthanothers,particularlyifthethermaldoesnotbecomethedrivingcase).Therefore,theoptionofflyingtheOLI-likeandTIRSsensorsonseparatebutcoordinatedplatformsisnowaviablealternative.

Pros:Lowercostswithoutlosingcontinuityofmeasurementscoupledwiththepotentialofhigherrefreshrates,whichwouldbeextremelyvaluableforagriculturalanddroughtmonitoringandemergencyresponseapplications.Multi-satelliteconstellationsaremoreresilienttoindividualcomponentfailures;theydegradegracefully(e.g.,degradedrevisit)ratherthanlosingcapabilityentirely,aswouldbethecasewithasinglesatellite.ThedisaggregationofthesensorsallowslaunchingTIRSsensorsconsistentwiththeirexpectedlife-cycleandsustainingacontinuousrecord.Cons:RequiresextensiveandprecisedesignworkupfronttorigorouslydemonstratehowathermalfreeflyerinformationwiththeOLItypesensorcanstillachievetherequireddegreeofsynopticity.Forexample,itwouldrequireastudytoshowtheabilitytoachievegeometriccalibrationthroughregistrationagainstabaselayer,etc.Recommendation:TheU.S.GovernmentshouldaggressivelyinvestigaterapidlyemergingandincreasinglyproventechnologieswhichcouldgreatlyreducethecostofLandsatmissions.IncludedinthisinvestigationshouldbeconsiderationofsmallersatelliteswithLandsat8/9OLI-likeperformanceandfreeflyerthermalmissionstomaintaincontinuityinLandsatthermalmeasurements.Asatest,itisrecommendedthattheU.S.GovernmentconsiderplacingathermalsensoronadedicatedfreeflyercompanionsatellitetooneoftheexistingEuropeanSentinel-2systems.Additionally,itisrecommendedthatastudybeundertakentodetermineifadditionalCAVISbandsorinputfromasuitableauxiliarylowerresolutionsatellite,couldbeusedtoreducecostsassociatedwithsensorsforradiometriccalibration.



Option2:AdopttheSentinelModelforCostSavingsandIncreasedTemporalandSpatialResolutionsSentinel-2hasestablishedanewstandardforEarthobservationsystems.ItsspectralresolutionisalsosimilartoLandsat,howeverwiththenotablelackofthethermalbands.Sentinel-2hasbeendesignedasafour-satelliteacquisition(e.g.afoursatellitebuywithtwosatellitesinorbitatanyonetime),therebyreducingdevelopmentandacquisitioncostspersatellite.Sentinel-2costsareestimatedat$250-300millionpersatelliteversusLandsat8’s$855millioncost.Sentinel-2isalsopartofalargercoordinatedprogramofsatelliteconstellations,includingSentinel-1C-bandSAR(similartoandimprovingontheCanadianMDARadarsatconstellation)andSentinel-3lowresolutiondailyglobalimaging(similartoandimprovingonNASA’sTerra/AquaMODISandNOAA’sSuomi-NPP/JPSSVIIRS).Sentinel-2hassetexpectationsforfuturepublicsatellitesystems,whiledrawingclosetothespatialresolutionthatcurrentlyseparatespublicimageryfromcommercialgradeimagery.Landsat10couldbeaconstellationofnewUS.instrumentsandsatellitesbuilttotheSentinel-2technicalspecifications.Alternatively,theU.S.couldseektoreducecostsbyleveragingtheexistingproductionrunofSentinel-2instrumentsandsatellites,eitherbylicensingthetechnologyororderingadditionalSentinel-2satellitesfromthecurrentmanufacturers.TheU.S.Governmentcouldthenapplythesavingstoproducingafree-flyingmedium-wave/thermalimagerthatprovidesthecurrentLandsatcapabilitynotpresentintheSentinel-2program.Inanyofthesecases,thenewLandsat10constellationshouldbeplacedinorbitsthataddtothecoverageprovidedbySentinel-2,e.g.,acoordinatedconstellationofSentinel-2A,2BandLandsat10A,10Bsatellitescouldprovideglobalcoveragewithsemi-weeklyimagingattheequator.

Pros:ReducescostsandensuresconsistentdatacollectionbetweenLandsatandSentinel-2systems;greatlyenhancesthecurrentrevisitratewhichisveryvaluabletoagriculturalanddroughtmonitoringandemergencyresponseapplications.Cons:CedesU.S.leadershipinmoderateresolutionearthobservation,whichwouldprobablyresultinariskoflossofCongressionalsupport;U.S.lackscontrolovercostanddesign.Recommendation:ToomanycriticalU.S.researchandoperationalprogramsrelyonU.S.leadershipinmoderateresolutionearthobservationsfortheU.S.tocedeitsleadershipinmoderateresolutionearthobservationstotheEuropeanCopernicusProgram.MaintainingU.S.homeland,foodandenvironmentalsecurityarealldependentupontheLandsatprogram.However,theU.S.shouldcontinuetoworkcloselywiththeEUbetterharmonizetheLandsatandSentineldatasets,obtaineconomiesofscalewherepossible,andsharelessonslearned.TheCopernicusapproachofbuildingmultiplesatelliteconstellationsatonceandlaunchingthemovertimeshouldespeciallybeinvestigatedtoreducedevelopmentandacquisitioncostspersatellite.

Option3:ImproveLandsatSpatialandTemporalResolutionIntherecentLAGstudy,AnalysisofNon-FederalLandsatUserRequirements(https://www.fgdc.gov/ngac/meetings/april-2016/landsat-user-requirements-analysis-ngac-june-2016.pdf),LandsatusersidentifiedimprovedspatialandtemporalresolutionasthemostimportantimprovementsneededforLandsat10.Savingsrealizedfromoptions1or2abovecouldbeusedto



improveLandsat10spatialresolutionto10metersglobalsemi-weeklycoverageatthefullLandsatspectralrangeincluding10meterthermal.Shorterintervalsbetweenobservationswouldrequireaconstellationofmultiplesatellites,andplanningtoacquire4to6satellitesfrominceptionoftheprogramwouldsignificantlyreducedevelopmentandacquisitioncostspersatellite.ThisconstellationwouldmaintainU.S.leadershipinpublic,globalEarthobservation.Itisimportant,however,thatsuchanapproachnotattempttoreplicatewhatcommercialfirmsaredoingorplantodo,asthiswouldplacetheGovernmentindirectcompetitionwithprivateenterprise,contrarytoUSspacepolicywhichdirectsthattheU.S.Governmentwill“…focusUnitedStatesGovernmentremotesensingspacesystemsonmeetingneedsthatcannotbeeffectively,affordably,andreliablysatisfiedbycommercialproviders…”(https://fas.org/irp/offdocs/nspd/remsens.html).Rather,suchanapproachshouldseektocomplementwhatthecommercialindustryisdoing.

Pros:IncreasedspatialandtemporalresolutionwhichhasbeenidentifiedasaLandsat10requirementbymultipleLandsatusers.IncreasedcompatibilitywithSentinel-2.Cons:Goingtohigherspatialresolutiontendstodriveupcosts,particularlyifthereisadesiretomaintainthesameswathwidth,asthenumberofpixelsinthefocalplanewillincreaseproportionally,whichdrivesbothelectronicscostandoptical/mechanicalcomplexity.SignificantlyhigherspatialresolutiononaLandsatsystemcouldbeinterpretedascompetingwiththecommercialsector,contrarytoU.S.SpacePolicy.Itisnotclearthatthisisthebestplacetobemakinginvestmentswhentheprivatesectorisalreadyprovidinghighresolutiondata,i.e.,isitcheaperforthoseapplicationswhichneedhigherresolution/revisitdata.Recommendation:TheLandsat10groundsampledistancebesetto10metersorlarger,soastoincreasecompatibilitywithSentinelsensors,ensurewiderswathwidths,increasecoverage,andreduceoverlapwithcommercialproviders.

Option4:ImproveLandsatSpectralResolutionIfcostsarelowered,multispectralnon-thermaltemporaland/orspatialresolutionimprovedthroughtheaboveoptions,andcontinuitymaintainedinthermalmeasurements,thenthepossibilityexistsfordevelopmentofamoderatespatialresolutionhyperspectralsystemflowninconstellationwiththemultispectralandthermalLandsatsystems.Super-orHyperspectralimagerywouldenhancetheLandsatrecordbyprovidingtheabilitytomoreaccuratelyidentifyandmonitorphenomenaontheEarth’ssurface.Conversely,ifitisfoundacceptabletocedeleadershipingloballandimagingtotheEU(Option2above),theU.S.GovernmentcouldacknowledgethatSentinel-2nowprovidesLandsat-likeglobalcoverageinthevisibletoshortwaveinfrared,andinsteadseektoprovideanewcomplementaryEarthobservationcapability,e.g.,developamedium-wavetothermalinfraredmulti-spectralinstrument,orexplorehyperspectralimaging.

Pros:DemonstratesU.S.spaceleadershipbyprovidinganewvaluablecapabilityfreelyavailabletothepublic.Cons:Additionaldevelopmentandoperationalrisk.Riskofcompetingwithnewcommercialspectral-imagingconstellations(plannedbutnotyetoperating).



Recommendation:TheU.S.GovernmentshouldinvestigatethebenefitsandcostsofincreasingLandsatspectralresolution.

OpportunitiesforPublic-PrivatePartnershipsEachof7successfulLandsatmissionshasresultedfromacollaborationbetweenpublicandprivateorganizationsinthatthegovernment(currentlyNASAandUSGS)definesitsrequirementsandawardscontractsprimarilywithprivatecompaniestoprovidethesatelliteandrocket.Followinglaunch,theGovernment(currentlyUSGS)operatesthesatelliteandgroundstation,oftenusingpersonnelcontractedfromprivatecompanies.However,thistypeofcollaborationdoesnotmeetthetypicalmodelofpublic-privatepartnershipwheretheprivatepartnerputssomeresourcesatriskwhichareoffsetbyexpectedcommercialrevenueandlowercoststotheGovernment.Severalpublic/privatepartnershipmodelsexistwhich,ifappliedtotheLandsatprogram,havethepotentialtoreducecoststotheGovernmentbyoffsettingsomeofthosecostswithcommercialrevenue.FundamentaltothesemodelsistheconceptthattheGovernmentdoesnotmakefreelyavailablethesameproductthatthecontractoristryingtocommercialize,asotherwisethereisnooffsettingcommercialrevenueopportunity,andtheGovernmentendsupbearingthefullcostoftheprogram.Therefore,tobesuccessful,asubstantiallylargedemandforthecommercialproductmustbeprojectedtoexist.Twomodelsarediscussedhere.“NextView”or“EnhancedView”ModelTheNationalGeospatial-IntelligenceAgency(NGA)hasacquiredcommercialhighresolutionsatelliteimageryoverthepastdecadeunderwhatisknownasthe“NextViewlicense.”NGApaysacommercialdataprovideranannualfee(whatisknownasa“ServiceAccessAgreement”orSAA)inexchangeforhavingtheabilitytousedataavailableviatheEnhancedViewcontract,includingtheabilitytotaskapercentageoftheprovider’scapacity(roughlyhalf).NGAcanusethatdatawithintheU.S.Government.Itcanalsoshareit(withsomelimitations)withallies,coalitionpartners,andfirstresponders,butitisnotallowedtomakethedataopenlyavailabletothepublic.Avariantonthismodel,whichwasusedintheoriginalNextViewcontracts,hastheGovernmentco-fundthedevelopmentofthesatellite(s)inexchangeforlowercostduringoperations.Thisapproachtradesoffthetimingoffunding(moreupfront)forlowertotalcostoverlifetime.Bothvariantsofthismodelworkbecausethecommercialprovideristhenfreetomonetizeitsdatawithnon-NGAcustomers.Therevenueearnedinthisfashionenablestheprovidertooffsetthecosttothegovernment,soNGApayslessthanitwouldhaveforadedicatedsystem.Asaroughdatapoint,thenon-NGArevenuesfromDigitalGlobe,thecurrentEnhancedViewcontractor,exceedthevalueoftheSAA.AnanalogueofthisforLandsat(orasimilarprogram)mightbetoenabletheGovernmenttosharedatafreelywiththeresearchandpublicagencycommunities,butanycommercialapplicationwouldneedtoprocuredatafromthecontractor.However,thedemandforLandsatimageryisoverwhelminglyderivedfromtheresearchandpublicgovernmentsectors,anditisunclearifalargeenoughcommercialdemandexiststosupportthismodel,especiallywhenSentinel-2dataisfreelyavailableandcanbesubstitutedforLandsatimageryinmanyapplications.



Pros:TheadvantageofsuchanapproacharethatcoststotheU.S.Governmentcouldbereducedduetoinvestmentsfromprivateindustryandhavingprivateindustryefficiencyaidinthelaunchandmanagementofthesatelliteswhichshouldfurtherreducedcosts.Cons:ThedisadvantageofthisapproachisthatitisunlikelythattheU.S.GovernmentwouldbeabletoconvinceaprivatecompanytoagreetotermsunlesssubstantialrestrictionswereplacedonthedistributionofLandsatdatatopublicagenciesandresearchorganizationswhichwouldinvalidatemanyoftheLandsatbenefitsandruncountertothegoalsoftheSustainableLandImagingprogram.

“PayforSuperiorData”ModelThispublic-privatemodelwouldentailtheU.S.Governmentcontractingwiththeprivatesectortobuildandlaunchaconstellationofsensorswithspecifiedresolutions,calibrationstandards,andspatialaccuraciessetbyGovernmentrequirements.Thecontractorwouldthenhavetheoptionofsellinghigherqualitydataintoallmarkets.Inthisapproach,thecontractorwouldbuildasystemthatwouldcollectdatathatexceededtherequirementsforLandsatcontinuity,butwouldprovideaLandsatrequirements-compliantsubsetofthisdatatoNASA/USGStobefreelydistributed.Thecontractor’ssystemcouldexceedLandsatrequirementsinanyofanumberofways(e.g.,higherspatialresolution,morespectralcoverage,moretemporalrevisit,highercalibrationstandards,spatialaccuracy,etc.).Forexample,theLandsatrequirementforspatialresolutioncouldbe30meterswiththecontractorsuperiorspatialresolutionat10metersorhigher.Thecontractorwouldhavecommercialrightstothefull-capabilitydata,whichitcouldmonetizebecausewhatNASA/USGSsharedfreelywasfundamentallyadifferentproductandsowouldnotcannibalizethecommercializationopportunity.Thisapproachinprincipleissoundaslongasthereissufficientdemandforthesuperiordatacollectedbythecontractor’ssystemanditisdifferentiatedfromthefreelydistributedLandsatdatabyenoughtobevaluedbythemarketandenablethecontractortoearnareturnand,thus,closeitsbusinesscase.In2002-2003,NASAconductedseveralformulationphasestudiesforavariantofthismodelfortheLandsatDataContinuityMission(LDCM).However,theapproachfailedintheoriginalLDCMbecausethebiddersandNASAwereunabletocometoagreementontermsthatenabledthebidderstoclosetheirbusinesscases,butthiswasduetospecifics(i.e.,allocationofriskandeconomicterms)ratherthananintrinsicflawinthemodel.Circumstances,markets,andtechnologieshavechangedwhichmaymakethismodelnowmoreviable.Forexample,thecompanyUrtheCastisbuildingandplanningtolaunchaconstellation(UrtheDaily)ofsatellitesin2020toprovideglobaldailylargeswathwidthcoveragewith5meterGSDandspectralbandssimilartothoseofLandsat-8andSentinel-2(exceptforthethermalband).Theremaybeanopportunitytolicensetherightstoalowerresolution20meterdataversionoftheproductsandprovidethesetotheLandsatcommunity.U.S.GovernmentdevelopmenteffortscouldthenbefocusedonprovidingacompanionTIRSconstellation.

Pros:TheadvantageofthisapproachisthattheU.S.Governmentwouldgainmostbytheefficienciesofprivateindustry,whilemaintainingLandsatcontinuity.Italsopreservespublic/openavailabilityofLandsat-qualitydata.Cons:Thisapproachisdependentonthecontractor’sabilitytodevelopabusinessmodelthatclosesbasedonthe“uppertier”ofdataqualitywhichisdifficult.Anotherdisadvantage



oftheapproachisthatitcanintrinsicallyincreasethecostofsystembyrequiringincreasedcapabilities,andmakesthesystemincumbenttotherequirementsofaprivateparty,andnotjusttheGovernment.

Recommendation:TheU.S.Governmentshouldconductamarketstudytodetermineifsufficientdemandexiststosupportexplorationofthecreationofapublic-privatepartnershipwherethecontractorprovidestwoormoretiersofdata-onemeetingU.S.GovernmentLandsattechnicalrequirementsforopenandfreedistribution,andothersthatprovide“superior”datawhichissoldtousers,therebycreatingasufficientrevenuestreamtooffsetatleastsomeofthecostsofbuildingandoperatingthesystem.Ifthismodelispursued,thegovernmentmustensurethatthereisanequitablebalanceofriskbetweentheGovernmentanditsprivatesectorpartner.AcknowledgementsThispaperwasapprovedbytheNGACLandsatAdvisoryGroup(LAG)onMarch20,2018andadoptedbytheNGACasawholeonApril3,2018.TheLAGteamdevelopingthispaperincludedKassGreen,KassGreen&Associates(TeamLead);PeterBecker,Esri;StevenBrumby,DescartesLabs;andWalterScott,DigitalGlobe.

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