NationalAeronauticsandSpaceAdministration

Mapping soil moisture and freeze/thaw state from space

Soil Moisture Active Passive (SMAP)PRODUCTS

The SMAP Mission

Objectives:SMAPmeasurementswillbeusedtoenhanceunderstandingofprocessesthatlinkthewater,energy,andcarboncycles,andtoenhancethepredictiveskillofweatherandclimatemodels.SMAPdatawillalsobeusedtoquantifynetcarbonfluxinboreallandscapesandtodevelopimprovedfloodpredictionanddroughtmonitoringcapabilities.

Observatory:TheSMAPobservatoryemploysadedicatedspacecraftwithaninstrumentsuitethatwillbelaunchedonanexpendablelaunchvehicleintoa680-kmnearpolar,sun-synchronousorbit,withequatorcrossingsat6AMand6PMlocaltime.

Instrument:TheSMAPinstrumentincludesaradiometerandasyntheticap-ertureradaroperatingatL-band(1.20-1.41GHz).Theinstrumentisdesignedtomakecoincidentmeasurementsofsurfaceemissionandbackscatter,withtheabilitytosensethesoilconditionsthroughmoderatevegetationcover.Theconically-scanningantennacoversa1000kmswathprovidingglobalcoveragewithin3daysattheequatorand2daysatboreallatitudes(>45°N).

Operations:SMAPsciencemeasurementswillbeacquiredforaperiodofthreeyears.Acomprehensivevalidationprogramwillbecarriedoutafterlaunchtoassessthesciencedataproducts.Theproductsfromtheseactivi-tieswillbemadeavailablethroughaNASAdataarchivecenter.

Sample Products

Level 1B Radiometer

• L1Bradiometercoverageiscontinuous(AMorPM,fore/aftscans)overallsur-facetypes

• ContainsEarth-located,calibratedbrightnesstem-peraturesatH,V,and3rd&4thStokespolarizationsforeachFOVfootprint,intime-order

• FOVfootprintresolutionisapproximately40km

• 3rdStokesmeasurementsareusedtoinferFaradayrotationcorrectionstotheH&VTBmeasurements

• EASEgridcoordinatesforglobal&polar36kmgridforeachfootprint

Level 1C High Resolution Radar

• Hascoverageoverlandandcoastaloceans,ontheAMorbitpass(AMandPMforregionsabove45°N),andusestheforwardandaftpartsofthescanfortheAMpass

• AllowsSARprocessingtoenablehigh-resolutionsingle-lookmeasurements;hasvariedresolutionfrom~400mattheswathedgetoabout1.2kmwithin150kmofthenadirsubtrack;hasnadirlooksthatarethinslicesaswideasthebeamfootprint

• ContainsEarth-locatedandcalibratedradarback-scattermeasurementsforHH,VVandHV

VolumetricSoilMoisture(cm3/cm3)

Level 2 and 3 Soil Moisture Active/Passive

• Mergesactive(radarHHandVV)withpassive(radiometerHandV)channelsusingatime-seriesalgorithmandspatialheterogeneityofL1Cradarproductstoretrieve~9kmsoilmoistureproductoverlandwith0.04cm3cm-3accuracyforlow-to-moderatelyvegetatedareas(VWC≤5kg/m2)

• Dependsontransientwaterbodyandfreeze-thawstatere-trievalsfromHiResradar

• Level3dailycompositemadefromLevel2half-orbits

• Providesglobalcoveragein3days

Level 3 Freeze/Thaw

• Quantifiesdailylandsur-facefreeze/thawstateasabinaryconditionoflandsurface

• Usesthe1kmL1CradarHiResdatawithatime-se-rieschangedetectionalgo-rithmtoinferfreeze/thawstate

• 80%F/Tspatialclassifica-tionaccuracy

• Resultsinthepostingofoutputdataat1-3kmspa-tialresolutionwith2dayav-eragetemporalintervalsforregionsabove45°N

DailyFreeze/ThawState

17February1998

1April1998

2April1998

15May1998

28June1998

24September1998

Level 4 Surface and Root Zone Soil Moisture (L4_SM)

• MergesSMAPobserva-tionswithsoilmoistureesti-matesfromalandsurfacemodelinalanddataas-

similationsystem,yieldingaproductthatissuperiortosatelliteorlandmodelestimatesalone

• Providesglobalsurface(top5cm)androotzone(top1m)soilmoistureestimatesat~9kmand3-hourlyreso-lutionthatarespatiallyandtemporallycompleteandconsistentwithSMAPob-servations

• Includessurfacemeteoro-logicalforcingfields,landsurfacefluxes,soiltem-peratureandsnowstates,runoff,anderrorestimatesasresearchoutput(validat-edonabesteffortbasis)

Thawed

Frozen

80 120 160

L1BTime-orderedH-polTB(K) L1CRadarBackscatterCross-Section[dB]

200 240 280 -25 -20 -15 -10

0.0 0.1 0.2 0.3 0.4 0.5

SoilMoisture(cm3/cm3)0.0 0.1 0.2 0.3 0.4 0.5

PanArcticNEE(gCm-2d-1)2003177-7 -4 -2 0 42 >7

Frozensoil

Level 4 Carbon Net Ecosystem Exchange (L4_C)

• Constrainscarbonfluxestimatesfromasoilres-pirationmodelandsatel-liteobservationsofgrossprimaryproductivitywithSMAPobservations

• Providesenhancedglobalestimatesofcarbonfluxesat~3kmanddailyresolution

• UsesL3_F/TandL4_SMbasedsoilmoistureandtemperaturewithancillarylandcoverandvegeta-tionproductivityinputstopredictnetecosystemCO2exchange(NEE)withtheatmosphere

• L4_Caccuracy(RMSE)commensuratewithinsitutowermeasurements(NEE<30gCm-2yr -1or1.6gCm-2d-1)

• Resultspostedto9-kmglobalgridwithdailytem-poralfidelity

www.nasa.gov See reverse side for complete list of data products

Mapping soil moisture and freeze/thaw state from space

Soil Moisture Active Passive (SMAP)PRODUCTS

Science Objectives

SMAP will provide a capability for global mapping of soil moisture and freeze/thaw state with unprecedented accuracy, resolution, and coverage. SMAP science objectives are to acquire space-based hydrosphere state measurements over a three-year period to:

•understandprocessesthatlinktheterrestrialwater,energy,andcarboncycles;

•estimateglobalwaterandenergyfluxesatthelandsurface;

•quantifynetcarbonfluxinboreallandscapes;

•enhanceweatherandclimateforecastskill;

•developimprovedfloodpredictionanddroughtmonitoringcapabilities.

TheSMAPmissionwillenableglobalsoilmoisturemappingwithunprecedentedresolution,sensitivity,areacoverage,andrevisit.Soilmoisture,asthestatevariableofthewatercycleoverland,determineswaterfluxesbetweentheatmosphere,surface,andsubsurface.Becausealargeamountofheatisexchangedwhenwaterchangesphase,thewatercycleisalsofundamentaltothedynamicsoftheEarth’senergycycle.SincewateristheultimatesolventintheEarthsystem,biogeochemicalcycles(carbon,nitrogen,methane,andothers)areembeddedinthewatercycle.Throughtheseeffects,whicharelinkeddirectlytoclimateandtheenvironment,SMAPobservationswillbetransformationalforelementsofEarthsystemscience,forwaterresourceassessment,andfornaturalhazardsmitigation.

SMAP Science Data Products

Data Product Short Name

Description Data Resolution Median Latency*

L1A_Radar Radarrawdataintimeorder — 12hrs

L1A_Radiometer Radiometerrawdataintimeorder — 12hrs

L1B_S0_LoRes Lowresolutionradarσointimeorder 5x30km 12hrs

L1B_TB RadiometerTBintimeorder 40km 12hrs

L1C_S0_HiRes Highresolutionradarσo(halforbit,gridded) 1x1kmto1x30km 12hrs

L1C_TB RadiometerTB(halforbit,gridded) 40km 12hrs

L2_SM_P Soilmoisture(radiometer,halforbit) 40km 24hrs

L2_SM_A/P Soilmoisture(radar/radiometer,halforbit) 9km 24hrs

L3_F/T_A Freeze/thawstate(radar,dailycomposite) 3km 48hrs

L3_SM_P Soilmoisture(radiometer,dailycomposite) 40km 48hrs

L3_SM_A/P Soilmoisture(radar/radiometer,dailycomposite) 9km 48hrs

L4_SM Soilmoisture(surface&rootzone) 9km 7days

L4_C CarbonandNetEcosystemExchange 3km 14days

*TheSMAPProjectwillmakeabestefforttoreducethedatalatenciesbeyondthoseshowninthistable.TheSMAPbaselinesciencedataproductsareshowninthistable.ThesedataproductswillbemadeavailablethroughaNASA-designateddatacenter.Theprod-uctswillconformtotheHDF-5standard.

Spatial Resolution:Radiometermeasurementsofsurfaceemissioncanbeinvertedtoestimatesur-facesoilmoisturewithhighsensitivitybutatcoarsespatialresolution(40km).Radarbackscattermea-surementsareathigherspatialresolution(1-3km)buttheyarelesssensitivetothesurfacesoilmois-ture.TheSMAPobservatoryanditsactive-passiveapproachtoL-bandmeasurementsisdesignedtoproduceacombinedradar-radiometersoilmoistureproductthathasanoptimalblendofresolution(9km)andaccuracy(0.04cm3cm-31-sigmaerror)tomeetscienceobjectives.Thehighresolutionoftheradarisalsocriticalforaccuratedeterminationoffreeze/thawstateintheheterogeneouslandscapesoftheborealforestregionnorthof45°Nlatitude.

Data Availability:SMAPwillcoordinatethere-leaseofdataproductversionstoaNASA-designat-edEarthsciencedatacenterandwillensurethecompletenessandaccuracyofqualitycontrolinfor-mationandvalidationstatusofthedataproducts.

RadiometerFrequency: 1.41GHzPolarizations: H,V,3rdand4thStokesRelativeaccuracy: 1.3KDatacollection: ContinuousoverfullscanIncludesdesignstodetectandmitigateRadio-FrequencyInterference(RFI)

RadarFrequency: 1.26GHzPolarizations: VV,HH,HVDatacollection: •High-resolution/high-rate

datacollectedoverlandandcoastalwatersforSARprocessing

•Low-resolutionreal-aperturedatacollectedcontinuously

Antenna ConfigurationConically-scanningreflectorsharedbybothradarandradiometerDiameter: 6meters

Rotationrate: 14.6RPM

Forms1000kmwideswath

Resolution: 40kmradiometer,1-3kmSAR

Beamefficiency: 90%

ConstantIncidenceAngle(40°)

SMAP Working Groups

WorkingGroupshavebeenestablishedasameanstoenablebroadscienceparticipationintheSMAPmission.TheworkinggroupsareledbyScienceDefinitionTeam(SDT)membersandprovideforumsforinformationex-changeonissuesrelatedtoSMAPscienceandapplicationsgoalsandobjectives.Theworkinggroupscommu-nicateviaemailandatmeetings,conferencesessions,workshops,andothervenues.

• AlgorithmsWorkingGroup(AWG)• Calibration&ValidationWorkingGroup(CVWG)• Radio-FrequencyInterferenceWorkingGroup(RFIWG)• ApplicationsWorkingGroup(AppWG)

Tojoinandfollowworkinggroupspleasevisit:http://smap.jpl.nasa.gov/science/wgroups/

Web Site

PleasevisitourwebsiteformoreinformationaboutSMAP:

http://smap.jpl.nasa.gov

EW-2010-9-036-GSFC