ã2017CaliforniaInstituteofTechnology.Governmentsponsorshipacknowledged.

NISAR:TheNASA-ISROSARMission

MonitoringNaturalandManmadeHazardsinTexasThe state of Texas is vast, and simply keeping track ofconditionseverywhereacrossthestateisimpossiblefromtheground. Frequentobservationsareneeded to trackthewiderangeofhazards,rangingfromthosethat

develop rapidly, like flooding, toothers that takea longtimetobeseen,suchaslandsubsidence.Thesolutionistomonitorfromspace.

NaturalandManmadeHazardsintheStateofTexas

TexasisrankedfirstintheU.S.inthevarietyandfrequencyofnaturaldisasters.Flooding,wildfires,tornados,hurricanes,hailstorms,sinkholes,erosionanddroughtalloccurinthestate.Sometimes,evenutilizationofthestate’snaturalreservesofoil,gas,andwatercanleadtosubsidenceandearthquakes.

A Large Range of Hazards in Texas AtleastonemajordisastereventisdeclaredeveryyearinthestateofTexas.Thesouthernextentof“TornadoAlley”reachesintotheheartofTexas,causingtornadoesthroughouttheyear.Inthespringandfall,hurricanes(suchastherecentdevastatingHarvey)cancauseseveredamageinthesouth,whileextremetemperaturesinthesummercreateconditionsthatleadtoseveredroughtsandwidespreadwildfires.Despitethelowaverageannualprecipitation,largeareasofTexasareoftenfloodedduringperiodsofintense,short-termrainfall.Geologically,Texasisprimarilycomposedofsaltdomesandsedimentarylayersthatholdvaluableoilandgasdeposits,butarealsoeasilydissolvedbywater,whichmakestheareapronetosinkholes.Injectionoffluidsforoilandgasproductionhasincreasedthefrequencyofearthquakes,sothatTexasisnowoneofthemostseismicallyactivestatesinthenation.Withdrawalofextremeamountsofgroundwater,aswellasthelonghistoryofhydrocarbonproductionalongtheGulfCoast,hascausedsomeareastosink(landsubsidence),andthesepopulatedareashavebecomeevenmorevulnerabletotheeffectsoftheplethoraofnaturalhazardsthatoccurinthestate.

TheNISARMission–ReliableObservationsforHazardMitigation

The NASA–ISRO Synthetic Aperture Radar (NISAR)mission, a collaboration between theNational Aeronautics and Space Administration (NASA) and the Indian Space ResearchOrganization (ISRO),willprovideall-weather,day/night imagingofnearlytheentire landand icemasses of the Earth repeated 4-6 times permonth.NISAR’s orbiting radars willimageatresolutionsof5-10metersto identifyandtracksubtlemovementoftheEarth’sland and its sea ice, and even provide information aboutwhat is happening below thesurface.Itsrepeatedsetofhighresolutionimagescaninformresourcemanagementandbeusedtodetectsmall-scalechangesbeforetheyarevisibletotheeye.Providinginformationfordisasterresponseandrecovery,forexample,followingfloodsortornadoes,isapriorityforthemission.Productsareexpectedtobeavailable1-2daysafterobservation,andwithinhoursinresponsetodisasters,providingactionable,timelydataformanyapplications.

Photos:UL(NOAA),UR(TexasA&MForestService),LL(NOAA),andLR(FEMA)

ã2017CaliforniaInstituteofTechnology.Governmentsponsorshipacknowledged.

NISAR:TheNASA-ISROSARMission

Toaccuratelyaddresstheadverseeffectsoneconomyandenvironment associatedwith various natural hazards inTexas, it is critical to use radar observations, such asNISAR, that can collect data regardless of weatherconditions,duringbothdayandnight.Radarimagescandelineateareasaffectedbyhurricanes,tornadoes, or other severe weather events to helpevaluate the magnitude and severity of the damage.Large-area-coverage and frequent-revisit radarobservations from NISAR can also be used in theestimation of changes in soil moisture to determinedrought conditions. These are particularly effective inmapping and monitoring flood extents, even duringinclementweather conditionswhen optical instrumentscannot see through the clouds. Using radarinterferometry (InSAR), radar images can be used tomonitorlandsubsidencecausedbyprocessessuchasthecompactionofundergroundwater-bearingrock,sinkhole

collapse, or hydrocarbon extraction. This allows for theidentification and classification of the causes andmechanisms responsible for the observed land surfacemovement, so that action can be taken to prevent,reduce, or mitigate the damages incurred from suchhazards. InSAR data is also effective when applied toseismic hazards, and has proven useful in theidentificationandmonitoringofactivefaults.Inthisway,seismicriskcanbedetermined.NISAR will be the first NASA earth observing radar toimageall theU.S. landsandcoastalwatersona regularbasis,witheverylocationimagedatleastonceaweek.AllNISARdataproducts,includingtheInSARimages,willbeavailablethroughanopenaccesswebportal.Inthisway,thenation’sinvestmentinlandsurveysremotelyacquiredfrom space can be most widely used to help preventnaturalandaccidentalhazardsfrombecomingdisasters.

NationalAeronauticsandSpaceAdministration Formoreinformation,visithttp://nisar.jpl.nasa.gov/applications

JetPropulsionLaboratory/CaliforniaInstituteofTechnology/Pasadena,California/www.jpl.nasa.gov

Land Subsidence in Harris County, Texas

ThefiguretotherightshowsamapoftheaveragegroundmovementaroundtheHoustonareaderivedfromradarimagesobtainedfrom1995-1998.Duringthattime,thepeaklandsurfacedrawdownwasabout50mm/yearoverHarrisCountryinnorthwesternHouston[Quetal.,2015].Landsubsidence,likethatshowninthisfigure,hascausedextensivedamagetobuildingsandinfrastructure,resultinginthelossofgroundwaterstorage,reactivatedfaults,generatedfissures,andincreasedseawaterintrusionthatcausedlossofwetlandhabitat.MeasuringlandsubsidenceisjustoneexampleofhowNISARwillallowustoidentifyandmonitorthevarioushazardsoccurringstatewideinTexas,sothatwecanbetterprotectlives,property,resources,theenvironmentandtheeconomy.Ground-basedmonitoringtechniquesandGPSobservationsprovideprecisesubsidencemeasurements,buttheyonlymeasurewhatishappeningatasinglelocation.Radarcanprovidehigh-accuracymeasurementsofgroundmovementoverlargeregionsthroughtime,enablingustogetabetterunderstandingoftheevolutioninbothspaceandtimeofprocessesresponsiblefortheobservedlandsurfacechanges.