simpl greenland 2015 campaign - icesat-2 · kurt rush, electronics engineer lead beth timmons,...

Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC

SIMPLGreenland2015Campaign

SIMPLTEAMDavidHarding,PrincipalInves:gator

PhilipDabney,InstrumentScien:standSystemEngineerSusanValeO,LeadSoPwareEngineerLead

AnthonyYu,Electro-op:calPhysicistandTransmiOerLeadKurtRush,ElectronicsEngineerLeadBethTimmons,SoPwareEngineer

GerryMcIn:re,MechanicalEngineerRayDesilvester,MechanicalEngineer

SIPSTEAMDavidHancock,SIPSLead

VijaySuchdeo,HDFSoPwareDevelopmentandDataProcessingAndyGriffen,HDFDataProduc:on

March30,2016

DocumentVersion1.1

G O D D A R D S P A C E F L I G H T C E N T E R

Release5DataProductDocumenta:onandInstrumentDescrip:on

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TableofContents

Release5ProductChangesandLimita:ons 3CampaignOverview 7SIMPLDataProducts 23SIMPLInstrumentDescrip:on 44AncillaryData:Applanix,CameraandHyperspectral 52References 59

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March30,2016DocumentVersion1.1



FordetailsseeHardingetal.,SIMPL_2015_Rel5_Calibra:on_v1.1ImprovementsoverPriorReleasesGeoloca3on

•  Precisepoin:ngand:mingbiasesdeterminedfromrollandpitchmaneuversoverwaterhavebeenappliedduringgeoloca:on.Poin:nganglesforeachchannelwithrespecttotheApplanixPOS/AV610deviceusedtomeasureposi:onandaatudearegivenin/flight_parameters/angle_1064_mradandangle_532_mrad.Timingbiases,inseconds,foreachchannelbetweenSIMPLandtheApplanixaregivenin/flight_parameters/tod_bias_1064andtod_bias_532.Thepoin:nganglesand:mingbiasesareconstantvaluesusedforallprocessing.

•  TimeoffsetsfortheNIRperpendicular,NIRparallelandGreenperpendicularchannelsrela:vetotheGreenparallelchannelsarealsoappliedduringgeoloca:on.Thesearedeterminedforeachgranuleindividuallybasedonalong-beamsurfaceslopecorrela:on.Theyarereportedinthe/Auxiliary/TimeOfDayOffsetfolders.

•  APergeoloca:ontheeleva:onresidualerrorsforflatsurfaces(waterdeparturefromaflatsurfaceduringthemaneuvers)are~1cmper1°offnadirforeachofthe16channels.Thiscorrespondstoahorizontalerrorof~10cmper1°offnadir.

•  Absoluterangebiasesforeachofthe16channelshavealsobeenappliedduringgeoloca:on.Theyarereportedin/flight_parameters/path_length_1064_mmandpath_length_532_mm.Theyweredeterminedbasedonrangingoverahorizontalpathtoafixedtargetatknowndistance.Theyareconstantvaluesusedforallprocessing.Basedonini:alanalysistheseyieldbetween-channeleleva:onaccuraciesatthedecimeterlevel.Confirma:onoftheabsoluteaccuracywithrespecttoanindependenteleva:onsourceispending.

ImpulseResponseParameters•  Parametersin/Auxiliary/ImpulseResponsedocumen:ngtheTransmitEchoPulse(TEP)havebeenimproved.ThemainandaPerpulseposi:onsandwidthsarenowcomputedusingfitstothepulseleadingandtrailingedgesimprovingtheirprecision.Theaccuracyoftheprobabilityofdetec:onparameterhasalsobeenimproved.

•  ParameterstocharacterizetheTEPvariabilityduringaflighthavebeenaddedintheMAINPULSETOMEANOFFSETandCENTROIDLINEARFITPARAMETERSfoldersin/Auxiliary/ImpulseResponse.

Release5ProductImprovementsandLimita:ons:1of3

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FordetailsseeHardingetal.,SIMPL_2015_Rel5_Calibra:on_v1.1Limita3onsSnow,iceandwaterpenetra3ondepth

•  Thedecimeter-levelabsoluteeleva:onaccuraciesdonotmeettheobjec:veofbetween-channeleleva:onaccuraciesatthecen:meterlevelforthefourchannelsoneachbeam.Workisongoingtoimprovethisaccuracy.Improvedabsoluteeleva:onbiaseswillbereportedonthiswebsitewhentheybecomeavailable.

•  TheTransmitEchoPulse(TEP)methodtomonitor:mevariabilityoftheeleva:onbiaseshasnotbeenimplementedduetocomplexi:esinthosemeasurements.Workison-goingtoassess:me-variabilityusingtheTEPproductswhichareprovidedin/Auxilliary/ImpulseResponse.Resultsofthatanalysiswillbereportedonthiswebsitewhentheybecomeavailable.

•  Calibra:onofthefirstphotonbiasforeachofthe16channelsatthecen:meterlevel,rela:ngcentroideleva:onoffsettoprobabilityofdetec:on,ison-going.Calibra:onparameterswillbereportedonthiswebsitewhentheybecomeavailable.


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FordetailsseeHardingetal.,SIMPL_2015_Rel5_Calibra:on_v1.1Limita3onsImpulseResponsePulseShapes

•  Theobjec:vetoprovide:me-varyingpulseshapesforeachchannelnotbeenreachedinRelease5.Thepulseshapesareprovidedin/Auxilliary/ImpulseHistogramsbutduetocomplexi:esintheTransmitEchoPulse(TEP)measurementmethodthesearenotreliable.Workison-goingtoproviderobustimpulseresponseswhichwillbeprovidedonthiswebsitewhentheybecomeavailable.

SignalAmplitudes•  Theamplitudeparametersin/Auxillary/PRNandchannelra:osin/Auxillary/PRNRarebasedonun-calibratedphotoncountsandarethereforenotconsistentbetweenchannelsandbeamsbecauseofinstrumenta:oneffects.Channelscalefactorstoderivenormalizedamplitudesandra:osareprovidedin/Auxillary/Ampi:ude_Scale_Factors.Thesearecurrenltysetto1.Workison-goingtodeterminethesevalueswhichwillbeprovidedonthiswebsitewhentheybecomeavailable.

MissingGranules•  Somegranulesaremissing,introducingdatagaps,dueto:meofdayerrorsinthegranulestartand/orend:mes.Forsomegranulesthe:meerrorshavebeencorrectedandthedataison-line.Workison-goingtocorrectsomeoftheothergranuleswhichwillbepostedastheybecomeavailable.Ifyouaremissingcri:caldatapleaseletusknow.GranulesforJuly21cannotbecorrectedandwillnotbeposted.IthasnotbeendeterminedifgranulesforJuly23andAugust11canbecorrected.


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Limita3onsSIMPLDatadelta_3meOffset

•  delta_:mesinthe/Auxillary/PRNand/Auxillary/PRNRfoldersuseadifferentreference:methanthedelta_:mesinthe/impulse,/insand/photonfoldersandsocannotbeuseddirectlytoalignthesedatatypes.ToalignthesedatatoGPSTime(secondssincethefirstGPSepoch)use:PRNandPRNRfolders=delta_:me+[604,800sec/weekxstart_gpsweek(in/ancillary_data)]+[86,400sec/dayxdayofweek]

Impulse,insandphotonfolders=delta_:me+gps_sec_offset(in/ancillary_data)

DayofweekforeachflightisprovidedinTable1.FrameCameraTimeOffset

•  Theframecamerafilenamesprovidehr:min:secsynchedtoGPS1pulsepersecondsignals.FortheJulyflightsa-4houroffsetwasappliedtothefilenamesduringimagerecordingconver:ngtoEDT.FortheAugustflightstheoffsetwassetto0.


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FlightDate GPSWeek DayofWeekFramecameradeltatooffsettoGPS:me(hrs)

20150721 830 2 420150723 830 4 420150729 ASDcalibra:on;noSIMPLdata 420150730 831 5 420150803 832 1 020150804 832 2 020150807 832 5 020150810 833 1 020150811 833 2 020150812 833 3 020150813 833 4 020150814 833 5 020150817 834 1 0


CampaignOverview

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SIMPL2015GreenlandCampaignTeam

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FromlePtorightGoddardSIMPLTeam:

AnthonyYu,SusanValeO,PhilipDabney,DavidHarding,BethTimmonsandKurtRushAmesApplanixInstalla3onandProcessing:

DennisGearhart,JamesJacobsonGoddardICESat-2ProjectScienceOffice:

KellyBrunt,KaitlinWalshGoddardASDProfilingSpectrometer(notshown):

ChrisCrawfordNASALangleyAircraQOpera3ons(notshown):

RickYasky,MikeWusk,AndyHaynes,DavePerez,SeanDeRubba


•  Con:nuingpolarwarmingisincreasingtheamountofmel:ngduringthesummercontribu:ngtoicesheetmassloss,resul:nginsealevelrise,andseaicethinning

•  ICESat-2willmeasurechangesinicesheeteleva:onandseaicethicknessusingtheATLASlaseral:meter

•  ATLASmeasurestheround-triptravel:meofhigh-repe::onratelaserpulsesalongsixbeams(3groupsof2)bymeasuringthepulsetransmit:meandreturn:meofsinglephotons(micropulsephotoncoun:ng)

•  Combiningrangingdistance,fromtravel-:me,withbeampoin:ngandspacecraPposi:ondeterminestheeleva:onofthesurfacealongthebeamprofiles

•  Repea:ngthemeasurementsquan:fiestheratesofchangeineleva:onandthickness

•  TheATLASlaseroperatesat532nm(greenwavelength)•  Penetra:onofthegreenlaserpulsesintoice,snowandwaterwillcausetherangetobebiasedtoolongintroducingerrorsinthesurfaceeleva:onprofiles

•  Thebiasmagnitudesaresensi:vetoseasonalandannualchangesinthesurfacephysicalproper:es

ICESat-2MissionOverview

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•  Theairbornefour-beamSlopeImagingMul:-polariza:onPhoton-coun:ngLidar(SIMPL)isideallysuitedtoquan:fygreenlaserpulsepenetra:ondepthsintosnow,iceandwaterbyopera:ngatgreenandnearinfraredwavelengths

•  Italsodefini:velyiden:fiesthepresenceand,whereshallow,thedepthofmeltpondsandtheloca:onofice-freeseaiceleads

•  NinescienceflightsduringJulyandAugust,2015innorthwestGreenland,totaling37hours,collecteddataforawiderangeofsurfacetypes- Interiordrysnow,coastalicesurfaceswithnumerousmeltponds,mel:ngseaiceandopenocean

•  ConcurrenthyperspectralAVIRISdatawascollectedtoes:matesnowandicecrystalsize,par:culatecontamina:onandwatercontent- Toassesiftheycontrolthedepthofgreenlightpenetra:onmeasuredbySIMPL

•  Forcampaignflightdocumenta:onseeBrunt,K.,T.NeumannandT.Markus,SIMPL/AVIRIS-NGGreenland2015FlightReport,NASA/TM–2015-217544,Oct.2015.

hOp://icesat.gsfc.nasa.gov/icesat2/data/simpl/docs/TM2015-217544.Brunt.pdf•  ForSIMPLcalibra:ondocumenta:onseeHardingetal.,SIMPL_2015_Rel5_Calibra:on_v1.1availableatthesamewebsite.

SlopeImagingMul:-polariza:onPhoton-coun:ngLidar

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Fourbeamswithsurfaceproper3esfrom

8amplitudesperbeam4laser“hotspot”retro-reflectanceand4solarbi-direc3onalreflectanceNolaserNIRpenetra:onsomeasuressurfaceeleva:on:

||1064nmparallel_|_1064nmperpendicularSomelasergreenpenetra:onintosnow,iceandwatersomeasureseleva:onthatisbiasedlow,dependentontheamountanddepthofmul:plescaOering:

||532nmparallel_|_532nmperpendicular

•  ThetransmiOerisan11kHz,1064nmmicropulselaserwith1nsecwide(FWHM),plane-polarizedpulses

•  Apor:onoftheenergyisfrequencydoubledto532nm•  Thesinglelaserbeamisdividedintofourbeamswith

co-aligned1064and532nmpulseenergy•  Thereceiverseparatesthereturnenergyintothetwo

colorsandintopolariza:onsthatareparallel||andperpendicular_|_tothetransmitplane

•  Increasing_|_photonsarecausedbyincreasingsurfaceandvolumemul:plescaOering

•  16singlephotoncoun:ngmodules(SPCM)andevent:merelectronicsareusedto:me-tagthedetec:onofindividualphotonswith0.1nsec(1.5cm)resolu:on

•  Thefourphoton“pointcloud”profilesquan:fyeleva:on,roughnessandslopewithveryhighprecision

•  Thenumberofdetectedlaser-transmiOedphotonsmeasuresthesurface“hotspot”retro-reflectanceintensityat0°phaseangle

•  Thenumberofdetectedsolarbackgroundphotonsmeasuresthesurfacebi-direc:onalreflectanceinthesameviewinggeometryastheretro-reflectance

•  Tradi:onallaseral:metersonlyrecordoneamplitude;laserretro-reflectanceatonewavelength

SIMPL’sMeasurementsCharacterizeSurfaceProper:es

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Polariza:onstaterela:vetotheplane-polarizedtransmitbeam:_|_=perpendicular||=parallel

SIMPL2015BeamGeometryandChannelAssignments

•  SIMPLflightal:tudes,aboveground,typicallyvariedbetween2to3km(6,500to9,500P)•  DuringtheGreenlandflightsonJuly30(DOY211),August3(DOY215)andAugust4(DOY216)Channel7hadanextremelyweaksignalduetoabrokenfiber.Thatwasrepairedforthesubsequentflights.

•  Thebeamdivergenceis130uradbasedonlaboratorybeamprofilemeasurementsofthemicropulselaserusedin2009-2011.Thenewmicropulselaserinstalledfor2015maynothaveexactlythesamebeamdivergence.

•  Theposi:onsofthebeamnumbershavechangedcomparedto2009-2011whenitwas4,3,2,1fromlePtoright

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Channel Mode Extension13 1064_|_ _A_414 1064|| _B_415 532_|_ _C_416 532|| _D_4




flightdirec:on

SpotSepara3on2.35mrad4.7m7.05m

FieldofView233urad0.45m0.0.67m

Divergence:At2kmrange:At3kmrange:

nadirviewofbeamposi3ons:notethattheposi3onsarenotthesameas2011SIMPLdata

3 2 1 4

1/e2SpotSize130urad0.26m0.39m


Horizontalpathrangingcalibra:ontoflattarget,ThuleAirForceBasehanger,July31,2015Theimpulseresponseistheconvolu:onofthelasertransmiOerpulseshapeandreceiverpulsebroadening

SIMPL2015ImpulseResponsePulseShapes

AlaseraPerpulseislocated1.5mfollowingthemainpulse.Itsamplitudeisstrongestrela:vetothemainpulseintheNIRperpendicularchannelsandreducedbyabout50%intheNIRparallelchannels.Itsamplitudeinthe532nmchannelsissignificantlydecreasedbytheprocessoffrequencydoubling.

Beam1 Beam2 Beam3 Beam4

1064_|_

1064||

532_|_

532||

Channel01

02

03

04

05

06

07

08

09

10

11

12

13

14

15

16

aPerpulse

mainpulse


SIMPLCryosphereRemoteSensingCapabili:es(1of2)

SIMPLcharacteris3csforsnowandicelaseral3metry•  Co-incidentGreen532nmandnear-infrared1064nmfootprintsenabledirectcomparisonofthesurfaceeleva:onfromtheNIRsignalphotonsanddepthofpenetra:onfromthegreenvolume-scaOeredsignalphotons

•  Anarrowsystemimpulseresponse(20cmFWHM)and0.1nsechighprecision:ming(1.5cm)achieves8cmrangeprecisionperphotonand~1cmfor100photonsenablehighlyresolvedpenetra:ondepthmeasurements.

•  SIMPLusessmallfootprints(nominally0.3mdiameter)tominimizewithin-footprintpulsebroadeningduetoslopeandroughnessinordertoisolateandquan:fypulsebroadeningduetogreenpenetra:on

•  Thesmallfootprintswithatypicalphotondensityof5to10permeterperchannelenableshighresolu:onmeasurementsofalong-tracksurfaceeleva:on,slope,roughness,penetra:onandphysicalstate

(5to10%channelprobabilityofphotondetec:onperpulse)x(11,000pulsespersec)/(110m/secgroundspeed)

•  Thetotalcross-tracksepara:onofthefourbeamsistypicallybetween13to20m,dependentonal:tude,enablingassessmentofthevariabilityofthesurfaceproper:esattheICESat-2ATLASfootprintscale

•  Thefourbeamsenablemeasurementofcross-tracksurfaceslopeandcurvatureattheATLASfootprintscale•  Thenumberof_|_photonsrela:veto||increasesassurfaceandvolumemul:plescaOeringincreasesprovidinginforma:ononphysicalproper:es(e.g.snowgrainsize,reflectanceandroughness)

•  Thenumberofgreensignalphotonsrela:vetoNIRissensi:vetothephysicalstateofthesurface(e.g.snow,firn,ice,dirtyice)becauseofreflectancedifferencesatthesewavelengths

•  Thenumberofsignalphotons(laser“hotspot”retro-reflectance)rela:vetobackgroundnoisephotons(solarBRDFbi-direc:onalreflectance)issensi:vetoincreasingslope(changingthesolarBRDFincidenceangle)andincreasingroughness(increasingthesolarshadowfrac:on).

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Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC 15

NominalCase•  ||photonsareonlyreturnedfromthesurfacebecauseNIRlightisabsorbedinthesub-surfaceduetowater’sveryhighabsorp:oncoefficient.•  _|_photonsareabsentbecausethewatersurfaceisspecularthusonlysinglescaOeringreflec:onsoccurandnophotonsareconvertedto_|_

state.Averyweaksignalissome:mespresentwhichmaybedueincompletesepara:onof_|_photonsfromthe||signal.•  ||photonsarereflectedfromthesurfaceandalsothewatercolumnduetosinglescaOeringreflec:onsfrompar:culates.ThecolumnscaOering

componentisindicatedbythegreendashedline.TheremaybeboOomreturnifthewaterissufficientlyclearandshallow.•  _|_photonsarenotreflectedfromthespecularsurface.Anincreasingfrac:onofthe||photonsinthewatercolumnareconvertedto_|_as

mul:plescaOeringfrompar:culatesincreases.Like||theremaybea_|_boOomsignal.IftheboOomisglassyspecularicetherewillbenosignal.•  Thedepthof532nmscaOeringandtherateof||vs._|_ex:nc:onisafunc:onofthewaterop:caldepthwhichisdependentonthepar:culate

concentra:on.Clearmeltpondcase•  Becausemeltpondwatercanbeveryclearwithfewpar:culates(dependingonthecontamina:onlevelinthesourcesnowandice)thereoPenis

minimaltonogreenwatercolumnscaOeringcomponent.•  ||willhaveasurfacereturnandaboOomreturnifthewaterissufficientlyclearandshallow.•  _|_willhavenosurfacereturnandnoboOomreturnbecausetherewillbeno_|_photonsgeneratedinthewatercolumntoreflect.Offnadirincidencecase•  Thestrengthofthesurfacereturnsdecreasewithincreasingbeamincidenceangleanddecreasingwind-drivenroughness.Iftheincidenceangleis

largeenoughand/orthesurfaceissmoothenough||and||surfacereturnswillnotbedetectedbecausetheyaredirectedawayforthereceiverbythespecularreflec:on.Asabove,greenwatercolumnandboOomsignalswilldependonthewaterclarityanddepth.

water

ice

1m

3m

1064_|_

1064||

532||

532_|_

6m

airnormalized

laseraPerpulse

laseraPerpulse

boOomreflec:on

SIMPLCryosphereRemoteSensingCapabili:es(2of2)

SIMPLsignalcharacteris3csforwatersurface,columnandbobomlaseral3metry


SIMPLWaterColumnSignalExample

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allsub-surfacescaOeringnospecularsurfacesignalduetohighincidenceangle

duringaircraPturn

laseraPerpulse allsub-surfacescaOeringno_|_surfacereturn

||NIRparallel

||Greenparallel

_|_Greenperpendicular

_|_NIRperpendicular

2011GulfofMexico20kmOff-shoreDeepwatersonoboOomsignal

dashedgreenlineissub-surfacecomponentof||

signalobservedwherethereisnospecularreturn

laseraPerpulsear:fact

solarnoise

surface

surface

PhotonPointCloudProfilesforOneofFourBeams


after pulse

main pulse

1064 _|_ 1064 ||

532 _|_ 532 ||

water and ice volume scattering

laser after pulse no water or ice volume scattering

laser after pulse no water or ice volume scattering

water and ice volume scattering

melt ponds

2015NaresStraitPackIcewithMeltPondNetwork

•  Photonpointcloudsiden:fytheloca:onofmeltpondsbytheabsenceof1064and532perpendicularsurfacereturns

•  532nmpenetra:onintoiceandwaterisseeninthevolumescaOeringbelowthesurfacewherethephotondensityishigherthanthebackgroundnoise

•  Lowsignalstrengthfromtheicefor1064_|_isbecauseNIRmul:plescaOeringisrare•  Stronger532_|_icesignalisbecausegreenmul:plescaOeringismorefrequentduetopenetra:onandhigheralbedo

•  Thehistogramshapesarebroadenedduetosurfacepenetra:on,roughnessandslopeSurfaceslopeisbecauseaircraProlleffectisnotremovedinthisrangedata

Photon point cloud profiles for the 4 channels

after pulse

main pulse

after pulse

main pulse

Photon range histograms for the 4 channels

1064 _|_ 1064 ||

532 _|_ 532 ||

350mlongprofileforBeam417

SIMPLIceandWaterSignalExampleframecameraimage


HorizontalPathRangeandBeamGeometryTes:ngatGoddardFiringatBuilding33CWingRooPopWallandTreesoutGWingPenthouseDoor

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TreeandgreypaintedwalltargetsSIMPLtowall=95m

ViewfromthewallbacktoSIMPL

SIMPLorientedhorizontallyonatripodanddatahandlingelectronics


HorizontalPathRangeandBeamGeometryTes:ngatGoddardFiringatBuilding33CWingRooPopWallandTreesoutGWingPenthouseDoor

45°

95m


HorizontalPathRangeandBeamGeometryTes:ngatGoddardNighameViewofBeamsontheBuilding33CWingWall

•  Beam2greenlaserspotsat95mrangingdistance•  Eightsuccessivephotosshowlaserscin:lla:on•  1/20secondexposure=550laserfiresperphoto

4123

20

flightdirec:on

wallpanelrib wallpanelrib

0.95m


Installa:ononNASALangleyN528NAKingAir

ForkliPing150lbSIMPLtransceiverintoplane

SIMPLinstalledoverop:calportbehindCommandandDataHandlingcomputerrack.

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ElectronicsracksinstalledbehindSIMPL.Eachrackis~160lbs.


MeasurementObjec:vesfor2015SIMPLCampaigninNorthwestGreenland

CampaignteamandNASALangleyKingAiratThule

Abla:onzonetopographyandmeltwaterdistribu:onanddepth

Greenlightpenetra:ondepthisafunc:onofsnowandicegrainsizeandcontaminantconcentra:on

Smoothicesheetandoutletglaciertopography

Openwatergreenlightpenetra:ondepth,icefreeboardandpackicebreakup


SIMPLHDFDataProducts




23



Toplevelh5granulestructure

24

ThegranulestructureissimilartothatusedfortheMABELdatadistribu:on.TheAuxiliaryandimpulsefoldershavebeenaddedforSIMPL-specificdataproducts.


Standardgeolocatedphotonpointcloudsforeachofthe16channelsDelta_:meistheoffsetwithrespecttotheGPSreferencesecondsgivenin/ancillary_data/gps_sec_offset.GPSTime(secondssincethefirstGPSepoch)=delta_:me+gps_sec_offset.TheheightrangeofthephotonsisLandandnear-shoreocean:DEM+1,000mto-500mOcean:±100rela:vetoMSSDesigna:onifthegranuleistreatedaslandorocean,andthesourcefortheDEM,isgivenin/al:metry/dem_drm/dem_flagElev,la:tudeandlongitudearereferencedtotheWGS-84referenceellipsoid,definedbytwoparameters:Semi-majoraxis,a=6378137metersInverseflaOening1/f=298.257223563Photonsinarangewindowfrom200mto5kmbelowtheaircraP(extending~2kmpastthesurface)areavailableinanICESat-2projectarchiveforatmospherestudies(thisdataisnoton-lineandisnotgeolocated)

PhotonFolderContents

25


TransmiberEchoPulse(TEP)impulseresponsephotonpointcloudsforeachofthe16channelsTransmitpulsephotonsaredelayedthroughafiberspoolanddirectedintothereceivertocharacterizetheinstrumentimpulseresponsepulseshapesandrangebiases.Therangewindowextendsfrom25to45mrangewiththeimpulseresponsesat~35m.Thesephotonsarenotgeolocated.Delta_:meistheoffsetwithrespecttotheGPSreferencesecondsgivenin/ancillary_data/gps_sec_offset.GPSTime(secondssincethefirstGPSepoch)=delta_:me+gps_sec_offset.

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ImpulseFolderContents


AuxiliaryFolderContents

Fornormalizingsignalstrengthsbetweenchannels*

RangehistogramsoftheTEPimpulsephotons

ParametersdescribingtheTEPimpulseresponse

Alongtracksignalandnoiseabributes

Alongtrackra3osbetweensignalsandnoise

Laseroutputpower3meseries

Receiverfilterblocktemperature3meseries

Timeoffsetsbetweenchannelsusedingeoloca3on

*ScalefactorsinRelease5aresetto1.

Correctfactorswillbeprovidedwhenthe

amplitudecalibra:oniscompleted.


TEPImpulseHistogramsFolderContents

Star3ngrangeforeachhistogrambinfrom25to45mwith0.015msamplingNumberofphotoncountsineachhistogrambinExamplehistogramshowingthefullrangewindow(top),thesegmentfrom33to38m(boOom)whichcontainstheimpulseresponseandtherangeposi:onsofparametersprovidedintheImpulseResponseFolder

Lasermainpulse

LaseraPerpulse


TEPImpulseResponseFolderContents

Quan3fytheposi3on,shapeandamplitudeoftheaQerpulse

Quan3fytheposi3on,shapeandamplitudeofthemainpulse

Quan3fythebackgroundnoisemeanandstandarddevia3on

Inputparametersusedintheimpulseresponseanalysis

Quan3fythesepara3onofthemainandaQerpulses

Pulseposi:onsandsepara:onsareprovidedforthemode(peak),centroid(mean),andleadingedgethresholdsat10%,50%(halfmax)and80%ofthemodeamplitude.Pulsewidths(leadingtotrailingedge)areprovidedforthethreethresholds.Amplitudesarereportedforthemodesandasprobabili:esofdetec:on(numberofdetectedphotonsabovethenoisemeandividedbythenumberoflaserfires).

Seenextslide

Seenextslide


TEPImpulseResponseFolderContents

Quan3fythemainpulseoffsetsfromthemeanforallgranulescollectedduringaflightforeachofthefiveposi3onparameters.

Parametersareprovidedthatgiveanindica:onofthe:mevariabilityofthemainpulseposi:onduringthecourseofaflight.

Quan3fyalinearfittothemainpulsecentroidposi3onforallgranulescollectedduringaflightandgivethedeparturefromthatfit(thedeltabetweenthegranulescentroidandthelinearfit).


TEPImpulseResponseFolderContentsExampleof:meseriesplotsfortwooftheTEPimpulseresponseparametersshowingmainpulseprobabilityofdetec:onandcentroidrangeforeachofthegranulescollectedduringtheflightonAugust12,2015.Channelswithverylowprobabilityofdetec:on(03,09,15,16)causingnoisyresultsareploOedasverythinlines.

granulestart:me(secondsofday)

Channels

Color=beamThick=NIRThin=GreenSolid=_|_Dashed=||


TEPImpulseResponseFolderContentsExampleoftwoplotsforparametersassociatedwiththelinearfittotheTEPimpulseresponsecentroids.Thetopshowseachgranulesdeparturefromthelinearfit.TheboOomshowstheR^2ofthefits.Channelswithverylowprobabilityofdetec:on(03,09,15,16)causingnoisyresultsareploOedasverythinlines.

granulestart:me(secondsofday)

Channels

Color=beamThick=NIRThin=GreenSolid=_|_Dashed=||


PRNFolderContents

Parametersareprovidedat10Hzthatquan:fylasersignalandsolarbackgroundnoiseamplitudesalongeachbeamprofileusingthemethoddescribedonthefollowingtwoslides.NotethattheSNRisnotastandardformula:on.ItiscomputedasthePDdividedbythenoiserate,notthenumberofsignalphotonsdividedbythenumberofnoisephotons.Theyarecomputedusingtheobservednumberofphotonsinachannel.Theamplitudeshavenotbeencalibratedforinstrumenta:oneffectssothevaluesarenotcomparablebetweenchannels.Scalefactorsforeachchannelwillbeprovidedsothatinstrumentaffectscanberemovedtherebynormalizingthebetweenchannelsignalandnoisestrengths.

Delta_:meistheoffsetinsecondswithrespecttomidnightofthatday.SecondssincethefirstGPSepoch=delta_:me+[604,800sec/weekxstart_gpsweek(in/ancillary_data)]+[86,400sec/dayxdayofweek]DistanceisanapproximatedistancealongtheprofileassuminganominalaircraPgroundspeedof105m/sec.


Theprobabilityofdetec3on(PD)andsignal-to-noisera3o(SNR)arebasedonsurfacesignalphotons•  Themethoddoesnotclassifyeachphoton

Thesurfaceisdefinedbasedonmaximumphotondensity•  SurfaceistrackedusingChannel2andthenappliedtoallchannels

Channel2isNIRParallelBeam1whichusuallyhasthehighestSNR•  The“surface”isthebinwiththemaximumnumberofphotons(max_range_bin)•  Binsare0.1secondsindura:on(frame)by15minrangeforsnow,iceandwater(2009and2015)and45mfornon-arc:clandtohandlesteeptopography,buildingsand/ortallvegeta:on(2010and2011data)

Theframelengthis~11m,dependentongroundspeed(nominally100to120m/sec)•  Max_range_bincanbenoise,adensecloudtoporthetruesurface.Ifitisnoisethemax_range_binwillrandomlyappearanywhereinthesearchwindowwhichextendsfrom200mbelowtheplanetotheendoftheacquisi:onwindow(13kmin2009-2011)ortotheendofapost-processinggatedwindow(5kmin2015).

•  Surfacetrackingini:a:onbeginsatthestartofagranuleanddetermineswhenmax_range_biniscon:nuousfor50frames(~0.5km).Con:nuityisdefinedasthemaxrangebinbeingwithin±3binsofthemaxbinintheprecedingframefor15mbinsand±2for45mbins

Ini:a:oncanstartonacloudtopifdensecloudsoccuratthestartofthegranulewithinthesearchwindow•  Once50con:nuousframesareiden:fiedthenthetrackingframebyframeproceedsstar:ngwiththemax_binmodeforthe50frames.

•  ThesignalusedtocomputePDandSNRisthesumofphotonsinthemax_range_binandthebinsthatare1aboveand1belowmax_range_bininthesameframe,withthesolarbackgroundnoisephotonsperbininthatframesubtractedfromeach

Noisephotonsperbinistheaverageofa30binwindowthatstops100binsfromtheendofthedatawindowThenoiserateisthenumberofnoisephotonspersecondinunitsofmHz.ThePDisthenumberofsignalphotons,inboththemainandaPerpulses,dividedbythenumberoflaserfiresin0.1secassuminganominallaserfirerateof11.4kHz.ThePDandnoiseratearecomputedat10Hzthensmoothedusingarunning5binaveragingwindow.TheSNRisanon-standardcomputa:onequaltothePDdividedbythenoiserate.Itisnotthenumberofsignalphotonsdividedbythenumberofnoisephotons.

PRNSta:s:csComputedUsingaBasicSurfaceTrackingAlgorithm

34


Trackingisresetwhenmax_range_binsurfacecon3nuityfails•  Surfacetrackingcanfail(max_range_binchangeexceedsthe±3or±2binlimit)

•  poin:ngatlargeanglesoverspecularsmoothwaterorice(turns;roll&pitch)•  rangingthroughclouds•  surfaceveryabruptlychangeseleva:on•  aircraPveryabruptlymaneuvers(rolland/oral:tude;unlikely)

•  Wheresurfacecon:nuityislostthelastmax_range_binisprojectedataconstantrangefor8frames(~90m),tes:ngforcon:nuityateachframe

•  Ifcon:nuityfailsforthe8framesthetrackingini:a:onisrestarted•  Theresetcancausethe“surface”tojumpfromthetruesurfacetoadensecloudtoporfromacloudtoptothetruesurface

•  AllPRNandPRNRresultsareinvalidforframeswheremax_range_binisnotthetruesurface•  Thereisnoflagontheproducttoiden:fyframesthatarenotthetruesurface

Itisdifficulttobecertaingiventhevarietyofmax_range_binpaOernsthatcanoccur•  Examina:onofmax_range_binprofilescanprovideinsightintowhenthetruesurfaceislostascanoutliersintheprobability_detec:on,noise_rateandSNRvalues

Thresholdeditscouldbeappliedtoanyofthesevaluestoexcludenon-surfaceframes

AlgorithmMethodwhenSurfaceTrackingisLost

35


Beam3532_|_and||areswappedduetodatalabelingerror.Correctedinreleaseddata.

PDGoal10%4%

_|_

_|_

||

||

B

AC

BD

August12,2015Abla:onZone~7,500PAGL

55°doublertemp1.3mingranule

15:07:20

GreenlandAbla:onZoneProbabilityofDetec:onExamplefromPRNFolderSampledat10Hz(~11m);Smoothedwithrunning5binaverage(~55m)

FrameCameraPhoto

36

ItemsofNote:•  UniformPD’soveruniformsurface

•  Sourceofgreenspikesnotknown

•  Green_|_~equalto||duetosignificantmul:plescaOering

bright&penetra:on•  NIR_|_lowcomparedto||duetominimalmul:plescaOering

darker&nopenetra:on


GreenlandAbla:onZoneProbabilityofDetec:onandNoiseRatefromPRNFolder

1064_|_ 1064|| 532||

pondsurfaceandlaseraPerpulseechoicesurfaceonpondmargins

boOomboOom

ver:calgapsareprocessingerrorwhichhasbeencorrected

photonpointcloud

laserretro-reflectance

solarbi-direc3onalreflectance

NWGreenlandcoastalabla3onzonemeltpond;framecameraimage

solarbackgroundphotons

darkwatersurfacedarkwatersurface

verysmallsignal

boOomsignalisafunc:onofwaterdepth

surface+boOomsignals

water=iceiscoincidence

watersurfacelasersignalstrengthsareafunc:onofroughnessandbeamincidenceangle

NoiseRate

(mHz

)Prob

abilityof

Detec:on

Ra

nge(m

)

532_|_notshownbecausemeltwaterissoclearthereisnocolumnvolumescaOering.AlsotheboOomsignalisabsentperhapsbecauseitssurfaceis

glassyandspecular.

PDandnoiseratearecomputedat10Hz(~10m)andsmoothedwithrunning

5binaverage

4kmlongframecameraimagecomposite

37


Green|| S+V S+V <S+V S+V S+V S+V S+V S+V

Green_|_ V S+V V S+V V S+V V S+V

NIR|| S S <S S S S S S

NIR_|_ S S S S

Varia:onsinLaserRetro-reflectanceSignalStrengthsareSensi:vetoScaOeringProper:es2009LakeErieIceCoverandOpenWaterPhotonPointClouds

roughniasice

greywhiteice

specularskimice

roughopenwater

greywhiteice

greywhiteice

260m

||

_|_

||

_|_

greywhiteice

specularskimice

laseraQer-pulse

laseraQer-pulse

laseraQer-pulse

laseraQer-pulse

S = surface scattering. V = volume scattering. Increased _|_ signal is caused by increased multiple scattering. The non-normal incidence angle to the smooth specular skim ice causes most surface scattering to be reflected away from the

receiver. More surface signal is reflected to the receiver from the wind-roughened specular open water. Aircraft roll effects on range not removed. After pulse strength in 2015 is smaller than in this 2009 data.

38





NIR_|_ S S S S


receiver. More surface signal is reflected to the receiver from the wind-roughened specular open water. These PD values, using the sum of main pulse and after pulse photons, are computed at 10 Hz then smoothed to 2 Hz.

260m

||

_|_

||

_|_

roughniasice

greywhiteice

specularskimice

roughopenwater

greywhiteice

greywhiteice

greywhiteice

roughopenwater

39

Varia:onsinLaserRetro-reflectanceSignalStrengthsareSensi:vetoScaOeringProper:es2009LakeErieIceCoverandOpenWaterProbabili:esofDetec:on


PRNRFolderContentsRa:osbetweenPRNparametersareprovidedthatprovideinforma:onaboutsurfacereflectanceandlightscaOeringproper:es.•  Ra:osintheDepolariza:onfolderareequaltothenumberof

perpendicularphotonsdividedbytheparallelphotons.Forthelasersignalphotons(PDra:os)itisameasureoftheamountofsurfaceandvolumemul:plescaOering.Forthesolarbackgroundnoiserate(NRra:os)itisameasureofthedegreetowhichrandomlypolarizedsunlightispolarizedbyreflectancefromspecularsurfaces.

•  Ra:osintheSolarfolderareequaltothesignalphotonPD(laser“hotspot”retro-reflectance)dividedbythebackgroundnoiserate(solarbi-direc:onalreflectance).Thesearesensi:vetoincreasingslope(changingthesolarincidenceangle)andincreasingroughness(increasingthesolarshadowfrac:on).

•  Ra:osintheWavelengthfolderareequaltothenumberofnearinfraredphotonsdividedbythenumberofgreenphotons,forboththelaserPDandsolarNR.Theyaresensi:vetothecomposi:onofthesurface(e.g.snow,firn,ice,dirtyice)becauseofwavelength-dependentreflectancedifferences.

Delta_:meistheoffsetinsecondswithrespecttomidnightofthatday.SecondssincethefirstGPSepoch=delta_:me+[604,800sec/weekxstart_gpsweek(in/ancillary_data)]+[86,400sec/dayxdayofweek]

DistanceisanapproximatedistancealongtheprofileassuminganominalaircraPgroundspeedof105m/sec.


260m

_|_/||

_|_/||

roughniasice

greywhiteice

specularskimice

roughopenwater

greywhiteice

greywhiteice

greywhiteice

specularskimice




NIR_|_ S S S S


receiver. More surface signal is reflected to the receiver from the wind-roughened specular open water. These ratios, using the sum of main pulse and after pulse photons, are computed using the smoothed 2 Hz PD values.

41

Varia:onsinLaserRetro-reflectanceSignalStrengthsareSensi:vetoScaOeringProper:es2009LakeErieIceCoverandOpenWaterDepolariza:onRa:os


AuxiliaryFolderContents

Twoinstrumentstatusparametersweremonitoredthroughthedura:onofeachflight.Theymayprovideconstraintsforfuturemodelingofinstrumentperformance.

Laseroutputpower3meseries

Receiverfilterblocktemperature3meseries

These:meseriesarefortheen:reflight,notjustthepor:onassociatedwithanindividualgranule.Thedelta_:meisgivenastheelapsedsecondssincethefirstdatapointinthegranule.Thereforepowerandthermal:mesthatoccurbeforethestartofthegranulewillbenega:venumbers.Delta_:meistheoffsetwithrespecttotheGPSreferencesecondsgivenin/ancillary_data/gps_sec_offset.GPSTime(secondssincethefirstGPSepoch)=delta_:me+gps_sec_offset.


Featuresofnote:•  Posi:vecorrela:onbetweenNIRandGreenTxpowersbutlessconsistentthanexpected.Needtoassesswhy.

•  Filterblocktemperaturedoesnotstabilize;notexpected.On-offdeadbandswitchnotworking?Needtoassesseffectonreceiverthroughput.

Rapidpowerchangesandextendingtozeroarenotunderstood.Inves3ga3onunderwayonthis.

InstrumentMonitoringforSignalAmplitudeCalibra:onLasertransmitpowersandreceiverspectralfilterblocktemperatures

43


SIMPLInstrumentDescrip:on




44



TransceiverInstrumentDesign

20cmSharedPrimaryMirror

SIMPLusesanoff-axisparabolaop:caldesignwiththetransmiOerandreceiversharingtheop:calbenchandprimaryandsecondarymirrors.Thisdesignprovides:

•  stablelaserfootprinttoreceiverfieldofviewalignment•  co-alignedNIRandgreentransmitbeams•  co-incidentNIRandgreenfootprints

45

SIMPLop:calbenchinsideitsmoun:ngframe(gold)installedintheLangleyKingAir.Theinstrumentis

fullyenclosedwithpanelsduringopera:on.

Receiverontopofbench

20cmSharedPrimaryMirror

SecondaryMirror

80cmSharedOp3calBenchTransmibersetinsidebench

ReceivedEnergy

TransmitBeams


TransmiOerComponentsandOp:calPath

SIMPLu:lizesa1064nmTeemPhotonics(modelSNP-08E-OEM)microchiplaserthatispassivelyQ-switchedwithapulserepe::onfrequency(PRF)at~11kHzand~6µJofoutputpulseenergy.Thepulsehasawidthof1nsecFWHMandaGaussianbeamprofile.Usingbeamshapinglensesthe1064nmoutputpulsesarefocusedintoasecondharmonicfrequencydoublingcrystalinwhichapor:onofthetransmitenergyisconvertedto532nm.Temperaturecontrolofthecrystaldeterminesdoublingefficiencydefiningthepropor:onalamountof164nmand532nmpower.Theminimumandmaximumsetpointof35°Cand65°Ccorrespondto38%and15%conversionefficiency,respec:vely.AdichroicbeamspliOerdividesthetwocolorsintoseparateop:calpathsthatbeginwithbeamshapinglensestoestablishthebeamdivergence.LaboratorymeasurementsusingtheoriginalSIMPLlaserdeterminedthedivergencewas130uradforbothcolors.Anewmicrochiplaserwasusedduringthe2015Greenlandcampaign.Thatbeamdivergencehasnotbeenmeasuredyetandcoulddiffer.APerthebeamshapinglensesapor:onoftheenergyoneachpathisreflectedver:callyandexitsthetransmiOerenclosurethroughthreeapertures.Thislighttriggersthestartpulsedetector,isusedforimpulseresponsepulseshapemeasurementsandtomonitortheoutputlaserpower.Oneachop:calpathasequenceofwaveplatesandbirefringentcalcitecrystalsproducefourbeamswhichallhavethesamepolariza:onplane.Thefirstquarterwaveplatecircularizestheplanepolarizedtransmitbeamwhichisthensplitbythefirstcalcitecrystalintoparallelandperpendicularcomponentsformingtwobeams.Thephysicalsepara:onofthebeamsisdefinedbythecalcitecrystallength.Thesecondquarterwaveplatecircularizesthosebeamsandthenthesecond,shortercalcitecrystalsplitsthetwobeamsintothetwopolariza:oncomponents,formingfourbeams.Thehalfwaveplaterotatestwoofthebeamspolariza:onplanesby90°sothatallbeamshavethesamepolariza:onplaneorientedperpendiculartotheop:calbench.Aseconddichroicbeamop:crecombinesthetwocolorsandprecisionalignmentoftheop:calcomponentsproducesco-aligned1064nmand532nmbeams.Anega:velensarrayestablishesthe2.1mradbeam-to-beamdivergence.ApolarizingbeamspliOerisusedasafinalsteptoensure≥100:1plane-parallelpolariza:onpurity.AnthonyYuatGoddardSpaceFlightCenterdesignedandimplementedthelasertransmiOer.

46


polarizingbeamspliOer

secondarymirror

transmiOerfoldingmirror

FoldingMirrorsandOp:calPath

APerpassingthroughthepolarizingbeamspliOerthetransmitbeamsreflectoffofasmallfoldingmirror.Thefoldingmirrordirectsthebeamsperpendicularlytothesecondarymirrorwhichreflectsthebeamstothe20cmdiameterprimarymirror.Thatmirrorreflectsthebeamsatnadirtothesurface.Uponexitfromtheinstrumentthebeamsareoverlappingwithacombineddiameterof70mmand5mmbeam-to-beamsepara:on.TheNominalOcularHazardDistanceofthecombinedbeamsandcolorsis0mandisthereforeeyesafe.Thedivergingbeamsbecomefullyseparatedatadistanceof23m.

entrancetoreceiverfoldingmirrorassembly

47

toprimarymirror

foldingmirror

assembly

pin-holefieldstop

Uponentryintotheinstrument’s20cmapertureasmallpor:onofthereturnedlaserenergyisblockedbythebackofthesecondarymirrorassembly.Theremainingenergyisreflectedbytheprimarymirrortothesecondarymirrorwhereitreflectsperpendicularlytotheop:calbench.Apor:onofthelightisinterceptedbythetransmitfoldingmirrorandisback-reflectedintothetransmiOerop:csbutthesignalstrengthistooweaktoeffectthelaserperformance.Themajorityofthelightpassesthroughaholeintheop:calbenchandentersafoldingmirrorassemblythatreflectsthelight90°sothatthepathisparalleltotheop:calbench.Thebeamsaredirectedtoapin-holefieldstop.


TransmitEchoPulse,StartPulseDetectorandPowerMeter

48

beamspliOercube

532nmcollec:on

lens

startpulse

detector

532nmpowermeter

input

532nmprojec:on

lens

1064nmprojec:on

lens

secondarymirror

transmiOerturningmirror

Thelaserpulseenergydirectedver:callyoutofthetransmiOerenclosurethroughthreeaperturesisusedforthreepurposes.Lightentersastartpulsedetectortoprovidepulseeventstothereceiverelectronicsthatareusedasthestar:ng:meofthephotonround-triptravel:memeasurement.ForeachwavelengthlightentersabeamspliOercubethatdirectspartofthelighttoaTransmitEchoPulse(TEP)collec:onlensandtheremaindertoapowermeter.TheTEPop:csareusedtorecordtheinstrumentimpulseresponsepulseshapewhichistheconvolu:onofthetransmitpulseshapeandthereceiverpulsebroadening.Fiberstransmitthetwocolorsthroughcouplersto38mfiberspoolswhichdelaythepulsestoseparatethemin:mefrominternalscaOeredlightsignals.Thedelayfibersarecoupledtofibersthattransmitthepulsestoprojec:onlensesthatdispersethelightontotheprimarymirror.Thislightfollowsthereceivepathtorecordtheimpulseresponsesusingthesameop:csandelectronicsasthepulsesreflectedfromthesurface.Deconvolu:onoftheimpulseresponsefromthesurfacereturnprovidesameasureofpulsebroadeningduetosurfaceroughness,slopeandpenetra:on.Theotherpor:onofthelightdividedbythebeamspliOerisdirectedtoaThorlabpowermeterthatrecordstransmitpowervariabilityat532nmand1064nm.AnthonyYuatGoddardSpaceFlightCenterdesignedandimplementedtheTEPop:calassemblies.

532nmand1064nmfiberspoolstodelayTEP


ReceiverComponentsandOp:calPath

Thefieldstopconsistsoffourpinholesthatdefinea233uradfieldofviewforeachbeam.ThesmallFOVsareusedtospa:allyrejectsolarbackgroundphotons.AlensarrayfollowsthatcollimatestheincomingbeamsandadichroicbeamspliOerdividesthetwocolorsintoseparateop:calpaths.OneachpathadoublestackofpolarizingbeamspliOercubesseparatesthereturnenergyintophotonswithpolariza:onstatesthatareparallelandperpendiculartotheplane-parallelpolarizedtransmitbeams.Thefourcolor+polariza:onmodeseachpassthroughamechanicaliristhatcanbeusedtoaOenuatethebeamenergy(theiriseswerenotinstalledonthebenchatthe:meofthephoto;insetshavebeenaddedtoshowtheirloca:on).Eachirisopeningsizeissetindependently.AstheyareclosedtheaOenuatetheouterbeamsmorerapidlythentheinnerbeams.Theirisesweresettobefullyopenforall2015flights.Lensarrayassembliesforeachofthefourmodesfocusthebeamsintofourfiberswhichhavea0.22numericalapertureand100micronsteppedindexcoresize.Usingaspooltoreducebendingthefibersarecoupledto1064nmand532nmfilterblockseachofwhichconsistofeightnarrow-bandspectralfilterassembliestorejectout-of-bandsolarbackgroundphotons.Thefilterassembliesaretemperaturecontrolledwithdead-bandheaterstomaintainstablebandpasswavelengths.Twothermistorsareinstalledoneachblocktorecordthetemperaturesattwoloca:onsusingafour-channelHobodatalogger.One1064nmblockthermistorwasnotopera:ngduring2015.Thedatashowedthattheblocktemperaturesslowlyincreasedthroughoutthedura:onoftheflightsratherthanbeingstabilizedataconstanttemperature.Thecauseisnotknown.What,ifany,impactthenon-constanttemperaturehadonreceiverthroughputisnotknownandwillbeevaluated.Onexitfromthefilterblocks16fibers,whichhavea0.37numericalapertureand200micronsteppedindexcoresize,transmitthesignalstofoursingle-photon-coun:ng-module(SPCM)quaddetectorsinanadjacentinstrumentrack.Thefoursignalsforabeamaredirectedtooneofthequaddetectormodules.YunhuiZhengandTimHussatSigmaSpaceCorp.weretheleadop:calandmechanicalengineerswhodesignedandintegratedthereceiverunderthedirec:onofPhilipDabneyatGoddardSpaceFlightCenter,theSIMPLinstrumentscien:standsystemengineer.

49

532 nm filter block

1064 nm filter block

turning mirror

fiber spool

532 perpendicular

532 parallel

1064 parallel

1064 perpendicular

dichroic beam splitter

aperture iris

dual-cube polarizing beam

splitter

laser transmit plane perpendicular to

optical bench

pinhole array

lens array

lens arrays

mirror

parallel and perpendicular

receive photons


ElectronicsRack

The19inchwide,half-heightelectronicsrackisinstalledbehindtheSIMPLtransceiver.TherackhousesanenclosurecontainingthefourSPCMquaddetectorassemblieswhicharesiliconavalanche-photodiode(SI:APD)devicesmanufacturedbyIntevac.TheSPCMdetec:onquantumefficiencyisintherange50to60%at532nmand1.6to2.3%at1064nm.TheIntevacSPCMsweretheonlyphotoncoun:ngdetectorsavailableatthe:meofSIMPL’sdevelopmentwithsensi:vityintheNIRsotheirusewasrequired.Eachdetectorinanassemblyreceivessignalsfromoneofthefourchannelsonabeam.Upondetec:onofaphotonthedetectorsgenerateanelectricalpulsethatistransmiOedtofourP7889event:merinterfaceboardsinthecommandanddatahandlingrack.Theelectronicsrackalsohousesapowersupplyenclosure,LightwavelaserpowermeterandaThorlabdoublingcrystaltemperaturecontroller.Themaximumandminimumconversionefficienciesusedwere38%and15%,at35°Cand65°C,respec:vely.Intermediatetemperatureswerealsoused.Thereisno-inflightknowledgeofthesurfacereturnPD.DoublertemperatureandaircraPal:tudewereplannedpre-flightbasedonthenominalNIRandgreenreflectancesofthetargetsurfaceswiththegoalofachievingPDsintherange4%to10%.Thiswasthegoalinordertohaveanadequatedensityofreturnphotonswhilenotintroducingalargefirstphotonrangebiasduetodetectorsatura:on.ThepowersupplyenclosurecontainsthreeDCpowersupplies(AcopianGoldBoxHighPerformancelinearAC-DC),alaserfirestart-pulsediscriminator,twoASRCFederaltransistor–transistorlogic(TTL)fan-outboardsandfrontpanelmountedvoltageandcurrentmeters.Thediscriminatortakesasinputthesignalfromthelaserfirestartpulsedetector.Onefan-outboardtakesthisdiscriminatoroutputandproducesduplicatelaserfirepulsesthatgotothefourindividualP7889boards.Theotherfan-outboarddistributestheGPS1pulsepersecondsignaltothefourinterfaceboards.PhilipDabneyandKurtRushatGoddardSpaceFlightCenterdesignedandintegratedtheelectronics.

50

front rear

SPCMdetectorenclosure

powersupply

enclosure

Frequencydoublertemperaturecontroller

powersupply

enclosure

laserpowermeter


CommandandDataHandlingRack

The19inchwide,half-heightcommandanddatahandling(C&DH)rackisinstalledinfrontoftheSIMPLtransceiver.TherackhousestheenclosurethatcontainsfourP7889event:merinterfaceboards.Eachboard:mesthearrivalofthelaserfirestartpulses,theGPSoncepersecondpulses(fromtheTTLfan-outboards)andthedetectedphotonpulseswith0.1nsec(1.5cm)resolu:on.Eachboard:mesthephotoneventsforthefourchannelsonabeam(1064nmparallelandperpendicularand532nmparallelandperpendicular).Therela:vearrival:mesofalleventsarerecordedbasedontheCPUclockfrequency.Absolute:meisrecordedforthestartandendofeachfiletakenfromtheCPUclockwhichissynchedtoGPS:meusingatotallyaccurateclockwhichreceivesinputfromadual-frequencyGPSantennaemountedonthetopoftheaircraPfuselage.Thecomputerissuescommandstotheinstrumenta:onandstorestheeventarrival:mesonRAIDdrives.TherackalsohousestheCPUkeyboardandscreenandthelasercontrollerandpowersupply.ALenovaWindowslaptopinstalledonthetopoftherackisusedtoruntheApplanixPosAVandpowermetersoPware.Italsorecordstheframecameraimages.SusanValeOatGoddardSpaceFlightCenter,theSIMPLsoPwareengineer,developedtheinterfacetotheP7889cards,theflightcontrolanddatacollec:onsoPwareandthegroundprocessingsoPware.ElizabethTimmonsatGoddardSpaceFlightCenterintegratedthelaptopandassociatedsoPware.

51

front

SPCMdetectorenclosure

powersupply

enclosure

P7889event:merInterfaceboards

enclosure

customC&DHcomputerandRAIDdrives

LasercontrollerandpowersupplyandGPStotallyaccurateclock(TAC)andcontroller

front





52

AncillaryData:Applanix,FrameCameraandHyperspectralData



FlownonNASALangleyKingAirwithSIMPLApplanixPOS/AV610IMU+GPS RecordedSIMPLposi:onandaatudedatausedingeoloca:on MountedadjacenttoSIMPLusingsameseattrackrailsforstablealignment ProvidedandinstalledbyNASAAmesResearchCenter Nadirframecamera ThorlabsDCU223CcolorCCDCamera,1024x768Resolu:on FujiPhotoOp:calCo.Lens678437,1:1.4/50 ImagetakenonceasecondcontrolledbyGPStosynchwithSIMPL AOachedtoSIMPLmoun:ngframeforstablealignment Secondoblique-anglecameraforstereoimaginginstalledbutnotused(FOVblocked)TwoASDFieldSpec4Spectroradiometerprofilers–ChrisCrawford,GSFC Fiber-couplednadirandzenithviewingwith1°andcosinereflectorfore-op:cs,respec:vely Nadirop:caOachedtoSIMPLmoun:ngframeforstablealignment

FlownonDynamicAvia:onKingAirJPLAVIRIS-NGHyperspectralImager–RobGreen,PI

Flownathigheral:tudethanSIMPL FollowedLangleyKingAirflightpathtrailingby15to20min

AncillaryInstrumenta:on

nadircamera

lens

ASDnadirop:c

AVIRIS

RobGreen


NadirColorCamera

54

Camera1680horizontalpixels;1200ver:calpixelsPixelSize4.40E-06mChipsize-V5.28E-03m;W7.39E-03mLensFocallength=5.00E-02mFOV–V=1.06E-01radians;6.04E+00degFOV–W=1.48E-01radians;8.46E+00degAtnominal2,500mflightal:tudeFramesize–V=264mFramesize–W=372mAtnominal100m/secgroundspeedFrame0verlap–V=2.6xResolu:on~0.5m0.2mpixelwithcolorre-samplingblurandop:csMTFV=in-trackW=cross-track

•  ThorlabsDCU223CcolorCCDCamera •  FujiPhotoOp:calCo.Lens678437,1:1.4/50•  Imagetakenonceasecond•  AOachedtoSIMPLmoun:ngframeforstablealignment•  Filenameis:mesynchedusingGPS1PPS

AllJulyflightsEDTlocal3me=GPS–4hr;resetforAugustflightstoGPS–0hr

Laserfootprintsarewithintheframebutloca:onvarieswithal:tudebecausethecameraandlenswerenotbore-sighted.Canbeestablishedusingal:metryprofilematchingtoimagefeatures.

SIMPL18mbeamspreadat2,500m

W=372mat2,500m


16:58:24

17:10:36

17:26:17

~17:20:00

August4,2015

Twopoten:alsourcesofconfusion:•  AVIRISKingAirtrailedSIMPLKingAirbyabout15to20minutes.

•  SIMPLKingAirsome:mesmadeturnstocrossovermelt-pondswhileKingAirflewstraight

AVIRIS

FrameCameramountedinsideSIMPL

FlightDirec:on

LAND_ICE_SH11_SH12QuickLookhOps://avirisng.jpl.nasa.gov/cgi/flights.cgi?step=view_all_flights

AVIRISvs.FrameCameraComparison

55

Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC56

Representa:veFrameCameraImagesMel:ngPackIceinNaresStrait

~0.4kmal:tude

dependent

HighEleva:onInteriorAccumula:onZone

LowEleva:onCoastalAbla:onZone

InteriorandcostalimagesarebrightnessandcontrastenhancedtoemphasizesurfacefeaturesCirculardarkblotchinlowerrightisdustspeckoninsideoflens(cleanedoffforlaterflights)


Sequen:alFrameCameraImages

~0.3kmal:tude

dependent

TarmacPassinfrontofThuleHangers

Imagesarebrightnessandcontrastenhancedtoemphasizesurfacefeatures

SeaIceNorthofEllesmere,August7,2015 Flightwasmostlycloudybelowtheplaneandat:meswatercondensedonwindowexterior(nosurfacesignal)withrareviewsofsurface(weaksignal).Alsocloudyaboveplanesosolarillumina:onwasweakanddiffuse.


SIDEVIEW

Op:calport

forward

SIMPL–HyperspectralASD–CameraBoresightTestinThuleHanger

Framecamera

SIMPLaperture

ASDop:calhead

NADIRVIEWINSIDEPLANE

•  Loca:onofmaximumASDsignalfromback-projectedLED

•  LEDpoin:ngorientedtomaximizebrightnessincameraimagetoalignFOVaxes

•  SIMPLlaserspots(green)areattrailingedgeofASDop:c1°FOV(yellow;45m@2,500m)

•  Forwardflightensuresthetwotrackssamplethesameprofile

50mtotarget

forward

Op:calPort

Mirror@45°Laserspots(indicatedbygreencircles)inthenear-fieldarelargerela:vetotheirspacingcomparedtoontheground

FrameCameraImage

20m

HORIZONTALVIEWTOTARGET

forward

45m

58


References




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simpl greenland 2015 campaign - icesat-2 · kurt rush, electronics engineer lead beth timmons,...

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