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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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Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC
TableofContents
Release5ProductChangesandLimita:ons 3CampaignOverview 7SIMPLDataProducts 23SIMPLInstrumentDescrip:on 44AncillaryData:Applanix,CameraandHyperspectral 52References 59
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SIMPLGreenland2015Campaign
G O D D A R D S P A C E F L I G H T C E N T E R
March30,2016DocumentVersion1.1
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Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC
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.
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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.
Release5ProductImprovementsandLimita:ons:2of3
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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.
Release5ProductImprovementsandLimita:ons:2of3
6
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
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CampaignOverview
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SIMPLGreenland2015Campaign
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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SIMPL2015GreenlandCampaignTeam
8
FromlePtorightGoddardSIMPLTeam:
AnthonyYu,SusanValeO,PhilipDabney,DavidHarding,BethTimmonsandKurtRushAmesApplanixInstalla3onandProcessing:
DennisGearhart,JamesJacobsonGoddardICESat-2ProjectScienceOffice:
KellyBrunt,KaitlinWalshGoddardASDProfilingSpectrometer(notshown):
ChrisCrawfordNASALangleyAircraQOpera3ons(notshown):
RickYasky,MikeWusk,AndyHaynes,DavePerez,SeanDeRubba
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• 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
12
Channel Mode Extension13 1064_|_ _A_414 1064|| _B_415 532_|_ _C_416 532|| _D_4
Channel Mode Extension9 1064_|_ _A_310 1064|| _B_311 532_|_ _C_312 532|| _D_3
Channel Mode Extension5 1064_|_ _A_26 1064|| _B_27 532_|_ _C_28 532|| _D_2
Channel Mode Extension1 1064_|_ _A_12 1064|| _B_13 532_|_ _C_14 532|| _D_1
flightdirec:on
SpotSepara3on2.35mrad4.7m7.05m
FieldofView233urad0.45m0.0.67m
Divergence:At2kmrange:At3kmrange:
nadirviewofbeamposi3ons:notethattheposi3onsarenotthesameas2011SIMPLdata
3 2 1 4
1/e2SpotSize130urad0.26m0.39m
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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
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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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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
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SIMPLWaterColumnSignalExample
16
allsub-surfacescaOeringnospecularsurfacesignalduetohighincidenceangle
duringaircraPturn
laseraPerpulse allsub-surfacescaOeringno_|_surfacereturn
||NIRparallel
||Greenparallel
_|_Greenperpendicular
_|_NIRperpendicular
2011GulfofMexico20kmOff-shoreDeepwatersonoboOomsignal
dashedgreenlineissub-surfacecomponentof||
signalobservedwherethereisnospecularreturn
laseraPerpulsear:fact
solarnoise
surface
surface
PhotonPointCloudProfilesforOneofFourBeams
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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
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HorizontalPathRangeandBeamGeometryTes:ngatGoddardFiringatBuilding33CWingRooPopWallandTreesoutGWingPenthouseDoor
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TreeandgreypaintedwalltargetsSIMPLtowall=95m
ViewfromthewallbacktoSIMPL
SIMPLorientedhorizontallyonatripodanddatahandlingelectronics
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HorizontalPathRangeandBeamGeometryTes:ngatGoddardFiringatBuilding33CWingRooPopWallandTreesoutGWingPenthouseDoor
45°
95m
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HorizontalPathRangeandBeamGeometryTes:ngatGoddardNighameViewofBeamsontheBuilding33CWingWall
• Beam2greenlaserspotsat95mrangingdistance• Eightsuccessivephotosshowlaserscin:lla:on• 1/20secondexposure=550laserfiresperphoto
4123
20
flightdirec:on
wallpanelrib wallpanelrib
0.95m
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Installa:ononNASALangleyN528NAKingAir
ForkliPing150lbSIMPLtransceiverintoplane
SIMPLinstalledoverop:calportbehindCommandandDataHandlingcomputerrack.
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ElectronicsracksinstalledbehindSIMPL.Eachrackis~160lbs.
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MeasurementObjec:vesfor2015SIMPLCampaigninNorthwestGreenland
CampaignteamandNASALangleyKingAiratThule
Abla:onzonetopographyandmeltwaterdistribu:onanddepth
Greenlightpenetra:ondepthisafunc:onofsnowandicegrainsizeandcontaminantconcentra:on
Smoothicesheetandoutletglaciertopography
Openwatergreenlightpenetra:ondepth,icefreeboardandpackicebreakup
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SIMPLHDFDataProducts
SIMPLGreenland2015Campaign
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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March30,2016DocumentVersion1.1
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Toplevelh5granulestructure
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ThegranulestructureissimilartothatusedfortheMABELdatadistribu:on.TheAuxiliaryandimpulsefoldershavebeenaddedforSIMPL-specificdataproducts.
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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
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TransmiberEchoPulse(TEP)impulseresponsephotonpointcloudsforeachofthe16channelsTransmitpulsephotonsaredelayedthroughafiberspoolanddirectedintothereceivertocharacterizetheinstrumentimpulseresponsepulseshapesandrangebiases.Therangewindowextendsfrom25to45mrangewiththeimpulseresponsesat~35m.Thesephotonsarenotgeolocated.Delta_:meistheoffsetwithrespecttotheGPSreferencesecondsgivenin/ancillary_data/gps_sec_offset.GPSTime(secondssincethefirstGPSepoch)=delta_:me+gps_sec_offset.
26
ImpulseFolderContents
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Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC
AuxiliaryFolderContents
Fornormalizingsignalstrengthsbetweenchannels*
RangehistogramsoftheTEPimpulsephotons
ParametersdescribingtheTEPimpulseresponse
Alongtracksignalandnoiseabributes
Alongtrackra3osbetweensignalsandnoise
Laseroutputpower3meseries
Receiverfilterblocktemperature3meseries
Timeoffsetsbetweenchannelsusedingeoloca3on
*ScalefactorsinRelease5aresetto1.
Correctfactorswillbeprovidedwhenthe
amplitudecalibra:oniscompleted.
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TEPImpulseHistogramsFolderContents
Star3ngrangeforeachhistogrambinfrom25to45mwith0.015msamplingNumberofphotoncountsineachhistogrambinExamplehistogramshowingthefullrangewindow(top),thesegmentfrom33to38m(boOom)whichcontainstheimpulseresponseandtherangeposi:onsofparametersprovidedintheImpulseResponseFolder
Lasermainpulse
LaseraPerpulse
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Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC
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
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Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC
TEPImpulseResponseFolderContents
Quan3fythemainpulseoffsetsfromthemeanforallgranulescollectedduringaflightforeachofthefiveposi3onparameters.
Parametersareprovidedthatgiveanindica:onofthe:mevariabilityofthemainpulseposi:onduringthecourseofaflight.
Quan3fyalinearfittothemainpulsecentroidposi3onforallgranulescollectedduringaflightandgivethedeparturefromthatfit(thedeltabetweenthegranulescentroidandthelinearfit).
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TEPImpulseResponseFolderContentsExampleof:meseriesplotsfortwooftheTEPimpulseresponseparametersshowingmainpulseprobabilityofdetec:onandcentroidrangeforeachofthegranulescollectedduringtheflightonAugust12,2015.Channelswithverylowprobabilityofdetec:on(03,09,15,16)causingnoisyresultsareploOedasverythinlines.
granulestart:me(secondsofday)
Channels
Color=beamThick=NIRThin=GreenSolid=_|_Dashed=||
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TEPImpulseResponseFolderContentsExampleoftwoplotsforparametersassociatedwiththelinearfittotheTEPimpulseresponsecentroids.Thetopshowseachgranulesdeparturefromthelinearfit.TheboOomshowstheR^2ofthefits.Channelswithverylowprobabilityofdetec:on(03,09,15,16)causingnoisyresultsareploOedasverythinlines.
granulestart:me(secondsofday)
Channels
Color=beamThick=NIRThin=GreenSolid=_|_Dashed=||
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Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC
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.
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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
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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
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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
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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
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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.
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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
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. 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
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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.
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260m
_|_/||
_|_/||
roughniasice
greywhiteice
specularskimice
roughopenwater
greywhiteice
greywhiteice
greywhiteice
specularskimice
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
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. 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
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Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC
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.
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Featuresofnote:• Posi:vecorrela:onbetweenNIRandGreenTxpowersbutlessconsistentthanexpected.Needtoassesswhy.
• Filterblocktemperaturedoesnotstabilize;notexpected.On-offdeadbandswitchnotworking?Needtoassesseffectonreceiverthroughput.
Rapidpowerchangesandextendingtozeroarenotunderstood.Inves3ga3onunderwayonthis.
InstrumentMonitoringforSignalAmplitudeCalibra:onLasertransmitpowersandreceiverspectralfilterblocktemperatures
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SIMPLInstrumentDescrip:on
SIMPLGreenland2015Campaign
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
44
March30,2016DocumentVersion1.1
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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
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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.
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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.
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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
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Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC
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.
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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
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Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC
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.
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front rear
SPCMdetectorenclosure
powersupply
enclosure
Frequencydoublertemperaturecontroller
powersupply
enclosure
laserpowermeter
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Greenland2015SIMPLRelease5DataProductDocumenta:onandInstrumentDescrip:on,Version1.1,March30,2016,D.Harding,NASA/GSFC
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.
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front
SPCMdetectorenclosure
powersupply
enclosure
P7889event:merInterfaceboards
enclosure
customC&DHcomputerandRAIDdrives
LasercontrollerandpowersupplyandGPStotallyaccurateclock(TAC)andcontroller
front
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SIMPLGreenland2015Campaign
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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AncillaryData:Applanix,FrameCameraandHyperspectralData
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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
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NadirColorCamera
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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
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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
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Representa:veFrameCameraImagesMel:ngPackIceinNaresStrait
~0.4kmal:tude
dependent
HighEleva:onInteriorAccumula:onZone
LowEleva:onCoastalAbla:onZone
InteriorandcostalimagesarebrightnessandcontrastenhancedtoemphasizesurfacefeaturesCirculardarkblotchinlowerrightisdustspeckoninsideoflens(cleanedoffforlaterflights)
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Sequen:alFrameCameraImages
~0.3kmal:tude
dependent
TarmacPassinfrontofThuleHangers
Imagesarebrightnessandcontrastenhancedtoemphasizesurfacefeatures
SeaIceNorthofEllesmere,August7,2015 Flightwasmostlycloudybelowtheplaneandat:meswatercondensedonwindowexterior(nosurfacesignal)withrareviewsofsurface(weaksignal).Alsocloudyaboveplanesosolarillumina:onwasweakanddiffuse.
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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
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References
SIMPLGreenland2015Campaign
G O D D A R D S P A C E F L I G H T C E N T E R
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March30,2016DocumentVersion1.1
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Dabney,P.,D.Harding,J.Abshire,T.Huss,G.Jodor,R.Machan,J.Marzouk,K.Rush,A.Seas,C.Shuman,X.Sun,S.ValeO,A.Vasilyev,A.Yu,andY.Zheng,2010,“TheSlopeImagingMul:-polariza:onPhoton-coun:ngLidar:developmentandperformanceresults,”inGeoscienceandRemoteSensingSymposium,2010IEEEInterna:onal,253-256,DOI10.1109/IGARSS.2010.5650862.
Harding,D.,P.Dabney,S.ValeO,A.Yu,A.VasilyevandA.Kelly,2011,“Airbornepolarimetric,two-colorlaseral:metermeasurementsoflakeicecover:ApathfinderforNASA’sICESat-2spaceflightmission”,inGeoscienceandRemoteSensingSymposium(IGARSS),2011IEEEInterna:onal,3598-3601,DOI10.1109/IGARSS.2011.6050002.
Harding,D.J.,P.W.DabneyandS.ValeO,2011,“Polarimetric,Two-Color,Photon-Coun:ngLaserAl:meterMeasurementsofForestCanopyStructure,”Proceedingsof2011Interna:onalSymposiumonLidarandRadarMapping:TechnologiesandApplica:ons,SPIE-TheInterna:onalSocietyforOp:calEngineering06/2011;DOI:10.1117/12.913960
Yu,A.W.,D.J.HardingandP.W.Dabney,2016,"LasertransmiOerdesignandperformancefortheslopeimagingmul:-polariza:onphoton-coun:nglidar(SIMPL)instrument”,Proc.SPIE9726,SolidStateLasersXXV:TechnologyandDevices,97260J(16March2016);doi:10.1117/12.2213005.
SIMPLPublica:ons
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