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WISM A Wideband Instrument for Snow MeasurementPast Accomplishments, Current Status, and Path Forwardby:Quenton Bonds, PhDLead Radiometer Systems Engineer

Paul Racette, PhDCo Investigator

Principle InvestigatorTim Durham, PhD, Harris Corporation

Project OverviewGSFC AccomplishmentsScience Experiment IScience Experiment IICurrent Status & Path ForwardPresentation Outline

Project Overview: NASA ROSES IIPObjectives, Motivation, and ApproachNASA ROSES IIP (Research Opportunities in Space and Earth Sciences Instrument Incubator Program) Currently in second round of fundingObjective Develop the Science and Technology to carry out snow remote sensing missions to make snow measurements on Airborne platforms Space platformsMotivation SCLP mission will include four instruments to gather data on snow pack extent, depth and massX-band SARKu-band SARKu-band radiometerKa-band radiometerX-Band radiometer Current State of the Art LimitationsExisting antenna concept uses reflector antennas fed by individual feeds for each frequency/beamMulti-element feeds produce offset beams, which impede the science The WISM Approach Demonstrated the technology to replace the feed manifold with a single array feed capable of supporting both SAR and radiometryPerformance improvement (i.e. co-boresighting)Significant size, weight, power advantagesEnables enhanced SWE algorithm development

WISM IIP FeedExisting Technology Feed Concept

Notional SCLP Spacecraft3

Importance of Seasonal SnowSupplies 50% to 80% of the yearly water supply in the Western United StatesAccurate measurement of the snow water equivalent (SWE), are needed to effectively manage water resourcesChallenge: on the very small spatial scales over which the snowpack varies. Project Overview: Science Implications and Broader Impact

Highly variable snowpack

Conceptualization of the measurement of SWE and other snow parameters from space 4Ground truth experiments are conducted in parallel with airborne SWE measurements

GSFC TeamRF: 555Data-System: 587Thermal System: 545Power System: 563

Instrument SubsystemsRF: 3x Radiometer Bands; Ku, Ka and X Data-SystemFour Zone Thermal System Power System

CalibrationInternal Calibration via 6x Calibration StatesCalibration Standards: Ambient termination, Cold Termination, 2x Noise sources External Pre-Flight CalibrationNoise Source External Black Body Target

Frequency BandsKu 18.6 GHz 18.8 GHzKa 36.0 GHz 37.0 GHzX 10.6Ghz 10.7GHz

Key SpecificationsHorizontal PoliarizationSpatial Resolution: 93mUncertainty: < 0.5 KTemp Resolution NeDT < 0.5 K

Project Overview: GSFCs Role The WISM Radiometer5

GSFC ACCOMPLISHMENTS

GSFC Team Accomplishments

Completed engineering integration and test (I&T) radiometerMeasurement test bench configurationGSFC 1st order calibrationGSFC laboratory measurements and data analysisGSFC SIRF lab snow measurement

Completed I&T of radiometer with WISM antennaGSFC SIRF lab snow measurementGSFC BLD 33 rooftop measurementsNoise inject test

Completed I&T of radiometer, radar and antenna @ HarrisValidated instrument (radar - radiometer) operation, power, etc.Tested radar blanking signalTested Zone 4 thermal assemblyConfigured and test GPS/IMUNo radar transmit interferenceEnhanced flightworthiness of cables and harnessing

Data Post-Processing Program (DPP) DevelopmentDPP DevelopmentL1A completedL1B In progressPre-flight calibration applicationCold sky calibrationCold and hot target calibration

Science Experiment I CompletedViable data received on all flightsCalibrated radiometer data deliveredCorrection in progress

WISM II EnhancementsEnhanced calibration via external noise injection Additional radiometer bandEnhanced the DPPs

Science Experiment II CompletedViable data received on all flights except X-bandResults promisingCorrection in progress

Q.Bonds secured supplemental funding via SECP and IRAD

Full I&T @ Harris Radiometer I&T@ GSFC Laboratory Meas@ GSFC Science Experiments@ Grand MesaGSFC Accomplishments: Overview7

GSFC Accomplishments: Radiometer System Design8

Internal Calibration interleaved with science dataTwo 50 waveguide terminations; primary, long averagesTwo noise sources (NS); secondary

Radiometer Box InputRoom temperature terminationLN2 Dewar

Antenna Calibration (sheet array)Room temperature blackbodyLN2 blackbody

Pre-flight calibrationAmbient blackbody box over sheet array

Flight Data CalibrationAntenna Pattern CorrectionInternal calibration + thermal correction of front-end losses (sheet array, triplexer)

9GSFC Accomplishments: Radiometer System Design

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Functional TestingData digitizationCalibration state sequencingNoise source switchingThermal control and stabilityThermal controlRadar blanking signal

GSFC Accomplishments: Integration and Test (I&T)

Task: WISM Antenna Integration with Radiometer Install measurement grade test tablesConfigure mobile test benchInstall WISM antenna feed into the reflector assemblyFeed angle of critical importanceReflector angle of critical importanceIntegrate radiometer with WISM antenna

Task: Preliminary Lab Tests to Confirm System FunctionalityData-system samplingInstrument controlRecording of science and telemetryThermal system Task: SIRF Lab Meas with WISM AntennaPerformed with Ludovic Brooker, Code 615 ScientistData-system samplingInstrument control

GSFC Accomplishments: Integration and Test (I&T)11

Task: Performance Validation via Cold-Sky Measurements on Bld 33 Roof Objective: Final Step Before Radar Integration at Harris in MelbourneRadiometer preliminary performance analysis to quantify: StabilityResolution - NeDTData-system sampling and timingImpact of the radome

BLD 33 Roof: Unobstructed View of Known TargetsZenith45 degreesCold black bodyWarm black body Radome measurements

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45 Zenith

45 ZenithRadomeBlack Body

22.5 GSFC Accomplishments: Integration and Test (I&T)12

Measurements Taken Zenith, 45 Degrees, Cold Black Body, Warm Black Body , Radome MeasurementsKu vs Ka Radome Measurements Below

GSFC Accomplishments: Integration and Test (I&T)13

Full Instrument I&T at HarrisResults: Confirmed with good confidence: The radar will not interfere with or damage the radiometer Final updates to the data-systemIntegration of radar and radiometerValidate instrument (radar - radiometer) operation, power, etc. Test radar blanking signalTest Zone 4 thermal assemblyConfigure and test GPU/IMU No radar transmit interferenceCables harnessing more flight worthy

Melbourne FloridaIn the Lab @ Harris

Radar Transmitting

Radiometer Blanking Validated

No Interference

GSFC Accomplishments: Full Instrument Integration and Test (I&T)14

Science Experiment I

Grand Mesa Snow MeasurementFebruary 2015

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Nadir Port (36x23x13|15)Lidar (22x13x10)

Twin Otter DC6

Rear Nadir Port

Mini-ATM Lidar in Nadir Well

Approx. Position in FuselageTwin Otter FuselageSeat Track BracketsT/R BoxINSRadiometerTriplexerFeed ArrayBoise St. Radar

Rear Door HatchScience Experiment I: Aircraft Procurement and Mechanical Integration

Science Experiment: Grand Mesa ColoradoPre-Flight Calibration Before Each FlightHot target (kept outside, temp ~17C - 19C)Cold target (kept outside, temp ~2C - 3.5C)Hot and cold targets were cycled onto the calibration structure Zenith (Cold Sky)45 (Cold Sky)

Measurements: SWE at 3 altitudes above the Grand Mesa; 1500ft, 3000ft, 5000ft

Cold Sky Cal @ ZenithCold Sky Cal @ 45WISM Payload @ Twin Otter DoorCold/Hot Target CalScience Experiment I: Aircraft Measurements

Science Experiment: Grand Mesa Colorado4 Flights 2/21/2015 Mesa2/22/2015 GJT Airport (Lidar/Radar) Cal2/24/2014 Mesa morning & Mesa afternoon

Ground Truth Site Visit with HP Marshall, PhD and Kelly Elder, PhDSurveyed area of investigationDug and surveyed snow pitAnalyzed snow crystals at microscopic level

Science Experiment I: Aircraft Measurements18

Process Raw Data: Bin to DecApply Triangular Mov AvgApply Calibration Remove SpikesAvg Per State Change, 10ms to 30msProcess Raw Data: Bin to DecApply CalibrationApply Triangular Mov AvgRemove SpikesAvg Per Cycle 240msEnhanced DesignPrev DPP Design

Apply Model to Correct for LossCalibrate Flight Data with Pre-FlightPerform Optimization on Model ParametersGeolocate DataScience Experiment I: Data Post-Processing19

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Science Experiment II

Grand Mesa Snow Free MeasurementOctober 2015

Science Experiment II: Pre-Flight 21

Science Experiment II: Flight

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Flt #DateDurationRadiometerRadarminiATMNotes(hours)XKuKaXKu14-Oct2.0miniATM foresight calibration and miniATM/radiometer flight over Mesa at 1.5kft. Radiometer and miniATM reported normal operation. Poor connection on X-band radiometer. No radar.26-Oct1.1Local flight over airport to test radar. Radar sampling window set wrong, no useful data.37-Oct0.7Local flight over airport for radar. CW leakage signal corrupted radar data.48-Oct0.9Local flight over airport for radar. Radar reported normal operation. miniATM removed from aircraft58-Oct2.3Local flight and then over Mesa at 5kft. Radar and radiometer reported normal operation. No miniATM.69-Oct2.7Local flight and then over Mesa at 5kft. Radar and radiometer reported normal operation. No miniATM.Validated DataUnsure: Data received but not processedNo Usable Data

Science Experiment II: Flight Measurement Summary

Current Status and Path Forward

Science Experiment 1 Snow: Data Analysis Data Collect: Sci Exp-1 Flt-4 3000ft Pas-1 EastboundCalibration with No CorrectionCorrelated to TB via Q.Bonds/555, Geolocated via K.Speed/Harris, Mapped and via L.Brucker/GSFC 615

Science Experiment 1 Ka Radiometer Brightness Temperature Geolocated Above the Grand MesaScience Experiment 1 Ku Radiometer Brightness Temperature Geolocated Above the Grand MesaLakesCanopyCurrent Status: Science Experiment I Data Post Processing and Analysis25

Sci Exp-1 Flt-4 3000ft Pas-1 Eastbound: Tb Over Lakes Plotted on World Map Actual vs Zoomed ScaleTB of Lakes vs Canopy Demonstrate the Desired Trend Over the Grand Mesa

LakesLakesCurrent Status: Science Experiment I Data Post Processing and Analysis26

SE1 vs SE 2 @1500Ft Eastbound: Data Analysis Calibration with No Correction

Current Status: Science Experiment II Data Post Processing and Analysis27

SE1 Flight 1 Ka Calibrated Via Preflight Data (light blue/orange) Radiometer data before (blue) and after (pink/green) the model is applied

Current Status: Calibration Correction28

SE1 Flight 1 Ka Preflight Calibration References (blue/blue dashed/black dashed) Versus Model Predications (pink) Optimization SetupCurrent Status: Model Optimization to Correct the Calibration29

Prior to Next Field CampaignImplement differential mode on A/DFabricate insulated ambient target calibratorsUpdate firmware on external calibratorAddress X-band switch sequence issue

Enhance Data Post Processing ProgramsImproved automation enabling faster post processing e.g. during the science experimentCalibrate radiometer science data using pre-flight calibrationEnhanced calibration algorithms Provide calibrated and corrected TB to be applied to SWE algorithm

Path Forward: Marginal Updates Prior to Next Science Experiment30