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OCEANOGRAPHY IS NO LONGER JUST AN EARTH SCIENCE. STANDING BODIES OF LIQUID THAT INTERACT WITH BOTH ATMOSPHERIC AND SURFACE RESERVOIRSALSO EXIST ON TITAN RECENTLY CASSINI OBSERVATIONS HAVE FOUND EVIDENCE FOR WIND WAVES ON THE SURFACE OF TITANS LAKES AND SEAS. ONEARTH WIND WAVE OBSERVING RADARS ARE COMMONLY USED AS ANEMOMETERS TO MEASURE SURFACE WINDS. SIMILARTO THESE WEATHER SATELLITESCASSINI DATA CAN BE USED TO ESTIMATE THE RMS HEIGHT AND OR SLOPE OF ROUGHNESS ON TITANS LAKES AND SEAS. WHEN COUPLED TO A WINDWAVEGENERATION MODEL THESE MEASUREMENTS CAN BE USED TO ESTIMATE THE WIND SPEED NECESSARY TO DRIVE THE WAVE FIELD. WE PROPOSE TOCOUPLE A PROVEN WAVE GENERATION MODEL TO CASSINI OBSERVATIONS OF ROUGHNESS ON TITANS LIQUID SURFACES IN ORDER TO CONSTRAIN SURFACE WINDSTHE UNIVERSITY OF MIAMI WAVE MODEL UMWM IS A SPECTRAL WAVE MODEL THAT CAN CALCULATE THE WAVENUMBER DIRECTIONAL SPECTRUM ONANY LAKE OR SEA BASIN GIVEN THE WIND SPEED AND DIRECTION THE MODEL ALSO CALCULATES THE TANGENTIAL STRESS OF THE WIND ON THE SURFACEUMWM HAS BEEN ADAPTED TO INCLUDE ALL WAVES GRAVITY CAPILLARY GRAVITY AND CAPILLARY AND TO BE APPLICABLE TO ANY GAS LIQUIDINTERFACE WITH MERELY A CHANGE IN THE FLUID PARAMETERS AND GRAVITY THIS UNIVERSAL WAVE AND STRESS UNIWSM HAS BEEN VALIDATEDUSING WAVE TANK EXPERIMENTS THAT VARIED LIQUID PROPERTIES VISCOSITY DENSITY AND ATMOSPHERIC PRESSURE DOWN TO 40 MBARS WE WILLADAPT UNIWSM TO THE TITAN ENVIRONMENT AND USE IT TO MODEL WAVES GENERATED ON TITANS HYDROCARBON LAKES IN RESPONSE TO VARIABLEWIND SPEEDS UNIWSM PROVIDE THE LINK BETWEEN WIND AND THE RMS HEIGHT SLOPE OF WAVE ROUGHENED LIQUID HYDROCARBON SURFACESPROVIDING THE FRAMEWORK NECESSARY TO ADD AN ANEMOMETER CAPABILITY TO CASSINICASSINI HAS THREE WAYS TO MEASURE THE RMS HEIGHT AND OR SLOPE ON LIQUID SURFACES VIMS SPECULAR REFLECTIONS RADAR ALTIMETRY ANDRADAR SCATTEROMETRY OF THESE THE VIMS OFF SPECULAR GLINTS PROVIDE THE MOST NUMEROUS OBSERVATIONS THAT HAVE BEEN INTERPRETEDAS WAVE ACTIVITY WHEN VIMS OBSERVES A SPECULAR REFLECTION OF THE SUN FROM A PART OF A LAKE SURFACE THAT SHOULD NOT HAVE A SPECULARREFLECTION IF IT WERE PERFECTLY SMOOTH THE INCREASED INTENSITY TELLS US THE FRACTION OF THE SURFACE THAT IS ORIENTED IN A PARTICULAR DIRECTIONINCIDENCE ANGLE + - THE VIMS IFOV2 RELATIVE TO THE SURFACE NORMAL THIS QUANTITY IS KNOWN AS THE SPECULAR AREA FRACTION SAF ANDFOR GIVEN WIND SPEED DIRECTION AND INCIDENCE ANGLE CAN BE DIRECTLY COMPARED TO THE OUTPUT OF THE UNIWSM TITAN MODEL TO CONSTRAINWIND SPEEDS THIS TECHNIQUE HAS BEEN SUCCESSFULLY APPLIED TO SUN GLINTS ON EARTH TO CONSTRAIN SURFACE WINDS WE WILL DETERMINE THESAF REQUIRED TO PRODUCE THE OBSERVED BRIGHTNESS OF THE APPROXIMATELY ONE DOZEN OFF SPECULAR INFRARED GLINTS OBSERVED BY VIMS THATHAVE BEEN INTERPRETED AS WAVE ACTIVITY OVER LIQUID SURFACES EACH OF THESE OBSERVATIONS CONSISTS OF BETWEEN 14 AND 102 INDIVIDUAL VIMSCUBES PERMITTING A ROBUST DATASET FOR ERROR ANALYSIS AND MODEL VALIDATION PRELIMINARY WORK HAS DETERMINED THAT THE BRIGHTNESS OFVIMS SPECULAR REFLECTIONS HAVE A STRONG LOGARITHMIC DEPENDENCE ON BOTH WIND SPEED AND AZIMUTH ANGLE SUGGESTING THAT THE BRIGHTNESSOF OFFSPECULAR RETURNS CAN BE A SENSITIVE MEASURE OF WAVE ACTIVITY ON TITAN.THE PROPOSED RESEARCH IS RELEVANT TO CDAP BECAUSE IT WILL ENHANCE THE SCIENTIFIC RETURN OF THE CASSINI DATASET BY DIRECTLY ADDRESSINGOUR UNDERSTANDING OF TITANS CLIMATE SPECIFICALLY THE PROPOSED RESEARCH WOULD INVOLVE DIRECT ANALYSIS OF CASSINI VIMS OBSERVATIONS TOADDRESS A CLEAR SCIENCE OBJECTIVE TO CONSTRAIN SURFACE WINDS ON TITAN TO DATE MEASUREMENTS OF TITANS WINDS HAVE BEEN DERIVED FROMTRACKING THE HUYGENS DESCENT KNOWLEDGE OF SURFACE WINDS ARE LIMITED TO INDIRECT ESTIMATES BASED ON THE COOLING RATE OF THE HUYGENSPROBE THE PROPOSED RESEARCH WOULD CONSTRAIN SURFACE WINDS MORE DIRECTLY AND PROVIDE DATA AT THE POLES AS OPPOSED TO THE EQUATOR

$359,258FY2020National Aeronautics and Space AdministrationNASA

Cornell University, Ithaca NY

Investigators

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