BACKGROUND/OBJECTIVES: (A) PHASE-RATIO ANALYSIS IS BECOMING A WIDELY USED TECHNIQUE TO OBTAIN SUB-RESOLUTION INFORMATION ON THE SCATTERING BEHAVIOR AND PARTICLE SIZE FOR THE SURFACES OF AIRLESS BODIES. RECENTLY PUBLISHED EXAMPLES HAVE EMPLOYED SPACECRAFT IMAGES FROM THE MOON MERCURY EROS AND VESTA. PHASE-RATIO IMAGES FORMED FROM CO-REGISTERED IMAGES OF THE SAME LOCATION COLLECTED AT DIFFERENT PHASE ANGLES CAN REVEAL ANOMALOUS PHOTOMETRIC BEHAVIOR. THE ANOMALY CAN BE INTERPRETED IN TERMS OF THE ROUGHNESS OR PARTICLE SIZE OF THE SURFACE. FOR EXAMPLE PYROCLASTIC DEPOSITS ON MERCURY WERE FOUND TO HAVE CHARACTER CONSISTENT WITH THE PRESENCE OF MATERIAL THAT IS FINER-GRAINED THAN THE SURROUNDINGS. HOWEVER CONCLUSIONS TO DATE HAVE BEEN LIMITED TO QUALITATIVE INFERENCES ("AREA 1 MUST HAVE FINER PARTICLES THAN NEARBY AREA 2"). THE LACK OF A COMPREHENSIVE LABORATORY FRAMEWORK FOR INTERPRETATION PREVENTS QUESTIONS LIKE "HOW MUCH FINER?" FROM BEING ANSWERED. (B) THERE IS GROWING INTEREST IN IMAGING POLARIMETRY AS A REMOTE-SENSING TECHNIQUE FOR INTERROGATING PLANETARY SURFACES. THE HAYABUSA SPACECRAFT CARRIED A CAMERA (AMICA) DESIGNED TO OBTAIN POLARIZATION IMAGES OF ASTEROID ITOKAWA. THE FORTHCOMING KOREA PATHFINDER LUNAR ORBITER (KPLO) INCLUDES POLCAM WHICH WILL COLLECT MULTI-POLARIZATION IMAGING OF THE MOON. UNLIKE REFLECTANCE AND EMITTANCE SPECTROSCOPY THERE HAS BEEN RELATIVELY LITTLE LABORATORY WORK AIMED AT EXPLORING THE POLARIZATION BEHAVIOR OF PLANETARY SURFACE MATERIALS. SUCH FOUNDATIONAL WORK IS NECESSARY FOR THE POLCAM AND OTHER FUTURE DATASETS TO YIELD THEIR GREATEST SCIENTIFIC RETURN. PROPOSED METHODS/TECHNIQUES: WE PROPOSE TO ESTABLISH A PLANETARY SURFACE TEXTURE LABORATORY AS AN INVESTIGATOR FACILITY INSTRUMENT TO EXPLORE THE PHASE AND POLARIZATION OF REGOLITH ANALOGS AS A FUNCTION OF ILLUMINATION (I) VIEWING (E) AND PHASE (G) ANGLES. WE WILL COLLECT DATA WITH AN IMAGING POLARIMETER THAT WAS PURCHASED WITH APL OVERHEAD FUNDS. THE CAMERA SIMULTANEOUSLY COLLECTS IMAGES IN MULTIPLE POLARIZATION STATES. WITH PME FUNDING WE PROPOSE TO CONSTRUCT A GONIOMETER SO THAT A LIGHT SOURCE AND THE POLARIMETER CAN BE MOVED THROUGH A RANGE OF (I E G). SOIL ANALOGS WILL BE PLACED IN TRAYS THAT ARE LARGE ENOUGH TO PERMIT DIFFERENT SURFACE PREPARATIONS TO BE VIEWED TOGETHER. THE REGOLITH ANALOGS WILL BE CHARACTERIZED IN TERMS OF PARTICLE SIZE-FREQUENCY DISTRIBUTION AND CRUCIALLY THE MATERIAL WILL ALSO BE CHARACTERIZED IN TERMS OF SHAPE. THE PARTICLE SIZE/SHAPE ANALYSIS WILL BE DONE WITH A RETSCH CAMSIZER X2 IN WHICH AN AIR STREAM ENTRAINS A SAMPLE OF GRANULAR MATERIAL AND PASSES THE PARTICLES THROUGH A MICROSCOPE AND HIGH-SPEED CAMERA. AUTOMATED IMAGE-PROCESSING ROUTINES EXTRACT A VARIETY OF PARTICLE SIZE AND SHAPE PARAMETERS INCLUDING AVERAGE PARTICLE DIAMETER SPHERICITY AND CONVEXITY AS WELL AS THE STANDARD DEVIATIONS AND SIZE-FREQUENCY DISTRIBUTIONS OF THESE PARAMETERS. THE DATA OBTAINED WITH PSTL WILL ALSO PROVIDE THE BASIS FOR MODELING STUDIES. THE COMPREHENSIVE DATA IN (I E G) WILL BE USED FOR PHOTOMETRIC MODELING E.G. EXTRACTION OF HAPKE PARAMETERS THAT CAN BE LINKED TO THE KNOWN PARTICLE PROPERTIES. WE WILL TEST EMPIRICAL RELATIONS THAT CONNECT PARTICLE SIZE TO POLARIZATION AND ALSO DEVELOP RIGOROUS RADIATIVE-TRANSFER CODE THAT INCLUDES STOKES PARAMETERS AND INCORPORATES PARTICLE SIZE PACKING AND SHAPE. PERCEIVED SIGNIFICANCE: THE PROPOSED LABORATORY REPRESENTS A UNIQUE CAPABILITY FOR IMAGING STUDIES OF THE PHOTOMETRIC AND POLARIZATION BEHAVIOR OF REGOLITH ANALOGS THAT HAVE BEEN QUANTITATIVELY CHARACTERIZED. BY CARRYING OUT SYSTEMATIC INVESTIGATION OF WELL CHARACTERIZED SAMPLES WE WILL PROVIDE THE FOUNDATION FOR INTERPRETATION OF PHASE-RATIO IMAGE DATA FROM PAST AND FUTURE PLANETARY MISSIONS AND FOR FUTURE POLARIZATION IMAGE DATA FROM MISSIONS LIKE KPLO. REMOTE ASSESSMENT OF PARTICLE SHAPES AND SIZES COULD ALSO BENEFIT SITE SELECTION FOR IN SITU RESOURCE UTILIZATION.