THIS PROPOSAL IS RESPONSIVE TO SUBELEMENT 2.1 SCIENCE DATA ANALYSIS OF NASA'S SCIENCE OF TERRA AQUA AND SUOMI NPP. THE OVERARCHING GOAL IS TO REFINE VALIDATE AND MAINTAIN GLOBAL ALGORITHMS FOR THE EXISTING STANDARD DATA PRODUCT OF PARTICULATE ORGANIC CARBON (POC) CONCENTRATION IN THE SURFACE OCEAN WHICH WILL ENSURE A CONTINUOUS MULTI-YEAR AND MULTI-SATELLITE POC RECORD FOR SUPPORTING RESEARCH ON DETECTING QUANTIFYING AND PREDICTING GLOBAL CHANGES IN POC AND ITS ROLES IN OCEAN CARBON CYCLE AND ECOSYSTEM. THIS CAPABILITY WILL HELP TO BETTER ADDRESS RESEARCH QUESTIONS RELATED TO THE GOALS OF NASA'S EARTH SCIENCE DIVISION SPECIFICALLY IN TWO EARTH SCIENCE FOCUS AREAS: CARBON CYCLE&ECOSYSTEMS AND CLIMATE VARIABILITY&CHANGE. POC IS AN ORPHAN DATA PRODUCT THAT WENT WITHOUT SUPPORT IN EARLIER SOLICITATIONS OF THIS NASA PROGRAM. THE NASA OCEAN BIOLOGY PROCESSING GROUP CURRENTLY PRODUCES POC AS A STANDARD GLOBAL OCEAN COLOR PRODUCT WHICH UTILIZES THE ALGORITHM DEVELOPED BY OUR LAB NEARLY A DECADE AGO WITH A LIMITED NUMBER OF IN SITU OBSERVATIONS. WE WILL REFINE AND EVALUATE THE INSTRUMENT-SPECIFIC (SEAWIFS MODIS-AQUA AND VIIRS) POC ALGORITHMS ON THE BASIS OF MUCH LARGER DATASETS INCLUDING MARINE ENVIRONMENTS THAT WERE UNDERREPRESENTED IN EARLIER ALGORITHM FORMULATIONS AND VALIDATION. THIS TASK WILL INCLUDE: (I) ASSEMBLY AND QUALITY CONTROL OF FIELD DATASETS FOR POC ALGORITHM REFINEMENT AND VALIDATION (II) ANALYSIS AND EVALUATION OF CANDIDATE APPROACHES TO ESTABLISH AND IMPLEMENT REFINED LEVEL-2 INSTRUMENT-SPECIFIC GLOBAL ALGORITHMS FOR CONTINUITY OF STANDARD GLOBAL POC DATA RECORD (III) EVALUATION OF ALGORITHM PERFORMANCE AND QUANTIFICATION OF UNCERTAINTIES IN STANDARD POC DATA PRODUCT AND (IV) INTERCOMPARISONS OF THE POC PRODUCT PROVIDED BY SEAWIFS MODIS-AQUA AND VIIRS OBSERVATIONS GLOBALLY AND WITHIN SPECIFIC GEOGRAPHICAL REGIONS. THE STANDARD INSTRUMENT-SPECIFIC ALGORITHMS WILL BE BASED ON MULTISPECTRAL REFLECTANCE DATA (BAND RATIO APPROACH POSSIBLY COMBINED WITH A COLOR INDEX APPROACH) BUT WE WILL ALSO DEVELOP AN EXPERIMENTAL POC PRODUCT BASED ON ALTERNATIVE SINGLE-WAVELENGTH ALGORITHM INVOLVING THE BACKSCATTERING COEFFICIENT AS AN INTERMEDIATE PRODUCT. THE LATTER WILL BE ALSO APPLICABLE TO LIDAR (E.G. CALIOP) OBSERVATIONS. AN ALGORITHM THEORETICAL BASIS DOCUMENT INCLUDING UNCERTAINTY ANALYSIS AND COMPUTER CODES WILL BE PROVIDED FOR IMPLEMENTATION INTO THE NASA STANDARD OCEAN COLOR PROCESSING STREAM THEREBY PRESERVING THE BACKWARD CONTINUITY SUPPORTING FULL INTEGRATION OF THE EXISTING MULTI-SATELLITE POC DATA RECORD AND READYING THE POC ALGORITHMS FOR THE JPSS ERA. WE ALSO PROPOSE TO DEVELOP AND EVALUATE NOVEL ALGORITHMS FOR GENERATING AN EXPERIMENTAL POC PRODUCT FOR OPTICALLY-COMPLEX COASTAL AND SHELF SEA ENVIRONMENTS IN WHICH THE STANDARD GLOBAL ALGORITHM EXHIBITS UNACCEPTABLE PERFORMANCE. THIS TASK WILL BE PURSUED IN COLLABORATION WITH FRENCH RESEARCHERS AT NO COST TO NASA AND WILL BUILD UPON OUR EARLIER FINDINGS ON THE UTILITY OF PARTICLE COMPOSITION-BASED APPROACHES FOR COASTAL WATER ALGORITHMS. WE WILL ALSO INVESTIGATE THE BLENDING APPROACHES FOR TRANSITIONS BETWEEN THE STANDARD (GLOBAL) AND EXPERIMENTAL (COASTAL) POC PRODUCTS AND EVALUATE THE READINESS STATUS OF THE EXPERIMENTAL PRODUCT FOR IMPLEMENTATION INTO NASA'S PROCESSING SYSTEM. IN ADDITION TO THE ALGORITHM-FOCUSED OBJECTIVES WE PROPOSE TO CONDUCT A FULL REANALYSIS OF GLOBAL AND BASIN-SCALE POC DATA RECORD FROM THE SEAWIFS MODIS-AQUA AND VIIRS OBSERVATIONS OVER A PERIOD OF ~20 YEARS PROVIDING REFERENCE BASELINE PROFILE OF POC AND A CRITICAL LOOK AT POSSIBLE TRENDS IN THE LONG-TERM RECORD IN SUPPORT OF GLOBAL CHANGE AND ECOSYSTEM CHARACTERIZATION RESEARCH. ONE SPECIFIC COMPONENT OF THIS ANALYSIS WILL FOCUS ON LONG-TERM SUMMER-TIME PATTERNS OF POC IN ARCTIC SEAS THAT ARE PARTICULARLY SENSITIVE TO CLIMATE PERTURBATIONS. THE PI AND CO-IS REQUEST MEMBERSHIP IN THE NASA'S OCEAN BIOLOGY AND BIOGEOCHEMISTRY MEASUREMENTS TEAM.