THE GOAL OF THIS 3-YEAR STUDY IS TO EXTEND AND TO IMPROVE THE EXISTING SEA SURFACE SALINITY (SSS) SATELLITE DATA VALIDATION FRAMEWORK BEYOND THE NASA AQUARIUS MISSION THUS SUPPORT NASAS PROGRAM TO CONTINUE OCEAN SALINITY SCIENCE. AQUARIUS WAS NASAS FIRST MISSION DEDICATED TO MEASURING SSS AND COLLECTED 45 MONTHS OF GLOBAL DATA UNTIL AN ELECTRICAL MALFUNCTION ON THE SATELLITE ENDED THE MISSION IN EARLY JUNE 2015. EARTH AND SPACE RESEARCH (ESR) TOOK THE LEADING ROLE FOR AQUARIUS SSS DATA VALIDATION AND ERROR ANALYSIS. ESR DEVELOPED THE AQUARIUS VALIDATION DATA SYSTEM (AVDS) AS A PRINCIPAL TOOL FOR THE AQUARIUS SCIENCE DATA VALIDATION RESEARCH. THE AVDS IS A REPOSITORY OF OCEANOGRAPHIC IN SITU SSS DATA AND DATA PROCESSING TOOLS TO MATCH THESE OBSERVATIONS WITH AQUARIUS SATELLITE LEVEL 2 AND LEVEL 3 SCIENCE DATA SETS. THE WORK PROPOSED HERE WILL APPLY THE SAME PRINCIPLES TO THE CURRENTLY OPERATING SALINITY-OBSERVING SATELLITES: THE NASA SOIL MOISTURE ACTIVE PASSIVE (SMAP) AND THE ESA SOIL MOISTURE OCEAN SALINITY (SMOS) MISSIONS. ESR PROPOSES TO ENHANCE THE AVDS TO A MORE VERSATILE SALINITY VALIDATION DATA SYSTEM (SVDS) THAT WILL SUPPORT QUANTITATIVE VALIDATION AND INTER-COMPARISON ANALYSES FOR ALL THREE OF THESE SATELLITE SALINITY DATA SETS. THE PRIMARY FUNCTIONS OF SVDS SHALL BE: 1. INDIVIDUAL SATELLITE INSTRUMENT CALIBRATION AND VALIDATION AS WELL AS INTER-INSTRUMENT CALIBRATION BETWEEN MISSIONS WHERE PRACTICAL 2. OPEN PUBLIC ACCESS TO SALINITY MATCH-UP DATA FOR SALINITY RESEARCHERS 3. NEAR-REAL-TIME VALIDATION ANALYSIS OF SALINITY FROM ACTIVE SALINITY MISSIONS THE VALIDATION WILL ALSO ADDRESS SEA SURFACE DENSITY/SPICINESS WHICH IS CALCULATED FROM SMAP-SSS AND ANCILLARY SEA SURFACE TEMPERATURE DATA. IT IS ALSO OUR OBJECTIVE TO SUMMARIZE THE UNCERTAINTIES FOR SALINITY MEASUREMENTS THAT HAVE BEEN STUDIED BY DIFFERENT RESEARCH GROUPS. THE WORK WILL ADVANCE UNDERSTANDING OF THE ROLES OF UNCERTAINTIES IN CAUSING THE DIFFERENCES BETWEEN OBSERVED SSS AND REFERENCE SSS. IN THIS PROPOSAL WE PROPOSE TO: 1) DEVELOP THE NEW SVDS BASED ON THE ARCHITECTURE LEGACY OF THE AVDS 2) CONTINUE THE VALIDATION FOR SATELLITE SEA SURFACE SALINITY OBSERVATIONS 3) SUPPORT THE ALGORITHM AND VALIDATE THE SEA SURFACE DENSITY AND SPICINESS DATA 4) SUMMARIZE KNOWN UNCERTAINTIES FOR SALINITY MEASUREMENTS