THE UV-VIS OZONE MONITORING INSTRUMENT (OMI) LAUNCHED ON NASA'S AURA SATELLITE IN JULY 2004 WAS THE FIRST SPACE-BASED SENSOR TO PROVIDE OPERATIONAL SULFUR DIOXIDE (SO2) MEASUREMENTS FOR USE BY THE SCIENTIFIC COMMUNITY. FOR OVER A DECADE FROM 2004 THE OMI DAILY GLOBAL SO2 MEASUREMENTS WERE PRODUCED USING THE LINEAR FIT (LF) AND BAND RESIDUAL DIFFERENCE (BRD) ALGORITHMS. HOWEVER THEORETICAL INVESTIGATIONS DATA ANALYSES AND VALIDATION STUDIES HAVE BROUGHT TO LIGHT A NUMBER OF AREAS IN WHICH OMI SO2 PRODUCTS MAY BE IMPROVED AND EXPANDED.WITH PREVIOUS ROSES FUNDING WE HAVE DEVELOPED AN ADVANCED ALGORITHM THE ITERATIVE SPECTRAL FITTING (ISF) ALGORITHM CURRENTLY OPERATIONAL IN OZONE SIPS (SCIENCE INVESTIGATOR-LED PROCESSING SYSTEMS) TO RETRIEVE SIMULTANEOUSLY O3 SO2 OTHER TRACE GASES (INCLUDING NO2 BRO HCHO) AND CLOUD PRESSURE FROM THE EARTHVIEW RADIANCES MEASURED BY THE OZONE MAPPING AND PROFILER SUITE - NADIR MAPPER (OMPS-NM) FLYING ON THE SUOMI NATIONAL POLAR PARTNERSHIP (SNPP) SPACECRAFT.IT HAS BEEN DEMONSTRATED THAT THE ISF ALGORITHM CAN ACHIEVE MORE ACCURATE AND MORE PRECISE RETRIEVALS FOR THE BROAD RANGE OF SO2 LOADINGS ENCOUNTERED IN ATMOSPHERIC REMOTE SENSING FROM CONCENTRATIONS (>0.1 DU) IN POLLUTED AREAS TO STRONG VOLCANIC EMISSIONS WITH VERTICAL COLUMN DENSITY (VCD) EXCEEDING 1000 DU. FURTHERMORE THE VOLCANIC SO2 CLOUD HEIGHT MAY ALSO BE RETRIEVED DIRECTLY FROM THE RADIANCE MEASUREMENTS WHEN VCD IS SUFFICIENTLY LARGE (>5 DU) USING THE EXTENDED ISF (EISF) ALGORITHM.WE PROPOSE TO PRODUCE NEW AND SIGNIFICANTLY IMPROVED OMI SO2 PRODUCTS USING THE ISF ALGORITHM AND MAKE THEM PUBLICLY AVAILABLE AT GODDARD EARTH SCIENCES (GES) DATA AND INFORMATION SERVICES CENTER (DISC). THE ENHANCED SENSITIVITY AND EXPANDED VALID RANGE OF SO2 MEASUREMENTS REALIZED BY THE ISF RETRIEVALS WILL GREATLY ADVANCE THE MAPPING OF EXPLOSIVE VOLCANIC PLUMES WITH THE ADDITIONAL HEIGHT INFORMATION AND INCREASE THE ACCURACY OF SO2 EMISSION QUANTIFICATIONS. THE IMPROVED PRODUCTS WILL ALSO PROVIDE A HIGHER QUALITY LONG-TERM GLOBAL DATA SET OF LOWER TROPOSPHERIC SO2 EMITTED BY QUIESCENT VOLCANIC DEGASSING AND ANTHROPOGENIC SOURCES. SPECIFICALLY WE PROPOSE A THREE-YEAR PROJECT TO1) PRODUCE A NEW OMI L2 PRODUCT OF HEIGHT-RESOLVED SO2 VCD FOR VOLCANIC ERUPTIONS USING THE EISF ALGORITHM; THIS PRODUCT WILL CONTINUE THE LONG-TERM EXPLOSIVE VOLCANIC SO2 DATA RECORD WITH IMPROVED ACCURACY AND WITH CRITICAL NEW INFORMATION ABOUT SO2 HEIGHT DISTRIBUTIONS;2) PRODUCE A SIGNIFICANTLY IMPROVED OMI L2 PBL SO2 PRODUCT FOR THE ENTIRE OMI RECORD CHARACTERIZED BY HIGHER PRECISION AND LOWER BIAS ACHIEVED BY APPLYING THE ISF ALGORITHM TO SOFT-CALIBRATED OMI L1B RADIANCE.THIS PROPOSAL DIRECTLY RESPONDS TO THE STATED OBJECTIVES OF THIS CALL. SPECIFICALLY IT ALIGNS WITH ITS 2ND OBJECTIVE: 'DEVELOPING NEW OR SIGNIFICANTLY IMPROVED LEVEL 2 DATA THAT ARE NOT SUPPORTED BY THE AURA PROJECT CORE DATA ANALYSIS BUDGET.'THE PROPOSED RESEARCH BUILDS ON THE ACHIEVEMENTS OF OUR PROPOSAL TEAM IN SATELLITE REMOTE SENSING OF ATMOSPHERIC CONSTITUENTS AND THEIR VALIDATIONS OUR EXPERTISE IN INSTRUMENT CHARACTERIZATION SOFT CALIBRATION AND ARTIFACT CORRECTIONS AND OUR EXPERIENCES IN DEVELOPING IMPLEMENTING AND MAINTAINING BOTH THE STANDARD AND NRT SO2 AND NO2 PROCESSING SOFTWARE FOR OMI AND OMPS.