SATELLITE MEASUREMENTS OF VOLCANIC SULFUR DIOXIDE (SO2) AND ASH EMISSIONS ARE CRUCIAL FOR DETECTION OF VOLCANIC ERUPTIONS AND FOR QUANTIFYING VOLCANIC IMPACTS ON THE ATMOSPHERE AND CLIMATE. VOLCANIC SO2 AND ASH EMISSIONS HAVE BEEN MEASURED BY ULTRAVIOLET (UV) AND INFRARED (IR) SENSORS ON POLAR-ORBITING SATELLITES SINCE THE LATE 1970S BUT WITH POOR TEMPORAL RESOLUTION. SEVERAL GEOSTATIONARY IR SENSORS CAN DETECT VOLCANIC ASH AND SO2 BUT WITH LOWER SENSITIVITY THAN UV MEASUREMENTS ESPECIALLY IN THE LOWER TROPOSPHERE. THIS HAS LIMITED OUR ABILITY TO STUDY KEY PROCESSES DURING THE INITIAL FEW HOURS OF ATMOSPHERIC RESIDENCE OF VOLCANIC ERUPTION CLOUDS. IN 2015 THE LAUNCH OF THE EARTH POLYCHROMATIC IMAGING CAMERA (EPIC) ABOARD THE DEEP SPACE CLIMATE OBSERVATORY (DSCOVR) PROVIDED THE FIRST OPPORTUNITY TO OBSERVE VOLCANIC ERUPTION CLOUDS GLOBALLY FROM THE L1 EARTH-SUN LAGRANGE POINT. EPIC IS A 10-CHANNEL UV NEAR IR SPECTRORADIOMETER THAT PROVIDES SUNRISE-SUNSET EARTH OBSERVATIONS WITH A CADENCE OF 68-110 MINUTES DEPENDING ON SEASON WITH CALIBRATED EPIC UV RADIANCES AVAILABLE FOR LEVEL 2 (L2) RETRIEVALS OF TRACE GASES INCLUDING OZONE AND SO2 AND CALCULATION OF A UV AEROSOL INDEX (AI) THAT IS SENSITIVE TO VOLCANIC ASH. EPIC HENCE OFFERS THE POTENTIAL FOR MULTIPLE DAILY OBSERVATIONS OF VOLCANIC SO2 AND ASH CLOUDS IN ITS FIELD OF VIEW. EPIC S UNIQUE ABILITY TO PROVIDE HIGH-CADENCE UV OBSERVATIONS OF VOLCANIC ERUPTION CLOUDS HAS BEEN DEMONSTRATED IN SEVERAL RECENT VOLCANIC ERUPTIONS. THE INCREASED OBSERVATION FREQUENCY OF DSCOVR/EPIC WILL PERMIT MORE TIMELY VOLCANIC ERUPTION DETECTION IMPROVED TRAJECTORY MODELING AND NOVEL ANALYSES OF THE TEMPORAL EVOLUTION OF VOLCANIC CLOUDS. AN OPPORTUNITY TO EXPLORE THE POTENTIAL OF A NEW EARTH OBSERVATION PARADIGM AND ITS APPLICATION TO REMOTE SENSING OF VOLCANIC CLOUDS IS RARE. FROM L1 EPIC S OBSERVATION FREQUENCY IS INTERMEDIATE BETWEEN POLAR-ORBITING (LEO) AND GEOSTATIONARY (GEO) SENSORS BUT IS THE HIGHEST TEMPORAL RESOLUTION OF UV SATELLITE MEASUREMENTS ACHIEVED TO DATE. EPIC COVERS THE ENTIRE SUNLIT EARTH DISK AND MORE OF THE POLAR REGIONS THAN GEO SENSORS IN THE SUMMER MONTHS AND PARTLY FILLS A ~4-HOUR DAYTIME MEASUREMENT GAP BETWEEN OVERPASSES OF SUN-SYNCHRONOUS LEO WEATHER SATELLITES AT ~9:30 AM (E.G. THE EUROPEAN METOP-A/B SATELLITES) AND ~1:30 PM LOCAL TIME (E.G. NASA S AQUA AURA AND SUOMI-NPP SATELLITES) AND ALSO COLLECTS DATA LATER INTO THE AFTERNOON. UNDER PRIOR DSCOVR SCIENCE TEAM SUPPORT OUR GROUP HAS DEVELOPED AN EPIC SO2 RETRIEVAL ALGORITHM THAT HAS SUCCESSFULLY DETECTED AT LEAST 12 SIGNIFICANT VOLCANIC ERUPTIONS SINCE 2015. OUR SO2 TEAM AT MICHIGAN TECH AND NASA GSFC HAS UNIQUE MULTI-DECADAL EXPERIENCE IN MEASURING SO2 FROM VOLCANIC ERUPTIONS FROM SPACE USING UV SATELLITE INSTRUMENTS (HTTP://SO2.GSFC.NASA.GOV). IN THIS PROJECT WE PROPOSE TO CONTINUE DEVELOPMENT AND MAINTENANCE OF THE EPIC SO2 ALGORITHM AND DERIVED L2 PRODUCTS AND CONDUCT DETAILED VALIDATION AND SCIENTIFIC ANALYSIS OF EPIC SO2 AND AI RETRIEVALS FOLLOWING SEVERAL OF THESE AND FUTURE VOLCANIC ERUPTIONS TO DEMONSTRATE HOW THESE UNIQUE OBSERVATIONS CAN ADVANCE OUR UNDERSTANDING OF VOLCANIC CLOUD PROCESSES (E.G. THE LIFETIMES OF AND INTERACTIONS BETWEEN SO2 AND ASH ON HOURLY TIMESCALES) AND IMPACTS. WE PROPOSE THE FOLLOWING SPECIFIC ACTIVITIES UNDER THIS PROPOSAL: - CONTINUED MAINTENANCE OF THE DSCOVR/EPIC SO2 ALGORITHM AND PRODUCTION OF LEVEL 2 EPIC VOLCANIC SO2 AND AI DATA PRODUCTS FOR THE USER COMMUNITY; - EVALUATION AND VALIDATION OF EPIC SO2 AND AEROSOL INDEX (AI) DATA FOR VOLCANIC ERUPTIONS WITH OTHER LEO UV AND IR SATELLITE SO2 MEASUREMENTS (E.G. OMI OMPS AIRS); - SCIENTIFIC ANALYSIS OF EPIC SO2 AND AI DATA FOR A SELECTION OF WELL-CHARACTERIZED VOLCANIC ERUPTIONS (BOTH EXPLOSIVE AND EFFUSIVE) USING TRAJECTORY AND CHEMICAL-TRANSPORT MODELING; - PROMOTION AND PUBLIC DISSEMINATION OF THE UNIQUE CAPABILITIES OF EPIC OBSERVATIONS VIA WEBSITES AND SOCIAL MEDIA.