SCIENCE GOALS AND OBJECTIVESTHE MERCURY ATMOSPHERIC AND SURFACE COMPOSITION SPECTROMETER (MASCS) ULTRAVIOLET AND VISIBLE SPECTROMETER (UVVS) ABOARD THE MERCURY SURFACE SPACE ENVIRONMENT GEOCHEMISTRY AND RANGING (MESSENGER) SPACECRAFT MEASURED EMISSION OF NA CA AND MG ROUTINELY FROM MARCH 2011-APRIL 2015 (17 MERCURY YEARS). MASCS UVVS OBSERVED SEASONAL VARIATIONS IN ALL THREE SPECIES THAT ARE SYSTEMATICALLY REPEATABLE FROM ONE YEAR TO THE NEXT. HOWEVER OBSERVATIONS OF EPISODIC BEHAVIOR FROM PROCESSES LINKED TO SPACE WEATHER EVENTS SUCH AS CORONAL MASS EJECTIONS (CME) AND LARGE IMPACTORS ARE ELUSIVE. THIS HAS BAFFLED THE MASCS UVVSSCIENCE TEAM. BECAUSE THE MASCS UVVS EXOSPHERIC DATASET IS SO RICH ONLY A PORTION OF THE DATA HAS BEEN ADEQUATELY EXPLORED AND STUDIED. THEREFORE WE PROPOSE TO SYSTEMATICALLY ANALYZE AND FURTHER EXPLORE THE MESSENGER MASCS EXOSPHERIC DATA IN SEARCH FOR EPISODIC BEHAVIOR AND UNDERSTAND THIS ELUSIVE SOURCE PROCESS. OUR EFFORT WILL BE COORDINATED WITH EPISODIC EVENT DATA FROM BOTH THEMAGNETOMETER (MAG) AND THE FAST IMAGING PLASMA SPECTROMETER (FIPS) ON MESSENGER.METHODOLOGYFIRST THE MASCS MAG AND FIPS DATA WILL BE OBTAINED FROM THE PDS FOR THE PERIOD UP TO THE SUBMISSION DATE OF THIS PROPOSAL. WE HAVE PROCESSING ROUTINES IN PLACE TO PARSE THE DATA OF INTEREST FROM THE CALIBRATED DATA RECORDS (CDRS) STORED ON THE PDS AND ORGANIZE THEM WITH POINTING INFORMATION BECAUSE MASCS UVVS HAS A LARGE SOLAR BACKGROUND AND THE OBSERVATIONAL GEOMETRY IS CONSTANTLYCHANGING THE DATA HAS TO BE CAREFULLY ANALYZED WITH TRAINED PERSONNEL SUCH AS OUR PROPOSAL TEAM. IT IS VERY EASY TO FALSELY IDENTIFY VARIABILITY THAT IS ACTUALLY ASSOCIATED WITH A CHANGING GEOMETRY RATHER THAN TO AN EPISODIC EVENT. BECAUSE THE PROPOSAL TEAM IS ALREADYVERY FAMILIAR WITH THE MESSENGER DATA WE HAVE AN ADVANTAGE THAT WE WILL BE PRODUCTIVE RIGHT AWAY WITH NO LEARNING CURVE. THE MASCS DATASET IS COMPLICATED BUT VERY RICH AND THERE ARE DATASETS THAT HAVE YET TO BE SYSTEMATICALLY ANALYZED. INCLUDING DATA IN THE CUSP REGIONS WHERE ION-RELATED EJECTION PROCESSES ARE THOUGHT TO CONTRIBUTE TO THE EXOSPHERE. TO HELP WITH OUR SEARCH WE WILL COORDINATE WITH BOTH THE MAG AND FIPS TEAM MEMBERS. THESE DATA WILL GUIDE US TO LOOK AT SPECIFIC DATES AND TIMES THAT SHOULD YIELDEPISODIC EXOSPHERE BEHAVIOR.RELEVANCETHE OBJECTIVE OF THE DISCOVERY DATA ANALYSIS PROGRAM (DDAP) IS TO ENHANCE THE SCIENTIFIC RETURN OF DISCOVERY PROGRAM MISSIONS. THIS WORK USES MESSENGER DATA IN THE PDS AT THE TIME OF THE PROPOSAL DUE DATE TO INCREASE OUR UNDERSTANDING OF PROCESSES THAT OCCUR AT THE MERCURYS SURFACE AND LINK THEM TO SPACE WEATHERING EVENTS.