THE MERCURY SURFACE SPACE ENVIRONMENT GEOCHEMISTRY AND RANGING (MESSENGER) MISSION WAS THE FIRST SPACECRAFT TO ENTER ORBIT AROUND MERCURY AND CONDUCT GLOBAL MAPPING OF THE PLANET ELUCIDATING MANY OUTSTANDING ISSUES ABOUT THE PLANET'S COMPOSITION STRUCTURE SHAPE AND ENVIRONMENT. ONE OF THE MANY OBJECTIVES OF MESSENGER WAS TO DETERMINE THE PLANET'S GRAVITY FIELD AND ITS TOPOGRAPHY. A JOINT ANALYSIS OF THESE DATA SETS PROVIDES A POWERFUL METHOD TO PROBE THE INTERIOR STRUCTURE OF A PLANET SINCE THE GRAVITY FIELD DEPENDS ON THE DENSITY DISTRIBUTION. THE MESSENGER SPACECRAFT WAS IN AN ECCENTRIC ORBIT AROUND MERCURY WITH ITS PERICENTER LOCATED OVER THE NORTHERN HEMISPHERE. IN MESSENGER S SECOND EXTENDED MISSION (MARCH 2013 UNTIL APRIL 2015) ALTITUDES AS LOW AS 15 25 KM ABOVE THE SURFACE OF MERCURY WERE ACHIEVED RESULTING IN A WEALTH OF INFORMATION ABOUT THE GRAVITY FIELD AT SMALL SCALES. HOWEVER THE SPATIAL RESOLUTION OF THE TRACKING DATA VARIES WIDELY GEOGRAPHICALLY WITH THE BEST RESOLUTION IN THE NORTHERN HEMISPHERE. SUCH A VARYING RESOLUTION REQUIRES SMOOTHING OF THE ESTIMATED GRAVITY FIELD WHICH RESULTS IN SUPPRESSING SHORT-WAVELENGTH SIGNALS. CURRENT GLOBAL GRAVITY MODELS CAN THEREFORE ONLY BE USED TO INTERPRET LONG-WAVELENGTH SIGNALS DESPITE USING ALL THE DATA. WE PROPOSE TO ANALYZE THE MESSENGER TRACKING DATA INTO HIGH-RESOLUTION GRAVITY FIELD MODELS WITH A METHOD BASED ON LINE-OF-SIGHT (LOS) ACCELERATIONS THAT HAS BEEN SHOWN TO RESULT IN MODELS WITH IMPROVED CORRELATIONS WITH TOPOGRAPHY. WE WILL ALSO USE LOS DATA TO ESTIMATE LOCAL VARIATIONS IN CRUSTAL DENSITY. WE WILL USE THESE COMBINED RESULTS TO PERFORM A SPECTRAL ANALYSIS OF MERCURY'S GRAVITY AND TOPOGRAPHY. FROM THE CORRELATION OF GRAVITY AND TOPOGRAPHY AND FROM THE RATIO OF THESE QUANTITIES CALLED THE ADMITTANCE WE WILL DETERMINE THE THICKNESS OF THE LITHOSPHERE THE OUTERMOST LAYER OF A PLANET. THIS WILL PROVIDE NEW CONSTRAINTS ON MODELS OF THE INTERIOR OF MERCURY AND OF OTHER TERRESTRIAL PLANETS. WE WILL LEVERAGE OUR EXPERIENCE IN PROCESSING THE MESSENGER TRACKING DATA WITH OUR ANALYSIS SOFTWARE GEODYN II AS WELL AS OUR TEAM'S EXPERIENCE IN INTERPRETING THE GRAVITY AND TOPOGRAPHY DATA. WE WILL ANALYZE THE MESSENGER TRACKING DATA WITH A METHOD THAT TRANSFORMS THE TRACKING DATA INTO LINE-OF-SIGHT ACCELERATIONS. WE SHOW THAT THIS WILL IMPROVE THE CORRELATIONS WITH TOPOGRAPHY ESPECIALLY FOR AREAS WHERE LOW-ALTITUDE TRACKING DATA ARE AVAILABLE. ALTHOUGH THE TRUE CORRELATION OF GRAVITY AND TOPOGRAPHY IS GENERALLY LESS THAN UNITY AN IMPROVED CORRELATION STRONGLY INDICATES A REDUCTION OF NOISE IN THE NEW GRAVITY FIELD. WE WILL THEN APPLY EXISTING METHODS BASED ON THE ADMITTANCE AND CORRELATION BETWEEN GRAVITY AND TOPOGRAPHY TO DETERMINE THE PROPERTIES OF MERCURY'S CRUST AND LITHOSPHERE. OUR NEW TREATMENT OF NOISE IN THE ADMITTANCE STUDY WILL BE AN IMPORTANT IMPROVEMENT UPON PREVIOUS STUDIES AS IT IS SHOWN TO MATCH THE DATA BETTER THAN PREVIOUS THEORETICAL STUDIES CAN. OUR PROPOSAL IS HIGHLY RELEVANT TO THE DISCOVERY DATA ANALYSIS PROGRAM. WE USE PUBLICLY AVAILABLE DATA FROM THE MESSENGER MISSION (CONSISTING OF BOTH TRACKING DATA AND PUBLISHED GRAVITY AND TOPOGRAPHY MODELS) AND OUR ANALYSIS WILL RESULT IN AN ENHANCED SCIENCE RETURN OF THIS MISSION. WE WILL ARCHIVE UPDATED GRAVITY MODELS AND MAPS. OUR PROPOSED ANALYSIS ALSO ADDRESSES ONE OF THE FUNDAMENTAL SCIENCE GOALS AS STATED IN NASA'S DECADAL SURVEY FOR PLANETARY SCIENCE NAMELY "UNDERSTANDING THE ORIGIN AND DIVERSITY OF TERRESTRIAL PLANETS". OUR PROPOSED ANALYSIS WILL ACHIEVE IMPROVED CONSTRAINTS ON THE COMPOSITION AND NEAR-SUBSURFACE STRUCTURE OF MERCURY AND WILL THEREFORE IMPACT OUR UNDERSTANDING OF THE ORIGIN AND CONSEQUENT EVOLUTION OF THE PLANET.