OUR PROPOSED RESEARCH WILL USE A COMBINATION CHANDRA X-RAY DATA ALONG WITH PLANCK AND GROUND-BASED SZ OBSERVATIONS TO OBTAIN AN ACCURATE RECONSTRUCTION OF CLUSTER PRESSURE PROFILES FROM THE CORE REGION TO BEYOND THE VIRIAL RADIUS IN A SET OF 45 GALAXY CLUSTERS. WE WILL OBTAIN BOTH PARAMETRIC AND NON-PARAMETRIC RECONSTRUCTIONS OF THE PROFILES FOR EACH CLUSTER ALONG WITH ENSEMBLE MEAN PROFILES AND THE INTRINSIC CLUSTER-TO-CLUSTER SCATTER ABOUT THE MEAN. SIMULATIONS INDICATE THAT THESE PROFILES SHOULD DEVIATE FROM A SELF-SIMILAR SHAPE WITH THE DEVIATIONS RESULTING FROM PHYSICAL PROCESSES RELATED TO CLUSTER GROWTH AND EVOLUTION SUCH AS AGN FEEDBACK AND THERMALIZATION OF ACCRETED MATERIAL. OUR WORK WILL PROVIDE QUANTITATIVE OBSERVATIONAL TESTS OF THE SIMULATION-BASED PREDICTIONS PARTICULARLY IN THE SPARSELY STUDIED OUTER REGIONS OF THE CLUSTER NEAR THE VIRIAL RADIUS THUS PROVIDING A BETTER UNDERSTANDING OF THE UNDERLYING PHYSICS. FOR EXAMPLE SIMULATIONS INDICATE THAT THE OUTER PRESSURE PROFILE SHOULD FLATTEN WITH DECREASING CLUSTER MASS AS A RESULT OF THE INCREASING RELATIVE IMPACT OF FEEDBACK MECHANISMS. AS ANOTHER EXAMPLE THE PREVALENCE OF DENSE GAS CLUMPS AND NON-THERMAL MOTIONS IN THE OUTER CLUSTER REGIONS IS EXPECTED TO INCREASE WITH REDSHIFT RESULTING IN A STEEPENING OF THE PRESSURE PROFILE. GIVEN OUR EXPECTED SENSITIVITIES ALONG WITH THE MASS AND REDSHIFT RANGES WITHIN OUR CLUSTER SAMPLE WE EXPECT TO MEASURE BOTH OF THESE TRENDS AT HIGH SIGNIFICANCE. FURTHERMORE WE WILL ANALYZE MOCK OBSERVATIONS OF SIMULATED CLUSTERS MATCHING THE SELECTION CUTS OF THE OBSERVATIONAL DATA WHICH WILL ALLOW US TO ACCOUNT FOR ANY POSSIBLE BIASES IN OUR ANALYSIS AND TO MAKE A DIRECT COMPARISON TO THE SIMULATION-BASED PREDICTIONS. OUR PROPOSED RESEARCH WILL FURTHER OUR UNDERSTANDING OF THE PHYSICAL PROCESSES RELATED TO CLUSTER GROWTH. THIS WORK WILL THEREFORE HELP TO ADDRESS SEVERAL QUESTIONS CALLED OUT IN THE NASA PCOS PROGRAM BOTH DIRECTLY AND BY BETTER CALIBRATING CLUSTERS FOR COSMOLOGICAL SURVEYS.