THIS PROPOSED RESEARCH IS A NEW JOINT ANALYSIS OF PLANCK AND DARK ENERGY SURVEY (DES) DATA IN AN APPROXIMATE BAYESIAN FRAMEWORK THAT CAN PROPERLY TAKE INTO ACCOUNT CORRELATIONS AND SHARED SYSTEMATICS BETWEEN PROBES. THE FIRST PART OF THE PROPOSAL IS A REANALYSIS OF PLANCK DATA PERFORMED IN A BASIS MORE DIRECTLY COMPARABLE TO LARGE SCALE STRUCTURE (LSS) DATA AND WITHOUT THE SAME ASSUMPTIONS ABOUT THE SHAPE OF THE LIKELIHOOD FUNCTIONS OF COSMIC MICROWAVE BACKGROUND (CMB) POWER SPECTRA. THE SECOND PART IS AN INTEGRATION OF CMB SIMULATION SOFTWARE INTO COSMOLIKE THE PI AND CO-I S BAYESIAN ANALYSIS FRAMEWORK AND A JOINT ANALYSIS OF PLANCK AND DES DATA USING THAT SOFTWARE. THIS EFFORT WILL ALSO INVOLVE THE ESTIMATION OF CORRELATED SYSTEMATICS BETWEEN THE CMB AND LSS DATA AND IT WILL LEAD TO SIGNIFICANTLY STRONGER CONSTRAINTS ON COSMOLOGICAL MODELS INCLUDING EXTENSIONS TO THE LAMBDA-COLD DARK MATTER (LCDM) COSMOLOGICAL MODEL.