THIS PROPOSAL PROVIDES SIGNIFICANT RISK REDUCTION FOR THE ACTIVE SENSING OF CO2 EMISSIONS OVER NIGHTS DAYS AND SEASONS (ASCENDS) MISSION THROUGH ADVANCEMENT OF THE O2 TRANSMITTER AND THE ASSOCIATED ALGORITHMS TO COUPLE THE CO2 AND O2 INTEGRATED COLUMN MEASUREMENTS FOR RETRIEVAL OF DRY AIR MOLE FRACTION OF CO2 (XCO2). THIS RISK REDUCTION DIRECTLY ALIGNS WITH NASA'S PLAN FOR A CLIMATE-CENTRIC ARCHITECTURE, WHICH CALLS FOR THE ASCENDS MISSION TO FOLLOW OCO-2 IN THE 2019 LRD TIMEFRAME. THE PROPOSED METHODOLOGY IS TO LEVERAGE THE SIGNIFICANT PROGRESS MADE BY THE PROPOSING TEAM DURING A CURRENT 2008 ACT TO ACCOMPLISH THE FOLLOWING TASKS: 1) OPTIMIZE COMPOSITIONALLY ENGINEERED P2O5/F FIBERS TO ACHIEVE 5 W AVERAGE CW POWER AT>50% OPTICAL-TO-OPTICAL EFFICIENCY 2) EMPLOY FIBER IN A FIBER RAMAN AMPLIFIER (FRA) DEVELOPED UNDER CURRENT ACT FOR TEST 3) REPACKAGE AND INTEGRATE FRA INTO THE LASER ABSORPTION SPECTROMETER (LAS) ENGINEERING UNIT, CONDUCT FIELD TESTING, AND PREPARATION FOR AIRCRAFT FLIGHT OF OPPORTUNITY UNDER THE ACES IIP. 4) DEVELOPMENT AND APPLICATION OF THE ALGORITHMS REQUIRED FOR FIRST TIME ACTIVE DEMONSTRATION AND VALIDATION OF THE RETRIEVAL OF XCO2 USING GROUND AND AIRCRAFT FLIGHT DATA FROM THE O2 LAS SUBSYSTEM PRESENTLY, FRAS AT THE 1.26 MICRON WAVELENGTH ARE TRL-4 WHILE ALGORITHMS FOR THE FULL RETRIEVAL OF CO2 MIXING RATIO ARE TRL-3. THE PROPOSED EFFORT WILL ADVANCE THE O2 LAS COMPONENT FOR THE RETRIEVAL OF XCO2 TO TRL-5+, AND THE RETRIEVAL ALGORITHM/SOFTWAREPACKAGE DEVELOPED TO SUPPORT THE ASSESSMENT OF THE O2 LAS COMPONENT TO TRL-4 THROUGH INTEGRATED TESTING WITH THE CO2 LAS INSTRUMENT.THE BENEFITS OF THIS WORK INCLUDE ENABLING THE RETRIEVAL OF CO2 SOURCES AND SINKS OVER ALL LATITUDES TO IMPROVE GLOBAL MODELS FOR CLIMATECHANGE PREDICTION AND ENHANCING THE KNOWLEDGE BASE OF PRESSURE RETRIEVALS IN SPARSELY REPRESENTED REGIONS FOR IMPROVED NUMERICALWEATHER PREDICTION. (PERIOD OF PERFORMANCE IS 2/2012 - 9/2013)