THE AEROSOL CLOUD METEOROLOGY INTERACTIONS OVER THE WESTERN ATLANTIC EXPERIMENT (ACTIVATE) IS A PROPOSED NASA EARTH VENTURE SUBORBITAL-3 PROGRAM. ACTIVATE WILL ACQUIRE A UNIQUE EXTENSIVE IN SITU AND REMOTE SENSING DATASET OF AEROSOLS MBL CLOUDS AND METEOROLOGICAL CONDITIONS FROM 150 PLANNED AIRCRAFT FLIGHTS TO ADDRESS THE FOLLOWING THREE SCIENCE OBJECTIVES (BASELINE AND THRESHOLD SCIENCE OBJECTIVES ARE IDENTICAL): OBJECTIVE 1. QUANTIFY RELATIONSHIPS BETWEEN AEROSOL NUMBER CONCENTRATION (NA) CLOUD CONDENSATION NUCLEI (CCN) CONCENTRATION AND CLOUD DROP NUMBER CONCENTRATION (ND) AND REDUCE UNCERTAINTY IN MODEL PARAMETERIZATIONS OF CLOUD DROPLET ACTIVATION. OBJECTIVE 2. IMPROVE PROCESS-LEVEL UNDERSTANDING AND MODEL REPRESENTATION OF FACTORS THAT GOVERN CLOUD MICRO/MACRO-PHYSICAL PROPERTIES AND HOW THEY COUPLE WITH CLOUD EFFECTS ON AEROSOL. OBJECTIVE 3. ASSESS ADVANCED REMOTE SENSING CAPABILITIES FOR RETRIEVING AEROSOL AND CLOUD PROPERTIES RELATED TO AEROSOL-CLOUD INTERACTIONS. ACTIVATE WILL DEPLOY TWO AIRCRAFT OVER THE WESTERN NORTH ATLANTIC OCEAN - THE NASA LARC HU-25 FALCON AND B-200 KING AIR. THE HU-25 ACQUIRES IN SITU MEASUREMENTS BELOW IN AND ABOVE CLOUDS. THE B-200 FLIES ABOVE CLOUDS TO REMOTELY MEASURE AEROSOLS AND CLOUDS USING THE HIGH SPECTRAL RESOLUTION LIDAR-2 (HSRL-2) THE RESEARCH SCANNING POLARIMETER (RSP) AND DEPLOYS DROPSONDES TO MEASURE THE ATMOSPHERIC STATE. ACTIVATE IS A FOUR-YEAR PROGRAM (FY2019-FY2023) WITH TWO FIELD DEPLOYMENTS IN EACH YEAR OF 2020 2021 2022 FOR A TOTAL OF SIX DEPLOYMENTS.