SIGNIFICANCE: HALF OF THE SOLAR ENERGY RECEIVED BY VENUS IS ABSORBED IN THE ULTRAVIOLET (UV) BY A STILL UNKNOWN ABSORBER SITUATED AT THE TOP OF THE PLANET CLOUDS LAYER. WHAT IS IT? WHAT IS ITS NATURE AND WHY DOES IT ABSORB SO MUCH? THIS IS STILL ONE OF THE MOST IMPORTANT BUT UNANSWERED QUESTIONS ABOUT OUR HOT AND AMAZING TWIN PLANET! PREVIOUS GROUND BASED AND SPACE BASED OBSERVATIONS DID NOT PRODUCE A HIGH SPECTRAL RESOLUTION AND LOW NOISE BROAD UV SPECTRUM OF VENUS! VENUS STRONG UV ABSORBER IN ITS CLOUDS TOP DRIVES VENUS THERMAL RADIATIVE BALANCE PRODUCES HIGH CONTRAST FEATURES AND ITS NATURE IS STILL UNKNOWN. MISSION CONCEPT: CUVE - CUBESAT UV EXPERIMENT ON AN INCLINED POLAR ORBIT AROUND VENUS WILL OBSERVE NADIR IN THE DAYSIDE AND NIGHTSIDE. PAYLOAD AND OBJECTIVES: THE CUBESAT UV EXPERIMENT (CUVE) WILL INVESTIGATE VENUS ATMOSPHERE WITH TWO ON-BOARD SCIENCE PAYLOADS (I) A HIGH SPECTRAL RESOLUTION (0.3 NM) UV SPECTROMETER COVERING 190-570 NM AND (II) A BROADBAND UV CAMERA WITH SPECTRAL RANGE CENTERED ON THE UNKNOWN ABSORBER AT 365 NM. (I) CUVE SPECTROMETER WILL: OBSERVE VENUS DAYSIDE UV ALBEDO SPECTRUM (SOLAR LIGHT SCATTERED BACK FROM THE CLOUDS) TO RESOLVE THE SO AND SO2 BANDS AND RETRIEVE THE COMPOSITION OF THE UV-BLUE ABSORBER AT 365 NM; OBSERVE VENUS NIGHTSIDE TO DETECT NIGHTGLOWS: NO (190-300NM) CO (205-240NM) O2 (400-500NM). (II) CUVE CAMERA WILL ADD CONTEXTUAL INFORMATION AND CAPTURE THE UV CONTRAST FEATURES TO DERIVE THE ABSORBER DISTRIBUTION AND THE CLOUDS TOP STRUCTURE AND DYNAMICS. THE ANALYSIS CORRELATION AND COMPARISON OF MEASUREMENTS WITH MODELS WILL DETERMINE THE ORIGIN OF THE UV ABSORBER AND INVESTIGATE THE PHYSICS AND CHEMISTRY OF VENUS ATMOSPHERE. RELEVANCE: THE STUDY OF VENUS IS PART OF THE THREE MAJOR CLASSES OF MISSION DESTINATIONS OF THE 2014 NASA SCIENCE PLAN - PLANETARY SCIENCE DIVISION INNER PLANETS: EARTH S MOON MARS AND ITS SATELLITES VENUS AND MERCURY. A UV INVESTIGATION IS ALSO PART OF THE DECADAL SURVEY AND THE VENUS EXPLORATION ANALYSIS GROUP (VEXAG I.B.1-2 I.C.1-2). IMPACT: WE WILL PRODUCE THE FIRST BROAD SPECTRAL RANGE (190 - 570 NM) HIGH SPECTRAL RESOLUTION (0.3 NM) HIGH SPATIAL RESOLUTION (50 KM) UV SPECTRUM OF VENUS WHICH WILL FINALLY CHARACTERIZE THE NATURE OF THE COMPONENTS IN ITS ATMOSPHERE THAT ABSORB IN THE UV. SINCE THE MAXIMUM ABSORPTION OF SOLAR ENERGY BY VENUS OCCURS IN THE UV DETERMINING THE NATURE CONCENTRATION AND DISTRIBUTION OF THE UNKNOWN UV ABSORBER WILL INCREASE THE UNDERSTANDING THE OVERALL RADIATIVE AND THERMAL BALANCE OF THE PLANET IN PARTICULAR THE ATMOSPHERIC DYNAMICS AND THE CHEMISTRY OF THE UPPER CLOUDS. THE UV CAMERA WITH HIGH SPATIAL RESOLUTION OF 1 KM WILL PROVIDE CONTEXTUAL INFORMATION AND PROVIDE IMAGES FOR CLOUD STRUCTURE AND DYNAMICS STUDIES. THIS MISSION STUDY WILL ALSO IDENTIFY MISSION CRITICAL TECHNOLOGY RELEVANT TO OTHER FUTURE PLANETARY CUBESAT MISSIONS. TEAM: OUR TEAM HAS DECADES OF EXPERIENCE RELEVANT TO THIS PROJECT. IT INCLUDES EXPERTS IN: VENUS ATMOSPHERE AND RADIATIVE TRANSFER (PI COTTINI COI PICCIONI - PI OF ESA/VENUSEXPRESS VIRTIS INSTRUMENT COLL. IGNATIEV - ESA/VENUSEXPRESS VMC INSTRUMENT COI COI HEWAGAMA) DESIGN FABRICATION AND OPERATION OF SPECTROMETERS FOR REMOTE SENSING (COI ASLAM AND GORIUS). OUR TEAM WILL ALSO BENEFIT FROM COLL. GLAZE S EXPERIENCE ON VENUS MISSION CONCEPT FORMULATION STUDIES. WE WILL DEVELOP CUVE MISSION PLANNING AND DESIGN CONCEPT IN COLLABORATION WITH THE GODDARD SPACE FLIGHT CENTER S MISSION PLANNING LAB (MPL) AND THE MISSION DESIGN LAB (MDL). OUR SCIENCE AND ENGINEERING TEAM IS THEREFORE UNIQUELY QUALIFIED FOR THIS INVESTIGATION.