SLEEP IS CENTRAL PHYSIOLOGICAL REGULATOR OF COGNITIVE / BEHAVIORAL NEUROPHYSIOLOGICAL AND IMMUNE FUNCTIONS. THEREFORE STUDY OF SLEEP QUALITY AND DURATION ON ORBIT MAY YIELD IMPORTANT INSIGHTS INTO ETIOLOGY AND MECHANISMS OF ADVERSE COGNITIVE/BEHAVIORAL SPACEFLIGHTASSOCIATED NEURO-OCULAR SYNDROME (SANS) AND IMMUNOLOGICAL RESPONSES DURING LONG DURATION DEEP SPACE EXPLORATION MISSIONS. WE THEREFORE PROPOSE TO USE AN INTEGRATED APPROACH COMBINING ASSESSMENTS OF (1) SLEEP QUALITY AND DURATION (2) INTRACRANIAL FLUIDS DISTRIBUTION (3) COGNITIVE PERFORMANCE AND (4) IMMUNOLOGICAL RESPONSE (5) CHANGES IN THESE PHYSIOLOGICAL MEASURES RELATIVE TO SLEEP QUALITY AND DURATION. WE PROPOSE TO COLLECT DATA ON CREWMEMBERS PARTICIPATING IN INTEGRATED ONE-YEAR MISSION PROJECT (I1YMP) ABOARD THE INTERNATIONAL SPACE STATION (ISS) AND DEMOGRAPHICALLY MATCHED CONTROL SUBJECTS IN HUMAN EXPLORATION RESEARCH ANALOG (HERA) FOR MISSIONS OF SIMILAR DURATIONS. WE WILL ACHIEVE THE PROPOSED GOALS THROUGH THESE SPECIFIC AIMS: AIM 1: CHARACTERIZE COGNITIVE TASK PERFORMANCE CHANGES DURING THE INTEGRATED 1 YEAR MISSION PROJECT ON THE ISS; AIM 2: CHARACTERIZE BRAIN AND SYSTEMIC PHYSIOLOGY CHANGES DURING 1YMP ON THE ISS; AIM 3: CHARACTERIZE THE EFFECTS OF SLEEP DURATION AND QUALITY ON CEREBRAL HEMODYNAMICS ON ISS AND IN HERA; AIM 4: QUANTIFY THE EFFECTS OF SLEEP DURATION AND QUALITY ON IMMUNE RESPONSE. THE OUTCOMES OF THE STUDY WILL CONTRIBUTE TO QUANTIFICATION OF CREW HEALTH AND PERFORMANCE RISKS ASSOCIATED WITH HUMAN SPACEFLIGHT AND AID IN DEVELOPMENT OF TECHNOLOGIES FOR MONITORING AND MITIGATING CREW HEALTH AND PERFORMANCE.