SANS REMAINS AN IMPORTANT AND UNMITIGATED RISK TO LONG-DURATION SPACEFLIGHT. CURRENT HYPOTHESES SUGGEST THAT THE LACK OF GRAVITY LEADS TO FLUID SHIFTING TOWARDS THE HEAD RESULTING IN CONGESTION AND/OR ELEVATED PRESSURES IN THE CRANIAL VASCULAR AND/OR LYMPHATIC COMPARTMENTS. NASA IS PROPOSING TO CONDUCT 30-DAY HEAD-DOWN TILT (HDT) EXPERIMENTS TO TEST SANS COUNTERMEASURES AT THE ENVIHAB FACILITY IN COLOGNE GERMANY. WE PROPOSE TO PROVIDE NUMEROUS KEY MEASUREMENTS IN SUPPORT OF THESE PLANNED 30-DAY MISSIONS. WE WILL FOCUS IN PARTICULAR ON PROVIDING A TOOLKIT FOR DETAILED NEUROPHYSIOLOGICAL AND FLUID SHIFT ASSESSMENT AND MONITORING SUITABLE FOR MEASURING BOTH SANS- AND COUNTERMEASURE-RELATED CHANGES. THESE TOOLS WILL BE DESIGNED TO COMPLEMENT THE STANDARD OCULAR MEASURES USED FOR SANS DIAGNOSIS AND MONITORING (E.G. OCT OCULAR US FUNDOSCOPY VISUAL ACUITY).