This Phase II SBIR proposal is aimed at developing a non-invasive, optical method for monitoring crew member state of awareness in operational environments. All active devices used in this monitoring system will consist of commercially available components. Continuous monitoring of the mental state of personnel engaged in critical activities could provide a means of protection against human performance lapses resulting from unforeseen circumstances. If a deterioration of the state of awareness of an individual can be detected before that individual's performance is affected, serious accidents or lapses in operator performance could be avoided. A computer-controlled four-wavelength breadboard cerebral oxygen monitor was designed, fabricated, and demonstrated during Phase I. Using phantoms with controlled blood-oxygenation levels, high sensitivity and motion artifact rejection by proper algorithm use was demonstrated. Based on these successful Phase I results, Phase II will miniaturize the system size to a wearable format, and optimize the system performance. The new cerebral oxygen monitor performance will be evaluated, and more refined algorithms to eliminate motion artifacts will be developed. A portable, prototype version of this crew cerebral oxygen monitor will be designed, fabricated, evaluated, and delivered to NASA at the completion of the program.