This project will achieve a wrist-worn actigraphy device called STARwatch, designed specifically for space exploration environments. It will provide a minimally obtrusive, objective measure that evaluates astronaut sleep-wake activity and light exposure. This project will leverage our second-generation actigraphy device that has already been validated in controlled laboratory experiments against gold-standard polysomnography. The compact wrist-worn device includes sensors to collect sleep metrics and will also serve as a wireless hub to collect real-time physiological data from other body-worn sensors (e.g., heart rate, EEG). It will use standardized wireless communication protocols (e.g., Bluetooth) to automatically uplink data to the ISS network (no astronaut time required). Data will automatically be integrated into medical operations support systems adhering to NASA data requirements (e.g., HL7), providing immediate feedback to astronauts and flight surgeons to aid in decision-making relative to astronaut medical, behavioral health and performance issues. During Phase II, we will conduct user testing and validation in a space flight analog environment, complete product refinements, and certify STARwatch for spaceflight. (Phase II TRL of 7-8).