The ISS Dynamic Lighting Schedule: An In-Flight Lighting Countermeasure to Facilitate Circadian Adaptation, Improve Sleep and Enhance Alertness and Performance on the International Space Station
Steven W. Lockley, Ph.D.
Harvard - Brigham and Women's Hospital
Spaceflight often exposes crews to unusual light-dark and work schedules that lead to misalignment of the circadian pacemaker, resulting in poor sleep, impaired alertness and increased risk of fatigue-related accidents. Recently, this project’s researchers and others have shown that short-wavelength (blue) light is the most effective wavelength for phase-shifting the circadian pacemaker and enhancing alertness and performance. In addition to permitting vision, light also therefore has the potential to be a safe, non-pharmacological countermeasure to reduce the risk of circadian misalignment and performance deficits during spaceflight. Using blue light alone, however, is undesirable as it impairs visual function. Manipulation of the blue light content of white light has similar benefits to blue light and provides a way to optimize both the visual and non-visual responses to light simultaneously.
A unique opportunity has arisen with the need to replace the current lighting aboard the International Space Station. NASA has proposed a new solid state lighting system with three pre-determined settings to address different operational needs: 1) white light for general vision; 2) blue-enriched white light to enhance high circadian adaptation and alertness; and, 3) blue-depleted white light to minimize alertness prior to sleep. The researchers have developed a Dynamic Lighting Schedule that determines when each of these three settings will be used to optimize lighting to maintain visual function and as a countermeasure to facilitate circadian adaptation, improve alertness and performance and enhance sleep.
The current project is studying how the new lights would be used operationally to address the problems associated with a slam shift, which is a common requirement during ISS operations, in a high-fidelity simulation of the ISS lighting environment, sleep patterns, and work schedule. The study will provide the data necessary to inform the operational guidelines for in-flight testing of the new light source.