Light exposure is a requirement for all spaceflight and base missions and careful consideration is required to provide light of sufficient quality and quantity to ensure adequate vision and to optimize the circadian, neuroendocrine, and neurobehavioral effects of light, and ultimately crew health and safety. The requirement to replace the out-of-date fluorescent lighting onboard ISS has provided an opportunity to re-fit the ISS with the latest in solid-state lighting technology which has the capability to provide light of varying spectrum, intensity, and pattern. While ours and others' work has established blue and blue-enriched light as optimal to enhance circadian entrainment and alertness, final ground-based testing in high-fidelity analogs is required to develop guidelines for operational use prior to flight testing. The proposed study will provide the ground-based data necessary to inform guidelines for flight testing the new lighting source, in time for the fluorescent light replacement in 2015. The proposal specifically targets lighting countermeasures to address circadian misalignment and performance decrements during a slam-shift, which is a common requirement during Soyuz docking, and to enhance sleep and alertness during both slam-shift and normal operations. Without such data, future recommendations for operational deployment of the Solid State Lighting Assemblies (SSLAs) will be suboptimal. The Earth-based applications and commercialization potential of these studies are enormous. The slam-shifts aboard ISS, and the consequences to sleep, circadian rhythms, performance, and health, are very similar to that experienced by the 15M Americans who do shiftwork. The World Health Organization recently designated shiftwork that involves circadian desynchrony as a probable carcinogen and shift-workers also have high rates of night-time accidents and injuries, cardiovascular disease, and diabetes. Similar lighting interventions could be deployed for night shift-workers using the same Dynamic Lighting Schedule (DLS) which would have the benefit of improving productivity and safety while also reducing energy use by using targeted light spectra that only provide the light needed. Many non shift-workers also suffer circadian misalignment and performance problems, for example the early-riser workforce, school and college students, professions requiring long work hours etc., and would benefit from a similar DLS. Patients in hospitals and care homes are also often exposed to poor light-dark patterns, correction of which has recently been shown to slow the rate of cognitive decline in dementia. Anywhere where high levels of alertness, performance, and vigilance are required are target sites for such lighting interventions and provide enormous potential for commercialization.