NASA has researched the advantages of LED lighting systems within the spacecraft environment. The Solid-State Lighting Module (SSLM) is designed to replace a General Luminaire Assembly (GLA) unit on the International Space Station (ISS). Identical to the GLA in fit and form, the SSLM temporarily replaced a GLA on ISS. The crew was asked to complete a brief evaluation regarding the quality of the light output and the usefulness of the dimming feature. The SSLM measures 26.5″ x 6.6″ x 3.9″ and has a mass of approximately 7.5 pounds.
Three ground-based studies were completed on visual performance, color discrimination, and melatonin (melatonin promotes sleepiness) suppression in healthy human subjects under different SSLA light exposure conditions inside a high-fidelity replica of the ISS crew quarters (CQ). Color discrimination tests showed no significant differences in color discrimination for indirect daylight, fluorescent room light, and SSLA light in the CQ. Also, there were no significant differences in score or time for subjects performing contrast tests. Presently, the data demonstrate that bright white Solid-State Lighting Module-Research (SSLM-R) light supports visual performance and color discrimination equivalently to typical indoor exposures to indirect daylight and overhead fluorescent light. In addition, increasing exposures to SSLA inside the CQ elicit increasingly stronger melatonin suppressions in healthy volunteers. The findings demonstrate the feasibility of doing controlled studies on visual, neuroendocrine and circadian responses in a high fidelity replica of an ISS component.
Early studies represent a start towards quantifying the broader range of visual, biological and behavioral responses to light once the current fluorescent lighting system is replaced by solid-state lighting. The data reported here begin to address long-duration space exploration, and the rapid development of solid-state lighting that will ultimately revolutionize how our public facilities, work places and homes are illuminated in the coming decades. Similar to some of the astronauts, a significant portion of the global population suffers from chronic sleep loss or circadian-related disorders. By refining multipurpose lights for astronaut safety, health and well-being in spaceflight, the door is opened for new lighting strategies that can be evolved for use on Earth.