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 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 (Brainard 2012).
PUBLICATION(S)
Brainard GC, Coyle W, Ayers M, et al. Solid-state lighting for the International Space Station:
Tests of visual performance and melatonin regulation. Acta Astronautica. 2012. doi:
10.1016/j.actaastro.2012.04.019.
This investigation is complete and all results are published.