Solid State Lighting Module, SDTO 15008U (SSLM) - 02.25.15

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
The Solid-State Lighting Module (SSLM), SDTO 15008U is a Station Development Test Objective (SDTO) sponsored by the National Aeronautics and Space Administration (NASA) to demonstrate the advantages of Light-Emitting Diode (LED) lighting systems within the spacecraft environment.
Science Results for Everyone
Let there be (better) light! Light-Emitting Diode (LED) lights are energy efficient, last longer and have no potentially toxic mercury vapor, important advantages over fluorescent lighting. Data from a prototype installed on the station indicate that LEDs are the same as typical indirect daylight and overhead fluorescent light as far as providing light for visual performance and color discrimination. In addition, LEDs suppress melatonin, which could help to better manage circadian rhythms, hence provide better sleep on the station. This technology will not only help long-duration space exploration, it will improve lighting and help those who suffer sleep disorders on Earth.   

The following content was provided by Daniel Shultz, and is maintained in a database by the ISS Program Science Office.
Experiment Details


Principal Investigator(s)

  • Daniel Shultz, Kennedy Space Center, Cape Canaveral, FL, United States

  • Co-Investigator(s)/Collaborator(s)
    Information Pending

    NASA Kennedy Space Center, FL, United States

    Sponsoring Space Agency
    National Aeronautics and Space Administration (NASA)

    Sponsoring Organization
    Human Exploration and Operations Mission Directorate (HEOMD)

    Research Benefits
    Information Pending

    ISS Expedition Duration
    October 2008 - April 2009

    Expeditions Assigned

    Previous ISS Missions
    SSLM is a unique SDTO which has not been performed in microgravity.

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    Experiment Description

    Research Overview

    • The Solid-State Lighting Module (SSLM), SDTO 15008U is a Station Development Test Objective (SDTO) designed to demonstrate the advantages of Light-Emitting Diode (LED) lighting systems for the spacecraft environment.

    The Solid-State Lighting Module (SSLM), SDTO 15008U is a Station Development Test Objective (SDTO) sponsored by the National Aeronautics and Space Administration (NASA) designed to replace a General Luminaire Assembly (GLA) unit already in use on the International Space Station (ISS). The SSLM is identical to the GLA in fit and form. The SSLM will temporarily replace a GLA on ISS. The crew will be 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.

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    Space Applications
    SSLM on the ISS will begin the evaluation of LED lighting systems for the next generation of crew exploration vehicles. SSLM will effectively evaluate potential savings of LED technology vs. currently installed systems.

    Earth Applications
    Analysis of the crew evaluations will be presented to NASA several boards after data return. A final report will be completed and archived for use in design of lighting systems in the next generation of exploration vehicles.

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    Operational Requirements
    The SSLM requires the +120 VDC power supply of the GLA. The continuous and peak power requirement is 30W. The crewmember will transfer the SSLM to a stowage location on ISS. To complete the SSLM on-orbit operations, the crewmember will remove the pre-existing GLA, transfer the GLA to a stowage location, remove the SSLM from its stowage location, transfer the SSLM to the mounting location, and install it. The SSLM installation procedures will be identical to the GLAs to eliminate the need for additional tools or training.

    There will be a ten-minute crew evaluation to rate the quality of the SSLM light output, the usefulness of the dimming feature and the ease of installation and removal. The SSLM will be removed from its GLA location following completion of the evaluation.

    Operational Protocols
    The SSLM requires transfer to the mounting location, installation of the SSLM into the mounting location, and removal of the SSLM from the mounting location upon completion. The evaluation should be completed by a minimum of two crewmembers in one session each. Additional sessions are welcome based on crew availability and time.

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    Results/More Information

    The new solid-state lighting technology provides an important opportunity for re-lamping of the ISS with an energy efficient lighting system that has a significantly longer life span and does not contain potentially toxic mercury vapor. A prototype Solid-State Lighting Assembly (SSLA) was developed at Kennedy Space Center and successfully installed on the ISS during Expedition 18. This new lighting system will provide multiple settings that can support astronaut vision and potentially serve as a lighting countermeasure for sleep and circadian disruption aboard the ISS.

    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 (Brainard et al. 2012).

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    Results Publications

      Brainard GC, Coyle W, Ayers M, Kemp J, Warfield B, Maida JC, Bowen C, Bernecker C, Lockley SW, Hanifin JP.  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.

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    Ground Based Results Publications

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    ISS Patents

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    Related Publications

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    Related Websites

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    image Flight unit Solid State Lighting Module (SSLM) at Kennedy Space Center. Image courtesy of Kennedy Space Center.
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    image (Top) SSLM with LED diffuser attached and (bottom) LED board without LED diffuser attached. Image courtesy of Kennedy Space Center.
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    image NASA Image: ISS018E010657 - View of Michael Fincke holding a General Luminaire Assembly (GLA) in Node 2.
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