Working draft 02 · Yuji graphics are temporary. Expand any box to explore.
A morning signal
Light helps synchronise our roughly 24-hour body clock. Morning exposure can help anchor that rhythm to the day. Timing should follow the person’s sleep schedule.
A brighter day
Daytime light provides a stronger signal for wakefulness. Spectrum, intensity at the eye and duration all contribute; the colour of the light alone is not enough.
A quieter evening
Lower melanopic exposure towards bedtime helps preserve the contrast between day and night. Night lighting should stay low while supporting safe movement. The diagram illustrates Yuji’s approach, not a prescribed schedule or SAGA specification.
01 / The body clock
Your eyes do more than see.
How light reaches the body clock
Light-sensitive retinal cells called ipRGCs send information to the brain’s circadian clock. This pathway helps coordinate sleep and wakefulness alongside other daily processes. It works alongside the rods and cones used for vision. Both daytime light and nighttime darkness matter.
02 / Spectrum
Same brightness.
Different signals.
Incandescent light
Daylight
What we see and what our body clock senses are different.
Why the spectrum matters
Different wavelengths contribute differently to vision and melanopic response. Melanopic daylight efficacy ratio (m-DER) compares melanopic content per lux with standard daylight, D65. A value of 1 matches that reference weighting; it does not guarantee identical effects on sleep. These source charts illustrate spectral differences, not measurements of SAGA’s light. Their M/P labels are not m-DER values.
03 / Exposure
The light has to reach you.
At the same 200 lux at the eye
m-DER 0.5
100 lux m-EDI
m-DER 1.0
200 lux m-EDI
Illustrative calculation, not an ISS measurement.
Spectrum × light at the eye = melanopic exposure
Melanopic equivalent daylight illuminance (m-EDI) equals m-DER multiplied by illuminance at the eye. Position, direction and the person’s view all matter: a bright desk does not necessarily mean bright light at the eyes. This example uses Yuji’s formula; it is not a recommended dose. Timing and duration still matter.
04 / SAGA in space
A day on Earth.
Reimagined for the ISS.
Three light faces
Three emitting faces direct different wavelengths at different angles. Developed with our long-term LED partner Yuji, the panel combines spectral engineering with directional light.
One personal rhythm
The panel automatically follows the astronaut’s planned sleep schedule. It moves through sunrise, daylight, sunset and night, with day-to-day variation evoking changing weather on Earth.
Built for space
An aluminium body, flame-retardant materials, a locking power connector and secured components turn the lighting idea into hardware for space. The project developed from LUNARK (2020) and Rosenberg (2022) to the ISS light (2023). The ISS project describes testing potential sleep benefits, not proven clinical outcomes.
Better spaces.
Start with light.
Talk to SAGA →Draft sources & graphics
Cropped reference diagrams: Yuji Circadian Lighting, supplied PDF, pp. 4, 8, 9 and 25. All headings, captions and explanations on this page are live text. The source charts retain their original internal annotations. Replace these temporary diagrams after graphics, flow and text are approved; check the underlying scientific sources and third-party rights, including the Nature Reviews Neuroscience credit on p. 4. SAGA’s implementation and animation come from our ISS project page.