ReflectOrbital Mirrors Would Create Dusk-Level Sky Brightness Over 30 km Radius

The paper models Rayleigh and aerosol scattering of the downward beam plus upward reflection from a 2.5 km illuminated patch under cloud-free conditions. For an observer inside the beam the mirror itself outshines the Moon by four magnitudes while the diffuse background matches post-sunset twilight, extinguishing all but the brightest stars. At 14 km the glow exceeds full-moon sky luminance across most of the visible hemisphere; at 34 km the excess remains detectable toward the beam axis. Scaling to 400 co-illuminating mirrors extends the detectable halo to 80 km.

Artificial light at night already disrupts circadian rhythms, pollinator navigation, and migratory bird orientation; the proposed constellation multiplies these stressors with a collimated, moving source whose spectrum and timing are under commercial rather than ecological control. No prior space-based illumination project has undergone equivalent atmospheric scattering analysis before hardware commitment.

Current U.S. and ITU orbital-lighting regulations address only direct glare to ground observers and aviation, not diffuse sky glow or cumulative ecological loading. The authors note that even the single-satellite EARENDIL-1 pathfinder would violate IAU dark-sky guidelines inside a 30 km radius, yet no environmental-impact statement has been released by the company.

Next steps hinge on whether national regulators require full radiative-transfer modeling and multi-year ecological monitoring before constellation licensing; without such requirements the 50 000-satellite fleet remains on the current 2028–2032 deployment timeline.