Large or bright satellite constellations
- 1European Southern Observatory
- 2IAU Centre for the Protection of the Dark and Quiet Sky, IAU-UAI Headquarters
Abstract
Context . Large satellite constellations impact astronomy through both visible trails and the generation of diffuse and atmospherically scattered light. Quantification of this cumulative sky-background component is essential to assess the full ramifications of extant and proposed systems. Aims . This study evaluates the effect of proposed constellations – ranging from current deployments to mega-constellations and very bright reflector concepts – on direct trail losses, diffuse background, and scattered sky brightness. Methods . The methodology employs a numerical model for Mie and Rayleigh scattering in the V band, adapted from moonlight sky-brightness calculations and validated against observations of moonlight and stellar background light. This is combined with the SatConAnalytic package to quantify scattered light, diffuse light from undetected satellites, and direct losses from detected trails. Results . Constellations comprising ∼60 000 satellites that adhere to the V 550km ≥ 7 recommendation exert a negligible effect on sky brightness, contributing only about 10 −4 of the natural dark sky. Conversely, mega-constellations with 10 6 satellites render trails pervasive, thereby affecting the majority of long exposures. Bright satellites, such as spacecraft analogous to AST SpaceMobile, significantly impact saturating detectors even when their number is moderate. Extremely bright satellites pose a far more severe threat: a 5000-satellite Reflect Orbital-like constellation could elevate the scattered sky background by 20–30%, and a population of 50 000 could increase it by 200–300%. Conclusions . The constellations currently proposed for launch, which exceed 1 700 000 objects and include satellites brighter than V 550km = 7, would substantially degrade astronomical observations. Maintaining satellite brightness below V 550km = 7 is important for all instruments but critical for safeguarding saturating instruments, such as the Rubin LSST camera, and for limiting sky-background pollution. Even under this constraint, the total satellite population should remain below ∼100 000 satellites to ensure that field-of-view losses do not exceed typical technical downtime.
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BibTeX
@article{hainaut2026large,
title = {{Large or bright satellite constellations}},
author = {O. Hainaut},
journal = {Astronomy and Astrophysics},
year = {2026},
month = jun,
doi = {10.1051/0004-6361/202660006},
url = {https://doi.org/10.1051/0004-6361/202660006},
note = {CC BY},
}
RIS
TY - JOUR
TI - Large or bright satellite constellations
AU - O. Hainaut
PY - 2026
DA - 2026/06/30
JO - Astronomy and Astrophysics
DO - 10.1051/0004-6361/202660006
UR - https://doi.org/10.1051/0004-6361/202660006
AB - Context . Large satellite constellations impact astronomy through both visible trails and the generation of diffuse and atmospherically scattered light. Quantification of this cumulative sky-background component is essential to assess the full ramifications of extant and proposed systems. Aims . This study evaluates the effect of proposed constellations – ranging from current deployments to mega-constellations and very bright reflector concepts – on direct trail losses, diffuse background, and scattered sky brightness. Methods . The methodology employs a numerical model for Mie and Rayleigh scattering in the V band, adapted from moonlight sky-brightness calculations and validated against observations of moonlight and stellar background light. This is combined with the SatConAnalytic package to quantify scattered light, diffuse light from undetected satellites, and direct losses from detected trails. Results . Constellations comprising ∼60 000 satellites that adhere to the V 550km ≥ 7 recommendation exert a negligible effect on sky brightness, contributing only about 10 −4 of the natural dark sky. Conversely, mega-constellations with 10 6 satellites render trails pervasive, thereby affecting the majority of long exposures. Bright satellites, such as spacecraft analogous to AST SpaceMobile, significantly impact saturating detectors even when their number is moderate. Extremely bright satellites pose a far more severe threat: a 5000-satellite Reflect Orbital-like constellation could elevate the scattered sky background by 20–30%, and a population of 50 000 could increase it by 200–300%. Conclusions . The constellations currently proposed for launch, which exceed 1 700 000 objects and include satellites brighter than V 550km = 7, would substantially degrade astronomical observations. Maintaining satellite brightness below V 550km = 7 is important for all instruments but critical for safeguarding saturating instruments, such as the Rubin LSST camera, and for limiting sky-background pollution. Even under this constraint, the total satellite population should remain below ∼100 000 satellites to ensure that field-of-view losses do not exceed typical technical downtime.
SN - 0004-6361
SN - 1432-0746
ER -