Reducing the impact of satellite brightness for astronomy: laboratory characterization and simulations

The rapid expansion of satellite constellations in low Earth orbit (LEO) has raised significant concerns about their contribution to night-sky brightness and the resulting impact on astronomical observations. In this work, we investigate a passive, material-based mitigation strategy based on an ultra-black, aerospace-qualified coating. We characterize the optical behaviour of the coating through laboratory measurements of its bidirectional reflectance distribution function (BRDF), obtained using a calibrated goniospectrophotometer. The measured BRDF is modelled using a parametric binomial function and incorporated into a brightness simulation framework to predict the apparent magnitude of representative LEO satellite configurations. For a 3.64\, m² nadir-facing panel at an altitude of 550\, km, the coating limits peak brightness to 6.7 AB magnitude (mag) across typical observing geometries, approaching the ~ 7 AB mag visibility threshold recommended by the International Astronomical Union (IAU) in the Johnson V band. Compared to conventional specular spacecraft surfaces, such as the Starlink V1.5 chassis, the coating significantly suppresses brightness enhancements across a range of viewing geometries and reduces sensitivity to secondary illumination, including earthshine. This behaviour is consistent with the measured near-Lambertian scattering properties of the coating, which suppress directional reflectance and contribute to stable brightness across varying illumination and viewing conditions, including extreme albedo. These results demonstrate the potential of laboratory-characterized, ultra-low-reflectance coatings as a scalable, material-level component of broader strategies to reduce satellite-induced light pollution. A dedicated in-orbit demonstration is planned with Jovian-1 to validate these findings under operational conditions.