Speakers
Description
Due to the growth of satellite constellations in LEO, the topic of the importance of dark skies preservation has received growing attention in recent years. Brighter spacecraft disrupt scientific observations by creating streaks or bright spots in telescope images and increasing signal-to-noise ratio. This poses significant challenges both for ground-based and space-based observations, potentially preventing important scientific discoveries through astronomy. To mitigate these effects, the ESA Space Debris Mitigation Requirements contain a section on "Dark and quiet skies", which obliges the satellite developer to quantify and minimise the visual brightness of its satellite design.
To address this need, OHB has developed DarKnight, a tool designed to compute the apparent visual magnitude m_sc of a satellite using the ratio of spacecraft irradiance to solar irradiance, including atmospheric extinction effects. DarKnight implements BRDF based modelling of diffuse and specular reflections, as recommended by ESA, and incorporates an illumination, shadowing, and occultation module to accurately represent spacecraft observability.
Numerically, DarKnight is built around a lightweight and highly flexible interface, designed to streamline brightness modelling. The tool allows users to efficiently define spacecraft geometry, assign material properties, and select observer configurations with minimal operational friction. The tool supports three simulation modes: single satellite, full constellation, and mixed‑fleet analysis. This enables rapid scaling from simple studies to large scenario assessments. Users can also choose between “preliminary analysis” and “detailed analysis” modes, depending on whether only basic material parameters are available, or a more comprehensive optical characterisation is desired. This modular structure ensures fast iteration and adaptability, making DarKnight suitable both for early design loops and for refined mitigation studies.
DarKnight has been verified and validated using publicly available brightness observations of multiple spacecraft, including OneWeb, Starlink V1.5 and V2 Mini, Qianfan, and Pelican 3001. The preliminary analysis mode shows good agreement with values reported by Littoriano (2021), while the detailed analysis mode provides even higher accuracy in many cases. Some mitigation configurations introduce discrepancies, which are discussed in the presentation.
Across all tested missions, DarKnight demonstrates reliable and consistent predictive performance, making it a valuable tool for supporting ESA’s dark‑and‑quiet‑skies requirements and for guiding brightness‑mitigation strategies in future satellite designs.