Speaker
Description
Artificial light pollution in the night sky has increased significantly in recent years, raising growing concern among institutions and the space community. International bodies, including the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) and the International Astronomical Union (IAU), have recognized satellite brightness as a major sustainability challenge. Despite this growing awareness, no formalised framework currently exists to assess and regulate satellite brightness at the pre-launch stage. This work funded by a Global Satellite Operators Association (GSOA) study aims to address that gap.
A method for estimating satellite brightness is proposed, based on the modelling of apparent magnitude through the combined contribution of direct solar flux and Earthshine, i.e., sunlight reflected by the Earth toward the satellite. Earthshine is modelled using a discrete Earth reflectance model, in which the Earth’s surface is subdivided into panels and assigned reflectance properties derived from observational data. In particular, BRDF measurements associated with the different IGBP surface classes are fitted using a Phong reflectance model to obtain a realistic representation of terrestrial reflectivity.
The satellite is represented as a three-dimensional object provided as input by the operator. The geometry is discretised into a triangular mesh, so that the spacecraft is modelled as an agglomeration of multiple two-dimensional surface elements, each contributing to the total reflected flux. This approach makes it possible to capture complex satellite geometries, including appendages and surface orientation effects. In addition, self-shadowing and facet visibility from the observer are explicitly taken into account, enabling the analysis of the impact of spacecraft attitude and orbit on apparent brightness. Material properties can also be assigned to each surface, allowing both diffuse and specular reflectance components to be modelled.
The proposed model has been validated through comparison with publicly available real observations, showing good agreement between estimated and measured brightness. Future developments will integrate the model into an indexing framework for quantifying the optical light pollution generated by a mission, with the goal of providing satellite operators with a practical tool to predict the impact of their design choices on the night sky.
| Which section would you like to submit your abstract to? | Session 12: “Towards the integration of all the open aspects in space sustainability” |
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