Anthropogenic Space Object attitude and material characterisation through multi-colour light curve inversion

Light-curve inversion for anthropogenic space objects (ASOs) is ill-posed when performed in a single band, which leads to non-unique combinations of attitude and material parameters. We present a physically grounded forward model based on a Cook–Torrance bidirectional reflectance distribution function, explicit shadowing by Earth and self-occlusion, and a satellite-centred geometry. We cast attitude–material retrieval as a constrained optimization problem and use multi-colour light curves (Johnson–Cousins B , V , R ) to regularize the inversion by coupling wavelength-invariant parameters. On four space objects of distinct morphology, the multi-colour constraint improves fit quality and narrows the admissible solution set relative to panchromatic inversions. We report parameter uncertainties from multi-start annealing and provide sensitivity of the fit to key BRDF and attitude parameters. Results support multi-colour optical surveys as an efficient path to unambiguous ASO characterization from a single site.