Reconstruction of Lorentzian manifolds from boundary light observation sets

On a time-oriented Lorentzian manifold $(M,g)$ with non-empty boundary satisfying a convexity assumption, we show that the topological, differentiable, and conformal structure of suitable subsets $Ssubset M$ of sources is uniquely determined by measurements of the intersection of future light cones from points in $S$ with a fixed open subset of the boundary of $M$; here, light rays are reflected at $partial M$ according to Snells law. Our proof is constructive, and allows for interior conjugate points as well as multiply reflected and self-intersecting light cones.