Campus, Varian 355
We present a method to reconstruct the probability distribution of the weak lensing magnification of Type Ia supernovae (SNe Ia) from observational data. The method is directly applicable to future data from surveys like WFIRST. With a realistic synthetic catalog, we measure the weak lensing signature and express the observable in terms of the variance of the lensing magnification. The comparison with cosmological models can be used to constrain cosmological parameters. This boosts SNe Ia as a cosmological probe by probing both geometrical expansion and growth of cosmological density perturbations.