PSTD-based approach to a large-scale inverse scattering problem

The three-dimensional finite-difference time-domain method (FDTD) simulation of electromagnetic wave propagation in large structures, like the cometary nucleus of 67P/Churyumov-Gerasimenko, as well as the inverse problem of reconstructing the permittivity distribution inside the comet nucleus is computationally expensive. With approximative methods not all propagation phenomena can be sufficiently modeled. For the efficient solution of this kind of inverse problem we propose the use of pseudo-spectral time-domain method (PSTD). This method overcomes the computational burdens and memory demands of the FDTD and allows accurate modeling of wave propagation for the CoNSERT case. In combination with optimal checkpointing and a state-of-the-art optimization tool, we demonstrate the solution of inverse problems at a scale of 50 wavelengths.