Abstract
Transmission line matrix (TLM) is a discrete numerical time-domain modeling technique that can frequently be reduced to a closed-form solution of the diffusion equation. In many cases the inverse operation of the TLM method is hampered by the imbalance between the number of available equations and the number of unknowns. This article outlines the nature of the problem for Gaussian temperature profiles and shows how simple optimization can be used to obtain initial or early-time thermal information.