An iterative alternating direction method of multipliers (ADMM) is proposed for inverse finite-element-boundaryintegral (FE-BI) problem with total variation (TV) regularization. The inverse FE-BI fits to a wide class of penetrable sensing applications, where this study specifically targets the problem of radio tomography of asteroid interior structure using orbiting spacecraft. The TV regularizer enforces sparsity on the gradient of reconstructed permittivity, which agrees well with the "piecewise constant" reality of "rocks embedded in soil" scenario and, meanwhile, addresses the inherent ill-posedness. For large-scale asteroid problems, the distributed ADMM algorithm is adapted to solve the linear TV inversion at each iteration. The 2-D inversion is validated with the Fresnel Institute measurement data. Simulated cases of asteroid internal imaging are also presented. The proposed iterative ADMM can be also applied to similar penetrable imaging applications.Index Terms-Asteroid radio tomography, inverse scattering, iterative alternating direction method of multipliers (ADMM), total variation (TV) regularization.