Orbiter-to-orbiter tomography: a potential approach for small planetary   objects
  The goal of this paper is to advance mathematical and computational methodology for orbiter-to-orbiter radio tomography of small planetary objects. In this study, an advanced full waveform forward model is coupled with a total variation based inversion technique. We use a satellite formation model in which a single unit receives a signal that is transmitted by one or more transponder satellites. Numerical results for a 2D domain are presented. 
Sampsa Pursiainen and Mikko Kaasalainen
astro-ph.IM