Given the extreme importance of monitoring ice sheets with remote sensing instruments in order to predict their interactions with the environment, the ESA IceSAR 2012 campaign was performed in south-west Greenland in the framework of BIOMASS activities. The objective was to assess the capability of longer wavelength SAR to retrieve information about ice flow and structure. In the present paper first results from processing of tomographic data for subsurface ice structure mapping are presented. The extent of signal penetration has been found to be of about 20-60 m, conditional on the different glacier zone investigated.