In this Phase I STTR project, we propose to develop the critical innovations necessary for a high speed three dimesnional terahertz (THz) tomographic imaging system for aerospace non destructive evaluation (NDE) applcations. NASA and the Aerospace industry are beginning to utilize THz reflection imaging (for example, examining the space shuttle external tank sprayed on foam insulation for voids and disbonds). THz NDE imaging is widely applicable to composite resin, ceramic, plastic, natural, and other non-metallic materials. Current commercial equipment is capable of two dimensional raster scanning. The wider utility of THz NDE technology can be more fully exploited for the development of NASA and aerospace applications if the full potential for high speed three dimensional THz imaging is realized. The current state of the art equipment collects the THz waveform reflection from a very narrow depth range from a strongly reflective backing. The proposed innovations will increase the dynamic range of the THz waveform acquisition to allow collection of reflections from weaker interfaces, and will increase the window of high speed scanning of the THz waveform to allow three dimensional images to be reconstructed for objects many inches thick.