The full potential of terahertz imaging systems for nondestructive aerospace imaging applications has not been realized
due to the lack of data linking damage and defects to terahertz signatures coupled with the complexity of modeling the
signatures. Terahertz systems (0.1 - 2.0 THz) may be ideally suited for NDI applications because of the ability of THz
radiation to penetrate through substances commonly found on the surfaces of aircraft structures while maintaining the
optical resolution required to detect defects. We will discuss several systems that we have used to study the signatures of
a set of target samples with known defects.