A method of foreign object debris discrimination incudes illuminating particulates located within a sensing volume with a first electromagnetic radiation pulse emitted from a first source, and illuminating the particulates within the sensing volume with a second electromagnetic radiation pulse emitted from a second source, wherein the second electromagnetic radiation pulse has a second wavelength range within the terahertz (THz) regime. The first electromagnetic radiation returns and the second electromagnetic radiation returns are compared to determine a scattering ratio from the comparing step. The scattering ratio is then utilized to determine a resultant foreign object debris type of the solid objects.