  A rail-mounted synthetic aperture radar has been constructed to operate at
W-band (75 - 110 GHz) and a THz band (325 - 500 GHz) in order to ascertain its
ability to locate isolated small, visually obscured metallic scatterers
embedded in highly scattering dielectric hosts that are either semi-transparent
or opaque. A top view 2D algorithm was used to reconstruct scenes from the
acquired data, locating metallic scatterers at W-band with high range and
cross-range resolution of 4.3 and 2 mm, respectively, and with improved range
resolution of 0.86 mm at the THz band. Millimeter-sized metallic scatterers
were easily located when embedded in semi-transparent, highly scattering target
hosts of Styrofoam and waxy packing foam but were more difficult to locate when
embedded in relatively opaque, highly scattering Celotex panels. Although the
THz band provided the expected greater spatial resolution, it required the
target to be moved closer to the rail and had a more limited field of view that
prevented some targets from being identified. Techniques for improving the
signal to noise ratio are discussed. This work establishes a path for
developing techniques to render a complete 3D reconstruction of a scene.
