There has been increased interest in applying radio frequency (RF) imaging to solving problems in surveillance, situational awareness, and security screening. This has been brought about by recent advances and new programs in component development from $100\mathrm{GHz}$ to $1\mathrm{THz}$ . While no new phenomenology has been uncovered in this region, the potential to finally realize systems that can begin to approach the resolution of optical imaging while operating under adverse conditions of weather and obscuration has prompted new investments. Several of the issues, beyond mere component availability, that must be considered when developing these systems are reviewed. Additionally, previous analysis of two applications proposed to operate in the region above $100\mathrm{GHz}$ is reviewed: a landing aid system and a standoff security screening imager, both of which are greatly influenced by atmospheric effects.