This proposal introduces an innovative sensor concept for the mitigation of aircraft hazards due to reduced visibility in fog, drizzle and light rain and the detection of hazards/obstacles on runways. Specifically, this effort will build upon a developing synthetic vision system for landing piloted aircraft to: 1) customize the design and feasibility for targeted unpiloted autonomous systems (UAS), and 2) incorporate interferometry for terrain mapping and hazard detection. Dubbed "PathIn", the proposed sensor is comprised of a Ka-band digitally beamformed (DBF) radar interferometer that will serve as a complement to existing infrared (IR) and near-IR enhanced visualization systems and provide a real-time data interface for ground-collision avoidance systems. The proposed effort is aligned with the effort to integrate UAS into the National Airspace (NAS). The Phase 1 effort will assess the PathIn performance for sample UAS flight scenarios over variable terrain using a high-fidelity point target simulator to provide synthetic digital surface maps and obstacle detections. This will demonstrate the potential of the PathIn as a technology that can contribute toward safe UAS operation in the NAS and in the terminal area. In Phase II we will realize a prototype of the PathIn sensor, leveraging our extensive radar, interferometry and DBF experience and key technology capabilities. In particular a FPGA-based digital receiver system will be extended for real-time beamforming and interferometry. At the end of the Phase I, a technology readiness level of 3 will be achieved.