Modeling the resolution of bistatic SAR used for navigation

Synthetic Aperture Radar (SAR) is an all-weather sensor that can generate photo-like images of the Earth´s surface, day or night, through clouds, rain, dust storms, and fog when infrared and visible light sensors cannot. SAR cross range resolution is inversely proportional to the length of the radar´s flight path projected onto a vector that is perpendicular to both the range vector and the normal vector of the ground plane. Traditional monostatic SAR systems experience degradation in cross range resolution when imaging a scene directly in line with the platform´s flight path. If not for this limitation, SAR would be an excellent aid to navigation for aircraft landing in adverse weather conditions. This limitation can be overcome with a bistatic SAR configuration where the transmitter is placed on a standoff aircraft and the receiver is placed on the landing aircraft. In this configuration, the bistatic SAR cross range resolution is achieved through the transmitter´s flight path. Bistatic SAR provides a landing aid capability at the cost of greater geometric complexity. In this study, an analytical model for SAR image resolution is developed as a function the relative geometry between the transmitter aircraft and the receiver aircraft. The model is used to investigate the sensitivity of resolution to multiple SAR imaging geometries. This model is then used to optimize transmitter aircraft flight parameters to achieve the finest possible image resolution.