Blind Geolocation of RF-Signals with LEO Satellite Formations

This paper presents a hybrid geolocation approach specifically designed for passive geolocation of unidentified RF emitters. The proposed method leverages a sparse antenna array consisting of seven formation flying satellites, enabling geolocation without ambiguity or low resolution while avoiding the need to confine the solution space. Each satellite is equipped with a single-element antenna distributed over several kilometers, providing a highly aperture-efficient configuration and enabling precise Angle of Arrival (AOA) estimation. However, the inherent sparsity of the array introduces manifold grating lobes, leading to ambiguity in the AOA estimation process. To overcome this ambiguity, we employ Time Difference of Arrival/Frequency Difference of Arrival (TDOA/FDOA) geolocation estimation. The inter-satellite distance required for AOA estimation differs from that for TDOA/FDOA estimation. The latter imposes a maximum distance constraint among the AOA satellite formation. To establish the constraint condition, our approach involves a comprehensive analysis of the Cramer Lower Bound (CRLB) for both TDOA/FDOA in the first step and the confinement of the solution space for AOA geolocation estimation in the second step. By combining these three methods through a joint CRLB analysis, we gain valuable insights into the overall performance of the system. The integration of multiple geolocation techniques, strategic satellite configuration, and significant improvement in accuracy compared to existing methods constitute the key innovations of this research.