Ground-Based Radar Performance Improvements

Ground-based radars operating in the naturally or nuclear disturbed ionospheric environment can be subjected to high levels of clutter and returns from countermeasures. Effective clutter mitigation and false alarm control is required to maintain performance in high sensitivity applications such as ballistic missile or Re-entry Vehicle (RV) detection, tracking, and discrimination. We propose a performance-enhancing algorithm that mitigates clutter and false alarms while actually increasing radar sensitivity. This method is called SIFTER, for Signal Inversion For Target Extraction and Registration. Our team has already successfully applied SIFTER to radars operating in the HF band (ROTHR over-the-horizon radar and CODAR HF surface wave radar). In this proposed effort we will extend the benefit of SIFTER processing to Air Force ground-based radars. SIFTER operates by solving the inverse problem of finding the distribution of scatterers (target and clutter sources) that best reproduces the radar measurements. The inverse problem is solved using Tikhonov Regularization, a smoothing constraint that works to suppress clutter sources in the scattering volume while maintaining target returns. As the SIFTER solutions are evolved in time, spurious noise peaks that do not evolve in a way consistent with their Doppler velocity are quickly smoothed away, exposing even quite weak targets.