Bistatic Space-Based Radar Space-Time Adaptive Processing

A bistatic space-based radar (SBR) system with a medium earth orbit (MEO) transmitter and an airborne receiver is a promising concept for affordable wide-area surveillance of ground moving targets. Due to the clutter characteristics, challenges exist for performing space-time adaptive processing (STAP) to separate slowly moving targets from interference. Our Phase I effort defined a first order candidate system design, studied STAP performance and demonstrated a new approach to compensate for clutter nonstationarity in bistatic SBR scenarios. This approach overcomes some of the deficiencies of previously published techniques, including 1) the ability to align both slope and value of nonlinear Doppler-angle contours 2) adaptivity to non-clutter interference without applying a fixed range-dependent transformation 3) the ability to simultaneously compensate for different range dependencies in higher range and Doppler ambiguities 4) compensation for terrain height variations using DTED and 5) a framework that naturally accommodates knowledge-aided STAP techniques. The new approach based on an expectation-maximization algorithm for covariance estimation was found to outperform standard STAP as well as Doppler warping in several different bistatic SBR scenarios. Our Phase II effort will refine the technique to produce a STAP procedure robust to a variety of environmental conditions and real world effects.