Performance analysis of multistatic configurations for spaceborne GMTI based on the auxiliary beam approach

In addition to powerful earth imaging and remote sensing, a multistatic spaceborne synthetic aperture radar (SAR) configuration offers the possibility of detecting efficiently the presence of slowly moving targets and surfaces as a result of the large baselines. Such a configuration can be achieved by a constellation of coherent passive satellites receiving the echoes of pulses transmitted by a separate SAR satellite and reflected from the earth. It also enables resolution of the design difficulty of space-based ground moving target indication (GMTI) systems caused by the severe spatial conditions. Owing to the additional degrees of freedom available in a multisatellite constellation compared with a monostatic system, the problem of blindness against certain directions of target motion can be overcome and the sensitivity can be extended to almost any direction of motion, depending on the configuration. For this purpose, non-classical algorithms have to be developed. Because of the high system complexity and the huge amount of data to be processed, only suboptimum methods can be implemented. A suboptimum method is proposed for multistatic spaceborne moving target detection based on the auxiliary beam approach. The main feature of this processing is estimation of both velocity and direction of target motion. According to this method, an analysis of multistatic SAR satellite configurations for their GMTI capability is carried out and the choice of the constellation baselines inferring directly on the expected GMTI sensitivity is discussed.