Range-Doppler and clutter considerations in designing a bistatic space based GMTI radar system

The theoretical application of bistatic radar concept to the ground moving target indicator mode from space based platforms present some intriguing possibilities, along with several intrinsic difficulties that must be surmounted in order to design an effective system. Key among these difficulties is the extraction of slowly moving ground target velocities from the significant background clutter spread introduced by relative Earth-satellite motion. The difficulty in characterizing the clutter is significantly compounded by the extreme variability in the bistatic footprint as a function of Earth/satellite geometry. In order to explore the theoretical nature of the motion induced clutter spread, a simple MATLAB model was constructed to simulate the clutter characteristics of a hypothetical medium Earth orbit (MEO) transmitter, and a low Earth orbit (LEO) receiver. Various receiver and transmitter satellite geometries have been discussed in the literature; placing the transmitter at MEO allows for a larger transmitter footprint, and moves it to a higher and presumably ´safer´ orbit, but then generally requires a somewhat larger antenna aperture. The more numerous LEO receiver platforms needed do not then require the additional expense of radiation hardening and are also less expensive to place in orbit.