3D Velocity Estimation for Moving Targets via Geosynchronous Bistatic SAR

Recently, geosynchronous synthetic aperture radar (GEO-SAR), which can achieve continuous Earth observation missions with large coverage and short revisit period, has drawn extensive attention. The wide-swath imaging mode of GEO-SAR presents great potentials for bistatic observation applications. Geosynchronous bistatic SAR (GEO-BiSAR) can not only complete large scene imaging task, but also provide the conditions for ground moving-target indication (GMTI). In this paper, the 3D velocity estimation for moving target via GEO-BiSAR are investigated. And the velocity estimation problem is extended to three-dimensional (3D) domain, considering that targets always move in a 3D space. To solve the 3D velocity of moving targets via GEO-BiSAR, the 3D velocity raw signal model is established, and a method based on fractional Fourier transform (FrFT) is proposed. First, the Doppler centroids and Doppler rates in the GEO-BiSAR are estimated by the FrFT. Second, one of the Doppler rates is used to estimate the azimuth velocity. Then, the range and height velocity are obtained by solving a Doppler centroid equation set. Finally, simulation experiments are presented to demonstrate the effectiveness of the method.