SAR along-track interferometry with application to RADARSAT-2 ground moving target indication

摘要

Canada's RADARSAT-2 (R2) Synthetic Aperture Radar (SAR) satellite will be equipped with an experimental Ground Moving Target Indication (GMTI) mode, which makes use of the "Dual-Receive" capability of the R2 antenna to provide two apertures aligned in the along-track direction. The mode allows two SAR images to be taken under identical geometry of observation, but separated by a short time lag. One of the GMTI techniques, currently being explored, is based on SAR Along-Track Interferometry (SAR-ATI), which uses the magnitude-phase information of the interferogram to extract movers from stationary clutter. In this paper, an unconventional but fully automatic detection scheme, derived using a histogram approximation to the clutter joint Probability Density Function (PDF), is proposed. The new method permits the implementation of a Constant False Alarm Rate (CFAR) detector without the need to derive a theoretical joint PDF for the clutter interferogram. A false alarm reduction technique, based on "selective" local density calculations, is also discussed and implemented, showing striking improvement in the reduction of the number of false alarms (up to 75% reduction) over the original detector without significantly degrading its performance. The detector is shown to be robust in its ability to handle both simulated (R2) and real (airborne) data. Preliminary comparison with a conventional CFAR detector, derived using theoretical marginal PDFs of the interferogram's magnitude and phase, show the performance superiority of the new detector.