Abstract
With the recent launches of the German TerraSAR-X and the Canadian RADARSAT-2, both equipped with phased array antennas and multiple receiver channels, synthetic aperture radar, ground moving target indication (SAR-GMTI) data are now routinely being acquired from space. Defence R&D Canada has been conducting SAR-GMTI trials to assess the performance and limitations of the RADARSAT-2 GMTI system. Several SAR-GMTI modes developed for RADARSAT-2 are described and preliminary test results of these modes are presented. Detailed equations of motion of a moving target for multiaperture spaceborne SAR geometry are derived and a moving target parameter estimation algorithm developed for RADARSAT-2 (called the Fractrum Estimator) is presented. Limitations of the simple dual-aperture SAR-GMTI mode are analysed as a function of the signal-to-noise ratio and target speed. Recently acquired RADARSAT-2 GMTI data are used to demonstrate the capability of different system modes and to validate the signal model and the algorithm.
Highlights
Due to the significant clutter Doppler spread that is imparted by a fast-moving space-based radar (SBR) platform and the large footprints that result from space observation of the earth, detection of airborne and ground vehicles is a difficult problem
We describe here a target parameter estimation algorithm based on the fractional Fourier transform (FrFT) [44] and along-track interferometry (ATI) [45], called the Fractrum Estimator, for the RADARSAT-2 imaging geometry
The results show that the standard deviation of the estimate of the range speed, indicated by the length of the error bars, increases with increasing target range speed Vtr
Summary
Before the launches of German TerraSAR-X [9], Canadian RADARSAT-2 [10], and Italian COSMO-SkyMed [11] in 2007-2008, spaceborne SARs were only single-aperture systems Such systems have a very limited GMTI capability due to dominant radar clutter, which prevents slowly moving targets from being detected. SAR-GMTI processing algorithms developed by the German Aerospace Center (DLR) and the Institute for High Frequency Physics and Radar Techniques (FGAN-FHR) are discussed in more details, as they have adopted two very different approaches and assumptions for the detection and estimation of ground moving targets.
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