Surface Target Velocity Estimation Using Sar: Single Dual-Channel Sar Vs Squinted Constellation of Small Sar

The full velocity vector of a surface moving target can be estimated from Synthetic Aperture Radar (SAR) observables by either using: (i) a single platform able to measure Doppler rate and along-track interferometric (ATI) phase or (ii) a constellation of two platforms simultaneously measuring only Doppler rates or ATI phases or both. This work derives the estimation accuracies of the available possibilities and compares them. Results obtained for a spaceborne case study show that the single-platform configuration is sufficient to achieve a good estimation accuracy provided that it has the two receiving channels connected with antenna element with a sufficient ATI baseline and operates at low squint angles (below 10°). Unless this baseline is very large, a comparable accuracy can be obtained by a symmetric constellation of two single-channel satellites only measuring the Doppler rate, operating with higher squint angles (above 10°). This provides the basis for a trade-off between a single large-satellite SAR and a small coherent constellation of small-satellite SAR. In addition, the presented analysis shows that the best estimation performance can be obtained by exploiting a more complex constellation of (large) dual-channel SAR; however, most of the improvement with respect to the simpler cases is obtained using a constellation of a large dual-channel SAR and a small single-channel SAR.