Abstract
We investigate multichannel imaging radar systems employing coherent combinations of polarimetry and interferometry (Pol-InSAR). Such systems are well suited for the extraction of bio- and geophysical parameters by evaluating the combined scattering from surfaces and volumes. This combination leads to several important differences between the design of Pol-InSAR sensors and conventional single polarisation SAR interferometers. We first highlight these differences and then investigate the Pol-InSAR performance of two proposed spaceborne SAR systems (ALOS/PalSAR and TerraSAR-L) operating in repeat-pass mode. For this, we introduce the novel concept of a phase tube which enables (1) a quantitative assessment of the Pol-InSAR performance, (2) a comparison between different sensor configurations, and (3) an optimization of the instrument settings for different Pol-InSAR applications. The phase tube may hence serve as an interface between system engineers and application-oriented scientists. The performance analysis reveals major limitations for even moderate levels of temporal decorrelation. Such deteriorations may be avoided in single-pass sensor configurations and we demonstrate the potential benefits from the use of future bi- and multistatic SAR interferometers.
Highlights
One of the key challenges facing synthetic aperture radar (SAR) remote sensing is to force evolution from highresolution qualitative imaging to accurate high-resolution quantitative measurement
In contrast to the phase behaviour, the interferometric coherence variation, shown in Figure 1b, is not monotonic with m: starting from almost no ground contribution (m = −20 dB) with a coherence corresponding to the volume layer alone, the coherence decreases with increasing ground contribution: due to the scattering contribution at the bottom of the volume, the overall scattering center moves towards ground
This is justified by comparing the phase error estimates computed from the signal-to-quantization noise ratio (SQNR) to the phase errors obtained from a simulation of the complete quantizer
Summary
One of the key challenges facing synthetic aperture radar (SAR) remote sensing is to force evolution from highresolution qualitative imaging to accurate high-resolution quantitative measurement. In polarimetric SAR interferometry (Pol-InSAR), both techniques are coherently combined to provide sensitivity to the vertical distribution of different scattering mechanisms [10, 11, 12]. Pol-InSAR applications deal with parameter estimation of natural volume scatterers based on the polarimetric diversity of InSAR observations (i.e., coherence and phase). Such systems use multiple satellites flying in close formation and allow for the acquisition of interferometric and polarimetric data during one satellite pass, thereby minimizing the distortions from temporal decorrelation [22, 23, 24].
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