Along-Track Deformation Retrieval Performance With the ROSE-L Multichannel SAR System Using Two-Look ScanSAR

A new generation of spaceborne synthetic aperture radar (SAR) systems with digital beamforming capabilities is currently under development. In particular, multiple azimuth channels provide access to a large Doppler bandwidth, which can be used to improve the azimuth resolution. In the ScanSAR mode, however, the resolution is given by the burst time. But the exploitation of a large Doppler bandwidth leads to a wider azimuth coverage and, therefore, to a larger overlap between consecutive bursts. This overlap can be exploited interferometrically in order to retrieve an improved measurement of the azimuth differential shift between two acquisitions. The retrieval performance is hereby limited by the antenna pattern, which can severely deteriorate the image quality towards the edges of the extended bursts. The reduced quality leads to a decreased deformation retrieval accuracy in these parts of the acquisition. We analyze the performance of the along-track deformation retrieval using a two-look ScanSAR processing for the particular case of the upcoming ROSE-L mission. For this purpose we analyze the influences of thermal noise and azimuth ambiguities on the performance and show their impact on the retrieval. The derived performance is validated with simulations using distributed targets and realistic scenes. The results show that the retrieval is subject to a tradeoff between spatial resolution and retrieval accuracy. However, even for low multilooking factors, the azimuth displacement is retrieved with a better accuracy than single-look approaches. The retrieval accuracy is also shown to be sufficient in most cases in order to decouple the along-track and across-track components of the deformation at medium resolutions. In this way, the phase jumps between bursts usually observed in interferograms of non-stationary scenes are significantly mitigated.