PSI deformation map retrieval by means of temporal sublook coherence on reduced sets of SAR images

Prior to the application of any persistent scatterer interferometry (PSI) technique for the monitoring of terrain displacement phenomena, an adequate pixel selection must be carried out in order to prevent the inclusion of noisy pixels in the processing. The rationale is to detect the so-called persistent scatterers, which are characterized by preserving their phase quality along the multi-temporal set of synthetic aperture radar (SAR) images available. Two criteria are mainly available for the estimation of pixels' phase quality, i.e., the coherence stability and the amplitude dispersion or permanent scatterers (PS) approach. The coherence stability method allows an accurate estimation of the phase statistics, even when a reduced number of SAR acquisitions is available. Unfortunately, it requires the multi-looking of data during the coherence estimation, leading to a spatial resolution loss in the final results. In contrast, the PS approach works at full-resolution, but it demands a larger number of SAR images to be reliable, typically more than 20. There is hence a clear limitation when a full-resolution PSI processing is to be carried out and the number of acquisitions available is small. In this context, a novel pixel selection method based on exploiting the spectral properties of point-like scatterers, referred to as temporal sublook coherence (TSC), has been recently proposed. This paper seeks to demonstrate the advantages of employing PSI techniques by means of TSC on both orbital and ground-based SAR (GB-SAR) data when the number of images available is small (10 images in the work presented). The displacement maps retrieved through the proposed technique are compared, in terms of pixel density and phase quality, with traditional criteria. Two X-band datasets composed of 10 sliding spotlight TerraSAR-X images and 10 GB-SAR images, respectively, over the landslide of El Forn de Canillo (Andorran Pyrenees), are employed for this study. For both datasets, the TSC technique has showed an excellent performance compared with traditional techniques, achieving up to a four-fold increase in the number of persistent scatters detected, compared with the coherence stability approach, and a similar density compared with the PS approach, but free of outliers.Peer ReviewedPostprint (published version

Status Report on the TerraSAR-X Mission

TerraSAR-X is a new German radar satellite that was launched in June 15, 2007. Its lifetime will be five years. It carries a high frequency X-band SAR sensor that can be operated in three different modes and various polarizations. The Spotlight-, Stripmap- and ScanSAR-modes provide high resolution images for detailed analysis as well as wide swath data whenever a larger coverage is required. These high geometric and radiometric resolutions together with the single, dual and quad-polarization capability are innovative and unique features with respect to space borne systems. Additionally several incidence angle combinations will be possible and double side access can be realized by satellite roll maneuvers. The satellite will be positioned in a sun-synchronous 11 days repeat orbit. The revisit time in the very high resolution Spotlight mode is 2.5 days for 95% Earth’s surface visible to TerraSAR-X. TerraSAR-X is an operational SAR-system for scientific and commercial applications. The commercial exploitation is exclusively granted to Astrium / Infoterra GmbH. DLR is responsible for the scientific utilization of the TerraSAR-X products. The status “scientific use” needs to be gained via a selection process. The Science Service System (http://sss.terrasar-x.dlr.de/) was developed for this purpose. Since end of October new proposals can be submitted at any time. The corresponding TerraSAR-X data will be provided to the costs of fulfilling the user request. Further Announcements of Opportunity (AOs) are planned where special conditions might be applied with respect to the data provision. Only four days after launch the first SAR image was processed successfully. A 30 km x 60 km area in Russia, western to Wolgograd has been imaged in the stripmap mode, HH polarization. Herewith the functional capability of the satellite on one hand and the operability of the ground segment on the other hand could be demonstrated. The entire processing chain including order input, scheduling, commanding, data acquisition, on ground data reception, SAR processing and archiving of the images has been verified. This result was also the consequence of a comprehensive pre-launch testing program including numerous space-to-ground-segment tests. By now the commissioning phase, involving tasks such as calibration, characterization/verification of the SAR-instrument, SAR system performance analysis, orbit and attitude as well as product verification was terminated successfully. The aim to ensure optimum SAR image quality and to accomplish the full operational readiness was achieved in December 2007 when the project passed successfully the Operational Readiness Review. Since January 7, 2008 ordering is possible for accepted proposals. Focus of the proposed presentation will be a review of the proposed scientific research, background mission scenarios as well the access procedure for researchers and future AOs