Appearance of Persistent Scatterers for Different Terrasar-x Acquisition Modes

Since beginning of 2008 products of TerraSAR-X have been available for the scientific community and the great performance of this satellite system has been proven by encouraging results presented during the recent workshops and conferences. Outstanding technical features of TerraSAR-X are multiple geometric and radiometric imaging as well as the short revisiting time of 11 days. These offer the opportunity to build up data stacks of the same scene very fast and with varying acquisition parameters. Since February 2008 several of such datasets could be acquired for the city of Berlin, Germany, using different incidence angles and track types (i.e. ascending or descending orbits). A thorough analysis of compliances and differences in these data stacks is of particular importance for Persistent Scatterer Interferometry (PSI). While, in the past, data takes from the long-revisiting ERS and ENVISAT satellites had to be used with similar image acquisition parameters, now first TerraSAR-X data stacks – each acquired with different parameters – can be evaluated and compared. The extremely high resolution of up to 1.1 m in azimuth and 0.6 m in slant range leads to an enormous increase in the number of PS offering new potentials and applications. As different acquisition parameters for one scene are possible, the number and positions of the PS may vary from stack to stack. In this study the change in number and local appearance of PS depending on incidence angle and track type (ascending or descending orbit) are investigated. To this end, six stacks comprising varying parameters have been set up and assessed. The investigation is based on the results of PSI-GENESIS software developed at DLR, Oberpfaffenhofen, which relies on the TerraSAR-X Multi Mode SAR Processor, and includes the analysis of the PS candidates densities and positions with respect to the different parameters mentioned. Especially the question of selecting a suitable incidence angle for PS analysis in urban areas is discussed besides the choice of track type.