Multi-temporal DInSAR analysis with X-band high resolution SAR data: examples and potential

The recent availability of wide-bandwidth, high-frequency, high-resolution SAR data is contributing to improved monitoring capabilities of spaceborne remote sensing instruments. In particular, the new COSMO/SkyMed (CSK) and TerraSAR-X (TSX) X-band sensors allow better performances in multitemporal DInSAR and PSI applications than legacy C-band sensors such as ENVISAT ASAR, with respect to both target detection and terrain displacement monitoring capabilities. In this paper we investigate about the possibility of achieving performances of PSI displacement detection comparable to those of C-band sensors, by use of reduced numbers of high-resolution X-band acquisitions. To this end, we develop a simple model for phase and displacement rate measurement accuracies taking into account both target characteristics and sensors acquisition schedule. The model predicts that the generally better resolution and repeat-time characteristics of new-generation X-band sensors allow reaching accuracies comparable to C-band data with a significantly smaller number of X-band acquisitions, provided that the total time span of the acquisitions is large enough. This allows in principle to contain the costs of monitoring campaigns, by using less scenes. Indications are more variable in the case of short-time acquisition schedules, such as those involved in the generation of so-called "rush products" for emergency applications. In this case, the higher uncertainty given by shorter total time spans lowers X-band performances to levels mostly comparable to those of the legacy medium-resolution C-band sensors, so that no significant gain in image number budget are foreseen. These theoretical results are confirmed by comparison of three PSI datasets, acquired by ENVISAT ASAR, CSK and TSX sensors over Assisi (central Italy) and Venice.