Exploiting artificial reflectors for SAR interferometry applications

This work is devoted to assessing reliability, precision and limitations of using artificial reflectors (AR) for supporting the displacement measurements derived through Spaceborne Multi-temporal SAR interferometry (MTInSAR). An experimental site has been set up by deploying two trihedral corner reflectors (CR) whose side length is respectively 0.7 m (CR-1) and 1 m (CR-2), and one compact active transponder (CAT) used to support the calibration for both ERS and ENVISAT missions. All AR have been tuned to work with the Seintinel-1 mission. In details, CR-1 is oriented to be visible from ascending passes, while CR-2 and the CAT are oriented to be visible from descending passes, and can be moved to simulate millimetric displacements. Both ascending and descending Sentinel-1 stacks have been processed through the SPINUA processing chain, then time series of both SAR amplitude and displacement values have been analysed for assessing the accuracy of MTInSAR measurements, and evaluating the potential improvements provided by using AR. Moreover, tThe proposed experimental set up allows comparting i) results obtained by using CR and CAT; and ii) results obtained by using CR of different sizes, which means different SNR conditions for both amplitude and phase signals. Furthermore, the reflectors have been deployed over a building roof in order to evaluate the impact of signals coming from other structures surrounding the AR. This is a relevant issue when using AR for monitoring the stability of specific parts of a building. This instrumented test site will be proposed as an open experimental site by providing open -data for testing and validating interferometric techniques.

This work was supported by the Italian Ministry of Education, University and Research, D.D. 2261 del 6.9.2018, PON R&I, 2014-2020 under project “Close to Earth” (ID ARS01_00141). Authors thank Saverio Triggiani for supporting the field activities.