Exploiting artificial reflectors for SAR interferometry applications

This work is devoted to experiment the use of artificial reflectors, both passive and active, for supporting the displacement measurements derived through multi-temporal SAR interferometry (MTInSAR). An experimental site has been set up by deploying two corner reflectors (CRs) and three active reflectors. Each CR consists of three triangular metal panels whose internal leg is respectively 69.5 cm (CR0) and 1.05 m (CR1), welded perpendicularly to each other to form a trihedral shape. Concerning the active reflectors, one is a C-band Electronic Corner Reflector (ECR-C), which is compatible with operation frequency of Sentinel-1, while the other two are Active Radar calibrators (ARC) designed in the early '90s for supporting the calibration of SAR sensors operating at C-band (ARC-C) and X-band (ARC-X). ECR-C and ARC-C have been tuned to work with the Sentinel-1 C-band SAR mission, while ARC-X has been exploited for working with COSMO- SkyMED X-band constellation. Ascending and descending data acquired by COSMO-SkyMED and Sentinel-1 have been processed through the SPINUA MTInSAR algorithm, then time series of both SAR amplitude and displacement values have been analysed for comparing results from CRs of different sizes and active reflectors. Generally, we found a good agreement between the measured and the nominal expected backscattered signals (both in amplitude and phase). The CR size impacts on the signal quality: CR0 is smaller and so noisier and more exposed to interaction with both ERC-C and urban structures than CR1. Phase stability of active reflectors is sometimes below the expected value. This instrumented test site will be proposed as an open experimental site by providing open data for testing and validating interferometric techniques.