# Analysis of the Dihedral Corner Reflector's RCS Features in Multi-Resource SAR
## 4 The RCS Features of the CR Array in Multi-Resource SAR
### The RCS Reduction Difference of CRs with Different Tilt Angles
Figure 9: The RCS time series of the dihedral reflector with a tilt angle of 10\({}^{\circ}\)under Sentinel (**a**) and TSX (**b**) data. evident that the scattering energy of DRI is unstable. Following an on-site investigation, it was discovered that the issue stemmed from misalignment towards the ascending orbit during azimuth alignment. This resulted in a deviation of a few degrees for the panels in descending orbit with respect to the radar beam. Figure 9 depicts the RCS time series of a dihedral CR with a 10\({}^{\circ}\) horizontal tilt angle in multi-resource SAR data. The incident angles for both SAR datasets fall within the range of 29\(\sim\)44\({}^{\circ}\), resulting in relatively small deviation angles and differences for the CR with a 10\({}^{\circ}\) tilt angle under both SAR datasets. In the Sentinel data, the modeled and measured RCS reduction differences resulting from the deviation angle difference (\(\Delta\beta\)) for DR5 and DR6 are relatively small, within 0.5 dBm. DR4 shows an RCS reduction difference (\(\Delta\tilde{\sigma}\)) of 2 dBsm, and its RCS in the TSX data is approximately 3 dBsm lower than that of an equivalent-sized CR. The observed RCS reduction difference (\(\Delta\tilde{\sigma}\)) in the ascending and descending TSX data differs by about 2.1 dBsm from the model values, indicating a slight obstruction caused by surrounding trees. Additionally, in the descending TSX data, the reflection from DR6 has attenuated by nearly 20 dBsm compared to the ascending TSX data, attributed to the same reasons as observed in DR1. In conclusion, except for CRs with noticeably attenuated reflection, the measured and modeled RCS reduction differences for other CRs in the Sentinel and TSX data are quite consistent, with deviations within 0.5 dBsm. This analysis also indicates that the examination of RCS reduction and RCS reduction difference can serve as a reference for CR quality inspection. Figure 10 illustrates the RCS time series of a dihedral CR with 15\({}^{\circ}\) tilt angle, resulting in incident deviation angles of 12\({}^{\circ}\) and 7\({}^{\circ}\) in the Sentinel and TSX data, respectively. In the Sentinel data, the measured RCS reduction difference of DR8 deviates by 0.2 dBsm from the theoretical value. In the TSX data, the RCS experiences a nearly 9 dBsm decrease in the descending orbit compared to the ascending orbit, with the same underlying cause as DR1. In the ascending orbit, DR7's RCS has been gradually declining since March 2021. This phenomenon is evident in both the Sentinel and TSX data and is attributed to gradual obstruction due to the growth of thatch on the ascending orbit side. In this section, a comparative analysis of the measured and modeled RCS reduction differences for CRs under different orbits has revealed that certain CRs may encounter issues such as panel quality, alignment deviations during installation and obstructions in the surrounding environment. This suggests that analyzing RCS reduction differences can serve as a basis for assessing the reliability of CR production or installation.