## 7 Conclusions  
Radiometric calibration is the cornerstone towards performing quantitative applications for SAR satellite data. In this study, based on the flexible automatic trihedral CR deployed at the Xilinhot SAR satellite calibration and validation site, the radiometric calibration of the UFS and FSI mode data of C-SAR/01 employing the sliding window-based integral and peak methods was performed as quickly. The calibration results obtained by the two methods were compared and analyzed. The results show that the spatial resolution, PSLR and ISLR of the UFS, and FSI mode data of C-SAR/01 are better than those of the design indexes, and the calibration results of the integral method are more stable than those of the peak method. Statistically, the standard deviation of the calibration constants of the UFS mode was evaluated as 0.234 dB, the relative calibration accuracy as 0.233 dB, and the absolute calibration accuracy as being 0.532 dB. Furthermore, the standard deviation of the calibration constants of the FSI mode was calculated as 0.198 dB, the relative calibration accuracy as 0.199 dB, and the absolute calibration accuracy as being 0.333 dB. The results satisfy the design indexes of C-SAR/01 and meet the requirements of quantitative applications for C-SAR/01 image radiometric performance.  
Subsequently, our team will conduct a two months ground synchronous measurement experiment in the Xilinhot SAR satellite calibration and validation site, with 15 automatic trihedral CRs and ARCs in an RCS range of 35-55 dB to perform radiometric calibration of C-SAR/01 in different imaging modes in order to obtain more SAR data and more accurately and comprehensively understand the performance of the C-SAR/01 satellite. Now, the Xilinhot SAR satellite calibration and validation site used for this experiment is still under construction. The site will be built into a larger range of calibration sites to meet the needs of a wider range of imaging modes, with a fixed deployment of remotely controllable automatic CR and ARC to form a long-term, cyclical operational service capability. At the same time, the experimental method of realizing the complete SAR radiometric calibration process based on remotely controllable calibrators is investigated from the calculation of the calibrator orientation to the ground-synchronous measurement experiment and then to the SAR image radiometric calibration, so as to achieve the purpose of long-term monitoring of satellite radiometric calibration performance to ensure the quality and stability of SAR data.  
[PERSON] undertook the research data curation, designed the methodology, conducted the formal analysis, and wrote the manuscript; [PERSON] provided the resources, supervised the study, and revised the manuscript; [PERSON] assisted to design the methodology and supervised the study; [PERSON] undertook the experiment investigation of ground control data and research data curation; [PERSON] assisted [PERSON] in validating the results and editing the manuscript; [PERSON] provided the resources and gave comments and suggestions in terms of validating the results; [PERSON] assisted in the experiment investigation. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Common Application Support Platform for Land Observation Satellites of China's Civil Space Infrastructure (CASPLOS_CCSI) and the China high-resolution earth observation system (21-Y20B01-9003-19/22).  
Not applicable.  
The authors declare no conflict of interest.