## 5 Conclusions  
This work investigated the FCP and DCP modes of CP-SAR (end-to-end circular polarization system) through rice growth monitoring. For this purpose, self-cultivated rice plants from germination to ripening stages were analyzed by means of frequency domain data measurement using a ground-based CP-radar system. We applied the \(H/\bar{\alpha}\) and four-/three-component polarimetric decomposition techniques to measurement data.  
The results for the two types of polarimetric decomposition can be summarized as:  
* The \(H/\bar{\alpha}\) 2D plane showed a satisfactory clear pattern of each stage of rice growth and yielded rough discriminating capability. However, booting and ripening stages could not be separated.
* The DCP mode exhibited better classification capability than DLP mode on the \(H/\bar{\alpha}\) 2D plane.
* The four-/three-component decomposition results demonstrated a similar trend of surface and double-bounce scattering as backscattering coefficients of cross- and co-polarization respectively.
* The triangle plot of relative scattering components contribution showed adequate classification capability, similar to the \(H/\bar{\alpha}\) plane.  
The comparison results between FCP and DCP modes can be stated as:  
* Entropy showed a difference of \(\sim\)0.12 between each other, but overall evolution exhibited similarity. \(\bar{\alpha}\) values almost coincided with each other except for non-rice and DoY 159 observations, but dominant and second dominant \(\bar{\alpha}\) resulted in differences.
* The volume scattering component yielded a very similar trend and value. Surface and double-bounce scattering presented different power to each other.  
Overall, results for both the FCP and DCP modes of CP-SAR demonstrated adequate rice phenology classification capability. Differences in some polarimetric decomposition parameters between the FCP and DCP modes were noted. Moreover, the DCP mode yielded similar performance to the FCP mode about the \(H/\bar{\alpha}\) decomposition and volume scattering, and better classification performance of rice phenology compared to the DLP mode.  
This work showed the first results of the ground-based CP radar system for long-term rice observation. We anticipate that this study will contribute to the future development and implementation of CP-SAR systems for space-borne and airborne missions, to be used for precise  
Figure 12: Relative contribution of surface, double-bounce, and volume scattering components on the triangle plot. (**a**) FCP mode; (**b**) DCP mode.  
and efficient monitoring of vegetation and ground surface by combining the advantages of circular polarization and the compact mode.  
This work was supported in part by the European Space Agency Earth Observation Category 1 under Grant 6613, by the 4 th Japan Aerospace Exploration Agency (JAXA) ALOS Research Announcement under Grant 1024, by the 6 th JAXA ALOS Research Announcement under Grant 3170, by the Japanese Government National Budget (Special Budget for Project) FY 2015 under Grant 2101, Taiwan National Space Organization under Grant NSPO-S-105096; Indonesian Bhimasena, and by the Chiba University Strategic Priority Research Promotion Program FY 2016.  
[PERSON] led this work. He proposed the idea, processed data, compiled results and wrote this manuscript. [PERSON] and [PERSON] supervised with some fruitful ideas to make this work meaningful. [PERSON] and [PERSON] arranged the SAR-system and experiment together with [PERSON].  
The authors declare no conflict of interest.