## 1 Introduction
For instance, previous studies have shown that attenuation measurements of multi-frequency links can be used to retrieve the parameters [24; 25]. Taking advantage of the oblateness of large raindrops, the approach of using attenuation measured by multi-polarization links has also been investigated [26; 27]. Furthermore, the multi-polarization and multi-frequency approaches can be combined together to improve the performance of the DSD retrieval [28]. On the other hand, it has been suggested that not all three parameters are always needed for the representation of DSD. Some studies use fixed \(\mu\) models (e.g., [25; 29]), while others identify a \(\mu-\Lambda\) relationship (e.g., [30; 31]) so that the number of independent parameters is also reduced to two. Both approaches have their merits and other factors such as rain types and locations determine which approach performs better. To date, existing studies use ground links at fixed locations to retrieve the path-averaged DSD parameters. In this paper, we will explore the possibility of exploiting the tomographic capability of moving signal links offered by LEO satellites. Realistic system models are proposed for the satellite communication system in which both vertically and horizontally polarized links are in operation. Synthetic DSD fields are adopted to suit the purpose of the study, and we use the Pruppacher-Beard raindrop shape model [32] and the T-matrix method [33] to calculate the attenuation caused by electromagnetic scattering. Our calculation shows that the elevation angle of the link does not affect the specific attenuation very much for horizontally polarized signals. While for vertical polarization, the increase in specific attenuation for the same rain field could be more than 10% when the elevation angle changes from 40 to 90 degrees. The two attenuation fields retrieved by the two differently polarized links are examined for the purpose of DSD estimation. It is found that a linear relationship can be identified between the slope parameter and the retrieved specific attenuation ratio of vertically to horizontally polarized signals. Using this relationship, we examine a fixed \(\mu\) model and investigate the system's ability to retrieve the slope (\(\Lambda\)) and intercept (\(N_{0}\)) parameters. Simulation results show that for areas of high specific attenuations, the retrieval is more accurate, thereby both the retrieved slope and intercept parameters have a close agreement with their true values. The main contributions of this study are summarized as follows. * A theoretical model is built for the novel approach for raindrop size distribution retrieval using dual-polarized microwave signals from LEO satellites;
* The feasibility of the approach is investigated through simulations of synthetic rain events and realistic satellite communication systems;
* It is confirmed that the specific attenuation ratio of vertically to horizontally polarized signals can be used to retrieve the slope and intercept parameters of DSD. The rest of the paper is organized as follows. Section 2 describes the satellite signal model, and explains how the SNR at the receivers is related to the path-integrated attenuation. It also establishes the DSD parametric model and examines the theoretical basis of DSD retrieval. In Section 3, simulation results of the synthetic DSD fields, the retrieved attenuation fields and DSD parameters are presented and discussed. Section 4 concludes the paper.