## 5 Conclusions  
In this paper, the ACM based on the DVB-S2 standard is developed and utilized to improve the data transmission efficiency of LEO EO satellites. Additionally, the ACM could adaptively adjust the MCS and make better use of link resources under different weather conditions and elevation angles. The TEF is proposed to realize the scheme design and applications of Ka-band data transmission systems for LEO satellites. The simulation results show that Kashgar G/S, with little rain and representative of temperate continental climate conditions, is more suitable for CCM of MCS 28. Beijing G/S, with moderate rainfall and representative of temperate monsoon climate conditions, and Sanya G/S, with abundant rainfall and representative of tropical monsoon climate conditions, are more suitable for ACM of minimum MCS 1.  
The proposed design and analysis method in this paper could comprehensively evaluate the satellite-to-ground transmission efficiency. It is calculated according to the change of free space loss and atmospheric attenuation with the elevation angle distribution of transmission arc segment in a repeat period, which is in accordance with engineering practice. This model and method could find important applications in the system design and implementation of Ka-band ACM satellite-to-ground data transmission links.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Minimum**} & \multicolumn{3}{c}{**VCM**} & \multicolumn{3}{c}{**ACM**} \\ \cline{2-7}  & **Kashgar** & **Beijing** & **Sanya** & **Kashgar** & **Beijing** & **Sanya** \\ \hline
1 & 18.79 & 19.47 & 23.66 & 100.16 & 103.62 & 124.51 \\
3 & 25.01 & 25.85 & 31.20 & 100.16 & 103.43 & 123.59 \\
6 & 37.12 & 38.30 & 45.49 & 100.15 & 103.21 & 121.67 \\
12 & 49.78 & 51.20 & 59.57 & 100.14 & 102.91 & 119.27 \\
14 & 59.81 & 61.33 & 70.21 & 100.13 & 102.63 & 117.05 \\
20 & 80.36 & 81.85 & 90.26 & 100.11 & 101.94 & 112.25 \\
25 & 94.88 & 95.73 & 100.74 & 100.06 & 100.96 & 106.22 \\ \hline \hline \end{tabular}
\end{table}
Table 9: The TEF ratio of ACM or VCM relative to CCM of MCS 28 (%).  
**Author Contributions:** Conceptualization, Z.W. and F.L.; methodology, Z.W. and F.L.; software, Z.W.; validation, Z.W. and D.W.; formal analysis, Z.W. and F.L.; investigation, Z.W. and F.L.; resources, Z.W.; data curation, J.L. ([PERSON]); writing--original draft preparation, Z.W.; writing--review and editing, Z.W., F.L. and J.L. ([PERSON]); visualization, X.Z.; supervision, J.L. ([PERSON]); project administration, J.L. ([PERSON]) All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Beijing Nova Program with grant number Z211100002121138 and by the National key R&D plan of the Ministry of Science and Technology with grant number 2021 YFB2900405.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.  
**Data Availability Statement:** The data that support the findings of this study are available from the corresponding author upon reasonable request.  
**Conflicts of Interest:** The authors declare no conflict of interest.