## 2 Instrument Characteristics  
The MWHS-II onboard FY-3F inherits the instrument characteristics of the MWHS-II from FY-3E but differs from the MWHS-II of the 02 batch FY-3C and FY-3D in that the frequency of window channel 10 has been changed from 150 GHz to 166 GHz, which enhances the instrument's radiometric calibration accuracy and detection sensitivity. Compared to ATMS, MWHS has eight additional channels near 118 GHz, which are located within the oxygen absorption band and can better detect the vertical temperature distribution in the atmosphere. Furthermore, although MWHS and ATMS share the same frequency near 183 GHz, the bandwidth setting for the 183.31 \(\pm\) 1.8 GHz channel is different. as shown in Table 1.  
The MWTS-III carried by FY-3F has inherited the MWTS-III of FY-3E, and it is an upgraded version of the MWTS-II instrument. This instrument has 17 channels. Compared to MWTS-II, it can better detect temperature distribution information near the surface and in the lower troposphere. In comparison to ATMS, MWTS-III has a larger scanning range, with 98 fields of view (FOVs) along each scan line, while ATMS has 96. The detailed channel information for the three instruments is shown in Table 2.  
Polarization is one of the fundamental characteristics of each channel, and it also affects data simulation and application. Therefore, it is of great importance to determine the polarization of the FY-3F MWTS and MWHS. Pure horizontal (H) or vertical (V) polarization of cross-track scanning radiometers only occurs at the minimum scan angle, while at other scan angles, it represents a mixed contribution from both V and H polarizations [22], \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Channel**} & \multicolumn{2}{c}{**Central Frequency (GHz)**} & \multicolumn{2}{c}{**Bandwidth (MHz)**} \\ \hline
**MWHS** & **ATMS** & **MWHS** & **ATMS** & **MWHS** & **ATMS** \\ \hline
1 & 16 & 89.0 & 88.2 & 1500 & 2000 \\
2 & & \(118.75\pm 0.08\) & & 20 & \\
3 & & \(118.75\pm 0.2\) & & 100 & \\
4 & & \(118.75\pm 0.3\) & & 165 & \\
5 & & \(118.75\pm 0.8\) & & 200 & \\
6 & & \(118.75\pm 1.1\) & & 200 & \\
7 & & \(118.75\pm 2.5\) & & 200 & \\
8 & & \(118.75\pm 3.0\) & & 1000 & \\
9 & & \(118.75\pm 5.0\) & & 2000 & \\
10 & 17 & 166.0 & 165.5 & 1500 & 3000 \\
11 & 22 & \(183.31\pm 1\) & \(183.31\pm 1\) & 500 & 500 \\
12 & 21 & \(183.31\pm 1.8\) & \(183.31\pm 1.8\) & 700 & 1000 \\
13 & 20 & \(183.31\pm 3\) & \(183.31\pm 3\) & 1000 & 1000 \\
14 & 19 & \(183.31\pm 4.5\) & \(183.31\pm 4.5\) & 2000 & 2000 \\
15 & 18 & \(183.31\pm 7\) & \(183.31\pm 7\) & 2000 & 2000 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Channels comparison of MWHS-II and ATMS. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Channel**} & \multicolumn{2}{c}{**Central Frequency (GHz)**} & \multicolumn{2}{c}{**Bandwidth (MHz)**} \\ \hline
**MWTS** & **ATMS** & **MWTS** & **ATMS** & **MWTS** & **ATMS** \\ \hline
1 & 1 & 23.8 & 23.8 & 270 & 270 \\
2 & 2 & 31.4 & 31.4 & 180 & 180 \\
3 & 3 & 50.30 & 50.30 & 180 & 180 \\
4 & 4 & 51.76 & 51.76 & 400 & 400 \\
5 & 5 & 52.8 &  
including quasi-horizontal (Qh) and quasi-vertical (Qv). According to the Hagen-Rubens equation [23], the radiation of Qh and Qv channels can be derived as follows:  
\[\mathrm{R_{qv}^{c}}=\mathrm{R_{qv}}+\epsilon_{h}(\mathrm{R_{r}}-\mathrm{R_{h}})+ [\epsilon_{v}(\mathrm{R_{r}}-\mathrm{R_{v}})-\epsilon_{h}(\mathrm{R_{r}}- \mathrm{R_{h}})]\mathrm{sin^{2}}\theta-\frac{\mathrm{R_{3}}}{2}(1-\epsilon_{h} )^{\frac{3}{2}}\mathrm{sin\,2}\theta \tag{1}\]  
\[\mathrm{R_{qh}^{c}}=\mathrm{R_{qh}}+\epsilon_{h}(\mathrm{R_{r}}-\mathrm{R_{h}}) +[\epsilon_{v}(\mathrm{R_{r}}-\mathrm{R_{v}})-\epsilon_{h}(\mathrm{R_{r}}- \mathrm{R_{h}})]\mathrm{cos^{2}}\theta-\frac{\mathrm{R_{3}}}{2}(1-\epsilon_{h} )^{\frac{3}{2}}\mathrm{sin\,2}\theta \tag{2}\]  
where \(\mathrm{R_{qv}^{c}}\) and \(\mathrm{R_{qh}^{c}}\) represent the radiation from the reflector.