## 3 Results
### Comprehensive Gain Calculation Results  
In Section 3.1, the comprehensive gains of different COMS sensors on board the OHS-F satellite calculated using the ground measurement data from different RadCalNet sites were shown, and the consistency of the calibration results and the stability of the sensors' radiometric performance was analyzed. In this section, the calibration data from different sites on different dates were used to fit the comprehensive gains of three CMOS sensors on board the OHS-F satellite in 2020 and 2021. Taking some bands of CMOS2 as an example, the results are shown in the figure below.  
As shown in Figure 12, the adaptive weighted least squares method can be used to eliminate the influence of discrete observation points. Compared to direct linear fitting and simple least squares fitting, the fitting error was the smallest using the adaptive weighted least squares method.  
Figure 13 shows the comprehensive gain fitting results and fitting errors of the CMOS1 sensor on board the OHS-F satellite in 2020 and 2021. It is noted that the overall trend of comprehensive gain in 2020 and 2021 at the wavelength range of 500 nm to 880 nm was very similar, and the gain value was also relatively close. In terms of fitting error, the %RE and %RMSE of these bands were basically within 10%.  
Figure 11: Calibration results for OHS-F CMOS3. (**a**) Description of comprehensive gains in 2020; (**b**) description of averaged value and SD of comprehensive gains in 2020; (**c**) description of comprehensive gains in 2021; (**d**) description of averaged value and SD of comprehensive gains in 2021.  
Figure 14 shows the fitting results and fitting errors of the comprehensive gain of the CMOS sensor. The fitting comprehensive gains in 2020 and 2021 were quite different, which was mainly due to the poor radiometric stability of the CMOS2 sensor in 2020 and the large change in the early stage of the launch. In terms of the fitting error, the fitting error of the bands at 443 nm, 760 nm, and 820 nm, and the bands with a central wavelength greater than 910 nm was large, which was basically consistent with the bands with poor stability in the previous analysis.  
Figure 15 shows the fitting results and fitting errors of the comprehensive gain of the CMOS3 sensor. The fitting comprehensive gains in 2020 and 2021 basically followed the same trend with the wavelength, and the comprehensive gain of most of the bands was also close in value. In terms of the fitting error, like the CMOS2 sensor, fitting errors greater than 10% were concentrated in the bands of 443 nm, 760 nm, and 820 nm, and in bands with central wavelengths greater than 910 nm.  
Figure 12: The radiance and DN value used to fit comprehensive gains for CMOS2. (**a**) description of 2020; (**b**) description of 2021.  
In summary, the comprehensive gain in 2020 and 2021 based on the least squares fitting was basically the same. The bands with large fitting errors were mainly concentrated in the gas absorption band (such as the bands with central wavelengths near 760 nm) and the bands with low signal-to-noise ratios (such as 443 nm and the bands with central wavelengths greater than 910 nm).  
Figure 14: Comprehensive gain fitting results and fitting errors for OHS-F CMOS2. (**a**) Description of comprehensive gain fitting results; (**b**) description of comprehensive gain fitting error.  
Figure 15: Comprehensive gain fitting results and fitting errors for OHS-F CMOS3. (**a**) Description of comprehensive gain fitting results; (**b**) description of comprehensive gain fitting error.