It was successfully launched at the Taiyuan Satellite Launch Center in Shanxi province, China, on 12 September 2019. It carries three payloads: a wide-field camera, a narrow-field high-resolution camera, and a ship AIS receiver [10]. (Table 1). The major payload of BNU-1 is the wide-field camera which provides multispectral satellite images with a 73.69 m spatial resolution and a 739 km swath width. Visible sensors carried by BNU-1 have the advantages of high coverage and relatively high spatial resolution, which have abilities of obtaining high-quality optical remote sensing images. However, due to the distributions of dark, noise, heat, and other environmental factors, the radiometric response of complementary metal-oxide-semiconductor (CMOS) sensors is also unbalance, often leading to the appearance of nonlinear radiometric errors in the remote sensing images. The radiometric consistency of satellite images is essential to obtain the whole image mosaics for Greenland or Antarctic ice sheets or monitor sea ice changes for Arctic or Antarctic regions [8; 11]. For example, the distributions of bule ice, which are widely distributed in Antarctic, maybe failed to be obtained if the radiometric errors are contained in the original satellite images [12]. Therefore, before applying visible remote sensing images, the radiometric errors need to be evaluated and corrected [13]. Existing radiometric correction methods can be divided into two categories. The first category is radiometric calibration, which can be divided into laboratory calibration, on-orbit calibration, and field calibration [14]. Laboratory calibration uses a stable light source for accurate radiometric calibration of the target payload. On-orbit calibration includes active \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{2}{c}{**Payloads**} & \multicolumn{2}{c}{**Main Parameters**} \\ \hline \multirow{5}{*}{The wide-field camera} & \multirow{2}{*}{Parameters} & Panchromatic, multispectral, \\  & & push broom \\ \cline{2-3}  & Spatial Resolution & 73.69 m \\  & Swath Width & 739 km \\ \cline{2-3}  & & Panchromatic: 527 nm–769 nm \\  & Spectral bandwidth & Blue (B1): 471 nm\(-\)506 nm \\  & & Green (B2): 560 nm–599 nm \\  & & Red (B3): 638 nm–676 nm \\ \hline \multirow{5}{*}{The narrow-field high-resolution camera} & Image mode & Area array staring. \\ \cline{2-3}  & Spatial Resolution & 8.2 m \\ \cline{1-1}  & Swath Width & 739 km \\ \cline{1-1} \cline{2-3}  & Spectral bandwidth & Bayer RGB \\ \hline \multirow{5}{*}{The ship AIS receiver} & Receiving frequency point & 161.975 MHz, 162.025 MHz \\  & & 156.775 MHz, 156.825 MHz \\ \cline{1-1} \cline{2-3}  & Modulation mode & GMSK/FM \\ \cline{1-1} \cline{2-3}  & Receiving sensitivity & \(\leq\)\(-\)112 dBm \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Main parameters of the payloads of BNU-1. onboard calibration and passive sun calibration. Field calibration serves as an alternative method to compensate for changes in the on-orbit sensor by selecting scenes. It requires observers to conduct on-site surveys to measure the surface radiances for a selected area with a large flat terrain, high visibility, and uniform reflectance. Then, these measurements are used to calibrate the observation from the satellite. The second category of methods is the relative sensor normalization. Common relative sensor normalization methods include histogram matching, histogram equalization, and moment matching [15; 16]. These methods assume that detectors from different satellite sensors should have the same radiation distribution characteristics for the detected objects. They remove errors by calculating the correlation between the error band and the grayscale statistics of the normal image. The wide-field camera carried by BNU-1 is a visible remote sensing sensor. It is also necessary to evaluate and correct the radiometric errors of the images obtained by BNU-1.