On-Orbit Relative radiometric Calibration of the Bayer Pattern Push-Broom Sensor for Zhuhai-1 Video Satellites  
[PERSON]  
1 College of Urban and Environmental Sciences, Hubei Normal University, Huangshi 435002, China 11 College of Computer Science and Technology (CCST), Zhejiang University, Hangzhou 310058, China 11 College of Urban and Environmental Sciences, Hubei Normal University, Huangshi 435002, China 11 College of Computer Science and Technology (CCST), Zhejiang University, Hangzhou 310058, China 11 College of Computer Science and Technology (CC  
and for CMOS2,4 is a \"GRBG\" Bayer pattern (Figure 1c). Detailed information for the sensor is shown in Table 1.  
For the Bayer pattern sensor, only one color is captured by each detector during imaging, and the full red, green, and blue (RGB) three-color band information at each detector must be reconstructed by the Bayer interpolation algorithm in the ground image processing system (Figure 2a). A major advantage of the Bayer pattern sensor over conventional multispectral sensors is that the amount of data acquired is drastically reduced while the image color information is retained (Figure 2b); hence, they are more commonly used in video and low-cost micro remote sensing satellites and can expand the scope of application of image data, such as ship detection [1].  
The OVS satellite uses a Bayer pattern sensor to provide two imaging modes: the staring and push-broom modes. The staring mode uses all plane array detectors to focus on an individual target (Figure 3a) and can obtain 8 bits of video data with a frame rate of approximately 10-25 fps. The push-broom mode uses the Bayer partial row detectors to form multilevel time delay integration (TDI), which is then used to perform push-broom imaging along the flight direction of the satellite to obtain 10 bits of long strip data, as shown in Figure 3b. For OVS satellites, approximately 17,000 km\({}^{2}\) of data can be captured  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Ground swath & 22.5 km @ 500 km \\ Imaging mode & Staring video mode: frame rate: 10–25 fps \\  & Push-broom mode \\ Resolution & 0.9 m \\  & Video mode: 8 bits \\  & Push-broom mode: 10 bits \\ Color & Bayer pattern \\ Modulation Transfer Function & \(\geq\)0.12 @ Nyquist frequency \\ Signal To Noise Ratio & \(\geq\)35 dB (Sun elevation angle \(\geq\) 50\({}^{\circ}\)) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Detailed information for the OVS sensor.  
Figure 1: CMOS arrangement of the focal plane of the OVS satellite (**a**), “GRBG” Bayer pattern (**b**), and “GRBG” Bayer pattern (**c**).  
in each strip image. Contrary to the conventional linear push-broom mode, the Bayer pattern push-broom mode uses the Bayer pattern detector group, which utilizes two rows of imaging detectors as the smallest imaging unit. This achieves the same multi-level TDI function as the linear array push-broom satellite by increasing or decreasing the number of Bayer pattern rows. Figure 4 shows a comparison of a conventional linear array push-broom and a Bayer pattern push-broom. The imaging data in the push-broom direction is the imaging data collected by a single detector in a single band, while the Bayer pattern push-broom obtains data from multiple bands.  
Figure 4: Schematic of multi-level TDI in (**a**) a linear array push-broom sensor and (**b**) a Bayer pattern push-broom sensor.  
Figure 3: Schematic of Bayer sensor staring (**a**) and push-broom imaging (**b**).  
Figure 2: Workflow of Bayer color reconstruction (**a**) and a Bayer interpolation example image (**b**).