### Relative Radiometric Calibration  
The Bayer pattern sensor of OVS satellites has 5056 \(\times\) 2968 detectors, each of which has its own unique physical properties, such as size and filter performance, which has resulted in detector response inconsistency, non-uniform electronic sensor biases, inconsistencies in the fixed-noise and dark current, and differences in the output circuit. Therefore, each detector in the sensor that images uniform radiance will output specific digital numbers (DN), resulting in numerous examples of stripe noise in the raw image recorded by the sensor. This degrades image quality and poses a risk to its suitability, which is required for analysis (Figure 5a). Relative radiometric calibration aims to calibrate inconsistencies in terms of sensor detector responses, eliminating detector-level striping artifacts (Figure 5c). When Bayer sensors lack relative radiometric calibration, their direct color interpolation may produce incorrect results. Figure 5b shows that the Bayer color interpolation algorithm enhances detector-level errors in raw Bayer pattern data, disturbing interband color information. Figure 5c shows the visual effect of Bayer color reconstruction after relative calibration. The RGB color information of a raw Bayer image can be completely covered, indicating that before Bayer interpolation processing, relative radiometric calibration must be performed to eliminate the detector-level radiometric error and improve the image quality of the Bayer color reconstruction image. Several radiometric calibration and correction methods have been widely developed by researchers to reduce these radiometric errors [2; 3; 4; 5; 6]. OVS satellites are low-cost microsatellite and are not equipped with on-board calibration equipment. Therefore, a calibration method based on earth images must be selected. In the staring imaging mode for the OVS, the Bayer sensor can be equivalent to the plane array video sensor, and on-orbit relative radiometric calibration can be accomplished using the sequence frame data, such as the uniform filed calibration of the SkySat satellites [7], Luojia1-01 satellite [8], and calibration without the uniform filed data of Jilin video satellites [9]; however, Bayer sensor push-broom imaging differs from the conventional linear push-broom mode because the imaging data in the push-broom direction is collected by a single band, but the Bayer pattern push-broom obtains data from multiple bands. Due to different bands having different radiometric response characteristics, each band of remote sensing sensors must be calibrated independently. The conventional methods include uniform field calibration [10; 11], statistical calibration [12; 13], yaw calibration [14; 15; 16], and fieldless calibration [17; 18], which are designed for linear push-broom sensors and cannot be directly applied to Bayer pattern sensors. Nevertheless, OVS push-broom imaging characteristics provide a possibility for the relative calibration of the Bayer array push-broom mode by referring to the statistical calibration principle of linear array push-broom remote sensing satellites. Based on the principle of consistent gray distribution of each imaging detector under the condition of massive samples, this study developed an on-orbit relative radiometric calibration method for the plane array Bayer push-broom imaging mode, which reconstructs the order of each detector within the Bayer pattern sensor and converts it into a virtual linear array sensor to separate the RGB three-band components from the Bayer pattern. For this, a positioning method linked by \"lineounters\" was designed to detect the specific position of  
Figure 5: Uniform ocean zone images captured from an OVS Bayer sensor: (**a**) raw Bayer data, (**b**) color reconstructed image without relative radiometric calibration, and (**c**) color reconstructed image after relative radiometric calibration. each detector within each Bayer pattern, and a nonlinear calibration model was used to solve the calibration coefficients.