| The new generation geosynchronous remote sensing satellite is a three-axis-stabilized platform satellite, on which the two-dimensional imaging of radiometers can only be realized by way of mechanical scanning. With this mechanism based on double-scan-mirror, one scan-mirror in the south-north direction and the other in the east-west direction moves independently, and their shafting are orthogonal. Within satellites’ field-of-view of the earth 18°×18°, the requirements that dynamic precision of the scanning is up to 1″(1σ). Then, the evaluating of scan-mirror’s dynamic precision in working mode has become a challenge. In this paper, we conduct our study during the process from the proposal of the scan-mirror’s dynamic precision measurements based on the digital imaging technique, to the system building, as well as the image information processing, the method arguments, and the method implementation.Firstly, this paper proposes the method of the scan-mirror’s dynamic precision measurements based on the digital imaging technique, which means measuring the scan-mirror’s dynamic precision by by detecting the deviation between the pixels’ positions of scanning image and the ideal image given a standard image scene. We choose a target plate with a 13×13 diamond array as the standard scene map, lighting the target board by the integrating sphere and transporting the the light to the scan-mirror through a collimator. The scan-mirror scans the light and the radiometer imaged the target plate. This paper makes a detailed analysis of the selection of the pattern on the standard plate, the designation of dimension parameter of the standard plate, the selection of material of the standard plate, the choice of lighting systems and the index of the projection system(collimator).Secondly, one of the biggest vitue of the proposed measuring method lies in the digital image information processing of the scanning image. Treating the corner and centroid point as the feature points of the scanning image, we detect the positions of them and then calculate the precision of scanning. We use the Harris Affine corner detection algorithm to detect the corner point and use the traditional centroid detection algorithm to detect the centroid point. Each detection algorithm’s precision simulation will be discussed in detail in this paper.Thirdly, we demonstrate the precision of the proposed method by simulation and experiment. According to the experiment of the precision of the proposed method with manual subpixel shift image series, the precision of proposed method based on corner point reaches 0.56~0.91urad(1σ), the precision of proposed method based on centroid point reaches 0.56~0.84urad(1σ). They both meet the demand of measurement of FY-4 radiometer’s scan-mirror’s dynamic precisionFinally, based on the built system, under the scan-mirror’s 10°/s scanning mode, we employ the angle measurement method to test the dynamic precision of the scan-mirror. We get the result that within the standard plate’s little field of view(0.33°×0.33°), the dynamic precision of the scan-mirror reaches 2.64urad(1σ, 0.54″).Though the above four arrangements of the study, this paper puts forward and demonstrates the dynamic angle measurement method of the scanning mirror dynamic precision based on the digital image processing technique, which produces an excellent measurement result and accuracy. This study provides an available reference to the measurement of the scan-mirror dynamic precision within the large field of view(18°×18°) under the scan mirror’s working mode.The innovative points of whole method study lie in that the proposed method is based on the scanning and imaging working principle of the radiometer, and measures the scanning mirror’s dynamic precision by way of processing the image information and detecting the pixel’s location. The method realizes the dynamic precision measurement of the scan-mirror under the dynamic scanning process in a true sense. Besides, the measuring precision is improved by the imaging technique.
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