Impact of receiver architecture on small satellite optical link in the presence of pointing jitter

Vibration Detection and Degraded Image Restoration of Space Camera Based on Correlation Imaging of Rolling-Shutter CMOS

To mitigate the influence of satellite platform vibrations on space camera imaging quality, a novel approach is proposed to detect vibration parameters based on correlation imaging of rolling-shutter CMOS. In the meantime, a restoration method to address the image degradation of rolling-shutter CMOS caused by such vibrations is proposed. The vibration parameter detection method utilizes the time-sharing and row-by-row imaging principle of rolling-shutter CMOS to obtain relative offset by comparing two frames of correlation images from continuous imaging. Then, the space camera's vibration parameters are derived from the fitting curve parameters of the relative offset. According to the detected vibration parameters, the discrete point spread function is obtained, and the rolling-shutter CMOS image degradation caused by vibration is restored row by row. The verification experiments demonstrate that the proposed detection method for two-dimensional vibration achieves a relative accuracy of less than 1% in period detection and less than 2% in amplitude detection. Additionally, the proposed restoration method can enhance the MTF index by over 20%. The experimental results demonstrate that the detection method is capable of detecting high-frequency vibrations through low-frame-frequency image sequences, and it exhibits excellent applicability in both push-scan cameras and staring cameras. The restoration method effectively enhances the evaluation parameters of image quality and yields a remarkable restorative effect on degraded images.

Study on the Influence of Random Vibration of Space-Based Payload on Area-Array Camera Frame-by-Frame Imaging

Satellite vibration is an important factor that can seriously reduce the image quality of remote sensing imaging. In this paper, the influence of the random vibration of the payload on the frame-by-frame imaging quality of the area-array CMOS camera is studied. Firstly, the mode of the camera’s dynamic frame-by-frame imaging is established; secondly, the curvature mapping function between the ground and camera focal planes is derived based on the invariance of the field of view (FOV). The frequency domain-filtered template of random vibration is constructed. Then, the distortion and degradation images, of single-frame images at different attitude angles, are inversed; finally, the influence of attitude angle, exposure time, and the error of velocity, caused by random vibrations on dynamic frame-by-frame imaging, are analyzed. The simulation results show that the degree of image edge distortion gets larger when the attitude angle increases from 0° to 50°. At the same time, the MTF decreases rapidly with the increase of the error of velocity and the attitude angle. Meanwhile, when the output-image SSIM decreases by 0.1, the MSE increases by 18.5. The experimental results show that the field of view (FOV) of dynamic imaging should be reasonably set, and the error of velocity should be effectively reduced to obtain high-quality remote sensing images.

Angular micro-vibration of the Micius satellite measured by an optical sensor and the method for its suppression

Satellite angular micro-vibration has an important impact on the efficiency of space quantum communication links. We measured the micro-vibrations on the Micius satellite in orbit using a high-precision optical sensor mounted on the satellite and analyzed the power spectral density. We designed a compound axis acquisition, tracking, and pointing (ATP) system based on a two-axis turntable and tested its suppressive effect on the micro-vibration through in-orbit experiments. The tracking error caused by the angular micro-vibration was found to be 9.3 µrad, with the energy concentrated primarily in the frequencies below 30 Hz; after suppression by the ATP system, the error was 0.47 µrad.