Full Field-of-View Optical Calibration with Microradian-Level Accuracy for Space Laser Communication Terminals on LEO Constellation Applications

XIE Qingkun; XU Changzhi; BIAN Jingying; ZHENG Xiaosong; ZHANG Bo

doi:10.11999/JEIT250734

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XIE Qingkun, XU Changzhi, BIAN Jingying, ZHENG Xiaosong, ZHANG Bo. Full Field-of-View Optical Calibration with Microradian-Level Accuracy for Space Laser Communication Terminals on LEO Constellation Applications[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250734

Citation:

XIE Qingkun, XU Changzhi, BIAN Jingying, ZHENG Xiaosong, ZHANG Bo. Full Field-of-View Optical Calibration with Microradian-Level Accuracy for Space Laser Communication Terminals on LEO Constellation Applications[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250734

Citation:

XIE Qingkun, XU Changzhi, BIAN Jingying, ZHENG Xiaosong, ZHANG Bo. Full Field-of-View Optical Calibration with Microradian-Level Accuracy for Space Laser Communication Terminals on LEO Constellation Applications[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250734

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Full Field-of-View Optical Calibration with Microradian-Level Accuracy for Space Laser Communication Terminals on LEO Constellation Applications

doi: 10.11999/JEIT250734 cstr: 32379.14.JEIT250734

Xi'an Institute of Space Radio Technology, Xi’an 710100, China

Received Date: 2025-08-07
Accepted Date: 2025-11-05
Rev Recd Date: 2025-11-05

Available Online: 2025-11-15

Abstract

Abstract

Objective The coarse pointing assembly (CPA) serves as a core component in laser communication systems, enabling wide-field scanning, active orbit-attitude compensation, and dynamic disturbance isolation. To counteract multi-source disturbances such as orbital perturbations and attitude maneuvers, it is essential to develop a high-precision, high-bandwidth, and fast-response pointing, acquisition, and tracking (PAT) algorithm. Establishing a full field-of-view (FOV) optical calibration model between the CPA and the detector is critical to suppress image degradation caused by spatial pointing deviations. Conventional calibration methods typically employ ray tracing to simulate beam offsets and infer calibration relationships. However, they exhibit several inherent limitations, including: high modeling complexity arising from non-coaxial paths, multi-reflective surfaces, and freeform optics; susceptibility to systematic errors due to assembly tolerances, detector non-uniformity, and thermal drift; limited applicability across the full FOV resulting from spatial anisotropy. To overcome these technical barriers and ensure stable and reliable laser communication links, a high-precision calibration method applicable over the entire FOV is urgently needed. Methods To achieve precise CPA-detector calibration and overcome the shortcomings of traditional methods, this paper proposes a full field-of-view optical calibration method with microradian-level accuracy. Based on the optical design features of periscope-type laser terminals, an equivalent optical transmission model of the CPA is established and the mechanism of image rotation is analyzed. Leveraging the structural rigidity of the optical transceiver channel, the optical transmission matrix is simplified to a constant matrix, yielding a full-space calibration model that directly relates CPA micro-perturbations to the spot displacements. By correlating the CPA rotation angles between the calibration target points and the actual operating positions, the calibration task is further reduced to estimating the calibration matrix at the target points. Random micro-perturbations are applied to the CPA, inducing corresponding micro-displacements of the detector spot. A calibration equation based on the CPA motion and spot displacement is formulated, and the calibration matrix is accurately estimated via least-squares regression. Finally, the full-space calibration relationship between the CPA and detector is derived through matrix operations. Results and Discussions Based on the proposed calibration method, an experimental platform (Fig. 4) is built to conduct calibration and verification using a periscope laser terminal. Accurate measurements of the conjugate motion relationship between the CPA and the CCD detector spot are obtained (Tab.1). To comprehensively assess the calibration accuracy and full-space applicability, systematic verification is executed, including single-step static pointing and continuous dynamic tracking. In the static pointing verification, the mechanical rotary table is moved to three extreme diagonal positions, and the CPA performs open-loop pointing based on the established CPA-detector calibration relationship. Experimental results confirm that the spot accurately reaches the intended target position (Fig. 5), with a pointing accuracy of less than 12μrad (RMS). In the dynamic tracking experiment, the system control parameters are optimized to ensure stable tracking of the platform beam. During the low-angular-velocity motion of the rotary table, the laser terminal maintains stable tracking (Fig. 6). The CPA trajectory exhibits a clear conjugate relationship with the rotary table motion (Fig. 6(a), Fig. 6(b)), and the tracking accuracy in both orthogonal directions is less than 4 μrad (Fig. 6(c), Fig. 6(d)). Furthermore, the independence of the optical transmission matrix from calibration target point selection is discussed. By improving the spatial accessibility of calibration points, this method reduces operational complexity without compromising calibration precision. Strategic optimization of the spatial distribution of calibration points further enhances calibration efficiency and accuracy. Conclusions This paper proposes a full field-of-view optical calibration method with microradian-level accuracy, based on single-target micro-perturbation measurement. To meet the engineering requirements of rapid linking and stable tracking, a full-space optical matrix model for the CPA-detector calibration is built via matrix optics. Random micro-perturbations applied to the CPA at a single target point yield a generalized transfer equation, from which the calibration matrix is determined by the least-squares estimation. Experimental results demonstrate that this model effectively mitigates issues such as image rotation, mirroring, and tracking anomalies, suppressing calibration residuals below 12 μrad across the entire FOV and limiting the dynamic tracking error to within 5 μrad per axis. The method eliminates the need for additional hardware and complex alignment procedures, providing a high-precision, low-complexity solution that supports rapid deployment in the mass production of Low-Earth-orbit (LEO) laser terminals.
- Laser terminal,
- Micro-perturbation,
- Calibration,
- CPA

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References(21)

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