Lower power consumption laser tracking with dynamic shaping beam in cross-orbit inter-satellite links

Inter-satellite optical communication (ISOC) provides satellite constellations with large-capacity, high-bandwidth, and energy-efficient links. However, in cross-orbit inter-satellite link scenarios, the significant relative velocity between satellites introduces severe tracking challenges, leading to pronounced asymmetric pointing errors. Conventional tracking approaches that employ symmetric circular beams struggle to match such asymmetric error distributions, resulting in an inefficient use of optical power and an increased probability of link outages. To address this issue, this study proposes a lower power consumption tracking method based on asymmetric elliptical beam shaping, specifically designed to enhance link availability and energy efficiency in cross-orbit ISOC. First, the study modeled the pointing error distribution under closed-loop tracking as a bivariate normal distribution. Using a conservative approximation, the study derived a closed-form analytical expression for the link availability and determined the optimal beam divergence angles that minimize the transmit power while satisfying the availability constraints. Simulations are first used to validate the theoretical analysis and then emulate an entire cross-orbit inter-satellite laser communication process. The results demonstrate that during periods of strong pointing error anisotropy, the proposed asymmetric elliptical beam shaping strategy reduces the total energy consumption by 79% compared to conventional circular beams, with instantaneous power savings of up to 90%. Furthermore, this study establishes a practical decision criterion based on the characteristics of the error distribution for selecting between symmetric circular and asymmetric elliptical beam config.urations. Finally, this study experimentally verified the proposed method under far-field equivalent conditions using a liquid crystal on silicon spatial light modulator. The experimental results confirmed that, under identical link availability requirements, the asymmetric elliptical beam exhibited superior robustness and significantly lower power demand than the symmetric circular beam, thereby validating the effectiveness of the proposed approach.