Low Earth orbit (LEO) satellite links experience rapid angular variation due to high orbital velocities, which causes severe beam misalignment and array gain degradation under conventional fixed-antenna architectures. In this letter, we propose a rotatable antenna (RA)-enabled LEO communication framework, where RA arrays are deployed at both the satellite and the ground node (GN) to exploit antenna boresight reconfiguration as an additional spatial degree-of-freedom (DoF) for maintaining directional alignment under high mobility. By leveraging the rank-one line-of-sight (LoS) channel structure inherent to satellite links, we derive closed-form solutions for the joint design of the transmit/receive beamforming and antenna boresight directions, revealing that optimal performance can be achieved via decoupled alignment across antennas with low computational complexity. To enable practical operation under dynamic conditions, we further develop a channel estimation and beam tracking protocol that exploits the predictable satellite orbit to continuously update boresight directions with low training overhead. Simulation results demonstrate that the proposed RA-enabled design significantly outperforms fixed and random boresight baselines in terms of achievable rate and robustness to angular variations, highlighting the effectiveness of rotational spatial reconfiguration in high-mobility satellite communications.

翻译：低地球轨道（LEO）卫星链路因高速轨道运动造成快速角度变化，在传统固定天线架构下会导致严重的波束失准与阵列增益退化。本文提出一种基于可旋转天线（RA）的LEO通信框架，在卫星与地面节点（GN）两端部署RA阵列，将天线波束指向重构作为额外的空间自由度（DoF），以在高机动条件下维持方向对准。通过利用卫星链路固有的秩一线视距（LoS）信道结构，我们推导出发送/接收波束成形与天线波束指向联合设计的闭式解，揭示了通过天线间的解耦对准可低计算复杂度实现最优性能。为在动态条件下实现实际运行，我们进一步开发了信道估计与波束跟踪协议，利用可预测的卫星轨道持续更新波束指向方向并降低训练开销。仿真结果表明，所提出的RA架构在可实现速率与角度变化鲁棒性方面显著优于固定与随机波束指向基准方案，凸显了旋转空间重构在高机动卫星通信中的有效性。