Space exploration missions generate rapidly increasing volumes of scientific telemetry that far exceed the capacity of today's manually scheduled, RF-based deep-space infrastructure. Free-space optical (FSO) communications promise orders of magnitude higher throughput, but their narrow beams require precise pointing, acquisition, and tracking (PAT) for link establishment and tightly synchronized contact schedules. Critically, no existing contact plan design (CPD) framework accounts for optical head retargeting delay, the time spent during coarse pointing and link acquisition before data transmission begins, which directly reduces usable contact time. Retargeting delay is the dominant impairment unique to optical networks, which induces a seconds-to-minutes-long mechanical pointing process for an optical terminal's laser from its current partner to the next receiver. This paper introduces the first PAT-aware CPD framework for optical interplanetary backhaul networks. The model captures directional temporal flows across both direct-to-Earth optical links and two-hop relay paths using delay/disruption-tolerant networking (DTN) satellites. We also introduce an optical network duty-cycle metric that quantifies the proportion of time spent transmitting to the contact window duration, exposing capacity lost to retargeting delay. Our results show that our MILP scheduler delivers over 30 percent higher network capacity than a greedy algorithm. More importantly, the results uncover a fundamental behavioral shift: when retargeting delays are modeled accurately, optimal schedules favor fewer but longer optical links that maximize throughput while minimizing retargeting overhead. These findings demonstrate that zero-delay assumptions substantially overestimate achievable performance and yield unrealistic contact plans.

翻译：太空探索任务产生的科学遥测数据量正快速增长，已远超当前基于射频技术、人工调度的深空基础设施承载能力。自由空间光通信虽有望实现数量级提升的吞吐量，但其窄波束特性要求精确的指向、捕获与跟踪过程以建立链路，并需要严格同步的接触调度方案。关键问题在于，现有接触计划设计框架均未考虑光学终端重定向延迟——即在数据传输开始前进行粗指向与链路捕获所耗费的时间，这会直接减少可用接触时长。重定向延迟是光网络特有的主要性能限制因素，它导致光终端激光器从当前通信对象转向下一接收器时，需经历数秒至数分钟的机械指向过程。本文首次提出面向星际光骨干网络的PAT感知型接触计划设计框架。该模型通过延迟/中断容忍网络卫星，刻画了直达地球光链路与双跳中继路径中的定向时空流。同时，我们提出光网络占空比度量指标，用以量化传输时间占接触窗口时长的比例，从而揭示因重定向延迟损失的通信容量。实验结果表明：相较于贪婪算法，我们的混合整数线性规划调度器可提升超过30%的网络容量。更重要的是，研究揭示了一个根本性行为转变：当精确建模重定向延迟时，最优调度方案倾向于选择数量更少但持续时间更长的光链路，在最大化吞吐量的同时最小化重定向开销。这些发现表明，零延迟假设会严重高估实际可达性能，并产生不切实际的接触计划。