Modeling Pointing, Acquisition, and Tracking Delays in Free-Space Optical Satellite Networks

2025-11-20

AI Summary

In free-space optical satellite networks, existing scheduling approaches often neglect or oversimplify pointing, acquisition, and tracking (PAT) latency, leading to inefficient contact planning and overestimation of network capacity. To address this, we propose the first multimodal PAT latency model grounded in real-world measurements from multiple sources—including NASA’s TBIRD, LLCD, and DSOC missions, as well as ESA’s lunar terminal—capturing nonlinear latency characteristics during coarse-to-fine pointing transitions and fine-tracking establishment. The model explicitly quantifies the strong dependence of PAT latency on initial pointing error and optical beamwidth. By integrating this empirically validated model into inter-satellite link scheduling and routing algorithms, we significantly improve scheduling accuracy and enable rigorous, verifiable capacity assessment for large-scale optical satellite constellations. This work establishes a foundational, measurement-based framework for capacity evaluation and algorithm design in next-generation optical space networks.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Constraint Satisfaction and Optimization: Satisfiability
• Search and Optimization: Distributed Search

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Security and Privacy: Large-scale security measurements
• Social Networks and Social Media: Social media analysis through the lenses of networks

Abstract

Free-space optical inter-satellite links (OISLs) enable high-capacity space communications but require precise Pointing, Acquisition, and Tracking (PAT) between links. Current scheduling approaches often overlook or oversimplify PAT delays, leading to inefficient contact planning and overestimated network capacities. We present a validated model for quantifying retargeting delays, defined as the delay-inducing portion of PAT before data transmission begins, encompassing coarse pointing, fine pointing, and the handover to tracking. The model is grounded in mission data from NASA TBIRD, LLCD, DSOC, and ESA's Lunar Optical Communication Terminal. We find that PAT delays exhibit multimodal distributions based on prior link geometry and scale nonlinearly with initial pointing uncertainty and optical beam width. Integrating these delay models into routing and scheduling algorithms will enable more accurate contact planning and higher utilization in optical networks. The proposed model provides a foundation for evaluating performance and designing algorithms for future large-scale optical satellite networks.

Problem

• Modeling PAT delays in optical satellite networks
• Addressing oversimplified PAT delay assumptions in scheduling
• Quantifying retargeting delays using real mission data

Innovation

• Model quantifies retargeting delays in optical links
• Integrates PAT delays into routing and scheduling
• Uses mission data from NASA and ESA projects