High-Precision Time Synchronization and Autonomous Maintenance for LEO Satellite Constellations Based on...

Area of Science:

• Space engineering
• Satellite technology
• Network synchronization

Background:

• Large-scale Low Earth Orbit (LEO) constellations necessitate autonomous time synchronization.
• Existing methods often rely on expensive atomic clocks or Global Navigation Satellite System (GNSS) signals, posing cost and power challenges.
• A low-cost, low-power, autonomous solution is critical for LEO constellation operations.

Purpose of the Study:

• To propose and validate an autonomous time synchronization method for LEO constellations.
• To enable high-precision time synchronization using only high-stability crystal oscillators.
• To eliminate the need for onboard atomic clocks or external GNSS timing references.

Main Methods:

• Development of a satellite-to-ground link visibility time model based on orbital parameters.
• Construction of a discrete state-space model including temperature-induced frequency perturbation compensation.
• Application of a combined Kalman filtering and Linear Quadratic Regulator (LQR) control framework for synchronization and maintenance.

Main Results:

• Achieved time synchronization performance better than 5 ns (1σ) and peak-to-peak error below 30 ns in simulations.
• Demonstrated effectiveness under a Walker-Delta constellation configuration at 800 km altitude and 55° inclination.
• Validated the method's suitability for typical LEO constellation applications requiring precise timing.

Conclusions:

• The proposed method offers a high-precision, autonomous time synchronization solution for LEO constellations.
• It meets the stringent timing requirements for applications like communication scheduling and critical infrastructure services.
• The decentralized nature and local time signal output make it ideal for large-scale satellite networks.