Weak and Dynamic GNSS Signal Tracking Strategies for Flight Missions in the Space Service Volume.

Area of Science:

• Space Navigation
• Satellite Systems Engineering
• Signal Processing

Background:

• Space navigation using Global Navigation Satellite Systems (GNSS) faces challenges with weak signals and high dynamics in the Space Service Volume (SSV).
• Conventional third-order phase-locked loop (PLL) architectures in onboard GNSS receivers are insufficient for these demanding conditions.
• Maintaining signal lock is critical for accurate positioning and trajectory determination in space missions.

Purpose of the Study:

• To address the limitations of conventional GNSS receivers in weak-signal and high-dynamic space environments.
• To introduce and evaluate novel tracking strategies for enhanced GNSS performance in the SSV.
• To improve the robustness and reliability of space navigation systems.

Main Methods:

• An adaptive four-state Kalman filter (KF) algorithm was developed to optimize loop noise bandwidth by adaptively adjusting filter gain based on signal power and line-of-sight (LOS) dynamics.
• An open-loop tracking strategy, aided by an Inertial Navigation System (INS), was proposed to maintain signal lock in challenging environments.
• The traditional maximum likelihood estimation (MLE) method was modified non-coherently by reconstructing the likelihood cost function.

Main Results:

• The adaptive four-state KF-based strategy demonstrated effectiveness under non-maneuvering conditions, optimizing loop performance.
• The INS-assisted open-loop tracking strategy proved advantageous during maneuvering conditions, maintaining reliable tracking.
• Computer simulations validated the performance improvements of both proposed strategies under different mission scenarios.

Conclusions:

• The adaptive KF strategy offers significant improvements for GNSS receivers in stable space trajectories.
• INS-assisted methods are crucial for robust GNSS tracking during dynamic orbital maneuvers.
• These advancements enhance the capabilities of GNSS for future space navigation applications.