Feasibility of Using Synthetic Aperture Radar to Aid UAV Navigation.

Area of Science:

• Aerospace Engineering
• Geophysics
• Remote Sensing

Background:

• Inertial Navigation Systems (INS) in Medium-Altitude Long-Endurance (MALE) Unmanned Aerial Vehicles (UAVs) are prone to drifts over long distances.
• Accurate navigation is critical for MALE UAVs carrying heavy payloads like Synthetic Aperture Radar (SAR) systems.
• Existing navigation systems may not provide sufficient accuracy for precise trajectory adherence over extended flights.

Purpose of the Study:

• To investigate the feasibility of using onboard SAR imagery as a backup navigation system for MALE UAVs.
• To develop and assess methods for correcting UAV position and attitude errors using SAR data.
• To determine system requirements for a SAR-based navigation augmentation system.

Main Methods:

• Utilizing both amplitude and phase information from onboard SAR images to infer UAV position and attitude.
• Employing an amplitude-based approach by matching ground landmarks in SAR images with known coordinates.
• Leveraging SAR interferometry with a reference Digital Terrain Model (DTM) when amplitude-based methods are not feasible.

Main Results:

• A feasibility analysis was conducted, considering radiometric and geometric acquisition parameters.
• The proposed SAR-based navigation system demonstrated the potential to bound UAV coordinate errors within ±12 meters.
• The study confirmed the viability of integrating SAR systems with commercial navigation sensors and available DTMs for enhanced UAV guidance.

Conclusions:

• A SAR-based backup navigation system is feasible for MALE UAVs, significantly improving positional accuracy.
• The integration of SAR amplitude and phase data offers a robust solution for mitigating INS drift.
• This technology enhances the operational capabilities of long-endurance UAVs by ensuring reliable navigation over extensive trajectories.