The Technology
Deep space navigation, particularly for spacecraft beyond lunar orbit, currently relies on traditional terrestrial systems such as NASA’s Deep Space Network (DSN) and ESA’s ESTRACK. These networks employ Very Long Baseline Interferometry (VLBI) for angular positioning. While exceptionally accurate, these ground-based systems face several significant challenges such as, limited angular resolution for deep space targets. Atmospheric distortions, Reduced Line-of-Sight (LOS) availability due to Earth’s rotation and curvature, at least two simultaneously visible ground stations are available for only about 50% of the time during a diurnal cycle and high demand and limited access making it difficult for additional missions to secure sufficient observation time.
Radiometric Interferometry Navigation by GEO Satellites (RINGS) proposes a complementary deep space navigation approach using space-based interferometry. The RINGS system replaces terrestrial VLBI stations with dual Geostationary Earth Orbit (GEO) satellites. These GEO satellites, positioned at widely separated longitudes (e.g., 180° apart), form a space-based interferometric baseline. During a measurement session, the target spacecraft’s radio signal is simultaneously received by both GEO satellites, time-stamped, and stored onboard. These observations are then downloaded to ground stations and forwarded to a central processing facility, where they are time-aligned and cross-correlated to extract phase differences for precise angular localization.
The RINGS system addresses and overcomes the fundamental limitations of terrestrial VLBI, offering a more robust and efficient solution for deep space navigation. GEO satellites can be separated by over 80,000 km, providing an order of magnitude greater effective baseline than the ~8,000 km baselines of ground-based systems. They eliminate Atmospheric Errors. The systems allows near-continuous visibility. Simulations show 98% availability for interferometric tracking, nearly doubling the ~49.66% availability of terrestrial VLBI arrays while keeping a total angular error of approximately 3.73 nanoradians, which is within the same order of magnitude as terrestrial VLBI’s 2.39 nanoradians.
Advantages
- Angular measurement precision enhancement.
- Complete elimination of atmospheric phase errors
- Near-continuous visibility and higher measurement availability (98%)
Applications
- Deep space navigation and spacecraft tracking beyond lunar orbit.
- Deep space orbit determination (OD).
- Supporting real-time Guidance and Control (G&C) operations for deep space missions.
- Interplanetary CubeSats and small spacecraft with limited transmission power and onboard resources.
- Missions where terrestrial station geometry limits availability or accuracy.
- The growing number of deep space and interplanetary missions requiring continuous tracking
Business Development Contacts
