Abstract
<jats:p>Radiometric interferometry is a powerful technique for angular spacecraft navigation, traditionally implemented through ground-based Very Long Baseline Interferometry (VLBI) and Delta Differential One-Way Ranging. A previously proposed concept, Radiometric Interferometry Navigation using GEO Satellites (RINGS), replaces terrestrial VLBI stations with geostationary satellites in order to create a space-based interferometric baseline for deep-space navigation. The present paper extends the initial RINGS concept by developing a time-position error analysis and by evaluating the impact of practical clock and GEO orbit-determination uncertainties on the reconstructed angle of arrival. The analysis focuses on two main practical error sources: residual relative clock misalignment between the GEO satellites and uncertainty in the GEO station positions that define the interferometric baseline. First, analytical models are developed to map clock timing error and GEO baseline uncertainty into angular error. The clock analysis shows that timing-induced path error is divided by the long GEO-GEO baseline, providing a baseline-leverage advantage relative to terrestrial VLBI. The paper then evaluates GNSS-based synchronization, passive-hydrogen-maser-class clock stability, two-way inter-satellite synchronization and ranging, relativistic and moving-endpoint timing corrections, and GEO orbit-determination uncertainty. A Monte Carlo simulation framework is then used to propagate clock and position perturbations through a dual-frequency RINGS angle-of-arrival estimator. The results show that picosecond to tens-of-picoseconds residual timing errors contribute only small stochastic angular scatter when considered alone. After PHM-class timing and two-way inter-satellite synchronization, a 10ps residual timing level contributes approximately 0.04nrad for a 120∘ three-GEO baseline, while a conservative 100ps residual contributes approximately 0.4nrad. GEO position uncertainty is found to be the dominant error driver once meter-level orbit-determination errors are assumed. Under sub-meter GEO baseline knowledge and picosecond-level inter-satellite synchronization, the simulations support nanoradian-level angular performance. The results strengthen the feasibility case for GEO-based VLBI as a complementary deep-space navigation observable. The main practical requirements identified are accurate relative GEO-GEO baseline knowledge, high-stability onboard timing, two-way inter-satellite synchronization and ranging, deterministic timing-correction modeling, and robust phase-ambiguity resolution.</jats:p>