Abstract: Objective: Maintaining high-precision orbits for low earth orbit satellites is essential for advanced Earth observation and navigation systems. This study investigated real-time precise orbit determination using gravity recovery and climate experiment follow-on (GRACE-FO) satellite data based on global navigation satellite system (GNSS) and accelerometer, specifically focusing on precise orbit determination and orbit maintenance during GNSS-denied conditions (signal degradation or loss). The key aim was to evaluate the improvement in orbit accuracy from integrating onboard accelerometer data, particularly during geomagnetic storms. Methods: Following an initial study of orbit determination accuracy during geomagnetically quiet periods, this paper assesses the precision gain from using accelerometer data over conventional empirical models for real-time orbit determination. When both strategies showed comparable accuracy, we then investigated their performance differences during geomagnetic storms. This included evaluating both real-time orbit determination and orbit maintenance accuracy under different denial lengths in navigation-denied scenarios. Results: During quiet periods with unimpeded GNSS signals, both strategies delivered similar real-time orbit determination accuracy, better than 30 cm. Under geomagnetic storm conditions, the accelerometer-assisted strategy achieved orbit determination accuracy better than 40 cm, outperforming the conventional strategy by an average of 31%. In simulated GNSS-denied conditions during storms, accelerometer data significantly improved orbit maintenance accuracy: 30 minute and 60 minute accuracies were better than 50 cm, and 200 minute accuracy was better than 150 cm (by an average of 87% improvement) compared to conditions without accelerometer data. Conclusions: Integrating on-board GNSS and accelerometer data for real-time orbit determination and maintenance during GNSS-denied conditions effectively maintains orbit accuracy during geomagnetic storms. This strategy sustains precision levels comparable to those achieved in quiet periods, demonstrating a strong capability for robust orbit accuracy maintenance under disturbed space weather conditions.