26. Strategy and Accuracy Analysis of Space-Borne GPS Single-Frequency Real-Time Orbit Determination

The real-time orbit determination for Low Earth Orbiters (LEOs) is generally based on dual-frequency tracking data from on-board GPS receivers, and positioning accuracies for LEOs currently vary from 0.5 to 1.0 m with sophisticated reduced dynamic orbit determination techniques. In this paper, different strategies are designed and applied to real-time orbit determination only using single-frequency pseudo-range and carrier phase measurements to analyze their corresponding performances. Then some simulative tests are carried out to process the GRACE-A space-borne GPS data in the different solar sunspot activities. The test results demonstrate that the position and velocity accuracy (3DRMS) are up to 0.9 m and 0.9 mm/s respectively using only single-frequency GPS pseudo-range data, and their accuracies could be improved to 0.55 m and 0.55 mm/s using single-frequency combination of pseudo-range and carrier phase measurements, which is close to the dual-frequency real-time orbit determination. Therefore a low-cost single frequency space-borne GPS receiver can be used in real-time orbit determination for LEO missions when appropriate strategies and methods would be selected.