Abstract: Precision Orbit Determination for High-Orbit Satellites Using Satellite-borne GNSS Alone is Challenging, While BDS Inter-Satellite Ka-band Measurements Exhibit High Accuracy and Favorable Geometric Distribution. Validation of Precision Orbit Determination Performance with Joint Ka-band and Satellite-borne GNSS Simulated Observations. Experimental results indicate that, compared to satellite-borne GNSS alone, the three-dimensional root mean square error decreased from 729.9 mm to 480.0 mm, resulting in a 34.2% improvement in orbit precision when only one BDS satellite is visible. With visibility of two BDS satellites, the three-dimensional orbit error decreased to 401.6 mm, and the radial root mean square error reduced from 269.8 mm to 137.8 mm relative to GNSS, leading to a 48.9% improvement in orbit precision. When GNSS is combined with all visible BDS satellites, the three-dimensional orbit precision can reach 269.4 mm. The introduction of BDS inter-satellite Ka-band measurements enhances the precision of high-orbit satellite orbit determination and increases orbit reliability.