Real-time GNSS-based applications require corresponding real-time orbit products. While traditional GNSS orbits are generated with the dual-frequency IF (Ionosphere-Free) model, the increase of multi-frequency signal satellites brings new challenges for the data processing. Therefore, real-time orbit determination with the multi-frequency UC (Uncombined) model is introduced in this study considering its flexibility. With the derived mathematical model conforming to IGS (International GNSS Service) dual-frequency clock definition and one-week triple-frequency Galileo observation data from 90 IGS network stations, the convergence and accuracy of real-time orbits is assessed and the characteristics of satellite IFCB (Inter-Frequency Clock Bias) are analyzed. Results indicate that the model differences, including dual-frequency IF model, dual-frequency UC model and triple-frequency UC model, contribute to only cm-level differences with CODE (Center for Orbit Determination in Europe) final orbits after a convergence time of around 12 h. The constellation-mean RMS (Root Mean Square) differences of the converged real-time orbits with the CODE final orbits reaches about 5.0 cm, 7.0 cm and 5.0 cm for the radial, tangential and normal directions. The convergence of satellite IFCB is much faster than that of satellite orbit, which reflects a loose correlation between these two parameters. While the Galileo satellite IFCB are temporally stable, the modeling of satellite IFCB may be unreliable when over constrained and becomes even more unstable with commonly encountered datum changes. In summary, real-time GNSS orbit determination with multi-frequency raw observations is feasible and extendable with proper treatment of IFCB.

基于GNSS的实时应用程序需要相应的实时轨道产品。尽管传统的GNSS轨道是通过双频IF（无电离层）模型生成的，但多频信号卫星的增加为数据处理带来了新的挑战。因此，考虑到它的灵活性，在本研究中引入了使用多频UC（非组合）模型进行实时轨道确定的方法。利用推导的符合IGS（国际GNSS服务）双频时钟定义的数学模型和来自90个IGS网络站的一周三频Galileo观测数据，评估了实时轨道的收敛性和准确性，并评估了卫星的特性分析了IFCB（频率间时钟偏差）。结果表明，模型差异包括双频IF模型，双频UC模型和三频UC模型在大约12 h的收敛时间后，仅与CODE（欧洲轨道确定中心）的最终轨道产生厘米级的差异。收敛的实时轨道与CODE最终轨道的星座平均RMS（均方根）差在径向，切向和法线方向分别达到约5.0 cm，7.0 cm和5.0 cm。卫星IFCB的收敛快于卫星轨道的收敛，这反映了这两个参数之间的松散相关性。尽管伽利略卫星IFCB在时间上是稳定的，但当卫星IFCB受到过度约束时，其建模可能会变得不可靠，并且在遇到常见的基准面变化时会变得更加不稳定。总之，