Precise (sub-meter level) real-time navigation using a space-capablesingle-frequency global positioning system (GPS) receiver and ultra-rapid(real-time) ephemerides from the international global navigation satellitesystems service is proposed for low-Earth-orbiting (LEO) satellites. The C/Acode and L1 carrier phase measurements are combined and single-differenced toeliminate first-order ionospheric effects and receiver clock offsets. Arandom-walk process is employed to model the phase ambiguities in order toabsorb the time-varying and satellite-specific higher-order measurement errorsas well as the GPS clock correction errors. A sequential Kalman filter whichincorporates the known orbital dynamic model is developed to estimate orbitalstates and phase ambiguities without matrix inversion. Real flight data fromthe single-frequency GPS receiver onboard China's SJ-9A small satellite areprocessed to evaluate the orbit determination accuracy. Statistics frominternal orbit assessments indicate that three-dimensional accuracies of betterthan 0.50 m and 0.55 mm/s are achieved for position and velocity, respectively.
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机译：针对低地球轨道，提出了使用具有空间功能的单频全球定位系统（GPS）接收器和来自国际全球导航卫星系统服务的超快速（实时）星历表进行的精确（亚米级）实时导航（LEO）卫星。 C / Acode和L1载波相位测量结合在一起并进行单差分，以消除一阶电离层效应和接收器时钟偏移。为了吸收时变和特定于卫星的高阶测量误差以及GPS时钟校正误差，采用了Arandom-walk过程对相位模糊度进行建模。开发了结合已知轨道动力学模型的顺序卡尔曼滤波器，以估计轨道状态和相位模糊度，而无需矩阵求逆。处理来自中国SJ-9A小卫星上单频GPS接收机的真实飞行数据，以评估定轨精度。内部轨道评估的统计数据表明，位置和速度的三维精度分别优于0.50 m和0.55 mm / s。
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