An inertial navigation method augmented by Signals of Opportunity (SOPs) of three low earth orbit (LEO) constellations is presented. The downlink signal characteristics of the Iridium-NEXT, Orbcomm, and Globalstar LEO constellations are discussed. Furthermore, a tightly coupled integration model of the inertial navigation system and high-order LEO-SOP Doppler measurement model is designed. We presented a second-order measurement model of the LEO-SOP/INS integration using a second-order extended Kalman filter in which all the unknown states of the receiver and LEO satellites are estimated. The state parameters of the second-order EKF model are the position and velocity of both the receiver and the satellites, as well as the receiver’s orientation, the clock bias, and clock drift of the LEO satellites, and the constant bias of the Inertial Measurement Unit. An experiment is performed using a ground aerial vehicle equipped with a Multi-Constellation Software-Defined Receiver (MC-SDR). The Doppler measurements are provided by observing the downlinks from multiple satellites of the Iridium-NEXT and Orbcomm constellations. As well, the predicted measurement of a Globalstar satellite is used in the designed model. The results show the positioning accuracy of less than 10 m being achieved during a dynamic ground experiment, representing an 82% precision gain as compared against the regular single constellation EKF method.

提出了一种由三个低地球轨道 (LEO) 星座的机会信号 (SOP) 增强的惯性导航方法。讨论了 Iridium-NEXT、Orbcomm 和 Globalstar LEO 星座的下行信号特性。此外，设计了惯性导航系统与高阶LEO-SOP多普勒测量模型的紧密耦合集成模型。我们使用二阶扩展卡尔曼滤波器提出了 LEO-SOP/INS 集成的二阶测量模型，其中估计了接收器和 LEO 卫星的所有未知状态。二阶EKF模型的状态参数是接收机和卫星的位置和速度，以及接收机的方位、LEO卫星的时钟偏差和时钟漂移，和惯性测量单元的恒定偏差。使用配备多星座软件定义接收器 (MC-SDR) 的地面飞行器进行实验。多普勒测量是通过观察来自 Iridium-NEXT 和 Orbcomm 星座的多颗卫星的下行链路来提供的。同样，在设计模型中使用了 Globalstar 卫星的预测测量值。结果表明，在动态地面实验中，定位精度小于 10 m，与常规单星座 EKF 方法相比，精度提高了 82%。多普勒测量是通过观察来自 Iridium-NEXT 和 Orbcomm 星座的多颗卫星的下行链路来提供的。同样，在设计模型中使用了 Globalstar 卫星的预测测量值。结果表明，在动态地面实验中，定位精度小于 10 m，与常规单星座 EKF 方法相比，精度提高了 82%。多普勒测量是通过观察来自 Iridium-NEXT 和 Orbcomm 星座的多颗卫星的下行链路来提供的。同样，在设计模型中使用了 Globalstar 卫星的预测测量值。结果表明，在动态地面实验中，定位精度小于 10 m，与常规单星座 EKF 方法相比，精度提高了 82%。