In this simulation study we analyze the benefit of ground-space optical two-way links (OTWL) for Galileo precise orbit determination (POD). OTWL is a concept based on continuous wave laser ranging and time transfer with modulated signals from and to ground stations. The measurements are in addition to Global Navigation Satellite System (GNSS) observations. We simulate the measurements with regard to 16 Galileo Sensor Stations. In the simulation study we assume that the whole Galileo satellite constellation is equipped with terminals for OTWL. Using OTWL together with Galileo L-band, in comparison with an orbit solution calculated with L-band-only, demonstrates the advantage of combining two ranging techniques with different influences of systematic errors. The two-way link allows a station and satellite clock synchronization. Furthermore, we compare the ground-space concept with the satellite-to-satellite counterpart known as optical two-way inter-satellite links (OISL). The advantage of OTWL is the connection between the satellite system and the solid Earth as well as the possibility to synchronize the satellite clocks and the ground station clocks. The full network, using all three observation types in combination is simulated as well. The possibility to estimate additional solar radiation pressure (SRP) parameters within these combinations is a clear benefit of these additional links. We paid great attention to simulate systematic effects of all observation techniques as realistically as possible. For L-band these are measurement noise, tropospheric delays, phase center variation of receiver and transmitter antennas, constant and variable biases as well as multipath. For optical links we simulated colored and distance-dependent noise, offsets due to the link repeatability and offsets related to the equipment calibration quality. In addition, we added a troposphere error for the OTWL measurements. We discuss the influence on the formal orbit uncertainties and the effects of the systematic errors. Restrictions due to weather conditions are addressed as well. OTWL is synergetic with the other measurement techniques like OISL and can be used for data transfer and communication, respectively.

在本模拟研究中，我们分析了地空光双向链路 (OTWL) 对伽利略精确定轨 (POD) 的益处。OTWL 是一个基于连续波激光测距和时间传输的概念，调制信号从地面站到地面站。这些测量是对全球导航卫星系统 (GNSS) 观测的补充。我们模拟了关于 16 个伽利略传感器站的测量。在模拟研究中，我们假设整个伽利略卫星星座都配备了用于 OTWL 的终端。将 OTWL 与伽利略 L 波段一起使用，与仅使用 L 波段计算的轨道解相比，展示了将两种测距技术与系统误差的不同影响相结合的优势。双向链路允许站和卫星时钟同步。此外，我们将地面空间概念与称为光双向卫星间链路 (OISL) 的卫星对卫星对应物进行了比较。OTWL 的优点是卫星系统和固体地球之间的连接以及同步卫星时钟和地面站时钟的可能性。还模拟了结合使用所有三种观察类型的完整网络。在这些组合中估计额外的太阳辐射压力 (SRP) 参数的可能性是这些额外链接的明显好处。我们非常注意尽可能真实地模拟所有观测技术的系统效果。对于 L 波段，这些是测量噪声、对流层延迟、接收器和发射器天线的相位中心变化、恒定和可变偏差以及多径。对于光链路，我们模拟了有色噪声和与距离相关的噪声、链路可重复性引起的偏移以及与设备校准质量相关的偏移。此外，我们为 OTWL 测量添加了对流层误差。我们讨论了对形式轨道不确定性的影响和系统误差的影响。由于天气条件造成的限制也得到了解决。OTWL 与 OISL 等其他测量技术协同工作，可分别用于数据传输和通信。由于天气条件造成的限制也得到了解决。OTWL 与 OISL 等其他测量技术协同工作，可分别用于数据传输和通信。由于天气条件造成的限制也得到了解决。OTWL 与 OISL 等其他测量技术协同工作，可分别用于数据传输和通信。