The European Space Agency (ESA) is preparing a satellite mission called GENESIS to be launched in 2027 as part of the FutureNAV program. GENESIS co-locates, for the first time, all four space geodetic techniques on one satellite platform. The main objectives of the mission are the realization of the International Terrestrial Reference Frames and the mitigation of biases in geodetic measurements; however, GENESIS will remarkably contribute to the determination of the geodetic parameters. The precise GENESIS orbits will be determined through satellite-to-satellite tracking, employing two GNSS antennas to observe GPS and Galileo satellites in both nadir and zenith directions. In this research, we show results from simulations of GENESIS and Galileo-like constellations with joint orbit and clock determination. We assess the orbit quality of GENESIS based on nadir-only, zenith-only, and combined nadir–zenith GNSS observations. The results prove that GENESIS and Galileo joint orbit and clock determination substantially improves Galileo orbits, satellite clocks, and even ground-based clocks of GNSS receivers tracking Galileo satellites. Although zenith and nadir GNSS antennas favor different orbital planes in terms of the number of collected observations, the mean results for each Galileo orbital plane are improved to a similar extent. The 3D orbit error of Galileo is improved from 27 mm (Galileo-only), 23 mm (Galileo + zenith), 16 mm (Galileo + nadir), to 14 mm (Galileo + zenith + nadir GENESIS observations), i.e., almost by a factor of two in the joint GENESIS + Galileo orbit and clock solutions.

欧洲航天局 (ESA) 正在准备一项名为 GENESIS 的卫星任务，作为 FutureNAV 计划的一部分，将于 2027 年发射。 GENESIS 首次将所有四种空间大地测量技术同时部署在一个卫星平台上。该任务的主要目标是实现国际陆地参考系并减少大地测量中的偏差；然而，GENESIS 将为大地测量参数的确定做出巨大贡献。精确的GENESIS轨道将通过卫星间跟踪确定，使用两个GNSS天线在天底和天顶方向观察GPS和伽利略卫星。在这项研究中，我们展示了对 GENESIS 和类伽利略星座进行联合轨道和时钟确定的模拟结果。我们根据仅天底、天顶和天底-天顶联合 GNSS 观测来评估 GENESIS 的轨道质量。结果证明，GENESIS 和伽利略联合轨道和时钟确定极大地改善了伽利略轨道、卫星时钟，甚至跟踪伽利略卫星的 GNSS 接收器的地面时钟。尽管天顶和天底 GNSS 天线在收集观测数据的数量方面有利于不同的轨道平面，但每个伽利略轨道平面的平均结果都有类似程度的改进。伽利略的 3D 轨道误差从 27 毫米（仅伽利略）、23 毫米（伽利略 + 天顶）、16 毫米（伽利略 + 天底）改进至 14 毫米（伽利略 + 天顶 + 天底 GENESIS 观测），即几乎GENESIS + 伽利略轨道和时钟联合解决方案中的两倍。