Monitoring the time-variable geopotential identifies the mass redistribution across the Earth and reveals, e.g., climate change and availability of water resources. The features of interest are characterized by spatial and temporal scales accessible only through space missions. Among the most important gravity missions are GRACE (2002–2017), its successor GRACE-FO (since 2018), and GOCE (2009–2013), which all sense the Earth’s gravity field via the geopotential derivatives. We investigate the geopotential estimation through frequency comparisons between orbiting clocks by means of the Doppler-canceling technique, describing the clocks’ behavior in the Earth’s gravitational field via Einstein’s general relativity. The novelty of this approach lies in measuring gravity by sensing the geopotential itself. The proof of principle for the measurement is achieved through an innovative mission scenario: for the first time, the observations are collected by a probing clock in LEO. We show gravity solutions obtained by simulating an estimation problem via our proposed architecture. The results suggest that we can conceivably retrieve the geopotential coefficients with accuracy comparable to the GRACE measurement concept by employing clocks with stabilities of order \({10}^{-18}\). Presently, terrestrial clocks can routinely attain fractional frequency stabilities of \({10}^{-18}\), whereas spaceborne clocks are still at the \({10}^{-15}\) level. While our findings are promising, further analysis is needed to obtain more realistic indications on the feasibility of an actual mission, whose realization will be possible when clock technology reaches the required performance. The goal is for the technique investigated in this study to become a future staple for gravity field estimation.

监测随时间变化的地势可以识别地球上的质量重新分配，并揭示气候变化和水资源可用性等情况。感兴趣的特征的特点是空间和时间尺度只能通过太空任务访问。最重要的重力任务包括GRACE（2002-2017）、其后继者GRACE-FO（自2018年起）和GOCE（2009-2013），它们都通过位势导数来感知地球的重力场。我们利用多普勒抵消技术通过轨道时钟之间的频率比较来研究地势估计，并通过爱因斯坦的广义相对论描述时钟在地球引力场中的行为。这种方法的新颖之处在于通过感测地势本身来测量重力。测量原理的证明是通过创新的任务场景实现的：首次由近地轨道的探测时钟收集观测结果。我们展示了通过我们提出的架构模拟估计问题获得的重力解决方案。结果表明，通过使用具有 \({10}^{-18}\) 阶稳定性的时钟，我们可以想象地以与 GRACE 测量概念相当的精度检索位势系数。目前，地面时钟通常可以达到\({10}^{-18}\)的分数频率稳定性，而星载时钟仍处于\({10}^{-15}\)水平。虽然我们的研究结果很有希望，但还需要进一步分析，以获得有关实际任务可行性的更现实的指示，当时钟技术达到所需的性能时，其实现就有可能。 本研究的目标是使该技术成为未来重力场估计的主要技术。