论文标题
验证卫星重力任务的光钟网络的潜在和科学要求
Potential and scientific requirements of optical clock networks for validating satellite gravity missions
论文作者
论文摘要
宽限期和宽限期的任务提供了对水周期大规模变化的前所未有的量化。但是，对于如何将这些任务的数据集引用到地面真相仍然是一个空旷的问题。同时，固定的光学时钟显示出一个小时以上的平均值低于$ 10^{-18} $的分数不稳定性，并在精确性和准确性，正常运行时间和可运输性方面继续改善。时钟的频率受重力红移的影响，因此取决于局部地势。 $ 10^{ - 18} $的相对频率更改对应于大约$ 1 $ cm的地质高度变化。在这里，我们建议可以进一步利用这种效果，以通过分布在地球表面的时钟网络来传感大规模的时间地势变化。实际上，已经提出了一些项目，以通过光纤链接来创建整个欧洲连接的光学时钟的集合。我们的假设是，具有共处的GNS接收器的时钟网络分布在欧洲 - 为此，物理基础设施已经部分到位 - 使我们能够确定地球重力场的时间变化在天数及以后的时间尺度上，并为验证诸如Grace -Fo或Future Gract Gractity任务等卫星任务提供了新的手段。在这里，我们通过模拟在未来网络中的时钟比较可以观察到欧洲的冰，水文和气氛变化如何遵循计量学界当前的设计概念。我们假定时钟和GNSS不确定性的情况不同，并且发现即使在保守的假设下 - 每日测量的时钟误差为$ 10^{ - 18} $，垂直高度控制误差为$ 1.4 $ mm-每日时间尺度上的水文信号，大气信号和大气信号下的每周时间尺度下降到每周的时间表。
The GRACE and GRACE-FO missions have provided an unprecedented quantification of large-scale changes in the water cycle. However, it is still an open problem of how these missions' data sets can be referenced to a ground truth. Meanwhile, stationary optical clocks show fractional instabilities below $10^{-18}$ when averaged over an hour, and continue to be improved in terms of precision and accuracy, uptime, and transportability. The frequency of a clock is affected by the gravitational redshift, and thus depends on the local geopotential; a relative frequency change of $10^{-18}$ corresponds to a geoid height change of about $1$ cm. Here we suggest that this effect could be further exploited for sensing large-scale temporal geopotential changes via a network of clocks distributed at the Earth's surface. In fact, several projects have already proposed to create an ensemble of optical clocks connected across Europe via optical fibre links. Our hypothesis is that a clock network with collocated GNSS receivers spread over Europe - for which the physical infrastructure is already partly in place - would enable us to determine temporal variations of the Earth's gravity field at time scales of days and beyond, and thus provide a new means for validating satellite missions such as GRACE-FO or a future gravity mission. Here, we show through simulations how ice, hydrology and atmosphere variations over Europe could be observed with clock comparisons in a future network that follows current design concepts in the metrology community. We assume different scenarios for clock and GNSS uncertainties and find that even under conservative assumptions - a clock error of $10^{-18}$ and vertical height control error of $1.4$ mm for daily measurements - hydrological signals at the annual time scale and atmospheric signals down to the weekly time scale could be observed.
