Both GRACE and GOCE have proven to be very successful missions, providing a wealth of data which are exploited for geophysical studies such as climate changes, hydrology, sea level changes, solid Earth phenomena, with benefits for society and the whole world population. It is indispensable to continue monitoring gravity and its changes from space, so much so that a GRACE follow-on mission has been launched in 2018. In this paper, a new satellite mission concept named MOCASS is presented, which can be considered as a GOCE follow-on, based on an innovative gradiometer exploiting ultra-cold atom technology and aimed at monitoring Earth mass distribution and its variations in time. The technical aspects regarding the payload will be described, illustrating the measurement principle and the technological characteristics of a cold atom interferometer that can measure gravity gradients. The results of numerical simulations will be presented for a one-arm and a two-arm gradiometer and for different orbit configurations, showing that an improvement with respect to GOCE could be obtained in the estimate of the static gravity field over all the harmonic spectrum (with an expected error of the order of 1 mGal at degree 300 for a 5-year mission) and that estimates are promising also for the time-variable gravity field (although GRACE is still performing better at very low degrees). Finally, the progress achievable by exploiting MOCASS observations for the detection and monitoring of geophysical phenomena will be discussed: the results of simulations of key geophysical themes (such as mass changes due to hydrology, glaciers and tectonic effects) with expected gravity change-rates, time constants and corresponding wavelengths, show that an improvement is attainable and that signals invisible to past satellites could be detected by exploiting the cold atom technology.

中文翻译：

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MOCASS：使用冷原子干涉测量地球重力场的卫星任务概念

事实证明，GRACE 和 GOCE 都是非常成功的任务，提供了大量数据，可用于地球物理研究，如气候变化、水文、海平面变化、固体地球现象，对社会和全世界人口都有好处。从空间持续监测重力及其变化是必不可少的，以至于 2018 年发射了 GRACE 后续任务。 本文提出了一个名为 MOCASS 的新卫星任务概念，它可以被认为是 GOCE后续，基于利用超冷原子技术的创新梯度计，旨在监测地球质量分布及其随时间的变化。将描述有关有效载荷的技术方面，说明可测量重力梯度的冷原子干涉仪的测量原理和技术特性。将针对单臂和双臂梯度计以及不同轨道配置的数值模拟结果显示，在所有谐波谱上的静态重力场估计中可以获得相对于 GOCE 的改进（ 5 年任务的 300 度的预期误差为 1 mGal），并且该估计值对于时变重力场也是有希望的（尽管 GRACE 在非常低的度数下仍然表现更好）。最后，将讨论利用 MOCASS 观测探测和监测地球物理现象所取得的进展：