Mass concentration (mascon) solutions have become a prominent medium for investigating time-variable gravity recovered by GRACE and GRACE Follow-On. While GRACE Level-2 spherical harmonic products require various postprocessing techniques to eliminate correlated noise, mascon formulations employ spatial regularization strategies during the estimation step to improve signal recovery. However, mascon estimation has traditionally required large computing resources and GRACE Level-1B processing capabilities. In this study, we show that a typical mascon estimation system can be reformulated to allow for the estimation of regularized mascons from Level-2 spherical harmonics. Provided that spherical harmonic solution covariances are available, the computed mascons will be mathematically equivalent to similar mascons estimated from Level-1B observations. This method is computationally efficient, better leverages GRACE spherical harmonics than past methods, and matches the performance of typical mascon solutions without locking scientists into predetermined regularization designs. We develop a proof-of-concept solution using ITSG-Grace2018 and compare results with traditional mascons from the Jet Propulsion Lab (JPL) and NASA Goddard Space Flight Center (GSFC). We then assess the effects of spherical harmonic truncation and use of regularization correlations on basin signal recovery. We find that spherical expansions to degree and order 60 provide the minimum expansion necessary to study most basins, while larger expansions help further localize signals. We also find that diagonal regularizations (i.e., regularizations that do not contain inter-mascon correlations) are adversely affected by leakage, especially across boundaries such as coastlines where signals are not highly correlated, whereas including inter-mascon correlations and regional boundaries in the regularization greatly improves signal recovery.

中文翻译：

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来自球谐函数的 GRACE Fast Mascons 和正则化设计贸易研究

质量浓度 (mascon) 溶液已成为研究由 GRACE 和 GRACE Follow-On 回收的时变重力的重要媒介。虽然 GRACE Level-2 球谐产品需要各种后处理技术来消除相关噪声，但 mascon 公式在估计步骤中采用空间正则化策略来改善信号恢复。然而，mascon 估计传统上需要大量计算资源和 GRACE Level-1B 处理能力。在这项研究中，我们表明可以重新制定典型的 mascon 估计系统，以允许从 2 级球谐函数估计正则化 mascon。如果球谐函数解协方差可用，计算的 mascons 将在数学上等同于根据 Level-1B 观测估计的类似 mascons。这种方法计算效率高，比过去的方法更好地利用了 GRACE 球谐函数，并且与典型的 mascon 解决方案的性能相匹配，而无需将科学家锁定在预定的正则化设计中。我们使用 ITSG-Grace2018 开发了一个概念验证解决方案，并将结果与​​来自喷气推进实验室 (JPL) 和 NASA Goddard 太空飞行中心 (GSFC) 的传统 mascon 进行比较。然后我们评估球谐截断和使用正则化相关性对盆地信号恢复的影响。我们发现，60 度和 60 阶的球形膨胀提供了研究大多数盆地所需的最小膨胀，而较大的膨胀有助于进一步定位信号。我们还发现对角正则化（即