Advancements in the GRACE and GRACE-FO Gradiometer Mode

The global gravitational gradient field has not been observed since the decommission of GOCE in 2013. Based on the foundational work of Peidou and Pagiatakis (2019, https://doi.org/10.1029/2018jb016382), we advance the concept of GRACE gradiometer mode (GM) for the purpose of using GRACE, GRACE-FO and future gravity space missions as “gradiometer missions.” Certainly, the GRACE missions have never carried on board a gradiometer; it is the concept of GM that creates a fictitious gradiometer system very similar to GOCE, only the GRACE “gradiometers” have long and variable baselines, an unprecedented paradigm for space-based gravitational gradiometry that extends the bandwidth of available GOCE gradient solutions. In this contribution, we develop a new configuration for GM that views an individual satellite as the “gradiometer” by directly using Level 1A accelerometer measurements at a 10 Hz sampling rate. We apply the new method in geodynamically active regions around the globe, and we demonstrate that using GRACE-C as a “gradiometer” in the single-satellite gradiometer mode (SS-GM) produces higher-fidelity gravitational gradient estimates, clearly delineating tectonic plate boundaries and subduction zones in the Himalayas and North Africa regions, the Aleutian trench, the Java trench, and the Peru-Chile trench. Over Canada, we see the delineation of the Canadian shield, and the effect of glacial isostatic adjustment is apparent. We also observe well-known signals resembling terrestrial water storage changes in Africa, among others, demonstrating the usefulness of the GM for a wide variety of geoscience applications.