## 8 Conclusions  
ESA's MAGIC/NGGM is a mission under definition to improve our knowledge and monitoring of geophysical phenomena revealed by Earth's gravity field, in the wake of the GOCE, GRACE and GRACE-FO missions. More than 10 years of extensive preparation activities have advanced the maturity of the system, attitude and drag control, proportional thrusters, laser optics and electronics to a sufficient technological readiness level to propose the mission for adoption in 2022 and launch in 2028. Concurrently, the USA's \"Decadal Strategy for Earth Observation from Space\" for 2017-2027 identifies mass change observations derived from the measurement of the time-variable gravity field, first obtained by GRACE and then continued by GRACE-FO, as one of the five priority observables and encourages NASA to seek international partnership to implement the mission. In this context, an NGGM mission in cooperation with NASA as part of the MAGIC constellation is considered as the most mature candidate for an ESA Mission of Opportunity in the current decade. A constellation of two satellite pairs orbiting in the Bender constellation is recommended, and the proposed orbits guarantee an unprecedented high temporal and spatial resolution of less than one week. This fits with the mission objectives to provide a valuable contribution to emergency and near-real-time (i.e., daily to subweekly) applications. Beyond such a goal, the retrieved solutions will benefit from a much higher spatial resolution as well, e.g., by resolving much smaller river basins than GRACE and GRACE-FO. The excellent ground track homogeneity at the established time scales will also provide unprecedented regular data quality to support services and to help to answer open and unsolved scientific and societal questions related to continental water storage, hydrology, cryosphere, oceans, solid Earth, atmosphere and climate change. Conceptualization, L.M. ; methodology, L.M., C.S. and G.M. ; software, C.S. and G.M. ; validation, L.M. and R.H.; resources, R.H.; data curation, G.M. ; writing--original draft preparation, L.M., C.S. and G.M. ; writing--review and editing, L.M., C.S. and R.H.; supervision, P.S. ; funding acquisition, P.S. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. This work is based on ESA internal work and on scientific, system and technology studies performed since 2016--under ESA contracts--by several European companies and universities. The authors would like to thank, among others, the University of Stuttgart's Institute of Geodesy, Thales Alenia Space (Italy), SpaceTech GmbH, Deimos Space and the Italian National Metrology Institute (INRIM). The authors declare no conflict of interest. * _[PERSON] et al. (2003)_ [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON] The gravity recovery and climate experiment: Mission overview and early results. _Geophys. Res. Lett._**2003**, _31_, L09607. [CrossRef]
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