ESA and NASA are currently intensifying their long-term efforts on a collaborative implementation of a next generation mass change and gravity monitoring satellite mission. The NASA-ESA Joint Programme Planning Group initiated an activity to investigate ideas for observing mass transport from space in the future. An Interagency Gravity Science Working Group (IGSWG) with experts from US and ESA member states was established in 2013, which delivered a report in 2016 "Towards a sustained observing system for mass transport to understand global change and to benefit society". The global user community document of the International Union of Geodesy and Geophysics (IUGG) served as a basis for the report. In the meantime, the most recent Decadal Survey was released in 2017 in the US and identified Mass Change (MC) as one of the five Designated Observables (DO) recommended for implementation. The MCDO study was issued by NASA at the end of 2018 to answer to Decadal Survey science questions, whilst ESA completed Phase 0 of Next Generation Gravity Mission (NGGM). In order to bring both activities together ESA and NASA established a science expert group with 5 US and 5 ESA member state scientists to consolidate science questions and user needs for the Mass-change And Geosciences International Constellation (MAGIC) incorporating elements from NGGM and MCDO. This resulted in the Mission Requirements Document (MRD) for MAGIC which summarizes the requirements of the global scientific community (which include requirements from the IGWSG report, IUGG, MCDO, etc.) and serves as the starting point for mission design in both agencies. The target and threshold user requirements consolidated by science expert group are provided in form of spatio-temporal resolution and accuracy for the individual disciplines of hydrology, cryosphere, oceanography, solid Earth and climate. The evolution of the MRD is currently supported by the Joint Mass Change Mission Expert Group (JMCMEG), which is a broader international group of experts in related Earth science disciplines. ESA and NASA are at the moment running a Phase A and pre-Phase A accordingly which are coordinated and aim at designing a constellation which provides on one hand enhanced continuity towards a climate series and on the other hand a better space-time resolution with homogeneous quality to serve the community needs for science and applications. This presentation will focus on the MAGIC mission status and on the scientific roadmap to achieve the mission objectives.

NASA and ESA have agreed to cooperate towards preparing a Mission Requirements Document (MRD) and defining support science study activities for a Mass-change And Geosciences International Constellation (MAGIC). Such a constellation is essential for understanding global change. Requirements sources are the ESA/NASA International Gravity Science Working Group (IGSWG) Report (1), the 2017 National Academies of Science Earth Science Decadal Survey (2) and an IUGG document (3), which include community user needs in view of potential future contributions to EC Copernicus services.

The evolution of the MRD will be supported by the Joint Mass Change Mission Expert Group (JMCMEG). The JMCMEG members cover expertise in Earth Science study disciplines. In addition, the group brings expertise from missions like GRACE, GRACE-FO and GOCE, and past or current preparatory studies for future concepts. The group’s expertise is complementary (hydrology, cryosphere, oceanography, solid earth, climate change, neutral atmosphere) so that it can consider a wide breadth of user community objectives, regarding science and applications, as well as more technical aspects of mission design trade-offs. JMCMEG activities will be conducted in the context of the MAGIC concept and supporting scientific study and validation activities. The JMCMEG will also provide support in strengthening the link to the international user communities and their representing Agencies, and support communications on the concept by means of scientific publications, presentations, and the World Wide Web.

This presentation will focus on the latest definition of MAGIC mission requirements and user needs.

(1) Towards a sustained observing system for mass transport to understand global change and to benefit society, NASA/ESA Interagency Gravity Science Working Group (IGSWG), 12 May 2016, Document number: TUD-IGSWG-2016-01

(2) Thriving on our changing planet - Decadal Survey for Earth Science and Applications from Space, doi: 10.17226/24938, The National Academies of Sciences, Engineering, Medicine, 2017

(3) Pail R. et al., Observing Mass Transport to Understand Global Change and to Benefit Society: Science and User Needs – An international multi-disciplinary initiative for IUGG, Deutsche Geodätische Kommission der Bayerischen Akademie der Wissenschaften, Heft 320, ISBN 978-3-7696-8599-2, München, 2015

NASA and ESA have assembled a Joint Mass Change Mission Expert Group (JMCMEG) to support and carry out science study activities for a joint NASA/ESA Mass-change And Geosciences International Constellation (MAGIC). A part of the JMCMEG is responsible for assessment of the gravity field recovery in diverse mass change mission architectures. The results from these studies support the evolution of a MAGIC Mission Requirements Document (MRD).

The performance of various MAGIC mission concepts is evaluated in the frame of full-fledged numerical closed-loop simulations, which try to mimic the real world conditions as realistically as possible. All relevant error sources are taken into account and projected to the finally achievable gravity field performance. In such a numerical simulation environment, the key parameters of the constellation, such as orbit altitude, inter-satellite distance, ground track pattern, and accuracy of the key instruments, are evaluated. The resulting performances are matched against the science and user needs, and science values of the different mission concepts are derived. These results inform NASA and ESA of the expected science and applications return of a variety of mission architectures, so this can be considered alongside other key mission implementation variables, such as cost, risk, schedule, and technology readiness.

The presentation summarizes the main simulation results of the contributing institutions, their inter-comparison and assessment as well as the main conclusions derived from these extensive numerical experiments.

The GRACE and GFO missions have revolutionised our understanding of mass movement at and below the surface of the Earth but the spatial and temporal resolution and instrument sensitivity limits our ability to resolve fundamental processes. In this presentation we focus on the advances and capabilities that the proposed Mass change And Geosciences International Constellation (MAGIC) mission will deliver for cryosphere and solid Earth applications and will also consider the potential it will have for studying the neutral atmosphere.

The time-varying gravity solutions from the current GRACE and GRACE-FO missions have an effective spatial resolution of ~300-400 km applying regularization or post-processing filters, which is larger than the scale of any glacier or ice cap and larger than most catchments on the Greenland Ice Sheet. Even over Antarctica, the limited spatial resolution is a major limitation for regions such as the Antarctic Peninsula. Tectonic processes, such as earthquakes, volcanic activity and even viscous mantle flow can take place on scales smaller than can be resolved currently. The target resolution and accuracy for MAGIC over ice is 170 km at 2.6 mm/yr EWH over the long term and 250 km at 5.5 mm EWH at monthly resolution plus lower accuracy daily to weekly capabilities. We consider here what this means for understanding and observing ice mass exchange with the oceans and improving our ability to measure the manometric contribution to sea level rise. Based on similar targets, we also explore the improvements this offers for monitoring different types of solid Earth processes such as the transient signals of tsunamis in the open ocean as well as other geohazard processes such as volcanic eruptions to slower steady motions. This includes the monitoring of the whole seismic cycle, from inter-seismic to post-seismic phases and the slow reshaping of the Earth’s surface by active tectonics. We discuss potential improvements at larger spatial scales, in order to advance knowledge of deep interior properties and dynamics for instance from tidal forcing. We finally consider what contributions MAGIC will be able to make to observations of thermosphere neutral density and related atmospheric parameters.

Satellite gravimetry observations as provided by the GRACE and GRACE-FO missions have revolutionized our understanding of the global water cycle under climate change. Among several other application fields, major achievements of the missions can be related to the first-time quantification of groundwater storage change from space, the disentangling of different contributors to sea level rise, a global analysis of flood and drought events, the analysis of the Earth’s energy imbalance, and the validation of Earth system and climate models.

Despite the groundbreaking success of ongoing satellite gravity observations, limitations of the current missions in terms of accuracy, spatial/temporal resolution, latency, and the length of the time series are still hampering an even more extended range of geophysical applications and a comprehensive operational integration into scientific services as those provided by the Copernicus program of the European Commission. To overcome these limitations NASA and ESA are cooperating towards a joint mission Mass-change And Geosciences International Constellation (MAGIC). The development of the respective Mission Requirements Document (MRD) is currently being supported by the Joint Mass Change Mission Expert Group (JMCMEG), covering expertise in all relevant application fields of MAGIC.

Based on the ongoing work of the JMCMEG, this presentation will focus on the MAGIC mission science applications related to the fields of hydrology, oceanography, and climate science. We will showcase important recent developments achieved with currently available satellite gravity data in these research fields, point out challenges involved with their analysis, and discuss expected scientific benefits of the MAGIC constellation.