NEXT GENERATION GRAVITY MISSION (NGGM)

Global climate change and related phenomena such as sea level rise, floods, droughts, Earth energy imbalance, have a widespread impact on society and generate alterations of gravity signals. Understanding and quantification of the related mass changes, their magnitude and impact is fundamental to mitigate climate-change challenges ahead.

ESA and NASA have developed a cooperation for a space mission to monitor Earth’s mass change based on gravity measurements. The Mass-change and Geosciences International Constellation (MAGIC) is a collaboration between ESA and NASA that includes a first pair of gravity satellites in near-polar orbit called GRACE Continuity (GRACE-C). This will be augmented by a second satellite pair in a complementary inclined orbit led by ESA called the Next Generation Gravity Mission “NGGM”.  

NGGM is ESA’s Mission of Opportunity within the FutureEO programme. The aim of the NGGM mission is to extend and improve time series of satellite gravity missions by providing enhanced spatial and temporal resolution time-varying gravity field measurements with reduced uncertainty and latency to address the international user needs as expressed by IUGG and GCOS and to demonstrate operational capabilities relevant for Copernicus.  The overarching objective of the NGGM is to measure and monitor Earth’s time varying gravity field and its trends at sub-weekly, monthly to seasonal and long-term timescales in regions up to 70^ο North/South. NGGM’s primary objectives on hydrology include the monitoring of GCOS Terrestrial Water Storage (TWS) and Groundwater Storage (GWS) GCOS Essential Climate Variable (ECV), to contribute to the operational monitor of droughts and floods, to support water management services and to contribute to the closure of water budget at sub-basin scales. On glaciology, NGGM aims to improve the estimates of the ice mass balance of Greenland, Antarctica (up to 70^ο North/South) and mountain glaciers and quantify their contribution to the global mean sea-level change. It also aims to improve our understanding of the dynamics of potentially unstable glacier systems. On oceanography, NGGM’s primary objective is to measure changes in the Antarctic Circumpolar Current (ACC) and the Atlantic Meridional Overturning Circulation (AMOC). On Solid Earth applications NGGM aims to improve our understanding of crust and mantle structure, as well as deformation processes, during all phases of the seismic cycle and to support geohazard monitoring. For climate applications, NGGM aims to provide improved estimates of global ocean heat uptake, ocean heat content changes and Earth’s energy imbalance, and to improve sea level budget closure at both global and regional scales. For geodesy applications, NGGM aims to contribute to the static and time-varying realisation of the International Height Reference Frame (IHRF).

Each NGGM satellite will embark a payload suite including an instrument for nanometre-precise intersatellite tracking, ultra-sensitive next generation accelerometers, and a precise orbit determination package. NGGM will be launched in an inclined controlled orbit that adds significantly improved East-West sensitivity in the gravity measurements and will improve the error isotropy of the recovered gravity field. NGGM’s orbit will be controlled via a hybrid propulsion system including electric propulsion thrusters for orbit maintenance and drag compensation and linear cold gas thrusters for fine attitude control and drag compensation. NGGM’s controlled orbit will enable consistent ground-track coverage, ensuring uniform product quality—essential for NGGM and MAGIC pre-operational capabilities. To support time-critical early warning applications, NGGM will deliver both fast-track (i.e. short-latency) products and final (i.e. full quality) products.