Earth System Mass Transport Mission (e.motion): A Concept for Future Earth Gravity Field Measurements from Space

In the last decade, satellite gravimetry has been revealed as a pioneering technique for mapping mass redistributions within the Earth system. This fact has allowed us to have an improved understanding of the dynamic processes that take place within and between the Earth’s various constituents. Results from the Gravity Recovery And Climate Experiment (GRACE) mission have revolutionized Earth system research and have established the necessity for future satellite gravity missions. In 2010, a comprehensive team of European and Canadian scientists and industrial partners proposed the e.motion (Earth system mass transport mission) concept to the European Space Agency. The proposal is based on two tandem satellites in a pendulum orbit configuration at an altitude of about 370 km, carrying a laser interferometer inter-satellite ranging instrument and improved accelerometers. In this paper, we review and discuss a wide range of mass signals related to the global water cycle and to solid Earth deformations that were outlined in the e.motion proposal. The technological and mission challenges that need to be addressed in order to detect these signals are emphasized within the context of the scientific return. This analysis presents a broad perspective on the value and need for future satellite gravimetry missions.