ESA GNC Conference Papers Repository

This paper concerns the preparatory studies of a future ESA Earth Observation mission ultimately devoted to improve our understanding of the Earth’s mass transport phenomena, the temporal variations of the gravity field, at different temporal and spatial scales, being caused by ice sheet and glaciers melting trends, continental water cycles, ocean masses dynamics and solid-earth deformations. The “Assessment of a Next Generation Gravity Mission for Monitoring the Variations of the Earth’s Gravity” activities (concisely: NGGM) include two parallel studies, one led by Astrium GmbH (Friedrichshafen, Germany) and another one by Thales Alenia Space (Turin, Italy). Both consortia involve European universities and academic institutions for scientific support and requirement assessments, in addition to experts in mission analysis and measurement technologies. Several mission concepts have been studied with well-defined science requirements and accurate sub-system designs: in addition to the drivers due to tight propulsion requirements and accelerometer calibration issues (since calibration represents a dominant error source at large scales), the technical constraints on power and fuel may dictate the choice of orbit. Thus, for each considered constellation type, the different interactions between drag-free and “loose” formation control have been analysed, together with the design of the relative attitude control, necessary to ensure the laser link for inter-satellite distance measurement all along the mission phases. Following the completion of the studies, the latest results concerning the proposed satellite architectures, laser metrology, attitude and orbit control system and formation flying control concepts are presented in the paper, including the ESA recommendations and the technology way-ahead for a successful preparation of this future gravity mission.