ESA GNC Conference Papers Repository
Model Description and Simulated Mission Performance of the Next Generation Gravity Mission E2E Simulator
In the years to come, Earth observation via remote sensing will enter into a new era, characterized by a growing number of advanced and sophisticated satellite missions. They will provide scientists with an unprecedented capacity to observe and monitor the Earths mass transport and its inner physical phenomena. Following the two successful missions GOCE and GRACE, gravity missions have acquired a great importance within the ESA Earth Observation Programme directorate. Indeed, a Next Generation Gravity Mission (NGGM) concept for measuring the variability of the Earths gravity field is proposed, whose objectives will be very challenging in terms of spatial and temporal resolution. The baseline measurement technique will be a laser interferometry system via low-low satellite-to-satellite tracking. This space segment will be based on two drag-free satellites, flying in loose formation in LEO, equipped with a very accurate accelerometer-based sensing system. The mission concepts and architectures have been implemented in an End-to-End (E2E) multi-missions simulation tool, an evolving simulator platform for the NGGM concept. The paper presents a description of the main subsystem models of the software simulating a typical NGGM mission scenario, giving particular attention to the mathematical expression of the relevant embedded models. Considered the specific thorny points of the mission (the 10 years duration, above all), particular attention is given to the environmental models, the ion thrusters assembly and the drag-free, attitude and orbit control algorithms. In addition, for a complete validation of the software, series of sensitivity tests have been carried out, mostly involving the gradiometer, the optical metrology and ion thrusters models. These tests have pointed out the different levels of compliance of the simulated NGGM scenarios against the preliminary mission requirements. Therefore, in the last part of the paper, a set of guidelines for the enhancement of the control algorithms will be provided, in order to allow optimal fitting of the E2E simulator with the latest mission concepts of NGGM.