Optimal Appendage Articulation Control of BepiColombo for Efficient Thruster Operation during Mercury Orbit Insertion Phase

Abstract

BepiColombo is a joint mission between European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) for Mercury exploration. Mercury, the inner most planet of the solar system, is the most challenging planetary target for a spacecraft to reach. In order to fulfil the orbital requirements in Mercury orbit, the spacecraft must follow a precisely defined delta-V operation schedule. In particular, the Mercury Orbit Insertion manoeuvres are BepiColombo’s most time critical events. During each insertion manoeuvre, the delta-V thrusters are ideally operated with maximum thrust level. However, in order to stabilize the spacecraft attitude, some thrusters are off-modulated. This inefficient thruster operation has a serious influence on the performance of the insertion manoeuvres. One cause of the off-modulation is the lateral offset of the spacecraft centre of gravity (CoG) position. The spacecraft CoG position has uncertainties and is not fixed during the mission lifetime. However, by using the articulation control of spacecraft appendages, the CoG position can be modified and the efficiency of the delta-V operation improved.