ESA GNC Conference Papers Repository

The long-term stability of reaction wheel performance has become a key factor for the success of many space missions. Over the last years, various investigations on particular features of reaction wheels for ESA spacecraft have been pursued at the European Space Research and Technology Centre (ESTEC) in cooperation with the European Space Operations Centre (ESOC) and industrial partners.Such investigations are often based on three main elements: (1) Modelling and simulation of the relevant operating principles and underlying physical effects (2) Hardware test activities on ground, with special attention to the post-processing of the test data and the correlation of simulation and test results (3) Analysis of in-flight telemetry data for routine monitoring of the equipment (and with special effort in the frame of anomalous behaviour) The paper will elaborate on above main elements via several typical examples: Reaction wheel performance modelling and simulation has considerably advanced on the basis of modern software tools and a more detailed correlation of simulation results with test data at component, subassembly and equipment level. In this context, the torque behaviour of ball bearing systems for flywheel suspension and electro-magnetic effects associated with reaction wheel drive motors will be specifically addressed. For the INTEGRAL spacecraft of ESA, a dedicated reaction wheel test as currently being performed in the ESTEC laboratories. As primary objective, more confidence shall be built up regarding the tolerance of reaction wheels against long-term operation at low speed and a high number of speed reversals. The hardware test activities also comprise micro-disturbance/micro-vibration characterisation on a regular basis, in the closer sense of non-intrusive health and condition monitoring. On the ROSETTA and XMM-NEWTON spacecraft, the stability and evolution of the reaction wheels' friction torque has been monitored over many years. Because of some irregularities of the friction torque, several attempts of bearing relubrication were conducted. Also in this conjunction, the paper will emphasise some key points for health and condition monitoring in flight as well as potential interventions on reaction wheel operation, aiming at performance recovery & stabilisation.