ESA GNC Conference Papers Repository

Be it in the shape of momentum or reaction wheels – spacewheels are an almost indispensable part of any present- day spacecraft that relies on stabilized attitude control. Based on advanced ball-bearing technology, these devices have proved their usefulness and reliability on satellites and interplanetary space missions over decades. Inevitably, however, their moving parts are a source of undesirable mechanical vibrations which, though 'micro'-small in absolute size, spread all over the spacecraft structure and have the potential to seriously disturb sensitive instruments. Earth imaging and extra-terrestric astronomical research are just two examples of space missions today which make more and more use of high-precision instruments. They continue to boost the need for 'quiet' platforms in space, which are largely free of vibration noise from whatever source. As for spacewheels, they turn out to be among the noisiest components aboard a spacecraft. Fighting that noise needs an understanding of its origin and behaviour first. The article gives an overview of the major sources of microvibration in spacewheels, explains their various characteristics and describes proven methods of microvibration measurement and presentation, complemented by several recent examples of microvibration test results from typical spacewheels. It then focuses on strategies to mitigate either the intensity of wheel noise itself, or at least the effects of that noise on sensitive components on board a spacecraft. To this end, appropriate procedures to be followed at the wheel manufacturer's are described, and suggestions are made for measures that could be advantageously taken in the responsibility of the spacecraft builder or operator and, finally, even on the spacecraft under way.