Abstract
Mechanically moving components onboard spacecraft generate disturbances and often deteriorate spacecraft attitude stability and payload pointing performance. Therefore, the effect of internal disturbances must be carefully evaluated and controlled within an acceptable level through the design and the test before launch of the spacecraft. However, the stiffness or the flexibility of the supporting structure and/or the internal structure of moving components sometimes gives complexity to the evaluation and verification of the effect. In particular, if the spacecraft performance such as payload pointing stability is predicted based on the the disturbance transfer function obtained either analytically or by measurement, in conjunction with the estimated level of disturbances, the stiffness effect may cause a severe problem on the reliability of the prediction. This situation is typically encountered during the early design and test phase, because neither the flight model of spacecraft nor the actual disturbing components exist at this phase so that the prediction based on the disturbance transfer function is the only viable way of prediction. In this paper, the problem is outlined and recommended practices are briefly described.
