Structural vibrations induced by HVI - Application to the Gaia spacecraft

Given the growing stability needed for spacecraft in operation to ensure functioning of future instruments whose sensitivity requires an important technological step, perturbations encounter in orbital conditions that used to be negligible, become today an issue. This is the case of micrometeorite impacts whose energy could induce modal response of the flexible structure and imply a dynamic response of the spacecraft which could probably be disturbing for the instrument functioning. The impact environment that could be encountered by the spacecraft is preliminary studied before the definition of test to recreate the excitation with light-gas gun. Experiments are made on samples of structure representative of the ongoing Gaia astrometric mission project. Response of the structure is recorded to be correlated to finite elements model of the sample. The excitation is then extrapolated to orbital conditions and to Gaia finite elements model. The final perturbation is compared to the specification. The main conclusion is that for daily impact event, dynamic response of the structure will not disturb Gaia functioning. Nevertheless, for a yearly impact event, the astrometric mission will largely be disturbed by the dynamic response of the structure to the impact.