Enhanced data-based dynamic characterization of PLATO satellite through qualification testing

The dynamic qualification of the ESA-PLATO (PLAnetary Transits and Oscillations of stars) Proto-Flight Model involved sine-sweep testing over multiple excitation levels and generated a large experimental dataset from several hundred measurement channels. This work presents a data-driven methodology that combines conventional frequency-response functions with synchronized time-domain measurements to identify and characterize amplitude-dependent dynamic behavior. A Similarity Index is introduced to compare transmissibility functions acquired at different excitation levels and to automatically rank sensors and spacecraft modules according to their response evolution. The identified critical regions are subsequently investigated through time-frequency analysis and Fourier decomposition of the measured responses. The proposed workflow reveals resonance shifts, jump phenomena and significant changes in the harmonic content of selected structural regions. The results demonstrate that synchronized time-domain measurements provide valuable complementary information to conventional frequency-domain processing, enabling a more comprehensive interpretation of spacecraft qualification tests without requiring a priori numerical models.