In-orbit vibration testing of spacecraft structures

In-orbit modal testing can be an interesting tool for the monitoring of spacecraft structures. In these applications, it is impossible to measure or to control the excitation resulting, for instance, from an impact with a small asteroid or from the working engines. Consequently the only realistic methodology must be an outputonly modal analysis, also called Operational Modal Analysis (OMA). This paper proposes another way of doing OMA where the post-processing (i.e. the physical modal parameter extraction) is simplified and automated. The methodology uses the Blind Source Separation (BSS) techniques which attempt to recover the source signals only from their observed mixtures. In case of structural dynamic responses, the source signals and the mixing matrix are equivalent to the modal coordinates and the mode matrix, respectively. The paper describes the complete methodology including the post-processing, and its feasibility is demonstrated using a numerical application modeling a truss satellite with the FE method.