Investigations concerning the effectiveness of the spacecraft finite element model correlation and update process

In order to examine the dynamic response of spacecraft during launch, Coupled Loads Analyses (CLAs), which couple a Finite Element Model (FEM) of the spacecraft with a model of the launch vehicle, are performed to simulate critical flight events. For the CLA results to be trusted, it is necessary to first develop a high level of confidence in the spacecraft FEM. This confidence is achieved by conducting appropriate test-FEM correlation and update activities making use of data gathered during vibration testing of the physical hardware. One major point of concern is the containment of the correlation and update effort in terms of mode count/modal domain. As such, this work is concerned with the assessment of the effectiveness of various target mode selection criteria. Findings are presented for initial investigations conducted using FEM data for a large, unique, scientific spacecraft developed by the European Space Agency (ESA). The work presented herein is the initial stage, and a larger study would be required to draw conclusions on the most effective means of containing the modal domain for correlation and update activities to those natural frequencies/modes which are most likely to contribute significantly in response to flight event level loading conditions