Simulation of On-Orbit Modal Identification.

Kurzfassung

Modularly designed large orbital systems cannot be tested as a total structure on earth. Size, zero-g design and the existing atmosphere conflict with traditional structural dynamic qualification. In order to avoid the associated problems with terrestrial testing some form of on-orbit testing is likely to be used. This paper focuses on two objectives: (1) a brief discussion of hardware concerns, particularly under space conditions and (2) the demonstration of one specific software tool for on-orbit modal testing. Results extracted with the Ibrahim Time Domain method from noisy responses of an analytical structure are presented. With an analytical structure, exact modal parameters can be used as a data base in order to illustrate the accurcy of identification. Challenges of the used problem for system identification are: a frequency bandwidth enclosing two orders of magnitude, two frequency clusters and one mode with relatively high damping. With few exceptions, all results are within predefined "assessment margins" of 2 % for frequencies and 10 % for damping and mode shapes.