An estimate of the effects of air environment on resonant frequencies and damping factors of solar arrays of spacecraft that are recorded during ground modal tests

The validity of loads acting on structural elements of spacecraft solar arrays in the course of their on-orbit operation depends on the accuracy of determining their dynamic properties. Dynamic properties of solar arrays determined by calculations using finite element models (due to insufficient knowledge of some of the stiffness parameters of their structure) require experimental validation, which is perfomed by running ground modal tests. Since solar arrays have a large surface area while their structure has low mass, the values of their resonant frequencies and damping factors are affected by the air environment. The paper provides the calculation procedure and a quantitative estimate of the effect the surrounding air has on the resonant frequencies and damping factors determined in the course of ground modal tests on one of the solar arrays developed at RSC Energia.