## 3 Updating Method for FE Model of Antenna  
The BUS is a typical three-dimensional truss system that directly supports the primary reflector surface of the antenna. The truss and related supports are composed of members mainly subjected to axial force in the truss structure. Based on the linear elastic deformation framework in Section 2, it can be seen that in the antenna FE model, the main material property parameter that affects the BUS deformation is the modulus of elasticity of the member. In order to solve the error caused by the difference in deformation between the antenna BUS and the FE model BUS, we evaluate the deformation of the antenna's primary surface using the FE method. We have designed a method for updating the large-aperture reflector antenna FE model, as illustrated in Figure 3. The method uses the Root Mean Square (RMS) of the primary reflector surface node's half-path length error to represent the antenna's primary reflector surface's deformation [20]. The antenna's original FE model is updated by optimizing the rod's elastic modulus in the BUS.  
We analyzed the effect of the BUS deformation on the primary reflector surface deformation in terms of the antenna original FE model BUS upper chord node displacement. The whole flow consists of the following two main parts:  
1. Parameter sensitivity analysis 1. The antenna's original FE model is established based on the design information. 2. The model input parameters are set to the elastic modulus of \(d\) different BUS bars. The output response is set as the RMS of the displacement of the BUS upper chord nodes. 3. The Latin hypercube sampling (LHS) experimental design method [21] is utilized to obtain \(p\) sets of random input parameter samples. Then, the FE model is employed to acquire \(p\) output responses. 4. The RBF surrogate model is obtained by using \(p\) sets of input and output responses, and it is used to replace the FE model for the parameter sensitivity analysis. 5. The sensitivity of these \(d\) input parameters to the output response is calculated using the RBF model and combined with the Sobol method to obtain \(d^{\prime}\) sensitive parameters. 2. Parameter optimization 1. The original FE model input parameters are set to the \(d^{\prime}\) sensitivity parameters obtained by sensitivity analysis, and the output response is the RMS of the relative  
Figure 3: The flow of FE model updating.  
displacement error between the antenna's nodes and the original FE model's corresponding nodes. 2. The Latin hypercube sampling experimental design method is utilized to obtain \(q\) sets of random input parameter samples. Then, the FE model is employed to acquire \(q\) output responses. 3. The RBF surrogate model is obtained by using \(q\) sets of input and output responses, and it is used to replace the FE model for the parameter optimization. 4. The \(d^{\prime}\) parameters were optimized using an agent model and combined with a genetic algorithm. 5. The optimized parameters are used in place of the original parameters in the FE model to calculate the RMS of the BUS upper chord nodes' half-path length errors, which is compared with the RMS of the antenna primary reflector surface nodes' half-path length errors to test the model updating effect [22].