Reducing the number of unknowns in the FFT employed BOR EM scattering problems

An estimate has been made of number of modes, which need to be considered for accurate results in the Body of Revolution (BOR) electromagnetic (EM) scattering problem employing Fast Fourier Transform (FFT). This way, we don't have to solve unnecessarily BOR EM scattering problems for large number of modes consuming a large CPU memory and time. We need to solve the BOR EM scattering problem up to a specific number of modes thereby increasing the efficiency of the BOR-FFT program due to the reduced number of unknowns without compromising the accuracy.