Full-wave and multi-GTD analysis of the ice cloud imager for MetOp-SG

We report an RF study at 50 GHz of the Ice Cloud Imager, consisting of a parabolic reflector inside a semi-closed sun shield, as obtained with full-wave method of moments (MoM) and the asymptotic high-frequency multi-geometrical theory of diffraction (Multi-GTD) method. The Multi-GTD results accurately reproduce details of the main beam and sidelobes originating from focusing, but fail to predict other parts of the pattern that are due to a large number of scattering events inside the semi-closed sun shield. MoM results at the half and double frequency (25 and 100 GHz) show that the parts of the pattern that are not well described by Multi-GTD, but still within the dynamic MoM range, remain at the same overall level as the frequency is varied. Thus, when analyzing at higher frequencies of interest (≥ 183 GHz), a complementary MoM and Multi-GTD approach can be adopted to predict the radiation pattern.