Full wavefield simulation versus measurement of microwave scattering by a complex 3D-printed asteroid analogue

Context. The small bodies of the Solar System, and especially their internal structures, are still not well-known. Studies of the interior of comets and asteroids could provide important information about their formation and also about the early Solar System. Aims. In this paper, we investigate the possibility of obtaining information about their inner structure from their response to an incident electromagnetic field in preparation for future space radar missions. Our focus is on experimental measurements concerning two analog models with the shape of 25143 Itokawa, a small rubble pile asteroid monitored by the Japanese space agency's (JAXA) Hayabusa mission in 2005. Methods. The analog models prepared for this study are based on the a priori knowledge of asteroid interiors of the time. The experimental data were obtained by performing microwave-range laboratory measurements. Two advanced in-house, full-wave modelling packages-one performing the calculations in the frequency domain and the other one in the time domain-were applied to calculate the wave interaction within the analog models. Results. The electric fields calculated via both the frequency and time domain approach are found to match the measurements appropriately. Conclusions. The present comparisons between the calculated results and laboratory measurements suggest that a high-enough correspondence between the measurement and numerical simulation can be achieved for the most significant part of the scattered signal, such that the inner structure of the analog can be observed based on these fields. Full-wave modeling that predicts direct and higher order scattering effects has been proven essential for this application.