Complex-structured 3D-printed wireframes as asteroid analogues for tomographic microwave radar measurements

This study introduces a fused filament fabrication (FFF) process for manufacturing complex-structured asteroid analogue objects to be applied in tomographic microwave radar measurements and inversion studies. We describe an approach to control the volume fraction of the plastic and, thereby, the effective relative permittivity within a tetrahedral wireframe which serves as metamaterial representing the actual asteroid composition. To determine the effective permittivity of the plastic–air mixture, we use an exponential model. In this study, two analogue objects based on the shape of the asteroids 1998 KY26 and (25143) Itokawa were 3D-printed in a scale suitable for microwave laboratory measurements using ABS filament with a controlled constant relative electric permittivity. The results obtained suggest that the permittivity of solid and powdery asteroid minerals can be modelled with the proposed technique and, in particular, that the numerical structural permittivity models of the earlier numerical studies can be approximated by 3D-printed analogues.