Waveguide-based Dielectric and Magnetic Property Measurement

This NASA invention utilizes a simple waveguide-based measurement system to determine the complex dielectric permittivity and magnetic permeability of arbitrary-shaped planetary rock samples. The system operates at L-band frequencies (~1 GHz) and can be extended to P- and S-bands for broader applications. The approach involves placing an arbitrarily-shaped sample inside an open-ended waveguide excited by a coaxial probe, measuring the scattering parameters, and extracting dielectric and magnetic properties through computational modeling and optimization techniques. A key aspect of this system is its ability to handle non-uniform and irregularly shaped rock samples, enabling the measurement of real-world planetary materials without requiring extensive sample preparation. The methodology includes calibration in an anechoic chamber, computational modeling, and iterative refinement of measured vs. simulated scattering parameters to extract the material properties. Future advancements will involve expanding measurements to different frequency bands, refining computational models using artificial intelligence, and automatically rotating samples within the waveguide to obtain multiple directional measurements (enhancing precision while reducing test time). This NASA innovation has been successfully applied to two Martian meteorite samples, yielding values of dielectric permittivity and permeability relevant for Mars radar applications. The system will further be leveraged to build an expansive database of the dielectric properties of planetary soils and rocks to improve radar-based mapping (e.g., subsurface mapping) missions. The invention could also be applied for the non-destructive screening of a variety of samples using radio waves, including biological samples for medical purposes, additive manufacturing feedstock or finished parts, and mining-related rock samples to test for impurities or resources of interest. This NASA invention is at technology readiness level (TRL) 5 (component and/or breadboard validation in relevant environment) and is available for patent licensing. Understanding the composition of planetary surfaces is crucial for advancing space exploration and preparing for future human missions to the Moon and Mars. NASA’s proposed International Mars Ice Mapping (I-MIM) mission aims to use Synthetic Aperture Radar (SAR) to identify near-surface ice deposits on Mars, which could serve as a vital resource for future explorers. To support this effort, scientists must first determine how radar signals interact with the diverse materials found on these planetary bodies, such as rock, regolith, and buried ice. An understanding of these interactions is critical to designing specialized SARs for such missions, as well as to determining their detection capabilities in specific environments. Traditional methods of analyzing such materials have provided valuable insights, but they often lack the ability to assess the 3-D electromagnetic (EM) properties of rock and soil, which are critical for improving radar-based detection capabilities. Furthermore, existing techniques require regularly shaped samples (e.g., rectangles). Martian and other planetary rock samples brought back to Earth are precious and cannot be altered, eliminating these techniques as an option. Recognizing this challenge, a team of engineers and scientists at NASA’s Goddard Space Flight Center (GSFC) have developed an advanced laboratory-based system for measuring the dielectric and magnetic properties of arbitrarily shaped samples with high accuracy.