Influence of temperature and frequency on microwave dielectric properties of lunar regolith simulant

The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the transmission coefficient of the Moon’s surface, and plays an important role in the Moon research. In order to study the dielectric properties of the lunar regolith, the lunar regolith simulant was made according to the making procedure of the CAS-1 simulant made by Chinese Academy of Sciences. Then the dielectric constants of the lunar regolith simulant were measured with 85070E Aiglent Microwave Network Analyzer in the frequency ranging from 0.2 GHz to 20.0 GHz and at temperature of 25.1°C, 17.7°C, 13.1°C, 11.5°C, 9.6°C, 8.0°C, 4.1°C, −0.3°C, −4.7°C, −9.5°C, −18.7°C, −27.7°C, and −32.6°C, respectively. The Odelevsky model was employed to remove the influence of water in the air on the final effective dielectric constants. The results indicate that frequency and temperature have apparent influences on the dielectric constants of the lunar regolith simulant. The real parts of the dielectric constants increase fast over the range of 0.2 GHz to 3.0 GHz, but decrease slowly over the range of 4.0 GHz to 20.0 GHz. The opposite phenomenon occurs in the imaginary parts. The influences of the frequency and temperature on the brightness temperature were also estimated based on the radiative transfer equation. The result shows that the variation of the frequency and temperature results in great changes of the microwave brightness temperature emitting from the lunar regolith.