Detecting Loose Regolith in Lunar Craters Using Thermal Imaging

Abstract

Robotic missions could soon explore permanently shadowed craters on the lunar poles in order to characterize ice accumulation beneath the surface. However, the regolith in these craters is hypothesized to be very loose and could endanger a rover mission. This work analyzes the ability of thermal imaging to detect hazardous, low-density regolith in shadowed regions on the lunar poles. A series of simulations was conducted to estimate the surface temperature of lunar regolith as a function of density in polar craters. A generalized lunar crater model was used, and thermal properties of regolith were taken from experiments on Apollo samples. Results showed that in most situations there is a difference in temperature between nominal and loose regolith samples. This effect is most consistent at night in the absence of solar radiation and generally causes temperature differences between 2 K and 3 K. Based on comparisons to the capabilities of the DIVINER lunar radiometer, it is likely that regolith density differences would be detectable by a rover-mounted instrument.