Near-Infrared Monitoring of Volatiles in Frozen Lunar Simulants While Drilling

摘要

In Situ Resource Utilization (ISRU) focuses on using local resources for mission consumables. The approach can reduce mission cost and risk. Lunar polar volatiles, e.g. water ice, have been detected via remote sensing measurements and represent a potential resource for both humans and propellant. The exact nature of the horizontal and depth distribution of the ice remains to be documented in situ. NASA's Resource Prospector mission (RP) is intended to investigate the polar volatiles using a rover, drill, and the RESOLVE science package. RP component level hardware is undergoing testing in relevant lunar conditions (cryovacuum). In March 2015 a series of drilling tests were undertaken using the Honeybee Robotics RP Drill, Near-Infrared Volatile Spectrometer System (NIRVSS), and sample capture mechanisms (SCM) inside a 'dirty' thermal vacuum chamber at the NASA Glenn Research Center. The goal of these tests was to investigate the ability of NIRVSS to monitor volatiles during drilling activities and assess delivery of soil sample transfer to the SCMs in order to elucidate the concept of operations associated with this regolith sampling method. Ten soil samples were captured over the course of two tests at pressures of 10~(-7)-10~(-5) Torr and soil temperatures were 203° to 213° K and ≈93° K for tests 1 and 2, respectively. Each sample was obtained from a depth of 30 to 40 cm within a cryogenically frozen layered bed of NU-LHT-3M lunar regolith simulant. The simulant was doped with 0.1 and 0.2 wt.% water in the upper ～16 cm, for test 1 and 2 respectively, and ～5 wt.% of water below, for both tests, with the two layers separated by aluminum foil. For each sample the drilling sequence consisted of insertion and extraction of the drill to 10, 20, 30, and 40 cm depths, and after the final depth the sample was delivered to the SCM. NIRVSS acquired spectra and images during the drilling sequence and these are the focus of the discussion here. NIRVSS spectra exhibit spectral features associated with water ice after the drill penetrated the aluminum barrier, and especially on extraction from 20 cm depth. These spectral features can be temporally correlated with measurements of the evolved water from the surface during the drilling sequence and images document the growth and evolution of the cuttings pile deposited by the drill. The spectra and images also document some anomalous behavior associated with the refilling of an existing hole due to the constraints imposed by the confined dimensions of the chamber.