Lunar Exploration Gas Spectrometer

The Lunar Exploration Gas Spectrometer (LEGS) is an instrument for studying the gas composition of lunar regolith. In the LEGS a 2.5 GHz solid state microwave transmitter positioned on a downward pointing horn is deployed by a lunar lander or rover using a long boom (e.g. 1-2 m) to set it down on the lunar surface, and then beams power into the regolith using its microwave transmitter. The microwaves directed down onto and into the ground contained under the horn, heating regolith to depths of several tens of centimeters. As a result, gases will be evolved from the cold subsurface regolith into the horn, where their composition will be analyzed by a near-infrared ~1 to 2.4-micron spectrometer mounted horn, and looking through a sapphire window into the interior of the horn illuminated by a tungsten lamp, enabling transmission spectra of evolved gases to be obtained. These instruments will provide qualitative and quantitative data on volatiles, potentially including water, hydrogen, helium, CO2, CO, ammonia hydrocarbons, and other species as they evolve from the subsurface over time. Since gases released by upper layers of regolith will reach the horn first, this procedure will also provide composition as a function of depth. Once gas emission ceases, the horn is lifted by the rod and placed on a new location, where the process is repeated. The LEGS deployment will involve very little disturbance to lunar soils prior to analysis, thereby preventing the accidental release of lightly-bound volatiles that is thought to be significant even following gentle handling. In the proposed program, a full scale working model of the LEGS, including horn, microwave transmitter, and spectrometer, will be built and tested in Pioneer Astronautics