The Lunar Instrumentation for Subsurface Thermal Exploration with Rapidity (LISTER) on Blue Ghost Mission 1 to Mare Crisium. I. Pneumatic Excavation of Regolith

Abstract The Lunar Instrumentation for Subsurface Thermal Exploration with Rapidity (LISTER) is the first robotically deployed subsurface thermal probe that actively excavates lunar regolith and makes scientific measurements at multiple depths. It was deployed in Mare Crisium on Blue Ghost Mission 1 in 2025 March, reached 1 m depth, and measured the temperature and thermal conductivity of the regolith at eight different depths. The previous depth record for robotic in situ thermal measurements of the Moon was 8 cm. LISTER utilizes the pneumatic excavation technique, blowing a jet of pressurized nitrogen gas, as it pushes its thermal probe into the regolith. The gas expands rapidly in the lunar vacuum and lofts regolith clumps and clasts out of the hole. When the probe reaches one of the depths targeted for thermal measurements, LISTER stops blowing gas and pushes the probe into the yet-to-be-excavated bottom-hole regolith. It completes the necessary thermal measurements in 2 hr and then resumes excavation to the next targeted depth. LISTER detects obstacles on its way by monitoring the weight on bit (WOB). When the WOB exceeds a programmable threshold, LISTER attempts to dislodge the obstacle by automatically performing a piston-like vibratory movement (“dithering”), while it keeps blowing gas. Finally, video-monitoring the ejecta from LISTER’s excavation operations is useful in studying the stratigraphy of the regolith.