An in-situ 3D elemental imager for planetary missions based on active neutron interrogation

Abstract The In Situ Nuclear Spectrometer with 3D Resolution (INSPECT3R) is a compact, 3D elemental imaging system for planetary exploration based on the Associated Particle Imaging (API) technique. This active neutron interrogation instrument achieves centimeter-scale spatial resolution (8 cm × 8 cm × 10 cm) over volumes of up to 50 cm × 50 cm × 40 cm—surpassing the capabilities of existing in-situ planetary nuclear spectrometers. INSPECT3R enables non-destructive, volumetric mapping of elemental composition, resolving layered structures and subsurface heterogeneities while suppressing all environmental background signals through coincidence detection. We present a series of experiments with lunar regolith simulants demonstrating INSPECT3R’s ability to identify and localize key elements and buried objects with high precision. This technology offers transformative potential for future planetary science and astrobiology missions and for In Situ Resource Utilization (ISRU) activities on the Moon and elsewhere, providing a new dimension of spatially resolved geochemical analysis critical to surface missions.