Distributed Acoustic Sensing for Subsurface Characterization in a LUNA Moon analog test facility

Distributed Acoustic Sensing (DAS) has emerged as a powerful fibre-optic technology for high-resolution seismic monitoring, particularly in environments where conventional sensor deployment is limited or impractical. Its ability to transform standard fibre-optic cables into dense arrays of virtual sensors offers significant advantages for applications in extreme and remote settings, including planetary exploration. In this study, we investigate the feasibility and performance of DAS for subsurface characterization under controlled lunar-analogue conditions. 
The experiment was conducted in the LUNA Moon analog test facility at the German Aerospace Center (DLR), which provides a controlled environment designed to simulate key aspects of extraterrestrial surfaces. The primary objective was to evaluate the applicability of refraction seismics for detecting subsurface structures analogous to water ice deposits, which is one of the most critical resources for future lunar and planetary missions. 

A DAS system was deployed along a fibre-optic cable to record seismic wavefields with high spatial resolution. To generate seismic energy, we employed a combination of active source types with complementary characteristics. Impulsive sources, such as sledgehammer impacts, were used to produce high-amplitude, broadband signals suitable for shallow subsurface imaging. In addition, a PASS (Portable Active Seismic Source) system was utilized to provide a controlled source sweep with distinct frequency features, enabling a systematic coverage of the frequency spectrum and the corresponding penetration depths.

The integration of these source types allows for enhanced flexibility in seismic data acquisition and facilitates a more comprehensive analysis of subsurface properties. The recorded DAS data were processed using refraction seismic techniques to identify velocity contrasts associated with potential ice-equivalent layers. The controlled test environment enables direct assessment of signal quality, repeatability, and resolution, offering valuable insights into the strengths and limitations of DAS under conditions relevant to planetary exploration. 

Our results demonstrate that DAS is capable of capturing seismic signals in a lunar-analogue setting and shows high sensitivity to heterogenities in the shallow subsurface. The combination of different seismic sources proves particularly effective in optimizing data quality across varying depths and frequency ranges. These findings highlight the potential of fibre-optic sensing technologies as a robust and scalable solution for future geophysical investigations beyond Earth. This work contributes to the advancement of seismic exploration methodologies for extreme environments and supports the development of innovative sensing strategies for upcoming missions targeting the Moon and other planetary bodies.