DAS system for the Moon

Active seismic experiments during the Apollo missions characterized the lunar regolith and crust, while passive monitoring suggested a thermal stress origin for the high-frequency lunar seismic noise. Deploying Distributed Acoustic Sensing (DAS) instruments, capable of withstanding the extreme lunar conditions, would allow to examine various lunar environments including permanently shadowed regions, which trap water ice due to their extremely cold temperatures. Benefiting from high spatial and temporal resolutions, DAS surveys would allow analyzing wave propagation, constructing 2D wave velocity sections, and potentially identifying ice-related velocity variations. How the DAS technology positions in terms of self-noise with respect to Apollo and modern sensors? We estimate the strain noise level of geophones to be around 1 pε/sqrt(Hz). For a 5-km long optic fiber with 10 meters gauge length, the typical self-noise of current DAS systems is around 1 pε/sqrt(Hz). This indicates that DAS instruments may achieve a low noise level on par with the best current geophysical technologies, which is crucial for precise and reliable exploration of lunar structure. We will discuss experiments that would be necessary for qualifying such an instrument for space applications.