Using DAS-Fibres for Lunar Seismic Imaging

Kurzfassung

A set of major mission themes has emerged from the 2020 ESA Call for Ideas, "Exploring the Moon with a large European lander", with a polar ice prospecting mission identified and currently being studied as a candidate EL3 science mission. A combination of Ground-Penetrating Radar (GPR), Magnetic Induc-tion Spectroscopy (MIS) and Distributed Acoustic Sensing (DAS) has been proposed to localize and 3D-map water ice and volatiles in the subsurface. In 2020 CGF (Centre for Geophysical Forecasting at NTNU) conducted a DAS field test using one DAS (Distributed Acoustic Sensing) interrogator located in Longyearbyen. An interrogator is a laser instru-ment that sends light into a fiber optic cable to perform real-time measurements of strain. This operation was a cooperation between CGF/NTNU, and industry. 40 days of continuous DAS recording was successfully completed, and the results demonstrate the huge potential of using telecommunication fibre cables for underwater sensing. We recorded more than 800 whale soundings, several earthquakes, ship passing and long distance Atlantic storms in 2020. In another field test in 2021 CGF established a field station in a quick clay area in Rissa, Norway for the purpose of acoustic monitoring of the clay proper-ties. Both these experiments were successful and proved that good DAS-data can be acquired using the newly developed high-energy interrogator.