Preliminary results of compressional seismic wave velocity measurements of lunar regolith simulant (JSC-1) during a microgravity flight campaign

Low velocity compressional wave (P-wave), Vp values, have been observed from the lunar geophysical measurements made during the Apollo 14, 16 and 17 missions. These low velocities are attributed to lack of water, low soil compaction as well as the non-consolidated nature of the regolith. The microgravity lunar regolith simulant velocity experiment (μ-SVeLSE) aims to determine if there is any dependence of gravitational force on the seismic longitudinal velocity measurements and thus correlate with data previously determined from in-situ lunar regolith measurements. The experiment is composed of a small cylindrical container and a low power control and data acquisition electronics. No external power source was necessary. The prototype is comprised of a regolith container (22cm x 7cm) with all the data acquisition and control electronics included and working on a low voltage battery power sources. The system, designed by us, produces very minute vibration impulses. The impulses from the source transducer (Tx) are sent during limited temporal windows of emission-reception (10 milliseconds), and recorded as weak sonic-ultrasonic impulses that reach the two receivers (Rx). The system has just a start-stop switch than can be initiated directly by a wireless mechanism. The system records the data on a micro-SD card and weighed, together with the lunar regolith (JSC-1), approximately 1.4 kg. The container is completely closed and designed not to vent any regolith particles. During October 2018 we took the experiment onboard an airborne microgravity campaign, carried out in Ottawa (Canada) by the National Research Council’s Falcon 20 aircraft. We acquired data on three parabolas of between 15 and 30 seconds with low noise microgravity values. Preliminary Vp measurement results, compared with those obtained in Earth’s normal 1g, show variations of signal amplitude that are attributed to lower coupling of the source and receivers to the suspended grains during the micro-g phases of flight. Vp velocity results measured during 1g were around 90 m/s whereas during micro-g phases of flight the velocities apparently decreased.
19th International Multidisciplinary Scientific Geoconference, SGEM 2019, June 30 - July 6, 2019, Albena, Bulgaria
Series: International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM