P062-04
Active-Source Seismology Using Astronaut Surface Operations During the Apollo 11 Mission

Monday, 14 December 2020: 20:42
Virtual
Aisha Khatib1, Nicholas C Schmerr1, Ben Fesit2, Jeffrey B Plescia1,3 and Noah E Petro4, (1)University of Maryland College Park, College Park, MD, United States, (2)NASA Johnson Space Center, Houston, TX, United States, (3)Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States, (4)NASA GSFC, Greenbelt, MD, United States
Recorded Presentation
Abstract:
The Passive Seismic Experiment Package (PSEP) on the Apollo 11 mission provided the first seismic data from another body in the Solar System. As the instrument was placed close to the lunar module (LM) and collected data during the EVA, it recorded seismic signal from the activities of the astronauts on the surface. Here, we use audio recordings of the astronaut surface activity to provide source times for seismic signal to conduct an active-source seismology study of the subsurface at Tranquility Base.

The seismic sources we investigate include the hammer strokes from the core tube sample collections, disassembly of the solar wind experiment, the Hasselblad camera pack dropping onto the surface as the astronauts loaded equipment before reentering the LM, and the jettison of the astronauts’ portable life support systems.

The time delay between signal generation and arrival is calculated using the time differences between the event signals in the seismic data and the event signals in the audio data, taken from the astronauts’ microphones from their correspondence with Mission Control in Houston, Texas. At each event onset, the time associated with the event in the audio signal (± 50 ms) is considered time of the signal generation, and the time associated with the signal in the seismic data is considered time of arrival (± 30 ms). Spatial positions of the astronaut activities are facilitated by Lunar Reconnaissance Orbiter Camera Narrow Angle Camera image M150361817R which provides precise (±1 m) locations, and footage from the command module television camera.

The preliminary seismic velocities obtained from these events are 45 to 50 m/s (± 2 to 6 m/s), and correspond to much shallower sub-surface depths (~10-20 m) than the active source studies performed on later Apollo missions. This study shows that astronaut surface activities provide an opportunity to collect seismic signal on other missions, but also illustrates that activity and transmission timelines, instrument timing, and relative location must be precisely and synchronously recorded to enable geophysical sounding.

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