[S19-2] Apollo seismic data re-processing and future lunar seismology project

[S19-2-05] Updated travel time analysis of Apollo artificial impacts' seismic data with the precise source locations identified by LRO

^○Keisuke Onodera^{1, 2}, Satoshi Tanaka², Taichi Kawamura³, Yoshiaki Ishihara² (1.SOKENDAI (The Graduate University for Advanced Studies), 2.JAXA/ISAS(Japan Aerospace Exploration Agency/Institute of Space and Astronautical Science), 3.NAOJ(National Astronomical Observatory of Japan))

In the previous lunar seismic analyses, the artificial impacts were often used to constrain the lunar crustal thickness. The S-IVB rocket stages were deliberately impacted on the lunar surface for seismic investigation and the impact sites were obtained from radio contacts with the booster. Recently, the precise source locations of the five S-IVB impacts were updated with Lunar Reconnaissance Orbiter(LRO) image data. The updated locations resulted in change in the reference source locations for the travel time analysis with these artificial impacts. The most significant change was in Apollo 16 S-IVB. Loss of radio contact between the booster rocket stage left large uncertainties on the location of the impact. We found that Apollo16 S-IVB impact site estimated in Apollo era was different from the precise one by about 30 km. In this study, we re-analyzed artificial impacts' seismic data using the precise source locations to determine more accurately the crustal thickness of the Moon. We will present the crustal thickness around the Apollo landing site and discuss the effect of local structure that might affect the travel time analyses. We will also discuss implications for future lunar seismic exploration for better understandings of lunar crustal structure.