P51C-2074
Studies based on global subsurface radar sounding of the Moon by SELENE (Kaguya) Lunar Radar Sounder (LRS): A summary

Friday, 18 December 2015
Poster Hall (Moscone South)
Atsushi Kumamoto1, Yasushi Yamaguchi2, Atsushi Yamaji3, Takao Kobayashi4, Shoko Oshigami5, Ken Ishiyama1, Norihiro Nakamura1 and Yoshitaka Goto6, (1)Tohoku University, Sendai, Japan, (2)Nagoya University, Nagoya, Japan, (3)Kyoto University, Kyoto, Japan, (4)KIGAM, Daejeon, South Korea, (5)National Astronomical Observatory of Japan, Oshu, Japan, (6)Kanazawa University, Kanazawa, Japan
Abstract:
The Lunar Radar Sounder (LRS) onboard the SELENE (Kaguya) spacecraft has successfully performed radar sounder observations of the lunar subsurface structures and passive observations of natural radio and plasma waves from the lunar orbit. After the transfer of the spacecraft into the final lunar orbit and antenna deployment, the operation of LRS started on October 29, 2007. Through the operation until June 10, 2009, 130 million pulses worth of radar sounder data have been obtained [Ono et al., 2010]. Based on the datasets of the first lunar global subsurface radar sounding, Ono et al. [2009] revealed that there are distinct reflectors at a depth of several hundred meters in the nearside maria, which are inferred to be buried regolith layers covered by a basalt layer with a thickness of several hundred meters.

Based on the further survey, Pommerol et al. [2010] pointed out the negative correlation of clear subsurface echoes with the maps of ilmenite, and suggested that dense ilmenite attenuates the radar pulse in the basaltic mare lava, and cause the absence of the clear subsurface echoes. That also suggests there are undetected subsurface reflectors especially below the young lava flow units with high ilmenite abundance.

Kobayashi et al. [2012] applied synthetic aperture radar (SAR) processing to SELENE LRS data in order to obtain distinct radargram. Taking advantage of analyzing waveform data sent via high data rate telemetry from the Moon, we can perform advanced data analyses on the ground. We started providing the both SAR processed and waveform datasets via SELENE Data Archive (http://l2db.selene.darts.isas.jaxa.jp/index.html.en) since 2015.

Oshigami et al. [2014] estimated volumes of basalt units in the ages of 2.7 Ga to 3.8 Ga in the nearside maria. The volume was derived from the depth of subsurface reflectors measured by LRS. The volumes of the geologic units were 103 to 104 km3. The average eruption rates were 10-5 to 10-3 km3 yr-1. The estimated volumes of the geologic mare units and average eruption rate showed clear positive correlations with their ages.

In the presentation, we are going to review not only the studies mentioned above but also some recent studies such as Ishiyama et al. [2013], and Bando et al. [2015].

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