The Lunar Radar Sounder (LRS) onboard the KAGUYA (SELENE) spacecraft

T. Ono, A. Kumamoto, Y. Kasahara, Y. Yamaguchi, A. Yamaji, T. Kobayashi, S. Oshigami, H. Nakagawa, Y. Goto, K. Hashimoto, Y. Omura, T. Imachi, H. Matsumoto, H. Oya

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)

Abstract

The Lunar Radar Sounder (LRS) onboard the KAGUYA (SELENE) 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, 2363 hours worth of radar sounder data and 8961 hours worth of natural radio and plasma wave data have been obtained. It was revealed through radar sounder observations 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. Radar sounder data were obtained not only in the nearside maria but also in other regions such as the farside highland region and polar region. LRS also performed passive observations of natural plasma waves associated with interaction processes between the solar wind plasma and the moon, and the natural waves from the Earth, the sun, and Jupiter. Natural radio waves such as auroral kilometric radiation (AKR) with interference patterns caused by the lunar surface reflections, and Jovian hectometric (HOM) emissions were detected. Intense electrostatic plasma waves around 20 kHz were almost always observed at local electron plasma frequency in the solar wind, and the electron density profile, including the lunar wake boundary, was derived along the spacecraft trajectory. Broadband noises below several kHz were frequently observed in the dayside and wake boundary of the moon and it was found that a portion of them consist of bipolar pulses. The datasets obtained by LRS will make contributions for studies on the lunar geology and physical processes of natural radio and plasma wave generation and propagation.

Original languageEnglish
Pages (from-to)145-192
Number of pages48
JournalSpace Science Reviews
Volume154
Issue number1-4
DOIs
Publication statusPublished - 2010 Jul

Keywords

  • Auroral kilometric radiation (AKR)
  • Buried regolith
  • Electrostatic solitary waves (ESW)
  • Jovian hectometric (HOM) radiation
  • KAGUYA (SELENE) spacecraft
  • Lunar Radar Sounder (LRS)
  • Lunar mare layered deposits
  • Lunar subsurface radar sounding
  • Lunar wake

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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