| Project/Area Number |
04554013
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| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体地球物理学
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| Research Institution | National Astronomical Observatory (NAO) |
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Principal Investigator |
OOE Masatsugu NAO,Div.Earth Rotation, Professor, 地球回転研究系, 教授 (00088783)
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| Co-Investigator(Kenkyū-buntansha) |
HANADA Hideo NAO,Div.Earth Rotation, Assistant, 地球回転研究系, 助手 (60132677)
SASAO Tetsuo NAO,Div.Earth Rotation, Professor, 地球回転研究系, 教授 (20000177)
KAWAGUCHI Noriyuki NAO,Div.Radio Astronomy, Assistant Professor, 電波天文学研究系, 助教授 (90214618)
KUJI Seisuke NAO,Div.Earth Rotation, Assistant, 地球回転研究系, 助手 (40132675)
KAWANO Nobuyuki NAO,Div.Earth Rotation, Professor, 地球回転研究系, 教授 (10186116)
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| Project Period (FY) |
1992 – 1994
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| Keywords | Differential VLBI / Physical librations / Lunar tides / Radio transmitter / Atmoshperic fluctuation / Lunar orbiter / Radiation pattern / Hard landing |
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| Research Abstract |
We have developed an artificial radio transmitter for differential VLBI in order to measure lunar physical librations and lunar tides precisely. We completed the total aystem including a 2.2GHz transmitter, a battery package, a timer and an antenna by the end of 1992, and confirmed that the frequency stability is better than 10 ^<-6> and that the system can survive under acceleration of 10,000g (1g=9.8ms ^<-2>), which is equivalent to that received when the transmitter dropped from a lunar orbiter on the altitude of 200Km collides to the lunar surface. We prepared sands which have similar electrical properties to the lunar regolith, and measured radiation patterns and intensities of CW radio signals emitted from the transmitter buried in the sands by changing the depth and the agale between the anttena surafce and the sand surface. As the results, we could obtain the condition which the transmitter should satisfy on the Moon.
This research is characterized by 1)development of the radio transmitter tolerating a hard landing on the lunar surface and 2)development of a method of the differential VLBI which can measure an angular distance between two radio sources on the Moon precisely, eliminating the effect of atmospheric fluctuation. We confirmed that the differential VLBI can determine the amplitude of the lunar physical librations with an accuracy of 10 ^<-5>, which is 10 times better than the previous results, and that of the lunar tides with an accuracy of 10 ^<-1>, respectively.
This radio transmitter will have great power and possibilities and wide applications in planetary science. The method of setting the radio transmitter on the lunar surface by hard landing has been established and a new approach into the planetary science has been prospected through this research.
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