| Project/Area Number |
10640240
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Astronomy
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| Research Institution | National Astronomical Observatory |
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Principal Investigator |
HARA Tadayoshi NAOJ Div. Earth Rotation, Associate prof., 地球回転研究系, 助教授 (60000171)
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| Co-Investigator(Kenkyū-buntansha) |
SATO K.-h. Mizusawa Astrogeodynamics Obs., Assistant, 水沢観測センター, 助手 (90178715)
KUJI S NAOJ Div. Earth Rotation, Assistant, 地球回転研究系, 助手 (40132675)
SASAO Tetuo NAOJ Div. Earth Rotation, Associate prof., Professor, 地球回転研究系, 教授 (20000177)
MIYOSHI M. NAOJ Div. Earth Rotation, Assistant, 地球回転研究系, 助手 (50270450)
KAMEYA O. Mizusawa Astrogeodynamics Obs., Assistant, 水沢観測センター, 助手 (70202025)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 1999: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1998: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Keywords | Troposphere / Radiometer / 22GHz / Continuum components / 2 channel / 10m antenna / Spatially differential / 水蒸気ラジオメータ / 超過光路長 / 受信機利得変動 / 輝度温度 |
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| Research Abstract |
Fluctuations of tropospheric propagation delay is one of the most serious problem for radio astronomical observations on the earth's surface. Study on the method to compensate the effect of troposphere was made by observing the atmospheric phase fluctuations by the developed spatially differential radiometer. Some of the results are reported here.
The antenna which has a narrow beam and high speed and short settle time is required for the research mentioned above. The 10m antenna at the Mizusawa Astro Geodynamic Center was used for it's high speed drive system attained by the digital control system for our research. This antenna system is mainly used for radio astronomy observations. Atmospheric brightness temperature was measured by adding some devices necessary for radiometer to this antenna system. The bandwidth of the receiver system is pretty narrow for 2-channel radiometer as much as 2GHz. This system, however, was confirmed to be effective to remove the continuum components such as liquid water by the measurement on a humid weather condition. The Allan standard deviation (ASD) showed the typical characteristics of the atmospheric phase fluctuations. The ASD was calculated from the time series data of the excess path length (EPL) calculated from the atmospheric brightness temperature with the antenna pointing to the zenith.
Confirming the basic function of our radiometer, experiments for spatially differential radiometer were performed by switching the antenna pointing by 5 deg. And 10 dig. In azimuth angle in space while the elevation angle was fixed at 60 dig. It was confirmed that the ASD of the differential phase changed from the flicker frequency noise to white phase noise at the time scale corresponds to the spatial separation angle.
Further improvements are desired to attain sub-mm order differential EPLdetection every several seconds by reducing both random and systematic noises.
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