| Co-Investigator(Kenkyū-buntansha) |
KAWAGUCHI Noriyuki NATIONAL ASTRON.OBS PROF., 地球回転研究系, 教授 (90214618)
MIYAZAKI Tomoyuki FACULTY OF ENG., KAGOSHIMA UNIV.PROF., 工学部, 教授 (80037241)
OMODAKA Toshihiro FACUTLTY OF SCIENCE, KAGOSHIMA UNIV.PROF., 理学部, 教授 (50129285)
SASAO Tetsuo NATIONAL ASTRON.OBS.PROF., 地球回転研究系, 教授 (20000177)
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| Research Abstract |
For real-time VIBL observations of the 19GHz beacon signals from geostationary satellites with the Kagoshima 6-m diameter and the Mizusawa 10-m diameter radio telescopes, a subsystem attached to the radio telescopes is developed, which consist of base-band frequency converters, data acquisition units, signals transmission units and a cross-correlator. The software for data transmission and cross-correlation is also developed. VLBI observations with the subsystem attached to the radio telescopes were made using the beacons waves of the geostationary satellites, where the baseline length was about 1300 km. We confirmed that the cross-correlation was obtained in real time. For the cross-correlation data, we have checked if the fluctuations of atmospheric propagation delay can be detected. Origins of the phase fluctuations included in the cross-correlation data were analyzed in detail, and we obtained following results ; (1) contribution of the receiver noise was negligibly small, (2) drif
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t of phase caused by the diurnal motion of the satellite and the effect of the frequency deviation of the beacon signal could be removed from the observed data, and (3) the frequency deviation of hydrogen maser oscillators installed in the radio telescopes as master oscillators was a main source of fast phase variation with the duration shorter than 10 sec, while its effect was negligible at the range of longer than 10 sec. We conclude the phase fluctuations with the duration from 10 to 100 sec are originated from the atmospheric disturbances. In addition, we conclude that smaller diameter antennas, such as 1-m diameter paraboloidal antennas, can be used for detection of the atmospheric disturbances.
This project makes it clear that (1) the real-time diagnosis of the VLBI system is achieved with simple and low-cost devices, such as commercial-based A-D converters, personal computers and communication devices, (2) fluctuation of radio propagation delay caused by atmospheric disturbance is detectable by the VLBI observations of the beacon waves of the geostationary satellites, (3) a radio monitoring system of the atmospheric disturbance can be constructed with small diameter antennas, low-cost receivers and commercial-based data processing units. The results obtained by this project are published as papers and proceedings, such as IEICE Transaction, SPIE Proceedings, ISAP Proceedings and so on. A follow-up study of this project is in progress and further papers will be appeared. Less
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