1992 Fiscal Year Final Research Report Summary
Development of Image Reconstruction Methods for a Hard X-ray Telescope of the Fourier-Synthesis Type
| Project/Area Number |
02452011
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Astronomy
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| Research Institution | National Astronomical Observatory (1992)
The University of Tokyo (1990-1991) |
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Principal Investigator |
KOSUGI Takeo National Astronomical Obs., Radio Astronomy Division, Professor, 電波天文学研究系, 教授 (70107473)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAO Taro National Astronomical Obs., Solar Physics Division, Research Assistant, 太陽物理学研究系, 助手 (00225781)
SHIBASAKI Kiyoto National Astronomical Obs., Radio Astronomy Division, Associated Professor, 電波天文学研究系, 助教授 (90023689)
TSUNETA Saku University of Tokyo, Institute of Astronomy, Associated Professor, 理学部, 助教授 (50188603)
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| Project Period (FY) |
1990 – 1992
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| Keywords | Solar flares / Hard X-ray imaging / Hard X-ray telescope / Modulation collimator / Fourier synthesis / Image reconstruction / Maximum Entropy Method |
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| Research Abstract |
The aims of this project are to develop image reconstruction methods for hard X-ray imagery of the Fourier-synthesis type, especially for the Hard X-ray Telescope (HXT) onboard the SOLAR-A ("Yohkoh") satellite, and also to construct an image analysis system on a workstation. In 1990, we wrote a Maximum Entropy (MEM) image reconstruction program, and precisely measured the X-ray transmissivity functions (modulation patterns) of the HXT collimators which are key parameters of MEM. Since the launch of "Yohkoh" on 1991 August 30, we applied this program to actual solar flare data, and revised it to be suitable for analyzing actual data. In 1991 through 1992, we have constructed an image analysis/handling system on a workstation, conducted research on hard X-ray sources from solar flares, and published "The Yohkoh HXT Databook, No.1". From this project it is confirmed that:
(1) The HXT works well as an imagery, i.e., the design is correct.
(2) The MEM program provides images with as good image quality as expected.
(3) X-ray sources of solar flares are found to be essentially double at high X-ray energies above 50 keV. Simultaneous variation of the two sources suggest that electrons are accelerated near the top of a loop and that they precipitate along the loop into the two footpoints where they emit X-rays.
(4) The height of hard X-ray sources is found to decrease with increasing X-ray energies, which is supporting evidence for the above interpretation.
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