Curriculum Vitaes
Profile Information
- Affiliation
- Japan Aerospace Exploration Agency
- J-GLOBAL ID
- 202001007325831201
- researchmap Member ID
- R000009366
Research Interests
8Papers
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JAXA Research and Development Report: Journal of Space Science Informatics Japan, JAXA-RR-22-009(12) 31-40, Feb 28, 2023 Peer-reviewedThis paper describes a method of interactive visualization for explaining the behavior of Single Flux Quantum (SFQ) circuits, a kind of logic circuit based on the principle of superconductivity. For the space exploration in the future, there has been an idea to develop devices based on SFQ circuits onboard spacecraft. SFQ circuits are expected to have extremely low power consumption and high computational speed during operation. On the other hand, since the principle of SFQ circuits is greatly different from that of logic circuits of semiconductor devices such as CPUs and memories, visualization tools for understanding such type of circuits are expected to be useful. In this paper we developed an interactive visualization application for SFQ circuits using JavaScript libraries including WebGL-based APIs and discussed issues as well as prospects.
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JAXA Research and Development Report: Journal of Space Science Informatics Japan, JAXA-RR-14-009(4) 1-13, Mar 31, 2015 Peer-reviewedCorresponding author
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JAXA Research and Development Report: Journal of Space Science Informatics Japan, JAXA-RR-14-009(4) 105-125, Mar 31, 2015 Peer-reviewedDARTS (http://darts.jaxa.jp/) is a scientific data archive system which provides data of scientific satellites launched by JAXA, and is developed and maintained by Center for Science-satellite Operation and Data Archive (C-SODA) in ISAS/JAXA. We have developed a web interface with search function to provide 2 dimensional image data (all-sky map) obtained from all sky survey observation of infrared astronomy satellite “AKARI”. The all-sky map is composed of many image files which are arranged like as tiles to cover whole celestial sphere and each image occupies a region about several square degrees. This search function is intended to return all image files in the region designated by a user, if they are overlapped with the region. To realize such a search, we adopt a method that each image is divided into a large number of small rectangular areas and then the center of each area is represented by an orthogonal coordinate system to register in the database. This method has the advantages that other external libraries to divide the celestial area such as HEALPix are not needed, and that both celestial poles is not treated as a singular point, and that high-speed search for arbitrary coordinate system can be obtained. To reduce the costs of development and maintenance, we apply the mechanism of AKARI catalogue search to this search function using PHP and PostgreSQL.
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JAXA Research and Development Report: Journal of Space Science Informatics Japan, JAXA-RR-13-010(3) 17-26, Mar 31, 2014 Peer-reviewedCorresponding authorGSTOS is Generic Spacecraft Test and Operations Software applied for test and operation system of future ISAS (Institute of Space and Aeronautical Science) spacecraft based on database SIB2 (Spacecraft Information Base version 2). SIB2/GSTOS-1 is a project to provide SIB2/GSTOS for SPRINT-A, ASTRO-H, Bepi/MMO. This paper describes goal, achievement relative to typical test and operation system for former ISAS spacecraft, development status and tasks for the future of SIB2/GSTOS-1.
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SOLAR PHYSICS AND SPACE WEATHER INSTRUMENTATION V, 8862, 2013 Peer-reviewedWe present a design progress of the Solar UV-Vis-IR Telescope (SUVIT) aboard the next Japanese solar mission SOLAR-C. SUVIT has an aperture diameter of similar to 1.4 m for achieving spectro-polarimetric observations with spatial and temporal resolution exceeding the Hinode Solar Optical Telescope (SOT). We have studied structural and thermal designs of the optical telescope as well as the optical interface between the telescope and the focal plane instruments. The focal plane instruments are installed into two packages, filtergraph and spectrograph packages. The spectropolarimeter is the instrument dedicated to accurate polarimetry in the three spectrum windows at 525 nm, 854 nm, and 1083 nm for observing magnetic fields at both the photospheric and chromospheric layers. We made optical design of the spectrograph accommodating the conventional slit spectrograph and the integral field unit (IFU) for two-dimensional coverage. We are running feasibility study of the IFU using fiber arrays consisting of rectangular cores.
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ASTROPHYSICAL JOURNAL, 688(2) 1374-1381, Dec, 2008 Peer-reviewedWe present observations of the magnetic landscape of the polar region of the Sun that are unprecedented in terms of spatial resolution, field of view, and polarimetric precision. They were carried out with the Solar Optical Telescope aboard Hinode. Using a Milne-Eddington inversion, we find many vertically oriented magnetic flux tubes with field strengths as strong as 1 kG scattered in latitude between 70 degrees and 90 degrees. They all have the same polarity, consistent with the global polarity of the polar region. The field vectors are observed to diverge from the centers of the flux elements, consistent with a view of magnetic fields that are expanding and fanning out with height. The polar region is also found to have ubiquitous horizontal fields. The polar regions are the source of the fast solar wind, which is channeled along unipolar coronal magnetic fields whose photospheric source is evidently rooted in the strong-field, vertical patches of flux. We conjecture that vertical flux tubes with large expansion around the photospheric-coronal boundary serve as efficient chimneys for Alfven waves that accelerate the solar wind.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 60(4) 827-834, Aug, 2008We obtained temperature structures in faint coronal features above and near the solar limb with the X-Ray Telescope aboard the Hinode satellite by accurately correcting the scattered X-rays from surrounding bright regions with occulted images during the solar eclipses. Our analysis yields a polar coronal hole temperature of about 1.0 MK and an emission measure in the range of 10(25.5)-10(26.0) cm(-5). In addition, our methods allow us to measure the temperature and emission measure of two distinct quiet-Sun structures: radial (plume-like) structures near the boundary of the coronal-hole and diffuse quiet Sun regions at mid-latitudes. The radial structures appear to have increasing temperature with height during the first 100 Mm, and constant temperatures above 100 Mm. For the diffuse quiet-Sun region the temperatures are the highest just above the limb, and appear to decrease with height. These differences may be due to different magnetic configurations.
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SOLAR PHYSICS, 249(2) 263-279, Jun, 2008 Peer-reviewedThe X-ray Telescope (XRT) aboard the Hinode satellite is a grazing incidence X-ray imager equipped with a 2048x2048 CCD. The XRT has 1 arcsec pixels with a wide field of view of 34x34 arcmin. It is sensitive to plasmas with a wide temperature range from < 1 to 30 MK, allowing us to obtain TRACE-like low-temperature images as well as Yohkoh/SXT-like high-temperature images. The spacecraft Mission Data Processor (MDP) controls the XRT through sequence tables with versatile autonomous functions such as exposure control, region-of-interest tracking, flare detection, and flare location identification. Data are compressed either with DPCM or JPEG, depending on the purpose. This results in higher cadence and/or wider field of view for a given telemetry bandwidth. With a focus adjust mechanism, a higher resolution of Gaussian focus may be available on-axis. This paper follows the first instrument paper for the XRT (Golub et al., Solar Phys. 243, 63, 2007) and discusses the design and measured performance of the X-ray CCD camera for the XRT and its control system with the MDP.
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SOLAR PHYSICS, 249(2) 221-232, Jun, 2008 Peer-reviewedThe Hinode Solar Optical Telescope (SOT) is the first space-borne visible-light telescope that enables us to observe magnetic-field dynamics in the solar lower atmosphere with 0.2-0.3 arcsec spatial resolution under extremely stable (seeing-free) conditions. To achieve precise measurements of the polarization with diffraction-limited images, stable pointing of the telescope (< 0.09 arcsec, 3 sigma) is required for solar images exposed on the focal plane CCD detectors. SOT has an image stabilization system that uses image displacements calculated from correlation tracking of solar granules to control a piezo-driven tip-tilt mirror. The system minimizes the motions of images for frequencies lower than 14 Hz while the satellite and telescope structural design damps microvibration in higher frequency ranges. It has been confirmed from the data taken on orbit that the remaining jitter is less than 0.03 arcsec (3 sigma) on the Sun. This excellent performance makes a major contribution to successful precise polarimetric measurements with 0.2-0.3 arcsec resolution.
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FIRST RESULTS FROM HINODE, 397 102-+, 2008We present Hinode/EIS raster scan observations of the GOES X3.2 flare that occurred on 2006 December 13. There was a small transient coronal hole which was located 200 arcsec east of the flare arcade. The transient coronal hole was strongly affected by the X-class flare, and the strong upflows were observed in Fe XV line 284.2 angstrom (log T/K = 6.3) at the boundary of dimming region. In this paper, we discuss how to obtain the velocity map by correcting the instrumental effects.
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Science (New York, N.Y.), 318(5856) 1585-8, Dec 7, 2007The Sun continuously expels a huge amount of ionized material into interplanetary space as the solar wind. Despite its influence on the heliospheric environment, the origin of the solar wind has yet to be well identified. In this paper, we report Hinode X-ray Telescope observations of a solar active region. At the edge of the active region, located adjacent to a coronal hole, a pattern of continuous outflow of soft-x-ray-emitting plasmas was identified emanating along apparently open magnetic field lines and into the upper corona. Estimates of temperature and density for the outflowing plasmas suggest a mass loss rate that amounts to approximately 1/4 of the total mass loss rate of the solar wind. These outflows may be indicative of one of the solar wind sources at the Sun.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 59 S757-S762, Nov, 2007 Peer-reviewedThe velocity structures of jets in a coronal hole have been derived for the first time. Hinode observations revealed the existence of many bright points in coronal holes. They are loop-shaped and sometimes associated with coronal jets. Spectra obtained with the Extreme-ultraviolet Imaging Spectrometer aboard Hinode were analyzed to infer the Doppler velocity of bright loops and jets in a coronal hole of the north polar region. Elongated jets above bright loops are found to be blue-shifted by 30 km s(-1) at maximum, while foot points of bright loops are red-shifted. Blue-shifts detected in coronal jets are interpreted as being upflows produced by magnetic reconnection between emerging flux and the ambient field in the coronal hole.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 59(S3) S793-S799, Nov, 2007We present Hinode/EIS raster scan observations of the plage region taken during the gradual phase of the GOES X3.2 flare that occurred on 2006 December 13. The plage region is located 200 '' east of the flare arcade. The plage region has a small transient coronal hole. The transient coronal hole is strongly affected by an X-class flare, and upflows are observed at its boundary. Multi-wavelength spectral observations allow us to determine velocities from the Doppler shifts at different temperatures. Strong upflows along with stationary plasma have been observed in the Fe XV line 284.2 angstrom (log T/K = 6.3) in the plage region. The strong upflows reach almost 150 km s(-1), which was estimated by a two-component Gaussian fitting. On the other hand, at a lower corona/transition region temperature (He II, 256.3 angstrom, log T/K = 4.9), very weak upflows, almost stationary, have been observed. We find that these upflow velocities clearly depend on the temperature with the hottest line, Fe XV, showing the fastest upflow velocity and the second-highest line, Fe XIV, showing the second-highest upflow velocity (130 km s-1). All velocities are below the sound speed. The trend of the upflow dependence on temperature dramatically changes at 1 MK. These results suggest that heating may have an important role for strong upflow.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 59 S845-S852, Nov, 2007 Peer-reviewedTo understand the physical mechanisms for activity and heating in the solar atmosphere, the magnetic coupling from the photosphere to the corona is an important piece of information from the Hinode observations, and therefore precise positional alignment is required among the data acquired by different telescopes. The Hinode spacecraft and its onboard telescopes were developed to allow us to investigate magnetic coupling with co-alignment accuracy better than 1 ''. Using the Mercury transit observed on 2006 November 8 and co-alignment measurements regularly performed on a weekly basis, we have determined the information necessary for precise image co-alignment, and have confirmed that co-alignment better than 1 '' can be realized between Solar Optical Telescope (SOT) and X-Ray Telescope (XRT) with our baseline co-alignment method. This paper presents results from the calibration for precise co-alignment of CCD images from SOT and XRT.
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JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, 55(637) 57-64, 2007The solar observation satellite "SOLAR-B," which is being developed under the joint cooperation of JAXA and NAOJ with the U.S.A. (NASA) and the U.K. (PPARC), will be launched in summer 2006. SOLAR-B requires very high pointing stability for its three telescopes. In particular, the Solar Optical Telescope (SOT), which has the highest resolution and narrowest field of view among these telescopes, requires 0.06 [arcsec]3σ of short-term (10[s]) stability to meet the observation demands. However, it is very difficult to achieve such levels of stability by only using the satellite attitude control system due to disturbance from the observation equipment. Therefore, we propose using the Correlation Tracker and tip-tilt Mirror package (CTM), which stabilizes the sun observation image. CTM consists of a correlation tracker and a piezo-based tip-tilt mirror with servo control electronics. This paper describes the mechanism and the control and determination methods of the control gain of CTM as well as the results of experiments conducted to clarify its capability.
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The discovery of diffuse X-ray emission in NGC 2024, one of the nearest massive star-forming regionsASTROPHYSICAL JOURNAL, 649(2) L123-L128, Oct, 2006 Peer-reviewedWe analyzed deep 75 ks Chandra ACIS-I data of NGC 2024 with the aim of searching for diffuse X-ray emission in this most nearby (415 pc) of massive star-forming regions. After removing point sources, extended emission was detected in the central circular region with a radius of 0.5 pc, and it is spatially associated with this young massive stellar cluster. Its X-ray spectrum exhibits a very hard continuum (kT > 8 keV) and shows signs of having a He-like Fe K alpha line with a 0.5-7 keV absorption-corrected luminosity of 2 x 10(31) ergs s(-1). Undetected faint point sources, estimated from the luminosity function of the detected sources, contribute less than 10% to this emission. Hence, the emission is truly diffuse in nature. Because of the proximity of NGC 2024 and the long exposure, this discovery is one of the strongest pieces of evidence in support of the existence of diffuse X-ray emission in massive star-forming regions.
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Astrophysical Journal, 638(2 I) 860-877, Feb 20, 2006 Peer-reviewedChandra ACIS-I data of the molecular cloud and H n region complex NGC 6334 were analyzed. The hard X-ray clumps detected with ASCA (Sekimoto and coworkers) were resolved into 792 point sources. After removing the point sources, an extended X-ray emission component was detected over a 5 × 9 pc2 region, with the 0.5-8 keV absorption-corrected luminosity of 2 × 10 33 ergs s-1. The contribution from faint point sources to this extended emission was estimated as at most ∼20%, suggesting that most of the emission is diffuse in nature. The X-ray spectrum of the diffuse emission was observed to vary from place to place. In tenuous molecular cloud regions with hydrogen column density of (0.5-1) × 1022 cm-2, the spectrum can be represented by a thermal plasma model with temperatures of several keV. The spectrum in dense cloud cores exhibits harder continuum, together with higher absorption of more than ∼3 × 1022 cm-2. In some of such highly obscured regions, the spectra show extremely hard continua equivalent to a photon index of ∼1, and favor a nonthermal interpretation. These results are discussed in the context of thermal and nonthermal emission, both powered by fast stellar winds from embedded young early-type stars through shock transitions. © 2006. The American Astronomical Society. All rights reserved.
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Solar-B Mission and the Forefront of Solar Physics, Proceedings, 325 15-25, 2004The Soft X-ray Telescope (XRT) aboard Solar-B is a grazing incidence X-ray telescope equipped with 2k x 2k CCD. XRT has I arcsec resolution with wide field-of-view of 34 x 34 arcmin. It is sensitive to < 1 MK to 30 MK, allowing us to obtain TRACE-like low temperature images as well. Co-alignment with SOT and EIS is realized through the XRT visible light telescope and with temperature overlap with EIS. Spacecraft mission data processor (MDP) controls XRT through the sequence tables with versatile autonomous functions such as exposure control, region-of-interest tracking, flare detection and flare location identification. Data are compressed either with DPCM or JPEG, depending on the purpose. This results in higher cadence and/or wider field-of-view for given telemetry bandwidth. With focus adjust mechanism, higher resolution of Gaussian focus may be available on-axis.
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OPTICAL, INFRARED, AND MILLIMETER SPACE TELESCOPES, PTS 1-3, 5487 1189-1198, 2004 Peer-reviewedWe present scientific as well as engineering overview of the X-Ray Telescope (XRT) aboard the Japanese Solar-B mission to be launched in 2006, with emphasis on the focal plane CCD camera that employs a 2k x 2k back-thinned CCD. Characterization activities for the flight CCD camera made at the National Astronomical Observatory of Japan (NAOJ) are discussed in detail with some of the results presented.
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Monthly Notices of the Royal Astronomical Society, 328(1) 112-126, Nov 21, 2001 Peer-reviewedExtremely strong ionized Fe emission lines, with equivalent widths reaching ∼4000 eV, were discovered by ASCA from a few Galactic compact objects, including AX J2315-0592, RX J1802.1 + 1804 and AX J1842.8-0423. These objects are thought to be binary systems containing magnetized white dwarfs (WDs). A possible interpretation of the strong Fe K line is the line-photon collimation in the WD accretion column, as a result of resonance scattering of line photons. The collimation occurs when the accretion column has a flat shape, and the effect is augmented by the vertical velocity gradient, which reduces the resonant trapping of resonant photons along the magnetic field lines. This effect was quantitatively confirmed with Monte Carlo simulations. Furthermore, with ASCA observations of the polar V834 Centauri, this collimation effect was clearly detected as a rotational modulation of the equivalent width of the Fe K emission line. The extremely strong emission lines mentioned above can be explained consistently by our interpretation. Combining this effect with other X-ray information, the geometry and plasma parameters in the accretion column were determined.
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X-RAY ASTRONOMY, 599 959-962, 2001 Peer-reviewedThe Galactic ridge X-ray emission (GRXE) is an enhanced X-ray emission along the Galactic plane, whose origin still remains unknown. The GRXE was studied for the first time in the energy band of 0.5-10 keV with a spatial resolution of 3' by the ASCA Galactic plane survey which covers the spatial area of |l| less than or similar to 45degrees and |b| less than or similar to 0.4degrees almost uniformly. We determined the large scale distribution of the GRXE after eliminating discrete X-ray sources with a flux above 10(-12.5) ergs cm(-2) s(-1) and revealed that the volume emissivity of the GRXE is highly concentrated within the 4 kpc arm. We resolved 163 discrete X-ray sources by imaging analysis and obtained the LogN-LogS relations of those sources. In the hard (2-10 keV) band, the slope of the LogN-LogS relation is significantly smaller than 1. Considering a scale height of the Galactic plane covered by the ASCA Galactic plane survey, we conclude that the slope of the LogN-LogS relation represents that the spatial distribution of the sources has a scale height as small as 10 pc, that the sources are distributed in arm-like structures, and/or that the relation reflects the luminosity function rather than the spatial distribution. We analyzed small-scale spatial intensity fluctuation of the GRXE after subtracting the large scale variations and the contributions of resolved discrete sources. The residual small-scale fluctuation is found to remain significantly over the photon-counting Poisson fluctuation. However, in the 2-10 keV band, the amplitude can be explained by the fluctuation of the cosmic X-ray background coming through the Galactic interstellar medium. From this, we can obtain a strong constraint to a flux and a number density of discrete sources if we are to explain the GRXE with a sum of discrete sources; more than 10(7) sources with the luminosity smaller than 10(31) ergs s(-1) must exist in the Galaxy. This source number density is larger by three orders of magnitude than that of CVs in the solar neighborhood, which would be a plausible candidate for the discrete source origin. Thus, We conclude that the diffuse emission origin should be much more probable even if it has large problems.
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ASTROPHYSICAL JOURNAL, 534(2) L181-L184, May, 2000 Peer-reviewedA new pulsating X-ray source, AX J183220-0840, with a 1549.1 s period was discovered at R.A. = 18(h)32(m)20(s) and decl, = -8 degrees 40'30 " (J2000, with an uncertainty of 0'.6) during an ASCA observation on the Galactic plane. The source was observed two times, in 1997 and in 1999. A phase-averaged X-ray flux of 1.1 x 10(-11) ergs cm(-2) s(-1) and a pulsation period of 1549.1 +/- 0.4 s were consistently obtained from these two observations. The X-ray spectrum was represented by a flat, absorbed power law with a photon index of Gamma similar or equal to 0.8 and an absorption column density of N-H similar or equal to 1.3 x 10(22) cm(-2). Also, a signature of iron K-shell line emission with a centroid of 6.7 keV and an equivalent width of approximately 450 eV was detected. From the pulsation period and the iron-line feature, AX J183220-0840 is likely to be a magnetic white dwarf binary with a complexly absorbed thermal spectrum with a temperature of about 10 keV.
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BROAD BAND X-RAY SPECTRA OF COSMIC SOURCES, 25(3-4) 589-592, 2000 Peer-reviewedAn X-ray study was made to examine whether some part of the soft X-ray background is coming from hot gas halo that might be associated with the Local Group. For this purpose, four consecutive pointings were made with ASCA onto a general sky region in between M31 and M33, which is thought to be close to the direction of the Local Group Center. After removing point sources with 2-10 keV fluxes exceeding 2 x 10(-13) erg s(-1) cm(-2), the X-ray background brightness in this direction was quantified in terms of two (steep and fiat) power-law components. By comparing the soft-component brightness with that in another blank sky region near the equatorial pole, any excess soft X-ray background coming from this M31/M33 region was determined to be less than or equal to 1.27 x 10(-8) erg s(-1) cm(-2) str(-1). Assuming a Raymond-Smith type spectrum of temperature 0.3-1.2 keV and a beta-model density distribution for the X-ray halo, the central plasma density No and core radius R-c for the beta model was constrained as [N-0/10(-3) cm(-3)](2) [R-c/100 kpc] less than or equal to 5.80x10(-3). The implied plasma column density is too low to cause any noticeable quardrupole anisotropy in the cosmic microwave backbround. (C) 2000 COSPAR. Published by Elsevier Science Ltd.
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IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 46(3) 371-376, Jun, 1999 Peer-reviewedASTRO-E Hard X-ray Detector (HXD) is characterized by well-type phoswich counters[1] in a compound-eye configuration which reduce the detector background to lower level than any other past hard X-ray mission. When operating in Low Earth Orbit, the expected background of the HXD is an order of 10(-5) counts/s/kev/cm(2), mainly caused from the radioactivity induced within the detector materials by geomagnetically trapped protons. Results are presented from measurements of induced radioactivity in two phoswich scintillators, GSO (Gd2SiO5:Ce 0.5% mol) and EGO (Bi4Ge3O12), irradiated by mono-energetic protons at an accelerator facility. Radiation transport computer codes are used to build the detector response functions for emissions from decays of spallation products. Based on the comparison between experimental and simulation results, the activation background level of HXD in the orbit is estimated.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 51(1) 39-44, Feb, 1999 Peer-reviewedA new transient X-ray source, AX J1842.8-0423, was discovered with ASCA in 1996 October in the Scutum arm region. The source exhibited an absorption-corrected 2-10 keV flux of 5.2 x 10(-12) erg s(-1) cm(-2) with insignificant intensity variability. The continuous spectrum is approximated by a power-law of photon index 2.9, absorbed by a hydrogen column of NH similar to 5 X 10(22) Cm-2 The spectrum also exhibits the Fe-K emission line with an extremely large equivalent width of similar to 4000 eV, of which the centroid energy is similar to 6.8 keV. The overall spectrum can be reproduced by a thin-thermal plasma-emission model having a temperature of similar to 5.1 keV, on the condition that the heavy-element abundance is allowed to increase to 3.0(-0.9)(+4.3) solar abundance. The source was undetectable in a previous observation in 1993 October, as well as in a subsequent observation in 1996 April. The overall source behavior is thus quite peculiar, but may be explained in terms of a close binary involving a magnetized white dwarf viewed from pole-on inclination, where the unusually strong Fe-K line may be the result of resonant scattering of line photons.
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IEEE Nuclear Science Symposium and Medical Imaging Conference, 1 227-232, 1999ASTRO-E Hard X-ray Detector (HXD) is characterized by well-type phoswich counters in a compound-eye configuration which reduce the X-ray and non X-ray background to lower level than any other past hard X-ray missions. When operating in Low Earth Orbit, the expected background of the HXD is an order of 10-5[counts/s/keV/cm2], mainly caused from the radioactivity induced within the detector materials by nuclear interactions with geomagnetically trapped protons. Results are presented from measurements of induced radioactivity in two phoswich scintillators, GSO and BGO, irradiated by mono-energetic protons at an accelerator facility. Radiation transport computer codes are used to build the detector response functions against emissions from decays of spallation products. Based on the comparison of experimental and simulation results, the activation background level of HXD in the orbit is estimated.
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ASTRONOMISCHE NACHRICHTEN, 320(4-5) 377-377, 1999 Peer-reviewed
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 49(3) L7-L11, Jun, 1997 Peer-reviewedWe report on the ASCA results of a featureless X-ray spectrum from RX J1713.7-3946, a new shell-like SNR discovered with the ROSAT all-sky survey. The northwest part of RX J1713.7-3946 was in the field of the ASCA Galactic Plane Survey Project, and was found to exhibit a shell-like structure. The spectrum, however, shows neither line emission nor any signature of a thermal origin. Instead, a power-law model with a photon index of 2.4-2.5 gives a reasonable fit to the spectrum, suggesting a non-thermal origin. Together with the similarity to SN 1006, we propose that RX J1713.7-3946 is the second example, after SN 1006, of synchrotron X-ray radiation from a shell of SNRs. Since the synchrotron X-rays suggest the existence of extremely high energy charged particles in the SNR shell, our discovery should have a strong impact on the origin of cosmic X-rays.
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Astrophysical Journal, 491(2) 638-652, 1997 Peer-reviewedX-ray spectra of the Galactic ridge emission in the Scutum arm region have been obtained with ASCA GIS and SIS in the energy range 0.7-10 keV. The observed spectra are basically of thermal emission from thin hot plasmas, and individual K emission lines from helium-like Mg, Si, S, and Fe ions are confirmed in both the GIS and SIS spectra. This means that the Galactic ridge X-ray emission cannot be explained by a single-temperature ionization-equilibrium plasma model. It cannot, however, be reproduced even if a nonequilibrium ionization model is introduced thus multiple plasma components are required. The GIS spectra are fairly well fitted by a double-temperature nonequilibrium ionization plasma model with temperatures of kT ∼ 0.8 keV and kT ∼7 keV. The softer component is found to be in an extremely low ionization state, with net ∼ 109 cm-3 s, while the harder component is in a relatively high ionization state, though not yet in a full equilibrium. The GRXE properties obtained with the GIS are carefully reexamined by the highly resolved spectral-line features with the SIS. The soft and hard components are absorbed by equivalent hydrogen columns of 0.7 × 1022 cm-2 and 4.6 × 1022 cm-2, respectively. The surface brightness of the soft and hard components at b ∼ 0° are estimated to be 1.9 × 10-6 and 5.3 × 10-7 ergs cm-2 s-1 sr-1 respectively, both in the 0.5-10 keV band. The surface brightness of the softer component extends toward significantly higher (∼2°) Galactic latitudes than the harder component, although their actual scale heights may be similar at ∼100 pc if the differences in their observable depths are taken into account. Spectral properties of the two components are seen to depend on the latitude the most noticeable effect is a rapid decrease in the Fe K line equivalent width seen in the hard component. Attempts are made to interpret the two components in terms of diffuse hot plasmas filling the interstellar space. © 1997. The American Astronomical Society. All rights reserved.
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ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES, 120(4) C645-C648, Dec, 1996 Peer-reviewedThe Hard X-ray Detector (HXD) is one of three instruments on the fifth Japanese X-ray astronomy satellite, ASTRO-E, scheduled for launch in 2000. The HXD consists of a 4x4 = 16 modular assembly of identical counters, each consisting of a combination of YAP(or GSO)/BGO well-type phoswich counters and silicon PIN diodes. The field of view of the detector for high energy photons is restricted to 4 degrees x 4 degrees by active collimators made of BGO and the fov for low energy photons is restricted to 0.5 degrees x 0.5 degrees by the fine passive collimators made of phosphor bronze. The detector is characterized by a low background reaching severalx10(-6) c/s/cm(2)/keV. Combined with the other two instruments for soft X-ray observations (0.5-12 keV), the ASTRO-E mission will cover the entire range of soft and hard X-rays with the highest sensitivity ever achieved. Furthermore, thick EGO counters which surround the 4x4 matrix of well-type phoswich counters act as a gamma-ray burst detector in the energy band of 100-2000 keV.
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1995 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE RECORD, VOLS 1-3, 224-228, 1996 Peer-reviewed
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Proceedings of SPIE - The International Society for Optical Engineering, 2806 314-328, 1996 Peer-reviewed
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Publications of the Astronomical Society of Japan, 48(2) L15-L20, 1996 Peer-reviewedWe report on the ASCA results of hard X-ray imaging and spectroscopic observations of the galactic ridge (the Scutum arm region). The bulk of X-rays in the field of view could not be explained by an integrated emission of resolved sources, indicating that most of the galactic-ridge X-rays are due to a diffuse thin hot plasma. The X-ray luminosity of discrete sources contributing to the galactic-ridge emission was estimated to be less than -2x1033 erg s-1 in the 2-10 keV energy band. Emission lines from helium-like Si, S, and Fe ions were confirmed in the spectra, which means that the galactic ridge X-ray emission can not be explained by a single temperature ionization equilibrium plasma model. We give some constraints on the origin of the galactic-ridge emission.
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Proceedings of SPIE - The International Society for Optical Engineering, 2518 2-12, 1995The fourth Japanese x-ray astronomy satellite, ASCA, carries two imaging gas scintillation proportional counters (GIS) on its focal plane. Extensive ground calibration has established its position resolution to be 0.5 mm and FWHM energy resolution to be 8.0% both at 6 keV. When combined with the x-ray telescope, a sensitivity range becomes 0.7 - 10 keV. These properties have been confirmed through in-orbit calibrations. The in-orbit background of the GIS has been confirmed to be as low as (5 - 7) × 10 -4 c s -1cm -2keV -1 over the 1 - 10 keV range. The long-term detector gain is stable within a few % for two years. Gain dependence on the position and temperature has been calibrated down to 1%. The overall energy response is calibrated very accurately. Thus the GIS is working as an all-round cosmic x-ray detector.
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray, Dec 13, 2020
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray, Dec 13, 2020
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Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray, 10699, Jul 6, 2018© 2018 SPIE. The ASTRO-H mission was designed and developed through an international collaboration of JAXA, NASA, ESA, and the CSA. It was successfully launched on February 17, 2016, and then named Hitomi. During the in-orbit verification phase, the on-board observational instruments functioned as expected. The intricate coolant and refrigeration systems for soft X-ray spectrometer (SXS, a quantum micro-calorimeter) and soft X-ray imager (SXI, an X-ray CCD) also functioned as expected. However, on March 26, 2016, operations were prematurely terminated by a series of abnormal events and mishaps triggered by the attitude control system. These errors led to a fatal event: the loss of the solar panels on the Hitomi mission. The X-ray Astronomy Recovery Mission (or, XARM) is proposed to regain the key scientific advances anticipated by the international collaboration behind Hitomi. XARM will recover this science in the shortest time possible by focusing on one of the main science goals of Hitomi,"Resolving astrophysical problems by precise high-resolution X-ray spectroscopy".1 This decision was reached after evaluating the performance of the instruments aboard Hitomi and the mission's initial scientific results, and considering the landscape of planned international X-ray astrophysics missions in 2020's and 2030's. Hitomi opened the door to high-resolution spectroscopy in the X-ray universe. It revealed a number of discrepancies between new observational results and prior theoretical predictions. Yet, the resolution pioneered by Hitomi is also the key to answering these and other fundamental questions. The high spectral resolution realized by XARM will not offer mere refinements; rather, it will enable qualitative leaps in astrophysics and plasma physics. XARM has therefore been given a broad scientific charge: "Revealing material circulation and energy transfer in cosmic plasmas and elucidating evolution of cosmic structures and objects". To fulfill this charge, four categories of science objectives that were defined for Hitomi will also be pursued by XARM; these include (1) Structure formation of the Universe and evolution of clusters of galaxies; (2) Circulation history of baryonic matters in the Universe; (3) Transport and circulation of energy in the Universe; (4) New science with unprecedented high resolution X-ray spectroscopy. In order to achieve these scientific objectives, XARM will carry a 6 × 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly, and an aligned X-ray CCD camera covering the same energy band and a wider field of view. This paper introduces the science objectives, mission concept, and observing plan of XARM.
Major Presentations
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Oct 19, 2023, The Japan Society for Aeronautical and Space SciencesThis paper shows the system design and development status of the data handling system, ISC(DH), for the Martian Moons eXploration (MMX) mission. ISC(DH) consists of SMU (Spacecraft Management Unit), MDP (Mission Data Processor) and PDCU (Power Distribution Control Unit). System overviews and configuration are described.
Research Projects
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, 2007 - 2009
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, 2004 - 2005
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, 2002 - 2004
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科学研究費助成事業, 日本学術振興会, 2002 - 2002
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, 2000 - 2001
