Dr. Hajime Ezawa Profile

Dr. Hajime Ezawa

at National Astronomical Observatory of Japan

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Author

Publications (16)

Proceedings Article | 28 August 2024 Presentation + Paper

Toward laboratory demonstration of terahertz intensity interferometry

Hiroshi Matsuo, Hajime Ezawa, Ayako Niwa, Tomohiro Koseki, Norio Okada

Proceedings Volume 13095, 130951L (2024) https://doi.org/10.1117/12.3021092

KEYWORDS: Astronomical interferometry, Quantum interferometry, Photodetectors, Telescopes, Sensors, Quantum receivers, Heterodyning, Quantum limits, Time metrology, Quantum noise

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Proceedings Article | 17 August 2024 Poster

Evaluation of 1.5 THz photon counting detectors for Antarctic terahertz intensity interferometry

Ayako Niwa, Hiroshi Matsuo, Hajime Ezawa, Tomohiro Koseki, Tomonori Tamura

Proceedings Volume PC13102, PC131021K (2024) https://doi.org/10.1117/12.3021254

Proceedings Article | 13 December 2020 Presentation

Technologies for space terahertz intensity interferometry

Hiroshi Matsuo, Hajime Ezawa, Hitoshi Kiuchi, Mareki Honma, Masahiro Ukibe, Go Fujii, Yasuhiro Murata, Makoto Hattori

Proceedings Volume 11453, 1145332 (2020) https://doi.org/10.1117/12.2562333

KEYWORDS: Terahertz technology, Interferometry, Photodetectors, Aerospace engineering, Astronomy, Synthetic apertures, Phase measurement, Sensors, Spatial resolution, Galactic astronomy

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Proceedings Article | 28 July 2010 Paper

Wind-induced pointing errors and surface deformation of a 10-m submillimeter antenna

Nobuharu Ukita, Hajime Ezawa, Sachiko Onodera, Masao Saito

Proceedings Volume 7733, 77331D (2010) https://doi.org/10.1117/12.857279

KEYWORDS: Antennas, Reflectors, Computer programming, Telescopes, Servomechanisms, Turbulence, Sensors, Motion measurement, Wind measurement, Reflector telescopes

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Proceedings Article | 22 July 2008 Paper

New achievements of ASTE: the Atacama Submillimeter Telescope Experiment

Hajime Ezawa, Kotaro Kohno, Ryohei Kawabe, Satoshi Yamamoto, Hirofumi Inoue, Hiroyuki Iwashita, Hiroshi Matsuo, Takeshi Okuda, Tai Oshima, Takeshi Sakai, Kunihiko Tanaka, Nobuyuki Yamaguchi, Grant Wilson, Min Yun, Itziar Aretxaga, David Hughes, Jason Austermann, Thushara Perera, Kimberly Scott, Leonardo Bronfman, Juan Cortes

Proceedings Volume 7012, 701208 (2008) https://doi.org/10.1117/12.789652

KEYWORDS: Telescopes, Receivers, Spectroscopy, Astronomy, Cameras, Submillimeter telescopes, Observatories, Bolometers, Single sideband modulation, Iterated function systems

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Proceedings Article | 10 July 2008 Paper

Site evaluations of the summit of Co. Chajnantor for infrared observations

Takashi Miyata, Kentaro Motohara, Shigeyuki Sako, Masuo Tanaka, Takeo Minezaki, Natsuko Mitani, Tsutomu Aoki, Takao Soyano, Toshihiko Tanabe, Kimiaki Kawara, Kotaro Kohno, Ken'ichi Tarusawa, Toshihiko Handa, Mamoru Doi, Yuzuru Yoshii, Hajime Ezawa, Leonardo Bronfman, Maria Ruiz

Proceedings Volume 7012, 701243 (2008) https://doi.org/10.1117/12.788264

KEYWORDS: Clouds, Astronomy, Observatories, Infrared radiation, Infrared astronomy, Telescopes, Satellites, Cameras, Mid-IR, Infrared cameras

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Proceedings Article | 8 October 2004 Paper

Design of wide-field submillimeter-wave camera using SIS photon detectors

Hiroshi Matsuo, Seiichiro Ariyoshi, Chiko Otani, Hajime Ezawa, Jun Kobayashi, Yuko Mori, Hirohisa Nagata, Hirohiko Shimizu, Mikio Fujiwara, Makoto Akiba, Iwao Hosako

Proceedings Volume 5498, (2004) https://doi.org/10.1117/12.552550

KEYWORDS: Sensors, Photodetectors, Bolometers, Sapphire, Cryogenics, Cameras, Superconductors, Antennas, Staring arrays, Electronics

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Proceedings Article | 28 September 2004 Paper

The Atacama Submillimeter Telescope Experiment (ASTE)

Hajime Ezawa, Ryohei Kawabe, Kotaro Kohno, Satoshi Yamamoto

Proceedings Volume 5489, (2004) https://doi.org/10.1117/12.551391

KEYWORDS: Telescopes, Receivers, Antennas, Submillimeter telescopes, Spectroscopy, Satellites, Astronomy, Control systems design, Control systems, Galactic astronomy

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Proceedings Article | 28 September 2004 Paper

Design and performance of the ALMA-J prototype antenna

Nobuharu Ukita, Masao Saito, Hajime Ezawa, Bungo Ikenoue, Hideharu Ishizaki, Hiroyuki Iwashita, Nobuyuki Yamaguchi, Takahiro Hayakawa

Proceedings Volume 5489, (2004) https://doi.org/10.1117/12.551523

KEYWORDS: Antennas, Computer programming, Reflectors, Holography, Observatories, Prototyping, Stars, Servomechanisms, Metrology, Telescopes

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The National Astronomical Observatory of Japan has constructed a prototype 12-m antenna of the Atacama Compact Array to evaluate its performance at the ALMA Test Facility in the NRAO VLA observatory in New Mexico, the United States. The antenna has a CFRP tube backup structure (BUS) with CFRP boards to support 205 machined Aluminum surface panels. Their accuracies were measured to be 5.9 m rms on average. A chemical treatment technique of the surface panels has successfully applied to scatter the solar radiation, which resulted in a subreflector temperature increase of about 25 degrees relative to ambient temperature during direct solar observations. Holography measurements and panel adjustments led to a final surface accuracy of 20 m rms, (weighted by 12dB edge taper), after three rounds of the panel adjustments. Based on a long term temperature monitoring of the BUS and thermal deformation FEM calculation, the BUS thermal deformation was estimated to be less than 3.1 m rms. We have employed gear drive mechanism both for a fast position switching capability and for smooth drive at low velocities. Servo errors measured with angle encoders were found to be less than 0.1 arcseconds rms at rotational velocities below 0.1 degrees s-1 and to increase to 0.7 arcseconds rms at the maximum speed of the 'on-the-fly' scan as a single dish, 0.5 deg s-1 induced by the irregularity of individual gear tooth profiles. Simultaneous measurements of the antenna motion with the angle encoders and seismic accelerometers mounted at the primary reflector mirror edges and at the subreflector showed the same amplitude and phase of oscillation, indicating that they are rigid, suggesting that it is possible to estimate where the antenna is actually pointing from the encoder readout. Continuous tracking measurements of Polaris during day and night have revealed a large pointing drift due to thermal distortion of the yoke structure. We have applied retrospective thermal corrections to tracking data for two hours, with a preliminary thermal deformation model of the yoke, and have found the tracking accuracy improved to be 0.1 - 0.3 arcseconds rms for a 15-munites period. The whole sky absolute pointing error under no wind and during night was measured to be 1.17 arcseconds rms. We need to make both an elaborated modeling of thermal deformation of the structure and systematic searches for significant correlation among pointing errors and metrology sensor outputs to achieve the stable tracking performance requested by ALMA.

Proceedings Article | 3 July 2000 Paper

Development of the reflector panel for the new 10-m millimeter/submillimeter telescope

Hajime Ezawa, Masato Ishiguro, Hiroshi Matsuo, Keizo Miyawaki, Naohisa Satou, Nobuharu Ukita

Proceedings Volume 4015, (2000) https://doi.org/10.1117/12.390444

KEYWORDS: Reflectors, Telescopes, Reflector telescopes, Scattering, Antennas, Reflectivity, Aluminum, Extremely high frequency, Light scattering, Observatories

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Proceedings Article | 3 July 2000 Paper

NRO 10-m submillimeter telescope

Nobuharu Ukita, Ryohei Kawabe, Masato Ishiguro, Hajime Ezawa, Yutaro Sekimoto, Tatsuo Hasegawa, Satoshi Yamamoto, Keizo Miyawaki, Soichi Matsumoto

Proceedings Volume 4015, (2000) https://doi.org/10.1117/12.390409

KEYWORDS: Antennas, Telescopes, Computer programming, Submillimeter telescopes, Temperature metrology, Control systems design, Receivers, Observatories, Optical telescopes, Thermal effects

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Proceedings Article | 10 November 1998 Paper

Electronic system for the Astro-E Hard X-ray Detector

Tadayuki Takahashi, Masaharu Nomachi, Yasushi Fukazawa, Makoto Tashiro, Hajime Ezawa, M. Hamaya, M. Horii, Naoki Isobe, Naoko Iyomoto, Jun Kataoka, Tuneyoshi Kamae, Ginga Kawaguti, Hidetoshi Kubo, S. Kubo, Aya Kubota, Motohide Kokubun, Kazuo Makishima, Keiichi Matsuzaki, Yukari Matsumoto, Tsunefumi Mizuno, Kunishiro Mori, N. Morita, Toshio Murakami, Kazuhiro Nakazawa, H. Obayashi, I. Odagi, Tomohisa Onishi, N. Ota, Hideki Ozawa, Kunihiko Sato, Masahiko Sugiho, Mutsumi Sugizaki, Koji Taguchi, Tadahisa Tamura, Y. Tanaka, Chiharu Tanihata, Yukikatsu Terada, Yasuhiro Uchiyama, Kazutaka Yamaoka, Atsumasa Yoshida

Proceedings Volume 3445, (1998) https://doi.org/10.1117/12.330273

KEYWORDS: Amplifiers, Sensors, Analog electronics, PIN photodiodes, Scintillators, Signal processing, Hard x-rays, Satellites, Genetical swarm optimization, X-rays

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Proceedings Article | 7 July 1997 Paper

Integration of the readout electronics for the Astro-E hard x-ray detector

Hideki Ozawa, Jun Kataoka, Toshio Murakami, Mutsumi Sugizaki, Tadayuki Takahashi, Kazutaka Yamaoka, Hajime Ezawa, Yasushi Fukazawa, Tuneyoshi Kamae, Kazuo Makishima, Tsunefumi Mizuno, Kazuhiro Nakazawa, Satoko Osone, Hirokazu Ikeda, Kiwamu Tsukada, Hidetoshi Kubo

Proceedings Volume 3115, (1997) https://doi.org/10.1117/12.277690

KEYWORDS: PIN photodiodes, Sensors, Analog electronics, Satellites, Electronics, Genetical swarm optimization, Amplifiers, Hard x-rays, Silicon, X-rays

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Proceedings Article | 18 October 1996 Paper

Astro-E hard x-ray detector

Tuneyoshi Kamae, Hajime Ezawa, Yasushi Fukazawa, Masaharu Hirayama, Eriko Idesawa, Naoko Iyomoto, Hidehiro Kaneda, Ginga Kawaguti, Motohide Kokubun, Hidetoshi Kubo, Aya Kubota, Kyoko Matsushita, Keiichi Matsuzaki, Kazuo Makishima, Tsunefumi Mizuno, Kazuhiro Nakazawa, Satoko Osone, H. Obayashi, Yoshitaka Saito, Takayuki Tamura, Masaaki Tanaka, Makoto Tashiro, Jun Kataoka, Toshio Murakami, Naomi Ota, Hideki Ozawa, Mutsumi Sugizaki, Kyoko Takizawa, Tadayuki Takahashi, Kazutaka Yamaoka, Atsumasa Yoshida, Hirokazu Ikeda, Kiwamu Tsukada, Masaharu Nomachi

Proceedings Volume 2806, (1996) https://doi.org/10.1117/12.253993

KEYWORDS: Genetical swarm optimization, Sensors, PIN photodiodes, Scintillators, Hard x-rays, Silicon, Collimators, X-rays, Analog electronics, Diodes

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Proceedings Article | 1 September 1995 Paper

In-orbit performance of the GIS instrument on board ASCA (ASTRO-D)

Makoto Tashiro, Kazuo Makishima, Hajime Ezawa, Yasushi Fukazawa, Eriko Idesawa, Yoshitaka Ishisaki, Naoko Iyomoto, Tuneyoshi Kamae, Hidehiro Kaneda, Kyoko Matsushita, Keiichi Matsuzaki, Yoshitaka Saito, Yutaro Sekimoto, Takayuki Tamura, Masaharu Hirayama, Manabu Ishida, Hidetoshi Kubo, Kyoko Okada, Tadayuki Takahashi, Yoshihiro Ueda, Koichi Kikuchi, Takaya Ohashi, Noriko Yamasaki, Yoshiki Kohmura, Yasushi Ikebe, Tatehiro Mihara, Takeshi Tsuru, K. Ebisawa, Shuichi Gunji

Proceedings Volume 2518, (1995) https://doi.org/10.1117/12.218370

KEYWORDS: Geographic information systems, Calibration, X-rays, Sensors, X-ray detectors, Lithium, X-ray astronomy, X-ray imaging, Electronics, Scintillation

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Proceedings Article | 1 September 1995 Paper

Development of the hard x-ray detector for the ASTRO-E mission

Hidehiro Kaneda, Hajime Ezawa, Masaharu Hirayama, Tuneyoshi Kamae, Hidetoshi Kubo, Keiichi Matsuzaki, Kazuo Makishima, Takanori Ohtsuka, Yoshitaka Saito, Yutaro Sekimoto, Tadayuki Takahashi, Takayuki Tamura, Makoto Tashiro, Naohiko Tsuchida, Toshio Murakami, Mutsumi Sugizaki, Hirokazu Ikeda, Kiwamu Tsukada, Masaharu Nomachi, Shuichi Gunji, Satoshi Miyazaki, Tadahisa Tamura, Noriko Yamasaki, Atsumasa Yoshida

Proceedings Volume 2518, (1995) https://doi.org/10.1117/12.218407

KEYWORDS: PIN photodiodes, Sensors, Scintillators, Silicon, Hard x-rays, X-rays, Crystals, Detector development, Diodes, Signal processing

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Showing 5 of 16 publications

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