Dr. Yoshiharu Asaki Profile

Dr. Yoshiharu Asaki

at NAOJ

SPIE Involvement:

Author

Publications (9)

Proceedings Article | 29 August 2022 Paper

Assembling and integration of the ALMA hardware in the loop simulation environment

Tzu-Chiang Shen, Alejandro Saez, Rodrigo Cabezas, Mark Gallilee, José L. Ortíz, Carlos Boza, Yoshiharu Asaki, Claudio Follert, Martin Tourneboeuf, Soledad Fuica, Johnny Reveco, Ruben Soto, Jorge Ibsen, Norikazu Mizuno, Stuartt Corder

Proceedings Volume 12189, 121891C (2022) https://doi.org/10.1117/12.2629194

KEYWORDS: Antennas, Telescopes, Signal processing, Control systems, Data modeling, Observatories

Read Abstract +

Proceedings Article | 8 August 2016 Paper

ALMA long baseline phase calibration using phase referencing

Yoshiharu Asaki, Satoki Matsushita, Edward Fomalont, Stuartt Corder, Lars-Åke Nyman, William R. Dent, Neil Philips, Akihiko Hirota, Satoko Takahashi, Baltasar Vila-Vilaro, Bojan Nikolic, Todd Hunter, Anthony Remijan, Catherine Vlahakis

Proceedings Volume 9906, 99065U (2016) https://doi.org/10.1117/12.2232301

KEYWORDS: Telescopes, Troposphere, Calibration, Antennas, Spatial resolution, Phase interferometry, Interferometers, Switching, Atmospheric modeling, Astronomy

Read Abstract +

The Atacama Large Millimeter/submillimeter Array (ALMA) is the world's largest millimeter/submillimeter telescope and provides unprecedented sensitivities and spatial resolutions. To achieve the highest imaging capabilities, interferometric phase calibration for the long baselines is one of the most important subjects: The longer the baselines, the worse the phase stability becomes because of turbulent motions of the Earth's atmosphere, especially, the water vapor in the troposphere. To overcome this subject, ALMA adopts a phase correction scheme using a Water Vapor Radiometer (WVR) to estimate the amount of water vapor content along the antenna line of sight. An additional technique is phase referencing, in which a science target and a nearby calibrator are observed by turn by quickly changing the antenna pointing. We conducted feasibility studies of the hybrid technique with the WVR phase correction and the antenna Fast Switching (FS) phase referencing (WVR+FS phase correction) for the ALMA 16 km longest baselines in cases that (1) the same observing frequency both for a target and calibrator is used, and (2) higher and lower frequencies for a target and calibrator, respectively, with a typical switching cycle time of 20 s. It was found that the phase correction performance of the hybrid technique is promising where a nearby calibrator is located within roughly 3◦ from a science target, and that the phase correction with 20 s switching cycle time significantly improves the performance with the above separation angle criterion comparing to the 120 s switching cycle time. The currently trial phase calibration method shows the same performance independent of the observing frequencies. This result is especially important for the higher frequency observations because it becomes difficult to find a bright calibrator close to an arbitrary sky position. In the series of our experiments, it is also found that phase errors affecting the image quality come from not only the water vapor content in the lower troposphere but also a large structure of the atmosphere with a typical cell scale of a few tens of kilometers.

Proceedings Article | 27 July 2016 Paper

Atmospheric phase characteristics of the ALMA long baseline

Satoki Matsushita, Yoshiharu Asaki, Edward Fomalont, Denis Barkats, Stuartt Corder, Richard Hills, Ryohei Kawabe, Luke Maud, Koh-Ichiro Morita, Bojan Nikolic, Remo P. J. Tilanus, Catherine Vlahakis

Proceedings Volume 9906, 99064X (2016) https://doi.org/10.1117/12.2231846

KEYWORDS: Atmospheric corrections, Atmospheric sciences, Atmospheric corrections, Atmospheric sensing, Calibration, Antennas, Turbulence, Atmospheric modeling, Astronomy, Signal detection, Statistical analysis

Read Abstract +

Proceedings Article | 22 July 2014 Paper

Phase characteristics of the ALMA 3-km baseline data

Satoki Matsushita, Yoshiharu Asaki, Ryohei Kawabe, Ed Fomalont, Denis Barkats, Stuartt Corder

Proceedings Volume 9145, 91453I (2014) https://doi.org/10.1117/12.2056424

KEYWORDS: Antennas, Atmospheric corrections, Radiometry, Atmospheric sensing, Astronomy, Fast packet switching, Diamond, Turbulence, Switching, Calibration

Read Abstract +

Proceedings Article | 22 July 2014 Paper

ALMA fast switching phase calibration on long baselines

Yoshiharu Asaki, Satoki Matsushita, Ryohei Kawabe, Ed Fomalont, Denis Barkats, Stuartt Corder

Proceedings Volume 9145, 91454K (2014) https://doi.org/10.1117/12.2055824

KEYWORDS: Interferometers, Phase interferometry, Calibration, Switching, Fast packet switching, Antennas, Observatories, Radiometry, Astronomy, Telescopes

Read Abstract +

Proceedings Article | 17 September 2012 Paper

ACA phase calibration scheme with the ALMA water vapor radiometers

Yoshiharu Asaki, Satoki Matsushita, Koh-Ichiro Morita, Bojan Nikolic

Proceedings Volume 8444, 84443K (2012) https://doi.org/10.1117/12.925986

KEYWORDS: Antennas, Interferometry, Phase interferometry, Calibration, Interferometers, Radiometry, Phase measurement, Astronomy, Observatories, Data corrections

Read Abstract +

Proceedings Article | 12 October 2004 Paper

The VSOP-2 Project: a second-generation space-VLBI mission ranging to mm-wavelengths

Hisashi Hirabayashi, Yasuhiro Murata, Yoshiharu Asaki, Philip Edwards, Nanako Mochizuki, Michihiro Natori, Makoto Inoue, Tomofumi Umemoto, Seiji Kameno, Yusuke Kono, Masato Tsuboi, Takashi Kasuga

Proceedings Volume 5487, (2004) https://doi.org/10.1117/12.563417

KEYWORDS: Antennas, Space operations, Satellites, Spatial resolution, Receivers, Radio astronomy, Space telescopes, Aerospace engineering, Scattering, Interferometry

Read Abstract +

Proceedings Article | 3 July 2000 Paper

HALCA: the radio telescope for the space VLBI mission

Y. Murata, Hisashi Hirabayashi, Hideyuki Kobayashi, H. Hirosawa, P. Edwards, Tsuneo Kii, Yoshiharu Asaki, K. Wajima, M. Inoue, T. Miyaji, K. Shibata, Kenta Fujisawa, R. Okayasu, Noriyuki Kawaguchi, S. Kameno

Proceedings Volume 4015, (2000) https://doi.org/10.1117/12.390413

KEYWORDS: Space telescopes, Antennas, Radio telescopes, Satellites, Optical correlators, Telescopes, Control systems, Sun, Magnetic sensors, Doppler effect

Read Abstract +

Proceedings Article | 3 July 2000 Paper

Novel method to compare tropospheric path delay fluctuations with 22-GHz water vapor line emissions

Yoshiharu Asaki, Hideyuki Kobayashi, Naoki Hagiwara, Masato Ishiguro

Proceedings Volume 4015, (2000) https://doi.org/10.1117/12.390456

KEYWORDS: Radiometry, Antennas, Satellites, Doppler effect, Observatories, Temperature metrology, Radio telescopes, Phase measurement, Interferometry, Radiometric corrections

Read Abstract +

Showing 5 of 9 publications

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years