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Volume 46, Issue 6
Special Issue on Next Generation Extremely Large Telescope: Thirty Meter Telescope (TMT) Project
Displaying 1-8 of 8 articles from this issue
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Special Issue on Next Generation Extremely Large Telescope: Thirty Meter Telescope (TMT) Project
Special Issue
Laser Review
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Masanori IYE2018 Volume 46 Issue 6 Pages 292-
Published: 2018
Released on J-STAGE: December 18, 2020
JOURNAL FREE ACCESSA short history of the last four decades of the optical/infrared astronomy of Japan that led to the current Thirty Meter Telescope project is presented as a preface of the present series based some part on the personal experiences and perspective of the author.View full abstractDownload PDF (2876K) -
Tomonori USUDA2018 Volume 46 Issue 6 Pages 294-
Published: 2018
Released on J-STAGE: December 18, 2020
JOURNAL FREE ACCESSThe TMT is a project to build an extremely large 30-meter optical/infrared telescope under the collaboration of five partner countries including Japan, USA, Canada, China, and India. In 2014, an agreement was executed among the participating organizations to found TMT International Observatory (TIO) to construct TMT on Maunakea. The onsite construction was halted because the supreme court of Hawai'i ruled in favor of a claim that cited a problem in the approval process of the land use permit for the Maunakea Conservation District and remanded it in December 2015. Although this has caused delays to construction onsite, mass production of the telescope primary mirror, design works of the telescope subsystems including science instruments have proceeded according to plan in the partner countries. The land use permit was approved again in September 2017, TIO is preparing to start on-site construction at Maunakea in 2018.View full abstractDownload PDF (2876K) -
Yutaka EZAKI, Atsushi KATO, Jyunji TAKAGI, Noboru KAWAGUCHI2018 Volume 46 Issue 6 Pages 300-
Published: 2018
Released on J-STAGE: December 18, 2020
JOURNAL FREE ACCESSsegment handling system. The technical requirements for the STR system are very challenging on its performance and interface condition with telescope-mounted optics and observation instruments. The major challenging technical requirements include low flexure of mirror support structure, high seismic performance against large earthquake, and fast, safe and labor-saving segment exchange. To meet these technical requirements, Mitsubishi Electric Corporation (MELCO) has made a detailed design and technology development. In this paper, overview of major key technologies is introduced that is adopted for the TMT telescope structure in the detailed design and technology development, including recent prototyping of Pintle Seismic Isolation System. Key Words: Telescope Structure, Low Gravitational DeformationView full abstractDownload PDF (3050K) -
Hiroyuki MINAMIKAWA2018 Volume 46 Issue 6 Pages 305-
Published: 2018
Released on J-STAGE: December 18, 2020
JOURNAL FREE ACCESSModern large telescopes require large mirrors for collecting light from faint stars and galaxies. The mirrors must be machinable to form intricately curved smooth surfaces for telescope optics and must be stable enough under the varying environment. Several types of zero thermal expansion glass are most frequently used as the material for those mirrors. CLERCERAMTM-Z is one of such zero thermal expansion glass ceramics manufactured by OHARA Inc. and adopted for the primary mirror segments of TMT. The present article describes the development history, the manufacturing processes and various characteristics of CLEARCERAMTM-Z. Measurement methods and actual measured data of thermal expansion coefficient, processability, long term stability, and internal stress are presented to date, 200 blanks, out of 574 blanks needed, have been manufactured all meeting the specifications of TMT primary segments.View full abstractDownload PDF (789K) -
Akira MIYAKE2018 Volume 46 Issue 6 Pages 311-
Published: 2018
Released on J-STAGE: December 18, 2020
JOURNAL FREE ACCESSTMT primary mirror consists of hexagon shape (1.44 m in diagonal diameter and 45 mm in thickness) segment mirrors. This article describes the fabrication process developed for these segment mirrors. Stressed mirror polishing (SMP) method is adopted taking the advantages of its process speed and attained smoothness in higher spatial frequency figure. Segment substrate bending fixtures enables versatile aspheric polishing of various types of TMT segments by adjusting the bending force distribution. Mass production of segment polishing has started and 22 segments were successfully polished to comply with the specifications. Detailed studies for hexagonal cutting and mounting of the polished mirror onto the segment support assembly to complete segment mirror assemblies are under way.View full abstractDownload PDF (1656K) -
Ryuji SUZUKI, Yutaka HAYANO2018 Volume 46 Issue 6 Pages 316-
Published: 2018
Released on J-STAGE: December 18, 2020
JOURNAL FREE ACCESSThe adaptive optics application in ground-based astronomy enables diffraction-limited imaging performance by correcting the wavefront disturbed by the earth’s atmosphere using guide stars, wavefront sensors, and deformable mirrors. The sky coverage of adaptive optics has been greatly improved since the Laser Guide Star and Multi-Conjugate Adaptive Optics were introduced. High sensitivity and high resolution observation enabled by adaptive optics makes it an essential technology, especially for the extremely large telescopes that are currently under construction. Its superb image quality is expected to allow the measurement of the position a star to be accurate to one three hundred millionth of a degree, greatly complicating the expected performance and requirements of client instruments. This paper reviews the adaptive optics system and its client near-infrared instrument that is being developed for the Thirty Meter Telescope.View full abstractDownload PDF (1174K) -
Michitoshi YOSHIDA2018 Volume 46 Issue 6 Pages 321-
Published: 2018
Released on J-STAGE: December 18, 2020
JOURNAL FREE ACCESSThe Subaru telescope, which is operated by National Astronomical Observatory of Japan, is an 8.2 m optical-infrared telescope at the 4,200 m summit of Maunakea, Hawaii. Its wide-field observation capability and high angular resolution make the telescope unique and one of the most powerful devices in the world. In the TMT era, wide-field capability will be particularly critical and a key characteristic of Subaru and will complement TMT ’s ultra-high sensitivity.View full abstractDownload PDF (939K)
Regular Paper
Laser Original
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Yasuhiro OKAMURA, Ikuya NAGATOMI, Atsushi TAKADA2018 Volume 46 Issue 6 Pages 326-
Published: 2018
Released on J-STAGE: December 18, 2020
JOURNAL FREE ACCESSThis study aimed to build a numerical model of carrier extraction from dual-polarization phaseconjugated twin waves (DP-PCTWs) to investigate polarization dependence on the carrier extraction in a pump phase-locked loop for phase-sensitive optical amplifier repeaters. First, the numerical model was developed, and extracted carrier power of 40- Gbit/s DP-PCTWs with quadrature phase-shift keying format was calculated. Numerical results show the extracted carrier disappears when the PCTWs are circular polarization, and polarization dependence exists on the carrier extraction. Then, carrier extraction of a 10- Gbit/s DP-PCTW with binary phase-shift keying format was experimentally demonstrated. The extracted carrier power was found to be relatively low when the DP-PCTWs are circular polarization, and this trend agrees closely with the numerical results. These results show the reasonability of the numerical model and existence of polarization dependence on the carrier extraction from DP-PCTWs.View full abstractDownload PDF (820K)
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