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An overview of the current status of the 8.2 m Subaru Telescope constructed and operated at Mauna Kea, Hawaii, by the National Astronomical Observatory of Japan is presented. The basic design concept and the verified performance of the telescope system are described. Also given are the status of the instrument package offered to the astronomical community, the status of operation, and some of the future plans. The status of the telescope reported in a number of SPIE papers as of the summer of 2002 are incorporated with some updates included as of 2004 February. However, readers are encouraged to check the most updated status of the telescope through the home page, http://subarutelescope.org/index.html, and/or the direct contact with the observatory staff., Comment: 18 pages (17 pages in published version), 29 figures (GIF format), This is the version before the galley proof

A SX Phe-type pulsating variable KZ Hya (HD94033) was observed with CCD set attached to the 45-cm reflector at Asuncion Astronomical Observatory in Paraguay. In the present work, 12 maximum phases were covered. A new ephemeris has been obtained, and the result suggests a probable change of the pulsation period of KZ Hya.

After the initial coating of the 8.3-m primary mirror of the Subaru Telescope in November 1998, we have conducted the first re-aluminization in August 1999. The primary mirror washing fixture worked efficiently for stripping the old coating and for washing the surface. Dry process is still to be improved. Suite of secondary and tertiary mirrors are being tested at the telescope, two of which were coated in- house, one in silver for the infrared observations and the other in aluminum for the optical observations, respectively. Evaluation of the coating film is conducted in two methods. Using a portable microScan, the reflectivity and the BRDF numbers of the primary mirror is monitored. Reflectivity over a wide range of the wavelength is measured in the witness mirrors. The preliminary data shows reasonably good number for the telescope optics. The in-situ cleaning of the primary mirror with solid and gaseous CO2 sprinkle arms is operating once every month. Next step for the coating chamber commissioning is to improve the heating capacity for silver coating of the infrared secondary and tertiary mirrors, and the experiment for silver coating is going.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The CIAX system especially CIAX-3 increased observation efficiency for Cassegrain test instruments at the early phase of Subaru telescope test observation. In order to control this system effectively and automatically, a control software for the entire system of the CIAX was developed. The software design goals are (1) redundancy for robust system, (2) the safety of the instrument by interlocking, (3) maximum efficiency by automatic control and (4) easy user interface for operator. In this paper, we describe the software which has been being tested through the telescope and instrument commissioning phase.

The Cassegrain Instrument Automatic eXchanger (CIAX) system for the 8.2 meter Subaru Telescope moves instruments between the Cassegrain mounting flange and stand-by flanges without manual intervention. Observation efficiency improves not only because of quick exchanges, scheduled or emergency, but also because of increased flexibility in selecting an optimum instrument for weather conditions or observation goals. Reliable and safer instrument exchanges are achieved by the precision mechanical positioning system (less than 0.5 mm) and an automatic connector system for electrical cables, optical fibers and fluid lines. Instrument down time due to connector/cable failure by human error is eliminated. Interfaces to the telescope flange are standardized for all five Cassegrain instruments (approximately 2000 kgf each) currently in use or under preparation.

On-shop test erection has been carried out at the Hitachi Zosen factory in Osaka since 1996. The purpose of this on- shop erection is to check and adjust the sizes of parts, to minimize the assembling errors, to test the telescope drive and active support system of the primary mirror, and to review the processes of final assembling. The alt-azimuth Subaru telescope structure weighting 500 ton is supported by six hydrostatic oil-film pads and is driven successfully by direct drive. The additional test for the instrument rotator drives, cable wrappers, and other were also carried out. We report the preliminary results of the control efficiency.

We adopt the hierarchy structure for the telescope control system of the Subaru Telescope. The system is made up of a TSC, three TWSs, three DCMOMs, three MLPs, and many LCUs. All devices are connected through local network each other.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The rotational part of the enclosure of SUBARU telescope (Japan National Large Telescope, or JNLT) is under the fabrication in Canada, and on-site erection is scheduled to take place in May, 1994, with the expected completion in the third quarter of 1995. The enclosure is featured with various design consideration for a better seeing performance, a better wind buffet performance, and good operability and maintainability. This paper describes the major design consideration behind the final shape and function of the enclosure and the current status of its fabrication.

The Japanese National Large Telescope (JNLT) will use a thin meniscus mirror of 7.5 m diameter and 0.2 m thickness as a primary mirror. One of the biggest concerns is mirror deflection due to dome-inside wind loading, which varies with time not only in its pressure amplitude but also in its pressure profile on the mirror surface. To analyze such mirror deflection, a method combining modal analysis and random vibration analysis was introduced. From the rms mirror deflection obtained by this method, the image quality degradation is considered to be better than that budgeted as wind loading degradation. Information about the method and typical result of the analysis are presented.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An engineering prototype with a 62 cm thin meniscus mirror to investigate the practical problems of the JNLT active optics system has been constructed. The structure and the performance of the prototype and the basis for the control algorithms are described. The stiffness of the mirror and the purity of figure control for the correction of lower order Zernike modes were measured for this system. The results of experiments to control the surface figure of the mirror under varying elevation angle of the telescope or under external force load are reported. The thermal effects on this system were also evaluated.

The Japanese National Large Telescope (JNLT) requires mechanical performance of high tracking accuracy to achieve good image quality and a mechanical configuration to provide several kinds of focus modes. Under these requirements, a conceptual design for the JNLT mechanical structure has been performed. This paper presents the results of the conceptual design currently under consideration.

In recent years, it has become increasingly clear that the dome is often itself a major source of seeing degradation, due to its adverse thermal properties. In order to enable the Japanese National Large Telescope (JNLT) to attain the highest image quality as a ground-based telescope, 0.1″ r.m.s. on 80% light energy diameter basis is budgeted to the dome-induced seeing degradation as a design goal. Feasibility of this goal has been studied, using the latest design concept of the dome, in the following manner. Model the JNLT dome on the latest design plan for dynamic thermal analysis. Perform the dynamic thermal analysis to attain temperature distribution in the dome. Predict the seeing degradation induced by the dome using the thermal analysis result.