Masashi Otsubo

Current performance and on-going improvements of the 8.2 m Subaru Telescope

An overview of the current status of the 8.2m 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.

Adaptive optics system for Cassegrain focus of Subaru 8.2-m telescope

The adaptive optics system for Subaru 8.2m telescope of the National Astronomical Observatory Japan has been developed for the Cassegrain ear-IR instruments, CIAO and IRCS. The system consists of a wavefront curvature sensor with 36 subaperture photon-counting avalanche photodiode modules and a bimorph deformable mirror with 36 electrodes. The expected Strehl ratio at K band exceeds 0.4 for objects that are located close enough to a bright guide star as faint as R equals 16 mag at the median seeing of 0.45 arcsec at Mauna Kea. The system will be in operation in 1999 as a natural guide star system, and will eventually be upgraded to a laser guide star system in cooperating an IR wavefront tilt sensor to provide nearly full sky. The construction of this common use system to Subaru telescope is now underway in our laboratory in Tokyo. Prior to starting the fabrication of this common use system, a full size prototype system was constructed and tested with the 1.6 m IR telescope at our observatory in Tokyo. This system has the identical optical design, deformable mirror, loop control computer to those for the Subaru system, while the wavefront sensing detectors were less-sensitive analog APDs. We succeeded in getting closed loop images of stars in K band with diffraction limited core. The Strehl ratio was around 0.5 and the factor of improvement was about 20 at K-band under the average seeing of 2 arcsec during the observation. The loop sped of the system was 2 K corrections per second.

HOLOGRAPHIC ATMOSPHERIC TURBULENCE SIMULATOR FOR TESTING ADAPTIVE OPTICS SYSTEMS

The basic principles, the manufacturing processes and the performance of a wavefront turbulence generator system that incorporates a computer generated hologram are described. This system was shown to be useful for evaluating in the laboratory the performance of the prototype adaptive optics system that was constructed for the 8 m Subaru telescop.

Subaru instrumentation plan and optical instruments

The overall updated plan for constructing 7 scientific instruments and 3 baseline programs for the 8 m Subaru telescope is shown. Somewhat detailed descriptions are given further for projects to develop large format CCDs, faint object camera and spectrograph (FOCAS), high dispersion spectrograph (HDS), Subaru prime focus camera (Suprime-Cam), and Cassegrain adaptive optics system (AO).

Subaru Adaptive Optics Program

The system overview and the current status of an adaptive optics system for the Cassegrain focus of Subaru 8.2 m telescope under construction atop Mauna Kea is presented. The system is composed of a wavefront curvature sensor with 36 elements photon-counting APD modules and a 36-element bimorph deformable mirror. We aim to get the Strehl ratio of greater than 0.6 at the K band (2.2 micron) using natural guide stars as wavefront reference under the average seeing condition (approximately 0.45 arcsec) at Mauna Kea. It is scheduled to be in operation in 1998. Expected performance, especially the sky coverage when employing natural guide stars are also presented. currently we are testing prototype system with basically identical specifications as those of the final system. We present here the optical system, deformable mirror, wavefront sensor, control system of the final system, and simple introduction and experimental results of the prototype system.