Subaru Telescope: current performances and future upgrade plans

Subaru Telescope has currently achieved the following performances. 1. Image Quality. (1) Subaru Telescope delivers a median image size, evaluated by equipped Auto Guider (AG) cameras, of 0.6-0.7 arcsec FWHM in the R and I-band at all the four foci; Prime (P), Cassegrain (Cs), and two Nasmyth (Ns). (2) The best image sizes obtained so far are 0.2 arcsecs FWHM without; AO in near-infrared (IR), less than 0.1 arcsec FWHM with AO, and 0.3 arcsec FWHM in optical and mid-IR wavelengths. (3) Stable Shack-Hartmann measurement enables one to keep the errors of Zernike coefficients to less than 0.2 mum which corresponds to similar to0.1 arcsec image size. 2. Tracking and Pointing. (1) Blind pointing accuracy is better than 1 arcsec RMS over most of the sky. (2) Tracking accuracy is better than 0.2 arcsec RMS in 10 minutes. (3) Guiding accuracy is between 0.08 and 0.18 arcsec RMS with 12-18th magnitude guide stars. 3. IR secondary mirror (M2). (1) Chopping performances: typical figures are at 3 Hz, 80% duty cycle with 30-60 arcsec chopping throw. (2) Tip-Tilt performances: Position stability is about 0.030 arcsec RMS for the effective closed-loop bandwidth less than 5 Hz. 4. Others. (1) The reflectivity of the primary mirror has been maintained at higher than 85 and 95% at 670 and 1300 nm wavelengths by regular cleaning with CO2 ice every two to three weeks. (2) The reflectivity of the blue-side image rotator (ImR) at Nasmyth-optical focus was improved after re-coating of mirrors.