MIRA-I.2: recent progress

摘要

After the first fringe detection with MIRA-I.2 30m baseline for Vega in June 2002, fringes for Vega and Deneb has been confirmed and then construction continued. Fast delay line has been evacuated and extended from 4m to 8m long. Coarse delay line has been extended from 2m to 4m. Baseline vector has been determined with 0.1mm accuracy. Aluminized mirrors have been changed to gold-plated ones, and the total throughput has become four times larger than before at the 600nm-1000nm band. The photon rate is 150 per ms for a 2 mag (I-band) star and the present limiting magnitude is better than 3mag. A delay modulation PZT has been set to push a cat's eye retro-reflector. Observations have been made for 6 stars with successful fringe packet detections. Visibility stability has been being studied with artificial light sources and Vega, which preliminary results are better than a few percent. A three-color system between 600-1000nm is now on the half way of installation. Gregorian cat's eye retro-reflectors with fine delay line PZTs and fringe tracking control software is planned to be installed.