MIRA status report: recent progress of MIRA-I.2 and future plans

摘要

MIRA-I.2 is a 30m-baseline two-aperture stellar interferometer working in the visible band (from 600 to 1000 nm). In this article are presented the up-to-date progress and performance of MIRA-I.2 as well as some ongoing and future plans. The fast and coarse delay lines are now both evacuated, and the maximum OPD (optical path delay) compensations are about 16 m and 4 m long, respectively, for the fast and coarse delay lines. The current limiting magnitude is about I=4.5mag, and stars within the declination range from +8 to +51 degree is possible to be observed longer than one hour at the elevation angle of 60 degrees and higher. The OPD of the coarse delay line is modulated by about 128 micrometers around the expected fringe center with the use of PZT, and 187 fringe packets are scanned during one shot (= 60 seconds duration) to yield the mean visibility of about 10 % internal errors for each shot. The thermal environment of the building that houses the delay lines and interference optics has been improved very much, and readjustments of the optical alignment are not necessary for a whole night. The assembly and the setup of the optics to be used for the fringe tracking experiment are nearly completed.