System design of the compact IR space imaging system MIRIS

Multi-purpose Infra-Red Imaging System (MIRIS) is the main payload of the Korea Science and Technology Satellite-3 (STSAT-3), which is being developed by Korea Astronomy & Space Science Institute (KASI). MIRIS is a small space telescope mainly for astronomical survey observations in the near infrared wavelengths of 0.9~2 μm. A compact wide field (3.67 x 3.67 degree) optical design has been studied using a 256 x 256 Teledyne PICNIC FPA IR sensor with a pixel scale of 51.6 arcsec. The passive cooling technique is applied to maintain telescope temperature below 200 K with a cold shutter in the filter wheel for accurate dark calibration and to reach required sensitivity, and a micro stirling cooler is employed to cool down the IR detector array below 100K in a cold box. The science mission of the MIRIS is to survey the Galactic plane in the emission line of Paschen-α (Paα, 1.88 μ;m) and to detect the cosmic infrared background (CIB) radiation. Comparing the Paα map with the Hα data from ground-based surveys, we can probe the origin of the warm-ionized medium (WIM) of the Galaxy. The CIB is being suspected to be originated from the first generation stars of the Universe and we will test this hypothesis by comparing the fluctuations in I (0.9~1.2 um) and H (1.2~2.0 um) bands to search the red shifted Lyman cutoff signature. Recent progress of the MIRIS imaging system design will be presented.