Multi-purpose Infra-Red Imaging System (MIRIS) is a near-infrared camera onboard on the Korea Science and
Technology Satellite 3 (STSAT-3). The MIRIS is a wide-field (3.67° × 3.67°) infrared imaging system which employs a
fast (F/2) refractive optics with 80 mm diameter aperture. The MIRIS optics consists of five lenses, among which the
rear surface of the fifth lens is aspheric. By passive cooling on a Sun-synchronous orbit, the telescope will be cooled
down below 200 K in order to deliver the designed performance. As the fabrication and assembly should be carried out
at room temperature, however, we convert all the lens data of cold temperature to that of room temperature. The
sophisticated opto-mechanical design accommodates the effects of thermal contraction after the launch, and the optical
elements are protected by flexure structures from the shock (10 G) during the launch. The MIRIS incorporates the wide-band
filters, I (1.05 μm) and H (1.6 μm), for the Cosmic Infrared Background observations, and also the narrow-band
filters, Paα (1.876 μm) and a specially designed dual-band continuum, for the emission line mapping of the Galactic
interstellar medium. We present the optical design, fabrication of components, assembly procedure, and the performance
test results of the qualification model of MIRIS near-infrared camera.
MIRIS is a compact near-infrared camera with a wide field of view of 3.67°×3.67° in the Korea Science and
Technology Satellite 3 (STSAT-3). MIRIS will be launched warm and cool the telescope optics below 200K by pointing
to the deep space on Sun-synchronous orbit. In order to realize the passive cooling, the mechanical structure was
designed to consider thermal analysis results on orbit. Structural analysis was also conducted to ensure safety and
stability in launching environments. To achieve structural and thermal requirements, we fabricated the thermal shielding
parts such as Glass Fiber Reinforced Plastic (GFRP) pipe supports, a Winston cone baffle, aluminum-shield plates, a
sunshade, a radiator and 30 layers of Multi Layer Insulation (MLI). These structures prevent the heat load from the
spacecraft and the earth effectively, and maintain the temperature of the telescope optics within operating range. A micro
cooler was installed in a cold box including a PICNIC detector and a filter-wheel, and cooled the detector down to a
operating temperature range. We tested the passive cooling in the simulated space environment and confirmed that the
required temperature of telescope can be achieved. Driving mechanism of the filter-wheel and the cold box structure
were also developed for the compact space IR camera. Finally, we present the assembly procedures and the test result for
the mechanical parts of 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.
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