Development of a Cryogenic Infrared Camera with a Wide Field of View

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Elemnts required for the development of the cryogenic infrared camera were divided into three categories : cryogenics, optics, and electronics. Each development is nearly completed.A cryostat with a large opening was designed and manufactured. Despite of large heat coming in from the window, the whole optics can be maintained below 80K and the detector unit below 30K,by using a closed cycle cooler. Indium seal and copper wires were employed to improve heat conduction and expel the heat from the cooler head efficiently. Cryogenic motors were made out of usual commmerical motors be changing bearings, and their tests have established their motion at the liquid nitrogen temperature.Metal mirrors were manufactured and examined. First, several small test mirrors were made : offset parabolas, parabolas of 10 cm in diameter, and spherical mirrors of 15 cm in diameter. All of them turned out to have sufficient accuracy. A Ritchey-Chretien optics was adopted as the primary and secondary mirrors. The primary (25 cm in diameter) and secondary have been designed and manufactured. Two-pieceens for aberration correction was also manufactured.Test electronics was completed and shows sufficiently low noise. MESSIA-III (National Astronomical Observatory of Japan) will be used as detector-independent part.The above three elements will be integrated, and observation of the Galactic plane with it will be started this year.