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18 August 2005 Optical system of the 12-26 micron instrument (MIR-L) for ASTRO-F
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The MIR-L is the mid-IR (12-26 μm) instrument for Japanese infrared astronomical satellite, the ASTRO-F. The instrument has 2 observing modes: a wide field imaging mode with a field of view of 10.7 × 10.2 arcmin2 and a low resolution spectroscopic mode with a spectral resolution R = λ/Δλ about 20. The spectroscopic mode provides with not only slit-spectroscopy for extended sources but also slitless-spectroscopy for point sources. We describe here the design, manufacturing, and performance evaluation of the cryogenic optical system of the MIR-L. The concept of the optical system design is to realize wide field observations with a compact size. The instrument employs a refractive optics of 5 lenses (CsI - CsI - KRS-5 - CsI - KRS-5) with a 256×256 pixel Si:As IBC array detector, 3 filters, and 2 grisms. The refractive indices of CsI and KRS-5 at the operating temperature of about 6 K have ambiguities because of the difficulty of the measurements. We therefore designed the MIR-L optics with tolerances for the uncertainties of the indices. Since both CsI and KRS-5 have the fragility and the large thermal expansion, we designed a specialized mounting architecture to prevent from making damages and/or decentrations of the lenses at cryogenic temperatures under the serious vibration during the launch. As a result, the optical system of the MIR-L has passed both vibration and thermal cycle tests without damage and performance degradation, and achieved diffraction limited performance over its full wavelength range at the operating temperature.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Naofumi Fujishiro, Hideo Matsuhara, Yuji Ikeda, Tomoyasu Yamamuro, Norihide Takeyama, Takashi Onaka, Hirokazu Kataza, Takehiko Wada, Kazunori Uemizu, Itsuki Sakon, Chiaki Ihara, Daisuke Ishihara, Woojung Kim, Munetaka Ueno, Hidenori Watarai, and Hiroshi Murakami "Optical system of the 12-26 micron instrument (MIR-L) for ASTRO-F", Proc. SPIE 5904, Cryogenic Optical Systems and Instruments XI, 59040I (18 August 2005);


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