21 August 1998 Telescope system of the infrared imaging surveyor (IRIS)
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Abstract
The telescope system of a Japanese IR Astronomical Space Mission, 'IR Imaging Surveyor (IRIS)', is described. The IRIS is a cryogenically-cooled telescope, being planned to be launched in 2003. It will make astronomical observations from near-IR to far-IR regions. The IRIS telescope system is a Ritchey-Chretien type, whose primary mirror size ins 700mm in diameter and whose system F ratio is 6. In order to share the focal plane with two scientific instruments and a focal- plane star sensor, it has a clear field of view of 38 arcminutes in radius. It is being designed to achieve the diffraction-limited performance at 5 micrometers for temperatures below 10K. The IRIS telescope will use light-weight silicon carbide (SiC) mirrors. The current estimate of the primary mirror weight is 9 kg and the goal of total weight of the telescope system is less than 27 kg. Preliminary tests of small size SiC mirrors at 4.2K suggest that slight distortion of the surface figure detected at low temperatures can be reduced by improved CVD processes. The telescope system is designed to meet the launch conditions of the M-V rocket and to have the fundamental frequencies above 100 Hz.
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Takashi Onaka, Yoshikazu Sugiyama, Shinji Miura, "Telescope system of the infrared imaging surveyor (IRIS)", Proc. SPIE 3354, Infrared Astronomical Instrumentation, (21 August 1998); doi: 10.1117/12.317291; https://doi.org/10.1117/12.317291
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