ULTIMATE-Subaru: conceptual design of WFI, a near-infrared wide field imager

Kentaro Motohara; Yusuke Minowa; Ichi Tanaka; Takashi Hattori; Yusei Koyama; Masahiro Konishi; Kenshi Yanagisawa; Ikuru Iwata; Shiang-Yu Wang; Richard C. Y. Chou; Masahiko Kimura; John Pazder

doi:10.1117/12.2560324

13 December 2020 ULTIMATE-Subaru: conceptual design of WFI, a near-infrared wide field imager

Kentaro Motohara, Yusuke Minowa, Ichi Tanaka, Takashi Hattori, Yusei Koyama, Masahiro Konishi, Kenshi Yanagisawa, Ikuru Iwata, Shiang-Yu Wang, Richard C. Y. Chou, Masahiko Kimura, John Pazder

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Proceedings Volume 11447, Ground-based and Airborne Instrumentation for Astronomy VIII; 114470N (2020) https://doi.org/10.1117/12.2560324
Event: SPIE Astronomical Telescopes + Instrumentation, 2020, Online Only

Abstract

Results of a conceptual design study of ULTAIMTE-Wide Field Imager (WFI) is presented. ULTIMATE-WFI is a near-infrared wide-field imager for the ground-layer adaptive optics system of the Subaru telescope (ULTIMATESubaru) which realizes a 0. 002 seeing size over 200diameter at the Cassegrain focus utilizing a deformable 2ndry mirror. WFI has a 15. 07×15. 07 FoV with a wavelength coverage of 0.9–2.5µm. The FoV is covered by four identical optics, each having a square field lens with 226mm on a side. Its effective FoV is 7. 02 on a side, and is covered by a HAWAII-4RG array detector with a pixel scale of 0. 0011/pix. Effective FoV will be 14. 04×14. 04 or 2070 in total. Spot sizes at a detector plane are less than 0. 001 over the wavelength coverage. Due to the large FoV, vignetting by the telescope structure occurs and an additional cold stop is necessary to block their thermal emission, which causes ~80% vignetting at the edge of the FoV. All the optics are contained in a cylindrical structure to be installed on the Cassegrain focus of the telescope, and kept under cryogenic temperature except for the field lenses. Gravitational deformation will be smaller than 1mm, and may have negligible impact on the final image quality.

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Kentaro Motohara, Yusuke Minowa, Ichi Tanaka, Takashi Hattori, Yusei Koyama, Masahiro Konishi, Kenshi Yanagisawa, Ikuru Iwata, Shiang-Yu Wang, Richard C. Y. Chou, Masahiko Kimura, and John Pazder "ULTIMATE-Subaru: conceptual design of WFI, a near-infrared wide field imager", Proc. SPIE 11447, Ground-based and Airborne Instrumentation for Astronomy VIII, 114470N (13 December 2020); https://doi.org/10.1117/12.2560324

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