Cryogenic silicon carbide mirrors for infrared astronomical telescopes: lessons learnt from AKARI for SPICA

Takashi Onaka; Hidehiro Kaneda; Mitsunobu Kawada; Keigo Enya; Takao Nakagawa

doi:10.1117/12.2026662

30 September 2013 Cryogenic silicon carbide mirrors for infrared astronomical telescopes: lessons learnt from AKARI for SPICA

Takashi Onaka, Hidehiro Kaneda, Mitsunobu Kawada, Keigo Enya, Takao Nakagawa

Author Affiliations +

Proceedings Volume 8837, Material Technologies and Applications to Optics, Structures, Components, and Sub-Systems; 88370K (2013) https://doi.org/10.1117/12.2026662
Event: SPIE Optical Engineering + Applications, 2013, San Diego, California, United States

Abstract

Silicon carbide (SiC) has good thermal conductivity, high stiffness, and a relatively low specific density, all of which are advantageous to the application to telescopes operating at cryogenic temperatures. The first Japanese astronomical infrared space mission AKARI, which was launched in 2006 February and completed the second generation all-sky survey at 6 bands from mid- to far-infrared, employed a 700mm cryogenic telescope made of specially developed SiC. It was a sandwich-type of SiC composed of a lightweight porous core and a dense chemical vapor deposition (CVD) coat to decrease the specific density and facilitate machining for achieving the required surface figure accuracy. Measurements with an interferometer of 160-mm sample mirrors demonstrated that the AKARI mirror SiC had good thermal stability down to cryogenic temperatures (~6K), while the mirror support of the compact design became the primary source of the wave-front errors of the AKARI telescope. Taking the advantage of the heritage of the AKARI telescope development as well as ESA’s Herschel telescope, we are planning the next infrared space mission SPICA (Space Infrared Telescope for Cosmology and Astrophysics) of a 3.2m cooled telescope in participation of ESA using SiC-based materials. In this presentation, we summarize the development of AKARI SiC telescope and present the development activities of the SPICA telescope from the point of view of SiC being as the mirror material for cryogenic space infrared telescopes.

Citation Download Citation

Takashi Onaka, Hidehiro Kaneda, Mitsunobu Kawada, Keigo Enya, and Takao Nakagawa "Cryogenic silicon carbide mirrors for infrared astronomical telescopes: lessons learnt from AKARI for SPICA", Proc. SPIE 8837, Material Technologies and Applications to Optics, Structures, Components, and Sub-Systems, 88370K (30 September 2013); https://doi.org/10.1117/12.2026662

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