The lightweight cryogenic telescope on board the Japanese infrared astronomical satellite, ASTRO-F, which is scheduled to be launched early in 2006, forms an F/6 Ritchey-Chretien system with a primary mirror of 710 mm in diameter. The mirrors of the ASTRO-F telescope are made of sandwich-type silicon carbide (SiC) material, comprising a porous core and a chemical-vapor-deposited coat of SiC on the surface. To estimate the optical performance of the flight model telescope, the telescope assembly was tested at cryogenic temperatures, the total wavefront errors of which were measured by an interferometer from outside a liquid-helium chamber. As a result, the wavefront error obtained at 9 K shows that the imaging performance of the ASTRO-F telescope is diffraction limited at a wavelength of 6.2 µm, which is a little worse than our original goal of diffraction-limited performance at 5.0 µm.
© 2005 Optical Society of America
(110.6770) Imaging systems : Telescopes
(120.6650) Instrumentation, measurement, and metrology : Surface measurements, figure
(220.4840) Optical design and fabrication : Testing
(230.4040) Optical devices : Mirrors
(350.1260) Other areas of optics : Astronomical optics
Hidehiro Kaneda, Takashi Onaka, Takao Nakagawa, Keigo Enya, Hiroshi Murakami, Ryoji Yamashiro, Tatsuhiko Ezaki, Yasuyuki Numao, and Yoshikazu Sugiyama, "Cryogenic optical performance of the ASTRO-F SiC telescope," Appl. Opt. 44, 6823-6832 (2005)