title: Cryogenic optical performance of the ASTRO-F SiC telescope.
abstract: 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 microm, which is a little worse than our original goal of diffraction-limited performance at 5.0 microm.
authors.affiliation: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa 229-8510, Japan. kaneda@ir.isas.jaxa.jp
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Kaneda
authors.forename: Takashi
authors.initials: T
authors.lastname: Onaka
authors.forename: Takao
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Keigo
authors.initials: K
authors.lastname: Enya
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Murakami
authors.forename: Ryoji
authors.initials: R
authors.lastname: Yamashiro
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Ezaki
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Numao
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Sugiyama