Cryogenic optical performance of the ASTRO-F SiC telescope

Kaneda, Hidehiro; Onaka, Takashi; Enya, Keigo; Murakami, Hiroshi; Yamashiro, Ryoji; Ezaki, Tatsuhiko; Numao, Yasuyuki; Sugiyama, Yoshikazu

doi:10.1364/ao.44.006823

Cited by 36 publications

(31 citation statements)

References 2 publications

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“…The deformation of the SiC mirror and the telescope system at cryogenic temperatures have been tested extensively in the laboratory. The deformation of the SiC mirror is shown to be negligible [10], while the deformation originating from the supporting structure is found to dominate in the wavefront errors of the telescope [11]. The AKARI telescope is equipped with a focus adjustment mechanism at the secondary mirror [5].…”

Section: Akari Telescope and On-board Instrumentsmentioning

confidence: 98%

AKARI: space infrared cooled telescope

Onaka

Salama

2009

Exp Astron

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AKARI, formerly known as ASTRO-F, is the second Japanese space mission to perform infrared astronomical observations. AKARI was launched on 21 February 2006 (UT) and brought into a sun-synchronous polar orbit at an altitude of 700 km by a JAXA M-V rocket. AKARI has a telescope with a primary-mirror aperture size of 685 mm together with two focal-plane instruments on board: the Infrared Camera (IRC), which covers the spectral range 2-26 µm and the Far-Infrared Surveyor (FIS), which operates in the range 50-180 µm. The telescope mirrors are made of sandwichtype silicon carbide, specially developed for AKARI. The focal-plane instruments and the telescope are cooled by a unique cryogenic system that kept the telescope at 6K for 550 days with 180 liters super-fluid liquid Helium (LHe) with the help of mechanical coolers on board. Despite the small telescope size, the cold environment and the stateof-the-art detectors enable very sensitive observations at infrared wavelengths. To take advantage of the characteristics of the sun-synchronous polar orbit, AKARI performed an all-sky survey during the LHe holding period in four far-infrared bands with FIS and two mid-infrared bands with IRC, which surpasses the IRAS survey made in 1983 in sensitivity, spatial resolution, and spectral coverage. AKARI also made over 5,000 pointing observations at given targets in the sky for approximately 10 minutes each, for deep imaging and spectroscopy from 2 to 180 µm during the LHe holding period. The LHe ran out on 26 August 2007, since which date the telescope and instrument are still kept around 40K by the mechanical cooler on board, and near-infrared imaging and spectroscopic observations with IRC are now being continued in pointing mode.

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Section: Akari Telescope and On-board Instrumentsmentioning

confidence: 98%

AKARI: space infrared cooled telescope

Onaka

Salama

2009

Exp Astron

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“…We had not had sufficient information on the cryogenic properties of the materials used for the AKARI telescope at the early design phase and we realized the problem of the mirror support structure after the failure at the vibration test. Only limited modifications in the mirror support structure were possible during the refurbishment of the telescope system were limited due to the constraints of the original mirror design 15 . The lessons we have learnt from the development of the AKARI telescope strongly suggests the importance of the careful design of the mirror support structure at the early phase and also calls for the investigation of mirror materials that will facilitate an improved mirror support structure for the next mission.…”

Section: Akari Telescope Silicon Carbidementioning

confidence: 99%

“…. Total wave-front errors of the AKARI telescope measured at room temperature (left) and a cryogenic temperature (~9K, right) 6,15 . A trefoil deformation is evident at the cryogenic temperature, which comes from the mirror supporting structure.…”

Section: Akari Telescope Silicon Carbidementioning

confidence: 99%

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

et al. 2013

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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.

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“…Either the phases are composed from different materials (as in the case of silicon carbide) or from different modifications of one material (as in the case of CFC). The number of applications of such materials is actually rapidly increasing: high performance brake systems [1], telescopes for space application based on sintered silicon carbide [2], metal matrix composites such as lightweight composite wires [3], just to name a few. Especially for CFC, the dimensioning with respect to thermomechanical loading is of utmost importance since in almost all applications of CFC, high temperatures are present.…”

Section: Introductionmentioning

confidence: 99%

Restrictions to the Energy Density in Energetic Models of Carbon Fiber Reinforced Carbon

Langhoff

Schnack

2008

Mechanics of Advanced Materials and Structures

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In this contribution an energetic model for multi-phase materials is developed describing the influence of microstructure on different length scales as well as the evolution of phase changes. Restrictions on the energy functional are discussed. In such a nonconvex framework, interfacial contributions serve for relaxing the total energy. Such models can be applied to describe the macroscopic material properties of carbon fiber reinforced carbon where phase transitions between regions of different texture of the carbon matrix are observed on a nanoscale as well as columnar microstructures on microscale.

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Cryogenic optical performance of the ASTRO-F SiC telescope

Cited by 36 publications

References 2 publications

AKARI: space infrared cooled telescope

AKARI: space infrared cooled telescope

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

Restrictions to the Energy Density in Energetic Models of Carbon Fiber Reinforced Carbon

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