ASTRO-F > Outline of Satellite

Outline of ASTRO-F Satellite

Outline

the exterior of the satellite

ASTRO-F satellite consists of a cryostat and a bus module. A telescope and scientific instruments are stored in the cryostat and cooled by liquid Helium and mechanical coolers. The bus module takes care of house keeping of the satellite, attitude control, data handling, and communication with the ground system. The height and weight of the satellite are 3.7 meters and 952 kg, respectively. The cryostat and the bus module have independent structures so as to decrease heat inflow into the cryostat.


 

the exterior of the satellite

The solar paddle which will supply electric power to the satellite will be extended in the orbit . The cryostat has an aperture lid on the ground so as to keep a tight vacuum and prevent stray light inflow. This aperture lid is ejected in space after establishment of the attitude of the satellite.

ASTRO-F will be launched by M-V launch vehicle No.8 which has also been developed by JAXA/ISAS. The operation after launch is performed principally at Sagamihara Space Operation Center (SSOC) and Uchinoura Space Center (USC).


 

Telescope

Telescope

The ASTRO-F telescope is a Ritchey-Chretien system with F/6.1. The focal length is 4200 mm and effective aperture is 68.5 cm. The entire telescope is cooled down to about 6K during observations. The aim of the cooled telescope is to suppress harmful thermal radiation radiated from telescope itself.

The telescope is composed of a primary mirror, a secondary mirror, trusses which support the secondary mirror, and baffles which prevent stray light. The trusses are made of Beryllium (Be) metal. Beryllium is a material with light weight and good thermal conduction.


 

The back of the primary mirror

The primary mirror is made of SiC (Silicon Carbide), a lightweight and rigid material. The back side of the mirror is hollowed out in order to make it lighter. The actual weight of the 71 cm (effective diameter is 67 cm) primary mirror is only 11 kg. This is the first time a SiC mirror will fly in space.

The surface of the primary mirror is coated by Gold (Au) in order to increase the reflectance at infrared wavelength.


 

Cryostat : Container to keep instruments low temperature

The width of the solar paddle is about 5.5m when extended

The temperature of the telescope is maintained at 5.8K (-267.4C) during observation

Thermal radiation : Electromagnetic wave radiated by all matter corresponding to its temperature

Stray light : Unwanted light which does not passed through the expected route but arrives at the focal plane. e.g. scattered light

Cryostat

The cross section of the cryostat

170 liter of superfluid liquid Helium (at launch time) is loaded into the tank of the cryostat and cools the instruments and the telescope down to a very low temperature.

Two sets of Stirling-cycle mechanical coolers are incorporated in addition to the liquid Helium. The addition of the mechanical coolers extends the Helium life and reduces the quantity of Helium to be carried into space. ASTRO-F will make observations for one and a half years keeping a very low temperature using both liquid Helium and the mechanical coolers.


 

The far-infrared detector for longer wavelength operates at a lowest temperature of 2K (-271.2C)

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ASTRO-F > Outline of Satellite