|
|
 ASCA's X-ray Telescopes
The four X-ray telescopes (XRT) onboard ASCA were built by NASA's Goddard Space
Flight Center and Nagoya University. The basic design of the telescope
approximates the conventional opticals-paired hyperbolic and parabolic
surfaces-with conical surfaces realised as a set of closely nested concentric
thin foils (120 per telescope) held together in quadrants by metal fittings.
The foils are made of aluminium and coated with 10 to 20 microns of acryllic and60 nm of gold, which provided the reflecting surface.
Although the use of foils, which cannot be smoothed by polishing, reduces the
sharpness of the image compared with conventional X-ray optics, it does provide
a larger collecting area and broader pass band.
The "vital statistics" of the four XRT combined are as follows:
- Effective Area: 1,300 cm**2 at 1 keV; 600 cm**2 at 7 keV
- Pass band: up to 12 keV
- Field of View (FWHM): 24 arcmin at 1 keV, 16 arcmin at 7 keV
- Angular Resolution: 2.9 arcmin HPD (Half Power Diameter)
Pictures of ASCA XRT
Effective area, angular response, and Point Spread Function (PSF) of ASCA XRT
References:
Serlemitosos, P. J. et al. 1995, "The X-ray Telescope with ASCA", Publ. Astron. Soc. Japan, 47, 105
Tsusaka, Y. et al. 1995, "Characterization of the Advanced Satellite for Cosmology and Astrophysics x-ray telescope: preflight calibration
and ray tracing", Applied Optics, 34, 22
Tsusaka, Y. et al. 1994 "Calibration of Astro-D telescope with an x-ray pencil beam", SPIE, 2011, 517
Kunieda, H. et al. 1993, Jpn, J. Appl. Phys. 32, 4805
|
