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ASTRO-H is an astrophysics satellite dedicated for X-ray spectroscopic study non-dispersively and to carry out survey complementally, which will be borne out of US-Japanese collaborative effort. Among the onboard instruments there are four conically approximated Wolter-I X-ray mirrors, among which two of them are soft X-ray mirrors\ of which the energy range is from a few hundred eV to 15 keY, currently being fabricated in the X-ray Optics Lab at Goddard Space Flight Center. The focal point instruments will be a calorimeter (SXS) and a CCD camera (SXI), respectively. The reflectors of the mirror are made of heat-formed aluminum substrate of the thickness gauged of 152 !lm, 229 !lm, and 305 !lm of the alloy 5052 H-19, followed by epoxy replication on gold-sputtered smooth Pyrex cylindrical mandrels to acquire the X-ray reflective surface. The epoxy layer is 10 !lm nominal and surface gold layer of 0.2 !lm. Improvements on angular response over the Astro-ElISuzaku mirrors come from error reduction on the figure, the roundness, and the grazing angle/radius mismatching of the reflecting surface, and tighter specs and mechanical strength on supporting structure to reduce the reflector positioning and the assembly errors. In this paper, we report the results of calibration of the engineering model of SXT (EM), and project the quality of the flight mirrors.Keywords: X-ray Optics, X-ray Telescope, X-ray Astrophysical Instrument IntrodnctionConical approximation ofthe Wolter-I type X-ray imagers has been a major tool for spectroscopic study in the last quarter of century since the launch of a sounding rocket experiment to study SN 1987 A. The high throughput, essential for the spectroscopic study, of the telescope is provided by using thin-foil reflectors, and the continuous improvement of angular response on X-ray imaging is accomplished by switching the substrate surface smoothing scheme from earlier lacquer-dipping to recent epoxy replication that reduced the mid-frequency waviness 2 • The low micro-roughness of the surface produces specular reflection of X-rays, with high Z material such as Au, Pt, or Ir as the reflecting surface. The energy range coverage can be up to 15 ke V by lowering the grazing angle. Despite the continuous improvement over the last two decades from 4 to 1.7 arc-minutes, the demand of even better angular resolution of such thin-foil mirrors is high. The current image quality is still far from achieving the conical approximation limit, which is about 0.2 arc-minute. The difficulty comes from the relatively weak mechanical integrity of the reflectors and the imprecision in the assembly/aligmnent scheme. The improvement ofHPD from the Suzaku mirror of2 arc-minutes to the recent test of engineering model of ASTRO-H of 1 arc-minute will be the main subject of this paper.

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Abstract:The atomic scattering factor in the energy range of 11.2-15.4 keV for the ASTRO-H Soft X-ray Telescope (SXT) is reported. The large effective area of the SXT makes use of photon spectra above 10 keV viable, unlike most other X-ray satellites with total-reflection mirror optics. Presence of gold's L-edges in the energy band is a major issue, as it complicates the function of the effective area. In order to model the area, the reflectivity measurements in the 11.2-15.4 keV band with the energy pitch of 0.4 -0.7 eV were made in the synchrotron beamline Spring-8 BL01B1. We obtained atomic scattering factors f1 and f2 by the curve fitting to the reflectivities of our witness sample. The edges associated with the L-I, II, and III transitions are identified, of which the depths are found to be roughly 60% shallower than those expected from the Henke's atomic scattering factor.