7 October 2016 Examining the angular resolution of the ASTRO-H’s soft x-ray telescopes
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Abstract
The international x-ray observatory ASTRO-H was renamed “Hitomi” after launch. It covers a wide energy range from a few hundred eV to 600 keV. It is equipped with two soft x-ray telescopes (SXTs: SXT-I and SXT-S) for imaging the soft x-ray sky up to ∼12  keV, which focus an image onto the respective focal-plane detectors: CCD camera (SXI) and a calorimeter (SXS). The SXTs are fabricated in a quadrant unit. The angular resolution in half-power diameter (HPD) of each quadrant of the SXTs ranges between 1.1 and 1.4 arc min at 4.51 keV. It was also found that one quadrant has an energy dependence on the HPD. We examine the angular resolution with “spot scan” measurements. In order to understand the cause of imaging capability deterioration and to reflect it to the future telescope development, we carried out spot scan measurements, in which we illuminate all over the aperture of each quadrant with a square beam 8 mm on a side. Based on the scan results, we made “maps” of image blurring and a focus position. The former and the latter reflect figure error and positioning error, respectively, of the foils that are within the incident 8  mm×8  mm beam. As a result, we estimated those errors in a quadrant to be ∼0.9 to 1.0 and ∼0.6 to 0.9 arc min, respectively. We found that the larger the positioning error in a quadrant is, the larger its HPD is. The HPD map, which manifests the local image blurring, is very similar from quadrant to quadrant, but the map of the focus position is different from location to location in each telescope. It is also found that the difference in local performance causes energy dependence of the HPD.
© 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)
Toshiki Sato, Toshiki Sato, Ryo Iizuka, Ryo Iizuka, Manabu Ishida, Manabu Ishida, Naomichi Kikuchi, Naomichi Kikuchi, Yoshitomo Maeda, Yoshitomo Maeda, Sho Kurashima, Sho Kurashima, Nozomi Nakaniwa, Nozomi Nakaniwa, Kazuki Tomikawa, Kazuki Tomikawa, Takayuki Hayashi, Takayuki Hayashi, Hideyuki Mori, Hideyuki Mori, Takashi Okajima, Takashi Okajima, Peter J. Serlemitsos, Peter J. Serlemitsos, Yang Soong, Yang Soong, Takanori Izumiya, Takanori Izumiya, Sari Minami, Sari Minami, } "Examining the angular resolution of the ASTRO-H’s soft x-ray telescopes," Journal of Astronomical Telescopes, Instruments, and Systems 2(4), 044001 (7 October 2016). https://doi.org/10.1117/1.JATIS.2.4.044001 . Submission:
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