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Examining the Angular Resolution of the Astro-H's Soft X-Ray TelescopesThe 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 x 8 mm beam. As a result, we estimated those errors in a quadrant to be approx. 0.9 to 1.0 and approx. 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.
Document ID
20170009124
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Sato, Toshiki
(Tokyo Univ. Japan)
Iizuka, Ryo
(Tokyo Univ. Japan)
Ishida, Manabu
(Graduate Univ. for Advanced Studies Japan)
Kikuchi, Naomichi
(Tokyo Univ. Japan)
Maeda, Yoshitomo
(Graduate Univ. for Advanced Studies Japan)
Kurashima, Sho
(Tokyo Univ. Japan)
Nakaniwa, Nozomi
(Tokyo Univ. Japan)
Tomikawa, Kazuki
(Tokyo Univ. Japan)
Hayashi, Takayuki
(Nagoya Univ. Nagoya, Japan)
Mori, Hideyuki
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Okajima, Takashi
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Serlemitsos, Peter J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Soong, Yang
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Izumiya, Takanori
(Chuo Univ. Tokyo, Japan)
Minami, Sari
(Nara Women's Univ. Japan)
Date Acquired
September 28, 2017
Publication Date
October 7, 2016
Publication Information
Publication: Journal of Astronomical Telescopes, Instruments, and Systems
Volume: 2
Issue: 4
ISSN: 2329-4124
Subject Category
Optics
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN46243
Distribution Limits
Public
Copyright
Other
Keywords
Astro-H/Hitomi; soft x-ray telescope; SXT; Wolter type-I optics; angular resolut

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