In-orbit performance and calibration of the Hard X-ray Imager onboard Hitomi (ASTRO-H)

Kouichi Hagino, Kazuhiro Nakazawa, Goro Sato, Motohide Kokubun, Teruaki Enoto, Yasushi Fukazawa, Katsuhiro Hayashi, Jun Kataoka, Junichiro Katsuta, Shogo B. Kobayashi, Philippe Laurent, Francois Lebrun, Olivier Limousin, Daniel Maier, Kazuo Makishima, Taketo Mimura, Katsuma Miyake, Tsunefumi Mizuno, Kunishiro Mori, Hiroaki MurakamiTakeshi Nakamori, Toshio Nakano, Hirofumi Noda, Hirokazu Odaka, Masanori Ohno, Masayuki Ohta, Shinya Saito, Rie Sato, Hiroyasu Tajima, Hiromitsu Takahashi, Tadayuki Takahashi, Shin'ichiro Takeda, Takaaki Tanaka, Yukikatsu Terada, Hideki Uchiyama, Yasunobu Uchiyama, Shin Watanabe, Kazutaka Yamaoka, Yoichi Yatsu, Takayuki Yuasa

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


The Hard X-ray Imager (HXI) onboard Hitomi (ASTRO-H) is an imaging spectrometer covering hard x-ray energies of 5 to 80 keV. Combined with the Hard X-ray Telescope, it enables imaging spectroscopy with an angular resolution of 10.7 half-power diameter, in a field of view of 9' × 9'. The main imager is composed of four layers of Si detectors and one layer of CdTe detector, stacked to cover a wide energy band up to 80 keV, surrounded by an active shield made of Bi4Ge3O12 scintillator to reduce the background. The HXI started observations 12 days before the Hitomi loss and successfully obtained data from G21.5-0.9, Crab, and blank sky. Utilizing these data, we calibrate the detector response and study properties of in-orbit background. The observed Crab spectra agree well with a powerlaw model convolved with the detector response, within 5% accuracy. We find that albedo electrons in specified orbit strongly affect the background of the Si top layer and establish a screening method to reduce it. The background level over the full field of view after all the processing and screening is as low as the preflight requirement of 1 - 3 × 10-4 counts s-1 cm-2 keV-1.

Original languageEnglish
Article number021409
JournalJournal of Astronomical Telescopes, Instruments, and Systems
Issue number2
Publication statusPublished - 2018 Apr 1


  • Astronomy
  • Imaging
  • Satellites
  • Semiconductors
  • Spectroscopy
  • X-rays

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Control and Systems Engineering
  • Instrumentation
  • Astronomy and Astrophysics
  • Mechanical Engineering
  • Space and Planetary Science


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