In-flight verification of the calibration and performance of the ASTRO-H (Hitomi) soft x-ray spectrometer

Maurice A. Leutenegger, Marc Audard, Kevin R. Boyce, Gregory V. Brown, Meng P. Chiao, Megan E. Eckart, Ryuichi Fujimoto, Akihiro Furuzawa, Matteo Guainazzi, Daniel Haas, Takayuki Hayashi, Jan Willem Den Herder, Ryo Iizuka, Manabu Ishida, Yoshitaka Ishisaki, Naomichi Kikuchi, Caroline A. Kilbourne, Shu Koyama, Sho Kurashima, Yoshitomo MaedaMaxim Markevitch, Dan Mccammon, Kazuhisa Mitsuda, Hideyuki Mori, Nozomi Nakaniwa, Takashi Okajima, Stéphane Paltani, Robert Petre, F. Scott Porter, Kosuke Sato, Toshiki Sato, Makoto Sawada, Peter J. Serlemitsos, Hiromi Seta, Gary Sneiderman, Yang Soong, Satoshi Sugita, Andrew E. Szymkowiak, Yoh Takei, Makoto Tashiro, Yuzuru Tawara, Masahiro Tsujimoto, Cor P. De Vries, Tomomi Watanabe, Shinya Yamada, Noriko Yamasaki

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


The Soft X-ray Spectrometer onboard the Astro-H (Hitomi) orbiting x-ray observatory featured an array of 36 silicon thermistor x-ray calorimeters optimized to perform high spectral resolution x-ray imaging spectroscopy of astrophysical sources in the 0.3-To 12-keV band. Extensive preflight calibration measurements are the basis for our modeling of the pulse height-energy relation and energy resolution for each pixel and event grade, telescope collecting area, detector efficiency, and pulse arrival time. Because of the early termination of mission operations, we needed to extract the maximum information from observations performed only days into the mission when the onboard calibration sources had not yet been commissioned and the dewar was still coming into thermal equilibrium, so our technique for reconstructing the per-pixel time-dependent pulse height-energy relation had to be modified. The gain scale was reconstructed using a combination of an absolute energy scale calibration at a single time using a fiducial from an onboard radioactive source and calibration of a dominant time-dependent gain drift component using a dedicated calibration pixel, as well as a residual time-dependent variation using spectra from the Perseus cluster of galaxies. The energy resolution was also measured using the onboard radioactive sources. It is consistent with instrument-level measurements accounting for the modest increase in noise due to spacecraft systems interference. We use observations of two pulsar wind nebulae to validate our models of the telescope area and detector efficiency and to derive a more accurate value for the thickness of the gate-valve Be window, which had not been opened by the time mission operations ceased. We use observations of the Crab nebula to refine the pixel-To-pixel timing and validate the absolute timing.

Original languageEnglish
Article number021407
JournalJournal of Astronomical Telescopes, Instruments, and Systems
Issue number2
Publication statusPublished - 01-04-2018

All Science Journal Classification (ASJC) codes

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


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