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Journal of Astronomical Telescopes, Instruments, and Systems • Open Access • new

Thermal analyses for initial operations of the soft x-ray spectrometer onboard the Hitomi satellite
Author(s): Hirofumi Noda; Kazuhisa Mitsuda; Atsushi Okamoto; Yuichiro Ezoe; Kumi Ishikawa; Ryuichi Fujimoto; Noriko Yamasaki; Yoh Takei; Takaya Ohashi; Yoshitaka Ishisaki; Ikuyuki Mitsuishi; Seiji Yoshida; Michael DiPirro; Peter Shirron

Paper Abstract

The soft x-ray spectrometer (SXS) onboard the Hitomi satellite achieved a high-energy resolution of 4.9    eV at 6 keV with an x-ray microcalorimeter array cooled to 50 mK. The cooling system utilizes liquid helium, confined in zero gravity by means of a porous plug (PP) phase separator. For the PP to function, the helium temperature must be kept lower than the λ point of 2.17 K in orbit. To determine the maximum allowable helium temperature at launch, taking into account the uncertainties in both the final ground operations and initial operation in orbit, we constructed a thermal mathematical model of the SXS dewar and PP vent and carried out time-series thermal simulations. Based on the results, the maximum allowable helium temperature at launch was set at 1.7 K. We also conducted a transient thermal calculation using the actual temperatures at launch as initial conditions to determine flow and cooling rates in orbit. From this, the equilibrium helium mass flow rate was estimated to be 34 to 42    μ g / s , and the lifetime of the helium mode was predicted to be 3.9 to 4.7 years. This paper describes the thermal model and presents simulation results and comparisons with temperatures measured in the orbit.

Paper Details

Date Published: 27 October 2017
PDF: 7 pages
J. Astron. Telesc. Instrum. Syst. 4(1) 011202 doi: 10.1117/1.JATIS.4.1.011202
Published in: Journal of Astronomical Telescopes, Instruments, and Systems Volume 4, Issue 1
Show Author Affiliations
Hirofumi Noda, Tohoku Univ. (Japan)
Kazuhisa Mitsuda, Institute of Space and Astronautical Science (Japan)
Atsushi Okamoto, Japan Aerospace Exploration Agency (Japan)
Yuichiro Ezoe, Tokyo Metropolitan Univ. (Japan)
Kumi Ishikawa, Institute of Space and Astronautical Science (Japan)
Ryuichi Fujimoto, Kanazawa Univ. (Japan)
Noriko Yamasaki, Institute of Space and Astronautical Science (Japan)
Yoh Takei, Institute of Space and Astronautical Science (Japan)
Takaya Ohashi, Tokyo Metropolitan Univ. (Japan)
Yoshitaka Ishisaki, Tokyo Metropolitan Univ. (Japan)
Ikuyuki Mitsuishi, Nagoya Univ. (Japan)
Seiji Yoshida, Sumitomo Heavy Industries, Ltd. (Japan)
Michael DiPirro, NASA Goddard Space Flight Ctr. (United States)
Peter Shirron, NASA Goddard Space Flight Ctr. (United States)


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