Verification of the timing system for the X-ray Imaging and Spectroscopy Mission in the GPS unsynchronized mode

We report the results from the ground and on-orbit verifications of the X-ray Imaging and Spectroscopy Mission timing system when the satellite clock is not synchronized to the Ground Positioning System (GPS) time. In this case, the time is determined by a free-run quartz oscillator of the clock, whose frequency changes depending on its temperature. In the thermal vacuum test performed in 2022, we obtained the GPS unsynchronized mode data and the temperature-versus-clock frequency trend. Comparing the time values calculated from the data and the true GPS times when the data were obtained, we confirmed that the requirement (within a 350-μs error in the absolute time, accounting for both the spacecraft bus and ground systems) was satisfied in the temperature conditions of the thermal vacuum test. We also simulated the variation of the timing accuracy in the on-orbit temperature conditions using the Hitomi on-orbit temperature data and found that the error remained within the requirement over ∼3×105 s. The on-orbit tests were conducted in 2023 September and October as part of the bus system checkout. The temperature-versus-clock frequency trend remained unchanged from that obtained in the thermal vacuum test, and the observed time drift was consistent with that expected from the trend.

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Publication Details

Journal
Journal of Astronomical Telescopes Instruments and Systems
Published
2025-06-03
DOI
https://doi.org/10.1117/1.jatis.11.4.042012
Primary Topic
Atomic and Subatomic Physics Research
Type
article
Field-Weighted Citation Impact
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article

Verification of the timing system for the X-ray Imaging and Spectroscopy Mission in the GPS unsynchronized mode

T. Takagi, Kotaro Fukushima, Ken Ebisawa, Shin Watanabe et al.
Journal of Astronomical Telescopes Instruments and Systems
Atomic and Subatomic Physics Research
article

Verification of the timing system for the X-ray Imaging and Spectroscopy Mission in the GPS unsynchronized mode

T. Takagi, Kotaro Fukushima, Ken Ebisawa, Shin Watanabe, Katsuhiro Hayashi, M. Shidatsu, So Kato, S. Eguchi, Chikara Natsukari, Hideki Uchiyama, Y. Terada, Ryo Iizuka, Chuen Siang Kang, K. Mukai, Eric D. Miller, Yoshiaki Kanemaru, Ryohei Sato, Kenji Hamaguchi, Rie Sato, Anna Ogorzałek, Efrain Perez-Solis, Y. Niida, Hironori Maejima, Robert Hill, Minami Sakama, Takashi Kominato, Satoru Katsuda, M. Tashiro, M. Yamauchi, Naomi Ota, Mihoko Yukita, Kenichi Toda, François Mernier, T. Yoneyama, Kazuhiro Nakazawa, Isabella Brewer, H. Takahashi, Yuusuke Uchida, A. Tanimoto, Yugo Motogami, Morgan D. Waddy, Mark Mekosh, Satoshi Yamada, Nagomi Uchida, Y. Tsuboi, Shoji Ogawa, Matt Holland, Tessei Yoshida, Katja Pottschmidt, Masayoshi Nobukawa, Tsunefumi Mizuno, Aya Kubota, Shin’ichiro Uno, Yuichi Terashima, Michael Loewenstein, Tomoko Nakamoto, Akio Hoshino, Chris Baluta, Tahir Yaqoob, Takumi Shioiri, Joseph B. Fox, Emily Aldoretta
article en

Abstract

We report the results from the ground and on-orbit verifications of the X-ray Imaging and Spectroscopy Mission timing system when the satellite clock is not synchronized to the Ground Positioning System (GPS) time. In this case, the time is determined by a free-run quartz oscillator of the clock, whose frequency changes depending on its temperature. In the thermal vacuum test performed in 2022, we obtained the GPS unsynchronized mode data and the temperature-versus-clock frequency trend. Comparing the time values calculated from the data and the true GPS times when the data were obtained, we confirmed that the requirement (within a 350-μs error in the absolute time, accounting for both the spacecraft bus and ground systems) was satisfied in the temperature conditions of the thermal vacuum test. We also simulated the variation of the timing accuracy in the on-orbit temperature conditions using the Hitomi on-orbit temperature data and found that the error remained within the requirement over ∼3×105 s. The on-orbit tests were conducted in 2023 September and October as part of the bus system checkout. The temperature-versus-clock frequency trend remained unchanged from that obtained in the thermal vacuum test, and the observed time drift was consistent with that expected from the trend.

Journal of Astronomical Telescopes Instruments and SystemsVol. 11(04)
Kagoshima University (JP), Hiroshima University (JP), NEC (Japan) (JP), Kumamoto Gakuen University (JP), Nihon Fukushi University (JP), Shizuoka University (JP), Goddard Space Flight Center (US), Nara University of Education (JP), Tokyo University of Science (JP), Shibaura Institute of Technology (JP), Tohoku University (JP), Japan Aerospace Exploration Agency (JP), National Aeronautics and Space Administration (US), Institute of Space and Astronautical Science (JP), Adnet Systems (United States) (US), Ehime University (JP), Nagoya University (JP), Massachusetts Institute of Technology (US), Saitama University (JP), Chuo University (JP), Nara Women's University (JP)
National Aeronautics and Space Administration, Ministry of Education, Culture, Sports, Science and Technology, Nuclear Safety and Security Commission, Goddard Space Flight Center, Japan Society for the Promotion of Science
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Atomic and Subatomic Physics Research
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