Verification of the XRISM timing system in the GPS unsynchronized mode

Megumi Shidatsu; Yukikatsu Terada; Takashi Kominato; So Kato; Ryohei Sato; Minami Sakama; Takumi Shioiri; Yugo Motogami; Yuki Niida; Toshihiro Takagi; Chikara Natsukari; Makoto S. Tashiro; Kenichi Toda; Hironori Maejima; Shin Watanabe; Ryo Iizuka; Rie Sato; Chris Baluta; Katsuhiro Hayashi; Tessei Yoshida; Shoji Ogawa; Yoshiaki Kanemaru; Kotaro Fukushima; Akio Hoshino; Hiromitsu Takahashi; Masayoshi Nobukawa; Tsunefumi Mizuno; Kazuhiro Nakazawa; Shin'ichiro Uno; Ken Ebisawa; Satoshi Eguchi; Satoru Katsuda; Aya Kubota; Naomi Ota; Atsushi Tanimoto; Yuichi Terashima; Yohko Tsuboi; Yuusuke Uchida; Hideki Uchiyama; Shigeo Yamauchi; Tomokage Yoneyama; Satoshi Yamada; Nagomi Uchida; Matt Holland; Michael Loewenstein; Eric D. Miller; Tahir Yaqoob; Robert S. Hill; Trisha F. Doyle; Efrain Perez-Solis; Morgan D. Waddy; Mark Mekosh; Joseph B. Fox

doi:10.1117/12.3019651

21 August 2024 Verification of the XRISM timing system in the GPS unsynchronized mode

Megumi Shidatsu, Yukikatsu Terada, Takashi Kominato, So Kato, Ryohei Sato, Minami Sakama, Takumi Shioiri, Yugo Motogami, Yuki Niida, Toshihiro Takagi, Chikara Natsukari, Makoto S. Tashiro, Kenichi Toda, Hironori Maejima, Shin Watanabe, Ryo Iizuka, Rie Sato, Chris Baluta, Katsuhiro Hayashi, Tessei Yoshida, Shoji Ogawa, Yoshiaki Kanemaru, Kotaro Fukushima, Akio Hoshino, Hiromitsu Takahashi, Masayoshi Nobukawa, Tsunefumi Mizuno, Kazuhiro Nakazawa, Shin'ichiro Uno, Ken Ebisawa, Satoshi Eguchi, Satoru Katsuda, Aya Kubota, Naomi Ota, Atsushi Tanimoto, Yuichi Terashima, Yohko Tsuboi, Yuusuke Uchida, Hideki Uchiyama, Shigeo Yamauchi, Tomokage Yoneyama, Satoshi Yamada, Nagomi Uchida, Matt Holland, Michael Loewenstein, Eric D. Miller, Tahir Yaqoob, Robert S. Hill, Trisha F. Doyle, Efrain Perez-Solis, Morgan D. Waddy, Mark Mekosh, Joseph B. Fox

Author Affiliations +

Proceedings Volume 13093, Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray; 1309365 (2024) https://doi.org/10.1117/12.3019651
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Conference Poster

Abstract

We report the results from the ground and on-orbit verification of the XRISM timing system when the satellite clock is not synchronized to the GPS time. XRISM carries a GPS receiver which synchronizes the main satellite clock to the GPS time but in a rare case that the satellite fails to receive the GPS signal, the clock runs freely and its frequency changes depending on its temperature. In this case, we correct the time drift considering the temperature dependency of the clock frequency measured in advance. To confirm that the accuracy of the time assignment in the GPS unsynchronized mode satisfies the requirement (within a 350 us error in the absolute time, for the satellite bus system plus ground system), we have performed the ground and on-orbit tests. 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 assigned to the data and the true GPS times when the data were obtained, we confirmed that the requirement was satisfied in the temperature condition 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 the dependency of the timing error on the temperature gradient obtained in the thermal vacuum test. We found that the error remained within the requirement over ∼ 300000 s without any time calibration data. After the launch, we performed on-orbit tests in 2023 September and October as part of the bus system checkout. The temperature versus clock frequency trend was found to remain 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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Megumi Shidatsu, Yukikatsu Terada, Takashi Kominato, So Kato, Ryohei Sato, Minami Sakama, Takumi Shioiri, Yugo Motogami, Yuki Niida, Toshihiro Takagi, Chikara Natsukari, Makoto S. Tashiro, Kenichi Toda, Hironori Maejima, Shin Watanabe, Ryo Iizuka, Rie Sato, Chris Baluta, Katsuhiro Hayashi, Tessei Yoshida, Shoji Ogawa, Yoshiaki Kanemaru, Kotaro Fukushima, Akio Hoshino, Hiromitsu Takahashi, Masayoshi Nobukawa, Tsunefumi Mizuno, Kazuhiro Nakazawa, Shin'ichiro Uno, Ken Ebisawa, Satoshi Eguchi, Satoru Katsuda, Aya Kubota, Naomi Ota, Atsushi Tanimoto, Yuichi Terashima, Yohko Tsuboi, Yuusuke Uchida, Hideki Uchiyama, Shigeo Yamauchi, Tomokage Yoneyama, Satoshi Yamada, Nagomi Uchida, Matt Holland, Michael Loewenstein, Eric D. Miller, Tahir Yaqoob, Robert S. Hill, Trisha F. Doyle, Efrain Perez-Solis, Morgan D. Waddy, Mark Mekosh, and Joseph B. Fox "Verification of the XRISM timing system in the GPS unsynchronized mode", Proc. SPIE 13093, Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 1309365 (21 August 2024); https://doi.org/10.1117/12.3019651

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