Sensitivity degradation of ISUAL instruments and its impact on observations

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Title:	Sensitivity degradation of ISUAL instruments and its impact on observations
Authors:	郭政靈;Chen, Alfred Bing-Chih;Wu, Yen-Jung;Chiang, Chih-Yu;Huang, Yin-Chieh;Kuo, Cheng-Ling;Su, Han-Tzong;Hsu, Rue-Ron;Mende, Stephen B.;Frey, Harald U.;Harris, Stewart E.;Takahashi, Yukihiro;Lee, Lou-Chuan
Contributors:	地球科學學院太空科學與工程學系
Keywords:	Anomalies;Atmospheric electricity;Atmospheric Science;Degradation;Detection;Earth and Planetary Sciences (miscellaneous);El Nino;El Nino phenomena;El Nino-Southern Oscillation event;El Nino-Southern Oscillation event forecasting;Imager of Sprites and Upper Atmospheric Lightnings (ISUAL);Instruments;Lightning;Lightning activity;Microchannel plates;Microchannels;Oceanography;Photometry;Photomultiplier tubes;Photons;Sensitivity;Sensors;Southern Oscillation;Space instrument;Statistical methods;Surveying;Transient luminous events;Transient luminous events (TLEs)
Date:	2012-02-01
Issue Date:	2026-04-23 11:05:58 (UTC+8)
Publisher:	Chinese Geoscience Union;Taiwan: Springer Science and Business Media LLC
Abstract:	摘要： In the past 6 years, the ISUAL payload onboard the Taiwanese FORMOSAT-2 satellite has successfully carried out the primary mission of performing a global survey of transient luminous events (TLE) and lightning activities. The observation data have been used to construct the first global distribution map of TLEs and to infer their occurrence rates. To register dim TLE emissions at night, ISUAL employs electron-multiplying devices like a photomultiplier, multi-anode array, and micro-channel plate to intensify the photons emitted by transient events. These devices, however, will degrade gradually with age. The degradation rate and the performance change were monitored through periodic calibration observations and are investigated carefully in order to achieve precise photometry and accurate statistics. The annual degradation rates up to 14% were identified for some of the sensor elements. This paper presents the variations of instrument efficiencies and overall detection capabilities, before and after applying a gain-adjustment to compensate for sensor degradation. The resulting stable trend of the ISUAL trigger and lightning rates suggests that the bias from instrument degradation and gain adjustments is minimal. This point is also supported by the near constant sprite and halo detection rates deduced from different statistical temporal intervals. Hence, the anomalies in the ISUAL elve detection rate for 2008 ~ 2009 likely are due to the El Niño and Southern Oscillation (ENSO) events. Forecast based on the ISUAL performance trend also indicates that the ISUAL sensors have sufficient sensitivity margins to operate efficiently until the end of 2013, or even beyond. 出版者： Taiwan: Springer Science and Business Media LLC 出版日期： 2012-02-01 出處： TAO : Terrestrial, atmospheric, and oceanic sciences, 2012-02, Vol.23 (1), p.71- 資源來源： Journals學術期刊資料庫(原CEPS) 版權： 2012. This work is licensed under https://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License. 識別號： ISSN: 1017-0839 識別號： ISSN: 2223-8964 識別號： ISSN: 2311-7680 識別號： EISSN: 2311-7680 識別號： DOI: 10.3319/tao.2011.06.20.01(aa)
Appears in Collections:	[DEPARTMENT OF SPACE SCIENCE AND ENGINEERING] journal & Dissertation

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