台灣福衛三號及七號掩星觀測大氣參數自主程式發展

Taiwan Self-developed Software Development for FORMOSAT-3 and FORMOSAT-7

黃成勇(Cheng-Yung Huang) ； 陳坤林(Kun-Lin Chen) ； 楊善國(Eddy Yang)

《航測及遙測學刊》 19卷4期 (2015/02) Pp. 267-278

https://doi.org/10.6574/JPRS.2015.19(4).1

摘要

從美國1995年美國發射第一顆掩星衛星MicroLab-1掩星衛星觀測地球大氣以來，已經歷經了17個年頭，台灣自2006年發射由六顆衛星組成的福爾摩沙衛星三號，至今也已經邁入第八個年頭，在電離層觀測和大氣觀測及天氣預報上，都有顯著的成果。可惜目前掩星觀測資料處理，仍仰賴美國UCAR的軟體，本研究在國研院國家太空中心的支持下，致力於發展台灣本土的掩星資料自主軟體，期待在福衛七號衛星發射前，可研發撰寫出符合及時及作業化的台灣掩星資料自主程式。本論文章將介紹自主軟體中大氣資料反演部分的發展現況。大氣掩星剖面反演，包含溢相位（Excess Phase）反演，大氣乾、濕溫度剖面反演。在溢相位反演方面，利用低軌道衛星一次差分，將GPS衛星軌道和福衛三號軌道資訊以及三號衛星酬載GOX（GPS Occultation Experiment）所收到的50Hz觀測資料，產出掩星溢相位。主要輸入資料為POD（Precise Orbit Determination）兩個天線所收到的50Hz參考資料和OCC（OCCultation）兩個天線所收到的掩星觀測資料。在乾溫度剖面上，目前使用項位匹配法（phase matching），計算偏折角，改進傳統電離層校正方式，忽略大氣水氣的影響，反演出大氣乾溫度剖面、折射率和壓力剖面。濕氣壓剖面反演須利用地面輔助觀測資料或大氣模式進行一為變分（one-D VAR）最佳化處理。目前前兩部分已經完成符合及時及作業化的雛型軟體，第三部分完成一維變分的主要模組，正積極改寫成作業化程式。

關鍵字

福衛三號 ； 掩星觀測 ； 全球定位系統

並列摘要

The radio occultation technique for observing atmosphere and ionosphere has been developing for seventeen years, since the launch of the first radio occultation satellite MicroLab-1. The six micro-satellites FORMOSAT-3, the first constellation to observe atmosphere, can provide the global coverage limb measurements above earth surface in all time. It had been proven to be a powerful tool to observe parameters of ionosphere and atmosphere. The radio occultation data is processed by CDAAC software developed by UCAR. Currently, the GPSARC are working hard to develop the Taiwan self-developed scientific software to process the radio occultation data for both missions, FORMOSAT-3 and FORMOSAT-7, NSPO and TACC are developing the automatic and independent system to process the RO data. In this study, we introduce the status of self-developed software about the atmospheric RO data process. The atmospheric radio Occultation data process include three main procedures, excess phase retrieval, dry parameter profiles retrieval and wet parameter profiles retrieval. The main function of excess phase retrieval is retrieve the OCC observation to excess phase with orbit information of GPS and FS3. The Dry parameter profiles retrieval will produce bending angle, refraction index, pressure and dry temperature without considering the water vapor. The wet parameter retrieval will produce the same atmospheric profiles, except the dry temperature is replaced by wet temperature, and produce the extra water vapor pressure.

並列關鍵字

FORMOSAT-3 ； GPS ； Occultation ； FORMOSAT-7

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