蘭摩爾探針的電子溫度濃度估算法以解決表面汙染與微衛星面積比問題;Estimate Correct Electron Temperature and Electron Density by Langmuir Probe Despite Probe Contamination And Small CubeSat To Probe Surface Area Ratio

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题名:	蘭摩爾探針的電子溫度濃度估算法以解決表面汙染與微衛星面積比問題;Estimate Correct Electron Temperature and Electron Density by Langmuir Probe Despite Probe Contamination And Small CubeSat To Probe Surface Area Ratio
作者:	江承剛;Chen-Kang Chiang
贡献者:	光機電工程研究所
关键词:	蘭摩爾探針;面積比;汙染層;Langmuir probe;area ratio;contaminated layer
日期:	2020-06-17
上传时间:	2020-09-02 15:36:08 (UTC+8)
出版者:	國立中央大學
摘要:	本論文為搭載在立方衛星上的蘭摩爾探針( Langmuir probe, LP)設計一套演算法，以解決進行量測時應該克服的兩個對量測的重要干擾，以便準確計算探針周圍的電子溫度與電子濃度。一個問題是，當衛星表面積過小，量測時應保持不變的衛星機殼電位參考產生偏移；另一個是覆蓋在探針與衛星表面的汙染層電容，會隨著量測的掃描電壓一起充放電。這兩個因素都會使量測到的I-V特性曲線產生扭曲，影響電子溫度與濃度的估算結果。為解決這些問題，先建立了一個蘭摩爾探針量測的等效電路模型，使用電路模擬軟體來重現過去文獻中提到的面積與汙染問題。從而推導了探針德拜鞘(Debye Sheath, DS)電壓、機殼DS電壓、汙染層電壓與掃描電壓的關係式，並提出了一套演算法來估算在探針DS上的電壓做為量測數據的修正，以獲得更準確的探針I-V特性曲線，而得以計算出正確的電子溫度與電子濃度。最後使用美國的國防氣象衛星計劃 (Defense Meteorological Satellite Program, DMSP)中取得850km軌道中電離層的電子溫度(1000K~3500K)與電子濃度(103 ~ 106 cm-3)資料來驗證演算法的適用性。當衛星對探針的面積比為6倍以上且有高達100ms時間常數的汙染層時，演算法的修正可以將失真降至5%以下，並且可以將電子溫度濃度的採樣頻率提高至5Hz。;Probe contamination and limited CubeSat to probe surface area ratio were two factors seriously disturbing the I-V curve data measured by a DC Langmuir probe (LP) and, thus, the accuracy to calculate the electron temperature and electron density in the ionosphere. When the satellite surface area is too small that the electric potential of satellite body as the reference ground can be shifted during the voltage driven measurement distorting the results. Moreover, probe contamination forms a capacitive layer which gets charged and discharged together with the probe Debye Sheath (DS) under test distorting the measurements. To correct the distortions, an electric circuit model of the satellite Debye-Sheath (DS), the probe DS, contaminated layers, and the scan voltage source is constructed to simulate and describe their functional relationship during measurement and the causes of the distortions. An algorithm is developed to find the actual probe voltage from the scan voltage so that the correct I–V curve for the LPs can be obtained to estimate the electron temperature and density correctly surrounding a small satellite. Tuning and verifying the algorithm for real in orbit conditions, the ionosphere electron temperature <3500K and density <10^6 cm^3 observed by the Defense Meteorological Satellite Program (DMSP) in 850km orbit were distorted according to the circuit model and corrected by our algorithm. The circuit model simulates a probe on a CubeSat of area at least 6 times the probe with contamination time constant up to 10ms and the distorted data can be corrected to estimate electron temperature and density with less than 5% error.
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