星载差分吸收光谱仪噪声分析及处理方法

Noise Analysis and Processing Method of Environment Monitoring Instrument

噪声对星载大气痕量气体差分吸收光谱仪信噪比具有重大影响,其是衡量光谱仪成像质量和痕量气体反演能力的标准。为量化并去除光谱仪系统噪声从而提高信噪比,分析了光谱仪噪声来源并给出了相应噪声模型,在此基础上建立了光谱仪信噪比模型。研究了入射光强度、积分时间和系统增益对系统信噪比的影响。通过光谱仪辐射定标试验数据对不同工作模式和不同参数与信噪比的关系进行了对比验证。并提出主要系统噪声的处理方法:利用线性拟合取截距法确定系统偏置噪声;在地面利用暗电流温度相关性获得温度修正因子实现载荷在轨暗电流校正;在探测器响应线性范围内利用两点校正法对PRNU噪声进行修正。结果表明:全幅成像模式下,可见1通道电子学偏置噪声响应DN值2 625,可见2通道电子学偏置噪声响应DN值2 763;暗电流噪声在CCD成像面温度高于0℃时占主要部分,温度下降至-20℃时其余噪声起主导作用,验证了CCD最佳制冷温度;光谱仪信噪比随着入射光响应和积分时间的增加而增大,系统增益不会影响信噪比;PRNU噪声通过校正得到明显改善,由3.32%下降到0.47%,提高了光谱仪成像质量。该噪声分析和处理方法对后期光谱数据的痕量气体反演提供帮助。

The noise has a significant effect on the Signal to Ratio(SNR)of the trace gasabsorption spectrometer,which is a standard for evaluating the imaging qualityand trace gas retrieving capability.To quantitatively assess factors affecting SNR,and remove the noise of the spectrometer system,the noise source of the spectrometer is analyzed and the corresponding noise model is given.On thisbasis,the SNR model of the spectrometer is established in this paper.In addition,the effects of incident light intensity,integration time and system gain on the SNR are studied.The relationship between the different operating modes and different parameters and SNR is verified by the calibration experiment data of the spectrometer.Andthe main system noise is proposed:the linear deviation is used to determine the system offset noise.Besides,the temperature correction factor is obtained by using the dark current temperature correlation on the ground to realize the load in-orbit dark current correction.In the linear range of the detector response PRNUnoise is corrected by the two-point correction method.The results show that the DN value of UV1 channel electronic offset noise is 2 625,and UV2 is 2 763.The dark current noise is the main part when the CCD imaging surface temperature is higher than 0℃,The temperature decreases to-20℃when the rest of the noise plays a leading role to verify the best cooling temperature of the CCD;SNR increases with the increasing incident light response and integration time,the system gain will not affect SNR;PRNU noise was significantly improved bycorrection,decreasing from 3.32%to 0.47%,improving the spectral quality of the spectrometer.The noise analysis and processing methods are conducive to trace gas retrieve of further spectral data.