115～180 nm远紫外临边成像光谱仪原理样机是针对电离层探测而开发的预研空间光谱仪器。 由于远紫外波段的特殊性, 仪器所能接收到的信号非常微弱, 因此灵敏度和信噪比就成为了衡量性能的重要指标。 该文根据信号统计检测理论, 在阈值理论的基础上, 提出了计算这种仪器的灵敏度和信噪比的方法。 首先分析了接收信号和系统噪声的概率分布, 然后引入探测概率和虚警概率因子, 从而推导出仪器的灵敏度与信噪比的计算表达式。 根据灵敏度计算和电离层中探测粒子辐射波长的亮度范围, 可知仪器的灵敏度能够满足探测需求。 之后对仪器的信噪比进行了理论计算, 并建立了相关的实验系统进行验证, 结果表明, 由该方法计算出的结果和实验结果之间的误差在允许范围内, 因此是合理的。

An 115-180 nm far ultraviolet limb imaging spectrograph prototype was developed for the detection of the ionosphere. For the particularity of the wavelength band in far ultraviolet, the signals accepted by the instrument are very weak. So the sensitivity and signal-noise-ratio (SNR) are two important performance parameters for the spectrograph. In the present paper, based on the signal statistical detection theory and the threshold detection theory, a method for calculation of the sensitivity and SNR has been proposed. Firstly, the probabilities of the accepted signals and system noises were analyzed. Secondly, the mathematical expressions of sensitivity and SNR of the instrument were deduced by introducing the detection probability factor and the false alarm rate factor. Based on the calculation of the sensitivity and the intensity of the particles radiation wavelengths, it was found that the sensitivity can meet the need of the detection. Finally, the SNR of the instrument were analyzed by using the method, and the coherent experiment was built to prove the results. The error of theoretic calculation and experimental results can be accepted. It indicates that the SNR analysis method is feasible.