We have developed a laser heterodyne spectroradiometer in combination with self-calibrated wavelength modulation spectroscopy based on a software-based lock-in amplifier to observe the atmospheric carbon dioxide (CO2) column absorption near wavelength 1.57 μm in solar occultation mode. This combination facilitates miniaturization of laser heterodyne radiometer. Combined with our developed retrieval algorithm, the atmospheric carbon dioxide column concentration is measured to be 413.7 ± 1.9 ppm, in agreement with GOSAT satellite observation results. This system offers high spectral signal-to-noise ratio of ~333 for the zeroth harmonic (0f) normalized second harmonic (R2f) signal of CO2 transition (R22e), with a measurement averaging time of 8 s, which can be further improved by increasing averaging time in accordance to the Allan deviation analysis for the noise fluctuation. This demonstrates the feasibility of the system for atmospheric investigation and the potential of ground-based, airborne and spaceborne observations for the variation of the global greenhouse gases.

中文翻译：

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激光外差分光辐射计借助自校准波长调制光谱仪进行大气CO2柱吸收测量。

我们开发了一种激光外差光谱仪，结合基于软件的锁定放大器的自校准波长调制光谱仪，可以在太阳掩星模式下观察波长为1.57μm的大气二氧化碳（CO2）柱吸收。这种组合有利于激光外差辐射计的小型化。结合我们开发的检索算法，测得的大气二氧化碳柱浓度为413.7±1.9 ppm，与GOSAT卫星观测结果一致。该系统为CO2跃迁（R22e）的零次谐波（0f）归一化二次谐波（R2f）信号提供〜333的高光谱信噪比，测量平均时间为8 s，根据针对噪声波动的Allan偏差分析，可以通过增加平均时间来进一步改善此效果。这证明了该系统用于大气调查的可行性以及地面，空中和星载观测对全球温室气体变化的潜力。