Remote Sensing of the Vertical Ozone Profile Using A Tunable CO2 Sideband Laser Heterdyne Spectrometer

一台连续可调且非常紧凑的中红外(9-12微米)二氧化碳边带激光光谱仪是在先前获得美国国家科学基金资助(ATM-9011067)的情况下开发的。该仪器已用于获得NH3分子的吸收谱线位置、谱线强度、谱线宽度和频移的准确数据。本项目将研究该激光器在平流层臭氧和硝酸遥感中的应用。该技术的开发还将扩展到其他平流层分子，如CF2Cl2(Frcon-12)。这项为期两年的研究计划将通过使用可调谐边带CO2激光器作为本地振荡器的外差辐射计进行现场测量，获得这些物种的定量垂直浓度分布。现场测量将通过使用现有模型并与现有垂直剖面进行比较来进行分析。将进行一项平行研究，以在受控的实验室条件下测量O2的临界线形参数。在这项工作中，可调谐边带激光光谱仪将在模拟平流层条件下提供足够分辨率的直接吸收测量，以获得所需的谱线参数。在第一年，将设计、组装和校准一个由太阳跟踪器、光合成器、本机振荡器、光电倍增器、射频滤光片和信号处理器组成的外差辐射计系统。特别是通过与黑体辐射的外差作用研究边带激光器的噪声特性，探索降低幅度和相位噪声的可能方法。目标是接近短噪声限制的性能，从而实现外差系统的最大信噪比。同时，将建立和校准用于输送和分析混合气体的系统。在第二年，将在平流层条件下以极高的分辨率(+0.00001 cm-)进行O2、HNO3和CF2Cl2的实验室吸收测量，以获得线形参数与分析物浓度之间的准确关联。将利用新获得的线形参数同时进行现场测量和分析。将开发一个模式，该模式将产生在15至50公里之间的准确垂直臭氧浓度分布。模式的最终应用在于解释与平流层臭氧层有关的动力学和化学。

A continuously tunable and very compact mid-infrared (9-12 um) CO2 sideband laser spectrometer was developed under prior a NSF grant (ATM-9011067). This instrument has been used to obtain accurate data on absorption line positions, line strengths, line width and frequency shift of NH3 molecules. The application of this laser for remote sensing of stratospheric ozone (O3) and HNO3 will be investigated in this project. Development of the technique will also be extended to other stratospheric molecules such as CF2Cl2 (Frcon-12). This two year year research program will obtain quantitative vertical concentration profiles of these species by conducting the field measurements using a heterodyne radiometer with the tunable sideband CO2 laser as a local oscillator. The field measurements will be analyzed by using existing models and comparing them with existing vertical profiles. A parallel study will be performed to measure the critical line shape parameters for O2 under controlled laboratory conditions. In this effort, the tunable sideband laser spectrometer will provide direct absorption measurements under simulated stratospheric conditions with sufficient resolution to obtain the desired spectroscopic line parameters. In the first year, a heterodyne radiometer system consisting of a solar- tracker, optical combiner, a local oscillator, a photomixer, RF filter band and signal processor will be designed, assembled and calibrated. In particular, noise characteristics of the sideband laser will be studied by heterodyining with blackbody radiation and potential methods to reduce the amplitude and phase noise will be explored. The goal is to approach short-noise- limited performance and thereby achieve maximum signal to noise ratio for the heterodyne system. In parallel, a system for delivering and analyzing gas mixtures will be constructed and calibrated. During the second year, laboratory absorption measurements of O2, HNO3 and CF2Cl2 will be perfo rmed with extremely high resolution (+0.00001 cm-) under stratospheric conditions to obtain accurate correlations between line shape parameters and analyte concentrations. Field measurements will be conducted and analyzed simultaneously utilizing the newly acquired line shape parameters. A model which yields an accurate vertical ozone concentration profile between 15 to 50 km will be developed. The ultimate application for the model lies in the interpretation of the dynamics and chemistry related to the stratospheric ozone layer.