我国大气污染呈现出区域性和复杂性等特性,开展污染气体区域分布的立体监测,能够及时了解大气环境现状、研究分析影响大气质量的各种因素,指导大气污染控制措施.机载成像差分吸收光谱仪,是目前有效的污染气体区域分布遥感手段之一.该技术观测区域大,覆盖率高,最终可提供精细化的污染气体区域分布资料,实现污染分布及传输的可视化探测.以往机载成像差分吸收光谱仪采用整体式设计,需要占用飞机光学观察窗口,航空搭载需求苛刻、应用受限.为此提出了光纤式机载成像差分吸收光谱仪,采用光纤束传输方式,安装过程中对飞机改装需求小,极大的便利了机上安装和调试,适应了适航设备认证需求.该系统采用特制多芯光纤束结合Littow-offner结构光谱成像系统,具有光谱成像分辨率高、大视场、结构紧凑等优点.在此详细介绍了该设备性能参数,并利用该系统在芜湖市周边开展了区域污染遥感应用.应用过程中,针对光纤式成像差分吸收光谱仪,提出了数据处理算法.对采集到的太阳散射光谱进行反演得到污染气体的斜柱浓度,并利用大气传输模型计算大气质量因子,实现垂直柱浓度转化.最后结合飞机姿态位置信息,快速获取了芜湖市区及其周边上空的NO2、SO2的浓度分布,并进行了区域内污染源快速定位和传输过程分析.从反演结果来看,本次实验NO2垂直柱浓度在实验区域存在4个高值点,SO2垂直柱浓度在实验区域存在2个高值点,高值点附近均存在重工企业,结果与实际情况相符.并结合卫星数据评估二者交叉校验精度,二者呈现正相关,相关性系数为0.77.应用效果验证了光纤式成像差分吸收光谱仪的方案可行性,可为大气污染气体航空遥感技术推广提供参考,同时弥补了地面站点监测在空间尺度上以及卫星遥感在时间尺度上的不足.
Air pollution in China presents regional and complex characteristics.Carrying out stereo monitoring of the regional distribution of polluted gases can help us understand the status quo of the atmospheric environment in a timely manner,study and analyze various factors affecting air quality,and guide air pollution control measures.The airborne imaging differential optical absorption spectroscopy is one of the effective remote sensing methods for the regional distribution of polluted gases.This technology has a large observation area and a high coverage rate,which can provide a detailed regional distribution of polluted gases and realize the visual detection of pollution distribution and transmission.In the past?the airborne imaging differential absorption spectrometer used an overall design that needed to occupy the optical observation window of the aircraft.The optical fiber imaging differential absorption spectrometer introduced in this paper adopts the optical fiber beam transmission method?which needs minimal requirements during installation?greatly facilitates the installation and debugging on the aircraft,and meets the requirements of airworthiness equipment certification.This system uses a special multi-core fiber bundle combined with a Littow-offner structure spectral imaging system,which has the advantages of high spectral imaging resolution?large field of view,and compact structure.The paper introduces the equipment performance parameters in detail,and the verification experiment is carried out using the system around Wuhu City.A data processing algorithm is proposed for the optical fiber imaging differential absorption spectrometer in the application process.In this experiment,the slanted column concentration of polluting gas is obtained by retrieving the collected scattered solar light?and the air quality factor is calculated using the atmospheric radiative transmission model.Then?convert the slanted column concentration into a path-independent vertical column concentration.Finally?the results are displayed on the map combined with the aircraft angles and positions.This equipment can quickly obtain the concentration distribution of NO2 and SO2 over Wuhu City and its surrounding areas realize the rapid location of pollution sources and analyze the transmission process.According to the results?there are 4 high-value points of NO2 vertical column concentration and 2 high-value points of SO2 vertical column concentration in the experimental area.According to the map,there are industrials around the high-value points,and the results are consistent with the actual situation.Finally,we evaluated the precision between satellite data and airborne data.They have a positive correlation with a correlation coefficient of 0.77.The results show that the scheme of optical fiber imaging differential absorption spectrometer is verified?which can provide a basis popularising air pollution gas remote sensing technology and compensate for the shortage on the spatial scale in ground station and the shortage on the time scale in satellite test.