Science objectives of the ozone monitoring instrument

The Ozone Monitoring Instrument (OMI) flies on NASA's Earth Observing System AURA satellite, launched in July 2004. OMI is an ultraviolet/visible (UV/VIS) nadir solar backscatter spectrometer, which provides nearly global coverage in one day, with a spatial resolution of 13 km/spl times/24 km. Trace gases measured include O/sub 3/, NO/sub 2/, SO/sub 2/, HCHO, BrO, and OClO. In addition OMI measures aerosol characteristics, cloud top heights and cloud coverage, and UV irradiance at the surface. OMI's unique capabilities for measuring important trace gases with daily global coverage and a small footprint will make a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change along with Aura's other three instruments. OMI's high spatial resolution enables detection of air pollution at urban scales. Total Ozone Mapping Spectrometer and differential optical absorption spectroscopy heritage algorithms, as well as new ones developed by the international (Dutch, Finnish, and U.S.) OMI science team, are used to derive OMI's advanced backscatter data products. In addition to providing data for Aura's prime objectives, OMI will provide near-real-time data for operational agencies in Europe and the U.S. Examples of OMI's unique capabilities are presented in this paper.     

The ozone monitoring instrument

The Ozone Monitoring Instrument (OMI) flies on the National Aeronautics and Space Administration's Earth Observing System Aura satellite launched in July 2004. OMI is a ultraviolet/visible (UV/VIS) nadir solar backscatter spectrometer, which provides nearly global coverage in one day with a spatial resolution of 13 km/spl times/24 km. Trace gases measured include O/sub 3/, NO/sub 2/, SO/sub 2/, HCHO, BrO, and OClO. In addition, OMI will measure aerosol characteristics, cloud top heights, and UV irradiance at the surface. OMI's unique capabilities for measuring important trace gases with a small footprint and daily global coverage will be a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change. OMI's high spatial resolution is unprecedented and will enable detection of air pollution on urban scale resolution. In this paper, the instrument and its performance will be discussed.     

Band residual difference algorithm for retrieval of SO/sub 2/ from the aura ozone monitoring instrument (OMI)

The Ozone Monitoring Instrument (OMI) on EOS/Aura offers unprecedented spatial and spectral resolution, coupled with global coverage, for space-based UV measurements of sulfur dioxide (SO/sub 2/). This paper describes an OMI SO/sub 2/ algorithm (the band residual difference) that uses calibrated residuals at SO/sub 2/ absorption band centers produced by the NASA operational ozone algorithm (OMTO3). By using optimum wavelengths for retrieval of SO/sub 2/, the retrieval sensitivity is improved over NASA predecessor Total Ozone Mapping Spectrometer (TOMS) by factors of 10 to 20, depending on location. The ground footprint of OMI is eight times smaller than TOMS. These factors produce two orders of magnitude improvement in the minimum detectable mass of SO/sub 2/. Thus, the diffuse boundaries of volcanic clouds can be imaged better and the clouds can be tracked longer. More significantly, the improved sensitivity now permits daily global measurement of passive volcanic degassing of SO/sub 2/ and of heavy anthropogenic SO/sub 2/ pollution to provide new information on the relative importance of these sources for climate studies.     

First results from the OMI rotational Raman scattering cloud pressure algorithm

We have developed an algorithm to retrieve scattering cloud pressures and other cloud properties with the Aura Ozone Monitoring Instrument (OMI). The scattering cloud pressure is retrieved using the effects of rotational Raman scattering (RRS). It is defined as the pressure of a Lambertian surface that would produce the observed amount of RRS consistent with the derived reflectivity of that surface. The independent pixel approximation is used in conjunction with the Lambertian-equivalent reflectivity model to provide an effective radiative cloud fraction and scattering pressure in the presence of broken or thin cloud. The derived cloud pressures will enable accurate retrievals of trace gas mixing ratios, including ozone, in the troposphere within and above clouds. We describe details of the algorithm that will be used for the first release of these products. We compare our scattering cloud pressures with cloud-top pressures and other cloud properties from the Aqua Moderate-Resolution Imaging Spectroradiometer (MODIS) instrument. OMI and MODIS are part of the so-called A-train satellites flying in formation within 30 min of each other. Differences between OMI and MODIS are expected because the MODIS observations in the thermal infrared are more sensitive to the cloud top whereas the backscattered photons in the ultraviolet can penetrate deeper into clouds. Radiative transfer calculations are consistent with the observed differences. The OMI cloud pressures are shown to be correlated with the cirrus reflectance. This relationship indicates that OMI can probe through thin or moderately thick cirrus to lower lying water clouds.     

Ozone monitoring instrument calibration

The Ozone Monitoring Instrument (OMI) was launched on July 15, 2004 on the National Aeronautics and Space Administration's Earth Observing System Aura satellite. The OMI instrument is an ultraviolet-visible imaging spectrograph that uses two-dimensional charge-coupled device detectors to register both the spectrum and the swath perpendicular to the flight direction with a 115/spl deg/ wide swath, which enables global daily ground coverage with high spatial resolution. This paper presents the OMI design and discusses the main performance and calibration features and results.     

Total ozone from the ozone monitoring instrument (OMI) using the DOAS technique

This paper describes the algorithm for deriving the total column ozone from spectral radiances and irradiances measured by the Ozone Monitoring Instrument (OMI) on the Earth Observing System Aura satellite. The algorithm is based on the differential optical absorption spectroscopy technique. The main characteristics of the algorithm as well as an error analysis are described. The algorithm has been successfully applied to the first available OMI data. First comparisons with ground-based instruments are very encouraging and clearly show the potential of the method.     

Algorithm for NO/sub 2/ vertical column retrieval from the ozone monitoring instrument

We describe the operational algorithm for the retrieval of stratospheric, tropospheric, and total column densities of nitrogen dioxide (NO/sub 2/) from earthshine radiances measured by the Ozone Monitoring Instrument (OMI), aboard the EOS-Aura satellite. The algorithm uses the DOAS method for the retrieval of slant column NO/sub 2/ densities. Air mass factors (AMFs) calculated from a stratospheric NO/sub 2/ profile are used to make initial estimates of the vertical column density. Using data collected over a 24-h period, a smooth estimate of the global stratospheric field is constructed. Where the initial vertical column densities exceed the estimated stratospheric field, we infer the presence of tropospheric NO/sub 2/, and recalculate the vertical column density (VCD) using an AMF calculated from an assumed tropospheric NO/sub 2/ profile. The parameters that control the operational algorithm were selected with the aid of a set of data assembled from stratospheric and tropospheric chemical transport models. We apply the optimized algorithm to OMI data and present global maps of NO/sub 2/ VCDs for the first time.     

基于MAX-DOAS的对流层NO2和气溶胶光学厚度遥测反演

随着全球工业化速度加快和人口的增多,大气环境问题日益突出,NO2和气溶胶在大气化学中扮演着重要的角色。地基多轴差分吸收光谱技术（MAX-DOAS）基于被动DOAS原理,近年来已成功应用于大气痕量气体柱浓度和气溶胶光学厚度（AOD）测量方面。本文基于被动DOAS算法对合肥秸秆燃烧期间NO2柱浓度以及气溶胶光学厚度进行了观测,并把对流层柱浓度和臭氧监测仪(Ozone Monitoring Instrument, OMI)结果进行对比;测量的气溶胶光学厚度和太阳光度计（CE318）进行了对比。结果表明,MAX-DOAS测量结果要高于卫星值,11月6日MAX-DOAS测量NO2柱浓度日均值为OMI的1.9倍;二者在无云条件下一致性较好;MAX-DOAS反演AOD和太阳光度计结果相关性在0.9以上。     

Comparison of ice-sheet satellite altimeter retracking algorithms

The NASA and ESA retracking algorithms are compared with an algorithm based upon a combined surface and volume (S/V) scattering model. First, the S/V, NASA, and ESA algorithms were used to retrack over 1.3 million altimeter return waveforms from the Greenland and Antarctic ice sheets. The surface elevations from the S/V algorithm were compared with the elevations produced by the NASA and ESA algorithms to determine the relative accuracy of these algorithms when subsurface volume scattering occurs. The results show that the ESA_25% algorithm produced slightly higher surface elevations than the S/V algorithm. The NASA retracking algorithm produced lower surface elevations than the SN retracking algorithm, with average differences ranging from -0.3 to -0.9 m. The lower NASA elevations can only account for a portion of previously reported differences between altimeter and geoceiver surface elevations, suggesting that the remainder is probably due to orbital differences. Next, by analyzing several thousand satellite crossover points from the Greenland and Antarctic ice sheets, the author estimated the repeatability of the surface elevations derived from the different retracking algorithms. The elevations derived from the ESA_25% and S/V algorithm had the smallest standard deviations for the crossover differences for a time period where no significant change in surface elevation should occur. The NASA standard deviations were approximately 0.2 m larger than those from the ESA_25% and S/V algorithm, which represents an average increase in error of approximately 0.5 m in the datasets. Since previous ice-sheet growth estimates have been based upon the elevations produced by the NASA retracking algorithm, further work needs to be conducted to determine if the ESA_25% or S/V retracking algorithms produce growth estimates that are significantly different from the previous estimates     

Growth of the Greenland ice sheet: a performance assessment ofaltimeter retracking algorithms

The authors compare the performance of different altimeter retracking algorithms for measuring ice sheet elevations and growth rates. The results show that the threshold, ESA, and S/V retracking algorithms produce growth rates that are 30-55% smaller than those produced by the NASA algorithm. Based upon a comparison of crossover-point standard deviations, the analysis indicates that the surface elevation estimates produced by these algorithms are more repeatable than the NASA surface elevations. An analysis of the NASA algorithm shows that a mixing of its 5 and 9 parameter functional fits on the crossover-point altimeter waveforms occurs in over 70% of the crossover data. The mixing of the functional fits is shown to reduce the repeatability of the NASA elevations and this may be responsible for the larger estimates of ice sheet growth produced by the NASA retracking algorithm. The extremely close agreement between the standard deviations and the growth-rate estimates from the threshold, ESA, and S/V retracking algorithms: lead the authors to conclude that 0.10 m/yr is a more accurate estimate of the growth of the Greenland ice sheet from 1978-1987 (south of 72°N)     

OMI very fast delivery and the Sodankyla/spl uml/ Satellite Data Centre

The Ozone Monitoring Instrument (OMI) operates onboard the National Aeronautics and Space Administration's Earth Observing System Aura satellite, which was launched in July 2004. Like its sister spacecraft Terra and Aqua, Aura's capabilities include direct broadcast (DB), i.e., the ability to broadcast data at the same time as they are being measured and stored in the spacecraft's memory for later transmission to Earth. The Finnish Meteorological Institute's Satellite Data Centre at Sodankyla/spl uml/ in Finnish Lapland is exploiting this capability to receive OMI data while Aura is in sight of the receiver, which enables nearly immediate production of OMI data products for a region that includes a large part of Europe, stretching from the North Pole to the Italian Alps. The current OMI Very Fast Delivery (VFD) products include maps of surface UV-B, ozone columns, and cloud coverage.     

二茂铁基复合推进剂红外/紫外低特征信号应用研究

针对精确制导武器隐身性能的需要,首先利用模拟的火箭发动机喷口结构测试了HTPB复合推进剂的红外和紫外特征信号,然后分析了二茂铁作为一种消光材料对HTPB复合推进剂火焰在红外波段和紫外波段的辐射信号衰减能力。同时,测试了二茂铁消光材料对火箭发动机的喷口温度的影响。结果表明,利用硝酸钾、硫和酚醛树脂为基础的烟火药配方提供初始能量,促使二茂铁快速汽化,并在推进剂火焰外形成薄层作为消光材料,对红外波段和紫外波段具有明显的遮蔽吸收作用,衰减率可以达到50%以上。得出二茂铁含量为30%时在710~3 500 cm-1波段,对于HTPB复合推进剂的红外辐射衰减效果最好;含量高于50%时对于HTPB复合推进剂的2 400~3 500 cm-1波段的红外辐射强度有所增加。     

紫外天体模拟器辐射参数现场校准技术

紫外天体模拟器为空间探测工程中紫外有效载荷的重要测试和仿真设备。为了解决紫外天体模拟器辐射参数现场校准存在的难题,建立一套便携式紫外天体模拟器辐射参数现场校准装置,实现紫外模拟器瞬态辐射参数校准和高灵敏度辐射参数校准。校准参数包括光谱辐亮度、光谱辐照度等。校准的光谱范围为200~400 nm,该装置的建立完善国内的紫外校准技术研究体系,填补我国现场计量型的紫外标准的空白。     

基于6S模型从MODIS图像反演陆地上空大气气溶胶光学厚度

本文描述了一种以MODIS图像反演陆地大气气溶胶光学厚度的算法，它是基于6S大气辐射传输模型计算的查找表(LUT)，并利用地面的暗目标自动反演陆地大气气溶胶光学厚度的方法。利用该算法给出了我国江西省中部地区的2001年10月19日550nm波长的平均大气气溶胶光学厚度(0．19)，这与从国家气象档案馆获得的该地区的气象能见度计算结果有较好的一致性。     

星载臭氧垂直探测仪地外太阳紫外光谱测量

介绍了国内外星载太阳紫外光谱辐射计的研究进展,对我国自行研制的星载臭氧垂直探测仪的结构和功能进行了简介。它是一种小型化、高精度的紫外-真空紫外光谱辐射计,可在轨测量获得160～400nm地外太阳绝对光谱。给出了星载臭氧垂直探测仪实测的地外太阳紫外光谱并对其精度进行了分析。误差分析表明,160～250nm地外太阳绝对光谱的测量不确定度为±6.4%;250～400nm为±5.2%。将臭氧垂直探测仪在轨观测结果与国际同类仪器进行了比对,一致性优于±5%。     

Aerosol properties over bright-reflecting source regions

Retrieving aerosol properties from satellite remote sensing over a bright surface is a challenging problem in the research of atmospheric and land applications. In this paper we propose a new approach to retrieve aerosol properties over surfaces such as arid, semiarid, and urban areas, where the surface reflectance is usually very bright in the red part of visible spectrum and in the near infrared, but is much darker in the blue spectral region (i.e., wavelength <500 nm). In order to infer atmospheric properties from these data, a global surface reflectance database of 0.1/spl deg/ latitude by 0.1/spl deg/ longitude resolution was constructed over bright surfaces for visible wavelengths using the minimum reflectivity technique (e.g., finding the clearest scene during each season for a given location). The aerosol optical thickness and aerosol type are then determined simultaneously in the algorithm using lookup tables to match the satellite observed spectral radiances. Examples of aerosol optical thickness derived using this algorithm over the Sahara Desert and Arabian Peninsula reveal various dust sources, which are important contributors to airborne dust transported over long distances. Comparisons of the satellite inferred aerosol optical thickness and the values from ground-based Aerosol Robotic Network (AERONET) sun/sky radiometer measurements indicate good agreement (i.e., within 30%) over the sites in Nigeria and Saudi Arabia. This new algorithm, when applied to Moderate Resolution Imaging Spectroradiometer (MODIS), Sea-viewing Wide Field of view Sensor (SeaWiFS), and Global Imager (GLI) satellite data, will provide high spatial resolution (/spl sim/1 km) global information of aerosol optical thickness over bright surfaces on a daily basis.     

适用于紫外光通信的延迟判决均衡算法

为了消除紫外光通信过程中强烈散射所引起的码间干扰，采用一种带信道估计的最小均方误差-最大似然估计(LMS-MLE)延迟判决均衡算法进行了理论分析和仿真验证。通过选取合适的判决延迟深度来调整LMS自适应滤波器抽头系数进行信道跟踪，获取新的信道估计向量，最后利用MLE均衡算法得到最优序列输出。结果表明, 该算法可以明显提升紫外光通信系统的性能，在没有提高复杂度的情况下，性能接近最优MLE均衡算法，并且可以实现信道跟踪, 紫外光通信中算法的最佳延迟量取值为20。这一结果对紫外光通信性能提升以及MLE均衡器的工程实现是有帮助的。     

基于OMI卫星数据结合车载DOAS技术修正的NOx排放通量估算

与搭载在EOS AURA卫星上的OMI（Ozone Monitoring Instrument）探测器相比,由车载被动差分吸收光谱（differential optical absorption spectroscopy,DOAS）技术获得的NO2柱浓度数据空间分辨率更高,因而能够更准确的反映出NO2时空分布情况,利用OMI NO2 Level2数据产品重构2013年6月石家庄及周边区域的NO2柱浓度分布,结合风场数据分析NO2柱浓度沿风场方向的空间分布,同时,使用车载被动DOAS系统对西南通道即石家庄-保定-北京路段进行走航观测,获取车载DOAS NO2柱浓度分布数据,使用指数修正高斯（exponentially-modified Gaussian,EMG）拟合方式,分别拟合OMI NO2 数据和经过地基DOAS数据修正后的OMI NO2 数据得到NOx排放通量分别为195.8 mol/s、160.6 mol/s。经过地基DOAS数据修正的NOx排放量小于卫星估算值,可能是由于卫星的空间分辨率较低导致的。     

Path loss of non-line-of-sight ultraviolet light communication channel in polydisperse aerosol systems

Performance of non-line-of-sight (NLOS) ultraviolet (UV) communication is closely related with the system geometry, the communication range, and the atmospheric parameters. In this paper, we implement a full numerical analysis of the relations of path loss of NLOS UV communication with these factors using the Mie scattering theory and the Monte-Carlo method. In the numerical simulations, the actual polydisperse aerosol systems are used as the transmission medium. Since for the actual aerosol systems the atmosphere conditions may be similar within a short period, the path loss may be exclusively determined by the atmosphere visibility. Hence, we build a relation between the path loss of the communication channel and the atmosphere visibility. Simulation results reveal that for a relatively small communication range, the path loss increases with the visibility. On the other hand, low elevation of the transceiver may reduce the path loss. Our simulation results are useful for the evaluation of performance of the real NLOS UV communication systems.