用于大气遥感的远紫外光栅色散成像光谱仪的研究

远紫外光栅色散型成像光谱仪在空间大气遥感领域主要用于电离层、热层、极光和辉光的探测。文章根据临边与天底结合的大气成像光谱探测原理,提出了探测方案,设计了适用于远紫外波段的光栅色散型成像光谱仪的两种光学系统,并选择了平面光栅结构进行研制集成,在国内首次获得了原理样机。样机工作波段为120～180nm,望远系统采用离轴抛物镜,光谱成像系统采用改进型的Czerny-Turner结构,探测器使用远紫外响应背照型增强CCD。搭建了相应的实验系统对样机的基本性能参数进行了测试,测得光谱分辨率约为2nm,空间分辨率0.5mrad。这种远紫外光栅色散型成像光谱仪的研究对完善我国大气遥感事业具有重要的研究与应用价值。     

向短波红外延伸的微光夜视技术及其应用

对传统的微光像增强器与向短波红外延伸的InGaAs光阴极像增强器进行了比较,分析了通过调节组分而使响应波段覆盖夜天光辐射主要波段的InGaAs材料特性,揭示了以InGaAs半导体材料为光阴极的像增强器将在夜间具有更高的量子效率和响应度。介绍了InGaAs器件技术的国内外研究现状,InGaAs光阴极微光器件在短波红外波段的辐射响应是传统像增强器的100~1 000倍,InGaAs全固态探测器可在0.4 m~1.7 m宽光谱成像,在0.9 m~1.7 m范围的量子效率大于80%,表明该器件在激光探测、远距离定位与跟踪、情报侦察、夜间辅助驾驶等方面可以获得广泛应用。     

紫外像增强器光谱响应特性测量方法研究

为了能及时测量自制紫外像增强器的光谱响应特性，设计了一套简便的测量紫外像增强器光谱响应的系统。该系统由专用光源室、光栅光谱仪、直流稳压电源、皮安电流计4部分构成。用光栅光谱仪配套软件直接读出光源每个波长对应的辐射功率；用皮安电流计直接测量出各个波长的光照射光阴极时光阴极产生的光电流，然后求出这2个比值并用Microsoft Excel 2003进行处理，得到光电流与波长变化的曲线，即相对光谱响应曲线。从曲线可以看出，该紫外像增强器的光谱响应范围为200nm～340nm，峰值响应在270nm附近，表明该紫外像增强器具有日盲特性。测试结果表明：系统不确定度＜10%。     

一种响应波长在120 nm～200 nm的紫外像增强器

介绍了一种响应波长在120 nm～200 nm的紫外像增强器。它是采用CsI直接蒸镀在MCP上形成反射式光电阴极,用MgF₂作为输入窗口,光纤面板作为输出窗的真空光电器件。管型采用近贴聚焦结构,从而使得弥散和像差得以减小,具有高的量子效率和空间分辨率。在静态测试中,空间分辨率可以达到18 lp/mm。该紫外像增强器可用于空间科学和天文观测领域。     

紫外增强薄膜发射光谱测量中的倍波现象分析

紫外探测技术足继激光和红外探测技术之后发展起来的又一军民两用光电探测技术,在普通探测器件光敏面镀上将紫外波段的光转化为可见波段的光的变频薄膜是增强光电探测器紫外响应的主要技术.文章用"旋涂法"制备成像器件紫外增强薄膜.在对紫外增强薄膜的量子转化效率进行测量分析的实验过程中用SP1702紫外可见光栅光谱仪对薄膜的紫外变频效率进行分析,在激发光源为260和280nm时变频薄膜的发射光谱在520和560 nm附近有较明显的波峰.结合光栅光谱仪的工作原理,对该现象进行了理论分析,得出520和560 nm附近的波峰并非变频薄膜受激发发出的光波,而是光谱测量中产生的倍波现象.从分离重级光谱的角度没计了光谱分级器,以消除光谱测鼍中倍波现象的影响.     

紫外像增强器辐射灵敏度测量系统

紫外像增强器是紫外探测系统的核心器件，是一种电真空成像器件，可将微弱的紫外光图像转换并增强为肉眼可见、亮度可见的光图像，其研制与应用是微光夜视技术的重要发展方向。辐射灵敏度是评价紫外像增强器的重要参数，直接决定了紫外探测系统的性能。介绍了紫外像增强器辐射灵敏度的测量原理，采用紫外辐射光源、光栅单色仪系统、测试暗箱、微电流计、计算机及测量软件组建了辐射灵敏度测量系统。对3只紫外像增强器在260 nm、280 nm及320 nm波长下的辐射灵敏度进行了测量，并分析了其测量不确定度。该测量系统的建立，将辐射灵敏度测量系统的光谱范围拓展至200 nm～400 nm，弥补了现有系统的不足，具有广泛的应用前景。     

空间高层大气遥感远紫外成像光谱仪的光学系统

空间高层大气遥感远紫外成像光谱仪主要用于观测高层大气中的远紫外辐射和实现对其内部中尺度现象成像的功能。目前我国该类的相关仪器研究基础还比较薄弱,针对这种情况,在光学系统设计的角度上给出了一种适用于130～180nm波段探测的光学系统方案。该成像光谱仪光学系统以离轴抛物镜为物镜,串联Wadsworth结构为成像光谱系统;这种串联Wadsworth成像光谱系统采用离轴抛物镜做准直镜,分光器件为平面光栅和球面光栅串联,实现二次色散,同时球面光栅起到聚焦成像作用;在像差理论的基础上,对该结构的光程函数和各像差进行了分析,获得了改进结构的宽波段完善成像条件。针对低轨空间探测应用要求设计了相关改进型Wadsworth结构成像光谱仪光学系统,设计结果证明系统像差得到了充分校正,在奈奎斯特频率(20lp/mm)下全视场全波段调制传递函数值在0.6以上。该优化结构同时具备高空间分辨率和高光谱分辨率,性能优越。     

一种新型真空型紫外成像探测器

针对紫外告警的关键元器件——紫外探测器，简述了紫外告警的特点及发展，紫外辐射的大气传输特性和紫外探测器的发展。详细介绍了一种新型响应波段为105nm～300nm的真空型紫外成像探测器，其光电阴极具有“日盲性”，管型采用近贴聚焦结构，从而使得弥散和像差得以减小。探测器读出系统有光耦合读出和电耦合读出2种读出方法：光耦合读出系统能实时响应；电耦合读出灵敏度高，分辨力强，探测距离远。采用自动门控BSP电源，可实现大动态范围探测，并对光电阴极和微通道板起到保护作用。     

透射式变掺杂GaAs光电阴极研究

为了将变掺杂GaAs材料应用于微光像增强器,开展了透射式变掺杂GaAs光电阴极实验研究,制备了2种反转结构透射式变掺杂GaAs光电阴极。测试了玻璃粘接前后GaAs光电阴极载流子浓度变化,发现高温粘接后载流子浓度增加现象。通过测试高温激活的透射式变掺杂GaAs光电阴极发现,在450 nm～550 nm波段内,变掺杂GaAs光电阴极仍然具有较高的光谱响应。     

一种测量动态光谱特性的新方法

根据光学薄膜在制备过程中测试动态光谱特性的需要,我们研制了一种测试动态光谱特性的装置。该装置工作在400nm—700nm可见光谱范围内,光谱扫描周期为二十毫秒。该装置利用国产紫外增强型硅靶摄象管作为光电转换器件,这种管子的短波段响应灵敏度较高,对溴钨灯光源的辐射特性有一定的补偿作用。多色仪采用Curney—Turner水平对称型光栅分光系统。摄象管靶面置于多色仪象方焦平面上。     

Ozone profiles retrieval from SCIAMACHY Chappuis-Wulf limb scattered spectra using MART

The Scanning Imaging Absorption spectroMeter for Atmospheric ChartographY(SCIAMACHY) instrument,launched on the Envisat satellite in March 2002,measures the earthshine radiance,simultaneously from the ultraviolet(UV) to the near infrared(NIR),in the three viewing geometries:nadir,limb,and occultation.These measurements are used to retrieve both the total amount and vertical profiles of a large number of atmospheric constituents.In this paper,stratospheric ozone profiles between 15 and 40 km altitude are ret...     

空间遥感仪器探测器工作温度对信噪比的影响分析

临边观测是一种新的空间大气遥感探测方式,但大气散射光谱辐射随临边高度的增加而迅速减弱。所以信噪比是临边遥感仪器的关键性能指标。在深入分析典型仪器信号光谱辐射传输特性和噪声来源的基础上建立了随探测器制冷温度变化的信噪比模型,并在一台临边遥感光谱仪原理样机上模拟试验验证了空间环境下临边高度70km处的信噪比,理论分析和实验结果一致表明:探测器制冷到一定温度时,仪器的信噪比达到了一个极限值。在综合考虑功耗、散热等问题的基础上获得了探测器的最优工作温度。     

Measurement of water-leaving radiance on smooth water surfaces at different viewing angles using high-resolution spectroradiometer

This letter describes a method for calculating water-leaving radiance on smooth surfaces at differentangles based on Fresnel law and the polarized measurements using an ASD FS3 spectroradiometer. The spectroradiometer is mounted on a goniometer so that it views the water surface from a height of severaldecimeters at different viewing angles through a linear polarizing filter. The incident angles equal theviewing angles. The water-leaving radiance spectra acquired by other methods are compared with the polarized measurements from the smooth water surface, and the radiance spectra obtained by the proposedmethod are found to be consistent with the results of the reference methods. The current study provides another effective technique for measuring water-surface reflectance via remote sensing. Moreover, the method does not avoid the sun glint during the detection of water-leaving radiance in cases where the viewing geometric position is clear.     

Adjoint sensitivity analysis of radiative transfer equation: 2. Applications to retrievals of temperature in scattering atmospheres in thermal IR

An approach to formulation of inversion algorithms for thermal sounding in the case of scattering atmosphere based on the adjoint equation of radiative transfer (Ustinov, JQSRT 68 (2001) 195, referred to as Paper 1 in the main text) is applied to temperature retrievals in the scattering atmosphere for the nadir viewing geometry. Analytical expressions for the weighting functions involving the integration of the source function are derived. Temperature weighting functions for a simple model of the atmosphere with scattering are evaluated and convergence to the case of pure atmospheric absorption is demonstrated. The numerical experiments on temperature retrievals are carried out to demonstrate the validity of the expressions obtained.     

影响光谱辐亮度标定因素的分析

在利用漫反射板标定光谱辐亮度的实验装置中,标准灯完全可以近似为点光源。通过对进入光谱仪的辐射通量的数值积分,可以对应求出仪器的实测光谱辐亮度的计算公式。计算表明,实测光谱辐亮度并不等于漫反射板表面的光谱辐亮度,而有一个随标定条件变化的微小差值。通过计算,对光谱仪与漫反射板的距离、光谱仪入射挟缝的光轴与漫反射板法线的夹角以及标准灯与漫反射板的距离等影响光谱仪标定的因素进行分析,得到了最佳的标定条件。讨论了理想标定情况、光谱仪视场趋于一点的极限情况和采用实际的双向反射分布函数已知的漫反射板标定时,实测光谱辐亮度的计算情况。     

非平衡大气辐射强度与透过率的Line-By-Line计算模式

导出了非局域热力学平衡(NLTE)大气辐射强度与透过率的基本公式,以及NLT和LTE的线强、光学厚度和透过率的关系。假设转动能级是热力学平衡(LTE)的,建立了一个精确的Line-by-LineNLTE辐射强度与透过率的有效算法来计算较高层行星大气红外活跃样品的辐射强度。计算了地球大气¹⁶O₃9.6μm带在白天、夜晚和NLTE、LTE条件下的临边光谱辐射强度、线积分辐射强度、带积分辐射强度和合成光谱辐射强度,揭示了NLTE辐射强度对LTE辐射强度有显著而重要的偏离。     

Methods for estimating the similarity parameter of clouds from internal measurements of the scattered radiation field

The similarity parameter is a combination of the single scattering albedo and the scattering asymmetry factor and can be used in conjunction with particle-size information to estimate the fractional absorption of a cloud layer. Methods are presented for estimating the parameter without estimating the optical thickness of the cloud or the ground albedo, but radiance measurements must be made at two elevations deep within the cloud layer. If the radiance data is for a sufficient number of directions, then one method can be used to give the parameter without using any correlation of the parameter with properties of the cloud. With the appropriate correlations, the parameter can be obtained using either the mean radiance and net flux or the radiance in only the zenith and nadir directions. The methods are based on an asymptotic transport theory and are shown to be a special case of more general transport results.     

Effect of the reflection of underlying surface on sky radiance distribution

Sky radiance might be influenced by the multiple reflectance between the earth's albedo surface and the atmosphere. Based on the Lambert's law and the radiative transfer equation (RTE), a model is developed to calculate the additional sky radiance at wavelengths of 0.4-3 μm due to the reflectance contribution of the underlying surface. The iterative method is used to calculate sky radiance without the reflectance from underlying surface. The hybrid modified delta-Eddington approximation is used to compute the atmospheric reflection of the radiation from the earth's surface. An interaction factor is introduced to deal with the multiple reflectance between the atmosphere and the underlying surface. The sky radiance increment is evaluated for some different albedos of the earth's surface. The results show that the sky radiance increment rises rapidly while viewing zenith angle is near to 90°, and the larger the albedo of the earth's surface is, the more obvious this effect appears.     

Atmospheric weighting functions and surface partial derivatives for remote sensing of scattering planetary atmospheres in thermal spectral region: general adjoint approach

An approach to formulation of inversion algorithms for remote sensing in the thermal spectral region in the case of a scattering planetary atmosphere, based on the adjoint equation of radiative transfer (Ustinov (JQSRT 68 (2001) 195; JQSRT 73 (2002) 29); referred to as Papers 1 and 2, respectively, in the main text), is applied to the general case of retrievals of atmospheric and surface parameters for the scattering atmosphere with nadir viewing geometry. Analytic expressions for corresponding weighting functions for atmospheric parameters and partial derivatives for surface parameters are derived. The case of pure atmospheric absorption with a scattering underlying surface is considered and convergence to results obtained for the non-scattering atmospheres (Ustinov (JQSRT 74 (2002) 683), referred to as Paper 3 in the main text) is demonstrated.     

硫酸钡漫反射板在250～400 nm光谱辐射亮度标定中的应用研究

表面喷涂硫酸钡的漫反射板正入射时是最接近朗伯特性的用于标定光谱辐射亮度的实用漫反射板。通过实验测量硫酸钡漫反射板 2 5 0～ 4 0 0nm的半球反射率和双向反射分布函数表明 ,实测的双向反射分布函数与假定漫反射板为朗伯表面根据测量的半球反射率计算的双向反射分布函数的相对差值为 6 7% ,实测的双向反射分布函数随散射角的变化可达 2 8%。为提高光谱辐射亮度标定的准确性 ,考虑双向反射分布函数的微小变化和漫反射板上的光谱辐射照度的不均匀性 ,通过对光谱仪视场内每一小面元积分 ,最后可精确求得所测光谱辐射亮度 ,并标定光谱仪的光谱辐射亮度