比值法光学遥感器机上辐射定标的研究

本文在简要介绍光学遥感器各种机上辐射定标方法的基础上,着重叙述了“太阳＋漫射白板＋比值辐射计”的机上定标方案。最后结合自行设计的比值辐射计及其测试结果对该系统的辐射定标精度进行了分析。     

航天遥感器的辐射灵敏度模型

辐射灵敏度表明遥感器对输入信号的响应能力,辐射灵敏度的分析包括辐射灵敏度的计算以及辐射灵敏度的不确定性分析。本文提出航天遥感器辐射灵敏度的分析模型,在模型中给出辐射灵敏度的计算方法,同时,所有相关参数的不确定性均已包含于辐射度灵敏度模型中,允许对其进行误差分析。最后,对一种中分辩率成像光谱仪的辐射灵敏度性能进行了分析和计算。     

比值法光学遥感器机上辐射定标的研究

本文在简要介绍光学遥感器各种机上辐射定标方法的基础上, 着重叙述了“太阳＋ 漫射白板＋ 比值辐射计”的机上定标方案。最后结合自行设计的比值辐射计及其测试结果对该系统的辐射定标精度进行了分析。     

航空遥感器主次镜一次像面补偿检验CGH研究

航空遥感作为一种多功能综合性探测技术,在资源探索、区域监测和环境探测等多种行业中被广泛使用。遥感器作为整个技术的核心部分,对其探测的精度和性能的稳定性有着严格的要求,所以遥感器的总体装配过程成为了关键步骤,其中,对主次镜一次像面的补偿检验就显得尤为重要。本文运用计算机全息图技术,针对此遥感器的光机系统结构参数设计出符合相应要求的补偿元件,给出设计图,同时对遥感器的主次镜一次像面进行补偿检验,确保了每一个装调过程的质量能满足光学设计要求的技术指标和精度,给出了相应的实验数据。在此基础上,运用精度理论知识对CGH补偿器制作的误差及一次像面补偿检验的系统误差进行了详尽的讨论和分析,并给出了分析结果。     

气象辐射计量检测用太阳模拟器性能分析

气象辐射计量检测用太阳模拟器是对气象辐射观测仪表-太阳总辐射表进行质量考核的一个重要检测设备,其性能直接影响总辐射表的考核质量。在对太阳模拟器的结构组成和工作原理的论述基础上,重点了研究了太阳模拟器的光谱匹配度、辐照强度及调节范围、辐照不稳定度、辐照不均匀度和光束准直性等性能指标的测试方法,并根据大量的试验数据对其性能进行了分析。采用滤光片对氙灯光谱进行修正,采用光学衰减片来提高低辐照度的稳定性,通过氙灯和光学积分器投影镜离焦的方式提高辐照不均匀度。结果表明研制的气象检测用太阳模拟器的光谱相匹配度达到AM1.5中A级标准,辐照强度在100~1250W∕m2连续可调,辐照不稳定度达到±1%,辐照不均匀度在Φ100mm和Φ200mm范围内分别达到±1%和±2%,满足气象辐射计量仪表检测的需要。     

海上飞行目标红外辐射特性测量试验设计

海上的飞行目标的飞行海域环境气象条件比陆地复杂,在进行目标红外辐射特性测量时,大气透过率不确定度增加.本文以海上飞行目标为例,设计了一种基于参考黑体的飞行目标红外辐射特性测量试验,以此提高海上飞行目标红外辐射亮度的测量精度.     

长焦距航空遥感器的光学装调

针对航空遥感器光机结构的精度需求,提出一种装调方法。对具有折反光路的系统,调整好各部件的位置和姿态,观测星点和光学传函,使系统接近最优的成像状态。通过照相的方法,确定遥感器的焦平面在1/4焦深以内。借助装调出的光学系统为基准,使自动检焦调焦机构的自准直结果准确,以确定像面位置,使遥感器的性能达到最好状态。     

基于大气修正的目标红外辐射测量

目标红外辐射测量是目标特性获取和目标识别的重要手段之一。在大气中测量目标辐射特性时,需要考虑目标与红外测量系统之间的大气透过率和程辐射。建立了大气中目标辐射测量模型,分析了辐射测量精度。利用长波红外相机对ISDC黑体进行了红外辐射测量实验,并利用MODTRAN软件计算大气透过率和程辐射,对测量数据进行大气修正。实验结果显示,目标辐射反演精度在9.5%～12.3%左右。     

弹头壁面温度场建模及红外辐射特性研究

空间目标红外信号难以进行实测,主要依靠建模仿真得到．通过建立飞行于弹道中段目标的壁面温度场模型,以弹头及两种诱饵为仿真对象,考虑表面材料及内热源对弹头温度的影响,采用有限体积法求解壁面空间温度场分布,得到了全弹道内表面平均温度及辐射度变化规律．进一步分析目标对环境辐射的反射,计算了目标的辐射光谱分布．仿真分析表明,弹头及诱饵间表面温度分布、辐射度变化率、光谱分布均有很大差异,为红外探测识别提供了基本参数和理论依据．     

红外光学系统团簇污染对系统杂散辐射特性的影响

红外光学系统中光学元件表面污染粒子的存在会引起系统杂散辐射特性的变化,并导致系统信噪比的下降。本文研究讨论了光学元件表面的团簇污染模型,并以典型的卡塞格伦式红外望远镜系统为例,利用ASAP光学追迹软件,仿真分析了该系统主镜在团簇污染后的杂散辐射特性以及系统目标-背景对比度的变化,并讨论了污染团簇位置的影响。经研究分析发现,光学元件镜面的团簇污染不仅会造成系统杂散辐射特性的变化,还会使系统的目标-背景对比度明显降低。并且,污染团簇在光学元件表面沉积的位置对系统杂散辐射的影响也会有所不同,且镜面边缘附近团簇污染的影响较中心位置附近更为明显。因此,在实际应用中,需要严格控制光学元件表面污染粒子的覆盖率,并及时合理地清洗镜面。     

CO2探测仪星上辐射定标设计方法的研究

为了使CO2探测仪性能变化得到校正,对CO2探测仪的星上辐射定标方法进行了研究。首先,利用稳定辐射源太阳与漫反射板相结合实现CO2探测仪探测器绝对辐射定标,其次,以定标灯、漫反射板与定标探测器相结合的方法对漫反射板反射率进行监视,实现CO2探测仪的相对辐射定标。最后,采用双定标灯、双定标探测器相互比对的方法对定标灯、定标探测器的性能变化进行校正,进而实现CO2探测仪的高精度星上辐射定标。实验结果表明:星上定标灯稳定性优于1%,星上定标探测器线性度优于0.01%。方案可以实现CO2探测仪绝对辐射定标5%,相对辐射定标3%的精度要求。     

发射率对辐射测温精度的影响及其在线测量技术

在阐明物体表面的发射率对辐射测温精度有重要影响的基础上,评述了发射率的在线测量技术。     

干涉型成像光谱仪在轨辐射定标技术应用

为提高干涉型成像光谱仪空间目标测量精度,降低传感器中各个探测元响应度差异,提升成像光谱仪在轨辐亮度测量准确性。提出了一种基于定标场反射率测量参数结合计算程序仿真与成像仪在轨测量数据比对的空间定标方法。首先在介绍高光谱定标概念的基础上,提出了不同光谱响应函数、不同场地条件下的高精度入瞳亮度计算方法;其次对干涉型成像光谱仪进行在轨相对辐射修正,校正传感器中各探测元相应度差异,利用反射率基法开展了在轨绝对辐射定标试验,针对可见光、近红外波段建立在轨辐射定标计算模型。解决了包括多种反射率场地、高精度测试区域指示的试验方案优化设计问题,实现了星载高分辨率干涉型成像光谱仪的在轨高精度定标。研究结果表明,采用该定标技术使成像光谱仪的在轨测量精度达到5%。此外,定标场地环境条件对模型计算精度有一定影响,大面积均匀场适合采用反射率基法,小面积均匀场则引入邻近像元效应进行计算,通过布设人工指示目标,可提高反射率测量数据的准确性。所采用的定标技术已获得工程应用。     

New high-accuracy spacecraft VLBI tracking using high data-rate signal: A demonstration with Chang’E-3

As the scientific data volume in deep-space exploration rapidly grows,spacecraft heavily relies on high data-rate signals that span several megahertz to transmit data back to Earth.Employing high data-rate signals for high-accuracy radiometric interferometry can simultaneously deal with data transmission and spacecraft navigation.We demonstrate very long baseline interferometry(VLBI)tracking of the Chang’E-3 lander and rover to determine their relative lunar-surface position using downlink high data-rate signals.A new method based on the VLBI phase-referencing technique is proposed to obtain the differential phase delay,which is much more accurate than the differential group delay acquired by conventional VLBI approaches.The systemic errors among different signal channels have been well calibrated using the new method.The data from the Chang’E-3mission were then processed,and meter-level accuracy positions of the rover with respect to the lander have been obtained.This demonstration shows the feasibility of high-accuracy radiometric interferometry using high data-rate signals.The method proposed in this paper can also be applied to future deep-space navigation.     

Absolute radiometric calibration of CBERS-02 IRMSS thermal band

Based on the laboratory calibration before launch of CBERS-02 IRMSS thermal infrared channel, the onboard blackbody calibration, the radiometric crosscalibration against TERRA MODIS corresponding channel and the in-flight field calibration at Lake Qinghai: water surface radiometric calibration test site of China on Aug. 17, 2004 are carried out in this research. When making onboard blackbody calibration of CBERS-02 IRMSS, it is necessary to understand inside structures and light path in IRMSS camera and receive and process calibration blackbody signals at normal and high temperatures. Onboard blackbody calibration results of each detector are very important to relative radiometric calibration of images processing and absolute radiometric calibration of each detector. In-flight field calibration mainly contains field experiments, obtaining synchronous images, spectrum marching and MODTRAN radiative transmission computation. Radiometric cross-calibration of CBERS-02 IRMSS thermal band against TERRA MODIS selected 6 times synchronous images of two sensors passing through Lake Qinghai and Lake Taihu from August to December, 2004 to compute the cross calibration data. Combining the in-flight field calibration and radiometric cross calibration data, the absolute radiometric calibration coefficients are calculated by the linear regression method. This new calibration model can obviously control the radiometric calibration uncertainties aroused by the single point method used in the in-flight calibration of CBERS-02 IRMSS, this kind of sensors cannot receive the cosmic background radiation. In this research, the radiometric calibration coefficients obtained through the linear regression model are 8.53 (gain, unit: DN/W m^?2sr^?1μm^?1) and 44.92 (offset, unit: DN).     

辐射保真的红外遥感图像超分辨率重建

为了解决红外遥感图像超分辨率重建与辐射定标精度保真之间的矛盾,结合正则化超分辨率重建理论,建立了基于二阶总广义变分的超分辨率重建模型。 通过分析重建模型的特点,引入交替方向乘子法进行数值求解;重建过程利用双边滤波器原理,将图像的高低频信息分离;针对分离后高频信息图像进行重建处理,将低频信息图像与重建后的高频信息图像融合达到超分辨率的目的。 利用风云四号气象卫星得到的真实红外图像进行实验验证和定量化分析,表明该方法对辐射定标精度的影响要小于常规意义下的超分辨率重建的影响。     

Radiometric Calibration Chain Design Based on Uniform Collimated Laser Source

A uniform collimated laser source,composed of the integrating sphere source and the off-axis parabolic,is designed.The calibration process is analyzed theoretically,and Monte Carlo ray tracing method is used to simulate and analyze the design model.The results show that when the calibration source is composed of an 8 cm diameter integral sphere,10 mm diameter exit port,and 1 000 mm focal length,and an off-axis angle 60°parabolic mirror,the maximum divergence angle is 7.5 mrad and the uniformity of irradiance is 99.31%.Finally,the uncertainty of radiometric calibration process is analyzed,and the calibration accuracy of 0.335%for imaging spectrometer can be achieved by using the radiation calibration laser source.     

Calibratio performance evaluation of the spaceborne hyperspectral CHRIS imager

The CHRIS (Compact High Resolution Imaging Spectrometer) is a new imaging spectrometer, carried on board a new space platform called PROBA (Project for On Board Autonomy). The satellite was successfully launched in October 2001 by the European Space Agency (ESA). CHRIS operates over the visible/near infrared band (400-1050 nm). It has five work modes and can reach a maximum of 62 spectral bands. In this research, atmospheric correction based on hyperspectral images was performed on CHRIS images by using the popular radiance transfer code ACORN (Atmospheric Correction Now) and empirical algorithms. ACORN was also used to evaluate the calibration performance of CHRIS by the retrieved spectra of typical vegetation and soil. As a result, the maize reflectance spectrum corrected by ACORN could characterize vegetation reflectance in the range of 498-750 nm, but gave a fairly large deviation beyond 750 nm, showing the deficiency of spectral calibration beyond 750 nm. The ACORN-derived soil reflectance decreased beyond 800 nm, which was quite inconsistent with field-spectrum measurement and showed that the calibration accuracy couldn't meet the requirements of ACORN for spectral and radiometric calibration within a certain spectral range. In addition, the stripes on the retrieved water-vapor content map indicated that the radiance-calibration performance of CHRIS is not perfect. As the first spaceborne hyperspectral imager of ESA, the calibration performance of CHRIS needs to be improved.