通道型偏振光谱仪望远镜组偏振效应分析与优化

为了满足高精度偏振探测要求,通道型偏振光谱仪在设计时需要考虑望远镜组偏振效应的影响,并对其进行相应的分析和优化。首先,分析望远镜组偏振效应的影响因素,采用坐标变换和穆勒矩阵连乘法建立了考虑膜系偏振效应的望远镜组穆勒矩阵模型,并带入通道型偏振光谱仪偏振解调模型。接着,通过同时控制S光和P光的透过率和相位延迟,设计相应的低偏振效应膜系。最后,运用偏振光线追迹的方法对镀有不同膜系的望远镜组进行偏振效应仿真。仿真结果表明,在580 nm和750 nm波长处,低偏振效应膜系与高偏振效应膜系的偏振探测精度变化不明显。而在420 nm波长处,低偏振效应膜系相较于常用膜系的边缘视场偏振探测精度提高了3.22%。低偏振效应膜系可以有效降低通道型偏振光谱仪望远镜组偏振效应,提高仪器的偏振探测精度。

增强吸收光谱技术的研究进展及展望

光程吸收光谱技术是吸收光谱技术发展中的一个重要分支,近年来基于不同光源技术、吸收腔技术、探测方式的光程吸收光谱技术大量涌现。随着对探测灵敏度和吸收光程长度需求的提高,出现了基于增强吸收原理的光程吸收光谱技术,包括:积分腔光谱(ICOS)、腔增强吸收光谱(CEAS)和腔衰荡光谱(CRDS)。增强吸收光谱技术具有高光谱分辨率、高灵敏度、快速响应、便携等优势,但至今缺乏统一的概念和明确的分类依据。本文梳理了吸收光谱技术的发展历程,明确了多光程吸收光谱技术的概念。依据吸收腔内是否发生谐振吸收,提出了基于谐振原理的吸收光谱技术这一概念,分析总结了谐振吸收光谱技术的研究现状,并对这些技术在各领域的应用进行概述。最后,对谐振吸收光谱技术中关键技术的未来发展进行了展望。

机载光谱仪高模态主支撑结构优化

为满足机载光谱仪主支撑结构动力学特性好、质量低等需求,本文进行了主支撑结构的优化设计及试验验证。首先,针对常用结构无法适用于本系统的问题,提出了一种框架式与薄壁筒式结构相结合的总体结构形式,方便对遮光罩与结构进行一体化设计,可有效降低质量且保证刚度;其次,为提高系统模态,采用多变量集成优化方法,在满足质量要求的情况下将其模态由127 Hz提高到156 Hz,使其具有良好的动力学特性;然后,为确定振动环境对系统调制传递函数(MTF)的影响,通过有限元分析与灵敏度矩阵相结合的方法分析了振动环境对系统MTF影响,并通过计算得知本结构能适用于像元尺寸大于10μm的机载系统;最后,通过对主支撑结构的测振试验与整机结构的波前检测试验,验证了本文设计方法与分析过程的有效性与可行性。本文提出的优化设计方法可为机载遥感仪器结构的优化设计提供参考,将有助于推动机载遥感仪器结构设计技术的发展。

基于蒙特卡罗法的星载太阳辐照度光谱仪对日指向误差分析

为保证光谱仪能够获取到有效太阳光谱数据,要求搭载光谱仪的二维转台能够长时间高精度跟踪太阳,而跟踪太阳的前提是转台实现精准指向,使太阳进入导行镜的有效视场。根据从卫星接收的太阳矢量和姿态数据对安装误差进行修正,计算修正后转台指向的参考值,并确保指向误差小于1°。在转台各个基准立方镜上建立坐标系,采用坐标变换法建立了对日指向的数学模型,通过运动学反解给出转台调整角度与轨道坐标系下太阳矢量的解析关系。然后,结合光谱仪的在轨运动形式,对其工作过程中的主要误差来源进行分析,并在MatLab平台上搭建基于蒙特卡罗法的指向误差模型。仿真结果表明指向误差优于0.35°。最后,在地面开展太阳指向模拟实验,测得春分轨道下指向误差低于0.16°,满足导行镜捕获视场需求。实验结果验证了数学模型的正确性及有效性,同时为光谱仪在轨工作提供了设计参考。

航空摆扫成像像移计算与误差分配

航空摆扫成像时,曝光时间内像点的移动是影响成像质量的重要因素。为了研究三面镜各项误差对像移量的影响,利用齐次坐标变换法建立了像点位移计算模型,准确地引入了摆扫镜轴系误差等常见误差项。在此基础上,分析了三面镜加工装调误差对像点位移量的影响,并比较了像点位移量对各误差项变化的灵敏度。接着,根据系统调制传递函数的指标对像点位移量的范围进行了限定,确定了高图像质量允许的像点位移量。最后,对分配后的三面镜误差进行了蒙特卡罗法仿真。仿真结果表明,像点位移量在10^-5 m量级,像移的MTF因子为0.97,满足指标要求。该结论对摆扫相机的结构设计与加工装调有重要的参考价值。

大视场空间可见光相机的杂散光分析与抑制

空间相机用于对空间暗弱目标的探测与监视,视场外杂散光的进入会降低像面对比度,严重时甚至会导致相机无法工作。大视场光学系统对杂散光尤为敏感。针对此问题,本文以一大视场空间相机为例,分析其杂散光的来源,通过研究杂光传输机理并总结抑制措施。为满足其轻小型的指标要求,在尺寸限制下分别设计挡光环垂直光轴和倾斜的遮光罩及光阑等消杂光结构。TracePro软件仿真结果显示:倾斜挡光环遮光罩的效果更好,该结构在杂光抑制角外的的点源透过率(PST)均达到10-7量级,系统至少可以满足6.5星等目标的探测,验证本文消杂光结构方案的有效性,为后续的系统优化提供了一定的参考。

激光通信地面测试终端间隔离度的仿真分析

受空间所限,激光通信地面测试平台与被测终端之间的距离远小于实际通信距离,导致测试平台光机等器件产生的后向散射杂光进入被测终端,从而严重影响被测终端的测试性能。从被测终端与测试平台间的光学干扰问题出发,本文研究了被测终端与测试平台间隔离度的关系,分别设计了卡塞格林和离轴三反光学天线,并根据杂散光传输模型,采用杂散光分析软件分析了光学天线结构形式及表面粗糙度两方面对隔离度的影响。分析结果表明,采用离轴三反光学天线时的隔离度明显高于卡塞格林光学天线,且隔离度随着光学表面粗糙度的减小而增大,当光学表面的粗糙度达到0.892 nm时,隔离度可达-86.22 dB。最后,推导了ABg模型与Harvey模型参数间的关系,并根据粗糙度与TIS计算公式,得出粗糙度分别为0.7 nm及0.5 nm的ABg模型参数,它们的终端间隔离度分别为-94.39 dB和-97.3 dB,实现了-90 dB的隔离度指标。

空间卫星相机安装固定基频性能优化设计

某空间卫星相机在多次迭代优化后基频仍然未满足技术要求,为解决相机整机基频偏低,易与卫星平台发生共振的问题,提出了更改相机安装固定位置为整机Z向质心平面处的解决方法。首先建立空间相机振动模型,通过对底部和中部两种安装结构等效模型的理论计算,找到提高相机基频的方法;其次,进行有限元仿真确定提高整机基频的理想位置,并根据仿真分析结果,优化设计了相机Z向中心平面处和Z向质心平面处两种安装方案;最后,采用有限元分析软件MSC/Patran对两种安装方案进行仿真分析对比。经分析确定,质心平面处安装方案基频较高,同时反射镜精度仍满足设计要求,整机重量相比初始设计有所下降。结果表明,提出的质心平面处安装方案提髙了整机基频,保持了反射镜精度,同时还部分降低了整机的重量,证明了结构设计和理论分析的合理性。

An Ocean Reanalysis System for the Joining Area of Asia and Indian-Pacific Ocean

An ocean reanalysis system for the joining area of Asia and Indian-Pacific Ocean (AIPO) has been developed and is currently delivering reanalysis data sets for study on the air-sea interaction over AIPO and its climate variation over China in the inter-annual time scale.This system consists of a nested ocean model forced by atmospheric reanalysis,an ensemble-based multivariate ocean data assimilation system and various ocean observations.The following report describes the main components of the data assimilation system in detail.The system adopts an ensemble optimal interpolation scheme that uses a seasonal update from a free running model to estimate the background error covariance matrix.In view of the systematic biases in some observation systems,some treatments were performed on the observations before the assimilation.A coarse resolution reanalysis dataset from the system is preliminarily evaluated to demonstrate the performance of the system for the period 1992 to 2006 by comparing this dataset with other observations or reanalysis data.

The Impact of "Bad" Argo Profiles on Ocean Data Assimilation

Recent studies have found cold biases in a fraction of Argo profiles (hereinafter referred to as bad Array for Real-time Geostrophic Oceanography (Argo) profiles) due to the pressure drifts during 2003 and 2006. These bad Argo profiles have had an important impact on in situ observation-based global ocean heat content esti- mates. This study investigated the impact of bad Argo profiles on ocean data assimilation results that were based on observations from diverse ocean observation systems, such as in situ profiles (e.g., Argo, expendable bathy- thermograph (XBT), and Tropical Atmosphere Ocean (TAO), remote-sensing sea surface temperature products and satellite altimetry between 2004 and 2006. Results from this work show that the upper ocean heat content analysis is vulnerable to bad Argo profiles and demon- strate a cooling trend in the studied period despite the multiple independent data types that were assimilated. When the bad Argo profiles were excluded from the as- similation, the decreased heat content disappeared and a warming occurred. Combination of satellite altimetry and mass variation data from gravity satellite demonstrated an increase, which agrees well with the increased heat con- tent. Additionally, when an additional Argo profile quality control procedure was utilized that simply removed the profiles that presented static unstable water columns, the results were very similar to those obtained when the bad Argo profiles were excluded from the assimilation. This indicates that an ocean data assimilation that uses multiple data sources with improved quality control could be less vulnerable to a major observation system failure, such as a bad Argo event.

Evaluation of a global eddy-permitting hybrid coordinate ocean model

本文基于垂直混合坐标模式HYCOM建立一个水平分辨率17–25km的准中尺度涡海洋环流数值系统,利用气候态强迫场进行了百年试验,保证了海洋状态达到平衡,然后利用高频强迫场对过去22年(1993–2014)开展了数值试验,利用观测对试验结构进行了检验。结果表明,对于全球大洋而言,模拟的海表温度要比观测暖0.29°C,模拟的海表温度季节循环稍微偏强;模拟的次表层温盐结构比较合理,但由于海冰模块的缺乏在上层1000m纬向平均的全球海洋引起了一个0.21°C冷偏差和0.16psu的淡水偏差;模拟的赤道太平洋潜流强度要弱于观测,但要优于再分析数据ECCO。能很好地再现与中尺度涡有关的变率位置。总之,该海洋环流数值系统能够比较合理地模拟上层海洋的动力、热力以及变率结构。

Athermal design of the mirror support with flexure hinges for the laser communication terminal

In order to suppress the effect of the temperature variation on the wavefront of the laser communication terminal, the secondary mirror support with flexure hinges is designed. The series-wound straight-circle flexure hinge is designed to achieve the maximal variation range of the flexibility or stiffness with the limit of flexure hinges' geometrical size. The position and quantity of the flexure hinges are determined to control the deformation direction of the secondary mirror. In order to search the direction in which the wavefront aberration is minimum, the flexure hinges' parameters are optimized with the system wavefront aberration as the optimization objective. The prototype of the laser communication terminal is constructed and the value of the wavefront aberration is measured under the condition of 20±2°C. Experimental results show that the value of the wavefront aberration root mean square(RMS) is reduced from 0.066λ to 0.042λ, meeting the requirement of RMS less than 1/20λ(λ=632.8 nm). The athermal design method presented in this paper provides a novel way for the athermal design of the small aperture mirror support in off-axis optical systems.