小型CMOS太阳敏感器

提出并设计了一种基于FPGA的小型CMOS数字式太阳敏感器.对其光学系统设计参数进行了合理选择,采用了"质心法"求取太阳像光斑中心位置,并用最小二乘法对该太阳敏感器进行了标定.经过测试,应用该技术实现的太阳敏感器样机的视场范围可达到60°×60°,测角精度可达到0.05°,帧频10Hz,质量小于250g,总功耗为750mW.包括处理电路在内的整个结构尺寸为80mm×80mm×35mm.     

基于光纤导入技术的太阳敏感器设计与研究

设计了一种基于光纤导入的太阳敏感器,其包括三个部分:光学头部、光电传感器和太阳偏移角度的算法.光学头部采用两对对称光纤和一根中心光纤,通过计算每对光纤导入光能的差分值,获得太阳与航天器自身坐标系统的相对角度关系.该光学结构兼顾了大、小视场,提高了太阳敏感器定位精度.采用光纤作为太阳光的导入器,将光能导入置于航天器内部的...     

基于MEMS光线引入器的太阳敏感器技术

太阳敏感器是卫星等航天器上的重要姿态测量部件,其原理是测量太阳光线和敏感器本体主轴的夹角,近而确定卫星的指向.随着MEMS技术和高精度图像传感器技术的发展,将MEMS光线引入器阵列和APS(Active Pixel Sensor)图像传感器技术进行组合,在不增加系统的质量和功耗的情况下通过多个成像阵列来降低系统的随机误差,提高成像中心位置的准确性,从而将太阳敏感器的测量精度提高一个量级.同时采用图像预测提取相关算法(Future Extraction and Image Corre-lation-FEIC),提高了系统的鲁棒性,在部分小孔受到堵塞等干扰情况下,依然保证系统正常工作,精度上基本上不受影响.传统的太阳敏感器一般采用单孔式光线引入器和CCD等方案来实现的,精度比较低.这种新设计思路和实现方法为太阳敏感器系统的可靠性提供了重要保障.     

三轴紫外光学成像敏感器

设计了一种三轴紫外敏感器,解决了近地轨道大视场观测问题。通过非常规光学系统,即反射阵列组合式光学系统,将一圆型大视场分成八个子视场成像、叠加后经图像处理,为卫星提供三轴姿态信息和自主导航数据。三轴紫外敏感器标定精度为偏航小于0.05°,俯仰小于0.05°,滚动小于0.05°。研制成的工程样机,通过观星试验和利用星模拟器测试,三轴紫外敏感器可以观测到5等星;紫外波段敏感器可以作为是深空探测航天器重要敏感器之一。     

基于CMOS APS的星敏感器光学系统结构设计与优化

基于CMOS APS的星敏感器是适应航天技术微型化的发展而产生的新一代姿态敏感器.结合星敏感器系统帧频以及探测信噪比阈值的要求,确定了合适的CMOS探测器件以及光学系统的通光孔径、焦距、工作光谱范围和中心波长等主要参数.分别基于球面和非球面,在ZEMAX平台上实现了具有良好像质的大孔径(F/1.198)、大视场(22.6°)、宽光谱范围(0.5～0.8 μm)的两种光学系统的结构设计,满足了对弥散斑、能量集中度、畸变等的特殊要求.     

卫星太阳敏感器模拟器校准技术研究

针对卫星姿轨控半实物仿真系统的技术要求,提出了一种用于太阳敏感器模拟器的校准装置。校准装置以FPGA和AVR单片机为控制核心,微型单板电脑模拟动力学计算机,通过网口进行指令的上传下达。内置信号调理电路、高精度采集模块,数据解算模块等。该校准装置集成度高,替代了原有由数字表、动力学计算机等组成的复杂校准系统,有效地降低了成本,提升效率约40%,实现了太阳敏感器模拟器的快速全过程在线校准。     

基于SOPC的太阳敏感器信息处理系统

基于内嵌处理器软核MicroBlaze的FPGA,设计了一种太阳敏感器信息处理系统。采用MicroBlaze软核实现光斑质心提取和姿态换算,并通过其它逻辑资源实现图像传感器驱动、图像存储和接口通信等模块的时序控制,同时根据MicroBlaze软核的特点,提出了一种基于扫描方式的质心提取算法。结果表明,具有单精度浮点运算能力的MicroBlaze软核能够保证太阳敏感器质心提取和姿态计算的精度;基于扫描方式的质心提取算法流程简单,占用资源少;采用SOPC的太阳敏感器无需DSP或ARM等协处理器,减小了硬件设计复杂性,提高了系统的集成度和性能。     

静态紫外地球模拟器光学系统设计

静态紫外地球模拟器是一种对紫外导航敏感器进行地面标定和精度测试的设备。本文设计了一种静态紫外地球模拟器光学系统,提出大视场静态紫外地球模拟器光学系统设计方案,对光学系统的参数进行了分析,系统选用七片透镜进行设计,有效孔径为D=10 mm,焦距为f=100 mm,视场角为Φ40°。全视场相对畸变小于0.036%,MTF在50 lp/mm处大于0.7,波像差均方根值小于0.037λ,地球张角偏差??0.006 7°,达到了高精度的指标要求,满足设计要求。     

小型太阳模拟器设计研究

太阳模拟器是一种模拟太阳辐射特性的测量仪器,其在航空航天领域中用来检测卫星热设计的热平衡试验和用来检测卫星姿态测量,并完成地面标定与测试试验。本文在突出太阳模拟器小型化的特点下,详细论述了太阳模拟器的设计要点,给出了详细设计方案。本文设计的太阳模拟器设计方法简单可靠,具有很大的推广价值。     

色温对星敏感器恒星定位精度的影响

色温影响星敏感器恒星定位精度,运用光线追迹方法,研究色温对恒星定位精度的影响.在分析不同色温恒星光谱分布特征的基础上,建立恒星光谱模型,计算色温差异引起的恒星定位误差,计算结果表明:中心视场附近色温差异引起的恒星定位误差较视场边缘小;通过合理选择光学系统的响应波段,可以减小色温差异引起的恒星定位误差,但会损失恒星到达探测器感光面的光能量.例如,当响应波长从300～1 100nm减小为400～800nm时,星敏感器视场(0°,0°)、(0°,2°)和(0°,4°)处的单颗恒星定位误差分别减小为0.042 2"、1.965 2"和3.389 1",约为原来的54%、65%和70%;色温为9 600 K、7 600 K、5 600 K和3 600 K的恒星像斑能量分别约为原来的58%、62%、63%和51%.     

基于FPGA的高可靠数字太阳敏算法研究

数字太阳敏是卫星姿态控制系统的敏感部件,对提高小卫星数字太阳敏系统的可靠性及精度具有重要意义.提出了基于FPGA的高可靠数字太阳敏算法,首先介绍了数字太阳敏系统原理,分析得出FLASH型FPGA的高可靠性能;然后利用Verilog HDL语言编写图像高斯滤波算法、太阳光斑质心提取算法,并设计了数字太阳敏系统的标定方法....     

Precision pointing of imaging spacecraft using gyro-based attitude reference with horizon sensor updates

Remote sensing satellites are required to meet stringent pointing and drift rate requirements for imaging operations. For achieving these pointing and stability requirements, continuous and accurate three-axis attitude information is required. Inertial sensors like gyros provide continuous attitude information with better short-term stability and less random errors. However, gyro measurements are affected by drifts. Hence over time, attitudes based on the gyro reference slowly diverge from the true attitudes. On the other hand, line-of-sight (LOS) sensors like horizon sensors provide attitude information with long-term stability. Their measurements however are affected by the presence of random instrumental errors and other systematic errors. The limitations of inertial and line-of-sight sensors are mutually exclusive. Hence, by optimal fusion of attitude information from both these sensors, it is possible to retain the advantages and overcome the limitations of both, thereby providing the precise attitude information required for control. This paper describes an improved earth-pointing scheme by fusion of the three-axis attitude information from gyros and horizon sensor roll and pitch measurements along with yaw updates from the digital sun sensor. A Kalman Filter is used to estimate the three-axis attitude by online estimation and corrections of various errors from the sensor measurements. Variations in orbit rate components are also accounted for using spacecraft position and velocity measurements from the satellite positioning system. Thus precise earth-pointing is achieved     

Wide-field-of-view polarization interference imaging spectrometer

A wide-field-of-view polarization interference imaging spectrometer (WPIIS) based on a modified Savart polariscope, without moving parts, and with a narrow slit has been designed. The primary feature of this device is for use with a large angle of incidence, and the target image as well as the interferogram can be obtained at the same time in the spatial domain and are recorded by a two-dimensional CCD camera. Under compensation, the field of view of the WPIIS will extend 3-5 times as large as a common interference imaging spectrometer, and throughput will raise 1-2 orders of magnitude. The developed optics is 20 x 8 cm ? in size. The spectral resolution of the prototype system is 86.8 cm(-1) between 22222.2 and 11111.1 cm(-1). This system has the advantages of being static and ultracompact with wide field of view and a very high throughput. The optics system and especially the wide-field-of-view compensation principle are described, and the experimental result of the interference imaging spectrum is shown.     

Attitude and orbit control for satellite broadcasting missions

This paper gives a broad introduction to the problems of attitude and orbit control of geostationary communications satellites. It specifically discusses the relationships between the satellite user’s requirements for a broadcasting mission and the design of the attitude and orbit control system. To put the subject in perspective, a brief review of past and present satellites is presented first. Then orbit control is described in terms of the forces that act on a satellite in geostationary orbit and the necessary station-keeping strategies. The design of attitude control systems for three-axis stabilised satellites is presented by considering the disturbance torques, attitude sensors and actuators and by identifying the various system problems and their solutions. Sources of error in pointing the satellite towards the earth are discussed together with the formulation of error budgets. Finally, the design approach for missions that require extremely accurate pointing is considered, and some remarks are given regarding the achievable accuracy for this class of satellite missions.     

Widening the effective field of view of adaptive-optics telescopes by deconvolution from wave-front sensing: average and signal-to-noise ratio performance

A fundamental problem of adaptive-optics systems is the very narrow corrected field of view that can be obtained because turbulence is extended in altitude throughout the atmosphere. The correctable field of view is of the order of 5-10 μrad at visible wavelengths and increases as the wavelength increases. Previous concepts to broaden the corrected field of view have been hardware oriented, requiring multiple wave-front sensor (WFS) measurements to control multiple deformable mirrors. We analyze the average and the signal-to-noise-ratio performance of an image measurement and postprocessing technique that uses simultaneous measurements of a short-exposure compensated image measured in an off-axis direction; an additional WFS measurement is taken in the off-axis direction. Results are presented for infinite-altitude WFS beacons driving both the WFS for the adaptive optics and the WFS looking in the off-axis direction, a variety of seeing and WFS light-level conditions, and off-axis angles from two to six times the isoplanatic angle. This technique improves the average effective transfer function out to a field angle of at least six times the isoplanatic angle while providing a higher signal-to-noise ratio in the spatial frequency domain.     

Propagation model and error analysis of an E-field sensor based on pockels effect and waveguide

Electric field measurement sensors based on the crystal Pockels effect are widely used. Currently, the development aims for electric field sensors are mainly focused on miniaturizing and integrating the sensor structure and improving measurement sensitivity and precision. The goal of this study was to analyse the sources of error in Pockels effect electric field measurement sensors, consider the mutual influence and accumulation effect of the various error factors, and establish a basic mathematical model of the measurement system with error components. Calculation and analysis were used to classify the function and change trend of several main errors, providing reference data for the structure design and error compensation of the sensor. The results show that the polarizing angle and the analyser angle have the same influence on assembly error. The inherent error is positively related to the electric field intensity. The periodic accumulation characteristic error under large electric field is also discussed. In order to avoid this error under an intense electric field, a suitable test electric field range was determined.