Design and implementation of an image stabilization device at the THEMIS solar telescope

An image stabilizer has been inserted into the optical path of the THEMIS solar telescope. THEMIS is a Ritchey–Chretien reflector telescope using an altazimuthal mount and closely tied to its spectrograph. The optical and mechanical design, implementation and system tests are described, and emphasis is put on the complexity of situations that this stabilizer must accept, including the scanning of the solar surface while stabilizing. The current closed-loop crossover frequency of the device is 65 Hz at ??3 dB on all typical solar scenes.     

Orbital period analysis of eclipsing post-novae T Aurigae: Evidence of magnetic braking and an unseen companion

Four new CCD times of light minimum of T Aurigae are presented. The orbital period variation is analyzed by means of the standard O–C technique. The new times of light minimum indicate that a ～24 yr sine-like period variation superimposed on a secular orbital period decrease is obviously seen in the O–C diagram. However, the orbital period should increase because of mass transfer between components. In order to solve this apparent paradox, three possibilities including magnetic braking mechanism, which plays an important role in angular moment loss of binary, are proposed. The mass loss rate $\dot{M}={10}^{-10.4}{M}_{\odot }{\text{yr}}^{-1}$ is derived by assuming that the Alfvén radius of secondary is the same as that of the sun (i.e. $R_A?15R_{\odot }$). Using the observational relationship of ${\dot{M}}_{\mathit{mb}}-P_{\mathit{orb}}(h)$ (McDermott and Taam, 1989, Rappaport et al., 1983), the Alfvén radius of secondary is estimated as $R_A?1.9R_{\odot }$, which only requires a weak magnetic field in secondary. Since the brightness variations of T Aurigae caused by Applegate’s mechanism need large energy beyond the total radiant energy in the time interval of 24 yr, the third body light travel-time effect is the most likely explanation for the 24-yr variation. The third body may be a brown-dwarf star in case of the high orbital inclination.     

Dynamics of flexible space vehicles with active attitude control

The implications of flexible appendages on the attitude dynamics of a space vehicle are examined in general terms. Two families of natural vibration modes, referred to as ‘constrained’ and ‘unconstrained’, are discussed and the relationships between them derived. The incorporation of either set of modes into a simulation of the general attitude motion (under the influence of perturbing torques and control torques) is explained. The influence of rotors on these results is also explored.     

A device for recording positions of a beam of an extralight torsion balance

A device for recording positions of a beam of an extralight torsion balance is developed, mounted, and tested by the practice of astronomical observations. The device makes it possible to completely automate the process of observations under constant monitoring of the measurement results in real time. The principle of color division of stationary marks which specify the meridian direction from a mobile marker is implemented owing to application of different luminescent paints and a source of UV radiation. In contrast to other recording systems of such type, the device described makes it possible to minimize convective air flows inside the chamber of a torsion balance and to drastically improve the accuracy of determining the beam direction at which the error of individual determination is ±0.172°. Long-term observations performed with the given device made it possible to reveal a distinct daily cycle in the behavior of a torsion balance, the nature of this cycle still being unclear.     

On the variable timing behavior of PSR B0540-69: an almost excellent example to study the pulsar braking mechanism

PSR B0540-69 has a braking index measurement in its persistent state: n = 2.129 ± 0.012.Recently, it has been reported to have changes in its spin-down state: a sudden 36% increase in the spindown rate. Combining the persistent state braking index measurement with different spin-down states, PSR B0540-69 is more powerful than intermittent pulsars in constraining pulsar spin-down models. The pulsar wind model is applied to explain the variable timing behavior of PSR B0540-69. The braking index of PSR B0540-69 in its persistent state results from the combined effect of magnetic dipole radiation and particle wind. The particle density reflects the magnetospheric activity in real-time and may be responsible for the changing spin-down behavior. Corresponding to the 36% increase in the spin-down rate of PSR B0540-69,the relative increase in the particle density is 88% in the vacuum gap model. The braking index calculated with the model in the new state is n = 1.79. Future observations that measure the braking index of PSR B0540-69 in the new spin-down state will be very powerful in distinguishing between different pulsar spin-down models and different particle acceleration models in the wind braking scenario. The variable timing behavior of PSR J1846-0258 is also understandable in the pulsar wind model.     

机器视觉高斯拟合法自动导星定心系统设计

丽江2.4m光学望远镜自动导星系统升级改造需要计算CCD图像中实际星像中心的位置,在现有导星定心算法的基础上,利用机器视觉Canny边缘检测和椭圆拟合的方法识别星像轮廓,然后对星像直接二维高斯拟合,计算星像中心位置.研究了导星算法中涉及的天光背景参数、星像轮廓识别所需阈值、星像拟合边界参数的整定方法,总结出有效的自动导星定心方法,并开发了基于Linux平台的高速自动导星定心系统软件.软件对星像的高斯拟合结果与IRAF软件高斯拟合结果一致;同一天区相邻时间图像中星像中心偏移量计算结果也表明算法的有效性.     

The interactions of the solar wind with planetary magnetic fields: Basic principles and observations

A planetary magnetic field obstructs the supersonic expansion of the solar coronol ions and electrons and creates a cigar shaped bubble in the solar wind. The pressure of the solar wind on the bubble compresses and seriously distorts the planetary magnetic field. A review is given here of the theoretical calculation and experimental observation of the shape of the bubble and the configuration of the compressed magnetic field inside the surface. Other effects, namely the shock structure on the surface, the radiation belts, and the current in the antisolar side of the bubble are described as well as a simplified account of electric fields and the connection of the planetary field lines with interplanetary field lines.     

一种天文图像的光纤传输系统的设计

简要介绍该图像数据光纤传输系统的总体设计思想。详细介绍该系统中FPGA周边电路、编码/解码电路、光发送/接收电路的设计以及发送/接收两端FPGA内部逻辑电路的设计,包括某些重要器件的介绍、VHDL程序的设计思想和实现方法,并给出一些关键模块的仿真和实测波形。最后进行模拟图像数据发送与接收实验,并进行了误码率估算。     

Design and experimental test of an optical vortex coronagraph

Using an optical vortex coronagraph(OVC) is one of the most promising techniques for directly imaging exoplanets because of its small inner working angle and high throughput.This paper presents the design and laboratory demonstration performance of an OVC based on liquid crystal polymers(LCPs) at 633 nm and 1520 nm.The OVC can deliver good performance in laboratory tests and achieve a contrast of 10~(-6) at an angular distance of 3λ/D,which can be implemented for imaging young giant exoplanets in combination with extreme adaptive optics.     

一种天文用CCD相机的电路设计

简述了一种面向天文应用的CCD相机系统的设计要求,详细介绍了该相机系统电路的基本结构及设计原则,包括CCD及其周边电路、模拟前端、时钟驱动电路、电源电路以及用VHDL编写的植入FPGA的CCD时序发生器电路等一些技术细节.对系统中一些关键电路模块进行了仿真和实测,并对仿真和测试结果进行比较分析,最后给出该CCD相机的图像采集结果.     

一种IIR滤波器的FPGA设计与仿真

在分析IIR滤波器结构的基础上,借助Mat lab完成一种基于FPGA的级联型IIR滤波器的设计与实现,同时设计并生成向量文件(.vec文件),在QuartusⅡ中完成向量文件的仿真。仿真结果表明文中设计的IIR滤波器能够高效完成滤波功能,同时通过向量文件的激励引入能够增强FPGA的仿真能力。     

行间转移CCD数字系统的VHDL设计

首先分析了KAI-04022行间转移面阵CCD以及模拟前端信号处理器AD9845B的工作原理及控制要求;重点介绍了在QUARTUS 8.0的开发环境下,使用VHDL语言与FPGA器件对此图像采集系统的数字控制部分进行的分析与设计过程,并给出了系统仿真波形图。最后对硬件电路进行了测试,给出了主要输出端口的实测波形,并对仿真与实测波形进行了比较与分析。     

基于以太网的CSRH天线阵控制系统研究方案

中国频谱日像仪(Chinese Spectral Radioheliograph,CSRH)一期工程包括40面天线(400 MHz ～2 GHz)组成的天线阵,二期工程包括60面天线(2～15 GHz).天线统一控制包括天线指向调整、目标源跟踪、射电定标等.无论何种情况,所有的天线均需统一协调工作.对CSRH天线阵列整体控制进行了研究,提出了一种基于以太网的CSRH天线阵控制方案,并对可能遇到的关键问题进行分析.     

Venera-D: A Design of an Automatic Space Station for Venus Exploration

Solar System Research - The paper focuses on a future mission to Venus, Venera-D, which is presently at the stage of defining the scientific objectives and shaping the preliminary mission...     

基于FPGA的高速FIR数字滤波器设计的改进方法

在高速有限冲击响应(Finite Impulse Response,FIR)数字滤波器的设计中,随着滤波器阶数的增加,保持数据流速率和有效使用硬件资源成为设计的一个重点和难点。基于高速并行有限冲击响应数字滤波器的基本原理,提出了一种将位平面法、正则有符号系数(Canonical-Signed Digit,CSD)编码算法和抽取算法应用于并行有限冲击响应数字滤波器的改进方法。设计通过Matlab仿真,在Quartus II中编译、仿真、综合后下载到现场可编程门阵列(Field Programmable Gate Array,FPGA)中进行测试,结果显示,这种改进方法较好地解决了滤波器阶数和数据流速率与硬件资源之间的关系。     

天籁实验抛物柱面天线阵结构设计与力学分析

为了满足大面积天区的射电巡天观测,完成对大尺度结构的精确测量和对暗能量的探测,需要设计可安装大量馈源单元的大规模射电干涉阵列天线。抛物柱面的结构形式能较好满足工作需求,对抛物柱面天线阵进行了结构的选型设计。基于有限元方法及有限元分析软件,建立了用于暗能量射电探测的抛物柱面天线阵结构的有限元模型,计算分析了在重力、冰雪和风力等载荷作用时反射面的变形情况。仿真计算分析结果表明:设计的用于暗能量射电探测的天线结构在各种工况下反射面变形量较小,能满足各项设计技术指标要求,从而验证了天线阵结构的合理性、稳定性和可靠性。     

基于RTS2和EPICS的成像控制软件的设计

EPICS是一个用于开发分布式设备控制程序的软件开发框架,它主要用于控制大型物理实验设备及天文望远镜系统,而RTS2是Linux系统上的一个远程自主望远镜控制系统。实现了EPICS与RTS2的集成,用RTS2负责望远镜观测流程控制,EPICS用于成像设备控制,使用EPICS的成像控制软件Area Detector完成了Andor相机的控制,并完成了RTS2和EPICS融合的命令状态接口,从而让RTS2能够兼容EPICS组件。成功用RTS2和EPICS实现了Andor相机的控制,并很好地集成到RTS2的流程控制中。     

基于IBOB的射电望远镜宽带数字频谱仪系统的设计与测试

简述了基于IBOB和Xilinx System Generator平台的射电望远镜宽带数字频谱仪系统的设计与应用;给出了双路400MHz、2048通道、16IP输出数字频谱仪系统的具体设计方案,并对该数字频谱仪器的性能指标进行了分析和测试,验证了方案的可行性;最后初步讨论了滤波器设备对后端系统的影响。