阵列量子器件的信噪比与处理

本文讨论了影响照相底片、光电倍增管、直到ＣＣＤ等探测器信噪比的因素，并导出了阵列量子器件的总信噪比与其单个象素的信噪比之间的关系表达式。     

可用于近红外太阳观测的几种红外探测器阵列

总结了天文用近红外焦平面阵列（ＩＲＦＰＡ）的发展历程，阐述了ＩＲＦＰＡ的结构，重点介绍了ＩｎＳｂ，ＨｇＣｄＴｅ和ＰｔＳｉ三种近红外探测器阵列，结合目前在筹建的红外太阳塔计划，对其各项性能指标作了详细比较。]     

GDJ人卫目视观测数据采集和处理系统的研制

本文介绍了ＧＤＪ跟踪打印经纬仪在人造卫星的观测中如何应用计算机对多圈卫星的目视观测资料进行实时采集、处理等工作过程的原理和方法。     

GPS信号信噪比对接收机捕获性能的影响

对于在强卫星信号的干扰下GPS接收机对弱卫星信号的捕获的性能进行了分析。对于强信号对弱信号的干扰进行了推导,讨论了几种能够改善接收机捕获性能的方法,并进行了相应的仿真,仿真的结果表明这几种方法是可行的。     

斑点干涉术统计结果的信噪比模拟和分析

高分辨统计重建中,随机误差影响着统计结果的信噪比,从而限制了探测目标时所能达到的精度。通过推导给出了单星斑点干涉术统计结果信噪比的数学表达式,并模拟计算了不同视宁度参量r0和不同光子数下斑点图统计功率谱环带上的信噪比,模拟计算结果和理论数学模型吻合较好,最后对一些实测数据进行了处理和分析。     

云南天文台所测大地星的初始星表

本文给出在1987年至1990年大地星表观测期间,云南天文台所观测到的604颗(其中FK5及FK5补编共203)二次过等高圈的恒星位置改正。     

四阵元微带天线阵列试制与测试

将阵列天线放置于射电望远镜焦平面处,结合波束合成网络,可以同时观测一片天区,实现更大的视场覆盖。由于需要对各个阵元的幅度和相位进行调控,阵列天线实际就是一个小型相控阵,因此在做阵列设计时,除了需要结合反射面焦面场分布及望远镜拟实现的视场以外,阵列自身的性能验证可以参照传统相控阵进行。设计并加工了工作在1.27 GHz的2×2矩形排布的微带贴片天线阵列,阵元间距为0.7倍波长。经实测,各端口S11均在-10 dB以下,4阵元合成后波束增益为12.54 dBi,通过为对应阵元添加理论偏移30^°的延时线,实测阵列的波束扫描角度为28.3^°。上述实测数据与仿真结果相比虽略有差异,这和阵列加工及馈电端口焊接有关,但相关工作为之后更多阵元的阵列天线设计、研制及测试积累了经验,尤其对性能验证具有较高的指导意义。     

组成干涉阵列的阵元数目问题研究

使用模拟干涉成像实验对组成干涉阵列的阵元数目进行讨论,假设分别使用从20个到100个天线组成干涉阵列,使用基因遗传优化的方法得出随天线数目的增加在旁瓣水平、能量覆盖率和平均方差等3种评价标准下的性能变化曲线,通过拟合得出天线数目与各种评价效果的函数对应关系,又进一步讨论了使用效果截断、增加阵元效率等方法为设计干涉阵列的阵元数目提出合理方案,为太阳低频射电阵列阵元数目的确定提供参考。     

具有旋量场的量子宇宙学

本文利用Hartle和Hawking的方法,讨论了具有旋量场的量子宇宙学,得到了相应的Wheeler-De Witt方程。求出了具有旋量场的宇宙波函数。从波函数可以看出,当标度因子α很小时,旋量场的影响很强,具体的形式与初始条件有关,而当标度因子α很大时,旋量场的行为和标量场一样。     

13 m天线观测深空探测器数据的处理与分析

武汉大学近年来逐步完善了13 m天线中用于深空探测的硬件设施,且收集了大量观测数据,包括月球探测器嫦娥三号(Chang’E-3, CE3)、火星探测器火星快车(Mars Express, MEX)和火星轨道勘察器(Mars Reconnaissance Orbiter, MRO)、土星探测器Juno等。对近两年的观测数据做了整体分析,包括信号接收功率、接收频率精度、氢钟稳定性、总相位抖动等方面。分析结果显示,接收信号的信噪比在制冷接收机安装之后提高了1倍,接收频率的精度在氢钟安装之后也提高了1倍,达到20 m Hz。13 m天线的氢钟在ms量级稳定性较差,但1 s稳定度达到10-12量级,能够满足当前深空探测的需求。另外,还提出一种事后计算总相位的方法,能够适应于极低信噪比情况。总相位受等离子体影响的分析结果与国际上研究结果接近。整体分析结果表明,13 m天线的观测数据除了可提取高精度多普勒频率应用于测定轨之外,还可提取相位抖动做空间介质等科学研究。     

Array Signal Processing for Radio Astronomy

Radio astronomy forms an interesting application area for array signal processing techniques. Current synthesis imaging telescopes consist of a small number of identical dishes, which track a fixed patch in the sky and produce estimates of the time-varying spatial covariance matrix. The observations sometimes are distorted by interference, e.g., from radio, TV, radar or satellite transmissions. We describe some of the tools that array signal processing offers to filter out the interference, based on eigenvalue decompositions and factor analysis, which is a more general technique applicable to partially calibrated arrays. We consider detection of interference, spatial filtering techniques using projections, and discuss how a reference antenna pointed at the interferer can improve the performance. We also consider image formation and its relation to beamforming.     

GPS接收机的中频信号处理算法研究

该文对GPS接收机的中频信号处理算法进行了研究,内容主要涉及信号捕获、载波恢复和伪码跟踪3部分,详细分析了信号捕获过程中所采用的匹配滤波器法、快速傅里叶算法(FFT)、锁频环(FLL)、锁相环(PLL)以及延迟锁定环(DLL)的算法原理,并对环路滤波器作了相应的阐述,给出环路对应的递推公式．     

The Impact of Bias Row Noise to Photometric Accuracy:Case Study Based on a Scientific CMOS Detector

We tested a new model of CMOS detector manufactured by the Gpixel Inc,for potential space astronomical application.In laboratory,we obtain some bias images under the typical application environment.In these bias images,clear random row noise pattern is observed.The row noise also contains some characteristic spatial frequencies.We quantitatively estimated the impact of this feature to photometric measurements,by making simulated images.We compared different bias noise types under strict paramete...     

Reticon探测器用于位置监测的信号处理方法和精度分析

利用低纬子午环上配备的Reticon探测器的输出信号 ,采用重心方法和互相关分析方法分析测定了Reticon用于位置监测的精度。结果表明 :在仪器系统保持稳定的情况下 ,Reticon监测位置变化的精度优于± 0 .0 1像素 (单次测定的标准误差 )。     

遥测接收机基带信号处理的数字化实现方法

根据VLBI系统中接收的遥测信号基带信号的特点,介绍了利用虚拟无线电技术实现遥测接收机基带信号处理的基本原理,并分别概述了接收机的载波解调、副载波解调、数据转换环3个功能模块的数字化实现方法。仿真结果和实测数据表明,利用虚拟无线电技术能够很好地实现对遥测信号的解调和同步工作,又因该技术本身具有容易更新、方便添加接口、可并行化等优点,这种基于虚拟无线电技术的遥测接收机基带处理系统,将能够为遥测、导航、天线组阵等相关技术提供很好的实验和应用平台。     

Calibration of the DAMPE Plastic Scintillator Detector and its on-orbit performance

The DArk Matter Particle Explorer(DAMPE) is a space-borne apparatus for detecting the highenergy cosmic-ray-like electrons, γ-rays, protons and heavy ions. The Plastic Scintillator Detector(PSD)is the top-most sub-detector of the DAMPE. The PSD is designed to measure the charge of incident highenergy particles and it also serves as a veto detector for discriminating γ-rays from charged particles. In this paper, a PSD on-orbit calibration procedure is described, which includes the five steps of pedestal, dynode correlation, response to minimum-ionizing particles, light attenuation function and energy reconstruction.A method for reconstructing the charge of incident high energy cosmic-ray particles is introduced. The detection efficiency of each PSD strip is verified to be above 99.5%; the total efficiency of the PSD for charged particles is above 99.99%.     

Probing Magnetic Fields with Square Kilometre Array and its Precursors

Origin of magnetic fields, its structure and effects on dynamical processes in stars to galaxies are not well understood. Lack of a direct probe has remained a problem for its study. The first phase of Square Kilometre Array (SKA-I), will have almost an order of magnitude higher sensitivity than the best existing radio telescope at GHz frequencies. In this contribution, we discuss specific science cases that are of interest to the Indian community concerned with astrophysical turbulence and magnetic fields. The SKA-I will allow observations of a large number of background sources with detectable polarization and measure their Faraday depths (FDs) through the Milky Way, other galaxies and their circum-galactic mediums. This will probe line-of-sight magnetic fields in these objects well and provide field configurations. Detailed comparison of observational data (e.g., pitch angles in spirals) with models which consider various processes giving rise to field amplification and maintenance (e.g., various types of dynamo models) will then be possible. Such observations will also provide the coherence scale of the fields and its random component through RM structure function. Measuring the random component is important to characterize turbulence in the medium. Observations of FDs with redshift will provide important information on magnetic field evolution as a function of redshift. The background sources could also be used to probe magnetic fields and its coherent scale in galaxy clusters and in bridges formed between interacting galaxies. Other than FDs, sensitive observations of synchrotron emission from galaxies will provide complimentary information on their magnetic field strengths in the sky plane. The core shift measurements of AGNs can provide more precise measurements of magnetic field in the sub parsec region near the black hole and its evolution. The low band of SKA-I will also be useful to study circularly polarized emission from Sun and comparing various models of field configurations with observations.     

Very Large Array and SOHO Observations of Type I Noise Storms,Large-Scale Loops and Magnetic Restructuring in the Corona

Very Large Array (VLA) observations at 91-cm wavelength are combined with data from the SOHO EIT, MDI and LASCO and used to study the evolving coronal magnetic environment in which Type I noise storms and large-scale coronal loops occur. On one day, we have shown the early evolution of a coronal mass ejection (CME) in projection in the disk by tracing its decimetric continuum emission. The passage of the CME and an associated EUV ejection event coincided with an increase in the 91-cm brightness temperature of an extended coronal loop located a significant distance away and with the displacement of the 91-cm source during the early stage of the CME. We suggest that the energy deposited into the corona by the CME may have caused a local increase in the thermal or nonthermal electron density or in the electron temperature in the middle corona resulting in a transient increase in the brightness of the 91-cm loop. On a second observing day, we have consolidated the known association between magnetic changes in the photosphere and low corona with noise storm enhancements in an overlying radio source well in advance of a flare event in the same region. We find anti-correlated changes in the brightness of a bipolar 91-cm Type I noise storm that appear to be associated with the cancellation and emergence of magnetic flux in the underlying photosphere. In this case, the evolving fields may have led to magnetic instabilities and reconnection in the corona and the acceleration of nonthermal particles that initiated and sustained the Type I noise storm.     

精密时钟噪声的按噪声分量分解与白噪声中f^—1随机过程的最优估计

对于任何精密时钟来说,其五种噪声分量的幂律谱系数不存在固定的比例关系,因而在对精密时钟进行最优综合时需要对其噪声进行按噪声分量分解。通过探讨白噪声中ｆ＾－１随机过程的最优估计,提出了一种分层次地对精密时钟噪声进行按噪声分量分解的方法。     

Explosive and Radio-Selected Transients: Transient Astronomy with Square Kilometre Array and its Precursors

With the high sensitivity and wide-field coverage of the Square Kilometre Array (SKA), large samples of explosive transients are expected to be discovered. Radio wavelengths, especially in commensal survey mode, are particularly well-suited for uncovering the complex transient phenomena. This is because observations at radio wavelengths may suffer less obscuration than in other bands (e.g. optical/IR or X-rays) due to dust absorption. At the same time, multiwaveband information often provides critical source classification rapidly than possible with only radio band data. Therefore, multiwaveband observational efforts with wide fields of view will be the key to progress of transients astronomy from the middle 2020s offering unprecedented deep images and high spatial and spectral resolutions. Radio observations of Gamma Ray Bursts (GRBs) with SKA will uncover not only much fainter bursts and verifying claims of sensitivity-limited population versus intrinsically dim GRBs, they will also unravel the enigmatic population of orphan afterglows. The supernova rate problem caused by dust extinction in optical bands is expected to be lifted in the SKA era. In addition, the debate of single degenerate scenario versus double degenerate scenario will be put to rest for the progenitors of thermonuclear supernovae, since highly sensitive measurements will lead to very accurate mass loss estimation in these supernovae. One also expects to detect gravitationally lensed supernovae in far away Universe in the SKA bands. Radio counterparts of the gravitational waves are likely to become a reality once SKA comes online. In addition, SKA is likely to discover various new kinds of transients.