低轨通信卫星多普勒定位性能分析

为了研究低轨通信卫星多普勒定位性能,首先分析了低轨卫星的对地覆盖特性、信号传输特性以及多普勒频移特性,推导了多普勒定位原理和方法,提出了适用于多普勒定位的精度因子.基于已在轨的铱星和全球星系统,解算了全球范围可见卫星数和定位精度因子,并对相应测站进行了定位仿真实验和误差分析.结果表明:对于铱星和全球星系统,随着纬度降低,卫星可见数减小,多普勒几何精度因子变大;多普勒定位结果精度同时受到频率测量精度、卫星位置误差以及卫星速度误差影响,当卫星位置误差小于10 m、卫星速度误差小于0.1 km·s^-1时,对定位结果影响不大,此时频率测量精度成为影响定位精度的决定性因素,且当频率测量精度为0.01 Hz时,定位精度可达1.18 m.     

卯酉圈观测测定子午环的绝对参数(Ⅰ)——绝对测定方位角

子午环上用于测定方位角的拱极星方位标方法,在纬度较低的地区不适用。本文提出了用卯酉圈上的观测测定方位角的方法,即用一架既能在子午方向观测、也能在卯酉方向观测的仪器,记录一颗恒星通过仪器卯酉方向和子午方向的三个时刻,就可以确定仪器在子午方向的方位角。这种方法所需要的观测时间短,工作简便,所测定的方位角是绝对的。     

卯酉圈观测测定子午环的绝对参数(Ⅱ)——绝对测定度盘的赤道点

本文继文章(Ⅰ)(绝对测定方位角)之后,叙述了用一颗恒星通过卯酉圈的观测记录时刻和中天时的天顶距测定值,,绝对确定度盘赤道点(或观测点的纬度值)的方法,并与传统的拱极星上、下中天观测方法作了比较。文章还就卯酉圈观测测定子午环绝对参数方法实施的可能性和适用的纬度范围进行了讨论。     

用卯酉圈观测绝对测定子午仪的方位角

本文介绍用改装后的中星仪,分别观测同一颗星过卯酉圈和子午圈的时刻,测定仪器绝对方位角的原理和试验结果.试验在云南天文台用蔡司中星仪进行,观测结果列在表1,试验表明方法是成功的。此法用在子午环上,可替代观测拱极星的方法来测定仪器的绝对方位角,从而避免观测拱极星的困难和因用方位标过渡引进的误差。     

星载氢钟VLBI观测实验及分析

中国计划于2025年左右建立月球轨道VLBI (Very Long Baseline Interferometer)测站,将会搭载被动型星载氢钟作为时间频率标准.由于是首次在VLBI观测中使用星载氢钟,需要研究和验证其可行性.因此,利用星载氢钟作为频率基准开展了VLBI观测.实验时,分别使用主动型地面氢钟和被动型星载氢钟作为频率基准,利用上海天文台佘山25 m射电望远镜和其他测站对我国火星探测器天问一号进行了交替VLBI观测.数据处理分析结果表明,基于地面氢钟与星载氢钟的VLBI残余群时延标准差均在0.5 ns以内,表明星载氢钟可满足深空探测VLBI测定轨的精度要求,验证了其作为月球VLBI测站频率基准的可行性.     

人造卫星观测的周日光行差的改正

本文讨论了人造卫星观测中卫星位置与测站位置所对应的时间不一致问题,证明了,对于方向观测,这种改正等价于卫星视位置到真位置的周日光行差的改正,并给出了其它观测的改正公式。经过这些改正后,在轨道改进时,星历表计算就可用最简单的时间对应的公式计算,不必进行迭代,也无需加任何附加项。     

人造卫星照相和双频观测资料定轨精度的初步分析

本文用模拟计算的方法,对人造卫星照相和双频观测资料的定轨精度进行了初步分析。给出了在测站坐标误差100米,测时误差0.002秒,位置误差2角秒,测速误差15厘米/秒的条件下,轨道根数中误差的最佳理论值。同时对测站坐标误差和测站分布对定轨精度的影响,也进行了初步的探讨。     

徐家汇观象台中星观测报告

本台中星观测所使用的仪器是法国帕兰(Prin)厂出品的80公里回转中星仪。并由超人差测微器与记时仪自动记录观测所得的时刻。观测结果的整理,则采用梅耶(Mayer)公式,恒星亦经以FK_3星表系统为根据。在观测每一颗星的时候,中星仪回转一次;即在星体中天前后,仪器顺放逆放各一次,借此消去视准差。所采用星体中天时刻,对于天顶以南的星体,是在中天前后各取10个数值平均而得;天顶以北的星(δ>31°11＇),为消除因其速率缓慢所引起的误差,故在中天前后,各取20个数值,再求平均值。     

小视场CCD图像的几何定标

针对长焦距望远镜CCD观测天然卫星的情况,导出了用两颗亮星作为定标时,CCD视场几何参数(比例尺和指向)测量的误差公式,进而设计了多定标星定标时正确的归算方案。新方案不仅对天然卫星的位置测量,也对同类型的小视场CCD位置测量具有指导意义。     

星表工作中子午方法与等高方法的比较

本文从观测原理、仪器参数、误差的主要来源及在星表工作中的局限性等方面,对子午方法和等高方法作了比较。子午方法原理简单,局限性小,绝对观测结果不依赖于工作星表,但仪器参数多,其变化难以控制,测定麻烦,只适于高纬度地区观测;等高方法原理复杂,仪器参数少,易于控制,但局限性大,观测结果不能完全独立于工作星表。本文就我国如何开展星位置绝对测定工作提出了看法     

Global adjustment of star positions for the compilation of independent catalogs

Presented is a method of global adjustment of stars' right ascensions for the compilation of an independent catalog obtained with a meridian circle. The concept of the problem is shown first, in which corrections to the catalog positions of observed stars can be determined directly by solving a set of observation equations constructed over many of nights. Some parameters such as clock correction, azimuth of artificial azimuth marks, and the correction to an adopted value of the latitude are assumed to vary regularly over the observation period. The present method is applied to the determination of the absolute azimuth of the Tokyo PMC by using upper and lower transits of azimuth stars.     

Determination of the azimuth error of the transit instrument by means of prime vertical observations

We present the principle and some test results of determining the instrumental azimuth by measuring the times of passage of the same stars through the meridian and the prime vertical. The test measurements were made on a reconstructed Zeiss transit instrument, equipped with four supporting pillars. The results of the test (TABLE 1) show that the method is successful. Applied to the meridian circle, this method replaces the traditional method of determining the absolute azimuth by observing circumpolar stars and thereby by-passes the difficulties inherant therein and the errors involved in the method of transfer via the azimuth mark.     

Super resolution for astronomical observations

In order to obtain detailed information from multiple telescope observations a general blind super-resolution (SR) reconstruction approach for astronomical images is proposed in this paper. A pixel-reliability-based SR reconstruction algorithm is described and implemented, where the developed process incorporates flat field correction, automatic star searching and centering, iterative star matching, and sub-pixel image registration. Images captured by the 1-m telescope at Yunnan Observatory are used to test the proposed technique. The results of these experiments indicate that, following SR reconstruction, faint stars are more distinct, bright stars have sharper profiles, and the backgrounds have higher details; thus these results benefit from the high-precision star centering and image registration provided by the developed method. Application of the proposed approach not only provides more opportunities for new discoveries from astronomical image sequences, but will also contribute to enhancing the capabilities of most spatial or ground-based telescopes.     

低纬子午环的研制过程

叙述了低纬子午环研制的全过程，从低纬度地区子午绝对测定方法的提出和验证，仪器几种主要误差测定方法的提出，到设计、加工和安装，最后叙述了在调试中遇到的几个主要问题和解决办法。文中还以与传统子午环比较的方式，论述了在对加工精度未提出苛刻要求的情况下如何能达到高精度测量的原因。     

用于自适应光学系统的激光引导星

自适应光学系统应用于天文观测时应满足一些技术要求,其中的关键技术之一是自适应光学系统为了对畸变的光波进行采样,需要在其很小的等晕角内有足够的信标强度。激光引导星,即人造信标,就是解决这种问题的方法之一。特别是在观测天文暗目标时,其自身的光强度不能为有探测提供信息,激光引导星就蛤得非常重要。根据国际上的最新进展对激光引导星技术给予了介绍。重点介绍了激光引导星的局限性,对近几年提出的对激光引导星可能的     

Star catalogue in the fields of axial meridian circle of the Nikolaev observatory

On the base of CCD-observations made with the axial meridian circle of the Nikolaev Observatory from 2008 to 2009, we compiled a catalogue for astrometric positions and proper motions for 140321 stars located in an ecliptic zone and around high proper motion stars. The root-meansquare error for a star position is 20–65 mas in right ascension and 30–70 mas in declination. The UCAC2 catalogue is used as a reference for astrometric reductions. To derive stars’ proper motion and to estimate systematic errors of the compiled catalogue, cross-identification of the obtained data with modern astronomic catalogues Tycho2, 2MASS, CMC14, LSPM, PPMX, USNO-A2, and XPM-1.0 is performed. In addition to star position and proper motion, our catalogue contains photometric values B, V, r’, J, H, and K taken from other catalogues.     

Use of Mathematic Morphological Operators for Processing the Smeared Images of A Camera without Shutter

In the observation of space objects with a full-frame transfer CCD camera, the camera shutter is often removed, and therefore the smeared images are produced, which affect seriously the object detection and location. Based on the difference of geometrical morphology between star images and smears, a mathematical morphology method is proposed to process the smeared images. By comparing the position accuracies of stars and space objects before and after processing, it is veri?ed that the morphological method can effectively remove the smears from astronomical images, and can signi?cantly improve the detection rates and position accuracies of stars and moving objects. The result indicates that this is an effective method to eliminate the smearing effect.     

两种快速星像匹配算法的比较

星像的位置和亮度等信息对天文研究和空间导航具有基础意义。人们常常需要快速匹配从密集星场CCD图像中提取的信息来获取与星表中对应的信息(如位置、光度等),因此开发出了多种星像匹配算法。重点比较了两种最新的星像匹配算法:i)基于向量的方法;ii)基于径向和环向特征的方法。通过对云南天文台1m望远镜观测的CCD图像进行实际匹配,结果表明基于向量的方法更优,它是一种快速的、接近常数时间的匹配算法。     

低纬子午环绝对测定瞬时方位差方法的改进（Ⅰ）

利用低纬子午环在卯酉圈东西两边同时观测得到的一对赤纬近似相等的恒星的天顶距，可以用来绝对确定仪器的瞬时方位差。这一方法不必对方位差的变化规律作任何假设，不需要改变现有的仪器设计方案。这将有利于改善低纬子午环的观测系统。