共查询到19条相似文献,搜索用时 140 毫秒
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建立在子午-卯酉交替观测原理基础上的低纬子午环即将出投入试及试运动阶段,进一步研究天文蒙气差修正将是低纬子午环进行高精度观测的 重要保证之一。 相似文献
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本文简述了大气等密度层倾斜对天体测量观测结果的影响,根据低纬子午环绝对测定瞬时大气折射的原理,提出了利用子午方向和卯酉方向交替观测,测定大气等密层倾斜的方法推导了解算倾斜量的公式,并对测定精度作了估计。 相似文献
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针对空间大地测量技术对中性大气折射延迟改正精度的要求,阐述了折射延迟改正值应随测站和随方位而异的必要性.指出,在尚不能直接测定天文大气折射值的情况下,现有的各种改正模型对大气分布模型的依赖性,不能达到预期的精度和降低观测的截止角.根据云南天文台低纬子午环的特殊结构,和测定大气折射的实践,提出了提高折射延迟改正精度的新方法,即:利用各观测站不同方位从天顶附近直到低地平高度角的天文大气折射实测数据,求解得到折射率差和映射函数的参数,从而建立随测站和随方位而异的大气折射延迟改正模型.这一新方法的实施,将能在不需采用大气分布模型的情况下,把天顶延迟的改正精度提高到1 mm以内,低地平高度角的折射延迟改正精度提高到厘米级,并且把截止高度角压缩到5°以内. 相似文献
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本文对LLMC+CCD仪器系统的误差理论进行了综合性的探讨。文中所涉及的误差主要来自两方面:其一是来自仪器系统本身的误差,其二是来自仪器系统以外的误差。论文的第一章对CCD器件的特性及其在天文学上的应用作了扼要介绍;第二章阐述了低纬子午环配备CCD的观测方法,还简述了低纬子午环的结构及观测原理;第三章对十七种不同类型误差的测定或消除方法作了详尽的探讨和分析;第四章推导了星径曲率改正;第五章对小角度天体测量技术和大角度天体测量技术进行了评估。 相似文献
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本文介绍了低纬子午环上电水准器的工作原理;讨论了电水准器在测定定位盘上盘的水平差时,其Deticon的比例尺的测定方法及其测量精度;讨论了电水准器中狭缝倾斜量的测量方法;最后给出了水平差的测量范围以及可达到的精度,证明低纬子午环对轴系的要求是比较低的,而水平差的测量精度是相当高的。 相似文献
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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。 相似文献
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天文折射中包含有显著的光谱型效应。本文从有效波长的角度,讨论了光谱型效应的复杂性,不同的仪器采用不同的接受器、以及在不同的天顶距观测,都有不同的光谱型差。提出在低纬子午环上,对不同光谱型的天体测定出天文折射,以提高星位测定的精度。 相似文献
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Hao-jian Yan 《Chinese Astronomy and Astrophysics》1998,22(4):200-496
In this paper we used the method of generator function to gave an improved mapping function of astronomical refraction, separately for optical and radio frequencies. We included a complete consideration of the corrections introduced by the physical and geophysical factors required in astronomy and space techniques. We used sounding balloon data to assess the actual accuracy of our corrected refraction formula. The result is 5″ at elevation 2° and 1″ at elevation 5°. We believe that the main factor that limits the accuracy is departure of the model atmosphere from the real atmosphere. 相似文献
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回顾了作为实用天文学和大地测量学中基本研究课题之一的大气折射函数研究的最新进展;介绍了近几年发展的大气折射母函数方法。对如今广泛地应用在空间测量技术中的几种映射函数,如CfA2.2、MTT等模型作出评述;特别分析了NMF模型的优点和不足之处。还介绍了由大气折射母函数方法引出的大气延迟新连分式映射函数和天文大气折射的映射函数方法,利用VLBI实验中高度截止角与基线长变化的关系和探空气球(radios 相似文献
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A. Ong R. D. Bhattacharya C. E. Covault D. D. Dixon D. T. Gregorich D. S. Hanna S. Oser J. Qu bert D. A. Smith O. T. Tü mer A. D. Zych 《Astroparticle Physics》1996,5(3-4):353-365
There is considerable interest world-wide in developing large area atmospheric Cherenkov detectors for ground-based gamma-ray astronomy. This interest stems, in large part, from the fact that the gamma-ray energy region between 20 and 250 GeV is unexplored by any experiment. Atmospheric Cherenkov detectors offer a possible way to explore this region, but large photon collection areas are needed to achieve low energy thresholds. We are developing an experiment using the heliostat mirrors of a solar power plant as the primary collecting element. As part of this development, we built a detector using four heliostat mirrors, a secondary Fresnel lens, and a fast photon detection system. In November 1994, we used this detector to record atmospheric Cherenkov radiation produced by cosmic ray particles showering in the atmosphere. The detected rate of cosmic ray events was consistent with an energy threshold near 1 TeV. The data presented here represent the first detection of atmospheric Cherenkov radiation using solar heliostats viewed from a central tower. 相似文献
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Focusing on lowering the cut-off elevation in the neutral atmosphere refraction delay correction and on raising the accuracy of the correction, we derive the formulae for calculating the correction for the bending of the light path caused by atmospheric refraction. This is the sort of correction that is given after the principal term in theoretical models of neutral atmospheric refraction delay correction, but is often neglected because it is a small quantity. However, in practice, for a not too low elevation like 15°, this term reaches 1 cm order of magnitude and can not be neglected. Li Yan-xing et al. specially gave a derivation of this correction and a computational method by successive approximation and some calculated values. Yan Hao-jian also proposed a formula of direct calculation but his calculated result was more than 3 times smaller than that of Li Yan-xing, which shows that further study of this correction is called for. Here we give a simple, convenient and reliable formula for calculating the correction. 相似文献
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Atmospheric optics is the study of optical effects induced by the atmosphere on light propagating from distant sources. Of particular concern to astronomers is atmospheric turbulence, which limits the performance of ground-based telescopes. The past two decades have seen remarkable growth in the capabilities and performance of adaptive optics (AO) systems. These opto-mechanical systems actively compensate for the blurring effect of the Earth’s turbulent atmosphere. By sensing, and correcting, wavefront distortion introduced by atmospheric index-of-refraction variations, AO systems can produce images with resolution approaching the diffraction limit of the telescope at near-infrared wavelengths. This review highlights the physical processes and fundamental relations of atmospheric optics that are most relevant to astronomy, and discusses the techniques used to characterize atmospheric turbulence. The fundamentals of AO are then introduced and the many types of advanced AO systems that have been developed are described. The principles of each are outlined, and the performance and limitations are examined. Aspects of photometric and astrometric measurements of AO-corrected images are considered. The paper concludes with a discussion of some of the challenges related to current and future AO systems, particularly those that will equip the next generation of large, ground-based optical and infrared telescopes. 相似文献
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本文综述了电离层、对流层中电波折射引起的射电天文观测及卫星测地中的各种误差及各种改正方法和它们的精度。 对流层影响的主要改正方法是实测大气温度、压力等参数,用数学模型计算。电离层影响的改正目前有三种方法:一是实时测量电离层主要参数——电子总含量的变化,然后用数学模型方法改正。二是采用双频同时观测的手段来消除电离层折射的影响。三是采用自校准方法。文中还比较了两种不同的自校准方法——常规自校准方法和多余量自校准方法。 相似文献