共查询到20条相似文献，搜索用时 31 毫秒
1.
VLBI (Very Long Baseline Interferometry)技术观测卫星需要对干涉测量数据进行相关和后处理,通过相关、时延校准、条纹搜索,最终得到卫星的基线几何时延.基于天文开源软件建立起一套卫星干涉测量数据处理系统.该系统可工作在实时和事后两种状态,实现相关、中性大气、电离层、钟模型以及仪器硬件的时延校准、条纹搜索、生成基线时延和时延率序列.使用该系统处理北斗GEO (Geosynchronous Earth Orbit)卫星的干涉测量试验数据,得到了精度在1–2 ns量级的卫星基线时延序列. 相似文献
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S. Kraus 《Astronomische Nachrichten》2014,335(1):51-58
Modern optical spectrographs and optical interferometers push the limits in the spectral and spatial regime, providing important new tools for the exploration of the Universe. In this contribution I outline the complementary nature of spectroscopic and interferometric observations and discuss different strategies for combining such data. Most remarkable, the latest generation of “spectro‐interferometric” instruments combine the milliarcsecond angular resolution achievable with interferometry with spectral capabilities, enabling direct constraints on the distribution, density, kinematics, and ionization structure of the gas component in protoplanetary disks. I will present some selected studies from the field of star‐ and planet formation and hot star research in order to illustrate these fundamentally new observational opportunities. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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由于地球电离层的阻挡以及其他干扰,在地面难以进行有效的甚低频天文观测,而使用搭载于绕地或绕月轨道卫星上的甚低频天线进行干涉观测会大大提高观测灵敏度和角分辨率.卫星定位精度会影响观测数据的处理结果,进而影响成图质量,并且会大幅影响飞行项目的复杂度和总成本.首先分析卫星姿态控制精度和星间基线测量精度对绕地轨道甚低频干涉观测的影响,之后对干涉观测中信号延时误差进行仿真,研究延时误差与数据相关处理中条纹搜索范围之间的关系,并对数据计算速度需求进行估算.分析和仿真结果可以辅助相关空间甚低频观测项目总体方案的制定和工程指标的优化. 相似文献
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闭合相位法是实现长基线恒星光干涉高分辨成像的重要技术手段之一,获得精确的闭合相位信息是进行光干涉图像重构的先决条件.提出一种基于精密光程差调制的时域干涉信号闭合相位检测方法,在3路干涉臂上进行非冗余精密光程调制,并通过多次干涉测量结合数据拟合的方法消除光程差调制中存在的正弦误差,使得光程调制的精度达到20 nm以内.引入高速探测器件提升时域干涉信号的采样频率,对探测器上获得的时域干涉信号进行傅立叶变换处理,获得3路干涉臂精确的闭合相位信息.室内实验结果表明,基于精密光程调制的时域信号闭合相位计算精度可以达到1/50波长以内. 相似文献
7.
D. Mouillet 《Astrophysics and Space Science》2003,286(1-2):3-15
As an introduction to the following talks, this presentation reviews the theoretical background of interferometric measurements.
Starting from a general formalism, I then emphasize the relationship between those measurements and the observed object properties.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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快速傅里叶变换(Fast Fourier Transform,FFT)比傅里叶变换有更好的算法性能,是射电干涉成像的基础算法,但因为天线阵列的不规则采样,需使用网格化算法将可见度数据重采样到规则的网格上才能应用。基于卷积的网格化计算具有密集型和迭代型的特点,特别是处理海量可见度数据的情况下,高性能的网格化计算对整个成像过程加速尤为重要。为了缓解数据处理的压力,在现有处理整块数据和支持多核计算的算法基础上,拓展应用Dask并行计算框架,不仅将数据分块并分配到多线程上,提高数值计算效率,而且动态的分布式任务调度策略优化了网格化的实时处理。实验结果表明,多核中央处理器利用率显著提高,即使增加数据量,也能进一步提高网格化算法的性能。分布式任务调度能够将单(多)测量集的网格化弹性缩放到单(多)机系统,充分发挥集群的规模化优势。 相似文献
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We present an interferometric technique for the reconstruction of ultra-wide band impulsive signals from point sources. This highly sensitive method was developed for the search for ultra-high energy neutrinos with the ANITA experiment but is fully generalizable to any antenna array detecting radio impulsive events. Applications of the interferometric method include event reconstruction, thermal noise and anthropogenic background rejection, and solar imaging for calibrations. We illustrate this technique with applications from the analysis of the ANITA-I and ANITA-II data in the 200–1200 MHz band. 相似文献
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Radiative Transfer (RT) codes with image capability are a fundamental tool for preparing interferometric observations and
for interpreting visibility data. In view of the upcoming VLTI facilities, we present the first comparison of images/visibilities
coming from two 3D codes that use completely different techniques to solve the problem of self-consistent continuum RT. In
addition, we focus on the astrophysical case of a disk distorted by tidal interaction with by-passing stars or internal planets
and investigate for which parameters the distortion can be best detected in the mid-infrared using the mid-infrared interferometric
device MIDI.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Sky models have been used in the past to calibrate individual low radio frequency telescopes. In this article we generalize this approach from a single antenna to a two element interferometer, and formulate the problem in a way that allows us to estimate the flux density of the Sun using the normalized cross-correlations (visibilities) measured on a low resolution interferometric baseline. For wide field-of-view instruments, typically the case at low radio frequencies, this approach can provide robust absolute solar flux calibration for well characterized antennas and receiver systems. It can provide a reliable and computationally lean method for extracting parameters of physical interest using a small fraction of the voluminous interferometric data, which can be computationally prohibitively expensive to calibrate and image using conventional approaches. We demonstrate this technique by applying it to data from the Murchison Widefield Array and assess its reliability. 相似文献
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Optical long-baseline interferometry is a unique and powerful technique for astronomical research. Since the 1980’s (with I2T, GI2T, Mark I to III, SUSI, ...), optical interferometers have produced an increasing number of scientific papers covering various fields of astrophysics. As current interferometric facilities are reaching their maturity, we take the opportunity in this paper to summarize the conclusions of a few key meetings, workshops, and conferences dedicated to interferometry. We present the most persistent recommendations related to science cases and discuss some key technological developments required to address them. In the era of extremely large telescopes, optical long-baseline interferometers will remain crucial to probe the smallest spatial scales and make breakthrough discoveries. 相似文献
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Accurate interferometric kinematic data suggest the interpretation of the brightest regions of NGC 6164-5 as a two-branched helical structure related to HD 148937 and having a systemic radial velocity nearly coincident with that of the tenuous surrounding medium; the gas in the helix could be the result of non-equatorial ejections from the central star. Morphologic, spectroscopic, and kinematic data would also indicate that the distance of 1.4 kpc proposed by Westerlund (1960) is substantially correct. 相似文献
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J. D. Gilmour O. V. Pravdivtseva A. Busfield C. M. Hohenberg 《Meteoritics & planetary science》2006,41(1):19-31
Abstract— We review the development of the I‐Xe technique and how its data are interpreted, and specify the best current practices. Individual mineral phases or components can yield interpretable trends in initial 129I/127I ratio, whereas whole‐rock I‐Xe ages are often hard to interpret because of the diversity of host phases, many of which are secondary. Varying standardizations in early work require caution; only samples calibrated against Shallowater enstatite or Bjurböle can contribute reliably to the emerging I‐Xe chronology of the early solar system. Although sparse, data for which I‐Xe and Mn‐Cr can be compared suggest that the two systems are concordant among ordinary chondrite samples. We derive a new age for the closure of the Shallowater enstatite standard of 4563.3 ± 0.4 Myr from the relationship between the I‐Xe and Pb‐Pb systems. This yields absolute I‐Xe ages and allows data from this and other systems to be tested by attempting to construct a common chronology of events in the early solar system. Absolute I‐Xe dates for aqueous and igneous processes are consistent with other systems. Consideration of the I‐Xe host phases in CAIs and dark inclusions demonstrates that here the chronometer records aqueous alteration of pre‐existing material. The ranges of chondrule ages deduced from the Al‐Mg and I‐Xe systems in Semarkona (LL3.0) and Chainpur (LL3.4) are consistent. Chainpur I‐Xe data exhibit a greater range of ages than Semarkona, possibly reflecting a greater degree of parent body processing. However individual chondrules show little or no evidence of such processing. Determining the host phase(s) responsible for high temperature correlations may resolve the issue. 相似文献
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Fabry-Perot interferometric observations of the λ5303 Å corona line on 22 September, 1968 were carried out. There are many elements of the interferometric rings with considerable line of sight velocities. The influence on the results of the changes in the brightness of the monochromatic and white-light corona were discussed. 相似文献
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A. M. Aliaga J. A. Rubiño-Martín E. Martínez-González R. B. Barreiro J. L. Sanz 《Monthly notices of the Royal Astronomical Society》2005,356(4):1559-1570
We adapt the smooth tests of goodness-of-fit developed by Rayner and Best to the study of the non-Gaussianity of interferometric observations of the cosmic microwave background (CMB). The interferometric measurements (visibilities) are transformed into signal-to-noise ratio eigenmodes, and then the method is applied directly in Fourier space. This transformation allows us to perform the analysis in different subsets of eigenmodes according to their signal-to-noise ratio level. The method can also deal with non-uniform or incomplete coverage of the UV plane. We explore here two possibilities: we analyse either the real and imaginary parts of the complex visibilities (Gaussianly distributed under the Gaussianity hypothesis) or their phases (uniformly distributed under the Gaussianity hypothesis). The power of the method in discriminating between Gaussian and non-Gaussian distributions is studied by using several kinds of non-Gaussian simulations. On the one hand, we introduce a certain degree of non-Gaussianity directly into the Fourier space using the Edgeworth expansion, and afterwards the desired correlation is introduced. On the other hand, we consider interferometric observations of a map with topological defects (cosmic strings). To these previous non-Gaussian simulations we add different noise levels and quantify the required signal-to-noise ratio necessary to achieve a detection of these non-Gaussian features. Finally, we have also studied the ability of the method to constrain the so-called non-linear coupling constant f NL using χ2 simulations. The whole method is illustrated here by application to simulated data from the Very Small Array interferometer. 相似文献
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This chapter gives some indications on the selection of suitable astronomical calibrators for interferometric observations. After an introduction to interferometric calibrations, we will focus on the criteria, steps and tools developed by ESO to prepare VLTI observations and to select calibrators. Although the tools described here are focused on VLTI, the problem of astronomical calibrators is the same for the other interferometers and can be approached in the same way. 相似文献
18.
InSAR技术现状与应用 总被引：6，自引：0，他引：6
合成孔径雷达干涉测量(InSAR)是近期发展起来的一种新型空间对地观测技术。经相干处理，它把合成孔径雷达(SAR)产生的单视复数图像中的相位信息提取出来，给出目标点的三维信息。由于SAR具有全天候、全天时和对某些地物有一定穿透性等特点，使InSAR技术的潜在应用领域相当广泛，目前已经成为地学界相关研究的热点之一。介绍了SAR和InSAR的基本原理与发展概况，分析了InSAR测量模式的测高精度，着重讨论了InSAR技术的应用及其与天文地球动力学研究的相互促进关系。 相似文献
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Robert I. Reid 《Monthly notices of the Royal Astronomical Society》2006,367(4):1766-1780
A new technique is presented for producing images from interferometric data. The method, 'smear fitting', makes the constraints necessary for interferometric imaging double as a model, with uncertainties, of the sky brightness distribution. It does this by modelling the sky with a set of functions and then convolving each component with its own elliptical Gaussian to account for the uncertainty in its shape and location that arises from noise. This yields much sharper resolution than clean for significantly detected features, without sacrificing any sensitivity. Using appropriate functional forms for the components provides both a scientifically interesting model and imaging constraints that tend to be better than those used by traditional deconvolution methods. This allows it to avoid the most serious problems that limit the imaging quality of those methods. Comparisons of smear fitting to clean and maximum entropy are given, using both real and simulated observations. It is also shown that the famous Rayleigh criterion (resolution = wavelength/baseline) is inappropriate for interferometers as it does not consider the reliability of the measurements. 相似文献