月球交会对接VLBI差分时延研究          下载免费PDF全文

郑鑫  刘庆会  吴亚军  马俊武  邓涛 《天文学报》2020,61(3):22

中国探月3期任务中,月球交会对接技术是任务成功的重要保障.利用嫦娥3号(CE03)绕月飞行的VLBI (Very Long Baseline Interferometry)时延数据,模拟仿真绕月交会对接过程中,同波束VLBI观测模式下,差分群时延的变化情况.仿真结果显示,在远程导引段,轨道器和上升组合体轨道距离保持100 km,持续半小时,差分群时延很好地反映了两者的轨道信息,可以用于定轨定位;自主控制段,上升组合体靠近轨道器,在轨道距离从5 km减小到20 m过程中,上升组合体加速追赶轨道器时,差分群时延快速趋近于0,上升组合体减速远离轨道器时,差分群时延绝对值快速变大.最后,利用嫦娥3号奔月段同时发射两个DOR (Differential One-Ranging)信号的VLBI时延数据,计算差分相时延,初步展示了月球交会对接过程中同波束VLBI差分相时延的误差情况.  相似文献   

ASO-S卫星工程科学应用系统的数据库设计          下载免费PDF全文

葛蕴翊  黎辉  黄宇  李敬伟  雷仕俊  藏京京  苏杨  封莉  李友平  李瑛  徐遵磊  李翔 《天文学报》2020,61(4):46

先进天基太阳天文台(Advanced Space-based Solar Observatory, ASO-S)卫星是我国首颗太阳观测卫星, 主要观测太阳耀斑和日冕物质抛射以及产生它们的磁场结构. ASO-S卫星的科学应用系统是科学卫星工程的6大系统之一, 它连接科学用户和卫星数据, 为将卫星的科学数据转化为科学成果提供保障. 科学应用系统的数据库是连接软件与海量数据的枢纽, 为科学数据生产和用户服务及运行提供数据层的支撑. 介绍了科学应用系统的数据库架构设计、数据库的选择以及数据库性能优化和表样例. 这里的数据库包括观测计划、工程参数、运维日志、科学数据、定标数据和特征事件识别等数据库. 这些数据库的建设将为ASO-S卫星工程科学应用系统的顺利运行提供数据支撑, 也可以为未来其他科学卫星类似数据库的搭建提供参考和借鉴.  相似文献   

The Review of γ-ray Astronomical Observing Techniques     

《Chinese Astronomy and Astrophysics》2021,45(3):281-300

$\gamma$-ray is a unique probe for extreme events in the universe. Detecting the $\gamma$-ray provides an important opportunity to understand the composition of universe, the evolution of stars, the origin of cosmic rays, etc. $\gamma$-ray astronomy involves in various frontier scientific issues, and the observed energy spectrum spans over a wide range from a few hundreds of keV to a few hundreds of TeV. Different $\gamma$-ray telescopes are in need for different scientific goals and spectral bands. In this work, 5 kinds of space- and ground-based $\gamma$-ray observing techniques were summarized, including the Coded-aperture telescopes, Compton telescopes, Pair-production telescopes, Imaging Atmospheric Cherenkov Telescopes, and Extensive Air Shower Arrays. The progress in $\gamma$-ray astronomy in the past 70 years, motivated by the observation capability, was reviewed. Great achievements have been made in the high-energy domain and very-high-energy domain, while because of the limited missions conducted, as well as a lower sensitivity comparing with other domains, discoveries in low- and medium-energy are few, and due to the high observation difficulty, as well as the late start, relevant scientific yields in ultra- and extremely-high energy are limited. Moreover, the future planned missions and capabilities of the $\gamma$-ray telescopes and their possible scientific outputs were discussed. Among these missions, low- and medium-energy space telescopes e-ASTROGAM (enhanced-ASTROGAM), AMEGO (All-sky Medium Energy Gamma-ray Observatory), and very-high-energy ground-based arrays LHAASO (Large High Altitude Air Shower Observatory) and CTA (Cherenkov Telescope Array) greatly improve sensitivity than their corresponding last generation, thus expect very likely to further expand our knowledge on the $\gamma$-universe.  相似文献   

Element Abundance Analysis of HD 140283 and Astrophysics Sources of Weak r-process Elements     

MA Wen-juan  LI Hong-jie  Zhang Lu  ZHANG Bo 《Chinese Astronomy and Astrophysics》2021,45(1):58-66

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Mattig's relation and dynamical distance indicators     

P. Teerikorpi  Yu. V. Baryshev 《Astronomische Nachrichten》2016,337(3):315-317

We discuss how the redshift (Mattig) method in the Friedmann cosmology relates to dynamical distance indicators based on Newton's gravity (Teerikorpi 2011). It belongs to the class of indicators where the relevant length inside the system is the distance itself (in this case the proper metric distance). As the Friedmann model has a Newtonian analogy, its use to infer distances has instructive similarities to classical dynamical distance indicators. In view of the theoretical exact linear distance‐velocity law, we emphasize that it is conceptually correct to derive the cosmological distance via the route: redshift (primarily observed) → space expansion velocity (not directly observed) → metric distance (physical length in “cm”). Important properties of the proper metric distance are summarized. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Chemical spots on the surface of the strongly magnetic Herbig Ae star HD 101412     

S. P. Jrvinen  S. Hubrig  M. Schller  I. Ilyin  T. A. Carroll  H. Korhonen 《Astronomische Nachrichten》2016,337(3):329-338

Due to the knowledge of the rotation period and the presence of a rather strong surface magnetic field, the sharp‐lined young Herbig Ae star HD 101412 with a rotation period of 42 d has become one of the most well‐studied targets among the Herbig Ae stars. High‐resolution HARPS polarimetric spectra of HD 101412 were recently obtained on seven different epochs. Our study of the spectral variability over the part of the rotation cycle covered by HARPS observations reveals that the line profiles of the elements Mg, Si, Ca, Ti, Cr, Mn, Fe, and Sr are clearly variable while He exhibits variability that is opposite to the behaviour of the other elements studied. Since classical Ap stars usually show a relationship between the magnetic field geometry and the distribution of element spots, we used in our magnetic field measurements different line samples belonging to the three elements with the most numerous spectral lines, Ti, Cr, and Fe. Over the time interval covered by the available spectra, the longitudinal magnetic field changes sign from negative to positive polarity. The distribution of field values obtained using Ti, Cr, and Fe lines is, however, completely different compared to the magnetic field values determined in previous low‐resolution FORS 2 measurements, where hydrogen Balmer lines are the main contributors to the magnetic field measurements, indicating the presence of concentration of the studied iron‐peak elements in the region of the magnetic equator. Further, we discuss the potential role of contamination by the surrounding warm circumstellar matter in the appearance of Zeeman features obtained using Ti lines. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Sunspot numbers based on historic records in the 1610s: Early telescopic observations by Simon Marius and others     

R. Neuhuser  D. L. Neuhuser 《Astronomische Nachrichten》2016,337(6):581-620

Hoyt & Schatten (1998) claim that Simon Marius would have observed the sun from 1617 Jun 7 to 1618 Dec 31 (Gregorian calendar) all days, except three short gaps in 1618, but would never have detected a sunspot – based on a quotation from Marius in Wolf (1857), but mis‐interpreted by Hoyt & Schatten. Marius himself specified in early 1619 that for one and a half year... rather few or more often no spots could be detected... which was never observed before (Marius 1619). The generic statement by Marius can be interpreted such that the active day fraction was below 0.5 (but not zero) from fall 1617 to spring 1619 and that it was 1 before fall 1617 (since August 1611). Hoyt & Schatten cite Zinner (1952), who referred to Zinner (1942), where observing dates by Marius since 1611 are given but which were not used by Hoyt & Schatten. We present all relevant texts from Marius where he clearly stated that he observed many spots in different form on and since 1611 Aug 3 (Julian) = Aug 13 (Greg.) (on the first day together with Ahasverus Schmidnerus); 14 spots on 1612 May 30 (Julian) = Jun 9 (Greg.), which is consistent with drawings by Galilei and Jungius for that day, the latter is shown here for the first time; at least one spot on 1611 Oct 3 and/or 11 (Julian), i.e. Oct 13 and/or 21 (Greg.), when he changed his sunspot observing technique; he also mentioned that he has drawn sunspots for 1611 Nov 17 (Julian) = Nov 27 (Greg.); in addition to those clearly datable detections, there is evidence in the texts for regular observations. For all the information that can be compared to other observers, the data from Marius could be confirmed, so that his texts are highly credible. We also correct several shortcomings or apparent errors in the database by Hoyt & Schatten (1998) regarding 1612 (Harriot), 1615 (Saxonius, Tard´e), 1616 (Tard´e), 1617–1619 (Marius, Riccioli/Argoli), and Malapert (for 1618, 1620, and 1621). Furthermore, Schmidnerus, Cysat, David & Johann Fabricius, Tanner, Perovius, Argoli, and Wely are not mentioned as observers for 1611, 1612, 1618, 1620, and 1621 in Hoyt & Schatten. Marius and Schmidnerus are among the earliest datable telescopic sunspot observers (1611 Aug 3, Julian), namely after Harriot, the two Fabricius (father and son), Scheiner, and Cysat. Sunspots records by Malapert from 1618 to 1621 show that the last low‐latitude spot was seen in Dec 1620, while the first high‐latitude spots were noticed in June and Oct 1620, so that the Schwabe cycle turnover (minimum) took place around that time, which is also consistent with the sunspot trend mentioned by Marius and with naked‐eye spots and likely true aurorae. We consider discrepancies in the Hoyt & Schatten (1998) systematics, we compile the active day fractions for the 1610s, and we critically discuss very recent publications on Marius which include the following Maunder Minimum. Our work should be seen as a call to go back to the historical sources. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Application of the relativistic precession model to the accreting milisecond X‐ray pulsar IGR J17511–3057     

I. Zh. Stefanov 《Astronomische Nachrichten》2016,337(3):246-253

The observation of a pair of simultaneous twin kHz QPOs in the power density spectrum of a neutron star or a black hole allows its mass‐angular‐momentum relation to be constrained. Situations in which the observed simultaneous pairs are more than one allow the different models of the kHz QPOs to be falsified. Discrepancy between the estimates coming from the different pairs would call the used model into question. In the current paper, the relativistic precession model is applied to the twin kHz QPOs that appear in the light curves of three groups of observations of the accreting millisecond X‐ray pulsar IGR J17511–3057. It was found that the predictions of one of the groups are practically in conflict with the other two. Another interesting result is that the region in which the kHz QPOs have been born is rather broad and extends quite far from the ISCO. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

CTK‐II & RTK: The CCD‐cameras operated at the auxiiary telescopes of the University Observatory Jena     

M. Mugrauer 《Astronomische Nachrichten》2016,337(3):226-234

The Cassegrain‐Teleskop‐Kamera (CTK‐II) and the Refraktor‐Teleskop‐Kamera (RTK) are two CCD‐imagers which are operated at the 25 cm Cassegrain and 20cm refractor auxiliary telescopes of the University Observatory Jena. This article describes the main characteristics of these instruments. The properties of the CCD‐detectors, the astrometry, the image quality, and the detection limits of both CCD‐cameras, as well as some results of ongoing observing projects, carried out with these instruments, are presented. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Optimisation of the Population Monte Carlo algorithm: Application to constraining isocurvature models with cosmic microwave background data     

D. Moodley  K. Moodley 《Astronomische Nachrichten》2016,337(6):672-682

We optimise the parameters of the Population Monte Carlo algorithm using numerical simulations. The optimisation is based on an efficiency statistic related to the number of samples evaluated prior to convergence, and is applied to a D ‐dimensional Gaussian distribution to derive optimal scaling laws for the algorithm parameters. More complex distributions such as the banana and bimodal distributions are also studied. We apply these results to a cosmological parameter estimation problem that uses CMB anisotropy data from the WMAP nine‐year release to constrain a six parameter adiabatic model and a fifteen parameter admixture model, consisting of correlated adiabatic and isocurvature perturbations. In the case of the adiabatic model and the admixture model we find that the number of sample points increase by factors of 3 and 20, respectively, relative to the optimal Gaussian case. This is due to degeneracies in the underlying parameter space. The WMAP nine‐year data constrain the admixture model to have an isocurvature fraction of 36.3 ± 2.8 %. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献