共查询到20条相似文献，搜索用时 135 毫秒
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稻城圆环阵太阳射电望远镜(Daocheng Solar Radio Telescope, DSRT)作为子午工程二期太阳-行星际探测子系统的重要部分, 工作在150--450MHz频段, 可提供高空间、高时间分辨率的太阳爆发亮温图像. 针对DSRT天线的高精度指向测量以及对指向误差批量标定和校正的需求, 首先根据DSRT独有的三轴座架系统, 通过四元数旋转变换法建立了天线3参数编码器零点误差模型; 然后提出了基于射电源的漂移扫描法获得16个单元天线功率方向图, 并根据2维方向图确定波束中心的方法精确测量了DSRT天线指向误差; 最后用最小二乘法拟合得到模型参数, 并通过天线控制软件重新调整各个轴的零点, 后对调整结果进行验证. 结果表明指向校正方法可靠有效, 校正后16个天线的指向精度为0.5$^\circ$之内, 明显优于校正前3.5$^\circ$的指向误差, 满足误差小于DSRT天线最高工作频率下的1/10波束范围内的要求. 相似文献
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天马13 m射电望远镜是专为空间大地测量的新一代甚长基线干涉测量(Very Long Baseline Interferometry, VLBI)天线,即VGOS(VLBI Global Observing System)系统。VGOS观测将从调度、相关、观测策略到分析各方面改变甚长基线干涉测量。与传统测地观测相比,VGOS观测将数据精度提高1～2个数量级。天马13 m射电望远镜安装了3～15 GHz宽频制冷接收机,一般要求天线指向偏差小于最高频率波束宽度的1/10。为满足高精度指向要求,详细介绍了建立指向的方法和天线控制扫描策略,给出了系统误差修正模型的完全表达式,明确了指向修正模型中的参数意义。基于该天线指向扫描的实测数据,实测评估了望远镜的指向精度。采用最小二乘法对覆盖全天区的数据样本进行拟合,得到天马13 m射电望远镜指向模型,并加载到天线伺服控制系统进行验证,得到了优于10″的盲指误差。 相似文献
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中国新一代厘米-分米波射电日像仪(Chinese Spectral Radio Heliograph,CSRH)项目已经完成了硬件建设.为了实现从数字接收机中读取观测数据,并将最新的可用数据状态通知其他子系统如监控系统和实时展现系统等,迫切需要一个稳定可靠的数据接收子系统.针对CSRH-I的特点及要求,在分析数字接收机原始数据格式的基础上,设计并实现了CSRH-I观测数据接收子系统.系统基于Linux环境,采用Boost软件包作为底层开发库,实现了基于TCP协议的网络套接服务器,能够异步接收、过滤数字接收机发送来的数据,经过相应的分析处理后最终以文件方式存储数据,进而采用UDP报文方式通知其它子系统观测数据的更新状态.本系统充分考虑了通信过程中可能的异常情况并采取了相应的对策.测试表明,CSRH-I观测数据接收子系统工作稳定可靠,容错能力强,可以满足CSRH-I的应用需求. 相似文献
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首先回顾了在现场射电望远镜天线性能的Y系数测量方法,指出如略加改进并利用射电望远镜自身接收机作测试接收机,则即能测出天线性能,又能测出接收机性能,详尽描述了这种改进方法。测量方法是模拟接收机输入端分别连接到50Ω终端、噪声源及天线输出端,且天线分别指向冷空和太阳。由测量方法得出4个传输方程,进而导出模拟接收机系统噪声温度、天线噪声温度、模拟接收机增益及天线增益与测试数据紧密联系的表达式。以一个射电望远镜测试数据为依据,算出相应系统参数并与设计指标要求进行了比对。小结中列出这种方法的优点,同时也讨论了现场测量天线增益的方向图法。 相似文献
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《天文学报》2017,(4)
讨论了TM65m射电望远镜Ku、K、Ka和Q4个高频段天线效率、灵敏度以及系统噪声温度的性能测量工作.首先介绍了TM65m接收系统4个高频段的关键指标,接着对测量工作中需要注意的方面进行了论述,主要包括望远镜指向和副面位姿模型的构建、噪声源的定标以及大气的影响.最后给出了TM65m在这4个频段的天线效率、灵敏度以及系统噪声温度的实测结果.测量结果表明:在最佳俯仰角45°-65°范围内,Ku、K、Ka和Q4个波段天线效率均可以达到约50%,而在较高和较低的俯仰角上,由于主面变形的缘故,效率有明显的下降现象.当俯仰角为50°左右时,4个波段的灵敏度分別为38 Jy、120 Jy、200 Jy和110 Jy. 相似文献
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北京天文台自1986年开始高时间分辨率的六厘米波段强度干涉仪的研制,计划在北京、昆明、乌鲁木齐设三个站,可发现角经0.01″的源。1988年初完成了北台单站接收系统,并取得了部分观测资料。主要性能如下:天线口径1.5米;接收频率5070±50MHz;高放噪声温度150K;中放带宽40MHz;系统时间常数0.2μs。系统见图1。采用前置微波高放未提高系统的灵敏度。用气体放电噪声管加15db定向耦合器组合作噪声标准源,以噪声源的输出温度为单位来测量每天的太阳强度m,由多日积累的m_i(i=1……n)与SGMR 4995MHz(引自S.G.D)的值取相关得线性相关参数a、b。由此得每天的绝对流量。目前只是初步的结果。表1为逐日的太阳射电强度m;SGMR 4995MHz;y;及黑子相对数Y。图2为V—m及y—m相关图,图上为S_p、S_n、Y及y的逐日变化图。表2为巡视观测中记录的部分爆发。六厘米强度干涉仪已取得的结果显示与太阳射电的国际频谱有很好的相关。三站(北京、昆明、乌鲁木齐)的强度干涉仪网建立后(1990年)所取得的高时间分辨率爆发的精细结构将具有极好的可靠性。该网将参加全国性的太阳活动联测。 相似文献
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射电望远镜天线结构设计和观测任务的正常进行都需要台址风场信息.随着望远镜性能要求的提高,天线结构设计越来越复杂,风载荷对天线观测时造成的指向影响也越发明显,如何在设计时保证结构刚度和强度,在观测时提高有效观测时间,都需要准确的风场数据.由于传统台址测风塔布置方法无法对测风塔拟设点的可靠性做出定量化评估,因此提出一种基于数值模拟优化测风塔位置的方法.数值模拟基于规范参数设置边界条件,与实测数据比较,整体趋势吻合,满足精度需求.对试验台址设置了4个测风塔位置,经分析P2点与天线位置的风速均方根误差值(root-mean-square error, RMSE)最小,测得的数据更能表征天线区域的风场特性. 相似文献
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A. M. Boichenko 《Astrophysics》2004,47(1):134-142
Observational data on the dynamics of stars in the neighborhood of the sun indicate the existence of a third integral besides the integrals of the angular momentum and energy. The Poincaré integral is proposed as a third integral. The consequences of this assumption are derived and compared with available astrophysical data. 相似文献
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耀变体(Blazars)的亮温度与黑洞喷流能量和吸积率有重要关系。搜集了53个耀变体源样本,包括22个蝎虎天体(BL Lacs)和31个平谱射电类星体(Flat Spectrum Radio Quasars,FSRQs),研究了耀变体亮温度与黑洞喷流能量的分布,并对子类中亮温度与黑洞喷流能量的相关性进行了讨论。研究结果表明:(1)蝎虎天体与平谱射电类星体的亮温度与黑洞喷流能量的分布存在明显差异,这可能与蝎虎天体与平谱射电类星体的内禀性质有关,也可能与其有无发射线及发射线的强弱有关;(2)蝎虎天体的亮温度与黑洞喷流能量之间的相关性较强,亮温度可以在一定程度上描述蝎虎天体的黑洞喷流能量,亮温度大的蝎虎天体喷流携带的能量也较大;(3)平谱射电类星体的亮温度与黑洞喷流能量之间有弱相关性,平谱射电类星体的亮温度不能清楚地描述黑洞喷流能量,黑洞喷流能量受亮温度影响较小,平谱射电类星体的黑洞喷流能量可能受到其他因素的影响;(4)耀变体的亮温度与黑洞吸积率之间有弱的相关性。 相似文献
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介绍和论述了在后牛顿引力理论(PPN形式)中在优越参考系和非优越参考系中经过参数化后引力常数变化对地球自转产生的效应,其中特别重点介绍了年周期变化的效应。此外也将理论结果同观测结果相对比。 相似文献
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Range of values of the Sun's mass quadrupole moment of coefficient J2 arising both from experimental and theoretical determinations enlarge across literature on two orders of magnitude, from
around 10-7 until to 10-5. The accurate knowledge of the Moon's physical librations, for which the Lunar Laser Ranging data reach an outstanding precision
level, prove to be appropriate to reduce the interval of J2 values by giving an upper bound of J2. A solar quadrupole moment as high as 1.1 10-5 given either from the upper bounds of the error bars of the observations, or from the Roche's theory, is not compatible with
the knowledge of the lunar librations accurately modeled and observed with the LLR experiment. The suitable values of J2 have to be smaller than 3.0 10-6.
As a consequence, this upper bound of 3.0 10-6 is accepted to study the impact of the Sun's quadrupole moment of mass on the dynamics of the Earth-Moon system. Such as
effect (with J2 = 5.5±1.3 × 10-6) has been already tested in 1983 by Campbell & Moffat using analytical approximate equations, and thus for the orbits of
Mercury, Venus, the Earth and Icarus. The approximate equations are no longer sufficient compared with present observational
data and exact equations are required. As if to compute the effect on the lunar librations, we have used our BJV relativistic
model of solar system integration including the spin-orbit coupled motion of the Moon. The model is solved by numerical integration.
The BJV model stems from general relativity by using the DSX formalism for purposes of celestial mechanics when it is about
to deal with a system of n extended, weakly self-gravitating, rotating and deformable bodies in mutual interactions.
The resulting effects on the orbital elements of the Earth have been computed and plotted over 160 and 1600 years. The impact
of the quadrupole moment of the Sun on the Earth's orbital motion is mainly characterized by variations of
,
, and
. As a consequence, the Sun's quadrupole moment of mass could play a sensible role over long time periods of integration of
solar system models.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Arbab I. Arbab 《Astrophysics and Space Science》2008,314(1-3):35-39
We have developed a cosmological model for the Earth rotation and planetary acceleration that gives a good account (data)
of the Earth astronomical parameters. These data can be compared with the ones obtained using space-base telescopes. The expansion
of the universe has shown to have an impact on the rotation of planets, and in particular, the Earth. The expansion of the
universe causes an acceleration that is exhibited by all planets. 相似文献
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I. Ilyin K.G. Strassmeier M. Woche F. Dionies I. Di Varano 《Astronomische Nachrichten》2011,332(8):753-758
We present the design concept of the spectropolarimeter for the high‐resolution echelle spectrograph PEPSI tobe installed at the 2 × 8.4 m Large Binocular Telescope (LBT) in Arizona. We discuss the optical key elements, the principles of operations of the instrument and its instrumental polarization effects (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Wu Lin-xiang 《Chinese Astronomy and Astrophysics》1992,16(4):427-433
By means of a simple relation between the velocity v of the fluid particle and the velocity vf of the photospheric footpoint of the magnetic field line vz and Bz being respectively the components of v and the magnetic field B normal to the photospheric surface, it is shown formally that through the phtospheric surface the transport of all the quantities attributed to the magnetic field, such as the magnetic flux, the magnetic energy and the helicity, is independent of vz, and vf is the only kinematical quantity on which the transport depends. In addition, in the neighborhood of the neutral line the velocity vl of the moving curve of constant Bz is found to be equal approximately to the component of v or vf in the direction of vl. Since vl can be measured or extimated, so can the components of v and vf near the neutral line. 相似文献
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L. S. Marochnik 《Astrophysics and Space Science》1983,89(1):61-75
The solar system's position in the Galaxy is an exclusive one, since the Sun is close to the corotation circle, which is the place where the angular velocity of the galactic differential rotation is equal to that of density waves displaying as spiral arms. Each galaxy contains only one corotation circle; therefore, it is an exceptional place. In the Galaxy, the deviation of the Sun from the corotation is very small — it is equal to ΔR/R ⊙≈0.03, where ΔR=R c ?R ⊙,R c is the corotation distance from the galactic center andR ⊙ is the Sun's distance from the galactic center. The special conditions of the Sun's position in the Galaxy explain the origin of the fundamental cosmogony timescalesT 1≈4.6×109 yr,T 2?108 yr,T 3?106 yr detected by the radioactive decay of various nuclides. The timescaleT 1 (the solar system's ‘lifetime’) is the protosolar cloud lifetime in a space between the galactic spiral arms. The timescaleT 2 is the presolar cloud lifetime in a spiral arm.T 3 is a timescale of hydrodynamical processes of a cloud-wave interaction. The possibility of the natural explanation of the cosmogony timescales by the unified process (on condition that the Sun is near the state of corotation) can become an argument in favour of the fact that the nearness to the corotation is necessary for the formation of systems similar to the Solar system. If the special position of the Sun is not incidental, then the corotation circles of our Galaxy, as well as those of other galaxies, are just regions where situations similar to ours are likely to be found. 相似文献
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Yoshio Kubo 《Celestial Mechanics and Dynamical Astronomy》1982,26(1):97-112
Perturbations in the motion of the Moon are computed for the effect by the oblateness of the Earth and for the indirect effect of planets. Based on Delaunay's analytical solution of the main problem, the computations are performed by a method of Fourier series operation. The effect of the oblateness of the Earth is obtained to the second order, partly adopting an analytical evaluation. Both in longitude and latitude are found a few terms whose coefficient differs from the current lunar ephemeris based on Brown's theory by about 0.01. While, concerning the indirect effect of planets, several periodic terms in the current ephemeris seem to have errors reaching 0.05.As for the secular variations of
and due to the figure of the Earth and the indirect effect of planets, the newly-computed values agree within 1/cy with Brown's results reduced to the same values of the parameters. Further, the accelerations in the mean longitude,
and caused by the secular changes in the eccentricity of the Earth's orbite and in the obliquity of the ecliptic are obtained. The comparison with Brown shows an agreement within 0.3/cy2 for the former cause and 0.02/cy2 for the latter. An error is found in the argument of the principal term for the perturbations due to the ecliptic motion in the current ephemeris.Proceedings of the Conference on Analytical Methods and Ephemerides: Theory and Observations of the Moon and Planets. Facultés universitaires Notre Dame de la Paix, Namur, Belgium, 28–31 July, 1980. 相似文献