共查询到20条相似文献，搜索用时 765 毫秒
1.
介绍了研究空间VLBI在大地测量等领域应用的意义,探讨了空间VLBI的观测量类型、观测模型及其涉及的大地测量所关心的参数;并采用1980～2004年的VLBI观测数据进行了计算,对大地测量所关心的几种参数的计算结果进行了分析. 相似文献
2.
《武汉大学学报(信息科学版)》2010,(6)
介绍了包括章动参数的空间VLBI数学模型,探讨了该模型用于大地测量解算的可行性;模拟了针对RADIOASTRON卫星的空间VLBI观测量及相关参数;利用所模拟的时延观测量研究分析包含章动参数的数学模型对EOP参数的可估计性,进而给空间VLBI数学模型中除EOP参数以外的参数赋予不同的先验误差,研究EOP参数对这些先验误差的灵敏度。 相似文献
3.
讨论了射电天线用于天文观测和VLBI大地测量时的几项性能参数;列出了我国现有射电天线组成系统时的工作性能和观测精度;计算了利用我国现有射电天线与FAST天线组成基线进行观测时的系统性能以及所要求射电源的最低流量密度.由此可以看出FAST天线用于VLBI观测具有巨大潜力. 相似文献
4.
讨论了射电天线用于天文观测和VLBI大地测量时的几项性能参数；列出了我国现有射电天线组成系统时的工作性能和观测精度；计算了利用我国现有射电天线与FAST天线组成基线进行观测时的系统性能以及所要求射电源的最低流量密度。由此可以看出FAST天线用于VLBI观测具有巨大潜力。 相似文献
5.
《武汉大学学报(信息科学版)》2010,(6)
结合国内外VLBI技术发展的历史、现状与动态,从天体测量、空间大地测量和深空探测等角度,对我国天测与测地VLBI观测网络的未来建设进行了需求分析和测站配置技术指标分析。 相似文献
6.
本文给出了上海、乌鲁木齐和昆明三个台站组成的VLBI网进行大地测量的射电源表，画出了这些射电源的天球分布图，计算了每颗射电源同时可被三个台站观测的时间图，利用它们可以编制观测计划表。 相似文献
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建立国家空间大地网的研究 总被引：2，自引：0，他引：2
本文就利用空间大地测量技术建立我国的空间大地网的目的、任务和布网设想进行了论证。在充分论证的基础上，从我国空间大地测量的现状出发，提供了利用VLBI、SLR和GPS技术布网的设想。 相似文献
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11.
WEI Erhu LIU Jingnan SHI Chuang 《地球空间信息科学学报》2007,10(1):12-16
The meaning to research the potential of VLBI for geodetic applications is summarized. And the observation models and their related parameters of geodetic interest are investigated. Then, the principle and method of using the random model in VLBI data processing are investigated. With the world wide VLBI data from 2000-2004, the conditions to compute the parameters of geodetic interest are introduced, and so are the computing methods and processes. And the computed results of the parameters of geodetic interest are analyzed. 相似文献
12.
We perform extensive simulations in order to assess the accuracy with which the position of a radio transmitter on the surface of the Moon can be determined by geodetic VLBI. We study how the quality and quantity of geodetic VLBI observations influence these position estimates and investigate how observations of such near-field objects affect classical geodetic parameters like VLBI station coordinates and Earth rotation parameters. Our studies are based on today’s global geodetic VLBI schedules as well as on those designed for the next-generation geodetic VLBI system. We use Monte Carlo simulations including realistic stochastic models of troposphere, station clocks, and observational noise. Our results indicate that it is possible to position a radio transmitter on the Moon using today’s geodetic VLBI with a two-dimensional horizontal accuracy of better than one meter. Moreover, we show that the next-generation geodetic VLBI has the potential to improve the two-dimensional accuracy to better than 5 cm. Thus, our results lay the base for novel observing concepts to improve both lunar research and geodetic VLBI. 相似文献
13.
差分VLBI测量的一种实现方案 总被引：1，自引：0，他引：1
差分VLBI通过交替观测目标天体和参考天体,将共同的误差因素从观测量中扣除,能够实现高精度的相对定位,因而在深空探测中有重要作用.然而,差分VLBI高精度的实现要求目标天体和参考天体的角距很近,这大大限制了其应用.讨论设计了差分VLBI测量的一种实现方案,利用多颗参考源的观测内插出目标源的非几何时延修正,放宽了对目标源和参考源的角距限制.该方案在S波段对目标源非几何时延的修正精度可以达到1 ns水平. 相似文献
14.
组合VLBI和SLR数据估计的全球板块运动参数 总被引：4，自引：0，他引：4
本文组合应用ＶＬＢＩ和ＳＬＲ数据导出了一个完全基于空间技术实测数据的现时板块运动模型，称为ＳＧＰＭＭ１。ＳＧＰＭＭ１与地学板块运动模型ＮＵＶＥＬ－１的比较指出：空间大地测量数据估计的板块运动总体上与地学估计值一致。经过地磁极倒转时间尺度修正，并考虑到冰斯后地壳回弹的影响，空间大地测量数据估计的北美，欧亚和澳大利亚板块之间的相对运动速率与地学估计值有极好的一致，但太平洋板块相对于北美、欧亚和澳大利亚 相似文献
15.
组合GPS和VLBI数据建立板块运动模型 总被引：6，自引：0，他引：6
利用GPS和VLBI的组合数据,解算了北美、欧亚、太平洋等12板块之间的相对运动欧拉矢量,得到了实测的板块运动模型GVM1。与地学模型(NUVEL1A)的比较指出,GVM1大体上与地学模型一致;EURANOAM的极位置与NUVEL1A的相应极比较接近,旋转速率略微偏大;澳大利亚板块在最近几年内是稳定的;太平洋板块与其他板块对的极位置与地学模型较为接近,这表明多种技术的组合数据提高了板块运动模型建立的精确性和可靠性。 相似文献
16.
Lucia Plank Andreas Hellerschmied Jamie McCallum Johannes Böhm Jim Lovell 《Journal of Geodesy》2017,91(7):867-880
The possibility of observing satellites with the very long baseline interferometry (VLBI) technique has been discussed for several years in the geodetic community, with observations of either existing satellites of the global navigation satellite systems or of satellites dedicated to realise a space tie. Such observations were carried out using the Australian telescopes in Hobart and Ceduna which, for the first time, integrated all the necessary steps: planning the observations (automated scheduling), correlation of the data and the generation of a series of time delay observables suitable for a subsequent geodetic analysis. We report on the development of new and the adaptation of existing routines for observing and data processing, focusing on technology development. The aim was to use methods that are routinely used in geodetic VLBI. A series of test experiments of up to six hours duration was performed, allowing to improve the observations from session to session and revealing new problems still to be solved. The newly developed procedures and programs now enable more observations. Further development assumed, this bears the prospect of being directly applied to the observation of dedicated space-tie satellites. 相似文献
17.
The source position time-series for many of the frequently observed radio sources in the NASA geodetic very long baseline
interferometry (VLBI) program show systematic linear and non-linear variations of as much as 0.5 mas (milli-arc-seconds) to
1.0 mas, due mainly to source structure changes. In standard terrestrial reference frame (TRF) geodetic solutions, it is a
common practice to only estimate a global source position for each source over the entire history of VLBI observing sessions.
If apparent source position variations are not modeled, they produce corresponding systematic variations in estimated Earth
orientation parameters (EOPs) at the level of 0.02–0.04 mas in nutation and 0.01–0.02 mas in polar motion. We examine the
stability of position time-series of the 107 radio sources in the current NASA geodetic source catalog since these sources
have relatively dense observing histories from which it is possible to detect systematic variations. We consider different
strategies for handling source instabilities where we (1) estimate the positions of unstable sources for each session they
are observed, or (2) estimate spline parameters or rate parameters for sources chosen to fit the specific variation seen in
the position-time series. We found that some strategies improve VLBI EOP accuracy by reducing the biases and weighted root
mean square differences between measurements from independent VLBI networks operating simultaneously. We discuss the problem
of identifying frequently observed unstable sources and how to identify new sources to replace these unstable sources in the
NASA VLBI geodetic source catalog. 相似文献
18.
Height bias and scale effect induced by antenna gravitational deformations in geodetic VLBI data analysis 总被引：2，自引：2，他引：0
The impact of signal path variations (SPVs) caused by antenna gravitational deformations on geodetic very long baseline interferometry
(VLBI) results is evaluated for the first time. Elevation-dependent models of SPV for Medicina and Noto (Italy) telescopes
were derived from a combination of terrestrial surveying methods to account for gravitational deformations. After applying
these models in geodetic VLBI data analysis, estimates of the antenna reference point positions are shifted upward by 8.9
and 6.7 mm, respectively. The impact on other parameters is negligible. To simulate the impact of antenna gravitational deformations
on the entire VLBI network, lacking measurements for other telescopes, we rescaled the SPV models of Medicina and Noto for
other antennas according to their size. The effects of the simulations are changes in VLBI heights in the range [−3, 73] mm
and a net scale increase of 0.3–0.8 ppb. The height bias is larger than random errors of VLBI position estimates, implying
the possibility of significant scale distortions related to antenna gravitational deformations. This demonstrates the need
to precisely measure gravitational deformations of other VLBI telescopes, to derive their precise SPV models and to apply
them in routine geodetic data analysis. 相似文献
19.
O. Titov 《Journal of Geodesy》2007,81(6-8):455-468
This paper evaluates the effect of the accuracy of reference radio sources on the daily estimates of station positions, nutation
angle offsets, and the estimated site coordinates determined by very long baseline interferometry (VLBI), which are used for
the realization of the international terrestrial reference frame (ITRF). Five global VLBI solutions, based on VLBI data collected
between 1979 and 2006, are compared. The reference solution comprises all observed radio sources, which are treated as global
parameters. Four other solutions, comprising different sub-sets of radio sources, were computed. The daily station positions
for all VLBI sites and the corrections to the nutation offset angles were estimated for these five solutions. The solution
statistics are mainly affected by the positional instabilities of reference radio sources, whereas the instabilities of geodetic
and astrometric time-series are caused by an insufficient number of observed reference radio sources. A mean offset of the
three positional components (Up, North, East) between any two solutions was calculated for each VLBI site. From a comparison
of the geodetic results, no significant discrepancies between the respective geodetic solutions for all VLBI sites in the
Northern Hemisphere were found. In contrast, the Southern Hemisphere sites were more sensitive to the selected set of reference
radio sources. The largest estimated mean offset of the vertical component between two solutions for the Australian VLBI site
at Hobart was 4 mm. In the worst case (if a weak VLBI network observed a limited number of reference radio sources) the daily
offsets of the estimated height component at Hobart exceeded 100 mm. The exclusion of the extended radio sources from the
list of reference sources improved the solution statistics and made the geodetic and astrometric time-series more consistent.
The problem with the large Hobart height component offset is magnified by a comparatively small number of observations due
to the low slewing rate of the VLBI dish (1°/ s). Unless a minimum of 200 scans are performed per 24-h VLBI experiment, the
daily vertical positions at Hobart do not achieve 10 mm accuracy. Improving the slew rate at Hobart and/or having an increased
number of new sites in the Southern Hemisphere is essential for further improvement of geodetic VLBI results for Southern
Hemisphere sites. 相似文献
20.
Kamil Teke Johannes B?hm Tobias Nilsson Harald Schuh Peter Steigenberger Rolf Dach Robert Heinkelmann Pascal Willis R��diger Haas Susana Garc��a-Espada Thomas Hobiger Ryuichi Ichikawa Shingo Shimizu 《Journal of Geodesy》2011,85(7):395-413
CONT08 was a 15 days campaign of continuous Very Long Baseline Interferometry (VLBI) sessions during the second half of August 2008 carried out by the International VLBI Service for Geodesy and Astrometry (IVS). In this study, VLBI estimates of troposphere zenith total delays (ZTD) and gradients during CONT08 were compared with those derived from observations with the Global Positioning System (GPS), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and water vapor radiometers (WVR) co-located with the VLBI radio telescopes. Similar geophysical models were used for the analysis of the space geodetic data, whereas the parameterization for the least-squares adjustment of the space geodetic techniques was optimized for each technique. In addition to space geodetic techniques and WVR, ZTD and gradients from numerical weather models (NWM) were used from the European Centre for Medium-Range Weather Forecasts (ECMWF) (all sites), the Japan Meteorological Agency (JMA) and Cloud Resolving Storm Simulator (CReSS) (Tsukuba), and the High Resolution Limited Area Model (HIRLAM) (European sites). Biases, standard deviations, and correlation coefficients were computed between the troposphere estimates of the various techniques for all eleven CONT08 co-located sites. ZTD from space geodetic techniques generally agree at the sub-centimetre level during CONT08, and??as expected??the best agreement is found for intra-technique comparisons: between the Vienna VLBI Software and the combined IVS solutions as well as between the Center for Orbit Determination (CODE) solution and an IGS PPP time series; both intra-technique comparisons are with standard deviations of about 3?C6?mm. The best inter space geodetic technique agreement of ZTD during CONT08 is found between the combined IVS and the IGS solutions with a mean standard deviation of about 6?mm over all sites, whereas the agreement with numerical weather models is between 6 and 20?mm. The standard deviations are generally larger at low latitude sites because of higher humidity, and the latter is also the reason why the standard deviations are larger at northern hemisphere stations during CONT08 in comparison to CONT02 which was observed in October 2002. The assessment of the troposphere gradients from the different techniques is not as clear because of different time intervals, different estimation properties, or different observables. However, the best inter-technique agreement is found between the IVS combined gradients and the GPS solutions with standard deviations between 0.2 and 0.7?mm. 相似文献