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1.
中国VLBI网软件相关处理机测地应用精度分析 总被引：1，自引：1，他引：0
为支持国际VLBI大地测量数据处理,中国VLBI网(CVN)软件相关处理机完成了功能、性能升级,提高了信噪比,实现了以国际测地通用Mk4格式数据输出结果,可以直接被VLBI通用测地后处理软件用于时延数据解算。本文通过与国外软件相关处理机DiFX的实测数据比对,系统地分析了CVN软件处理机带宽综合残余时延和时延率精度、带宽综合总时延和时延率精度、信噪比和VLBI站坐标解算值。数据显示,CVN软件相关处理机已经达到了测地数据处理的精度要求,可以用于IVS国际联测数据处理。 相似文献
2.
在国际甚长基线干涉测量（very long baseline interferometry, VLBI）大地测量与天体测量服务组织协调下,首次利用隶属于VLBI全球观测系统（VLBI global observing system, VGOS）的美国Kokee和德国Wettzell观测站及并置的传统VLBI观测站开展了世界时（universal time, UT1）联合测量试验,观测数据在上海VLBI中心进行了干涉处理。结果表明,VGOS超宽带观测系统的UT1测量精度约为7 μs,并置基线的传统S/X双频系统测量精度约为14 μs,VGOS系统的UT1解算结果优于S/X系统。通过试验建立了从相关处理、相关后处理到UT1参数解算的完整数据处理流程,验证了上海VLBI相关处理机的VGOS数据处理能力,为承担国内和国际VGOS观测数据的相关处理任务奠定了基础。 相似文献
3.
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
4.
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
5.
New VLBI2010 scheduling strategies and implications on the terrestrial reference frames 总被引：1，自引：1，他引：0
Jing Sun Johannes Böhm Tobias Nilsson Hana Krásná Sigrid Böhm Harald Schuh 《Journal of Geodesy》2014,88(5):449-461
In connection with the work for the next generation VLBI2010 Global Observing System (VGOS) of the International VLBI Service for Geodesy and Astrometry, a new scheduling package (Vie_Sched) has been developed at the Vienna University of Technology as a part of the Vienna VLBI Software. In addition to the classical station-based approach it is equipped with a new scheduling strategy based on the radio sources to be observed. We introduce different configurations of source-based scheduling options and investigate the implications on present and future VLBI2010 geodetic schedules. By comparison to existing VLBI schedules of the continuous campaign CONT11, we find that the source-based approach with two sources has a performance similar to the station-based approach in terms of number of observations, sky coverage, and geodetic parameters. For an artificial 16 station VLBI2010 network, the source-based approach with four sources provides an improved distribution of source observations on the celestial sphere. Monte Carlo simulations yield slightly better repeatabilities of station coordinates with the source-based approach with two sources or four sources than the classical strategy. The new VLBI scheduling software with its alternative scheduling strategy offers a promising option with respect to applications of the VGOS. 相似文献
6.
Alessandra Bertarini Alan L. Roy Brian Corey R. Craig Walker Walter Alef Axel Nothnagel 《Journal of Geodesy》2011,85(10):715-721
Geodetic very long baseline interferometry (VLBI) delivers time series of station positions and Earth orientation parameters.
These series offer a viable and precise way to study Earth crustal and core dynamics and to support space navigation. Their
accuracy is degraded by instrumental errors, of which polarization leakage is considered to be one of the largest that is
not yet being addressed. Its effect on the data can be corrected, provided one knows the leakage characteristics of the receivers.
For this purpose, we designed a VLBI session to measure the polarization leakage at 15 geodetic and very long baseline array
stations over the frequency range from 8,212.99 to 8,932.99 MHz. We describe the polarization leakage measurements and the
algorithm that was implemented to correct for its effect on the geodetic delay observables. Subsequently, we applied the correction
for polarization leakage to the same data that were used to determine the leakage and checked for the resulting improvement.
From the measured leakage terms, one would expect polarization leakage to affect the group delay measurements in 90% of the
cases by 1.6 ps or less. This proved to be below the statistical noise in our single VLBI session, and hence, an improvement
from the correction could not be detected. Applying this analysis in the context of VLBI2010, we provide a specification for
the allowable polarization leakage to achieve the target submillimetre accuracy. 相似文献
7.
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
8.
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
9.
Natalia Panafidina Urs Hugentobler Manuela Seitz Hana Krásná 《Journal of Geodesy》2017,91(12):1503-1512
This paper studies the connection between the subdaily model for polar motion used in the processing of very long baseline interferometry (VLBI) observations and the estimated nutation offsets. By convention accepted by the International Earth Rotation Service, the subdaily model for polar motion recommended for routine processing of geodetic observations does not contain any daily retrograde terms due to their one-to-one correlation with the nutation. Nevertheless, for a 24-h VLBI solution a part of the signal contained in the polar motion given by the used subdaily model is numerically mistaken for a retrograde daily sidereal signal. This fictitious retrograde daily signal contributes to the estimated nutation, leading to systematic differences between the nutation offsets from VLBI solutions computed with different subdaily polar motion models. We demonstrate this effect using solutions for all suitable 24-h VLBI sessions over a time span of 11 years (2000–2011). By changing the amplitudes of one tidal term in the underlying subdaily model for polar motion and comparing the estimated parameters to the solutions computed with the unchanged subdaily model, the paper shows and explains theoretically the effects produced by the individual subdaily terms on the VLBI nutation estimates. 相似文献
10.
Our present relativistic part of the geodetic VLBI model for Earthbound antennas is a consensus model which is considered as a standard for processing high-precision VLBI observations. It was created as a compromise between a variety of relativistic VLBI models proposed by different authors as documented in the IERS Conventions 2010. The accuracy of the consensus model is in the picosecond range for the group delay but this is not sufficient for current geodetic purposes. This paper provides a fully documented derivation of a new relativistic model having an accuracy substantially higher than one picosecond and based upon a well accepted formalism of relativistic celestial mechanics, astrometry and geodesy. Our new model fully confirms the consensus model at the picosecond level and in several respects goes to a great extent beyond it. More specifically, terms related to the acceleration of the geocenter are considered and kept in the model, the gravitational time-delay due to a massive body (planet, Sun, etc.) with arbitrary mass and spin-multipole moments is derived taking into account the motion of the body, and a new formalism for the time-delay problem of radio sources located at finite distance from VLBI stations is presented. Thus, the paper presents a substantially elaborated theoretical justification of the consensus model and its significant extension that allows researchers to make concrete estimates of the magnitude of residual terms of this model for any conceivable configuration of the source of light, massive bodies, and VLBI stations. The largest terms in the relativistic time delay which can affect the current VLBI observations are from the quadrupole and the angular momentum of the gravitating bodies that are known from the literature. These terms should be included in the new geodetic VLBI model for improving its consistency. 相似文献
11.
Summary In the last three years, the European Geodetic Very Long Baseline Interferometry (VLBI) Network has grown to a total of six fixed antennas placed in Germany, Italy, Spain and Sweden, all equipped with the standard geodetic VLBI instrumentation and data recording systems. During this period of time, several experiments have been carried out using this interferometer providing data of very high quality due to the excellent sensitivity and performance of the European stations. The purpose of this paper is to study the consistency of the VLBI geodetic results on the European baselines with respect to the different degrees of freedom in the analysis procedure. In order to complete this study we have made use of both real and simulated data sets, two different software packages (OCCAM 3.0 and CALC 7.4/SOLVE) and a variety of strategies in the data analysis. The results we have obtained show that the repeatability of the VLBI estimates of the baseline lengths in the European network is better than one centimeter, independent of the different analysis methods, and is consistent with the formal error levels expected from the data analysis. This consistency should be enough to produce geophysically significant information in Europe from VLBI data within a relatively short time span. 相似文献
12.
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
13.
European geodetic very long baseline interferometry (VLBI) sessions (also known as EUROPE sessions) have been carried out
on a regular basis for the past 15 years to study relative crustal motions within Europe. These sessions are based on observations
of extragalactic radio sources, which serve as distant fiducial marks to establish an accurate and stable celestial reference
frame for long-term geodetic measurements. The radio sources, however, are not always point-like on milliarcsecond scales,
as VLBI imaging has revealed. In this work, we quantify the magnitude of the expected effect of intrinsic source structure
on geodetic bandwidth synthesis delay VLBI measurements for a subset of 14 sources regularly observed during the EUROPE sessions.
These sources have been imaged at both X-band (8.4 GHz) and S-band (2.3 GHz) based on dedicated observations acquired with
the European VLBI Network (EVN) in November 1996. The results of this calculation indicate that the reference source 0457+024
causes significant structural effects in measurements obtained on European VLBI baselines (about 10 picoseconds on average),
whereas most of the other sources produce effects that are only occasionally larger than a few picoseconds. Applying the derived
source structure models to the data of the EUROPE5-96 session carried out at the same epoch as the EVN experiment shows no
noticeable changes in the estimated VLBI station locations. 相似文献
14.
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
15.
Monte Carlo simulations of the impact of troposphere,clock and measurement errors on the repeatability of VLBI positions 总被引：6，自引：5，他引：1
Within the International VLBI Service for Geodesy and Astrometry (IVS) Monte Carlo simulations have been carried out to design
the next generation VLBI system (“VLBI2010”). Simulated VLBI observables were generated taking into account the three most
important stochastic error sources in VLBI, i.e. wet troposphere delay, station clock, and measurement error. Based on realistic
physical properties of the troposphere and clocks we ran simulations to investigate the influence of the troposphere on VLBI
analyses, and to gain information about the role of clock performance and measurement errors of the receiving system in the
process of reaching VLBI2010’s goal of mm position accuracy on a global scale. Our simulations confirm that the wet troposphere
delay is the most important of these three error sources. We did not observe significant improvement of geodetic parameters
if the clocks were simulated with an Allan standard deviation better than 1 × 10−14 at 50 min and found the impact of measurement errors to be relatively small compared with the impact of the troposphere.
Along with simulations to test different network sizes, scheduling strategies, and antenna slew rates these studies were used
as a basis for the definition and specification of VLBI2010 antennas and recording system and might also be an example for
other space geodetic techniques. 相似文献
16.
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
17.
OCCAM V6．0是在PC机上开发的一套VLBI大地测量数据处理软件。该软件用标准FORTRAN77(90)语言编写，可在Windows95以上版本和LINUX环境下的PC机上运行，其主要特点是操作简便、兼容性好、处理容量大、速度快和结果输出多样化等。随着该软件的不断改进和发展，利用OCCAM进行VLBI数据分析的学者逐渐增多，OCCAM软件的使用也日益广泛。本文简要介绍了OCCAM软件的安装、各个模块的主要功能和在运行中的注意事项，供今后OCCAM用户在使用过程中参考。 相似文献
18.
The GEOSAT software for satellite geodetic and geodynamics applications has lately been extended to Very Long Baseline Interferometry (VLBI) applications. Geodetic VLBI data have been analyzed using this software and station coordinates and velocities, source coordinates, and earth orientation parameters have been derived in a global mode using data from the Extended Research and Development Experiment (ERDE) and the Research and Development series (R&D) within the NASA's CDP.It is demonstrated using the ERDE data, that the program is capable of calculating station coordinates with an accuracy of a few mm in the local horizontal plane and about 7 mm in the vertical direction. Analysis of the R&D dataset yields errors 2 to 3 times higher in all directions. 相似文献
19.
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
20.
Y. Fukuzaki K. Shibuya K. Doi T. Ozawa A. Nothnagel T. Jike S. Iwano D. L. Jauncey G. D. Nicolson P. M. McCulloch 《Journal of Geodesy》2005,79(6-7):379-388
The first successful geodetic Very Long Baseline Interferometry (VLBI) observations to Antarctica were made on baselines from Syowa Station (Antarctica) to Tidbinbilla (Australia) and to Kashima (Japan) in January 1990. Regular geodetic experiments started in 1998 with the installation of a permanent VLBI terminal at Syowa Station. These observations are conducted at the standard geodetic VLBI frequencies of 2.3 and 8.4 GHz, S- and X-Bands. In the first year, the 11-m multipurpose antenna at Syowa Station observed together with the 26-m radio telescope of the University of Tasmania in Australia and the 26-m radio telescope of the Hartebeesthoek Radio Astronomy Observatory in South Africa. From 1999, the experiments were expanded to also include the O’Higgins Station in Antarctica, Fortaleza in Brazil and Kokee on Hawaii. From 1999 until the end of 2003, 25 observing sessions have been reduced and analyzed using the CALC/SOLVE geodetic VLBI data reduction package. The results show that the horizontal baseline of Syowa-Hobart is increasing at the rate of 57.0±1.9 mm/year. The baseline Syowa-Hartebeesthoek is also increasing, but at the lower rate of 9.8±1.9 mm/year. The VLBI result of 2.0±3.1 mm/year and the GPS result of −1.9±0.7 mm/year for the Syowa-O’Higgins horizontal baseline support the hypothesis of one rigid Antarctic plate without intra-plate deformation, which is consistent with the NNR-NUVEL-1A global plate motion model. The location of the Euler pole of the Antarctic plate by VLBI is estimated as 59.7°S and 62.6°E with a rotation rate of 0.190 deg/Myr, while that by GPS in our study is estimated as 60.6°S and 42.2°E with a rotation rate of 0.221 deg/Myr. These pole positions are slightly different to that implied by the NNR-NUVEL-1A model of 63.0°S and 64.2°E with a rotation rate of 0.238 deg/Myr. VLBI observations over a longer time span may resolve small discrepancy of current plate motion from the NNR-NUVEL-1A model. The consistency of the VLBI coordinates with the GPS coordinates at Syowa Station, after correction for the local tie vector components between the two reference markers, is also discussed. 相似文献