We present the second realization of the International Celestial Reference Frame (ICRF2) at radio... more We present the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry observations. The earliest observations used are from 1979 August and the latest are from 2009 March. ICRF2 consists of accurate positions of 295 new "defining" sources and positions of 3119 additional compact radio sources to densify the frame. ICRF2 has more than 5 times as many sources as ICRF1 (Ma et al. 1997, cat. I/251), is roughly 5-6 times more accurate, and is nearly twice as stable in the orientation of its axes. (3 data files).
The construction of the second realization of the International Celestial Reference Frame by VLBI... more The construction of the second realization of the International Celestial Reference Frame by VLBI (ICRF2) was undertaken to take advantage of the many improvements in geodetic and astrometric VLBI and the vast increase in data since the first ICRF. The impact the switch to ICRF2 has had on the terrestrial reference frame and EOP solutions generated by VLBI is very small, at about the mm level, and should be transparent to most users of VLBI products.
This report summarizes the progress made in developing the next generation VLBI system, dubbed th... more This report summarizes the progress made in developing the next generation VLBI system, dubbed the VLBI2010 system. The VLBI2010 Committee of the International VLBI Service for Geodesy and Astrometry (IVS) worked on the design aspects of the new system. The report covers ...
Page 1. Design Aspects of the VLBI2010 System Progress Report of the IVS VLBI2010 Committee Bill ... more Page 1. Design Aspects of the VLBI2010 System Progress Report of the IVS VLBI2010 Committee Bill Petrachenko 1 (chair), Arthur Niell 2 , Dirk Behrend 3 , Brian Corey 2 , Johannes Böhm 4 , Patrick Charlot 5 , Arnaud Collioud 5 , John Gipson 3 , ...
Long Baseline Array and up to 10 globally distributed antennas. One of the goals of this program ... more Long Baseline Array and up to 10 globally distributed antennas. One of the goals of this program was to monitor positions of the array at a 1 millimeter level of accuracy and to tie the VLBA into the International Terrestrial Reference Frame. We describe the analysis of these data and report several interesting geophysical results including measured station displacements due to crustal motion, earthquakes, and antenna tilt. In terms of both formal errors and observed scatter, these sessions are among the very best geodetic VLBI experiments.
We report the results of new VLBI SOLVE data analysis options. These are: 1) modeling antenna the... more We report the results of new VLBI SOLVE data analysis options. These are: 1) modeling antenna thermal deformation, 2) elevation-dependent weighting, 3) VMF1, 4) in- troducing correlation between observations, 5) use of slant path tropospheric delays from nu- merical weather models.
From October 2003 to September 2005, the International VLBI Service for Geodesy and Astrometry (I... more From October 2003 to September 2005, the International VLBI Service for Geodesy and Astrometry (IVS) examined current and future requirements for geodetic VLBI, including all components from antennas to analysis. IVS Working Group 3 ‘VLBI 2010’, which was tasked with this effort, concluded with recommendations for a new generation of VLBI systems. These recommendations were based on the goals of achieving 1 mm measurement accuracy on global baselines, performing continuous measurements for time series of station positions and Earth orientation parameters, and reaching a turnaround time from measurement to initial geodetic results of less than 24 hours. To realize these recommendations and goals, along with the need for low cost of construction and operation, requires a complete examination of all aspects of geodetic VLBI including equipment, processes, and observational strategies. Hence, in October 2005, the IVS VLBI2010 Committee (V2C) commenced work on defining the VLBI2010 syste...
A generalized no-fiducial approach has been developed to obtain global positions and velocities w... more A generalized no-fiducial approach has been developed to obtain global positions and velocities without fixing any individual position or velocity components. The method used can be applied to any global geodetic technique and proceeds in three general steps. First, daily solutions derived with weak constraints are combined to yield one global set of positions and velocities. Second, 14 minimal constraints are applied to remove uncertainties due to the loosely defined reference frame. Third, transformation from one reference frame to another is accomplished with a 14 parameter transformation. One year of daily FLINN solutions, each made with data from about 40 sites, have been combined to yield our best fit global model...
ABSTRACT An employment of microwave antenna holography makes it possible to plot contour maps of ... more ABSTRACT An employment of microwave antenna holography makes it possible to plot contour maps of parabolic dish antenna surfaces quickly and easily. This approach can be utilized to check the surface quality and alignment of the antenna panels and to conduct a search for focusing errors. The considered technique has a number of advantages over laser-ranging, near-field electromagnetic, and mechanical measurement techniques. The advantages are related to an improvement of measurement resolution, the reduced costs of the required measurements, and the possibility to interrupt the measurement process at any time in response to normal operational requirements. Attention is given to holographic phase plots, the test procedure, software functions, the scanning method, signal processing, and the digitization of channels.
We present the second realization of the International Celestial Reference Frame (ICRF2) at radio... more We present the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry observations. The earliest observations used are from 1979 August and the latest are from 2009 March. ICRF2 consists of accurate positions of 295 new "defining" sources and positions of 3119 additional compact radio sources to densify the frame. ICRF2 has more than 5 times as many sources as ICRF1 (Ma et al. 1997, cat. I/251), is roughly 5-6 times more accurate, and is nearly twice as stable in the orientation of its axes. (3 data files).
The construction of the second realization of the International Celestial Reference Frame by VLBI... more The construction of the second realization of the International Celestial Reference Frame by VLBI (ICRF2) was undertaken to take advantage of the many improvements in geodetic and astrometric VLBI and the vast increase in data since the first ICRF. The impact the switch to ICRF2 has had on the terrestrial reference frame and EOP solutions generated by VLBI is very small, at about the mm level, and should be transparent to most users of VLBI products.
This report summarizes the progress made in developing the next generation VLBI system, dubbed th... more This report summarizes the progress made in developing the next generation VLBI system, dubbed the VLBI2010 system. The VLBI2010 Committee of the International VLBI Service for Geodesy and Astrometry (IVS) worked on the design aspects of the new system. The report covers ...
Page 1. Design Aspects of the VLBI2010 System Progress Report of the IVS VLBI2010 Committee Bill ... more Page 1. Design Aspects of the VLBI2010 System Progress Report of the IVS VLBI2010 Committee Bill Petrachenko 1 (chair), Arthur Niell 2 , Dirk Behrend 3 , Brian Corey 2 , Johannes Böhm 4 , Patrick Charlot 5 , Arnaud Collioud 5 , John Gipson 3 , ...
Long Baseline Array and up to 10 globally distributed antennas. One of the goals of this program ... more Long Baseline Array and up to 10 globally distributed antennas. One of the goals of this program was to monitor positions of the array at a 1 millimeter level of accuracy and to tie the VLBA into the International Terrestrial Reference Frame. We describe the analysis of these data and report several interesting geophysical results including measured station displacements due to crustal motion, earthquakes, and antenna tilt. In terms of both formal errors and observed scatter, these sessions are among the very best geodetic VLBI experiments.
We report the results of new VLBI SOLVE data analysis options. These are: 1) modeling antenna the... more We report the results of new VLBI SOLVE data analysis options. These are: 1) modeling antenna thermal deformation, 2) elevation-dependent weighting, 3) VMF1, 4) in- troducing correlation between observations, 5) use of slant path tropospheric delays from nu- merical weather models.
From October 2003 to September 2005, the International VLBI Service for Geodesy and Astrometry (I... more From October 2003 to September 2005, the International VLBI Service for Geodesy and Astrometry (IVS) examined current and future requirements for geodetic VLBI, including all components from antennas to analysis. IVS Working Group 3 ‘VLBI 2010’, which was tasked with this effort, concluded with recommendations for a new generation of VLBI systems. These recommendations were based on the goals of achieving 1 mm measurement accuracy on global baselines, performing continuous measurements for time series of station positions and Earth orientation parameters, and reaching a turnaround time from measurement to initial geodetic results of less than 24 hours. To realize these recommendations and goals, along with the need for low cost of construction and operation, requires a complete examination of all aspects of geodetic VLBI including equipment, processes, and observational strategies. Hence, in October 2005, the IVS VLBI2010 Committee (V2C) commenced work on defining the VLBI2010 syste...
A generalized no-fiducial approach has been developed to obtain global positions and velocities w... more A generalized no-fiducial approach has been developed to obtain global positions and velocities without fixing any individual position or velocity components. The method used can be applied to any global geodetic technique and proceeds in three general steps. First, daily solutions derived with weak constraints are combined to yield one global set of positions and velocities. Second, 14 minimal constraints are applied to remove uncertainties due to the loosely defined reference frame. Third, transformation from one reference frame to another is accomplished with a 14 parameter transformation. One year of daily FLINN solutions, each made with data from about 40 sites, have been combined to yield our best fit global model...
ABSTRACT An employment of microwave antenna holography makes it possible to plot contour maps of ... more ABSTRACT An employment of microwave antenna holography makes it possible to plot contour maps of parabolic dish antenna surfaces quickly and easily. This approach can be utilized to check the surface quality and alignment of the antenna panels and to conduct a search for focusing errors. The considered technique has a number of advantages over laser-ranging, near-field electromagnetic, and mechanical measurement techniques. The advantages are related to an improvement of measurement resolution, the reduced costs of the required measurements, and the possibility to interrupt the measurement process at any time in response to normal operational requirements. Attention is given to holographic phase plots, the test procedure, software functions, the scanning method, signal processing, and the digitization of channels.
Uploads
Papers by J. Gipson