scholarly journals First Geodetic Observations Using New VLBI Stations ASKAP-29 and WARK12M

2011 ◽  
Vol 28 (2) ◽  
pp. 107-116 ◽  
Author(s):  
Leonid Petrov ◽  
Chris Phillips ◽  
Tasso Tzioumis ◽  
Bruce Stansby ◽  
Cormac Reynolds ◽  
...  
Keyword(s):  
New Zealand ◽  
Very Long Baseline Interferometry ◽  
Vertical Component ◽  
Systematic Errors ◽  
Horizontal Component ◽  
Path Delay ◽  
Random Errors ◽  
Geodetic Vlbi ◽  
The North ◽  
Long Baseline

AbstractWe report the results of a successful 7-hour 1.4 GHz Very Long Baseline Interferometry (VLBI) experiment using two new stations, ASKAP-29 located in Western Australia and WARK12M located on the North Island of New Zealand. This was the first geodetic VLBI observing session with the participation of these new stations. We have determined the positions of ASKAP-29 and WARK12M. Random errors on position estimates are 150–200 mm for the vertical component and 40–50 mm for the horizontal component. Systematic errors caused by the unmodeled ionosphere path delay may reach 1.3 m for the vertical component.

scholarly journals A Tri-Band Cooled Receiver for Geodetic VLBI

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2662
Author(s):  
José A. López-Pérez ◽  
Félix Tercero-Martínez ◽  
José M. Serna-Puente ◽  
Beatriz Vaquero-Jiménez ◽  
María Patino-Esteban ◽  
...  
Keyword(s):  
Very Long Baseline Interferometry ◽  
Low Noise ◽  
Cryogenic Temperatures ◽  
Geospatial Information ◽  
Receiver Noise ◽  
Geodetic Vlbi ◽  
Long Baseline ◽  
Front End ◽  
X Band ◽  
Santa Maria

This paper shows a simultaneous tri-band (S: 2.2–2.7 GHz, X: 7.5–9 GHz and Ka: 28–33 GHz) low-noise cryogenic receiver for geodetic Very Long Baseline Interferometry (geo-VLBI) which has been developed at Yebes Observatory laboratories in Spain. A special feature is that the whole receiver front-end is fully coolable down to cryogenic temperatures to minimize receiver noise. It was installed in the first radio telescope of the Red Atlántica de Estaciones Geodinámicas y Espaciales (RAEGE) project, which is located in Yebes Observatory, in the frame of the VLBI Global Observing System (VGOS). After this, the receiver was borrowed by the Norwegian Mapping Autorithy (NMA) for the commissioning of two VGOS radiotelescopes in Svalbard (Norway). A second identical receiver was built for the Ishioka VGOS station of the Geospatial Information Authority (GSI) of Japan, and a third one for the second RAEGE VGOS station, located in Santa María (Açores Archipelago, Portugal). The average receiver noise temperatures are 21, 23, and 25 Kelvin and the measured antenna efficiencies are 70%, 75%, and 60% in S-band, X-band, and Ka-band, respectively.

scholarly journals Station correction analysis for surface-wave magnitudes of New Zealand earthquakes

1999 ◽  
Vol 32 (1) ◽  
pp. 21-29 ◽  
Author(s):  
D. A. Rhoades ◽  
D. J. Dowrick
Keyword(s):  
New Zealand ◽  
Surface Wave ◽  
Linear Model ◽  
World Wide ◽  
Vertical Component ◽  
Horizontal Component ◽  
Standard Errors ◽  
Station Correction ◽  
The Mean

Station terms and standard errors are presented for 345 world-wide stations used in the determination of surface-wave magnitudes of 190 selected New Zealand earthquakes over the period 1901-1993 [1]. These will facilitate the estimation of surface-wave magnitudes of other earthquakes in the New Zealand region. The station terms and the residuals from the linear model used to estimate them are both found to be weakly related to the mean distance from the earthquakes recorded by each station. The horizontal and vertical components at a given site are treated as separate stations. The station term for the horizontal component tends to exceed that for the vertical component at mean distances in the 20°-40° range.

scholarly journals Station Infrastructure Developments of the IVS

2020 ◽  
Author(s):  
Dirk Behrend ◽  
Axel Nothnagel ◽  
Johannes Böhm ◽  
Chet Ruszczyk ◽  
Pedro Elosegui
Keyword(s):  
Very Long Baseline Interferometry ◽  
Global Network ◽  
Radio Telescopes ◽  
Geodetic Vlbi ◽  
The Past ◽  
Long Baseline ◽  
Aging Infrastructure ◽  
Recent Developments ◽  
International Vlbi Service ◽  
Vlbi Data

<p>The International VLBI Service for Geodesy and Astrometry (IVS) is a globally operating service that coordinates and performs Very Long Baseline Interferometry (VLBI) activities through its constituent components. The VLBI activities are associated with the creation, provision, dissemination, and archiving of relevant VLBI data and products. The operational station network of the IVS currently consists of about 40 radio telescopes worldwide, subsets of which participate in regular 24-hour and 1-hour observing sessions. This legacy S/X observing network dates back in large part to the 1970s and 1980s. Because of highly demanding new scientific requirements such as sea-level change but also due to the aging infrastructure, the larger IVS community planned and started to implement a new VLBI system called VGOS (VLBI Global Observing System) at existing and new sites over the past several years. In 2020, a fledgling network of 8 VGOS stations started to observe in operational IVS sessions. We anticipate that the VGOS network will grow over the next couple of years to a global network of 25 stations and will eventually replace the legacy S/X system as the IVS production system. We will provide an overview of the recent developments and anticipated evolution of the geodetic VLBI station infrastructure.</p>

scholarly journals Experience from geodetic very long baseline interferometry observations at Onsala using a digital backend

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
N. Kareinen ◽  
R. Haas
Keyword(s):  
Very Long Baseline Interferometry ◽  
Recording System ◽  
Data Sets ◽  
Space Observatory ◽  
Geodetic Vlbi ◽  
Long Baseline ◽  
Vlbi Observations ◽  
Onsala Space Observatory ◽  
Base Band ◽  
Raw Observations

AbstractThe Onsala Space Observatory has installed a modern digital backend for geodetic and astronomical Very Long Baseline Interferometry (VLBI). This system consists of a Digital Base-Band Converter (DBBC) and a Mark 5B+ recorder. From 2011 until late 2014 this new system was run for geodetic VLBI observations in parallel with the old system consisting of a Mark 4 rack and Mark 5A recording system. Several of these observed sessions were correlated at the correlator in Bonn including both data sets. We present results from the analysis and comparison of these sessions. Both the original observed delays and corresponding geodetic parameters are compared. No significant differences are detected, for either the raw observations or for the geodetic parameters. This shows that the digital backend can be used operationally for geodetic VLBI observations.

scholarly journals Possible systematics in the VLBI catalogs as seen from Gaia

2017 ◽  
Vol 609 ◽  
pp. A19 ◽  
Author(s):  
N. Liu ◽  
Z. Zhu ◽  
J.-C. Liu
Keyword(s):  
Southern Hemisphere ◽  
Spherical Harmonics ◽  
Very Long Baseline Interferometry ◽  
Systematic Errors ◽  
Vector Spherical Harmonics ◽  
Long Baseline ◽  
Quadrupole Component ◽  
Data Release ◽  
Celestial Reference Frame ◽  
Rotation Component

Aims. In order to investigate the systematic errors in the very long baseline interferometry (VLBI) positions of extragalactic sources (quasars) and the global differences between Gaia and VLBI catalogs, we use the first data release of Gaia (Gaia DR1) quasar positions as the reference and study the positional offsets of the second realization of the International Celestial Reference Frame (ICRF2) and the Goddard VLBI solution 2016a (gsf2016a) catalogs. Methods. We select a sample of 1032 common sources among three catalogs and adopt two methods to represent the systematics: considering the differential orientation (offset) and declination bias; analyzing with the vector spherical harmonics (VSH) functions. Results. Between two VLBI catalogs and Gaia DR1, we find that: i) the estimated orientation is consistent with the alignment accuracy of Gaia DR1 to ICRF, of ~0.1 mas, but the southern and northern hemispheres show opposite orientations; ii) the declination bias in the southern hemisphere between Gaia DR1 and ICRF2 is estimated to be +152 μas, much larger than that between Gaia DR1 and gsf2016a which is +34 μas. Between two VLBI catalogs, we find that: i) the rotation component shows that ICRF2 and gsf2016a are generally consistent within 30 μas; ii) the glide component and quadrupole component report two declination-dependent offsets: dipolar deformation of ~+50 μas along the Z-axis, and quadrupolar deformation of ~−50 μas that would induce a pattern of sin2δ. Conclusions. The significant declination bias between Gaia DR1 and ICRF2 catalogs reported in previous studies is possibly attributed to the systematic errors of ICRF2 in the southern hemisphere. The global differences between ICRF2 and gsf2016a catalogs imply that possible, mainly declination-dependent systematics exit in the VLBI positions and need further investigations in the future Gaia data release and the next generation of ICRF.

scholarly journals A Tri-band Low-noise Cryogenic Receiver for Geodetic VLBI Observations with VGOS Radio Telescopes

2019 ◽  
Author(s):  
José A. López-Pérez ◽  
Félix Tercero-Martínez ◽  
José M. Serna-Puente ◽  
Beatriz Vaquero-Jiménez ◽  
María Patino-Esteban ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Very Long Baseline Interferometry ◽  
Low Noise ◽  
Radio Telescopes ◽  
Geospatial Information ◽  
Ka Band ◽  
Geodetic Vlbi ◽  
Long Baseline ◽  
Vlbi Observations ◽  
X Band

This paper shows the development of a simultaneous tri-band (S: 2.2 - 2.7 GHz, X: 7.5 - 9 GHz and Ka: 28 - 33 GHz) low-noise cryogenic receiver for geodetic Very Long Baseline Interferometry (geo-VLBI) which has been developed by the technical staff of Yebes Observatory (IGN) laboratories in Spain. The receiver was installed in the first radio telescope of the Red Atlántica de Estaciones Geodinámicas y Espaciales (RAEGE) project, which is located in Yebes Observatory, in the frame of the VLBI Global Observing System (VGOS). After this, the receiver was borrowed by the Norwegian Mapping Autorithy (NMA) for the commissioning of two VGOS radiotelescopes in Svalbard (Norway). A second identical receiver was built for the Ishioka VGOS station of the Geospatial Information Authority (GSI) of Japan, and a third one for the second RAEGE VGOS station, located in Santa María (Açores Archipelago, Portugal). The average receiver noise temperatures are 21, 23 and 25 Kelvin and the measured antenna efficiencies are 70%, 75% and 60% in S-band, X-band and Ka-band, respectively.

scholarly journals VLBI geodesy: 2 parts-per-billion precision in length determinations for transcontinental baselines

1988 ◽  
Vol 129 ◽  
pp. 367-368
Author(s):  
J. L. Davis ◽  
T. A. Herring ◽  
I. I. Shapiro
Keyword(s):  
Root Mean Square ◽  
Very Long Baseline Interferometry ◽  
Large Fraction ◽  
Baseline Length ◽  
Mean Square ◽  
Vertical Coordinate ◽  
Geodetic Vlbi ◽  
Long Baseline

We have used very-long-baseline interferometry (VLBI) to make twenty-two independent measurements, between September 1984 and December 1986, of the length of the 3900-km baseline between the Mojave site in California and the Haystack/Westford site in Massachusetts. These experiments differ from the typical geodetic VLBI experiments in that a large fraction of observations are obtained at elevation angles between 4° and 10°. Data from these low elevation angles allows the vertical coordinate of site position, and hence the baseline length, to be estimated with greater precision. For the sixteen experiments processed thus far, the weighted root-mean-square scatter of the estimates of the baseline length is 8 mm. We discuss these experiments, the processing of the data, and the resulting baseline length estimates.

Statistics and parallaxes

1978 ◽  
Vol 48 ◽  
pp. 7-29
Author(s):  
T. E. Lutz
Keyword(s):  
Experimental Design ◽  
Statistical Methods ◽  
Review Paper ◽  
Systematic Errors ◽  
Past Experience ◽  
Random Errors ◽  
Trigonometric Parallaxes ◽  
Systematic And Random Errors

This review paper deals with the use of statistical methods to evaluate systematic and random errors associated with trigonometric parallaxes. First, systematic errors which arise when using trigonometric parallaxes to calibrate luminosity systems are discussed. Next, determination of the external errors of parallax measurement are reviewed. Observatory corrections are discussed. Schilt’s point, that as the causes of these systematic differences between observatories are not known the computed corrections can not be applied appropriately, is emphasized. However, modern parallax work is sufficiently accurate that it is necessary to determine observatory corrections if full use is to be made of the potential precision of the data. To this end, it is suggested that a prior experimental design is required. Past experience has shown that accidental overlap of observing programs will not suffice to determine observatory corrections which are meaningful.

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