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 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 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 Analysis of the Residuals between Theoretical Nutations and VLBI Observations

2002 ◽  
Vol 12 ◽  
pp. 124-125 ◽  
Author(s):  
V. Dehant ◽  
M. Feissel ◽  
O. de Viron ◽  
M. Yseboodt ◽  
Ch. Bizouard
Keyword(s):  
Very Long Baseline Interferometry ◽  
Short Description ◽  
Time Intervals ◽  
Long Baseline ◽  
Vlbi Observations ◽  
Vlbi Data ◽  
Theoretical Developments

The recent theoretical developments have provided accurate series of nutations, which are close to the Very Long Baseline Interferometry (VLBI) data. At the milliarcsecond (mas) level, three series are available: MHB2000 (Mathews et al. 2000), FG2000 (Getino and Ferrándiz 2000), and SF2000 (Shirai and Fukushima 2000a,b) (see Dehant 2000, and in this volume, for more information and for a short description of these models).In the first part of our work we have compared these models with the (VLBI) observations (Ma et al. 2000) by computing rms of the residuals for several time intervals of measurements. We have concluded that these series have comparable precision.

scholarly journals VLBI studies of the nutations of the earth

1988 ◽  
Vol 129 ◽  
pp. 371-375
Author(s):  
T. A. Herring
Keyword(s):  
Truncation Error ◽  
Very Long Baseline Interferometry ◽  
Long Baseline ◽  
The Earth ◽  
Vlbi Data ◽  
One Year ◽  
Nutation Series ◽  
Theoretical Considerations ◽  
Active Investigation

The application of very–long–baseline interferometry (VLBI) to the study of the nutations of the earth has yielded unprecedented accuracy for the experimental determination of the coefficients of the nutation series. The analysis of six years of VLBI data has yielded corrections to the coefficients of the seven largest terms in the IAU 1980 nutation series with periods of one year or less, with accuracies approaching the truncation error of this nutation series (0.1 mas). The nutation series coefficients computed from the VLBI data, and those obtained from theoretical considerations (the IAU 1980 nutation series), are in excellent agreement. The largest corrections are to the coefficients of the retrograde annual nutation [2.0 ± 0.1 mas], the prograde semiannual nutation [(0.5 - ι 0.4) ±0.1 mas], and the prograde 13.7 day nutation [−0.4 ± 0.1 mas]. (The imaginary term for the semiannual nutation represents a term 90° out–of–phase with the arguments of the nutation series.) The geophysical implications of these results are currently under active investigation. We discuss the methods used to extract the nutation information from the VLBI data, the calculations of the uncertainties of the resultant corrections to the coefficients of the nutation series, and the current research into the nutations of the earth.

scholarly journals Use of the Long Baseline Array in Australia for Precise Geodesy and Absolute Astrometry

2009 ◽  
Vol 26 (1) ◽  
pp. 75-84 ◽  
Author(s):  
Leonid Petrov ◽  
Chris Phillips ◽  
Alessandra Bertarini ◽  
Adam Deller ◽  
Sergei Pogrebenko ◽  
...  
Keyword(s):  
Data Analysis ◽  
Heterogeneous Network ◽  
Radio Sources ◽  
Radio Telescopes ◽  
Geodetic Vlbi ◽  
Novel Technique ◽  
Long Baseline ◽  
Better Than

AbstractWe report the results of a successful 12-hour 22-GHz VLBI experiment using a heterogeneous network that includes radio telescopes of the Long Baseline Array (LBA) in Australia and several VLBI stations that regularly observe in geodetic VLBI campaigns. We have determined positions of three VLBI stations, atca-104, ceduna and mopra, with an accuracy of 4–30 mm using a novel technique of data analysis. These stations have never before participated in geodetic experiments. We observed 105 radio sources, and amongst them 5 objects which have not previously been observed with VLBI. We have determined positions of these new sources with the accuracy of 2–5 mas. We make the conclusion that the LBA network is capable of conducting absolute astrometry VLBI surveys with an accuracy better than 5 mas.

scholarly journals Improved VLBI scheduling through evolutionary strategies

2021 ◽  
Author(s):  
Matthias Schartner ◽  
Christian Plötz ◽  
Benedikt Soja
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Parameter Space ◽  
Very Long Baseline Interferometry ◽  
Evolutionary Strategies ◽  
Vlbi Observation ◽  
Long Baseline ◽  
International Vlbi Service ◽  
Survival Of The Fittest ◽  
Crossover And Mutation

<p>Since mid-2020, various Very Long Baseline Interferometry (VLBI) observation programs organized by the International VLBI Service for Geodesy and Astrometry (IVS) are scheduled using a new algorithm inspired by evolutionary processes based on selection, crossover and mutation. It mimics the biological concept "survival of the fittest" to iteratively explore the scheduling parameter space looking for the best solution.</p><p>In this work, we will present the general workflow of the algorithm as well as discuss its strengths and potential weaknesses. Moreover, we will highlight how the improved scheduling affects the precision of geodetic parameters. In the case of difficult-to-schedule OHG sessions, an improvement in the precision of the geodetic parameters of up to 15% could be identified based on Monte-Carlo simulations, as well as an increase in the number of observations of up to 10% compared to classical scheduling approaches.</p>

scholarly journals GNSS-based water vapor estimation and validation during the MOSAiC expedition

2021 ◽  
Author(s):  
Benjamin Männel ◽  
Florian Zus ◽  
Galina Dick ◽  
Susanne Glaser ◽  
Maximilian Semmling ◽  
...  
Keyword(s):  
Water Vapor ◽  
Very Long Baseline Interferometry ◽  
Precise Point Positioning ◽  
Radiosonde Data ◽  
Weather Data ◽  
Radio Telescopes ◽  
Long Baseline ◽  
Gnss Data ◽  
Level Of Agreement ◽  
Good Agreement

Abstract. Within the transpolar drifting expedition MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate), GNSS was used among other techniques to monitor variations in atmospheric water vapor. Based on 15 months of continuously tracked GNSS data including GPS, GLONASS, and Galileo, epoch-wise coordinates and hourly zenith total delays (ZTD) were determined using a kinematic precise point positioning (PPP) approach. The derived ZTD values agree to 1.1 ± 0.2 mm (RMS of the differences 10.2 mm) with the numerical weather data of ECMWF’s latest reanalysis, ERA5, computed for the derived ship’s locations. This level of agreement is also confirmed by comparing the on-board estimates with ZTDs derived for terrestrial GNSS stations in Bremerhaven and Ny Ålesund and for the radio telescopes observing Very Long Baseline Interferometry in Ny Ålesund. Preliminary estimates of integrated water vapor derived from frequently launched radiosondes are used to assess the GNSS-derived integrated water vapor estimates. The overall difference of 0.08 ± 0.04 kg m−2 (RMS of the differences 1.47 kg m−2) demonstrates a good agreement between GNSS and radiosonde data. Finally, the water vapor variations associated with two warm air intrusion events in April 2020 are assessed.

scholarly journals Eurasian-Pacific-N. American Plate Motions from Very Long Baseline Interferometry

1993 ◽  
Vol 156 ◽  
pp. 179-184
Author(s):  
Ailin Mao ◽  
Zhihan Qian
Keyword(s):  
North American ◽  
Very Long Baseline Interferometry ◽  
Plate Motions ◽  
The Past ◽  
Long Baseline ◽  
Made In ◽  
Relative Motions

We use the baseline variation rates, which are obtained by the VLBI measuring in the past years (1979. /-1991.1), to estimate the relative motions among Eurasian, Pacific and North American plates. A comparion with the geological-based models has been made. In order to strengthen the VLBI constraints on the Euler vectors, we estimate the velocities of unstable stations in addition to the Euler vectors.

scholarly journals Receiving And Data Acquisition Systems Of Rt-32 For Vlbi Observations / Rt-32 Uztveršanas Un Datu Reģistrācijas Sistēmas Vlbi Novērojumiem

2012 ◽  
Vol 49 (6-II) ◽  
pp. 30-42
Author(s):  
Vl. Bezrukovs ◽  
I. Shmeld ◽  
M. Nechaeva ◽  
J. Trokss ◽  
D. Bezrukovs ◽  
...  
Keyword(s):  
Data Acquisition ◽  
Radio Astronomy ◽  
Very Long Baseline Interferometry ◽  
Low Frequency ◽  
Current Status ◽  
Data Acquisition Systems ◽  
Long Baseline ◽  
Vlbi Observations ◽  
Parabolic Antenna ◽  
Vlbi Data

Abstract Radiotelescope RT-32 is a fully steerable 32-m parabolic antenna located at Irbene and belonging to Ventspils International Radio Astronomy Centre (VIRAC). Currently, the work on upgrading and repair of its receiving hardware and data acquisition systems is of high priority for the VIRAC. One of the main scientific objectives for the VIRAC Radioastronomical observatory is VLBI (very long baseline interferometry) observations in centimetre wavelengths in collaboration with world VLBI networks, such as European VLBI network (EVN), Low Frequency VLBI network (LFVN), and others. During the last years the room in the secondary focus of telescope was reconstructed, and several new receivers were installed. Currently, RT-32 observations are carried out in four different bands: 92 cm, 18 cm, 6 cm, and 2.5 cm. First three of them are already successfully employed in diversified VLBI experiments. The receiver on 2.5 cm band has only one linear polarized chain and is used mainly for the methanol maser single dish observations. The apparatus system of RT-32 is equipped with two independent VLBI data acquisition systems: TN-16, and DBBC in combination with MK5b. Both systems are employed in interferometric observations depending on the purpose of experiment and the enabled radiotelescopes. The current status of RT-32, the availability of its receiving and data acquisition units for VLBI observations and the previous VLBI sessions are discussed.

scholarly journals Recent developments in supernova research with VLBI

2013 ◽  
Vol 9 (S296) ◽  
pp. 53-57 ◽  
Author(s):  
Norbert Bartel ◽  
Michael F. Bietenholz
Keyword(s):  
Very Long Baseline Interferometry ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Expansion Velocity ◽  
Radial Density ◽  
Density Profiles ◽  
Long Baseline ◽  
Vlbi Observations ◽  
Recent Developments ◽  
Circumstellar Medium

AbstractVery long baseline interferometry (VLBI) observations during the last 30 years have resolved many supernovae and provided detailed measurements of the expansion velocity and deceleration. Such measurements are useful for estimating the radial density profiles of both the ejecta and the circumstellar medium left over from the progenitor. VLBI measurements are also the most direct way of confirming the relativistic expansion velocities thought to occur in supernovae associated with gamma-ray bursts. Well-resolved images of a few supernovae have been obtained, and the interaction of the ejecta as it expands into the circumstellar medium could be monitored in detail. We discuss recent results, for SN 1979C, SN 1986J, and SN 1993J, and note that updated movies of the latter two of the supernovae from soon after the explosion to the present are available from the first author's personal website.

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