Short Baseline Observations at Geodetic Observatory Wettzell

The Geodetic Observatory Wettzell (GOW), jointly operated by the Federal Agency for Cartography and Geodesy (BKG), Germany and the Technical University of Munich, Germany is equipped with three radio telescopes for Very Long Baseline Interferometry (VLBI). Correlation capability is primarily designed for relative positioning of the three Wettzell radio telescopes i.e., to derive the local ties between the three telescopes from VLBI raw data in addition to the conventional terrestrial surveys. A computing cluster forming the GO Wettzell Local Correlator (GOWL) was installed in 2017 as well as the Distributed FX (DiFX) software correlation package and the Haystack Observatory Postprocessing System (HOPS) for fringe fitting and postprocessing of the output. Data pre-processing includes ambiguity resolution (if necessary) as well as the generation of the geodetic database and NGS card files with υ Solve. The final analysis is either carried out with local processing software (LEVIKA short baseline analysis) or with the Vienna VLBI and Satellite (VieVS) software. We will present an overview of the scheduling, correlation and analysis capabilities at GOW and results obtained so. The dataset includes auxiliary files (schedule and log files) which contain information about the participating antenna, observed sources, clock offset between formatter and GPS time, cable delay, meteorological parameters (temperature, barometric pressure, and relative humidity) and ASCII files created after fringe fitting and final analysis. The published dataset can be used by the researchers and scientists to further explore short baseline interferometry.

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Short-baseline interferometry local-tie experiments at the Onsala Space Observatory

Journal of Geodesy ◽

10.1007/s00190-021-01509-5 ◽

2021 ◽

Vol 95 (5) ◽

Author(s):

Eskil Varenius ◽

Rüdiger Haas ◽

Tobias Nilsson

Keyword(s):

Very Long Baseline Interferometry ◽

A Priori ◽

Radio Telescopes ◽

Space Observatory ◽

Short Baseline ◽

Long Baseline ◽

Onsala Space Observatory ◽

X Band ◽

Group Delays ◽

Local Tie

AbstractWe present results from observation, correlation and analysis of interferometric measurements between the three geodetic very long baseline interferometry (VLBI) stations at the Onsala Space Observatory. In total, 25 sessions were observed in 2019 and 2020, most of them 24 h long, all using X band only. These involved the legacy VLBI station ONSALA60 and the Onsala twin telescopes, ONSA13NE and ONSA13SW, two broadband stations for the next-generation geodetic VLBI global observing system (VGOS). We used two analysis packages: $$\nu $$ ν Solve to pre-process the data and solve ambiguities, and ASCOT to solve for station positions, including modelling gravitational deformation of the radio telescopes and other significant effects. We obtained weighted root mean square post-fit residuals for each session on the order of 10–15 ps using group-delays and 2–5 ps using phase-delays. The best performance was achieved on the (rather short) baseline between the VGOS stations. As the main result of this work, we determined the coordinates of the Onsala twin telescopes in VTRF2020b with sub-millimetre precision. This new set of coordinates should be used from now on for scheduling, correlation, as a priori for data analyses, and for comparison with classical local-tie techniques. Finally, we find that positions estimated from phase-delays are offset $$\sim +3$$ ∼ + 3 mm in the up-component with respect to group-delays. Additional modelling of (elevation dependent) effects may contribute to the future understanding of this offset.

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Orbit Determination of Geostationary Earth Orbit Satellite by Transfer with Differenced Ranges between Slave-Slave Stations

Journal of Navigation ◽

10.1017/s0373463313000581 ◽

2013 ◽

Vol 67 (1) ◽

pp. 163-175 ◽

Cited By ~ 3

Author(s):

Cao Fen ◽

Yang XuHai ◽

Su MuDan ◽

Li ZhiGang ◽

Feng ChuGang ◽

...

Keyword(s):

Orbit Determination ◽

Very Long Baseline Interferometry ◽

Baseline Length ◽

Positioning System ◽

Orbit Error ◽

Long Baseline ◽

Data Volume ◽

Clock Offset ◽

Range Observation

In order to more restrict the transverse orbit error, a new method named “differenced ranges between slave stations by transfer”, similar to Very Long Baseline Interferometry (VLBI) observation, has been developed in the Chinese Area Positioning System (CAPS). This method has the number of baselines added, the baseline length increased and the data volume enlarged. In this article, the principle of “differenced ranges between slave stations by transfer” has been described in detail, with the clock offset between slave stations and system error which affects the precision of the differenced ranges observation being discussed. Using this method, the differenced observation of the SINOSAT-1 satellite with C-band between slave stations from 6 to 13 June 2005 was conducted. Then a comparison was made between the accuracy of orbit determination and orbit prediction. A conclusion can be drawn that the combination of pseudo-range receiving the own-station-disseminated signal and the differenced range observation between slave-slave stations has a higher orbit determination and prediction accuracy than using only the former.

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Station Infrastructure Developments of the IVS

10.5194/egusphere-egu2020-12847 ◽

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>

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

10.5194/amt-2021-79 ◽

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.

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Stability monitoring of a stationary VLBI antenna

Canadian Journal of Earth Sciences ◽

10.1139/e83-148 ◽

1983 ◽

Vol 20 (10) ◽

pp. 1586-1597 ◽

Cited By ~ 1

Author(s):

W. F. Teskey ◽

W. Niemeier ◽

M. Sideris ◽

R. G. Lyall

Keyword(s):

Very Long Baseline Interferometry ◽

Monitoring Network ◽

Numerical Results ◽

Sensitivity Analyses ◽

Radio Telescopes ◽

Monitoring Networks ◽

Tectonic Plates ◽

Stability Monitoring ◽

Mathematical Background ◽

Long Baseline

The proposed Canadian Long Baseline Array (CLBA) and the use of several radio telescopes in the CLBA as very long baseline interferometry (VLBI) stations to determine possible movements of tectonic plates are briefly described. The need for a monitoring network surrounding each VLBI antenna is explained, and expected movement between two possible VLBI stations is estimated. The mathematical background of precision, reliability, and sensitivity analyses is outlined. These analyses are then applied to an actual monitoring network. The numerical results are discussed to show how these analyses are particularly useful for monitoring networks.

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Orbiting VLBI: A Survey

Symposium - International Astronomical Union ◽

10.1017/s0074180900078554 ◽

1984 ◽

Vol 110 ◽

pp. 397-403

Author(s):

Bernard F. Burke

Keyword(s):

Very Long Baseline Interferometry ◽

Dynamic Range ◽

High Dynamic Range ◽

Limiting Factor ◽

Space Vehicles ◽

Radio Telescopes ◽

Long Baseline ◽

The Earth ◽

Effective Aperture ◽

High Dynamic

The Very-Long-Baseline Interferometry technique is not limited by the size of the Earth. Near-Earth-orbiting space vehicles can carry radio telescopes that can serve as VLBI stations using existing technology. By proper use of ground VLB arrays, a single orbiting VLBI satellite can yield radio maps with 2-dimensional coverage and high dynamic range at all declinations. A single orbiter can be used out to orbits that yield an effective aperture greater than two Earth diameters. Interstellar scintillations are a limiting factor only in the micro-arc-second range.

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The VSOP project: Space VLBI Imaging of AGN at 1.6 and 5 GHz

Symposium - International Astronomical Union ◽

10.1017/s0074180900220664 ◽

2001 ◽

Vol 205 ◽

pp. 118-121

Author(s):

Y. Murata ◽

H. Hirabayashi ◽

P.G. Edwards

Keyword(s):

Active Galactic Nuclei ◽

Very Long Baseline Interferometry ◽

Galactic Nuclei ◽

Radio Telescopes ◽

Space Observatory ◽

Long Baseline ◽

5 Ghz

The VLBI Space Observatory Programme (VSOP) combines an orbiting radiotelescope with arrays of ground radio telescopes to extend the Very Long Baseline Interferometry (VLBI) technique to baselines up to almost three Earth diameters. In this paper, we present results from VSOP observations of active galactic nuclei (AGN) at 1.6 and 5 GHz from the first 3.5 years of the mission.

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Star Scheduling Mode—A New Observing Strategy for Monitoring Weak Southern Radio Sources with the AuScope VLBI Array

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2017.58 ◽

2017 ◽

Vol 34 ◽

Cited By ~ 2

Author(s):

Lucia McCallum ◽

David Mayer ◽

Karine Le Bail ◽

Matthias Schartner ◽

Jamie McCallum ◽

...

Keyword(s):

Very Long Baseline Interferometry ◽

Integration Time ◽

Radio Sources ◽

Radio Telescopes ◽

The South ◽

Baseline Sensitivity ◽

Long Baseline ◽

Australian Continent ◽

Celestial Reference Frame ◽

Short Integration Time

AbstractThe International Celestial Reference Frame suffers from significantly less observations in the southern hemisphere compared to the northern one. One reason for this is the historically low number of very long baseline interferometry radio telescopes in the south. The AuScope very long baseline interferometry array with three new telescopes on the Australian continent and an identical antenna in New Zealand were built to address this issue. While the overall number of observations in the south has greatly improved since then, a closer look reveals that this improvement is only true for strong radio sources (source flux densities >0.6 Jy). The new array of small very long baseline interferometry antennas has a relatively low baseline sensitivity so that only strong sources can be observed within a short integration time. A new observing strategy, the star scheduling mode, was developed to enable efficient observations of weak sources during geodetic sessions, through the addition of a single more sensitive antenna to the network. This scheduling mode was implemented in the Vienna very long baseline interferometry Software and applied in four 24-h sessions in 2016. These observations provide updated positions and source flux densities for 42 weak southern radio sources and significantly reduce the formal uncertainties for these sources. The star scheduling mode now allows the AuScope very long baseline interferometry array to undertake greater responsibility in monitoring sources in the southern sky, without significantly weakening the session for geodetic purposes.

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

10.20944/preprints201912.0408.v1 ◽

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.

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Influence of Adopted Nutation Model on VLBI NEOS-Intensives Analysis

International Astronomical Union Colloquium ◽

10.1017/s0252921100000385 ◽

2000 ◽

Vol 180 ◽

pp. 259-262 ◽

Cited By ~ 3

Author(s):

Oleg Titov

Keyword(s):

Very Long Baseline Interferometry ◽

Parametric Model ◽

Universal Time ◽

Reference Station ◽

Earth’S Rotation ◽

Clock Rate ◽

Long Baseline ◽

Vlbi Data ◽

Intensive Program ◽

Clock Offset

Very Long Baseline Interferometry (VLBI) provides information about the Earth’s rotation. Various observational programs have operated for different specific purposes since 1983. The purpose of the NEOS-Intensive program is to make observations of Universal Time (UT1–UTC). Short observational sessions (1-2 hours) include only the transcontinental baseline (Wettzell - NRAO20). 20–30 individual scans are performed during the observational time. Only five parameters, wet delay for the reference station, wet delay for the second station, clock offset for the second station, clock rate for the second station, and UT1–UTC are considered in the parametric model.The purpose of this paper is to investigate the influence of the adopted nutation model on the UT1–UTC estimates. VLBI data from the NEOS-Intensives have been analyzed using the OCCAM 3.4 software. All reduction calculations are in accordance with the IERS Conventions 1996 (McCarthy, 1996).

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