| 1. |
- Albentosa, Ezequiel, et al.
(author)
-
Current Status of the EU-VGOS Project
- 2023
-
In: International VLBI Service for Geodesy and Astrometry 2022 General Meeting Proceedings. ; NASA/ CP–20220018789, s. 85-89
-
Conference paper (peer-reviewed)abstract
- The EU-VGOS project began in 2018 with the aim of using the VGOS infrastructure in Europe to investigate methods for VGOS data processing. The project is now structured into Working Groups dealing with operations (stations), e-transfer, correlation and post-processing, and analysis. This is a report on the status of the project.
|
|
| 2. |
- Alef, Walter, et al.
(author)
-
Geodetic data analysis of VGOS experiments
- 2021
-
In: 2021 34th General Assembly and Scientific Symposium of the International Union of Radio Science, URSI GASS 2021.
-
Conference paper (peer-reviewed)abstract
- Very Long Baseline Interferometry (VLBI) serves as one of the common geodetic methods to define the global reference frames and monitor Earth's orientation variations. The technical upgrade of the VLBI method known as the VLBI Global Observing System (VGOS) includes a critical re-design of the observed frequencies from the dual band mode (S and X band, i.e. 2 GHz and 8 GHz) to observations in a broadband (2-14 GHz). Since 2019 the first VGOS experiments are available for the geodetic analysis in free access at the International VLBI service for Geodesy and Astrometry (IVS). Also regional-only subnetworks such as European VLBI stations have succeeded already in VGOS mode. Based on these brand-new observations we review the current geodetic data analysis workflow to build a bridge between geodetic observed delays derived from different bands.
|
|
| 3. |
- Alef, Walter, et al.
(author)
-
The EUropean-VGOS Project
- 2019
-
In: Proceedings of the 24th European VLBI Group for Geodesy and Astrometry Working Meeting. - 9788441656345 ; , s. 107-111
-
Conference paper (peer-reviewed)abstract
- In Spring 2018 the Bonn correlation centre started a collaboration with the three European stations of Wettzell, Onsala and Yebes, equipped with both S/X- and broadband systems, to perform VGOS-like test sessions. The aim is to verify and develop further the processing chain for VGOS experiments end-to-end, from the scheduling to the analysis of the derived observables. We will present the current status of the project.
|
|
| 4. |
- Asgarimehr, Milad, et al.
(author)
-
Remote Sensing of Precipitation Using Reflected GNSS Signals: Response Analysis of Polarimetric Observations
- 2022
-
In: IEEE Transactions on Geoscience and Remote Sensing. - 0196-2892 .- 1558-0644. ; 60
-
Journal article (peer-reviewed)abstract
- For the first time, rain effects on the polarimetric observations of the global navigation satellite system reflectometry (GNSS-R) are investigated. The physical feasibility of tracking the modifications in the surface roughness by rain splash and the surface salinity by the accumulation of freshwater is theoretically discussed. An empirical analysis is carried out using measurements of a coastal GNSS-R station with two side-looking antennas in right- and left-handed circular polarizations (RHCP and LHCP). Discernible drops in RHCP and LHCP powers are observed during rain over a calm sea. The power drop becomes larger at higher elevation angles. The average LHCP power drops by ≈ 5 dB at an elevation angle of 45°. The amplitude of the correlation sum shows a dampening, responding to rain rate systematically. The LHCP observations show higher sensitivity to rainfall compared to RHCP observations. The retrieved standard deviation of surface heights shows a steady increase with the rain rate. The derived surface salinity shows a decrease at rains higher than 10 mm/h. This study confirms the potential under environmental conditions of the GNSS-R ground-based station, e.g., with salinity mostly lower than 30 psu, over a calm sea, being a starting point for future investigations.
|
|
| 5. |
|
|
| 6. |
- Behrend, Dirk, et al.
(author)
-
Recent Progress in the VLBI2010 Development
- 2008
-
In: in Proceedings of the 2007 IAG General Assembly, Perugia, Italy, July 2-13, 2007, ed. M. Sideris, Springer. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0939-9585. - 9783540854258 ; 133:Part 5, s. 833-840
-
Conference paper (peer-reviewed)abstract
- 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 1mm 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 h. 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 system specifications. In this paper we give a summary of the recent progress of the VLBI2010 project. © Springer-Verlag Berlin Heidelberg 2009.
|
|
| 7. |
- Behrend, Dirk, et al.
(author)
-
Reports of IERS Components: International VLBI Service (IVS)
- 2011
-
In: IERS Annual Report 2008-09. Edited by Wolfgang R. Dick and Bernd Richter. International Earth Rotation and Reference Systems Service, Central Bureau. Frankfurt am Main: Verlag des Bundesamts für Kartographie und Geodäsie, 2011. 237 p.. - 1029-0060. ; , s. 72-82
-
Journal article (other academic/artistic)
|
|
| 8. |
|
|
| 9. |
- Bergstrand, Sten, et al.
(author)
-
A gravitational telescope deformation model for geodetic VLBI
- 2019
-
In: Journal of Geodesy. - : Springer Science and Business Media LLC. - 0949-7714 .- 1432-1394. ; 93:5, s. 669-680
-
Journal article (peer-reviewed)abstract
- We have measured the geometric deformations of the Onsala 20 m VLBI telescope utilizing a combination of laser scanner, laser tracker, and electronic distance meters. The data put geometric constraints on the electromagnetic raypath variations inside the telescope. The results show that the propagated distance of the electromagnetic signal inside the telescope differs from the telescope’s focal length variation, and that the deformations alias as a vertical or tropospheric component. We find that for geodetic purposes, structural deformations of the telescope are more important than optic properties, and that for geodetic modelling the variations in raypath centroid rather than focal length should be used. All variations that have been identified as significant in previous studies can be quantified. We derived coefficients to model the gravitational deformation effect on the path length and provide uncertainty intervals for this model. The path length variation due to gravitational deformation of the Onsala 20 m telescope is in the range of 7–11 mm, comparing elevation 0$$^{\circ }$$∘and 90$$^{\circ }$$∘, and can be modelled with an uncertainty of 0.3 mm.
|
|
| 10. |
|
|
