| 1. |
- Elgered, Gunnar, 1955, et al.
(författare)
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The Onsala Tide Gauge Station: Experiences from the first four years of operation
- 2019
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Ingår i: Proceedings of the 24th European VLBI Group for Geodesy and Astrometry Working Meeting. ; , s. 75-79
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Konferensbidrag (refereegranskat)abstract
- A tide gauge station was installed at the Onsala Space Observatory in 2015. The official tide gauge station includes several independent senors: one radar and three pneumatic sensors (also referred to as bubblers). The radar and two bubblers are mounted in a well and one bubbler outside the well. Additional sensors such as one laser sensor and three radar sensors have been used during dierent time periods in order to further assess the quality of the acquired sea level data. Here we compare the four ocial sensors and the laser sensor which was installed in April 2016. The expected accuracy (one standard deviation) for all of these sensors is approximately 3 mm, according to the datasheet specifications. Results from the first four years of operations are used to assess and estimate the actual accuracies by means of comparisons between the sensors. We observe typical biases over time scales of months of up to 10 mm. Biases are caused by uncertainties of the reference level of the sensor, the density of the water for the bubblers, multipath eects for the radar, and nonlinearities with temperature for the laser. The observed monthly standard deviation between the sensors in the well vary between 2 mm and 6 mm, which is roughly consistent with the data sheet specifications.
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| 2. |
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| 3. |
- Haas, Rüdiger, 1966, et al.
(författare)
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Status of the Onsala Twin Telescopes – Two Years After the Inauguration
- 2019
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Ingår i: Proceedings of the 24th European VLBI Group for Geodesy and Astrometry Working Meeting. - 9788441656345 ; , s. 5-9
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Konferensbidrag (refereegranskat)abstract
- We give a brief overview on the status of the Onsala twin telescopes (OTT), two years after their inauguration. The dierent components of the VGOS systems are briefly described, and the development towards routine operations.
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| 4. |
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| 5. |
- Alef, Walter, et al.
(författare)
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The EUropean-VGOS Project
- 2019
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Ingår i: Proceedings of the 24th European VLBI Group for Geodesy and Astrometry Working Meeting. - 9788441656345 ; , s. 107-111
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Konferensbidrag (refereegranskat)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.
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| 6. |
- Bergstrand, Sten, et al.
(författare)
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A gravitational telescope deformation model for geodetic VLBI
- 2019
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Ingår i: Journal of Geodesy. - : Springer Science and Business Media LLC. - 0949-7714 .- 1432-1394. ; 93:5, s. 669-680
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Tidskriftsartikel (refereegranskat)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.
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| 7. |
- Bergstrand, Sten, 1971, et al.
(författare)
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Geometric Variations of a Geodetic Radio Telescope
- 2017
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Ingår i: Proceedings of the 23rd European VLBI Group for Geodesy and Astrometry Working Meeting. - 9789188041104 ; , s. 61-64
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 8. |
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| 9. |
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| 10. |
- Corbin, Armin, 1993, et al.
(författare)
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Scheduling of Twin Telescopes and the Impact on Troposphere and UT1 Estimation
- 2019
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Ingår i: Proceedings of the 24th European VLBI Group for Geodesy and Astrometry Working Meeting. ; , s. 194-198
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Konferensbidrag (refereegranskat)abstract
- Recently, several VGOS twin telescopes in Europe were completed.We examine the use of VGOS twin telescopes by a new scheduling approach. This approach is based on integer linear programming and creates uniform distributed observations over time. Several VLBI intensive sessions are rescheduled involving the VGOS twin telescopes and the impact on the troposphere and UT1 estimation is investigated.
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