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| 2. |
- Klopotek, Grzegorz, 1990, et al.
(författare)
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Results from the VLBI Analysis Software Comparison Campaign 2015
- 2016
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Ingår i: IVS 2016 General Meeting Proceedings "New Horizons with VGOS". Edited by Dirk Behrend, Karen D. Baver, and Kyla L. Armstrong, NASA/CP-2016-219016. ; , s. 203-207
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the VLBI Analysis Software Comparison Campaign 2015 (VASCC2015) was to compare differentVLBI analysis software packages on the basis of computed theoretical delays. Eleven research groups and institutes participated in this project which allowed us to compare software packages that are used in operational VLBI analyses or that are still under development. We present the first results and we show how well the individual software packages agree at this stage.
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| 3. |
- Elgered, Gunnar, 1955, et al.
(författare)
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The Onsala Twin Telescopes Project
- 2017
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Ingår i: The 23rd Working Meeting of the European VLBI Group for Geodesy and Astrometry (EVGA), Gothenburg, May 14–18, 2017.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Onsala Space Observatory is the European site in the International VLBI Service for Geodesy and Astrometry (IVS) that has the longest history in VLBI. First geodetic VLBI measurements were performed already in 1968 with the 25 m radio telescope. Onsala is today one of the sites with thelongest time series in the IVS data base. The observatory is one of the unique fundamental space geodetic sites that have a direct access to the coast line and co-locate VLBI, GNSS, gravimetry, and sea-level monitoring. Onsala is thus an important co-location site for the GlobalGeodetic Observing System (GGOS). Being well aware of the VGOS standard it was clear around 2010 that Onsala was in need for a telescope with significantly faster slew rates than the existing radome-enclosed 20 m telescope.
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| 4. |
- Elgered, Gunnar, 1955, et al.
(författare)
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The Onsala Twin Telescopes: the Status at the Time for the Inauguration
- 2017
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Ingår i: Proceedings of the 23rd European VLBI Group for Geodesy and Astrometry Working Meeting. - 9789188041098 ; , s. 136-139
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We summarise the activities related to the Onsala Twin Telescopes (OTT), from the time when the decision was taken to fund the proposal, to the inauguration on 18 May 2017.
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| 5. |
- Geremia-Nievinski, F., et al.
(författare)
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SNR-based GNSS reflectometry for coastal sea-level altimetry: results from the first IAG inter-comparison campaign
- 2020
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Ingår i: Journal of Geodesy. - : Springer Science and Business Media LLC. - 0949-7714 .- 1432-1394. ; 94:8
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Tidskriftsartikel (refereegranskat)abstract
- Ground-based Global Navigation Satellite System Reflectometry (GNSS-R) is quickly maturing toward the objective of becoming a viable alternative for operational coastal sea-level (SL) altimetry in a geocentric reference frame. SL has immense societal implications related to climate change. Of particular interest is the exploitation of existing coastal GNSS sites for reflectometry by means of signal-to-noise ratio (SNR) observables. We report results from the first inter-comparison campaign on SNR-based GNSS-R. The goal was to cross-validate retrieval solutions from independent research groups under comparable conditions. This action was an initiative of the International Association of Geodesy working group 4.3.9 (2015–2019 term). Data collected at the Onsala Space Observatory for a 1-year period (2015–2016) were compared to a co-located tide gauge (TG). SNR data for the GPS L1-C/A signal were processed by four groups, in Sweden, Luxembourg/Brazil, Germany, and the UK. Semidiurnal tidal constituents showed good agreement between TG and all GNSS-R groups. SL variations at diurnal and longer periods were also well captured by all series. Most GNSS-R solutions exhibited spurious tones at integer fractions of one sidereal day, the satellite revisit time of the particular GNSS constellation employed (GPS). Band-pass filtering between 3 h and 30 h confirmed that the dominant tidal components were well captured by most GNSS-R solutions. Higher-frequency SL variations (periods < 3 h) are poorly represented by GNSS-R as a consequence of its low temporal resolution. The solution with the worst agreement neglects a correction associated with the rate of change in sea level and uses narrower satellite elevation ranges per retrieval. Overall, there was excellent agreement, with correlation coefficients exceeding 0.9 and RMSE smaller than 5 cm.
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| 6. |
- Haas, Rüdiger, 1966, et al.
(författare)
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Contributions of Onsala Space Observatory to GGOS
- 2015
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Ingår i: Proceedings of the 22nd European VLBI Group for Geodesy and Astrometry Working Meeting. - 9789892061917 ; , s. 125-129
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Haas, Rüdiger, 1966, et al.
(författare)
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GLONASS-VLBI: Onsala-Wettzell test observations
- 2015
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Ingår i: Proceedings of the 22nd European VLBI Group for Geodesy and Astrometry Working Meeting. - 9789892061917 ; , s. 107-111
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Haas, Rüdiger, 1966, et al.
(författare)
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Near real-time monitoring of UT1 with geodetic VLBI
- 2011
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Ingår i: Proceedings of the 20th Meeting of the European VLBI Group for Geodesy and Astrometry. - 1864-1113. ; , s. 64-66
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We give a short overview on the current status of near real-time monitoring of UT1 with geodetic VLBI. The use ofreal-time data transfer together with automated correlation and data analysis makes it possible to derive final dUT1-results with very low latency. The agreement with IERS C04 results is on the level of 30 msec. It is even possible to determine time series of dUT1 during ongoing 24 h IVS-sessions. The concept is highly relevant for future VLBI2010 operations.
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| 9. |
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| 10. |
- Haas, Rüdiger, 1966, et al.
(författare)
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Onsala Space Observatory – IVS Network Station Activities during 2014
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We participated in 39 IVS sessions, includ-ing CONT14. Eleven out of the initially planned ses-sions could not be observed due to the installation ofa new radome for the 20-m radio telescope. As in theprevious six years, we used several of the sessions thatinvolved both Onsala and Tsukuba to perform ultra-rapid UT1-UTC sessions together with our colleaguesin Tsukuba. This included the complete CONT14 cam-paign where near real-time UT1-UTC on the baselineOnsala—Tsukuba could be determined. The procure-ment of the telescopes for the Onsala Twin Telescopeswas started in the summer of 2014. The contract to buytwo VGOS radio telescopes was signed at the end of the year.
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