| 1. |
- Calves, G. M., et al.
(författare)
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Observations and analysis of phase scintillation of spacecraft signal on the interplanetary plasma
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 564
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Tidskriftsartikel (refereegranskat)abstract
- Aims. The phase scintillation of the European Space Agency's Venus Express (VEX) spacecraft telemetry signal was observed at X-band (lambda = 3.6 cm) with a number of radio telescopes of the European Very Long Baseline Interferometry (VLBI) Network in the period 2009-2013. Methods. We found a phase fluctuation spectrum along the Venus orbit with a nearly constant spectral index of -2.42 +/- 0.25 over the full range of solar elongation angles from 0 degrees to 45 degrees, which is consistent with Kolmogorov turbulence. Radio astronomical observations of spacecraft signals within the solar system give a unique opportunity to study the temporal behaviour of the signal's phase fluctuations caused by its propagation through the interplanetary plasma and the Earth's ionosphere. This gives complementary data to the classical interplanetary scintillation (IPS) study based on observations of the flux variability of distant natural radio sources. Results. We present here our technique and the results on IPS. We compare these with the total electron content for the line of sight through the solar wind. Finally, we evaluate the applicability of the presented technique to phase-referencing VLBI and Doppler observations of currently operational and prospective space missions.
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| 4. |
- Kodet, Jan, et al.
(författare)
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Co-location of space geodetics techniques in Space and on the ground
- 2013
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Ingår i: Reports of the Finnish Geodetic Institute, Proceedings of the 21st Meeting of the European VLBI Group for Geodesy and Astronomy, Ed. by N. Zubko and M. Poutanen. - 0355-1962. - 9789517112970 ; 2013:1:1, s. 223-226
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The most demanding goal of the GlobalGeodetic Observing System (GGOS) initiative is thedefinition of station positions to an accuracy of 1 mmand the corresponding velocities to 0.1 mm/year. Fundamentalstations are core sites in this respect, becausethey collocate the geodetic relevant space techniques.However this requires unprecedented control over localties, intra- and inter-technique biases. To improvethe accuracy of the geodetic techniques, new conceptsfor the monitoring and controlling of local ties and biaseshave to be implemented.We are developing a symmetrictwo-way measurement technique to identify unaccountedsystem delays within and between the instrumentationof the Geodetic Observatory Wettzell. Itrequires redesign of the VLBI (Very Long Baseline Interferometry)phase calibration generator to be compatiblewith such an two-way measurement technique andVLBI2010. Another activity is the mapping of GlobalNavigation Satellite System (GNSS) satellites into theframe of the quasars using VLBI telescope, in geodeticmode. This corresponds to a collocation of geodetictechniques in space. The receiver of the 20 m radiotelescope Wettzell (RTW) has been modified to measurethe GNSS L1 signal without changing the physicalreference point. Preliminary experiments have alreadybeen executed.
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| 5. |
- Kodet, Jan, et al.
(författare)
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Co-locations of Space Geodetic Techniques on Ground and in Space
- 2014
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Ingår i: IVS 2014 General Meeting Proceedings "VGOS: The New VLBI Network", Edited by Dirk Behrend, Karen D. Baver, and Kyla L. Armstrong, Science Press (Beijing). - 9787030429742
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 6. |
- Liu, Li, et al.
(författare)
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New Progress in VLBI tracking of GNSS satellites at GFZ
- 2014
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Ingår i: IVS 2014 General Meeting Proceedings "VGOS: The New VLBI Network", Edited by Dirk Behrend, Karen D. Baver, and Kyla L. Armstrong, Science Press (Beijing). - 9787030429742 ; , s. 456-460
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Tornatore, Vincenza, et al.
(författare)
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Determination of GLONASS satellite coordinates with respect to natural radio sources using the VLBI technique: preliminary results
- 2011
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Ingår i: Proceedings of the European Test and Telemetry Conference ETTC2011, Toulouse, France.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The main objective of this manuscript is topresent tests that have been carried out using VLBI (VeryLong Baseline Interferometry) in order to evaluate if thistechnique, primarily a radio astronomical technique, canalso be used to determine positions of Earth orbitingsatellites. A number of GLONASS (Global NavigationSatellite Systems) satellites, usually used for navigationand positioning purposes, were simultaneously trackedwith two European VLBI radio telescopes in geodeticmode. Software, developed for VLBI tracking ofspacecraft, was successfully used for the processing ofthese GLONASS observations. First results are presentedand discussed.
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| 8. |
- Tornatore, Vincenza, et al.
(författare)
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Direct VLBI Observations of Global Navigation Satellite System Signals
- 2014
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Ingår i: International Association of Geodesy Symposia. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0939-9585. ; 139, s. 247-252
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Konferensbidrag (refereegranskat)abstract
- We describe an experiment carried out to observe signals emitted by GLONASS (GLObalNAvigation Satellite System) satellites using the Very Long Baseline Interferometry (VLBI)technique. This test was performed on a single baseline and had as its primary goal toevaluate the capability of the VLBI system to observe GNSS (Global Navigation SatelliteSystem) signals in terms of scheduling, tracking, acquisition, recording, correlation andprocessing of data.
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| 10. |
- Tornatore, Vincenza, et al.
(författare)
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Single baseline GLONASS observations with VLBI: data processing and first results
- 2011
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Ingår i: Proceedings of the 20th Meeting of the European VLBI Group for Geodesy and Astrometry. - 1864-1113. ; , s. 162-165
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The VLBI technique, in geodetic mode, was used to observe signals emitted by three GLONASS (GLObal NAvigationSatellite System) satellites. The baseline observing simultaneously satellites had at its ends the Medicina (32 m) and Onsala85 (25 m) radio telescopes, both equipped with L-band receivers. Several preparatory tests were necessary for obtaining good data that could be processed. In this paper we report on the observations performed on August 16, 2010 data processing and results of the experiment. The natural radio source 3c286 was observed also as a calibrator before and after satellite observing sessions. A narrow band approach using software primarily developed for astronomical and space applications, was applied to extract the narrow band carrier. Differential frequency on the baseline Medicina-Onsala was also evaluated to compute differential phase which was then adopted to determine satellite coordinate corrections with respect to ITRFvalues. Broad-band correlation was performed on the calibrator data using the DiFX software. The SFXC correlation of satellite data was performed testing near field delay model at extreme nearness; obtained results are described.
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