scholarly journals Observing UT1-UTC with VGOS

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Rüdiger Haas ◽  
Eskil Varenius ◽  
Saho Matsumoto ◽  
Matthias Schartner
Keyword(s):  
Standard Deviation ◽  
Reference Frame ◽  
Earth Rotation ◽  
Space Observatory ◽  
International Earth Rotation ◽  
Onsala Space Observatory ◽  
X Band ◽  
First Results

AbstractWe present first results for the determination of UT1-UTC using the VLBI Global Observing System (VGOS). During December 2019 through February 2020, a series of 1 h long observing sessions were performed using the VGOS stations at Ishioka in Japan and the Onsala twin telescopes in Sweden. These VGOS-B sessions were observed simultaneously to standard legacy S/X-band Intensive sessions. The VGOS-B data were correlated, post-correlation processed, and analysed at the Onsala Space Observatory. The derived UT1-UTC results were compared to corresponding results from standard legacy S/X-band Intensive sessions (INT1/INT2), as well as to the final values of the International Earth Rotation and Reference Frame Service (IERS), provided in IERS Bulletin B. The VGOS-B series achieves 3–4 times lower formal uncertainties for the UT1-UTC results than standard legacy S/X-band INT series. The RMS agreement w.r.t. to IERS Bulletin B is slightly better for the VGOS-B results than for the simultaneously observed legacy S/X-band INT1 results, and the VGOS-B results have a small bias only with the smallest remaining standard deviation.

scholarly journals Observing UT1-UTC with VGOS

2020 ◽  
Author(s):  
Rüdiger Haas ◽  
Eskil Varenius ◽  
Saho Matsumoto ◽  
Matthias Schartner
Keyword(s):  
Reference Frame ◽  
Root Mean Square ◽  
Earth Rotation ◽  
Mean Square ◽  
Space Observatory ◽  
International Earth Rotation ◽  
Onsala Space Observatory

Abstract We present rst results of UT1-UTC determinations using the VLBI Global Observing System (VGOS). During December 2019 through February 2020 a series of 1 hour long observing sessions were performed using the VGOS stations at Ishioka in Japan and the Onsala twin telescopes in Sweden. The data of this VGOS-B series were correlated, post-correlation processed, and analysed at the Onsala Space Observatory. The derived UT1-UTC results were compared to corresponding results from standard legacy S/X Intensive sessions (INT1/INT2), as well to the nal values of the International Earth Rotation and Reference Frame Service (IERS), provided in IERS Bulletin B. The VGOS-B series achieve 3-4 times lower formal uncertainties for the UT1-UTC results than standard legacy S/X INT series. Furthermore, the root mean square (RMS) agreement with respect to the IERS Bulletin B is 30-40 % better for the VGOS-B results than for the INT1/INT2 results.

scholarly journals Tidal Parameters as a Tool for the Determination of the Coordinates of the SLR Stations

2019 ◽  
Vol 54 (4) ◽  
pp. 129-135
Author(s):  
Marcin Jagoda ◽  
Miłosáawa Rutkowska ◽  
Romuald Obuchovski ◽  
Czesław Suchocki ◽  
Jacek Katzer
Keyword(s):  
Reference Frame ◽  
Earth Rotation ◽  
Reference System ◽  
Satellite Geodesy ◽  
Satellite Laser Ranging ◽  
Laser Ranging ◽  
System Service ◽  
International Earth Rotation

Abstract One of the primary objectives of satellite geodesy is the determination of coordinates of the satellite laser ranging (SLR) stations. This task is conducted by using laser ranging techniques. The main goal of the current study was to assess the influence of using varied values of the tidal parameters (Love h2 and Shida l2 numbers) on the determination of the positions of chosen SLR stations. The obtained results are presented for coordinates determination conducted for six SLR stations: Mt Stromlo (no. 7825, Australia), Matera (no. 7941, Italy), Grasse (no. 7845, France), McDonald (no. 7080, USA), Arequipa (no. 7403, Peru) and Beijing (no. 7249, China). The analysis covers SLR data for 2 satellites (LAGEOS1 and LAGEOS2), which were observed for 10 consecutive years (from 2008 to 2018). The analysis was performed using the ITRF2014 reference frame in two scenarios of calculations. In scenario 1, the SLR stations coordinates were calculated using the nominal values as per the International Earth Rotation and Reference System Service (IERS) standards recommendation of the Love/Shida numbers: h2 = 0.6078, l2 = 0.0847. In scenario 2, the coordinates were estimated using the harnessing values of the Love/Shida numbers (h2 = 0.6140 and l2 = 0.0876), which were proposed by authors in a previous publication. The effect of the application of different values of the Love/Shida numbers for the determination of SLR stations coordinates was scrutinized.

THE ANALYSIS OF THE STABILITY OF PERMANENT GPS STATION VILNIUS (VLNS) / NUOLAT VEIKIANČIOS VILNIAUS (VLNS) GPS STOTIES STABILUMO ANALIZĖ / АНАЛИЗ СТАБИЛЬНОСТИ ПОСТОЯННО ДЕЙСТВУЮЩЕЙ СТАНЦИИ ГПС VILNIUS (VLNS)

2011 ◽  
Vol 37 (3) ◽  
pp. 129-134 ◽  
Author(s):  
Eimuntas Paršeliūnas ◽  
Ričardas Kolosovskis ◽  
Raimundas Putrimas ◽  
Arūnas Būga
Keyword(s):  
Earth Rotation ◽  
Current Status ◽  
Main Task ◽  
Technical Equipment ◽  
Space Observatory ◽  
International Earth Rotation Service ◽  
Gps Satellites ◽  
Onsala Space Observatory ◽  
The Stability ◽  
Gps Station

Lithuania has been participating in the activities of the EUREF permanent network since 1996, when GPS station VILNIUS started regular continuous tracking of GPS satellites. The GPS station was established with a help of the Onsala Space Observatory (Sweden) and was mounted in the territory of Vilnius international airport (Lithuania). Four character identifier VLNS and DOMES number 10801M001 were assigned to VILNIUS GPS station by the International Earth Rotation Service in 1999. VILNIUS station is operated and maintained by the Institute of Geodesy of Vilnius Technical University. The main task of the permanent VLNS GPS station is to take part in EUREF activities and serve as reference to GPS campaigns in Lithuania. The aim of this paper is to describe the evolution and current status of the technical equipment of VILNIUS station. The paper also presents the analysis of data quality and a few years interval of coordinate determination at VLNS within the EUREF network. Santrauka EUREF nuolat veikiančių stočių tinklo veikloje Lietuva dalyvauja nuo 1996 m., kai GPS VILNIAUS stotis pradėjo reguliarius matavimus iš GPS palydovų. Stotis įsteigta padedant Onsalos kosmoso observatorijai (Švedija). GPS stotis įrengta Vilniaus tarptautinio oro uosto teritorijoje 1999 metais. Tarptautinė žemės sukimositarnyba stočiai suteikė keturių simbolių identifikatorių VLNS ir DOMES numerį 10801M001. GPS VILNIAUS stotį prižiūri ir valdo Vilniaus Gedimino technikos universiteto Geodezijos instituto specialistai. Pagrindinis stoties uždavinys yra dalyvauti EUREF veikloje, ir tai turi būti atraminis geodezinis punktas GPS kampanijoms Lietuvoje. Straipsnio tikslas – aprašyti dabartinę techninės įrangos būklę ir jos tobulinimo eigą. Pateikiama kelerių metų matavimo duomenų kokybės analizė ir nustatytos koordinatės EUREF tinkle. Резюме В проекте сети постоянно действующих станций ГПС EUREF Литва участвует с 1996 г., когда станция VILNIUS стала производить постоянные измерения со спутников ГПС. Станция была основана при помощи Онсольской космической oбсерватории (Швеция). Станция ГПС установлена на территории Вильнюсского международного аэропорта. В 1999 г. Международная служба вращения Земли присвоила станции код VLNS и DOMES номер 10801М001. Станцией управляют специалисты из Геодезического института Вильнюсского технического университета им. Гедиминаса. Главной задачей станции является участие в мероприятиях EUREF, а также быть основным геодезическим пунктом в кампаниях ГПС на территории Литвы. В статье преследовалась цель описать состояние технического оборудования станции и меры по его улучшению. Представлен анализ данных измерений ГПС за несколько лет и определены геодезические координаты в сети EUREF.

Short-baseline interferometry at Onsala Space Observatory

2021 ◽  
Author(s):  
Eskil Varenius ◽  
Rüdiger Haas ◽  
Periklis Diamantidis ◽  
Tobias Nilsson
Keyword(s):  
Mixed Mode ◽  
Reference Frames ◽  
Radio Telescopes ◽  
Space Observatory ◽  
Short Baseline ◽  
Geodetic Vlbi ◽  
Onsala Space Observatory ◽  
X Band ◽  
The Impact ◽  
Local Tie

<p>A growing number of geodetic VLBI stations participate in the VLBI Global Observing System (VGOS). Multiple sites operate both new VGOS telescopes and legacy S/X VLBI telescopes. At Onsala Space Observatory, Sweden, we operate two 13.2 m diameter VGOS radio telescopes, ONSA13NE (OE) and ONSA13SW (OW), as well as the 20~m legacy S/X telescope ONSALA60 (ON). Transitioning from the legacy system and providing continuity of the terrestrial and celestial reference frames necessitate establishing ties between S/X and VGOS telescopes. Since spring 2019, we have carried out more than 20 short-baseline (550 m) interferometric observations at X-band to establish local-tie vectors between ON, OE and OW. The obtained data were correlated at Onsala Space Observatory using DiFX, post-processed using HOPS and analysed with nuSolve and ASCOT. In this presentation we given an overview of the observations, analysis, and results of these local-tie experiments. We investigate the impact of modeling e.g. gravitational deformation, and the possibility of using phase-delays to improve the precision. Finally, we present a comparison with preliminary results from two other methods: global mixed-mode observations and classical local-tie measurements.</p>

scholarly journals Earth Rotation Information Derived from Merit and Polaris VLBI Observations

1981 ◽  
Vol 63 ◽  
pp. 97-122 ◽  
Author(s):  
D. S. Robertson ◽  
W. E. Carter
Keyword(s):  
Earth Rotation ◽  
The United States ◽  
Geodetic Survey ◽  
West Germany ◽  
National Geodetic Survey ◽  
Space Observatory ◽  
Paper Briefly ◽  
Owens Valley ◽  
Radio Observatory ◽  
Onsala Space Observatory

AbstractIn September and October 1980, the National Geodetic Survey, jointly with the National Aeronautics and Space Administration and several other agencies and institutions, conducted a series of astronomical radio interferometry (VLBI) observing sessions to support the IAU/IUGG MERIT short campaign. A total of 14 days of observations, organized into two 7-day sessions, was collected by three observatories in the United States (Harvard Radio Astronomy Station (HRAS), Haystack Observatory, and Owens Valley Radio Observatory) and the Onsala Space Observatory in Sweden. Chilbolton Observatory, England, and Effelsberg Observatory, West Germany, also participated on some days. Immediately following the MERIT campaign, NGS initiated a series of 24-hour observing sessions, spaced at approximately 2-week intervals, as a pilot program to project POLARIS. All of these sessions included two observatories, HRAS and Haystack, and Onsala participated in about half of the sessions. The MERIT and POLARIS observations were made with the third generation MARK III VLBI system using procedures and schedules designed to yield high quality geodetic information, including Earth rotation values. This paper briefly traces the planning, observing, and data processing activities, and presents the Earth rotation information thus far derived from the data.

scholarly journals VGOS Intensives Ishioka-Onsala

2021 ◽  
Author(s):  
Rüdiger Haas ◽  
Eskil Varenius ◽  
Periklis-Konstantinos Diamantidis ◽  
Saho Matsumotu ◽  
Matthias Schartner ◽  
...  
Keyword(s):  
Earth Rotation ◽  
Mean Square ◽  
Radio Telescopes ◽  
Analysis Software ◽  
Space Observatory ◽  
Software Packages ◽  
Onsala Space Observatory ◽  
Observation Program ◽  
International Vlbi Service ◽  
Near Future

<p>The VLBI Global Observing System (VGOS) is the VLBI contribution to GGOS. During the last years, several VGOS stations have been established, the VGOS observation program has started, and by 2021 VGOS has achieved an operational state involving nine international VGOS stations. Further VGOS stations are currently being installed, so that the number of active VGOS stations will increase drastically in the near future. In the end of 2019 the International VLBI Service for Geodesy and Astrometry (IVS) decided to start a new and so-far experimental VGOS-Intensive series, called VGOS-B, involving Ishioka (Japan) and Onsala (Sweden). Both sites operate modern VGOS stations with 13.2~m diameter radio telescopes, i.e. ISHIOKA (IS) in Japan, and ONSA13NE (OE) and ONSA13SW (OW) in Sweden. In total 12 VGOS-B sessions were observed between December 2019 and February 2020, one every week, in parallel and simultaneously to legacy S/X INT1 Intensive sessions that involve the stations KOKEE (KK) on Hawaii and WETTZELL (WZ) in Germany. These 1-hour long VGOS-B sessions consist of more than fifty radio source observations, resulting in about 1.6 TB of raw data that are collected at each station. The scheduling of the VGOS-B sessions was done using <em>VieSched++</em> and the subsequent steps (correlation, fringe-fitting, database creation) were carried out at the Onsala Space Observatory using <em>DIFX</em> and <em>HOPS</em>. The resulting VGOS databases were  analysed with several VLBI analysis software packages, involving <em>nuSolve</em>, <em>c5++</em> and <em>ASCOT</em>. In this presentation, we give an overview on the VGOS-B series, present our experiences, and discuss the obtained results. The derived UT1-UTC results were compared to corresponding results from standard legacy S/X Intensive sessions (INT1/INT2), as well to the final values of the International Earth Rotation and Reference Frame Service (IERS), provided in IERS Bulletin~B. <br>The VGOS-B series achieve 3-4 times lower formal uncertainties for the UT1-UTC results than standard legacy S/X INT series.  Furthermore, the root mean square (RMS) agreement with respect to the IERS Bulletin B is 30-40 % better for the VGOS-B results than for the INT1/INT2 results.</p>

scholarly journals A Polarimetric Radar Approach to Identify Rain, Melting-Layer, and Snow Regions for Applying Corrections to Vertical Profiles of Reflectivity

2007 ◽  
Vol 46 (2) ◽  
pp. 154-166 ◽  
Author(s):  
Sergey Y. Matrosov ◽  
Kurt A. Clark ◽  
David E. Kingsmill
Keyword(s):  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Sierra Nevada ◽  
Test Bed ◽  
Radar Rainfall ◽  
Melting Layer ◽  
Freezing Level ◽  
X Band ◽  
Relative Standard

Abstract This article describes polarimetric X-band radar-based quantitative precipitation estimations (QPE) under conditions of low freezing levels when, even at the lowest possible elevation angles, radar resolution volumes at longer ranges are in melting-layer or snow regions while it rains at the ground. A specifically adjusted vertical-profile-of-reflectivity (VPR) approach is introduced. The mean VPR is constructed based on the range–height indicator scans, and the effects of smoothing of brightband (BB) features with range are accounted for. A principal feature of the suggested QPE approach is the determination of the reflectivity BB boundaries and freezing-level heights on a beam-by-beam basis using the copolar correlation coefficient ρhv, which is routinely available from the X-band radar measurements. It is shown that this coefficient provides a robust discrimination among the regions of rain, melting hydrometeors, and snow. The freezing-level estimates made using ρhv were within 100–200 m from the corresponding estimates of the 0° isotherm heights from radiosonde soundings. The suggested VPR approach with the polarimetric determination of the reflectivity BB boundaries was used for QPE during the wintertime deployment of the NOAA X-band radar as part of the 2006 Hydrometeorological Test Bed (HMT-06) field experiment in the California Sierra Nevada foothills. It is shown that this approach noticeably improves radar-rainfall accumulation estimates. The use of the HMT-06 mean X-band reflectivity–rain-rate (Zeh–R) relation resulted in an approximately 65% relative standard deviation of radar estimates from the surface rain gauges if no VPR adjustments were made. Applying the VPR approach with polarimetric detection of the melting layer resulted in reduction of the corresponding relative standard deviation by about a factor of 2.

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

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.

Requirements for a radio coordinate reference frame for the determination of Earth rotation parameters

1978 ◽  
Vol 48 ◽  
pp. 171-174
Author(s):  
K. Johnston ◽  
J. Spencer ◽  
C. Mayer ◽  
W. Klepczynski ◽  
G. Kaplan ◽  
...  
Keyword(s):  
West Virginia ◽  
Radio Source ◽  
Reference Frame ◽  
Earth Rotation ◽  
Earth Rotation Parameters ◽  
Rotation Parameters

The requirements for a radio reference frame to be used for the determination of Earth rotation parameters are given. The use of the NRAO interferometer at Green Bank, West Virginia for the initial radio interferometric studies of Earth rotation on a regular basis is also described. A catalog of accurate radio source positions will result from this study.

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