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Bergstrand, S., Herbertsson, M., Rieck, C., Spetz, J., Svantesson, C.-G. & Haas, R. (2019). A gravitational telescope deformation model for geodetic VLBI. Journal of Geodesy, 93(5), 669-680
Öppna denna publikation i ny flik eller fönster >>A gravitational telescope deformation model for geodetic VLBI
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2019 (Engelska)Ingår i: Journal of Geodesy, ISSN 0949-7714, E-ISSN 1432-1394, Vol. 93, nr 5, s. 669-680Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

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.

Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-36562 (URN)10.1007/s00190-018-1188-1 (DOI)2-s2.0-85053236319 (Scopus ID)
Tillgänglig från: 2018-12-06 Skapad: 2018-12-06 Senast uppdaterad: 2019-06-28Bibliografiskt granskad
Ebenhag, S. C., Hedekvist, P. O., Rieck, C., Bergroth, M., Krehlik, P. & Sliwczynski, L. (2019). Evaluation of Fiber Optic Time and Frequency Distribution System in a Coherent Communication Network. In: IFCS/EFTF 2019 - Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum, Proceedings: . Paper presented at 2019 Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum, IFCS/EFTF 2019, 14 April 2019 through 18 April 2019. Institute of Electrical and Electronics Engineers Inc.
Öppna denna publikation i ny flik eller fönster >>Evaluation of Fiber Optic Time and Frequency Distribution System in a Coherent Communication Network
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2019 (Engelska)Ingår i: IFCS/EFTF 2019 - Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum, Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2019Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

A fiber-based time transfer between UTC(SP) and the VLBI-station at Onsala Space Observatory has been evaluated. The transfer uses a single wavelength in an active coherent DWDM-network in unidirectional duplex fibers and is routed through Reconfigurable Optical Add-Drop Multiplexers.

Ort, förlag, år, upplaga, sidor
Institute of Electrical and Electronics Engineers Inc., 2019
Nyckelord
fiber optics, time dissemination, traceable, Coherent communication, DWDM networks, Onsala Space Observatory, Reconfigurable optical add-drop multiplexer, Single wavelength, Time and frequencies, Fibers
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-40617 (URN)10.1109/FCS.2019.8856039 (DOI)2-s2.0-85073779075 (Scopus ID)9781538683057 (ISBN)
Konferens
2019 Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum, IFCS/EFTF 2019, 14 April 2019 through 18 April 2019
Anmärkning

Funding text 1: This work was supported by 15SIB05-OFTEN, which has received funding from the EMPIR programme co-financed by the Participating States within Euramet and from the European Union's Horizon 2020 research and innovation programme.

Tillgänglig från: 2019-11-25 Skapad: 2019-11-25 Senast uppdaterad: 2019-11-25Bibliografiskt granskad
Jaldehag, K., Jarlemark, P. & Rieck, C. (2019). Further Evaluation of CGGTTS Time Transfer Software. In: IFCS/EFTF 2019 - Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum, Proceedings: . Paper presented at 2019 Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum, IFCS/EFTF 2019, 14 April 2019 through 18 April 2019. Institute of Electrical and Electronics Engineers Inc.
Öppna denna publikation i ny flik eller fönster >>Further Evaluation of CGGTTS Time Transfer Software
2019 (Engelska)Ingår i: IFCS/EFTF 2019 - Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum, Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2019Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

A new software tool for GNSS time transfer implementing the Common GNSS Generic Time Transfer Standard (CGGTTS) was developed by the time and frequency group at RISE Research Institutes of Sweden. The software is called RISEGNSS and converts RINEX observational data into CGGTTS data. It handles codes and carriers of the satellite navigation systems GPS, GLONASS, Galileo and BeiDou including the most important ranging codes for time transfer applications. The software is also prepared for single-frequency applications, and for the use of non-standard codes and carriers such as Galileo PRS and those from SBAS. The aim of the development is to provide an alternative to existing software and to support time transfer with new GNSS. This paper presents a full comparison of new versions of RISEGNSS and the well-established software R2CGGTTS, developed by the Royal Observatory of Belgium. The evaluation includes the linear combinations recommended in the CGGTTS standard for time transfer applications using GPS, GLONASS, Galileo and BeiDou. The aim of the evaluation is to support the development in making CGGTTS data compatible between different stand-alone software as well as those implemented in receivers, which is important to make Common-View (CV) time transfer results precise and accurate. The paper also presents CV time transfer results for three different baselines based on CGGTTS data obtained from the RISEGNSS software. The results include those obtained from dual-frequency code combinations of the four GNSS: GPS, Galileo, GLONASS and BeiDou. The results also include those of using standard single-frequency code observables as well as nonstandard codes and carriers such as L5 for GPS, E5b and E5 (Alt-BOC) for Galileo, G3 for GLONASS, and B3 for BeiDou. It finally studies the possibility and quality of using SBAS for time transfer. 

Ort, förlag, år, upplaga, sidor
Institute of Electrical and Electronics Engineers Inc., 2019
Nyckelord
CGGTTS, GNSS, Software, Time Transfer, Codes (symbols), Computer software, Global positioning system, Petroleum reservoir evaluation, Radio navigation, Linear combinations, Research institutes, Satellite navigation systems, Stand-alone software, Time and frequencies, Application programs
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-40615 (URN)10.1109/FCS.2019.8856022 (DOI)2-s2.0-85073778760 (Scopus ID)9781538683057 (ISBN)
Konferens
2019 Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum, IFCS/EFTF 2019, 14 April 2019 through 18 April 2019
Tillgänglig från: 2019-11-26 Skapad: 2019-11-26 Senast uppdaterad: 2019-11-26Bibliografiskt granskad
Svensson, S., Rieck, C., Bideberg, G. & Larsson, B. (2018). A PMU Calibration System. In: CPEM 2018 - Conference on Precision Electromagnetic Measurements: . Paper presented at 2018 Conference on Precision Electromagnetic Measurements, CPEM 2018, 8 July 2018 through 13 July 2018.
Öppna denna publikation i ny flik eller fönster >>A PMU Calibration System
2018 (Engelska)Ingår i: CPEM 2018 - Conference on Precision Electromagnetic Measurements, 2018Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

There is a need for traceable calibrations of Phasor measurement units, which measures the phase angle of power system signals with respect to the universal time. This paper describes the design of such a calibration system. The system utilizes a fast A-D converter, synchronized to the Swedish time and frequency realization. The speed and synchronization makes the calibration and adjustment fast and relatively straight-forward. Coaxial dividers and shunts are used for system control. The goal is a three-phase system with an angular uncertainty in the order of, or better than ±0.002° or ±100 ns.

Nyckelord
calibration, Measurement, phase angle, phasor measurement standards, traceability, UTC, Phase measurement, Angular uncertainty, Measurement standards, Phase angles, Power system signal, Three phase system, Time and frequencies, Traceable calibration, Phasor measurement units
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-36602 (URN)10.1109/CPEM.2018.8501235 (DOI)2-s2.0-85057058820 (Scopus ID)9781538609736 (ISBN)
Konferens
2018 Conference on Precision Electromagnetic Measurements, CPEM 2018, 8 July 2018 through 13 July 2018
Tillgänglig från: 2018-12-17 Skapad: 2018-12-17 Senast uppdaterad: 2018-12-17Bibliografiskt granskad
Jaldehag, K., Rieck, C. & Jarlemark, P. (2018). Evaluation of CGGTTS time transfer software using multiple GNSS constellations. In: : . Paper presented at 2018 European Frequency and Time Forum (EFTF) (pp. 159-166).
Öppna denna publikation i ny flik eller fönster >>Evaluation of CGGTTS time transfer software using multiple GNSS constellations
2018 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

A new software tool for GNSS time transfer implementing the Common GNSS Generic Time Transfer Standard (CGGTTS) has been developed by the time and frequency group at RISE Research Institutes of Sweden. The software handles signals from the satellite navigation systems GPS, GLONASS, Galileo and BeiDou including the most important ranging codes for time transfer applications. The aim of the development is to provide an alternative to existing software and to support time transfer with new GNSS. The paper presents an evaluation of CGGTTS data calculated with the new software tool in comparison with those calculated using two other, independently developed software tools. It is shown that the results obtained from the different software agree to the sub-nanosecond level. Specifically, the agreement seen between individual GPS, Galileo and BeiDou CGGTTS data is at the 100- to 200-picosecond level. Similarly, GLONASS CGGTTS data agree to the sub-nanosecond level. Further, the paper presents a comparison between time transfer links for both long baselines and short, common-clock baselines obtained from a common view analysis of CGGTTS data from the four mentioned GNSS, as well as a combination of them. It finally discusses other features available from the RISE software, such as non-smoothed CGGTTS data, adoption of satellite orbit and clock products from the IGS as well as the results of an evaluation using linear combinations with non-standard CGGTTS codes and signals.

Nyckelord
Global navigation satellite system, Global Positioning System, Receivers, Satellites, Software tools, Standards, GNSS, Time Transfer, CGGTTS, Software, IGS
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-34325 (URN)10.1109/EFTF.2018.8409022 (DOI)2-s2.0-85050763645 (Scopus ID)
Konferens
2018 European Frequency and Time Forum (EFTF)
Tillgänglig från: 2018-08-07 Skapad: 2018-08-07 Senast uppdaterad: 2019-01-08Bibliografiskt granskad
Rieck, C., Jarlemark, P. & Jaldehag, K. (2018). Passive utilization of the TWSTFT technique. In: : . Paper presented at 2018 European Frequency and Time Forum (EFTF) (pp. 263-269).
Öppna denna publikation i ny flik eller fönster >>Passive utilization of the TWSTFT technique
2018 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

As an active technique TWSTFT is limited in the number of concurrent users on the same communication channel. Using the transmissions of the reference network, passive users can observe the signals in a common view sense and by knowing the orbit of the relaying satellite, corrections describing the dynamic path delay can be used to estimate the clock difference between passive stations. Reliable orbit determination can be achieved using all the active measurements performed by the regular active users. For the EU/US network using Telesat Telstar 11N, the orbit estimation uncertainty is in the order of 1m for the area spanned by the contributing stations. The corresponding time uncertainty for a passive user is about 1 ns, slightly larger than achievable by active links. A passive use of TWSTFT may provide increased timing resiliency for a number of applications. The design of a passive ground station based on a SDR receiver is suggested.

Nyckelord
Orbits, Extraterrestrial measurements, Delays, Satellites, Real-time systems, Atmospheric measurements, Current measurement, TWSTFT, time transfer, orbit determination, passive approach, real-time, resiliency
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-34326 (URN)10.1109/EFTF.2018.8409046 (DOI)2-s2.0-85050723601 (Scopus ID)
Konferens
2018 European Frequency and Time Forum (EFTF)
Tillgänglig från: 2018-08-07 Skapad: 2018-08-07 Senast uppdaterad: 2019-01-10Bibliografiskt granskad
Jiang, Z., Zhang, V. S., Huang, Y. J., Achkar, J., Piester, D., Lin, S. Y., . . . Whibberley, P. B. (2018). Use of software-defined radio receivers in two-way satellite time and frequency transfers for UTC computation. Metrologia, 55(5), 685-698
Öppna denna publikation i ny flik eller fönster >>Use of software-defined radio receivers in two-way satellite time and frequency transfers for UTC computation
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2018 (Engelska)Ingår i: Metrologia, ISSN 0026-1394, E-ISSN 1681-7575, Vol. 55, nr 5, s. 685-698Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Two-way satellite time and frequency transfer (TWSTFT) is a primary technique for the generation of coordinated universal time (UTC). About 20 timing laboratories around the world continuously operate TWSTFT using satellite time and ranging equipment (SATRE19) modems for remote time and frequency comparisons in this context. The precision of the SATRE TWSTFT as observed today is limited by an apparent daily variation pattern (diurnal) in the TWSTFT results. The observed peak-to-peak variation have been found as high as 2 ns in some cases. Investigations into the origins of the diurnals have so far provided no complete understanding about the cause of the diurnals. One major contributor to the diurnals, however, could be related to properties of the receive part in the modem. In 2014 and 2015, it was demonstrated that bypassing the receive part and the use of software-defined radio (SDR) receivers in TWSTFT ground stations (SDR TWSTFT) instead could considerably reduce both the diurnals and the measurement noise. In 2016, the International Bureau of Weights and Measures (BIPM) and the Consultative Committee for Time and Frequency (CCTF) working group (WG) on TWSTFT launched a pilot study on the application of SDR receivers in the TWSTFT network for UTC computation. The first results of the pilot study were reported to the CCTF WG on TWSTFT annual meeting in May 2017, demonstrating that SDR TWSTFT shows superior performance compared to that of SATRE TWSTFT for practically all links between participating stations. In particular, for continental TWSTFT links, in which the strongest diurnals appear, the use of SDR TWSTFT results in a significant suppression of the diurnals by a factor of between two and three. For the very long inter-continental links, e.g. the Europe-to-USA links where the diurnals are less pronounced, SDR TWSTFT achieved a smaller but still significant gain of 30%. These findings are supported by an evaluation of some of the links with an alternate technique based on GPS signals (GPS IPPP) as reported in this paper. Stimulated by these results, the WG on TWSTFT prepared a recommendation for the 21st CCTF meeting, which proposed the introduction of SDR TWSTFT in UTC generation. With CCTF approval of the recommendation, a roadmap was developed for the implementation of SDR TWSTFT in UTC generation. In accordance with the roadmap, most of the stations that participated in the pilot study have updated the SDR TWSTFT settings to facilitate the use of SDR TWSTFT data in UTC generation. In addition, the BIPM conducted a final evaluation to validate the long-term stability of SDR TWSTFT links, made test runs using the BIPM standard software for the calculation of UTC, now including SDR TWSTFT data, and started to calculate SDR TWSTFT time links as backup from October 2017. The use of SDR TWSTFT in UTC generation will begin in 2018.

Nyckelord
diurnal, SDR, time transfer, TWSTFT, uncertainty, UTC, Analog circuits, Global positioning system, Modems, Radio, Radio receivers, Satellites, Software testing, Time measurement, Units of measurement, Coordinated universal time, Software Defined Radio (SDR), Time- and frequency comparisons, Two-way satellite time and frequency transfers, Software radio
Nationell ämneskategori
Fysik
Identifikatorer
urn:nbn:se:ri:diva-37288 (URN)10.1088/1681-7575/aacbe6 (DOI)2-s2.0-85053907924 (Scopus ID)
Tillgänglig från: 2019-01-18 Skapad: 2019-01-18 Senast uppdaterad: 2019-03-28Bibliografiskt granskad
Jiang, Z., Zhang, V., Huang, Y.-J., Achkar, J., Piester, D., Lin, S.-Y., . . . Whibberley, P. (2018). Use of software-defined radio receiversin two-way satellite time and frequencytransfers for UTC computation. Metrologia, 55, 685-698
Öppna denna publikation i ny flik eller fönster >>Use of software-defined radio receiversin two-way satellite time and frequencytransfers for UTC computation
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2018 (Engelska)Ingår i: Metrologia, ISSN 0026-1394, E-ISSN 1681-7575, Vol. 55, s. 685-698Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Two-way satellite time and frequency transfer (TWSTFT) is a primary technique for thegeneration of coordinated universal time (UTC). About 20 timing laboratories around theworld continuously operate TWSTFT using satellite time and ranging equipment (SATRE19)modems for remote time and frequency comparisons in this context. The precision of theSATRE TWSTFT as observed today is limited by an apparent daily variation pattern (diurnal)in the TWSTFT results. The observed peak-to-peak variation have been found as high as 2 nsin some cases. Investigations into the origins of the diurnals have so far provided no completeunderstanding about the cause of the diurnals. One major contributor to the diurnals, however,could be related to properties of the receive part in the modem. In 2014 and 2015, it wasdemonstrated that bypassing the receive part and the use of software-defined radio (SDR) receivers in TWSTFT ground stations (SDR TWSTFT) instead could considerably reduce boththe diurnals and the measurement noise.In 2016, the International Bureau of Weights and Measures (BIPM) and the ConsultativeCommittee for Time and Frequency (CCTF) working group (WG) on TWSTFT launched a pilotstudy on the application of SDR receivers in the TWSTFT network for UTC computation.The first results of the pilot study were reported to the CCTF WG on TWSTFT annualmeeting in May 2017, demonstrating that SDR TWSTFT shows superior performancecompared to that of SATRE TWSTFT for practically all links between participating stations.In particular, for continental TWSTFT links, in which the strongest diurnals appear, the useof SDR TWSTFT results in a significant suppression of the diurnals by a factor of betweentwo and three. For the very long inter-continental links, e.g. the Europe-to-USA links wherethe diurnals are less pronounced, SDR TWSTFT achieved a smaller but still significant gainof 30%. These findings are supported by an evaluation of some of the links with an alternatetechnique based on GPS signals (GPS IPPP) as reported in this paper.Stimulated by these results, the WG on TWSTFT prepared a recommendation for the 21stCCTF meeting, which proposed the introduction of SDR TWSTFT in UTC generation. WithCCTF approval of the recommendation, a roadmap was developed for the implementationof SDR TWSTFT in UTC generation. In accordance with the roadmap, most of the stationsthat participated in the pilot study have updated the SDR TWSTFT settings to facilitatethe use of SDR TWSTFT data in UTC generation. In addition, the BIPM conducted a finalevaluation to validate the long-term stability of SDR TWSTFT links, made test runs using theBIPM standard software for the calculation of UTC, now including SDR TWSTFT data, andstarted to calculate SDR TWSTFT time links as backup from October 2017. The use of SDRTWSTFT in UTC generation will begin in 2018.

Nyckelord
UTC, TWSTFT, SDR, diurnal, uncertainty, time transfer
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-35175 (URN)10.1088/1681-7575/aacbe6 (DOI)
Tillgänglig från: 2018-09-12 Skapad: 2018-09-12 Senast uppdaterad: 2019-05-29Bibliografiskt granskad
Rieck, C., Jarlemark, P. O. .. & Jaldehag, K. (2017). Utilizing TWSTFT in a passive configuration. In: Proceedings of the Annual Precise Time and Time Interval Systems and Applications Meeting, PTTI: . Paper presented at Precise Time and Time Interval Systems and Applications Meeting, PTTI 2017, 30 January 2017 through 2 February 2017 (pp. 219-234). Institute of Electrical and Electronics Engineers Inc.
Öppna denna publikation i ny flik eller fönster >>Utilizing TWSTFT in a passive configuration
2017 (Engelska)Ingår i: Proceedings of the Annual Precise Time and Time Interval Systems and Applications Meeting, PTTI, Institute of Electrical and Electronics Engineers Inc. , 2017, s. 219-234Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

In this paper we suggest the passive usage of Two Way Satellite Time and Frequency Transfer (TWSTFT). In a passive configuration a receiver observes, possibly multiple, codes sent by the active users of a TWSTFT-network. Common view observations of the same signals by a pair of observers can be used to compare their local clocks. Similar to GNSS, the users need to know their local coordinates and the orbit of the satellite in order to reduce the measurements by the geometry. As the orbit is usually poorly known, it is essential to establish an infrastructure that provides the users with satellite ephemerides and appropriated correction models. In this initial study we use the ranging measurements performed by the active European network to TELSTAR 11N in order to estimate precise satellite positions. Residual ranges of the position estimates are well below 1 m. Based on the precise satellite positions and other regular TWSTFT measurements an extended Kepler description of the orbit is determined, which can be used to estimate ranges from the satellite to a passive user at arbitrary station positions and arbitrary epochs. A passive use of TWSTFT will enable us to increase the number of measurements without increasing the noise level on the transponder. It will also reach out to a new group of users, both commercial and scientific, which will benefit from current and future developments of TWSTFT. NMIs will be able to offer an independent method for robust distribution of their national time scales. © 2017 Institute of Electrical and Electronics Engineers Inc. All rights reserved.

Ort, förlag, år, upplaga, sidor
Institute of Electrical and Electronics Engineers Inc., 2017
Nyckelord
Orbits, Satellites, Time measurement, Correction models, European networks, Local coordinate, Position estimates, Residual range, Satellite ephemeris, Satellite position, Two-way satellite time and frequency transfers, Tracking (position)
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:ri:diva-38134 (URN)10.33012/2017.15002 (DOI)2-s2.0-85047020426 (Scopus ID)9781510855397 (ISBN)
Konferens
Precise Time and Time Interval Systems and Applications Meeting, PTTI 2017, 30 January 2017 through 2 February 2017
Tillgänglig från: 2019-03-04 Skapad: 2019-03-04 Senast uppdaterad: 2019-08-09Bibliografiskt granskad
Jaldehag, K., Jarlemark, P. & Rieck, C. (2016). Clock models for Kalman filtering.
Öppna denna publikation i ny flik eller fönster >>Clock models for Kalman filtering
2016 (Engelska)Rapport (Övrigt vetenskapligt)
Serie
SP Rapport, ISSN 0284-5172 ; 2016:48
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-623 (URN)
Tillgänglig från: 2016-06-29 Skapad: 2016-06-29 Senast uppdaterad: 2018-08-13Bibliografiskt granskad
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0003-1710-6058

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