Results of the 2008 TWSTFT calibration of seven european stations

Bauch, A.; Piester, D.; Blanzano, B.; Koudelka, Otto; Kroon, Erik; Dierikx, Erik; Whibberley, Peter; Achkar, Joseph; Rovera, Daniele; Lorini, L.; Cordara, F.; Schlunegger, C.

doi:10.1109/freq.2009.5168392

Cited by 8 publications

(6 citation statements)

References 2 publications

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“…Breakiron et al (2005) report for a series of intra U.S. calibration campaigns overall uncertainties down to 0.38 ns. On the other hand also values of slightly above 1 ns have been reported for recent European campaigns (Bauch et al, 2009) which lead us to conclude that using currently available equipment link uncertainties between 0.4 ns and 1.2 ns are achievable.…”

Section: Two-way Satellite Time and Frequency Transfermentioning

confidence: 54%

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Remote atomic clock synchronization via satellites and optical fibers

et al. 2011

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In the global network of institutions engaged with the realization of International Atomic Time (TAI), atomic clocks and time scales are compared by means of the Global Positioning System (GPS) and by employing telecommunication satellites for two-way satellite time and frequency transfer (TWSTFT). The frequencies of the state-of-the-art primary caesium fountain clocks can be compared at the level of 10 -15 (relative, 1 day averaging) and time scales can be synchronized with an uncertainty of one nanosecond. Future improvements of worldwide clock comparisons will require also an improvement of the local signal distribution systems. For example, the future ACES (atomic clock ensemble in space) mission shall demonstrate remote time scale comparisons at the uncertainty level of 100 ps.To ensure that the ACES ground instrument will be synchronized to the local time scale at PTB without a significant uncertainty contribution, we have developed a means for calibrated clock comparisons through optical fibers. An uncertainty below 50 ps over a distance of 2 km has been demonstrated on the campus of PTB. This technology is thus in general a promising candidate for synchronization of enhanced time transfer equipment with the local realizations of UTC .Based on these experiments we estimate the uncertainty level for calibrated time transfer through optical fibers over longer distances. These findings are compared with the current status and developments of satellite based time transfer systems, with a focus on the calibration techniques for operational systems.

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Section: Two-way Satellite Time and Frequency Transfermentioning

confidence: 54%

“…Distance (km) Uncertainty (ns) References GPS ~20 000 < 1.6 to 5 Esteban et al 2010, Feldmann et al, 2011, Circular T 2010 TWSTFT ~10 000 ~0.4 to ~1.2 Breakiron et al, 2005, Piester et al, 2008, Bauch et al 2009 Optical Fibers ~1500 < 0.1 to 0.2 Rost et al 2010, this work…”

Section: Discussionmentioning

confidence: 82%

Remote atomic clock synchronization via satellites and optical fibers

et al. 2011

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“…The last TW calibrations were performed in 2008 [6], and they were lost because of the change in satellites in July 2009. The calibrations were restored with the help of bridges made at the BIPM with the respective GPS PPP links with one exception (NPL) due to equipment failure [8].…”

Section: Andxuuhqw 87and Fdoleudwlrq Srolf\mentioning

confidence: 99%

“…The GPS P code calibration was also a differential calibration with BIPM standard equipment which was absolutely calibrated in 2001 [4]. The first TW calibrations for 3 European laboratories (TUG, DTAG and PTB) were made in 1997 [5] and the latest for 7 European laboratories (CH, IT, OP, NPL, PTB, SP, VSL) [6] and for USNO-PTB were carried out in 2008. These calibrations were performed with traditional methods.…”

Section: Qwurgxfwlrqmentioning

confidence: 99%

Toward new procedures in TWSTFT and GNSS delay characterization for UTC time transfer?

Jiang

Arias

Lewandowski

et al. 2010

EFTF-2010 24th European Frequency and Time Forum

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7LPH )UHTXHQF\ DQG *UDYLPHWU\ 6HFWLRQ %XUHDX ,QWHUQDWLRQDO GHV 3RLGV HW 0HVXUHV %,30 3DYLOORQ GH %UHWHXLO ) 6(95(6 &('(; )UDQFH ]MLDQJ#ELSPRUJ $EVWUDFW 87& generation includes the computation of 87&-87&(N) and its uncertainty estimation. A significant part of the uncertainty of the 87& approximations 87&(N) in national contributing laboratories is based on accurate metrological measurement of time transfer equipment delays (so called "equipment calibration"). Organizing and maintaining the calibration of the time transfer facilities contributing to 87& is among the responsibilities of the BIPM. At present, the time transfer techniques used for UTC generation are based on the two-way satellite time and frequency transfer (TWSTFT or TW) and the global navigation satellite systems (GNSS), i.e. GPS and GLN (Glonass). They are used for calculating the differences [87&(N) -87& (O)] between any participating laboratory and that chosen as a pivot (at present the PTB). In the 1980s, GPS C/A technique dominated the 87& time transfer. Since 2000, TW and GPS MC, P3 and PPP techniques as well as GLN have been successively introduced in the UTC generation. In consequence, the calibrations of the different time transfer equipment were introduced and are performed separately. Today, there are four parallel types of independent calibrations based on different strategies that can be defined either as site-based or link-based. The BIPM has assigned values of u B of about 1 ns for the link-based TW calibrations, based on the values reported by those performing the calibration. However, for the sited-based GNSS calibrations, a conventional value of 5 ns has generally been assigned. This choice has been motivated by studies which found that values of [87&(N) -87& (O)] bigger the respective u B may exist when the link as calculated by different techniques, and because long-term instability of the standard receivers may cause inconstancy in individual calibrations carried out in different periods.On the other side, due to the development in technology, the statistical uncertainty u A has been reduced by a factor of 10 since a dozen of years. The state of the art of u A is 0.5 ns for TW and 0.3 ns for GPS PPP. The u B calibration uncertainty is dominant in the total uncertainty of [87&-87&(N)], and several authors have investigated how to improve the calibration of time transfer equipment to decrease its value.

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“…The approach of the calibration approach can either be operated in GPS common view (CV) or all in view (AV) mode with the code observation, which only provides the nanosecond accuracy level almost limited to the observations [3–6]. Since the GPS carrier phase (CP) is more precise than the code observation, the CP is utilised in order to improve the calibration uncertainty recently [7–11]. However, the previous researches using CP technique were mainly focused on the specific implementation procedures in the process of time link calibration, but the exact mechanism of how GPS CP approach works in the case of time link calibration data processing remains still unclear [2, 3, 11].…”

Section: Introductionmentioning

confidence: 99%