First results of real-time time and frequency transfer using GPS code and carrier phase observations

Jarlemark, Per; Jaldehag, Kenneth; Rieck, Carsten; Johansson, Jan M.

doi:10.1109/freq.2003.1275111

Cited by 6 publications

(7 citation statements)

References 4 publications

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“…The terms with tilde represent the quantities obtained by prediction and the terms with caret represent the quantities obtained by measurement update. Equation (7) shows the measurement update of the estimate error covariance combined with covariance x-reduction. Assuming that n is the number of the member clocks and the two-state clock model is used for each member clock, S becomes a 2n × 2n identity matrix with diagonal elements that correspond to the individual clock phases set to zero [13].…”

Section: Kalman Filter-based Ensemble Clockmentioning

confidence: 99%

“…Some other studies made use of GPS CP in realtime frequency transfer [5,6] and their strategies were based on time differencing of the CP signal. Another study tested various solution strategies for real-time time and frequency transfer using the GPS CP measurements and concluded that among the real-time solutions tested, the common-view-type real-time solution yielded the best agreement with the postprocessed solution [7].…”

Section: Introductionmentioning

confidence: 99%

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Real-time formation of a time scale using GPS carrier-phase time transfer network

Lee

2009

Metrologia

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This paper presents a prototype real-time clock ensemble system that utilizes a Kalman filter-based ensemble algorithm to combine remote clocks linked via a real-time GPS carrier-phase time transfer network. The calculated ensemble clock is realized by the use of an optimal control technique, where emphasis is placed on seeking a balance between the short-term stability of a hydrogen maser clock and the long-term stability of the ensemble clock. The performance of the system is investigated by conducting a five-month long ensemble experiment based on local realizations of UTC from four timing laboratories, and the frequency stability of the real-time ensemble time scale as well as its realizations are assessed with reference to UTC.

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Section: Kalman Filter-based Ensemble Clockmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Real-time formation of a time scale using GPS carrier-phase time transfer network

Lee

2009

Metrologia

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“…[1]. The limit for real time solutions is about 100 ps [2]. Uncertainties due to temperature-induced delays can accumulate up to several 100 ps or even to the ns level for a badly controlled system, see e.g.…”

Section: Introductionmentioning

confidence: 99%

Thermal influence on the receiver chain of GPS carrier phase equipment for time and frequency transfer

Rieck¹,

Jarlemark²,

Jaldehag³

et al.

IEEE International Frequency Control Sympposium and PDA Exhibition Jointly With the 17th European Frequency and Time Forum, 200

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In this study a temperature controlled environment is used in order to quantify the thermal influence on all major parts of state of the art geodetic GPS receiving equipment. Temperature variations, effective as time delay variations, were identified as a dominating error source that degrades the capabilities of carrier phase GPS based time and frequency transfer considerably. For purely code-based measurements with uncertainties in the ns range is temperature rarely an issue. In contrast carrier phase observations offer potentially a two orders of magnitude better accuracy and are therefore suitable for exploiting the characteristics of maser quality clocks. However, the stability of the environment around the receiver equipment defines the achievable accuracy. Four distinct parts of the receiver chain were subject to systematic measurements of the temperature-delay dependency: antenna preamplifier, antenna and clock cables, power distribution devices and geodetic receivers. A temperature controllable climate chamber was deployed with the respective component to follow a long time-constant temperature stepping. Signal through devices were mainly tested in a vector-voltmeter approach. Zero base line GPS processing was used to test receivers. With individual component temperature dependence being far above the expected accuracy of carrier phase based time and frequency transfer it underlines the necessity to include temperature as an important parameter into time/frequency solutions.

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“…However, they used the observed part of the ultra-rapid ephemeris rather than the predicted part, which is not possible in real-time applications. Another study tested various solution strategies for real-time time and frequency transfer using the GPS CP measurements and concluded that among the realtime solutions tested, the common-view (CV) type real-time solution yielded the best agreement with the post-processed solution [11].…”

Section: Introductionmentioning

confidence: 99%

Real-time linked common-view time transfer for monitoring GNSS system time differences

Lee

2012

Metrologia

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This paper presents results obtained by conducting real-time linked common-view (CV) Global Navigation Satellite System (GNSS) time transfer between stations that are supposed to maintain various GNSS system times including those of GPS and Galileo. The distance between those stations is typically more than 5000 km and the conventional CV GPS time transfer may not be feasible for such long-distance time transfer. We used the real-time linked CV time transfer technique to monitor the GNSS system time differences, and the time links examined in this study are the USNO–PTB link for the GPS–Galileo system time difference and the USNO–NICT link for the GPS–QZSS system time difference. The performance of the developed time transfer method was assessed by comparing against other time transfer solutions such as TWSTFT. Finally, global closure was formed to examine the inherent noise level of the method in a self-sufficient way. Results showed that the real-time linked CV time transfer solution yields sub-nanosecond-level agreement with the reference solutions including TWSTFT, and its frequency stability is generally at the level of (3–4) × 10−15 in terms of the modified Allan deviation at the averaging time of one day, which seems to be sufficient to support civil interoperability between different GNSSs for sub-metre-level accuracy.

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First results of real-time time and frequency transfer using GPS code and carrier phase observations

Cited by 6 publications

References 4 publications

Real-time formation of a time scale using GPS carrier-phase time transfer network

Real-time formation of a time scale using GPS carrier-phase time transfer network

Thermal influence on the receiver chain of GPS carrier phase equipment for time and frequency transfer

Real-time linked common-view time transfer for monitoring GNSS system time differences

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