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See detailAccurate Determination of the Earth Tidal Parameters at the BIPM to Support the Watt Balance Project
Francis, Olivier UL; Rothleitner, Christian UL; Jiang, Z.

in Rizos, C.; Willis, P. (Eds.) Earth on the Edge: Science for a Sustanaible Planet (2014)

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See detailAccurate Gravimetry at the BIPM Watt Balance Site
Jiang, Z.; Palinkas, V.; Francis, Olivier UL et al

in Rizos, C.; Willis, P. (Eds.) Earth on the Edge: Science for a Sustanaible Planet (2014)

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See detailMeasurement of the speed-of-light perturbation of free-fall absolute gravimeters
Rothleitner, Christian UL; Niebauer, Tim; Francis, Olivier UL

in Metrologia (2014), 51(3), 9

We report on a direct measurement of the relativistic Doppler shift with a commercial free-fall absolute gravimeter of the type FG5X. The observed Doppler shift, which is commonly called speed-of-light ... [more ▼]

We report on a direct measurement of the relativistic Doppler shift with a commercial free-fall absolute gravimeter of the type FG5X. The observed Doppler shift, which is commonly called speed-of-light perturbation, can be well described by the relativistic Doppler formula, where the constant object velocity is replaced by a time-dependent velocity with constant acceleration. The observed speed-of-light perturbation stands in contrast to other publications, which predict a higher frequency shift. It has been measured with a relative uncertainty of 1.1 × 10 −3 . [less ▲]

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See detailOn the gravimetric contribution to watt balance experiments
Jiang, Z.; Pálinkáš, V.; Francis, Olivier UL et al

in Metrologia (2013), 50(5), 452

It has been recommended that the relative standard uncertainty of the numerical value of the Planck constant required for the redefinition of the kilogram should not exceed 2 × 10 −8 . To reach this goal ... [more ▼]

It has been recommended that the relative standard uncertainty of the numerical value of the Planck constant required for the redefinition of the kilogram should not exceed 2 × 10 −8 . To reach this goal using experiments based on a watt balance, the free-fall acceleration ( g ) traceable to the SI, at a given point and a given time, needs to be known with a sufficiently small uncertainty well below 2 × 10 −8 . Reducing the uncertainty in g allows the other uncertainties related to the watt balance to be increased. Instead of a simultaneous operation of an absolute gravimeter with a watt balance, we propose an alternative approach and demonstrate that a standard uncertainty below 5 µGal (relative uncertainty of 5 × 10 −9 ) is reachable under the conditions at BIPM. Further decreasing the uncertainty could significantly increase commitments in terms of personnel and equipment and would not significantly improve the uncertainty targeted for the BIPM watt balance experiment. A 5 µGal uncertainty might also satisfy the needs of other watt balance experiments underway or planned. In our approach we combine the following information: (1) the Key Comparison Reference Values obtained from the CCM.G-K1, a key comparison carried out in the frame of the International Comparison of Absolute Gravimeters in 2009 (ICAG2009); (2) the accurate gravity network established using the qualified absolute and relative gravimeters; (3) temporal gravity variations based on observed Earth-tide parameters and modelled effects of polar motion and atmospheric mass redistribution; (4) uncertainty estimates that account for non-modelled effects; (5) the option to carry out absolute gravity measurements once every one or two years with two or more gravimeters for monitoring the stability of the gravity field at the BIPM. [less ▲]

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See detailThe European Comparison of Absolute Gravimeters 2011 (ECAG-2011) in Walferdange, Luxembourg: results and recommendations
Francis, Olivier UL; Baumann, Henri; Volarik, Tomas et al

in Metrologia (2013), 50(3), 257

We present the results of the third European Comparison of Absolute Gravimeters held in Walferdange, Grand Duchy of Luxembourg, in November 2011. Twenty-two gravimeters from both metrological and non ... [more ▼]

We present the results of the third European Comparison of Absolute Gravimeters held in Walferdange, Grand Duchy of Luxembourg, in November 2011. Twenty-two gravimeters from both metrological and non-metrological institutes are compared. For the first time, corrections for the laser beam diffraction and the self-attraction of the gravimeters are implemented. The gravity observations are also corrected for geophysical gravity changes that occurred during the comparison using the observations of a superconducting gravimeter. We show that these corrections improve the degree of equivalence between the gravimeters. We present the results for two different combinations of data. In the first one, we use only the observations from the metrological institutes. In the second solution, we include all the data from both metrological and non-metrological institutes. Those solutions are then compared with the official result of the comparison published previously and based on the observations of the metrological institutes and the gravity differences at the different sites as measured by non-metrological institutes. Overall, the absolute gravity meters agree with one another with a standard deviation of3.1 µ Gal. Finally, the results of this comparison are linked to previous ones. We conclude with some important recommendations for future comparisons. [less ▲]

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See detailAccuracy assessment of the two-sample zero-crossing detection in a sinusoidal signal
Svitlov, Sergiy; Rothleitner, Christian UL; Wang, Lijun

in Metrologia (2012), 49(4), 413-424

The accuracy of a two-sample zero-crossing detection method is assessed by analytical uncertainty propagation and is verified in numerical simulations. Approximated expressions are given to evaluate ... [more ▼]

The accuracy of a two-sample zero-crossing detection method is assessed by analytical uncertainty propagation and is verified in numerical simulations. Approximated expressions are given to evaluate uncertainty components due to linear interpolation, quantization, white noise and time jitter. The combined standard uncertainty of a detected zero phase is expressed as a function of the signal frequency, power of external noise and parameters of the digitizer used. The evaluation of the uncertainty of the measurand, derived from several detected zero-crossings, is illustrated with applications in frequency, displacement and free-fall acceleration measurements. The reported results can be used for uncertainty analysis and parameter optimization of a measurement system or a procedure, involving processing of sinusoidal signals. [less ▲]

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See detailOn the evaluation of systematic effects in atom and corner-cube absolute gravimeters
Rothleitner, Christian UL; Svitlov, Sergiy

in Physics Letters A (2012), 376

We show that due to analogy of atom and optical interferometry a perturbed phase propagates identically in atom and corner-cube absolute gravimeters. To evaluate associated systematic effects, we consider ... [more ▼]

We show that due to analogy of atom and optical interferometry a perturbed phase propagates identically in atom and corner-cube absolute gravimeters. To evaluate associated systematic effects, we consider both gravimeters as a linear system in the time domain. This formalism is based on a weighting function earlier derived for a corner-cube gravimeter. As an example, we demonstrate that the corrections for a linear change of gravity are essentially the same for both gravimeters. Application of a common formalism to analyse various systematic effects could reveal possible source of disagreement in comparisons of atom and corner-cube absolute gravimeters. [less ▲]

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See detailUpdating the Precise Gravity Network at the BIPM
Jiang, Z.; Arias, E. F.; Tisserand, L. et al

in Geodesy for Planet Earth (2012)

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See detailRelative Gravity Measurement Campaign during the 8th International Comparison of Absolute Gravimeters (2009)
Jiang, Z.; Pálinkáš, V.; Francis, Olivier UL et al

in Metrologia (2012), 49(1), 95

The 8th International Comparison of Absolute Gravimeters (ICAG-2009) and the associated Relative Gravity Campaign (RGC2009) took place at the Bureau International des Poids et Mesures (BIPM) between July ... [more ▼]

The 8th International Comparison of Absolute Gravimeters (ICAG-2009) and the associated Relative Gravity Campaign (RGC2009) took place at the Bureau International des Poids et Mesures (BIPM) between July and October 2009. Altogether 24 institutes with 22 absolute gravimeters and 9 relative gravimeters participated in the ICAG/RGC campaign. Accurate absolute and relative gravity measurements as well as precision levelling measurements were performed on the micro-gravity 3D-grid at the BIPM. The 2009 comparison was the first to be organized as a Comité International des Poids et Mesures (CIPM) metrological Key Comparison under the CIPM MRA (Mutual Recognition Arrangement), which means that the result will be officially recognized by the governmental organizations responsible. As a consequence, the relative gravimeters employed were carefully selected and the measurement schedules were rigorously enforced compared with earlier campaigns. Thus the quality of the RGC2009 and the determination of the BIPM local gravity network were improved. After 30 years and eight successive ICAGs, the BIPM has decided to transfer its role to the national metrological institutes, although the CIPM will continue to organize the key comparison as ICAGs. The background to the RGC2009, and the organization, data processing and final results of the gravity and vertical gravity gradients, are presented in this paper. This report is more detailed than previous final reports of the RGCs. [less ▲]

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See detailSecond-order Doppler-shift corrections in free-fall absolute gravimeters
Rothleitner, Christian UL; Francis, Olivier UL

in Metrologia (2011), 48(3), 187-195

In a free-fall absolute gravimeter usually a Michelson type interferometer is employed to track the trajectory of a freely falling retroreflector. The accelerated motion of the retroreflector produces a ... [more ▼]

In a free-fall absolute gravimeter usually a Michelson type interferometer is employed to track the trajectory of a freely falling retroreflector. The accelerated motion of the retroreflector produces a Doppler-shift in the laser wavelength. From the interference signal (beat signal) of the Doppler-shifted and the reference electromagnetic waves the relative motion of the freely falling retroreflector with respect to an inertial reference retroreflector is reconstructed. Considerations of second-order Doppler-shift terms lead to a correction in the acceleration due to gravity of several microgals (1 µGal = 10 nm s −2 ). This correction is commonly called speed of light correction . To date different correction formulae have been proposed, which differ by several microgals. In this paper we review several previous publications and show the reasons for the different results. [less ▲]

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See detailPreliminary results of the BIPM Relative Gravity Measurement Campaign during the 8th International Comparison of Absolute Gravimeters (2009)
Jiang, Zihang; Tisserand, L.; Kessler-Schulz, K. U. et al

in Peshekhonov, Vladimir (Ed.) Proceedings of the IAG Symposium on Terrestrial Gravimetry: Static and Mobile Measurements (2011)

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See detailOn the influence of the rotation of a corner cube reflector in absolute gravimetry
Rothleitner, Christian UL; Francis, Olivier UL

in Metrologia (2010), 47(5), 567

Test masses of absolute gravimeters contain prism or hollow retroreflectors. A rotation of such a retroreflector during free-fall can cause a bias in the measured g -value. In particular, prism ... [more ▼]

Test masses of absolute gravimeters contain prism or hollow retroreflectors. A rotation of such a retroreflector during free-fall can cause a bias in the measured g -value. In particular, prism retroreflectors produce phase shifts, which cannot be eliminated. Such an error is small if the rotation occurs about the optical centre of the retroreflector; however, under certain initial conditions the error can reach the microgal level. The contribution from these rotation-induced accelerations is calculated. [less ▲]

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See detailImprovements of the MPG-2 transportable absolute ballistic gravimeter
Hu, H.; Svitlov, S.; Rothleitner, Christian UL et al

in Metrologia (2010), 47

The MPG-2 (Max-Planck-Gravimeter) is a transportable absolute gravimeter built on a classical free-fall scheme to measure the local gravity value. With significant improvements and further investigations ... [more ▼]

The MPG-2 (Max-Planck-Gravimeter) is a transportable absolute gravimeter built on a classical free-fall scheme to measure the local gravity value. With significant improvements and further investigations in recent years, the standard deviation of the mean for a typical measurement over 12 h to 24 h is 1.0 µGal to 3.0 µGal (1 µGal = 10 −8  m s −2 ), and the combined standard uncertainty is estimated to be less than 10 µGal. The major improvements include the new interferometer design and alignment, longer drop length, reduced recoil effects and demagnetization of the falling body. The revised uncertainty budget and new measurement results of MPG-2 are reported. The results of observations at the reference gravity station Bad Homburg confirmed the revised uncertainty budget. [less ▲]

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See detailFirst Experience with the Transportable MPG-2 Absolute Gravimeter
Svitlov, S.; Rothleitner, Christian UL; Wang, L. J.

in Mertikas, Stelios P. (Ed.) Gravity, Geoid and Earth Observation (2010)

We report on design details and first results obtained with the transportable absolute gravimeter MPG-2 (“Max-Planck-Gravimeter”). It is developed as an evolution of the stationary device MPG-1, completed ... [more ▼]

We report on design details and first results obtained with the transportable absolute gravimeter MPG-2 (“Max-Planck-Gravimeter”). It is developed as an evolution of the stationary device MPG-1, completed in 2007. The MPG-2 is built on a common scheme where the position of a freely falling object is monitored. The setup consists of a ballistic block, an interferometer and the electronics. Free fall drops can be repeated every 10 s with the standard deviation close to 30 μgal. A one-day gravity observation gives a result with a standard deviation of the mean of less than 5 μgal. A prototype of the MPG-2 took part in the ECAG-2007. New measurements at the reference gravity station “Bad Homburg”, Germany confirmed the declared combined standard uncertainty of 50 μgal. [less ▲]

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See detailComparison of three digital fringe signal processing methods in a ballistic free-fall absolute gravimeter
Svitlov, S.; Masłyk, P.; Rothleitner, Christian UL et al

in Metrologia (2010), 47(6), 677

This paper reports results of comparison of three digital fringe signal processing methods implemented in the same free-fall absolute gravimeter. A two-sample zero-crossing method, a windowed second ... [more ▼]

This paper reports results of comparison of three digital fringe signal processing methods implemented in the same free-fall absolute gravimeter. A two-sample zero-crossing method, a windowed second-difference method and a method of non-linear least-squares adjustment on the undersampled fringe signal are compared in numerical simulations, hardware tests and actual measurements with the MPG-2 absolute gravimeter, developed at the Max Planck Institute for the Science of Light, Germany. The two-sample zero-crossing method realizes data location schemes that are both equally spaced in distance and equally spaced in time (EST) along the free-fall trajectory. The windowed second-difference method and the method of non-linear least-squares adjustment with complex heterodyne demodulation operate with the EST data. Results of the comparison verify an agreement of the three methods within one part in 10 9 of the measured gravity value, provided a common data location scheme is considered. [less ▲]

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See detailResults of the European Comparison of Absolute Gravimeters in Walferdange (Luxembourg) of November 2007
Francis, Olivier UL; van Dam, Tonie UL; Germak, A. et al

in Gravity, Geoid and Earth Observation (2010)

The second international comparison of absolute gravimeters was held in Walferdange, Grand Duchy of Luxembourg, in November 2007, in which twenty absolute gravimeters took part. A short description of the ... [more ▼]

The second international comparison of absolute gravimeters was held in Walferdange, Grand Duchy of Luxembourg, in November 2007, in which twenty absolute gravimeters took part. A short description of the data processing and adjustments will be presented here and will be followed by the presentation of the results. Two different methods were applied to estimate the relative offsets between the gravimeters. We show that the results are equivalent as the uncertainties of both adjustments overlap. The absolute gravity meters agree with one another with a standard deviation of 2 μgal (1 gal = 1 cm/s2). [less ▲]

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See detailDevelopment of new free-fall absolute gravimeters
Rothleitner, Christian UL; Svitlov, S.; Mérimèche, H. et al

in Metrologia (2009), 46(3), 283-297

The design and first results of two free-fall absolute gravimeters are reported: a stationary gravimeter is designed and can be used as a reference system and a portable gravimeter is aimed at field ... [more ▼]

The design and first results of two free-fall absolute gravimeters are reported: a stationary gravimeter is designed and can be used as a reference system and a portable gravimeter is aimed at field measurements. The determination of the acceleration due to gravity is done interferometrically in both instruments. The whole fringe signal is digitized by a high-speed analogue-to-digital converter, which is locked to a rubidium frequency standard. This fringe recording and processing is novel as compared with commercial free-fall gravimeters, which use an electronic zero-crossing discrimination. Advantages such as the application of a zero-phase-shifting digital filter to the digitized data are depicted. The portable gravimeter's mechanics deviate from the conventional type. Springs are used to accelerate and decelerate the carriage supporting the falling object. A detailed uncertainty budget is given for both gravimeters. The combined standard uncertainty for the portable and for the stationary gravimeter is estimated at 38.8 µGal and 16.6 µGal, respectively. The corresponding statistical uncertainties are 1.6 µGal (over one day of measurement) and 0.6 µGal (over one month of measurement). The different designs and dimensions of the new free-fall gravimeters can help to reveal unknown or so far underestimated systematic effects. The assessments of the uncertainties due to seismic noise and shock vibrations, and electronic phase shifts give validity to this assumption. [less ▲]

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