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Valter Ferrero - One of the best experts on this subject based on the ideXlab platform.
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free space optical system performance for a gaussian beam propagating through non kolmogorov weak turbulence
IEEE Transactions on Antennas and Propagation, 2009Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:Atmospheric turbulence has been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular in portions of the troposphere and stratosphere. It is known that free space laser system performance is limited by atmospheric turbulence. In this paper we use a non-Kolmogorov power spectrum which uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Using this spectrum in weak turbulence, we carry out, for a Gaussian beam propagating along a horizontal path, analysis of long term beam spread, scintillation, probability of fade, mean signal to noise ratio and mean bit error rate as variation of the spectrum exponent. Our theoretical results show that for alpha values lower than alpha = 11/3, but not for alpha close to alpha = 3, there is a remarkable increase of scintillation and consequently a major penalty on the system performance. However when alpha assumes values close to alpha = 3 or for alpha values higher than alpha = 11/3 scintillation decreases leading to an improvement on the system performance.
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free space optical system performance for laser beam propagation through non kolmogorov turbulence
Optical Engineering, 2008Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:It is well know that free-space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately, several experiments have been reported recently that show that the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. We present a non-Kolmogorov power spectrum that uses a generalized exponent instead of constant standard exponent value 11/3, and a generalized Amplitude Factor instead of constant value 0.033. Using this new spectrum in weak turbulence, we carry out, for a horizontal path, an analysis of long-term beam spread, scintillation index, probability of fade, mean signal-to-noise ratio (SNR), and mean bit error rate (BER) as variation of the spectrum exponent. Our theoretical results show that for alpha values lower than =11/3, but not for alpha close to =3, there is a remarkable increase of scintillation and consequently a major penalty on the system performance. However, when alpha assumes a value close to =3 or for alpha values higher than =11/3, scintillation decreases, leading to an improvement on the system performance.
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scintillation index of optical plane wave propagating through non kolmogorov moderate strong turbulence
Remote Sensing, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:An optical plane wave propagating through atmospheric turbulence is affected by irradiance fluctuations known as scintillation. The scintillation index of an optical wave in strong turbulence can be analyzed by extended Rytov theory, which uses filter functions to eliminate the effect of cell turbulence sizes that do not contribute to scintillation, and it already has been calculated by Kolmogorov's power spectral density model. However several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric turbulence properly. In this paper, for a horizontal path, we use extended Rytov theory to carry out plane wave scintillation index analysis in non Kolmogorov strong turbulence. We do it using a non Kolmogorov power spectrum which uses a generalized exponent Factor and a generalized Amplitude Factor. Although our final expressions for the scintillation have been obtained by extended Rytov theory, which is necessary to adopt in strong turbulence conditions, they reduce to the proper results also in weak turbulence.
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Free space optical system performance for laser beam propagation through non Kolmogorov turbulence for uplink and downlink paths
Atmospheric Optics: Models Measurements and Target-in-the-Loop Propagation, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:It is well known that free space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. In this paper, using a non Kolmogorov spectrum and following same procedure already used for horizontal path analysis, we extend free space optical system performance analysis to uplink and downlink paths. Our non Kolmogorov spectrum uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Therefore, in non-Kolmogorov weak turbulence, we carry out, for a uplink and a downlink paths, analysis of Long Term Beam Spread, Scintillation index, Probability of fade, mean SNR and mean BER as variation of the spectrum exponent.
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angle of arrival fluctuations for free space laser beam propagation through non kolmogorov turbulence
SPIE: Defense & Security Symposium Atmospheric Propagation IV, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:Atmospheric turbulence induces significant variation on the angle-of-arrival of laser beams used in free space laser communication. Angle-of-arrival fluctuations of an optical wave in the plane of the receiver aperture can be described in terms of the phase structure function that already has been calculated by Kolmogorov's power spectral density model. Unfortunately several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly. In this paper, for horizontal path and weak turbulence, we carry out analysis of angle-of-arrival fluctuations using a non Kolmogorov power spectrum which uses a generalized exponent Factor instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Also our non Kolmogorov spectrum includes both inner scale and outer scale effects.
Italo Toselli - One of the best experts on this subject based on the ideXlab platform.
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free space optical system performance for a gaussian beam propagating through non kolmogorov weak turbulence
IEEE Transactions on Antennas and Propagation, 2009Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:Atmospheric turbulence has been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular in portions of the troposphere and stratosphere. It is known that free space laser system performance is limited by atmospheric turbulence. In this paper we use a non-Kolmogorov power spectrum which uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Using this spectrum in weak turbulence, we carry out, for a Gaussian beam propagating along a horizontal path, analysis of long term beam spread, scintillation, probability of fade, mean signal to noise ratio and mean bit error rate as variation of the spectrum exponent. Our theoretical results show that for alpha values lower than alpha = 11/3, but not for alpha close to alpha = 3, there is a remarkable increase of scintillation and consequently a major penalty on the system performance. However when alpha assumes values close to alpha = 3 or for alpha values higher than alpha = 11/3 scintillation decreases leading to an improvement on the system performance.
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free space optical system performance for laser beam propagation through non kolmogorov turbulence
Optical Engineering, 2008Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:It is well know that free-space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately, several experiments have been reported recently that show that the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. We present a non-Kolmogorov power spectrum that uses a generalized exponent instead of constant standard exponent value 11/3, and a generalized Amplitude Factor instead of constant value 0.033. Using this new spectrum in weak turbulence, we carry out, for a horizontal path, an analysis of long-term beam spread, scintillation index, probability of fade, mean signal-to-noise ratio (SNR), and mean bit error rate (BER) as variation of the spectrum exponent. Our theoretical results show that for alpha values lower than =11/3, but not for alpha close to =3, there is a remarkable increase of scintillation and consequently a major penalty on the system performance. However, when alpha assumes a value close to =3 or for alpha values higher than =11/3, scintillation decreases, leading to an improvement on the system performance.
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scintillation index of optical plane wave propagating through non kolmogorov moderate strong turbulence
Remote Sensing, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:An optical plane wave propagating through atmospheric turbulence is affected by irradiance fluctuations known as scintillation. The scintillation index of an optical wave in strong turbulence can be analyzed by extended Rytov theory, which uses filter functions to eliminate the effect of cell turbulence sizes that do not contribute to scintillation, and it already has been calculated by Kolmogorov's power spectral density model. However several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric turbulence properly. In this paper, for a horizontal path, we use extended Rytov theory to carry out plane wave scintillation index analysis in non Kolmogorov strong turbulence. We do it using a non Kolmogorov power spectrum which uses a generalized exponent Factor and a generalized Amplitude Factor. Although our final expressions for the scintillation have been obtained by extended Rytov theory, which is necessary to adopt in strong turbulence conditions, they reduce to the proper results also in weak turbulence.
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Free space optical system performance for laser beam propagation through non Kolmogorov turbulence for uplink and downlink paths
Atmospheric Optics: Models Measurements and Target-in-the-Loop Propagation, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:It is well known that free space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. In this paper, using a non Kolmogorov spectrum and following same procedure already used for horizontal path analysis, we extend free space optical system performance analysis to uplink and downlink paths. Our non Kolmogorov spectrum uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Therefore, in non-Kolmogorov weak turbulence, we carry out, for a uplink and a downlink paths, analysis of Long Term Beam Spread, Scintillation index, Probability of fade, mean SNR and mean BER as variation of the spectrum exponent.
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angle of arrival fluctuations for free space laser beam propagation through non kolmogorov turbulence
SPIE: Defense & Security Symposium Atmospheric Propagation IV, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:Atmospheric turbulence induces significant variation on the angle-of-arrival of laser beams used in free space laser communication. Angle-of-arrival fluctuations of an optical wave in the plane of the receiver aperture can be described in terms of the phase structure function that already has been calculated by Kolmogorov's power spectral density model. Unfortunately several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly. In this paper, for horizontal path and weak turbulence, we carry out analysis of angle-of-arrival fluctuations using a non Kolmogorov power spectrum which uses a generalized exponent Factor instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Also our non Kolmogorov spectrum includes both inner scale and outer scale effects.
Ronald L Phillips - One of the best experts on this subject based on the ideXlab platform.
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free space optical system performance for a gaussian beam propagating through non kolmogorov weak turbulence
IEEE Transactions on Antennas and Propagation, 2009Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:Atmospheric turbulence has been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular in portions of the troposphere and stratosphere. It is known that free space laser system performance is limited by atmospheric turbulence. In this paper we use a non-Kolmogorov power spectrum which uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Using this spectrum in weak turbulence, we carry out, for a Gaussian beam propagating along a horizontal path, analysis of long term beam spread, scintillation, probability of fade, mean signal to noise ratio and mean bit error rate as variation of the spectrum exponent. Our theoretical results show that for alpha values lower than alpha = 11/3, but not for alpha close to alpha = 3, there is a remarkable increase of scintillation and consequently a major penalty on the system performance. However when alpha assumes values close to alpha = 3 or for alpha values higher than alpha = 11/3 scintillation decreases leading to an improvement on the system performance.
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free space optical system performance for laser beam propagation through non kolmogorov turbulence
Optical Engineering, 2008Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:It is well know that free-space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately, several experiments have been reported recently that show that the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. We present a non-Kolmogorov power spectrum that uses a generalized exponent instead of constant standard exponent value 11/3, and a generalized Amplitude Factor instead of constant value 0.033. Using this new spectrum in weak turbulence, we carry out, for a horizontal path, an analysis of long-term beam spread, scintillation index, probability of fade, mean signal-to-noise ratio (SNR), and mean bit error rate (BER) as variation of the spectrum exponent. Our theoretical results show that for alpha values lower than =11/3, but not for alpha close to =3, there is a remarkable increase of scintillation and consequently a major penalty on the system performance. However, when alpha assumes a value close to =3 or for alpha values higher than =11/3, scintillation decreases, leading to an improvement on the system performance.
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scintillation index of optical plane wave propagating through non kolmogorov moderate strong turbulence
Remote Sensing, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:An optical plane wave propagating through atmospheric turbulence is affected by irradiance fluctuations known as scintillation. The scintillation index of an optical wave in strong turbulence can be analyzed by extended Rytov theory, which uses filter functions to eliminate the effect of cell turbulence sizes that do not contribute to scintillation, and it already has been calculated by Kolmogorov's power spectral density model. However several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric turbulence properly. In this paper, for a horizontal path, we use extended Rytov theory to carry out plane wave scintillation index analysis in non Kolmogorov strong turbulence. We do it using a non Kolmogorov power spectrum which uses a generalized exponent Factor and a generalized Amplitude Factor. Although our final expressions for the scintillation have been obtained by extended Rytov theory, which is necessary to adopt in strong turbulence conditions, they reduce to the proper results also in weak turbulence.
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Free space optical system performance for laser beam propagation through non Kolmogorov turbulence for uplink and downlink paths
Atmospheric Optics: Models Measurements and Target-in-the-Loop Propagation, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:It is well known that free space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. In this paper, using a non Kolmogorov spectrum and following same procedure already used for horizontal path analysis, we extend free space optical system performance analysis to uplink and downlink paths. Our non Kolmogorov spectrum uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Therefore, in non-Kolmogorov weak turbulence, we carry out, for a uplink and a downlink paths, analysis of Long Term Beam Spread, Scintillation index, Probability of fade, mean SNR and mean BER as variation of the spectrum exponent.
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angle of arrival fluctuations for free space laser beam propagation through non kolmogorov turbulence
SPIE: Defense & Security Symposium Atmospheric Propagation IV, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:Atmospheric turbulence induces significant variation on the angle-of-arrival of laser beams used in free space laser communication. Angle-of-arrival fluctuations of an optical wave in the plane of the receiver aperture can be described in terms of the phase structure function that already has been calculated by Kolmogorov's power spectral density model. Unfortunately several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly. In this paper, for horizontal path and weak turbulence, we carry out analysis of angle-of-arrival fluctuations using a non Kolmogorov power spectrum which uses a generalized exponent Factor instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Also our non Kolmogorov spectrum includes both inner scale and outer scale effects.
Larry C Andrews - One of the best experts on this subject based on the ideXlab platform.
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free space optical system performance for a gaussian beam propagating through non kolmogorov weak turbulence
IEEE Transactions on Antennas and Propagation, 2009Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:Atmospheric turbulence has been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular in portions of the troposphere and stratosphere. It is known that free space laser system performance is limited by atmospheric turbulence. In this paper we use a non-Kolmogorov power spectrum which uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Using this spectrum in weak turbulence, we carry out, for a Gaussian beam propagating along a horizontal path, analysis of long term beam spread, scintillation, probability of fade, mean signal to noise ratio and mean bit error rate as variation of the spectrum exponent. Our theoretical results show that for alpha values lower than alpha = 11/3, but not for alpha close to alpha = 3, there is a remarkable increase of scintillation and consequently a major penalty on the system performance. However when alpha assumes values close to alpha = 3 or for alpha values higher than alpha = 11/3 scintillation decreases leading to an improvement on the system performance.
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free space optical system performance for laser beam propagation through non kolmogorov turbulence
Optical Engineering, 2008Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:It is well know that free-space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately, several experiments have been reported recently that show that the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. We present a non-Kolmogorov power spectrum that uses a generalized exponent instead of constant standard exponent value 11/3, and a generalized Amplitude Factor instead of constant value 0.033. Using this new spectrum in weak turbulence, we carry out, for a horizontal path, an analysis of long-term beam spread, scintillation index, probability of fade, mean signal-to-noise ratio (SNR), and mean bit error rate (BER) as variation of the spectrum exponent. Our theoretical results show that for alpha values lower than =11/3, but not for alpha close to =3, there is a remarkable increase of scintillation and consequently a major penalty on the system performance. However, when alpha assumes a value close to =3 or for alpha values higher than =11/3, scintillation decreases, leading to an improvement on the system performance.
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scintillation index of optical plane wave propagating through non kolmogorov moderate strong turbulence
Remote Sensing, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:An optical plane wave propagating through atmospheric turbulence is affected by irradiance fluctuations known as scintillation. The scintillation index of an optical wave in strong turbulence can be analyzed by extended Rytov theory, which uses filter functions to eliminate the effect of cell turbulence sizes that do not contribute to scintillation, and it already has been calculated by Kolmogorov's power spectral density model. However several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric turbulence properly. In this paper, for a horizontal path, we use extended Rytov theory to carry out plane wave scintillation index analysis in non Kolmogorov strong turbulence. We do it using a non Kolmogorov power spectrum which uses a generalized exponent Factor and a generalized Amplitude Factor. Although our final expressions for the scintillation have been obtained by extended Rytov theory, which is necessary to adopt in strong turbulence conditions, they reduce to the proper results also in weak turbulence.
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Free space optical system performance for laser beam propagation through non Kolmogorov turbulence for uplink and downlink paths
Atmospheric Optics: Models Measurements and Target-in-the-Loop Propagation, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:It is well known that free space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. In this paper, using a non Kolmogorov spectrum and following same procedure already used for horizontal path analysis, we extend free space optical system performance analysis to uplink and downlink paths. Our non Kolmogorov spectrum uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Therefore, in non-Kolmogorov weak turbulence, we carry out, for a uplink and a downlink paths, analysis of Long Term Beam Spread, Scintillation index, Probability of fade, mean SNR and mean BER as variation of the spectrum exponent.
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angle of arrival fluctuations for free space laser beam propagation through non kolmogorov turbulence
SPIE: Defense & Security Symposium Atmospheric Propagation IV, 2007Co-Authors: Italo Toselli, Larry C Andrews, Ronald L Phillips, Valter FerreroAbstract:Atmospheric turbulence induces significant variation on the angle-of-arrival of laser beams used in free space laser communication. Angle-of-arrival fluctuations of an optical wave in the plane of the receiver aperture can be described in terms of the phase structure function that already has been calculated by Kolmogorov's power spectral density model. Unfortunately several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly. In this paper, for horizontal path and weak turbulence, we carry out analysis of angle-of-arrival fluctuations using a non Kolmogorov power spectrum which uses a generalized exponent Factor instead of constant standard exponent value 11/3 and a generalized Amplitude Factor instead of constant value 0.033. Also our non Kolmogorov spectrum includes both inner scale and outer scale effects.
Heping Sun - One of the best experts on this subject based on the ideXlab platform.
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detection of free core nutation resonance variation in earth tide from global superconducting gravimeter observations
Earth Planets and Space, 2018Co-Authors: Xiaoming Cui, Heping Sun, Jiangcun Zhou, Xiaodong ChenAbstract:In order to verify the time variability of free core nutation (FCN) period, global superconducting gravimeter (SG) observations were analyzed based on synthetic test data. The gravity data series were synthesized to check the detectability of resonance variation caused by FCN period change. The tests indicate that the discrepancy between the FCN periods determined by SG and VLBI observations is caused by the high correlation between the FCN parameter and the Amplitude Factor of the ψ1 wave. The K1 wave is more sensitive to the FCN period change than other diurnal waves. The limit of the standard deviation of the K1 wave is found for more precisely observing the FCN period change. Tidal parameters of diurnal waves estimated from long series of 20 global SG stations were analyzed. A common variation trend is found in the Amplitude Factor of both K1 and ψ1 waves in all 8 stations above the limit, which indicates the FCN period may be not so stable in time. Furthermore, the variation in the K1 and ψ1 waves constrains the FCN period change to between 2.5 and 4 sidereal days, which also agrees with the possible variation from the current VLBI and SG observations.
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loading effect of a self consistent equilibrium ocean pole tide on the gravimetric parameters of the gravity pole tides at superconducting gravimeter stations
Journal of Geodynamics, 2008Co-Authors: Xiaodong Chen, B Ducarme, Heping SunAbstract:Abstract The gravimetric parameters of the gravity pole tide are the Amplitude Factor δ , which is the ratio of gravity variations induced by polar motion for a real Earth to variations computed for a rigid one, and the phase difference κ between the observed and the rigid gravity pole tide. They can be estimated from the records of superconducting gravimeters (SGs). However, they are affected by the loading effect of the ocean pole tide. Recent results from TOPEX/Poseidon (TP) altimeter confirm that the ocean pole tide has a self-consistent equilibrium response. Accordingly, we calculate the gravity loading effects as well as their influence on the gravimetric parameters of gravity pole tide at all the 26 SG stations in the world on the assumption of a self-consistent equilibrium ocean pole tide model. The gravity loading effect is evaluated between 1 January 1997 and 31 December 2006. Numerical results show that the Amplitude of the gravity loading effect reaches 10 −9 m s −2 , which is larger than the accuracy (10 −10 m s −2 ) of a SG. The gravimetric Factor δ is 1% larger at all SG stations. Then, the contribution of a self-consistent ocean pole tide to the pole tide gravimetric parameters cannot be ignored as it exceeds the current accuracy of the estimation of the pole tide gravity Factors. For the nine stations studied in Ducarme et al. [Ducarme, B., Venedikov, A.P., Arnoso, J., et al., 2006. Global analysis of the GGP superconducting gravimeters network for the estimation of the pole tide gravimetric Amplitude Factor. J. Geodyn. 41, 334–344.], the mean of the modeled tidal Factors δ m = 1.1813 agrees very well with the result of a global analysis δ CH = 1.1816 ± 0.0047 in that paper. On the other hand, the modeled phase difference κ m varies from −0.273° to 0.351°. Comparing to the two main periods of the gravity pole tide, annual period and Chandler period, κ m is too small to be considered. Therefore, The computed time difference κ L induced by a self-consistent ocean pole tide produces a negligible effect on κ m . It confirms the results of Ducarme et al., 2006, where no convincing time difference was found in the SG records.
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global analysis of the ggp superconducting gravimeters network for the estimation of the pole tide gravimetric Amplitude Factor
Journal of Geodynamics, 2006Co-Authors: B Ducarme, Xiaodong Chen, Heping Sun, A P Venedikov, Jose Arnoso, Ricardo VieiraAbstract:The tidal records of superconducting gravimeters (SG) in nine stations are analyzed, in order to determine the gravity variation due to the polar motion. In a first step the tidal constituents are estimated and subtracted from the original data, together with the estimated atmospheric pressure effects, by the computer program VAV. The data so obtained are submitted to a regression analysis by a specially developed program POLAR, whose aim is the estimation of the gravimetric Amplitude Factor δCH of the pole tide and its time shift with respect to the theoretical gravity signal due to the polar motion. The procedure includes an optimization of various parameters of the regression model, as well as a detection and elimination of the anomalous portions of the records. The analysis has been first applied separately on each one of the nine series. Most of the stations provided a δCH Factor between 1.17 and 1.19 with mean square deviation close to 1%. Further all series have been submitted to a global analysis through which a common value of the δCH Factor has been estimated. No significant global time shift has been found. The global adjustment values are δCH = 1.1816 ± 0.0047 or 1.1797 ± 0.0047, depending on the way the time shift is introduced, while the simple arithmetic mean of the stations is 1.1788 ± 0.0040. This result differs considerably from the values predicted by Earth response models, e.g. from δ = 1.158 obtained for the annual period through the non-hydrostatic anelastic model, usually called DDW99. The discrepancy is due to the indirect effects of the ocean tides. A preliminary correction scheme based on an equilibrium ocean pole tide is indeed reducing the globally adjusted δCH Factor to 1.1612 or 1.1593 and the arithmetic mean to 1.1605.
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a study of gravity variations caused by polar motion using superconducting gravimeter data from the ggp network
Journal of Geodesy, 2004Co-Authors: Heping Sun, Xin YangAbstract:Long-term continuous gravity observations, recorded at five superconducting gravimeter (SG) sta- tions in the Global Geodynamic Project (GGP) net- work, as well as data on orientation variations in the Earth's rotation axis (i.e. polar motion), have been used to investigate the characteristics of gravity variations on the Earth's surface caused by polar motion. All the SG gravity data sets were pre-processed using identical techniques to remove the luni-solar gravity tides, the long-term trends of the instrumental drift, and the effects of atmospheric pressure. The analysis indicates that the spectral peaks, related to the Chandler and annual wobbles, were identified in both the power and product spectral density estimates. The magnitude of gravity variations, as well as the gravimetric Amplitude Factor associated with the Chandler wobble, changed significantly at different SG stations and during different observation periods. However, when all the SG obser- vations at these five sites were combined, the gravimetric parameters of the Chandler wobble were retrieved accurately: 1.1613 ± 0.0737 for the Amplitude Factor and )1� .30 ± 1� .33 for the phase difference. The value of the estimated Amplitude Factor is in agreement with that predicted theoretically for the zonal tides of an elastic Earth model.