Based on the nearly diurnal resonance in the tidal gravity observations, the temporal variations in period of the Earth＇s free core nutation （FCN） are investigated by using the tidal gravity observations of 18-year...Based on the nearly diurnal resonance in the tidal gravity observations, the temporal variations in period of the Earth＇s free core nutation （FCN） are investigated by using the tidal gravity observations of 18-year duration recorded continu- ously with a superconducting gravimeter （SG） at Brussels. The effects of the global oceanic tide loading and local barometric pressure on the SG observations have been removed by using eleven high-precision global digital models of oceanic tides and barometric pressure measurements recorded simultaneously at the same site. The results indicate that there exist decade-scale variations in the FCN period. The results should be further confirmed by the measurements using other space-based geodetic techniques （such as the very long baseline interferometry） and the SG observations from globally distributed stations.展开更多
Spatial precession is a special micro-motion of the spinning-directional target, and the micro-Doppler signature of the cone-shaped target with precession is studied. The micro-motion model of precession is built firs...Spatial precession is a special micro-motion of the spinning-directional target, and the micro-Doppler signature of the cone-shaped target with precession is studied. The micro-motion model of precession is built first, and then the micro-Doppler model is developed based on the proposed concept of micro-motion ma- trix, by which the theoretical formula of micro-Doppler signature of precession is derived. In order to further approach to the actual case, the occlusion effect is firstly considered in micro-Doppler, and the simulated result with occlusion effect is well in accordance with the measured result in microwave anechoic chamber, which suggests that the micro-motion model and micro-Doppler model of precession are both valid.展开更多
The Free Core Nutation(FCN)is a rotational mode caused by non-alignment of the rotation axis of the core and of the mantle.Its period observed by VLBI and superconducting gravimetry is around 430 sidereal days(Sd)with...The Free Core Nutation(FCN)is a rotational mode caused by non-alignment of the rotation axis of the core and of the mantle.Its period observed by VLBI and superconducting gravimetry is around 430 sidereal days(Sd)with precision of better than 1 Sd,while its“theoretical”period calculated by traditional approaches and a given Earth model ranges from 450 to 470 Sd.Their gap of about 30 Sd is significant compared with its observation precision.We propose a spectral element method to compute the period of FCN and obtain a period of 434 Sd which is very close to the observed value.展开更多
A numerical solution to the Earth＇s precession in a relativistic framework for a long time span is presented here. We obtain the motion of the solar system in the Barycentric Celestial Reference System by numerical i...A numerical solution to the Earth＇s precession in a relativistic framework for a long time span is presented here. We obtain the motion of the solar system in the Barycentric Celestial Reference System by numerical integration with a symplectic in- tegrator. Special Newtonian corrections accounting for tidal dissipation are included in the force model. The part representing Earth＇s rotation is calculated in the Geocentric Celestial Reference System by integrating the post-Newtonian equations of motion published by Klioner et al. All the main relativistic effects are included following Klioner et al. In particular, we consider several relativistic reference systems with cor- responding time scales, scaled constants and parameters. Approximate expressions for Earth＇s precession in the interval ~1 Myr around J2000.0 are provided. In the interval 4-2000 years around J2000.0, the difference compared to the P03 precession theory is only several arcseconds and the results are consistent with other long-term precession theories.展开更多
Relativists have exposed various precessions and developed ingenious experiments to verify those phenomena with extreme precisions. The Gravity Probe B mission was designed to study the precessions of the gyroscopes r...Relativists have exposed various precessions and developed ingenious experiments to verify those phenomena with extreme precisions. The Gravity Probe B mission was designed to study the precessions of the gyroscopes rotating round the Earth in a nearly circular near-Earth polar orbit to demonstrate the geodetic effect and the Lense-Thirring effect as predicted by the general relativity theory. In this paper, we show in a very simple and novel analysis that the precession of the perihelion of Mercury, the Thomas precession, and the precession data （on the de Sitter and Lense-Thirring precessions） collected from the Gravity Probe B mission could easily be explained from classical physics, too.展开更多
基金supported by the Key Project of the Knowledge Innovation of Chinese Academy of Sciences (Grant No. KZCX2-YW-133, KZCX2-YW-Q08-2)National Natural Science Foun-dation of China (Grant No. 40874038 and 40730316)
文摘Based on the nearly diurnal resonance in the tidal gravity observations, the temporal variations in period of the Earth＇s free core nutation （FCN） are investigated by using the tidal gravity observations of 18-year duration recorded continu- ously with a superconducting gravimeter （SG） at Brussels. The effects of the global oceanic tide loading and local barometric pressure on the SG observations have been removed by using eleven high-precision global digital models of oceanic tides and barometric pressure measurements recorded simultaneously at the same site. The results indicate that there exist decade-scale variations in the FCN period. The results should be further confirmed by the measurements using other space-based geodetic techniques （such as the very long baseline interferometry） and the SG observations from globally distributed stations.
文摘Spatial precession is a special micro-motion of the spinning-directional target, and the micro-Doppler signature of the cone-shaped target with precession is studied. The micro-motion model of precession is built first, and then the micro-Doppler model is developed based on the proposed concept of micro-motion ma- trix, by which the theoretical formula of micro-Doppler signature of precession is derived. In order to further approach to the actual case, the occlusion effect is firstly considered in micro-Doppler, and the simulated result with occlusion effect is well in accordance with the measured result in microwave anechoic chamber, which suggests that the micro-motion model and micro-Doppler model of precession are both valid.
基金the National Natural Science Foundation of China(11973072/12233010).
文摘The Free Core Nutation(FCN)is a rotational mode caused by non-alignment of the rotation axis of the core and of the mantle.Its period observed by VLBI and superconducting gravimetry is around 430 sidereal days(Sd)with precision of better than 1 Sd,while its“theoretical”period calculated by traditional approaches and a given Earth model ranges from 450 to 470 Sd.Their gap of about 30 Sd is significant compared with its observation precision.We propose a spectral element method to compute the period of FCN and obtain a period of 434 Sd which is very close to the observed value.
基金Supported by the National Natural Science Foundation of China
文摘A numerical solution to the Earth＇s precession in a relativistic framework for a long time span is presented here. We obtain the motion of the solar system in the Barycentric Celestial Reference System by numerical integration with a symplectic in- tegrator. Special Newtonian corrections accounting for tidal dissipation are included in the force model. The part representing Earth＇s rotation is calculated in the Geocentric Celestial Reference System by integrating the post-Newtonian equations of motion published by Klioner et al. All the main relativistic effects are included following Klioner et al. In particular, we consider several relativistic reference systems with cor- responding time scales, scaled constants and parameters. Approximate expressions for Earth＇s precession in the interval ~1 Myr around J2000.0 are provided. In the interval 4-2000 years around J2000.0, the difference compared to the P03 precession theory is only several arcseconds and the results are consistent with other long-term precession theories.
文摘Relativists have exposed various precessions and developed ingenious experiments to verify those phenomena with extreme precisions. The Gravity Probe B mission was designed to study the precessions of the gyroscopes rotating round the Earth in a nearly circular near-Earth polar orbit to demonstrate the geodetic effect and the Lense-Thirring effect as predicted by the general relativity theory. In this paper, we show in a very simple and novel analysis that the precession of the perihelion of Mercury, the Thomas precession, and the precession data （on the de Sitter and Lense-Thirring precessions） collected from the Gravity Probe B mission could easily be explained from classical physics, too.
