在国际甚长基线干涉测量(very long baseline interferometry,VLBI)大地测量与天体测量服务组织协调下,首次利用隶属于VLBI全球观测系统(VLBI global observing system,VGOS)的美国Kokee和德国Wettzell观测站及并置的传统VLBI观测站开...在国际甚长基线干涉测量(very long baseline interferometry,VLBI)大地测量与天体测量服务组织协调下,首次利用隶属于VLBI全球观测系统(VLBI global observing system,VGOS)的美国Kokee和德国Wettzell观测站及并置的传统VLBI观测站开展了世界时(universal time,UT1)联合测量试验,观测数据在上海VLBI中心进行了干涉处理。结果表明,VGOS超宽带观测系统的UT1测量精度约为7μs,并置基线的传统S/X双频系统测量精度约为14μs,VGOS系统的UT1解算结果优于S/X系统。通过试验建立了从相关处理、相关后处理到UT1参数解算的完整数据处理流程,验证了上海VLBI相关处理机的VGOS数据处理能力,为承担国内和国际VGOS观测数据的相关处理任务奠定了基础。展开更多
Zhouqu County in Gansu Province, Northwest China, is typically highly prone to landslides. On July 12, 2018, a landslide blocked the Bailong River near Zhouqu County, posing a serious threat to the life and property o...Zhouqu County in Gansu Province, Northwest China, is typically highly prone to landslides. On July 12, 2018, a landslide blocked the Bailong River near Zhouqu County, posing a serious threat to the life and property of local residents and the safety of infrastructure. Small baseline subset interferometry synthetic aperture radar technology(SBAS-In SAR) was adopted to identify the potential active landslides in the surrounding area of Zhouqu County, using ascending and descending orbit Sentinel-1 satellite images taken from October 2017 to December 2018. The surface deformation areas detected by SBAS-In SAR were verified by optical remote sensing image interpretation and field investigation, and a total of 23 active landslides were identified finally. The deformation characteristics of four typical landslides are analysed in detail using deformation velocity and rainfall data. It is found that the deformation velocity of landslides in this area is mainly affected by rainfall and there is a lag effect. The results can provide a reference for the prevention and control of landslide risk in Zhouqu County.展开更多
The Earth’s Free Core Nutation(FCN) causes Earth tides and forced nutation with frequencies close to the FCN that exhibit resonance effects.High-precision superconducting gravimeter(SG) and very long baseline interfe...The Earth’s Free Core Nutation(FCN) causes Earth tides and forced nutation with frequencies close to the FCN that exhibit resonance effects.High-precision superconducting gravimeter(SG) and very long baseline interferometry(VLBI) provide good observation techniques for detecting the FCN parameters.However,some choices in data processing and solution procedures increase the uncertainty of the FCN parameters.In this study,we analyzed the differences and the effectiveness of weight function and ocean tide corrections in the FCN parameter detection using synthetic data,SG data from thirty-one stations,and the 10 celestial pole offset(CPO) series.The results show that significant discrepancies are caused by different computing options for a single SG station.The stacking method,which results in a variation of0.24-5 sidereal days(SDs) in the FCN period(T) and 10^(3)-10^(4) in the quality factor(Q) due to the selection of the weighting function and the ocean tide model(OTM),can effectively suppress this influence.The statistical analysis results of synthetic data shows that although different weight choices,while adjusting the proportion of diurnal tidal waves involved,do not significantly improve the accuracy of fitted FCN parameters from gravity observations.The study evaluated a series of OTMs using the loading correction efficiency.The fitting of FCN parameters can be improved by selecting the mean of appropriate OTMs based on the evaluation results.Through the estimation of the FCN parameters based on the forced nutation,it was found that the weight function P_(1) is more suitable than others,and different CPO series(after 2009) resulted in a difference of 0.4 SDs in the T and of 103 in the Q.We estimated the FCN parameters for SG(T=430.4±1.5 SDs and Q=1.52×10^(4)±2.5×10^(3)) and for VLBI(T=429.8±0.7 SDs,Q=1.88×10^(4)±2.1×10^(3)).展开更多
The seven co-located sites of the Crustal Movement Observation Network of China（CMONOC） in Shanghai, Wuhan, Kunming, Beijing, Xi＇an, Changchun, and Urumqi are equipped with Global Navigation Satellite System（GNSS...The seven co-located sites of the Crustal Movement Observation Network of China（CMONOC） in Shanghai, Wuhan, Kunming, Beijing, Xi＇an, Changchun, and Urumqi are equipped with Global Navigation Satellite System（GNSS）, very long baseline interferometry（VLBI）, and satellite laser ranging（SLR） equipment. Co-location surveying of these sites was performed in 2012 and the accuracies of the solved tie vectors are approximately 5 mm.This paper proposes a mathematical model that handles the least squares adjustment of the 3D control network and calculates the tie vectors in one step, using all the available constraints in the adjustment. Using the new mathematical model, local tie vectors can be more precisely determined and their covariance more reasonably estimated.展开更多
The imaging of two supermassive black holes by the Event Horizon Telescope Collaboration proved to a new level the correctness of Einstein's general relativity,regarding its prediction of black hole shadows in the...The imaging of two supermassive black holes by the Event Horizon Telescope Collaboration proved to a new level the correctness of Einstein's general relativity,regarding its prediction of black hole shadows in the highly curved spacetime regime.展开更多
The precise orbit determination of ChanE-2 is the most important issue for successful mission and scientific applications, while the lunar gravity field model with big un- certainties has large effect on Chang＇E-2 or...The precise orbit determination of ChanE-2 is the most important issue for successful mission and scientific applications, while the lunar gravity field model with big un- certainties has large effect on Chang＇E-2 orbit determination. Recently, several new gravity models have been produced using the latest lunar satellites tracking data, such as LP16SP, SGM1SOJ, GL0900D and GRGM900C. In this paper, the four gravity models mentioned above were evaluated through the power spectra analysis, admittance and coherence analysis. Effect of four lunar gravity models on Chang＇E-2 orbit determination performance is investigated and assessed using Very Long Baseline Interferometry （VLBI） tracking data. The overlap orbit analysis, the posteriori data residual, and the orbit prediction are used to evaluate the orbit precision between successive arcs. The LPI65P model has better orbit overlap performance than the SGM150J model for Chang＇E-2100 km x 100 km orbit and the SGM150J model performs better for Chang＇E-2100 km x 15 km orbit, while GL0900D and GRGM900C have the best orbit overlap results for the two types of Chang＇E-2 orbit. For the orbit prediction, GRGM900C has the best orbit prediction performance in the four models.展开更多
Multi-baseline synthetic aperture radar interferometry(InSAR),capable of mapping 3D surface model with high precision,is able to overcome the ill-posed problem in the single-baseline InSAR.Current tandem SAR mission u...Multi-baseline synthetic aperture radar interferometry(InSAR),capable of mapping 3D surface model with high precision,is able to overcome the ill-posed problem in the single-baseline InSAR.Current tandem SAR mission utilizes a two-stage global coverage to get the dual-baseline interferograms,which achieves the trade-off between the unwrapping errors and height precision.However,the baseline adjustment will decrease the timeliness of the data acquisition,which is not suitable for monitoring temporal changes of the ground targets.Designing a SAR mission with the single-pass multi-baseline acquisition will improve the practical capability in fast 3D reconstruction.Following the asymptotic 3D phase unwrapping proposed for the airborne array InSAR system,it is possible to get a reliable 3D reconstruction using very sparse acquisitions but the interferograms should follow the optimal baseline configuration.In this article,a new concept of tandem multi-antenna SAR interferometry system for acquiring optimal single-pass multi-baseline interferograms is proposed.Two indicators,i.e.,expected relative height precision and successful phase unwrapping rate,are selected to optimize the system parameters.Additionally,taking the satellites with two antennas as an example,the performances of various baseline configurations in typical scenarios and the impact of different error sources are investigated correspondingly.The simulation-based experiments demonstrate that the proposed system acquires the optimal MB interferograms for asymptotic 3D phase unwrapping,and thus enables good performance in both urban and forest area in a single flight.This system has the potential applications in accurate digital surface model acquisition,3D target recognition,and biomass estimation.展开更多
文摘在国际甚长基线干涉测量(very long baseline interferometry,VLBI)大地测量与天体测量服务组织协调下,首次利用隶属于VLBI全球观测系统(VLBI global observing system,VGOS)的美国Kokee和德国Wettzell观测站及并置的传统VLBI观测站开展了世界时(universal time,UT1)联合测量试验,观测数据在上海VLBI中心进行了干涉处理。结果表明,VGOS超宽带观测系统的UT1测量精度约为7μs,并置基线的传统S/X双频系统测量精度约为14μs,VGOS系统的UT1解算结果优于S/X系统。通过试验建立了从相关处理、相关后处理到UT1参数解算的完整数据处理流程,验证了上海VLBI相关处理机的VGOS数据处理能力,为承担国内和国际VGOS观测数据的相关处理任务奠定了基础。
基金The work was financially supported by the National Key Research and Development Program of China(No.2018YFC1505402)the National Natural Science Foundation of China(Nos.41941019,41521002)+1 种基金the Key R&D project of the Science and Technology Department of the Sichuan Province of China(No.2019YFG0460)the Science and Technology Innovation Fund of the Sichuan Earthquake Agency(No.201901)。
文摘Zhouqu County in Gansu Province, Northwest China, is typically highly prone to landslides. On July 12, 2018, a landslide blocked the Bailong River near Zhouqu County, posing a serious threat to the life and property of local residents and the safety of infrastructure. Small baseline subset interferometry synthetic aperture radar technology(SBAS-In SAR) was adopted to identify the potential active landslides in the surrounding area of Zhouqu County, using ascending and descending orbit Sentinel-1 satellite images taken from October 2017 to December 2018. The surface deformation areas detected by SBAS-In SAR were verified by optical remote sensing image interpretation and field investigation, and a total of 23 active landslides were identified finally. The deformation characteristics of four typical landslides are analysed in detail using deformation velocity and rainfall data. It is found that the deformation velocity of landslides in this area is mainly affected by rainfall and there is a lag effect. The results can provide a reference for the prevention and control of landslide risk in Zhouqu County.
基金supported by the Open Fund of Hubei Luojia Laboratory (No. 220100033)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB41000000)+1 种基金National Natural Science Foundation of China (Grant Nos. 42174108, 41874094, 42192535 and 42242015)the Young Top-notch Talent Cultivation Program of Hubei Province。
文摘The Earth’s Free Core Nutation(FCN) causes Earth tides and forced nutation with frequencies close to the FCN that exhibit resonance effects.High-precision superconducting gravimeter(SG) and very long baseline interferometry(VLBI) provide good observation techniques for detecting the FCN parameters.However,some choices in data processing and solution procedures increase the uncertainty of the FCN parameters.In this study,we analyzed the differences and the effectiveness of weight function and ocean tide corrections in the FCN parameter detection using synthetic data,SG data from thirty-one stations,and the 10 celestial pole offset(CPO) series.The results show that significant discrepancies are caused by different computing options for a single SG station.The stacking method,which results in a variation of0.24-5 sidereal days(SDs) in the FCN period(T) and 10^(3)-10^(4) in the quality factor(Q) due to the selection of the weighting function and the ocean tide model(OTM),can effectively suppress this influence.The statistical analysis results of synthetic data shows that although different weight choices,while adjusting the proportion of diurnal tidal waves involved,do not significantly improve the accuracy of fitted FCN parameters from gravity observations.The study evaluated a series of OTMs using the loading correction efficiency.The fitting of FCN parameters can be improved by selecting the mean of appropriate OTMs based on the evaluation results.Through the estimation of the FCN parameters based on the forced nutation,it was found that the weight function P_(1) is more suitable than others,and different CPO series(after 2009) resulted in a difference of 0.4 SDs in the T and of 103 in the Q.We estimated the FCN parameters for SG(T=430.4±1.5 SDs and Q=1.52×10^(4)±2.5×10^(3)) and for VLBI(T=429.8±0.7 SDs,Q=1.88×10^(4)±2.1×10^(3)).
基金sponsored by the Crustal Movement Observation Network of China(CMONOC)partially supported by the Natural Science Foundation of China(41274035,41174023)
文摘The seven co-located sites of the Crustal Movement Observation Network of China（CMONOC） in Shanghai, Wuhan, Kunming, Beijing, Xi＇an, Changchun, and Urumqi are equipped with Global Navigation Satellite System（GNSS）, very long baseline interferometry（VLBI）, and satellite laser ranging（SLR） equipment. Co-location surveying of these sites was performed in 2012 and the accuracies of the solved tie vectors are approximately 5 mm.This paper proposes a mathematical model that handles the least squares adjustment of the 3D control network and calculates the tie vectors in one step, using all the available constraints in the adjustment. Using the new mathematical model, local tie vectors can be more precisely determined and their covariance more reasonably estimated.
文摘The imaging of two supermassive black holes by the Event Horizon Telescope Collaboration proved to a new level the correctness of Einstein's general relativity,regarding its prediction of black hole shadows in the highly curved spacetime regime.
基金funded by National Natural Science Foundation of China(41374012)
文摘The precise orbit determination of ChanE-2 is the most important issue for successful mission and scientific applications, while the lunar gravity field model with big un- certainties has large effect on Chang＇E-2 orbit determination. Recently, several new gravity models have been produced using the latest lunar satellites tracking data, such as LP16SP, SGM1SOJ, GL0900D and GRGM900C. In this paper, the four gravity models mentioned above were evaluated through the power spectra analysis, admittance and coherence analysis. Effect of four lunar gravity models on Chang＇E-2 orbit determination performance is investigated and assessed using Very Long Baseline Interferometry （VLBI） tracking data. The overlap orbit analysis, the posteriori data residual, and the orbit prediction are used to evaluate the orbit precision between successive arcs. The LPI65P model has better orbit overlap performance than the SGM150J model for Chang＇E-2100 km x 100 km orbit and the SGM150J model performs better for Chang＇E-2100 km x 15 km orbit, while GL0900D and GRGM900C have the best orbit overlap results for the two types of Chang＇E-2 orbit. For the orbit prediction, GRGM900C has the best orbit prediction performance in the four models.
基金supported in part by the National Nature Science Foundation of China under grants 61991422 and 62201158.
文摘Multi-baseline synthetic aperture radar interferometry(InSAR),capable of mapping 3D surface model with high precision,is able to overcome the ill-posed problem in the single-baseline InSAR.Current tandem SAR mission utilizes a two-stage global coverage to get the dual-baseline interferograms,which achieves the trade-off between the unwrapping errors and height precision.However,the baseline adjustment will decrease the timeliness of the data acquisition,which is not suitable for monitoring temporal changes of the ground targets.Designing a SAR mission with the single-pass multi-baseline acquisition will improve the practical capability in fast 3D reconstruction.Following the asymptotic 3D phase unwrapping proposed for the airborne array InSAR system,it is possible to get a reliable 3D reconstruction using very sparse acquisitions but the interferograms should follow the optimal baseline configuration.In this article,a new concept of tandem multi-antenna SAR interferometry system for acquiring optimal single-pass multi-baseline interferograms is proposed.Two indicators,i.e.,expected relative height precision and successful phase unwrapping rate,are selected to optimize the system parameters.Additionally,taking the satellites with two antennas as an example,the performances of various baseline configurations in typical scenarios and the impact of different error sources are investigated correspondingly.The simulation-based experiments demonstrate that the proposed system acquires the optimal MB interferograms for asymptotic 3D phase unwrapping,and thus enables good performance in both urban and forest area in a single flight.This system has the potential applications in accurate digital surface model acquisition,3D target recognition,and biomass estimation.
