The near-Earth asteroid collisions could cause catastrophic disasters to humanity and the Earth,so it is crucial to monitor asteroids.Ground-based synthetic aperture radar(SAR)is an observation technique for high reso...The near-Earth asteroid collisions could cause catastrophic disasters to humanity and the Earth,so it is crucial to monitor asteroids.Ground-based synthetic aperture radar(SAR)is an observation technique for high resolution imaging of asteroids.The ground-based SAR requires a long integration time to achieve a large synthetic aperture,and the echo signal will be seriously affected by temporal-spatial variant troposphere.Traditional spatiotemporal freezing tropospheric models are ineffective.To cope with this,this paper models and analyses the impacts of temporal-spatial variant troposphere on ground-based SAR imaging of asteroids.For the background tropo-sphere,a temporal-spatial variant ray tracing method is proposed to trace the 4D(3D spatial+temporal)refractive index network provided by the numerical weather model,and calculate the error of the background troposphere.For the tropospheric turbulence,the Andrew power spectral model is used in conjunction with multiphase screen theory,and varying errors are obtained by tracking the changing position of the pierce point on the phase screen.Through simulation,the impact of temporal-spatial variant tropospheric errors on image quality is analyzed,and the simulation results show that the X-band echo signal is seriously affected by the troposphere and the echo signal must be compensated.展开更多
利用2021-09全球80个MGEX测站进行PPP实验,以国际GNSS服务组织(IGS)发布的ZTD产品为参考进行比较分析。结果表明,多系统联合估计ZTD在精度上具有较大优势,GPS+BDS双系统比单GPS系统平均RMSE精度提高约0.6 mm, GPS+BDS+GLONASS+Galileo...利用2021-09全球80个MGEX测站进行PPP实验,以国际GNSS服务组织(IGS)发布的ZTD产品为参考进行比较分析。结果表明,多系统联合估计ZTD在精度上具有较大优势,GPS+BDS双系统比单GPS系统平均RMSE精度提高约0.6 mm, GPS+BDS+GLONASS+Galileo四系统比双系统精度提高约0.9 mm,单系统条件下GPS的ZTD估计精度高于BDS。在精度空间分布上,随着纬度升高ZTD估计精度提升较为明显,当纬度大于50°时,四系统PPP估计的ZTD精度优于5 mm。在纬度基本不变的情况下,观测站海拔升高可提升ZTD估计精度。在模糊度固定的情况下,ZTD估计精度明显提升,单GPS系统估计ZTD的平均绝对误差(MAE)和均方根误差(RMSE)分别为7.6 mm和8.4 mm,相比于浮点解分别提高约11%和12%,平均收敛时间加快20 min。展开更多
The conventional zenith tropospheric delay(ZTD)model(known as the Saastamoinen model)does not consider seasonal variations affecting the delay,giving it low accuracy and stability.This may be improved with adjustments...The conventional zenith tropospheric delay(ZTD)model(known as the Saastamoinen model)does not consider seasonal variations affecting the delay,giving it low accuracy and stability.This may be improved with adjustments to account for annual and semi-annual variations.This method uses ZTD data provided by the Global Geodetic Observing System to analyze seasonal variations in the bias of the Saastamoinen model in Asia,and then constructs a model with seasonal variation corrections,denoted as SSA.To overcome the dependence of the model on in-situ meteorological parameters,the SSA+GPT3 model is formed by combining the SSA and GPT3(global pressure-temperature)models.The results show that the introduction of annual and semi-annual variations can substantially improve the Saastamoinen model,yielding small and time-stable variations in bias and root mean square(RMS).In summer and autumn,the bias and RMS are noticeably smaller than those from the Saastamoinen model.In addition,the SSA model performs better in low-latitude and low-altitude areas,and bias and RMS decease with the increase of latitude or altitude.The prediction accuracy of the SSA model is also evaluated for external consistency.The results show that the accuracy of the SSA model(bias:-0.38 cm,RMS:4.43 cm)is better than that of the Saastamoinen model(bias:1.45 cm,RMS:5.16 cm).The proposed method has strong applicability and can therefore be used for predictive ZTD correction across Asia.展开更多
通过并网整合、站点加密、差站迁建和软件升级,建立网形更优、覆盖更广的新一代昆明市卫星定位综合服务系统(Kunming Continuously Operating Reference Stations,KMCORS)。在KMCORS的NRTK(Network Real Time Kinematic,网络实时动态定...通过并网整合、站点加密、差站迁建和软件升级,建立网形更优、覆盖更广的新一代昆明市卫星定位综合服务系统(Kunming Continuously Operating Reference Stations,KMCORS)。在KMCORS的NRTK(Network Real Time Kinematic,网络实时动态定位技术)性能测试中,于C级测试点CD(长地)和DY(大营)处发现定位异常问题,为分析其原因,进行测试点原成果检核和对流层异常探测工作。结果表明,DY点位因施工发生偏移,其修正坐标符合NRTK定位结果;CD点对流层状态异常,与临近CORS站存在显著差异,致使其对流层延迟未能有效订正,最终造成较大的高程误差。今后,将收集CD附近区域的观测数据,用以精化KMCORS现有的对流层模型。展开更多
针对已有天顶湿延迟(zenith wet delay,ZWD)模型的建模数据未能顾及精细的日周期变化的问题,为充分探究顾及日周期变化对建模的精度影响,根据2015—2017年ECMWF提供的第5代再分析资料(ERA5)建立未顾及日变化的CZWD_1模型和顾及日变化的C...针对已有天顶湿延迟(zenith wet delay,ZWD)模型的建模数据未能顾及精细的日周期变化的问题,为充分探究顾及日周期变化对建模的精度影响,根据2015—2017年ECMWF提供的第5代再分析资料(ERA5)建立未顾及日变化的CZWD_1模型和顾及日变化的CZWD_2模型,利用未参与建模的2018年ERA5再分析资料和无线电探空数据进行精度验证,并与广泛使用的GPT3模型进行精度对比。结果表明:以2018年ERA5再分析资料为参考值,CZWD_2模型表现出最优的精度,年均均方根(root mean square,RMS)值相较于GPT3和CZWD_1模型分别提高了0.90 cm (18.7%)和0.32 cm (7.6%);以2018年无线电探空数据为参考值,CZWD_2模型的年均均方根(root mean square,RMS)值相较于GPT3和CZWD_1模型分别提高了1.24 cm (21.2%)和0.47 cm (9.3%)。此外,将所构建的ZWD模型应用于全球导航卫星系统(global navigation satellite systems,GNSS)水汽(precipitable water vapor,PWV)反演,CZWD_2模型表现出最优的反演精度,其RMS值相较于GPT3和CZWD_1模型分别提高了1.52 mm (27.7%)和0.38 mm (8.8%)。因此,CZWD_2模型更适用于中国东部地区的GNSS水汽探测及气象研究。展开更多
基金supported in part by the National Natural Science Foundation of China(Nos.62101039,62201051)in part by the Shandong Excellent Young Scientists Fund Program(Overseas)in part by China Postdoctoral Science Foundation(No.2022M720443).
文摘The near-Earth asteroid collisions could cause catastrophic disasters to humanity and the Earth,so it is crucial to monitor asteroids.Ground-based synthetic aperture radar(SAR)is an observation technique for high resolution imaging of asteroids.The ground-based SAR requires a long integration time to achieve a large synthetic aperture,and the echo signal will be seriously affected by temporal-spatial variant troposphere.Traditional spatiotemporal freezing tropospheric models are ineffective.To cope with this,this paper models and analyses the impacts of temporal-spatial variant troposphere on ground-based SAR imaging of asteroids.For the background tropo-sphere,a temporal-spatial variant ray tracing method is proposed to trace the 4D(3D spatial+temporal)refractive index network provided by the numerical weather model,and calculate the error of the background troposphere.For the tropospheric turbulence,the Andrew power spectral model is used in conjunction with multiphase screen theory,and varying errors are obtained by tracking the changing position of the pierce point on the phase screen.Through simulation,the impact of temporal-spatial variant tropospheric errors on image quality is analyzed,and the simulation results show that the X-band echo signal is seriously affected by the troposphere and the echo signal must be compensated.
基金This work was supported by the Basic Science Research Program of Shaanxi Province(2023-JC-YB-057 and 2022JM-031).
文摘The conventional zenith tropospheric delay(ZTD)model(known as the Saastamoinen model)does not consider seasonal variations affecting the delay,giving it low accuracy and stability.This may be improved with adjustments to account for annual and semi-annual variations.This method uses ZTD data provided by the Global Geodetic Observing System to analyze seasonal variations in the bias of the Saastamoinen model in Asia,and then constructs a model with seasonal variation corrections,denoted as SSA.To overcome the dependence of the model on in-situ meteorological parameters,the SSA+GPT3 model is formed by combining the SSA and GPT3(global pressure-temperature)models.The results show that the introduction of annual and semi-annual variations can substantially improve the Saastamoinen model,yielding small and time-stable variations in bias and root mean square(RMS).In summer and autumn,the bias and RMS are noticeably smaller than those from the Saastamoinen model.In addition,the SSA model performs better in low-latitude and low-altitude areas,and bias and RMS decease with the increase of latitude or altitude.The prediction accuracy of the SSA model is also evaluated for external consistency.The results show that the accuracy of the SSA model(bias:-0.38 cm,RMS:4.43 cm)is better than that of the Saastamoinen model(bias:1.45 cm,RMS:5.16 cm).The proposed method has strong applicability and can therefore be used for predictive ZTD correction across Asia.
文摘通过并网整合、站点加密、差站迁建和软件升级,建立网形更优、覆盖更广的新一代昆明市卫星定位综合服务系统(Kunming Continuously Operating Reference Stations,KMCORS)。在KMCORS的NRTK(Network Real Time Kinematic,网络实时动态定位技术)性能测试中,于C级测试点CD(长地)和DY(大营)处发现定位异常问题,为分析其原因,进行测试点原成果检核和对流层异常探测工作。结果表明,DY点位因施工发生偏移,其修正坐标符合NRTK定位结果;CD点对流层状态异常,与临近CORS站存在显著差异,致使其对流层延迟未能有效订正,最终造成较大的高程误差。今后,将收集CD附近区域的观测数据,用以精化KMCORS现有的对流层模型。
文摘针对已有天顶湿延迟(zenith wet delay,ZWD)模型的建模数据未能顾及精细的日周期变化的问题,为充分探究顾及日周期变化对建模的精度影响,根据2015—2017年ECMWF提供的第5代再分析资料(ERA5)建立未顾及日变化的CZWD_1模型和顾及日变化的CZWD_2模型,利用未参与建模的2018年ERA5再分析资料和无线电探空数据进行精度验证,并与广泛使用的GPT3模型进行精度对比。结果表明:以2018年ERA5再分析资料为参考值,CZWD_2模型表现出最优的精度,年均均方根(root mean square,RMS)值相较于GPT3和CZWD_1模型分别提高了0.90 cm (18.7%)和0.32 cm (7.6%);以2018年无线电探空数据为参考值,CZWD_2模型的年均均方根(root mean square,RMS)值相较于GPT3和CZWD_1模型分别提高了1.24 cm (21.2%)和0.47 cm (9.3%)。此外,将所构建的ZWD模型应用于全球导航卫星系统(global navigation satellite systems,GNSS)水汽(precipitable water vapor,PWV)反演,CZWD_2模型表现出最优的反演精度,其RMS值相较于GPT3和CZWD_1模型分别提高了1.52 mm (27.7%)和0.38 mm (8.8%)。因此,CZWD_2模型更适用于中国东部地区的GNSS水汽探测及气象研究。
