Decimeter-level service is provided by the BeiDou satellite navigation system wide area differential service(BDS WADS)for users who collect carrier phase measurements.However,the fluctuations in Geostationary Earth Or...Decimeter-level service is provided by the BeiDou satellite navigation system wide area differential service(BDS WADS)for users who collect carrier phase measurements.However,the fluctuations in Geostationary Earth Orbit(GEO)satellite orbit errors reduce the spatial correlation of orbit errors.These fluctuations not only decrease the accuracy and stability of zone correction service provided by BDS WADS,but also shorten its effective range.In this paper,we proposed an algorithm to weaken the influence of GEO satellite orbit error fluctuations and verified the method using data from eight sparsely distributed zones.The results show that orbit errors can be stabilized using orbit fluctuation corrections,and the positioning precision and stability of the BDS WADS can be improved simultaneously.Under normal circumstances,the horizontal and vertical positioning accuracy of users within 1000 km from the center of the zone can reach 0.19 m and 0.34 m.Furthermore,the effective range is increased.The positioning performance within 1800 km could reach 0.24 m and 0.38 m for the horizontal and vertical components,respectively.展开更多
Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position ac...Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position accuracy is affected by several factors such as satellite clock error, propagation path delays and receiver noise due to which the GPS does not meet the requirements of critical navigation applications such as missile navigation and category I/II/III aircraft landings. This paper emphasizes on modelling the satellite clock error and orbital solution (satellite position) error considering the signal emission time. The transmission time sent by each satellite in broadcast ephemerides is not accurate. This has to be corrected in order to obtain correct satellite position and in turn a precise receiver position. Signal transmission time or broadcast time from satellite antenna phase center is computed at the receiver using several parameters such as signal reception time, propagation time, pseudorange observed and satellite clock error correction parameters. This corrected time of transmission and broadcast orbital parameters are used for estimation of the orbital solution. The estimated orbital solution was validated with the precise ephemerides which are estimated by Jet Propulsion Laboratory (JPL), USA. The errors are estimated for a typical day data collected on 11th March 2011 from dual frequency GPS receiver located at Department of Electronics and Communication Engineering, Andhra University College of Engineering, Visakhapatnam (17.73°N/83.319°E).展开更多
In the study, position and velocity values of a geostationary satellite are found. When performing this, a MATLAB algorithm is used for Runge-Kutta Fehlberg orbit integration method to solve spacecraft’s position and...In the study, position and velocity values of a geostationary satellite are found. When performing this, a MATLAB algorithm is used for Runge-Kutta Fehlberg orbit integration method to solve spacecraft’s position and velocity. Integrated method is the solution for the systems which mainly work with a single station. Method provides calculation of azimuth, elevation and range data by using the position simulation results found by RKF. Errors of orbit determination are analysed. Variances of orbit parameters are chosen as the accuracy criteria. Analysis results are the indicator of the method’s展开更多
针对大视场红外相机在轨调焦时受大气条件、地物丰富度、月相角等因素影响导致对地调焦和对月调焦周期长、效率低的问题,文章提出一种基于星点亚像元误差补偿的红外相机在轨检焦方法,通过对未经大气退化的星点图像进行精准质心定位提取...针对大视场红外相机在轨调焦时受大气条件、地物丰富度、月相角等因素影响导致对地调焦和对月调焦周期长、效率低的问题,文章提出一种基于星点亚像元误差补偿的红外相机在轨检焦方法,通过对未经大气退化的星点图像进行精准质心定位提取清晰度评价指标,有效规避外界因素的影响,提升在轨检焦效率,保障在轨检焦精度。首先对星点图像分别采用自适应阈值质心法和高斯拟合法提取质心估计值;依据图像信噪比、星点目标能量集中度确定最佳因子,构建误差补偿模型进行精确质心定位;再提取图像点扩散函数的波形半高宽(Full Width at Half Maximum,FWHM)作为在轨检焦清晰度评价指标;设置不同谱段、不同能量集中度的星点红外图像作为在轨检焦图像,分别采用质心法、高斯拟合法及星点亚像元误差补偿方法进行目标质心提取并估计FWHM,实验结果表明:三种方法的质心提取平均误差分别为0.1195、0.0107、0.0027,均方根误差分别为0.1210、0.0124、0.0085,星点亚像元误差补偿方法质心提取误差最小,稳定性最好。能量集中度为0.4~0.8之间时,采用星点亚像元误差补偿方法质心提取平均误差均小于0.01,优于其他方法。在此基础上,采用该方法提取的FWHM平均精度提升了三倍以上,且不受星点质心位置随机性的影响,对于实现基于恒星的在轨检焦具有较高的可靠性和稳定性,满足在轨检焦要求。展开更多
基金the National Natural Science Funds of China(Grant No.41604032).
文摘Decimeter-level service is provided by the BeiDou satellite navigation system wide area differential service(BDS WADS)for users who collect carrier phase measurements.However,the fluctuations in Geostationary Earth Orbit(GEO)satellite orbit errors reduce the spatial correlation of orbit errors.These fluctuations not only decrease the accuracy and stability of zone correction service provided by BDS WADS,but also shorten its effective range.In this paper,we proposed an algorithm to weaken the influence of GEO satellite orbit error fluctuations and verified the method using data from eight sparsely distributed zones.The results show that orbit errors can be stabilized using orbit fluctuation corrections,and the positioning precision and stability of the BDS WADS can be improved simultaneously.Under normal circumstances,the horizontal and vertical positioning accuracy of users within 1000 km from the center of the zone can reach 0.19 m and 0.34 m.Furthermore,the effective range is increased.The positioning performance within 1800 km could reach 0.24 m and 0.38 m for the horizontal and vertical components,respectively.
文摘Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position accuracy is affected by several factors such as satellite clock error, propagation path delays and receiver noise due to which the GPS does not meet the requirements of critical navigation applications such as missile navigation and category I/II/III aircraft landings. This paper emphasizes on modelling the satellite clock error and orbital solution (satellite position) error considering the signal emission time. The transmission time sent by each satellite in broadcast ephemerides is not accurate. This has to be corrected in order to obtain correct satellite position and in turn a precise receiver position. Signal transmission time or broadcast time from satellite antenna phase center is computed at the receiver using several parameters such as signal reception time, propagation time, pseudorange observed and satellite clock error correction parameters. This corrected time of transmission and broadcast orbital parameters are used for estimation of the orbital solution. The estimated orbital solution was validated with the precise ephemerides which are estimated by Jet Propulsion Laboratory (JPL), USA. The errors are estimated for a typical day data collected on 11th March 2011 from dual frequency GPS receiver located at Department of Electronics and Communication Engineering, Andhra University College of Engineering, Visakhapatnam (17.73°N/83.319°E).
文摘In the study, position and velocity values of a geostationary satellite are found. When performing this, a MATLAB algorithm is used for Runge-Kutta Fehlberg orbit integration method to solve spacecraft’s position and velocity. Integrated method is the solution for the systems which mainly work with a single station. Method provides calculation of azimuth, elevation and range data by using the position simulation results found by RKF. Errors of orbit determination are analysed. Variances of orbit parameters are chosen as the accuracy criteria. Analysis results are the indicator of the method’s
文摘针对大视场红外相机在轨调焦时受大气条件、地物丰富度、月相角等因素影响导致对地调焦和对月调焦周期长、效率低的问题,文章提出一种基于星点亚像元误差补偿的红外相机在轨检焦方法,通过对未经大气退化的星点图像进行精准质心定位提取清晰度评价指标,有效规避外界因素的影响,提升在轨检焦效率,保障在轨检焦精度。首先对星点图像分别采用自适应阈值质心法和高斯拟合法提取质心估计值;依据图像信噪比、星点目标能量集中度确定最佳因子,构建误差补偿模型进行精确质心定位;再提取图像点扩散函数的波形半高宽(Full Width at Half Maximum,FWHM)作为在轨检焦清晰度评价指标;设置不同谱段、不同能量集中度的星点红外图像作为在轨检焦图像,分别采用质心法、高斯拟合法及星点亚像元误差补偿方法进行目标质心提取并估计FWHM,实验结果表明:三种方法的质心提取平均误差分别为0.1195、0.0107、0.0027,均方根误差分别为0.1210、0.0124、0.0085,星点亚像元误差补偿方法质心提取误差最小,稳定性最好。能量集中度为0.4~0.8之间时,采用星点亚像元误差补偿方法质心提取平均误差均小于0.01,优于其他方法。在此基础上,采用该方法提取的FWHM平均精度提升了三倍以上,且不受星点质心位置随机性的影响,对于实现基于恒星的在轨检焦具有较高的可靠性和稳定性,满足在轨检焦要求。
