星地通信背景下,P波段信号在穿越大气到达地面阵列的过程中,受到电离层效应的影响,其波达方向(Direction of Arrival,DOA)与极化角均发生改变,因此现有DOA-极化联合估计算法得到的估计值与真实值之间存在误差。为解决此问题,从DOA和极...星地通信背景下,P波段信号在穿越大气到达地面阵列的过程中,受到电离层效应的影响,其波达方向(Direction of Arrival,DOA)与极化角均发生改变,因此现有DOA-极化联合估计算法得到的估计值与真实值之间存在误差。为解决此问题,从DOA和极化角两个方面分别进行校正。首先考虑电离层折射效应,建立电离层信号传播模型,以此为基础提出俯仰角误差修正方法。其次针对电离层法拉第旋转(Faraday Rotation,FR)效应,分析法拉第旋转角(Faraday Rotation Angle,FRA)对信号极化的影响,根据地面目标散射过程,提出两种基于散射矩阵的FRA估计方法。通过仿真实验可知,所提方法可以准确计算P波段信号俯仰角修正值与FRA,在一定条件下,将俯仰角估计精度提高约0.1°,FRA估计精度提高近1°,从而实现DOA与极化角的校正。展开更多
张衡一号卫星在轨6年积累了海量观测数据,检测其中的闪电哨声波事件(Lightning Whistler,LW)对于分析空间物理环境规律具有重要意义.但现有基于时频图像的方法推理速度过慢,完成任务需约40年.为此,研究首次从音频事件检测的角度提出高...张衡一号卫星在轨6年积累了海量观测数据,检测其中的闪电哨声波事件(Lightning Whistler,LW)对于分析空间物理环境规律具有重要意义.但现有基于时频图像的方法推理速度过慢,完成任务需约40年.为此,研究首次从音频事件检测的角度提出高速的闪电哨声波检测模型WhisNet,将检测的时间成本从40年压缩至54天.方法为以4 s滑动窗截取波形,提取梅尔频谱特征,利用轻量级卷积循环神经网络(CRNN)提取音频事件特征,输出层预测LW事件起始时间和持续时长.基于2020年4月1-10日的感应磁力仪(SCM)数据实验显示,WhisNet检测性能与传统方法相当,但计算量和参数量减少99%,速度提升98%.进一步在2020年5月SCM数据上的应用结果与WGLC(全球闪电气候学和时间序列,WWLLN Global Lightning Climatology and time series)全球闪电密度趋势高度一致,验证了WhisNet在大规模卫星数据处理中的准确性与适用性.研究结果为挖掘其他海量地球空间事件提供了重要参考.展开更多
电离层延迟是全球卫星导航定位中重要的误差源之一,提高电离层总电子含量(Total Electron Content,TEC)预报精度对改善卫星导航定位精度极其重要.本文联合滑动窗口(Sliding Window)和长短时记忆(Long-Short-Term Memory,LSTM)神经网络,...电离层延迟是全球卫星导航定位中重要的误差源之一,提高电离层总电子含量(Total Electron Content,TEC)预报精度对改善卫星导航定位精度极其重要.本文联合滑动窗口(Sliding Window)和长短时记忆(Long-Short-Term Memory,LSTM)神经网络,以滑动窗口算法对输入序列数据集不断更新并测试不同输入序列长度对应模型的精度,最后以预测值来更新输入数据序列的最后10%,进而构建TEC预报模型SLSTM(Sliding Window on Long-Short-Term Memory).验证结果表明,该模型在平静期和磁暴期预测残差绝对值小于5TECU的比例均达85%以上,较传统LSTM模型对应值占比增加了49%,71%,均方根误差(RMSE)低31%,35%;其预报结果的平均绝对误差(MAE)减少25%,32%;SLSTM模型预测结果的RMSE均值、MAE均值均比传统LSTM模型、BP模型小.展开更多
The magnetic fields and dynamical processes in the solar polar regions play a crucial role in the solar magnetic cycle and in supplying mass and energy to the fast solar wind,ultimately being vital in controlling sola...The magnetic fields and dynamical processes in the solar polar regions play a crucial role in the solar magnetic cycle and in supplying mass and energy to the fast solar wind,ultimately being vital in controlling solar activities and driving space weather.Despite numerous efforts to explore these regions,to date no imaging observations of the Sun's poles have been achieved from vantage points out of the ecliptic plane,leaving their behavior and evolution poorly understood.This observation gap has left three top-level scientific questions unanswered:How does the solar dynamo work and drive the solar magnetic cycle?What drives the fast solar wind?How do space weather processes globally originate from the Sun and propagate throughout the solar system?The Solar Polarorbit Observatory(SPO)mission,a solar polar exploration spacecraft,is proposed to address these three unanswered scientific questions by imaging the Sun's poles from high heliolatitudes.In order to achieve its scientific goals,SPO will carry six remote-sensing and four in-situ instruments to measure the vector magnetic fields and Doppler velocity fields in the photosphere,to observe the Sun in the extreme ultraviolet,X-ray,and radio wavelengths,to image the corona and the heliosphere up to 45 R_(s),and to perform in-situ detection of magnetic fields,and low-and high-energy particles in the solar wind.The SPO mission is capable of providing critical vector magnetic fields and Doppler velocities of the polar regions to advance our understanding of the origin of the solar magnetic cycle,providing unprecedented imaging observations of the solar poles alongside in-situ measurements of charged particles and magnetic fields from high heliolatitudes to unveil the mass and energy supply that drive the fast solar wind,and providing observational constraints for improving our ability to model and predict the three-dimensional(3D)structures and propagation of space weather events.展开更多
文摘利用全球导航卫星系统(Global Navigation Satellite System,GNSS)双频差分信号进行电离层电子含量反演是一种常用的电离层探测手段,但GNSS信号在强电磁干扰环境下,被淹没于电磁噪声中而无法被提取,影响电离层总电子含量(total electron content,TEC)反演系统的可靠性。采用传统调零抗干扰阵列天线方案能解决干扰源剥离的问题,但调零信号的天线相位中心不稳定导致高精度的相位平滑伪距和精密单点定位(precise point positioning,PPP)算法无法收敛。针对强干扰环境下的电离层监测需求,本文提出一种抗干扰TEC数据反演手段,通过对阵列天线通道幅相一致性进行校正,保证相位中心的稳定性,从而推算出准确的电离层TEC信息,提高了系统的可靠性和抗干扰能力。
文摘张衡一号卫星在轨6年积累了海量观测数据,检测其中的闪电哨声波事件(Lightning Whistler,LW)对于分析空间物理环境规律具有重要意义.但现有基于时频图像的方法推理速度过慢,完成任务需约40年.为此,研究首次从音频事件检测的角度提出高速的闪电哨声波检测模型WhisNet,将检测的时间成本从40年压缩至54天.方法为以4 s滑动窗截取波形,提取梅尔频谱特征,利用轻量级卷积循环神经网络(CRNN)提取音频事件特征,输出层预测LW事件起始时间和持续时长.基于2020年4月1-10日的感应磁力仪(SCM)数据实验显示,WhisNet检测性能与传统方法相当,但计算量和参数量减少99%,速度提升98%.进一步在2020年5月SCM数据上的应用结果与WGLC(全球闪电气候学和时间序列,WWLLN Global Lightning Climatology and time series)全球闪电密度趋势高度一致,验证了WhisNet在大规模卫星数据处理中的准确性与适用性.研究结果为挖掘其他海量地球空间事件提供了重要参考.
文摘电离层延迟是全球卫星导航定位中重要的误差源之一,提高电离层总电子含量(Total Electron Content,TEC)预报精度对改善卫星导航定位精度极其重要.本文联合滑动窗口(Sliding Window)和长短时记忆(Long-Short-Term Memory,LSTM)神经网络,以滑动窗口算法对输入序列数据集不断更新并测试不同输入序列长度对应模型的精度,最后以预测值来更新输入数据序列的最后10%,进而构建TEC预报模型SLSTM(Sliding Window on Long-Short-Term Memory).验证结果表明,该模型在平静期和磁暴期预测残差绝对值小于5TECU的比例均达85%以上,较传统LSTM模型对应值占比增加了49%,71%,均方根误差(RMSE)低31%,35%;其预报结果的平均绝对误差(MAE)减少25%,32%;SLSTM模型预测结果的RMSE均值、MAE均值均比传统LSTM模型、BP模型小.
文摘The magnetic fields and dynamical processes in the solar polar regions play a crucial role in the solar magnetic cycle and in supplying mass and energy to the fast solar wind,ultimately being vital in controlling solar activities and driving space weather.Despite numerous efforts to explore these regions,to date no imaging observations of the Sun's poles have been achieved from vantage points out of the ecliptic plane,leaving their behavior and evolution poorly understood.This observation gap has left three top-level scientific questions unanswered:How does the solar dynamo work and drive the solar magnetic cycle?What drives the fast solar wind?How do space weather processes globally originate from the Sun and propagate throughout the solar system?The Solar Polarorbit Observatory(SPO)mission,a solar polar exploration spacecraft,is proposed to address these three unanswered scientific questions by imaging the Sun's poles from high heliolatitudes.In order to achieve its scientific goals,SPO will carry six remote-sensing and four in-situ instruments to measure the vector magnetic fields and Doppler velocity fields in the photosphere,to observe the Sun in the extreme ultraviolet,X-ray,and radio wavelengths,to image the corona and the heliosphere up to 45 R_(s),and to perform in-situ detection of magnetic fields,and low-and high-energy particles in the solar wind.The SPO mission is capable of providing critical vector magnetic fields and Doppler velocities of the polar regions to advance our understanding of the origin of the solar magnetic cycle,providing unprecedented imaging observations of the solar poles alongside in-situ measurements of charged particles and magnetic fields from high heliolatitudes to unveil the mass and energy supply that drive the fast solar wind,and providing observational constraints for improving our ability to model and predict the three-dimensional(3D)structures and propagation of space weather events.
