Evaluation and improvement of coastal GNSS reflectometry sea level variations from existing GNSS stations in Taiwan

Global sea level rise due to an increasingly warmer climate has begun to induce hazards, adversely affecting the lives and properties of people residing in low-lying coastal regions and islands. Therefore, it is important to monitor and understand variations in coastal sea level covering offshore regions. Signal-to-noise ratio (SNR) data of Global Navigation Satellite System (GNSS) have been successfully used to robustly derive sea level heights (SLHs). In Taiwan, there are a number of continuously operating GNSS stations, not originally installed for sea level monitoring. They were established in harbors or near coastal regions for monitoring land motion. This study utilizes existing SNR data from three GNSS stations (Kaohsiung, Suao, and TaiCOAST) in Taiwan to compute SLHs with two methods, namely, Lomb–Scargle Periodogram (LSP)-only, and LSP aided with tidal harmonic analysis developed in this study. The results of both methods are compared with co-located or nearby tide gauge records. Due to the poor quality of SNR data, the worst accuracy of SLHs derived from traditional LSP-only method exceeds 1?m at the TaiCOAST station. With our procedure, the standard deviations (STDs) of difference between GNSS-derived SLHs and tide gauge records in Kaohsiung and Suao stations decreased to 10?cm and the results show excellent agreement with tide gauge derived relative sea level records, with STD of differences of 7?cm and correlation coefficient of 0.96. In addition, the absolute GNSS-R sea level trend in Kaohsiung during 2006–2011 agrees well with that derived from satellite altimetry. We conclude that the coastal GNSS stations in Taiwan have the potential of monitoring absolute coastal sea level change accurately when our proposed methodology is used.     

Global ionospheric scintillations revealed by GPS radio occultation data with FY3C satellite before midnight during the March 2015 storm

Global observations of S4 amplitude scintillation index by the GPS Occultation Sounder (GNOS) on FengYun-3 C (FY3C) satellite reveal global dynamic patterns of a strong pre-midnight scintillations in F-region of the ionosphere during the St. Patrick’s Day geomagnetic super storm of 17–19 March 2015. The observed strong scintillations mainly occurred in the low latitudes, caused by equatorial plasma bubbles. During the main storm phase (March 17), the scintillations were first triggered in the New Zealand sector near 160°E longitudes, extending beyond 40°S dip latitude. They were also enhanced in the Indian sector, but significantly suppressed in East Asia near 120°E longitude and in Africa around 30°E longitude. During the initial recovery phase (March 18–19), the global scintillations were seldom observed in GNOS data. During the later recovery phase (after March 19), the scintillations recovered to the pre-storm level in Indian, African, and American sectors, but not in East Asian and any of Pacific sectors. These results closely correlate with observations of the density depletion structures by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite, and ground-based instruments. Such consistency indicates reliability of our scintillation sensing approach even in a case-by-case comparison study. The prompt penetration electric field and disturbance dynamo electric field are suggested as the main factors that control the enhancement and inhibition of the scintillations during the storm, respectively.     

一种卫星信道的反馈优化接入机制

提高卫星信道资源利用率，探索高效可行的端站接入机制是卫星通信发展亟待解决的问题之一。当前卫星通信DVB-RCS标准基于带宽预先规划的接入机制与端站随遇接入的需求矛盾凸显，因此提出一套信道反馈优化接入机制，综合考虑各端站数据业务需求，在不改变原有协议信令特征的基础上，探索性地引入谦虚度激励方法，创造性地构造动态协商反馈模型并加以求解，达到提高端站接入数量、满足随遇接入需求、提升信道利用效率、最大化整体带宽通信业务效益的目的。通过试验验证，带宽分配反馈优化机制比传统模式提高近1倍接入率，最大端站数接入时算法耗时约只有0.67s，可为卫星信道使用提供技术参考。     

基于卫星和星敏感器的冗余激光惯组在轨标定

采用高精度卫星导航速度、位置信息以及星敏感器提供的姿态信息设计十表冗余捷联惯组的标定模型,包含陀螺和加速度计的零次项和标度因数,对卫星和星敏感器辅助的冗余激光陀螺捷联惯组进行实时在轨标定.利用标准Kalman滤波和Sage-Husa自适应滤波作为估计算法,对十表冗余捷联惯组参数进行在线估计.数值仿真结果表明:参数标定精度均在7％以内,是一种实时的在轨标定方法,满足误差补偿要求.冗余惯组在轨标定方法为航天器高精度定姿和定轨提供了一种理论参考.     

微磁强计弱磁处理芯片设计与实现

为适应微纳卫星平台的应用需求、实现磁强计的微型化,针对巨磁阻抗(GMI)效应微磁强计的研制需求设计并研制了弱磁信号处理芯片.在分析GMI微磁强计构造的基础上,针对单机(微)小型化提出了弱磁信号处理电路芯片化的方案;结合空间应用特点,设计并实现了基于SOI CMOS工艺的弱磁信号处理芯片.实测结果表明:基于所研制的弱磁信号处理芯片不仅实现了磁强计的微型化、集成化,而且具有良好的弱磁测量性能.     

低轨卫星月影事件预报优化

针对卫星月影问题,提出了一种低轨卫星优化的月影预报策略,可以有效提高目前低轨卫星在轨管理时对月影事件预报的效率.结合仿真对产生月影事件的太阳、地球、月球的三体关系进行了分析,首先给出了月影产生的解析分析方法,并通过对一个三维月影影响模型的分析,得到了月影影响区间的判定要素——月影临界角;然后进一步通过对月影临界角的分析,提出了基于太阳与白道面的位置关系和月影临界角对低轨卫星月影事件的优化预报方法;最后基于大量的随机低轨卫星场景对本方法的正确性进行了验证.研究结果表明,此方法能够较大地提高月影预报效率,可以将月影预报频率从每月1次降低到每年2次,从而简化了低轨卫星在轨运行管理的任务复杂度,为卫星的在轨可靠运行提供支持.     

用于光波纳米推力器的颗粒供应技术和光聚积技术研究

为提高光波纳米推力器在轨应用的可行性,针对与其匹配的颗粒供应技术和光聚积技术进行研究。提出整个推进系统的设计思路,通过建立理论计算和数值计算模型,分析颗粒供应技术和光聚积技术的各项核心结构参数的设计方法。计算结果表明:颗粒供应装置的正负电极内径之比(W/D)会影响正负电荷产生的总量之比,在W/D=300/322附近时,正负电荷比例接近1:1。静电诱导电压为9 V,当中和通道长度大于37.5mm时,正负颗粒可以视为完全中和。光聚积设计思路可令聚积球对光能的利用率在32.8%左右。两种相关技术的装置与推力器在结构上能够对接、在性能上可以匹配,从理论上表明了两种支撑技术的可行性。     

基于气压高度辅助的机载自主完好性监测算法

卫星接收机自主完好性监测是指根据用户接收机的多余观测值监测用户定位结果的完好性,其目的是在导航过程中检测出发生故障的卫星,并保障导航定位精度。针对卫星接收机自主完好性监测算法可用性不足的问题,结合机载实际导航系统配置,提出了一种基于气压高度表辅助的机载自主完好性监测算法。综合利用卫星导航系统及气压高度表观测信息,建立联合系统的观测模型,推导了基于多解分离的完好性监测及保护级别计算方法。仿真结果表明,相比于传统的接收机自主完好性监测算法,该算法在可见星为5颗时仍能识别故障卫星。该算法具有更好的故障检测能力及可用性,能有效提高卫星导航系统的完好性监测性能,从而保证卫星导航系统的精度和可靠性。     

卫星通信干扰样式研究

综述通信对抗干扰的分类方式,分析了部分文献中对干扰样式划分的不合理性.根据卫星通信对抗的特点将通信对抗干扰样式进行分类,并从与压制式干扰相区别的角度对欺骗式干扰做出研究分析.     

卫星用两种单相流体回路方案对比研究

单相流体回路系统是航天器主动热控技术中的一种重要方式。文章概述了流体回路的工作原理及理论基础，总结了单相流体回路的设计思路，结合某卫星型号，设计了两种流体回路方案，在SINDA／FLUINT中建立数值仿真模型进行分析计算，并比较了两种方案的应用性能。结果显示，将单相流体回路系统应用于卫星，可取得较好的控温效果。