珠海一号高光谱卫星辐射精度真实性检验研究

“珠海一号（OHS）”高光谱商业遥感卫星数据在国民经济建设中发挥着越来越重要的作用。当前，针对商业遥感卫星数据质量精度的验证和评价研究成果较少。本文基于地面实测数据，对OHS卫星高光谱数据的辐射精度进行了真实性检验和定量分析。结果表明：OHS卫星表观辐亮度与实测结果具有较好的线性相关关系，相关系数R²大于0.7。与实测结果相比，OHS卫星各通道表观辐亮度值整体偏低，但两者光谱曲线形态基本一致。随着时间的推移，OHS传感器性能可能存在衰减，不同通道的衰减程度不一；在31个通道中，与实测值之间的相对差异在20%以内的通道数为9个；在20%~30%之间为14个，30%~40%为8个。     

原子钟性能对卫星导航系统定位精度的影响分析

星载原子钟是卫星导航系统的关键设备,原子钟主要通过影响卫星钟差对定位精度产生影响,分析了GNSS星载原子钟性能对定位精度的影响.通过原理分析,建立了原子钟稳定度与卫星导航系统定位精度的关系.在不考虑控制段对星钟校准误差的前提下,将原子钟噪声与星上工作环境因素作为主要因素,分析了GPS-IIF铷钟和铯钟对钟差/定位误差的影响,并给出了分析结果.最后,利用iGMAS提供的钟差产品数据,对比了北斗和GPS部分原子钟的稳定度及其对定位精度的影响,为后续星载原子钟的发展与选择提供了一定参考.     

Adaptive cubature Kalman filter with the estimation of correlation between multiplicative noise and additive measurement noise

Mobile robots are often subject to multiplicative noise in the target tracking tasks, where the multiplicative measurement noise is correlated with additive measurement noise. In this paper,first, a correlation multiplicative measurement noise model is established. It is able to more accurately represent the measurement error caused by the distance sensor dependence state. Then, the estimated performance mismatch problem of Cubature Kalman Filter(CKF) under multiplicative noise is analyzed. An i...     

考虑在轨热效应的网状天线索网优化设计

网状天线服役于高低温、强辐射的复杂太空环境，其热变形是影响天线在轨性能的重要因素。目前的设计方法均为常温下的索段预应力配置，难以计及服役环境对天线在轨性能的影响。通过在索网模型中引入温度载荷，建立了以常温下索段参数为变量，以服役环境下的索网形面精度和张力分布为目标及约束条件的索网优化模型，从而在设计之初充分考虑服役热环境下的天线性能，改善天线在轨精度和张力分布。分析了天线运行轨道热环境，计算了天线在不同轨道位置的温度场；基于非线性有限元理论，建立了网状天线热结构模型，形成了考虑温度效应的索网找形及优化设计方法；开展了面向天线服役性能的索网优化设计。优化结果表明，该方法有效提高了天线在轨运行时的性能，可为考虑服役环境的网状天线优化设计提供方法和思路。     

瞬态热应力问题的组合杂交有限元方法

求解瞬态热应力问题的杂交元方法面临Ladyshenskaya-Babuska-Brezzi(LBB)条件的检查,其稳定性难以保证,从而提出瞬态热应力问题的组合杂交有限元方法。建立瞬态热应力问题的基于区域分解的组合杂交变分原理及其有限元离散;通过数值算例验证求解瞬态热应力问题的组合杂交元的数值性能。结果表明:在大宽厚比网格下,八节点六面体组合杂交元(CHH(0-1))可以获得与二十节点六面体元(B20)精度相当的位移计算结果和更好的应力计算结果。     

Frequency steering of spaceborne clocks based on XPNAV-1 observations

Due to high stable rotations, timing of pulsars provides a natural tool to correct the frequency deviation of spaceborne atomic clocks. Based on processing the observational data about a year of Crab pulsar given by XPNAV-1 satellite, we study the possibility of correcting the frequency deviation of spaceborne atomic clocks using pulsar timing. According to the observational data in X-ray band and the timing model parameters from radio observations, the pre-fit timing residuals with a level of 6...     

非对称偏馈环形网状天线索网预张力设计方法

提出一种考虑桁架柔性变形对索网平衡态影响的非对称偏馈环形网状天线索网预张力设计方法。该方法将天线整体结构分为内部索网与外部桁架两部分，通过内部索网预张力与外部桁架变形间的不断迭代，寻找满足索网形状及张力要求的天线平衡态，以实现网状天线索网预张力优化配置的目的。相比于常规基于刚性桁架假设的预张力设计，该方法可充分计及环形桁架与柔性索网协调变形，获得高精度反射面，且该方法适用于非对称偏馈天线，可有效避免后期张力调试，节约人力物力。算例分析验证了在进行预张力设计时计及桁架柔性的必要性及方法的正确性和有效性。     

Robust extension of the simple sea-surface irradiance model to handle cloudy conditions for the global ocean using satellite remote sensing data

Sea-surface solar radiation (abbreviated as photosynthetically available radiation, PAR) in the visible wavelength (400–700 nm) is an essential parameter to estimate marine primary productivity and understanding phytoplankton dynamics, upper ocean physics and biogeochemical processes. Although many remote-sensing models were developed to estimate daily PAR (DPAR) from ocean colour data, these models often produce biases in the DPAR products under cloudy-sky and complex atmospheric conditions due to the lack of parameterization to deal with the cloud cover conditions and insufficient in-situ DPAR data. This study presents an Extended Sea-surface Solar Irradiance Model (ESSIM) for estimating DPAR over the global ocean. The ESSIM uses the direct and diffuse components from the Simple sea-surface Solar Irradiance Model (SSIM) along with a new parameter to handle cloudy conditions. The ESSIM produced DPAR products with greater accuracy under both clear and cloudy conditions. Its performance was tested on the time-series MODIS-Aqua images and compared with the concurrent in-situ data and the results from two global models. Results showed that the DPAR values produced by ESSIM agree with in-situ data better than the global models for all-sky conditions (with a mean relative error of 11.267 %; a root mean square error of 5.563 Em^?2day^?1; and a mean net bias of 2.917 Em^?2day^?1). The ESSIM performed slightly better than the SSIM for clear conditions and the Frouin's Operational Algorithm (FOA) for all-sky conditions. As the new parameterization accounts for cloudy conditions, the ESSIM produced more accurate results for cloud cover conditions across latitudes (up to 60°). The time-series Level-3 binned MODIS-Aqua data (global gridded) also demonstrated that the ESSIM improved the accuracy of DPAR products and produced spatially and temporally consistent DPAR products over the global ocean regardless of the seasons and sky conditions.     

不同尺度范围的监测网对星基增强服务性能的影响分析

区域监测站提供的星基增强完好性监测服务在民用航空等生命安全领域发挥着重要作用。为了分析利用不同尺度监测网估计的完好性信息对用户服务性能影响,使用等效钟差方法分别实现三种不同尺度的监测网完好性参数估计,并进行增强定位验证。从增强卫星数目、用户测距误差、定位精度和保护级包络特性方面研究不同尺度的监测网对用户服务性能评估的影响,结果表明:与小尺度和中等尺度区域相比,大尺度区域增强卫星数目分别增加了50.7%、33.7%。与广播星历伪距单点定位相比,基于小、中等和大尺度区域监测网估计的改正数增强定位在水平方向定位精度分别提升了33.08%、33.59%和32.54%,垂直方向定位精度分别提升了36.56%、41.07%和43.86%。三种尺度估计的平均用户测距误差均优于0.3 m,保护级水平对定位误差的包络均能达到95%。研究成果可为区域星基增强监测网的选择提供理论支撑和应用依据。