利用微波探测仪(ATMS)对在轨微波辐射计观测精度的模拟分析

微波辐射计的观测精度及其对数值模式同化应用的影响评估是微波辐射计观测指标设计的重要参考。基于微波探测仪(ATMS)资料,利用三维变分同化系统模拟分析在轨微波辐射计的观测精度指标。针对ATMS观测误差特征,在其观测基础上增加均值为零、标准偏差分别为0.5,1.0,1.5,2.0K的正态随机扰动,进而获得不同精度的观测模拟值序列,然后利用Harris和Kelley的辐射资料偏差订正经验方法订正不同精度的观测资料。偏差订正后,利用三维变分同化模式(WRFDA)直接同化ATMS资料。通过2016年6月6h预报场的同化试验,评估了不同观测精度的模拟资料对数值模式的同化影响。     

电子对抗事件建模方法在危机预测中的应用

提出了一种用于危机预测的电子对抗事件建模方法,该方法主要使用电子目标参数特征、行为特征和环境特征进行危机事件建模.利用事件模型和电子侦察数据进行事件情报处理,能够有效提高电抗情报处理水平和危机预测能力,实现电抗情报从数据层向认识层的提升.通过仿真数据实现了危机事件预测,验证了该方法的有效性.     

三维射击精度的一阶逼近评估方法

在提出导弹武器三维射击精度参数自助评估方法之后,进而推出了三维射击精度的一阶逼近评估方法,它与参数自助法的研究思路有很大不同。一阶逼近法基于函数变换和极限分布理论,利用正态分布的特性,使用球概率误差SEP对分布参数的一阶偏导数来构造SEP的置信上界和置信区间。通过实例证明,一阶逼近法具有良好的应用前景。     

气象卫星智慧观测需求与设想

随着日益加剧的全球气候变化引发的气象灾害频发和生命财产损失影响的扩大,要求未来的气象卫星观测系统通过自主星上处理、自主任务规划、星间互联互通等智慧观测手段实现快速响应、精准预报、提前预警和连续跟踪。为此,文章以我国第二代静止轨道气象卫星风云四号(FY-4)为例,结合数值天气预报和短临天气预报等业务需求,提出了包括多载荷自主协同观测、定位恒星自主预报、自主太阳规避等智慧观测的设想和实现技术途径,通过气象卫星智慧观测可有效提升卫星应用效能,更好地发挥气象卫星数据服务能力。     

XNAV算法及其整周模糊度确定方法研究

X射线脉冲星导航(XNAV)是一种新型的航天器天文导航方法.研究了利用脉冲星脉冲相位观测信息进行导航卫星自主定轨的算法.首先分析了X射线脉冲在卫星和太阳系质心之间的传播时间方程,然后利用卫星与太阳系质心之间的相位差分观测量建立了系统的观测方程;结合导航卫星的轨道动力学特性,采用扩展卡尔曼滤波算法估计卫星的轨道.考虑到卫星轨道动力学预报得到的卫星位置值具有较好的精度,提出直接利用该位置预报值快速确定整周模糊度,并验证了该方法的可行性.数学仿真表明,该导航算法能够精确确定导航卫星在 l惯性系F的绝对位置.     

在轨物体碰撞预报的并行算法

2009年美俄卫星意外相撞事件显示:目前在轨的卫星已经相当拥挤,相互碰撞的危险不再可以忽视.预报在轨物体的碰撞,不仅需要更完善准确的观测数据,也需要更完善准确的环境模拟计算模型.在"怀疑-确认"策略的基础上讨论了在轨物体碰撞预报计算的并行算法,从计算的时间复杂度评估,现有的并行计算能力可以进行卫星碰撞危险预报.     

2023年12月地磁暴事件的初步分析

2023年12月1日在我国北方地区观测到的绚烂极光,是一次强地磁暴的伴生现象。我们结合卫星在轨探测的实时数据和数值模拟结果,首先对本次地磁暴事件的触发原因和演化过程进行了梳理和分析,然后对其的潜在影响进行初步评估,最后对我国即将发射的空间探测卫星“太阳风-磁层相互作用全景成像”进行简要介绍。     

一种基于数字空间的空间站任务飞控事件规划方法

针对空间站任务飞控事件规划问题,结合资源约束、飞控事件需求数据维度高、事件间互相影响等特点,提出一种基于数字空间的飞控事件规划方法,将飞控事件规划问题转化为数字模型构建、数值计算及飞控事件时序设计问题。结合空间站应用实例,给出了飞控事件规划流程和规划结果分析,验证了方法的有效性,为空间站任务飞控事件规划问题提供了新思路。     

天基空间监视交会计算和可观测时段预报的误差分析

将卫星和目标的轨道预报误差引入天基空间目标监视的任务规划中,研究了交会计算和可观测时段预报的误差分析方法。在协方差转换基本方法和交会信息计算公式的基础上,推导了从RSW轨道坐标系到RAE参数（距离、方位角、俯仰角）的协方差转换方法。对LEO和GEO目标观测分别引入相对速度和角距变化率,给出了可观测时段误差的分析方法。算例表明本文的计算结果与Monte-Carlo仿真结果相对误差不大于4%,典型轨道误差下LEO和GEO目标的可观测时段误差分别为0.2秒和3秒量级。该方法对任务规划和姿态及相机导引具有指导意义,还可用于分析成功观测对轨道预报精度的需求。     

航天器观测重调度问题中的模糊性不确定因素及其处理

为了处理航天器观测问题中具有模糊性特点的不确定因素,解决动态环境下的航天器观测重调度问题,提出了一种基于模糊神经网络的处理方法.该方法通过参数模糊化和径向基神经网络来评估模糊性不确定因素对系统造成的影响程度,同时将重调度响应划分为立即型、延迟型和忽略型三种类型,以处理不同影响程度的不确定事件.最后通过算例说明了所提出的模糊神经网络算法的有效性.     

太阳高能粒子在行星际中的扩散过程

当太阳活动频繁,特别是有耀斑爆发或者日冕物质抛射驱动的激波时,经常能够观察到高能粒子(能量从几十keV到几十MeV)通量突然增加,这种由太阳活动产生的高能粒子事件被称为太阳高能粒子事件。文章研究了耀斑和日冕物质抛射产生的两类高能粒子事件,重点讨论了高能粒子横越磁力线的扩散对粒子在行星际空间传播过程中所起到的作用,给出了对于不同扩散系数条件的数值模拟结果。     

Solar cycle variation of “killer” electrons at geosynchronous orbit and electron flux correlation with the solar wind parameters and ULF waves intensity

To construct models for hazard prediction from radiation belt particles to satellite electronics, one should know temporal behavior of the particle fluxes. We analyzed 11-year variation in relativistic electron flux (E>2 MeV) at geosynchronous orbit using measurements made by GOES satellites during the 23rd sunspot cycle. As it is believed that electron flux enhancements are connected with the high-speed solar wind streams and ULF or/and VLF activity in the magnetosphere, we studied also solar cycle changes in rank order cross-correlation of the outer radiation belt electron flux with the solar wind speed and both interplanetary and on-ground wave intensity. Data from magnetometers and plasma sensors onboard the spacecraft ACE and WIND, as well as magnetic measurements at two mid-latitude diametrically opposite INTERMAGNET observatories were used. Results obtained show that average value of relativistic electron flux at the decay and minimum phases of solar activity is one order higher than the flux during maximum sunspot activity. Of all solar wind parameters, only solar wind speed variation has significant correlation with changes in relativistic electron flux, taking the lead over the latter by 2 days. Variations in ULF amplitude advance changes in electron flux by 3 days. Results of the above study may be of interest for model makers developing forecast algorithms.     

Some features of solar cosmic ray penetration into the Earth’s magnetosphere

We compared fluxes of the 1–100 MeV solar energetic particles (SEP) measured in the interplanetary medium (ACE) and in the magnetosphere (Universitetsky-Tatiana, POES—in polar caps, and GOES-11—at geosynchronous orbit) during several SEP events of 2005–2006. Peak intensities of the SEP fluxes inside and outside the magnetosphere were compared for each event. It is shown that observed inside-outside difference depends mainly on direction of interplanetary magnetic field (IMF), on degree of the SEP anisotropy (pitch-angle distribution) in IMF, and on distance of the dayside magnetopause from the Earth.     

Intermittency of solar wind density fluctuations and its relation to sharp density changes

The paper presents the study of turbulent properties of the solar wind plasma, namely, the intermittency of fluctuations of the solar wind ion flux in the earlier unexplored region of comparatively high frequencies (0.01–1 Hz). Special attention is given to a comparison of intermittency for solar wind observation intervals containing sharp (shorter than 10 min) and high-amplitude (greater than 20%) changes of the ion flux to intervals without such changes. The solar wind observation intervals containing sharp changes of the flux are found to be essentially more intermittent than the intervals of quiet solar wind. Such a comparison allows one to reveal the fundamental difference in turbulent properties of the solar wind depending on the presence or absence of sharp boundaries in plasma structures.     

Motion and transport of solar cosmic rays in heliospheric traps: The event on January 28–31, 2001

The results of studying the enhancement of solar cosmic ray fluxes on January 28?C31, 2001 in a wide energy range are presented using the ACE spacecraft data. A comparative analysis of temporal variations of the fluxes of charged particles and of the interplanetary medium parameters (interplanetary magnetic field and solar wind) has been performed on the basis of the ??reflection?? model of motion, accumulation, and modulation of cosmic rays. It is shown that a magnetic trap for solar cosmic rays was created by a plasma stream and flare ejection from an active region in the western part of the solar disk. Particles of low energies (<10 MeV) were captured inside the trap; the dispersion of distribution of particles with different energies inside the trap being determined by its complicated magnetic structure. The power-low dependence of the time of maximum for the flux of particles on their energy is found, and softer energy spectrum inside the trap is explained.     

Characteristics of the decay phase of proton fluxes in solar events as a function of observer’s heliolongitude

Events in energetic solar protons with the energy > 4 MeV at the stage of their decay are considered for the period from 1974 to 2001. It is shown that in the events with the exponential shape of decay for west flares (relative to the observation point), the characteristic decay time τ and the power index γ of the energy spectrum decrease with an increase in the angular distance between the observer and the source of the particles on the Sun, while this effect is absent for east flares.     

Sequences of Solar Events with Identical Decays as a Tool for Isolating Quasistationary States in the Interplanetary Space

Time profile of the fluxes of energetic solar particles generated by solar flares (including their phase of decline) is formed to a large extent by the structure of the interplanetary magnetic field and its irregularities that move away from the Sun with the solar wind velocity. When propagation is a pure diffusion, the solar particle fluxes decay after the maximum in a power-law manner. At the same time in many cases this decay is exponential, which is indicative of a considerable role played by the convective sweep of particles and their adiabatic deceleration in the expanding solar wind. In this paper we consider the events with long exponential decays and newly discovered series of successive events with identical exponential decays lasting for one to two weeks or more. They allow us to assume that the interplanetary space is stable and homogeneous during this period.     

Modeling of Ejecta Produced upon Hypervelocity Impacts

Each time a debris particle or a meteoroid strikes a satellite in orbit, a great amount of secondary particles is ejected in the neighborhood of the impact site. This phenomenon is important in particular for brittle materials, such as those used for solar arrays or thermal control paint. The secondary particles that do not impact other parts of the spacecraft are added to the primary debris population and hence increase the small debris particle flux. We describe an ejecta production model that gives the size and the velocity distribution of ejected particles as a function of primary impact parameters. The model has been used to explain the discrepancy between measurements and modeling of impact crater distribution on the solar arrays of the EuReCa spacecraft.