一种2π视场高分辨热等离子体分析仪设计与仿真

针对空间热等离子探测中大通量动态范围、宽视场和高分辨率的需求,以带顶盖球形静电分析器为基础设计了2π视场热等离子体分析仪(Hot plasma analyzer, HPA),探测性能得到显著提升。通过优化球形剖面视场偏转系统以及粒子光学系统,实现对热等离子体的2π视场高角度分辨率探测,可探测能量范围覆盖50 eV~20 keV,能量分辨率优于10%。利用顶盖电压控制方式实现几何因子在两个量级内连续可调,可以满足对太阳风和磁层热等离子体的全空间高分辨探测需求。     

Studies of electron and ion temperatures at 500 km altitude during sunrise using Indian SROSS C2 satellite

Solar dependence of electron and ion temperatures (T_e and T_i) in the ionosphere is studied using RPA data onboard SROSS C2 at an altitude of ∼500 km and 77°E longitude during early morning hours (04:00–07:00 LT) for three solar activities: solar minimum, moderate and maximum during winter, summer and equinox months in 10°S–20°N geomagnetic latitude. In winter the morning overshoot phenomenon is observed around 06:00 LT (T_e enhances to ∼4000 K) during low-solar activity and to T_e ∼ 3800 K, during higher solar activity. In summer, it is observed around 05:30 LT, but the rate of T_e enhancement is higher during moderate solar activity (∼2700 K/hr) than the low-solar activity (∼1700 K/hr). During equinox, this phenomenon is delayed and is observed around 06:00 LT (∼4200 K) during all three activities.     

An evaluation of the IRI-2007 storm time model at low latitude stations

This paper discusses the ability of the International Reference Ionosphere IRI-2007 storm time model to predict foF2 ionospheric parameter during geomagnetic storm periods. Experimental data (based on availability) from two low latitude stations: Vanimo (geographic coordinates, 2.7 °S, 141.3 °E, magnetic coordinates, 12.3 °S, 212.50 °E) and Darwin (geographic coordinates, 12.45 °S, 130.95 °E, magnetic coordinates, 22.9 °S, 202.7 °E) during nine storms that occurred in 2000 (Rz₁₂ = 119), 2001(Rz₁₂ = 111) and 2003 (Rz₁₂ = 64) are compared with those obtained by the IRI-2007 storm model. The results obtained show that the percentage deviation between the experimental and IRI predicted foF2 values during these storm periods is as high as 100% during the main and recovery phases. Based on the values of “relative deviation module mean” (RDMM) obtained (i.e. between 0.08 and 0.60), it is observed that there is a reasonable to poor agreement between measured foF2 values and the IRI-storm model prediction values during main and recovery phases of the storms under investigation. As a result, in addition to other studies that have been carried out from different sectors, more studies are required to be carried out. This will enable IRI community to improve on the present performance of the model. In general the IRI-storm model predictions follow normal trend of the foF2 measured values but does not reproduce well the measured values.     

Statistical properties of variability of the quiet ionosphere F2-layer maximum parameters over Irkutsk under low solar activity

The statistical analysis of the quiet ionosphere F2-layer maximum parameters variability (deviations of NmF2 and hmF2 from the quiet medians, δn and Δh) under solar minimum at day (10–16 LT) and night (22–04 LT) hours based on data of Irkutsk station for 2007–2010 is presented. It is found that the experimental distribution (histogram) of δn can be approximated by a mixture of two normal distributions. The first and second components of the mixture characterize, mainly, relatively weak and strong fluctuations of δn which are presumably associated with the ionospheric effects of the atmospheric gravity waves and of the planetary waves and tides correspondingly. Deviation of the δn histogram from a single normal distribution is most considerable at night hours in winter and equinoxes. For these conditions the weak fluctuations of δn are mainly negative and the strong ones are mainly positive. The Δh histogram is a normal distribution except day hours in winter and equinoxes when a weak deviation of the histogram from the normal distribution occurs.     

On the application of Exploratory Data Analysis for characterization of space weather data sets

This paper presents an overview of the mathematical foundations for techniques in Exploratory Data Analysis (EDA) for the purpose of investigating the relationships among the numerous variables in large sets of multivariate space weather data. Specifically, we cover techniques in Principal Components Analysis (PCA) and Common Factor Analysis (CFA). These techniques are illustrated using space weather activity indices collected during the year 2002 and the corresponding noon-time hmF2 data from the International Reference Ionosphere (IRI). A CFA is used to categorize the activity indices, and a PCA is used to derive two macro-indices of activity to ascertain the strength of solar and geomagnetic activity. These macro-indices are then used to compare and contrast IRI’s noon-time hmF2 values at six different geographic stations. It was found that the correlation between hmF2 and the macro-indices more accurately represented the variation of this correlation with latitude found in previous studies than if we used an isolated conventional index, such as SSN and AE. We also found that the daily maximum value of the Polar Cap Index was dependent on both solar and geomagnetic activity, but the closely-related cross-Polar Cap Potential was solely associated with elevated levels of geomagnetic activity, which is a unique result compared to previous studies. We argue that the discrepancy can be explained by the difference in experiment designs between the two studies. This paper demonstrates the usefulness of EDA in space weather studies of large multivariate data sets.     

Metallic and Oxidized Aluminum Debris Impacting the Trailing Edge of the Long Duration Exposure Facility (LDEF)

A total of 87 microcraters >30 m in diameter that were found in gold substrates exposed on the trailing edge of the non-spinning Long Duration Exposure Facility (LDEF) yielded analyzable projectile residues in their interiors. Using qualitative SEM-EDS analysis methods, some 60 of these craters were formed by natural cosmic-dust particles, while 27 residues (31%) were assigned to orbital debris (Hörz et al., 1993). The far majority of the orbital-debris impacts, 24 (89%) of the 27 events, contained only aluminum in their X-ray spectra. The present study evaluates these aluminum-rich residues in detail and employs a windowless X-ray detector, which permits for the analysis of low-Z elements and specifically of oxygen. This makes it possible to discriminate between oxidized (Al₂O₃) and metallic (Al) projectiles from dramatically different sources, the former produced during solid-fuel rocket firings, the latter resulting from explosively or collisionally disrupted spacecraft.Of the 24 craters analyzed with the windowless detector, 13 (54%) contained Al₂O₃ and 11 (46%) yielded structurally disintegrated Al metal. The oxidized residues preferentially occur in the smaller craters, all <60 m in diameter. Corresponding particles on LDEF's trailing edge are <35 m in diameter. Some 70% of this particle population is composed of Al₂O₃. Although solid-fuel rocket exhaust products are typically <5 m in size, they tend to coagulate into crusts at the rocket nozzle to be shed occasionally as relatively large, aggregate particles. Structurally disintegrated, metallic fragments compose one-third of all particles <35 m, but they dominate all particles >35 m, and thus all craters >60 m. These findings clearly establish that solid-rocket exhaust particles, as well as explosively or collisionally produced debris, exist in low-inclination, high-eccentricity orbits in sufficient quantities that they must be accounted for in models describing the present and future orbital-debris population at typical Shuttle and Space Station altitudes.     

FY-2C星发射轨道计算与分析

根据卫星发射窗口的一般性和风云二号(FY-2)C气象卫星特定限制条件,计算了2004年10月19日符合要求的发射窗口.在比较上午和晚上发射窗口的基础上,确定C星选择上午发射窗口.给出了影响卫星定点捕获所需速度增量的入轨轨道参数和点火姿态等因素,并仿真计算了轨道半长轴、近地点高度、倾角和近地点幅角与速度增量的关系.分析结果表明,卫星发射窗口的确定与星、地、日间的位置密切相关.入轨偏差越小,定点捕获所需肼燃料消耗也越少.     

FY-2卫星功率合成器低气压放电和微放电预防

阐述了星载无源大功率部件发生微放电和低气压放电的原因.讨论了提高风云二号(FY-2)卫星测控系统中功率合成器低气压放电阈值的方法,并提出增大内部间隙、提高器件内表面洁净度和改进调谐螺钉设计等措施.实验结果表明,功率合成器放电容量由4.5 W提高至9 W,从而大幅改善了其低气压临界工作状态.     

FY-2C星业务运行调度管理

介绍了风云二号(FY-2)C星系统运行控制中心(SOCC)的组成和功能,阐述了C星业务测控与管理、特殊事件预报与控制,并说明其采用的全系统集中控制、卫星业务运行自动调度、卫星测控流程控制、应用系统作业流程,以及系统设备运行监视与控制等调度控制方式.与01批相比,C星SOCC的系统结构与功能有较大改进,由原分散式功能单-的调度改为集中式监视和控制能力强大的"大运控"系统.该系统集中了卫星控制、整个地面业务系统调度安排、各种作业调度管理、地面设备切换控制、产品处理软件调度,以及产品分发等各种功能,具有-定的先进性.     

“高分一号”卫星PMS图像几何定位精度验证

卫星影像定位精度的验证是支撑卫星业务化运行和应用的基础性工作,文章测试了“高分一号”卫星PMS相机全色（PAN）二级产品和多光谱（MSS）二级产品几何定位精度。测试结果表明,卫星PMS相机全色测试数据的平均定位精度为27.9m,其中,平原、山区测试数据最大外部几何定位精度分别为16.4m、53m;多光谱测试数据的平均几何定位精度为23.2m,其中,平原、山区测试数据平均外部几何定位精度分别为10m、49.7m。“高分一号”卫星 PMS 相机全色与多光谱二级产品的定位精度满足1？10万比例尺地形图更新要求,其中平原地区二级产品精度能满足1？5万比例尺地形图更新要求。