A New Population of the Cusp Suprathermal Protons Formed at Mid-Altitudes: INTERBALL-2 Measurements

A new population of dispersed suprathermal ions descending into the ionosphere is discovered in the cusp region from theINTERBALL-2 measurements at altitudes of 2–3R _E. The proton energies of the population are below the low energy cut-off of the main dispersed proton population of the magnetosheath origin, and its intensity and density are also much lower. For IMF B _z 2 nT the region of the population observations is located partly coincident with (or sometimes poleward from) the main proton population of the cusp proper. The pitch-angle velocity dispersion in the population during a 2-min satellite rotation manifests itself as a typical pitch-angle V together with a velocity dispersion due to poleward convection. The satellite passes chosen for the detailed analysis and modeling lay approximately along the cusp/cleft band from afternoon till prenoon MLT sectors, thus emphasizing the pitch-angle dispersion role with respect to the dispersion due to convection. This allows one to observe the suprathermal proton population during several tens of minutes over the MLT range of 3 h around noon, i.e., similarly to the MLT extension of the cusp proper. A remarkable space/time stability of this new population is due to its low velocity (tens of km/s) and/or velocity diffusion in the flux tubes of the cusp proper. We have performed both backward tracing of proton trajectories in the Tsyganenko-96 model, and kinetic modeling of the kinematic variations of the distribution function for protons along their way from the bi-Maxwellian source in the form of a heating wall till the satellite. The parameters of the model were adjusted to the observed energy–time spectrograms. They consistently indicate the origin of the descending suprathermal proton population at intermediate altitudes of 5R _E, i.e., within cusp flux tubes but well below the magnetopause. Some published measurements from the POLAR satellite in the cusp region at altitudes of 4–5R _E seem to be consistent with the supposition of crossing the source region of this population, variable in space and time (though these measurements were interpreted in a different manner).     

Verification of the Accuracy of the Magnetopause Empirical Models Using the INTERBALL-1 Satellite Data

A statistical analysis of the shape and location of the magnetopause according to the INTERBALL-1 satellite data for the period 1995–1997 is carried out. The instants of crossing the magnetosphere boundaries obtained by the plasma and magnetic data are compared with computations based on three empirical models, namely, Petrinec and Russel, 1996; Shue et al., 1997; and Shue et al., 1998. The state of the interplanetary medium (dynamic pressure of the solar wind plasma P _d and the B _z component of the interplanetary magnetic field) was determined by the measurements onboard the WIND spacecraft. We estimate the accuracy of the considered models for different groups of boundary crossings: single, multiple with small duration (less than 40 min), and multiple with large duration (more than 40 min). It is demonstrated that the small-scale motions of the boundary (<1R _E) are observed more often in the dayside magnetosphere, especially near the cusp region. Large-scale boundary oscillations (>1R _E) are more common in the tail region of the magnetosphere, namely, its flanks. Various models give similar results: about 50% of all events have deviations by more than 1R _E from the model locations. In some cases, the deviation of the measured location of the magnetosphere boundary from the model prediction may be as large as 5–6R _E for all three models considered, the actual boundary being more often located nearer to the Earth than the result of model computations. The best model is that of Shue et al., 1998, but it does not differ significantly from the other models.     

Satellite Measurements of Plasma Disturbances and Electric Currents Induced in the Midlatitude Ionosphere Modified by High-Power HF Radio Waves

Cosmic Research - We have analyzed the experimental data obtained in 2016–2019 from the measurements of plasma disturbances and electric currents induced at ionospheric altitudes upon the...     

GEO卫星电推力器安装位置优化研究

针对配置电推力器的地球静止轨道(GEO)卫星,研究了以位置保持效率为指标的电推力器最佳安装位置。分析了南北、东西位置保持所需推力大小与工作时间的关系,得到推力器安装位置与位置保持可控性的定量关系。分析了电推力器安装位置与角动量卸载能力的关系,电推力器的推力方向越接近垂直,角动量卸载能力越大。以位置保持效率为最优目标,考虑卫星尺寸、位置保持可控性和角动量卸载能力等约束条件,给出了电推力器最优安装位置的确定方法:根据位置保持效率及卫星尺寸约束,确定电推力器纵向与垂向安装位置;根据位置保持可控性和角动量卸载能力等约束条件,确定电推力器横向安装位置。利用一个典型优化算例对此方法进行验证,结果表明:该优化方法能够确定满足约束条件下的电推力器最优安装位置,可为GEO卫星电推进系统的布局设计提供参考。     

Fluctuations of Current onto Flat Probes of the ZOND–ZARYAD Instrument Mounted on the MIR Orbital Complex

Flat probes of the ZOND–ZARYAD instrument, which operated on the MIR orbital complex (OC), form a counterprobe (reference surface) configuration in which the alternating component of the net probe current is measured. There is no potential difference between the spacecraft (SC) body and the probes; that is, the probes are at the floating potential (FP). By measuring the alternating component of the probe current, one cannot estimate the FP value, but we can observe small-scale FP dynamics of a single probe in the OC near-surface region and estimate the fluctuations of currents flowing onto the SC. The alternating component of the current on the probes in the OC near-surface region varies in a wide range depending on ionospheric plasma parameters, the probe orientation with respect to the velocity vector, the magnetic field vector, and the direction to the Sun in the illuminated part of the orbit. In addition to the amplitude dynamics, the frequency dynamics of the alternating component of the current onto the probes is observed.     

一种实时测量卫星运动像移的新方法

文章针对高分辨率对地观测卫星 ,介绍一种新的方法来实时测量卫星运动在焦平面上的像移。详细地说明了像移实时测量的原理 ,具体推导了像移测量的数学表达式。测量出的像移可以用来对畸变的图像进行校正 ,获得高质量的图像     

Stationary Nose Structures of Protons in the Inner Magnetosphere: Observations by the ION Instrument onboard the Interball-2 Satellite and Modeling

Nose structures are objects formed by H⁺ particles penetrating into the inner magnetosphere [1, 2]. We present the results of experimental studies and numerical modeling of the nose structures. Statistical processing of the observations of nose structures in 1997 by the ION instrument onboard the Interball-2 satellite at heights of 10000–15000 km demonstrates that the probability of formation of the nose structures under quiet magnetic conditions (with current values K _p = 0–1) in the nighttime sector of the magnetosphere is 90%. The probability of observation of the nose structures in the daytime sector equals 50% at the current value K _p = 0–1, and the correlation between the observations of nose structures and K _p can be improved (up to 75%) if the K _p index is taken 6 h before the observed events. It is shown that nose structures are a characteristic feature not only of the substorm processes but also of quasi-stationary phenomena in the quiet magnetosphere. The nose structures observed in magnetically quiet periods are called stationary nose structures in this work. By modeling drift trajectories for protons, it is shown that the stationary nose structures are formed in all sectors of the MLT. The stationary nose structures observed by the ION instrument are modeled in the night, morning, and daytime sectors of the MLT. The relation between the stationary nose structures and ion spectral gaps is considered.     

基于全球网和区域网SLR数据的低轨卫星定轨精度分析

卫星激光测距(SLR)是目前低轨卫星常用的定轨手段之一.文章以贾森-1(Jason-1)和环境卫星(EN VISAT)实测数据为例,讨论了不同弧段长度(1天、3天和7天)的全球网SLR数据对低轨卫星定轨精度的影响,分析了基于美国网、欧洲网和亚洲网等区域网SLR数据的低轨卫星精密定轨精度.检验定轨精度的参考轨道来自美...     

GEO卫星电推进与化学推进组合变轨方案研究

针对GEO卫星采用电推进和化学推进系统进行变轨的问题,在给定轨道控制模型的基础上,给出实现轨道半长轴、偏心率和倾角3个参数单独调整和联合控制的控制律。结合假设的运载火箭发射能力约束,给出航天器不同入轨高度对应的初始质量。以此为约束,给出化学推进和电推进不同组合的6种GTO向GEO转移方案,并对比分析各方案完成变轨所需的时间、推进剂、速度增量以及完成变轨后的质量剩余情况,研究方法可为电推进系统在航天领域的应用提供参考。     

探针游移对方形四探针测试仪测量硅片薄层电阻的影响分析

分析方形四探针探针游移对其测量微区薄层电阻的影响,完成了测试薄层电阻的公式的推导,对游移后产生的误差影响进行了统计数据分析,得出了测试结果满足测试误差要求的结论.     

探针游移对方形四探针测试仪测量硅片薄层电阻的影响分析

分析方形四探针探针游移对其测量微区薄层电阻的影响,完成了测试薄层电阻的公式的推导,对游移后产生的误差影响进行了统计数据分析,得出了测试结果满足测试误差要求的结论。     

FY-2C星应答机子系统技术改进

阐述了风云二号(FY-2)C星测控分系统应答机子系统的功能,以及载频中心频率、工作体制、接收机输入信号电平、馈线损耗、发射性能和功耗等主要技术指标.给出了子系统的组成和工作原理.介绍了C星应答机的倍频链电路、调制器、选用固态功率放大器(SSPA),以及功率合成器放电余量增大等设计改进.试验验证及在轨运行状况表明,C星应答机工作正常,所作技术改进正确有效.     

FY-2C星地面应用分系统工程建设

介绍了风云二号(FY-2)C气象卫星地面应用分系统的组成、主要任务及建设目标.说明了分系统建设中采用的建立健全两总系统、成立气象卫星工程建设部和建立两总联席会议制度等行政措施.阐明了在分系统建设中采用的软件工程管理开发、加强合同签定审批、不同设备的验收,以及严格选择基础施工单位与聘请施工监理等管理措施.建成的地面应用分系统在C星的业务运行中发挥了重要作用.     

“高分二号”卫星相机热控系统的设计与验证

为了保证相机在轨成像品质和指向精度,相机光机部件的控温要求需全寿命周期温度稳定性优于±0.3℃。文章根据"高分二号"卫星相机在轨成像需求,详细分析了相机热控设计的重点与难点,并创新性的采用了辐射主动控温措施对相机进行高精度的温度控制。热平衡试验和在轨飞行温度数据表明,相机热控设计合理可行,热控措施能够很好的满足在轨成像时所需温度要求,同时证明了辐射主动控温方法具有很好的控温精度和鲁棒性,在未来空间相机高精度、高稳定性热控设计中具有很好的应用前景。     

卫星振动对HY-1卫星步进电机工作状态的影响

为分析海洋一号(HY-1)卫星水色扫描仪(水色仪)在轨发生的转动机构与卫星间耦合振动对步进电机工作状态的影响,根据建立的步进电机 角速度振动环境、步进电机 卫星 太阳帆板两种不同模式的电机运动状态模型,在不同设计参数条件下进行了仿真.结果表明:步进电机会因与卫星耦合振动造成工作状态变差,影响步进电机在轨工作状态的主要因素是卫星结构基频.     

对GEO卫星照相的HEO卫星变轨策略研究

为对地球同步轨道卫星近距离光学照相,设计了大椭圆任务轨道.在考虑地球扁率J2的动力学模型下,研究了大椭圆轨道变轨策略,提出了轨道设计方案,并进行了仿真计算.基于STK软件对变轨方案进行了仿真验证,结果表明所提出的轨道设计方案能够满足对地球同步轨道卫星近距离光学照相要求.     

“高分二号”卫星在西藏矿山遥感监测中的应用研究

西藏自治区海拔高、地形起伏大,利用优于1m分辨率卫星影像监测当地的矿业开发活动存在较多难点。文章以墨竹工卡重点矿集区为例,通过影像的正射校正、融合镶嵌、几何校正、信息提取等处理工作,完成了基于高分二号(GF-2)卫星影像的1∶1万比例尺矿山遥感监测工作。通过与国际多元多尺度卫星影像的对比研究,GF-2卫星影像对于开采硐口的识别、开采面及开发占地性质的确定、水体污染现象的识别等矿山开发信息提取的准确率有了明显提高,完全能够满足1∶1万尺度矿山遥感监测技术要求,在替代国际同等分辨率商业卫星数据的同时,亦可节省大量的野外验证工作,具有显著的社会经济效益。     

卫星控制系统故障仿真技术研究

首先分析卫星控制系统可能发生故障的各种原因、现象及防止故障的各种措施,讨论仿真技术在卫星故障诊断和对策中应用,然后介绍卫星故障仿真的工具－卫星飞行控制模拟系统。     

国外卫星星座自主运行技术发展综述

综述国外卫星星座自主运行技术的研究和发展情况,重点介绍了导航星座、移动通信星座和区域覆盖星座的自主导航和自主轨道控制技术的发展现状,并对实现星座自主控制的关键技术进行了分析。这为我国发展星座自主控制技术提供参考。     

FY-2C星辐射致冷器太阳屏研制

在风云二号(FY-2)01批气象卫星的基础上,为提高辐射致冷器(以下简称辐冷器)的性能,对C星辐冷器太阳屏进行了改进.根据太阳屏保护膜厚度和翻边白漆等表面特性对辐冷器性能的影响,通过控制保护膜厚度和改用耐紫外光的KS-Z无机漆等以改善C星太阳屏表面特性.地面试验和在轨测试结果表明,C星辐冷器温度和制冷量均在理论计算范围内,太阳屏技术改进有效.