Magnetospheric and ionospheric manifestations of interplanetary foreshocks

The geometry of a typical interplanetary shock front in the vicinity of the Earth’s orbit predicts that the leading edge of the foreshock region comes into contact with the magnetosphere a few hours ahead of geomagnetic sudden impulses (SI). There is reason to believe that the interaction of the magnetosphere with the foreshock leads to magnetic and ionospheric disturbances, which can be detected by ground-based instruments. We searched for specific precursors of SIs in data from the Scandinavian riometer network and in the short period geomagnetic pulsation data from mid-latitude magnetometers. We found that SIs were preceded by the following three features: (1) an increase in riometric absorption, (2) excitation of Pcl magnetic pulsations and (3) a spectral broadening of the Pc3 magnetic pulsations. Our observations may be useful for the study of acceleration processes in the solar wind. These observations are also of potential forecasting interest.     

航天器太阳电池阵热真空试验技术

文章叙述了进行太阳电池阵热真空试验的重要性、一般要求及相关的主要试验技术.     

双损耗Al2O3基多孔吸波材料的制备及其吸波性能

基于片状Al₂O₃陶瓷互锁结构强度高的特点,制备出夹杂石墨的高气孔率的Al₂O₃多孔陶瓷,并通过原位还原在多孔骨架中制备出Ni微粒,形成一种轻质的双损耗陶瓷基吸波材料。通过XRD、FE-SEM和EDS研究了还原温度对多孔吸波材料的组成、微观形貌、元素分布和吸波性能的影响。结果表明,还原温度升温至700 ℃可将多孔网络中Ni完全还原,形成以堆叠互锁Al₂O₃为基,夹杂片状石墨和孔表面覆盖Ni微粒的双损耗轻质吸波材料。当复合材料厚度为6.5 mm时,最小反射损耗为-35.01 dB,有效吸收带宽达到1.75 GHz。片状Al₂O₃锁定的石墨片构筑的导电网络,Ni微粒与基体之间的极化效应等共同促进复合材料良好的微波吸收性能。     

连续型和非连续型蜂窝芯材的共振吸声结构性能研究

以芳纶纸蜂窝、内嵌树脂隔板和微穿孔面板为原料,制备了连续和非连续双自由度共振吸声结构,对两种共振吸声结构的力学性能和吸声系数进行对比研究。结果表明：连续蜂窝芯材所制备共振吸声结构的压缩和拉伸性能高于非连续型共振吸声结构,其中非稳定型压缩强度和拉伸强度高19%,稳定型压缩强度高32%,稳定型压缩模量高43%,剪切性能基本相当;两层蜂窝芯材容易出现孔格错位（非连续型共振吸声结构）,引起错位区域的微孔堵塞,使该结构的共振吸收峰与理论值出现较大差异。     

Low-velocity impact response and infrared radiation characteristics of thermoplastic/thermoset composites

The low-velocity impact response and infrared radiation characteristics of composites have rarely been focused on simultaneously. This study aims to investigate the low-velocity impact response and infrared radiation characteristics of the glass fiber reinforced thermoplastic polypropylene and carbon fiber reinforced thermosetting epoxy resin laminates wildly used in the aircraft industry. The impact tests were conducted at five energy levels. Characterization parameters such as impact load, displacement, and absorbed energy were measured. The damage evolution and damage modes of the laminates were analyzed through active and passive thermography, ultrasonic C-scan, and optical microscope. The results indicate that Thermosets (TS) laminates exhibit better impact resistance, while Thermoplastics (TP) laminates show higher delamination ductility, and the maximum contact force of TP laminates is much smaller than that of the TS laminates under low-velocity impacts, but the low bending stiffness and low ductility of the TP matrix cause the difference in energy absorption level between the two not significant. The temperature characteristic changes of passive infrared thermography heat maps could characterize the damage mode of the laminates. The correlation between the heat maps and the impact characteristic curves is explained; the fluctuation of the impact characteristic curves is directly related to the hot spot characteristics changes of the heat maps. More frequent curve fluctuations correspond to a larger and brighter hot spot on the heat map, which peaks at the maximum impact load after the impact force versus time curve fluctuation cutoff point, the maximum center displacement of the impact force versus displacement curve, and the maximum absorbed energy of the absorbed energy versus time curve.     

红外地平仪摆动扫描装置自适应控制器的FPGA实现

本文介绍了红外地平仪自适应摆动控制器ＦＰＧＡ原理样机的有关研制结果。针对新型长寿命红外地平仪的摆动扫描控制装置，基于系统特征分析，提出了能跟踪摆动装置的固有频率、同时保证摆幅稳定的一套自适应控制方案，并且研制出ＦＰＧＡ芯片原理样机，最终通过了实验验证并得到满意的实验结果。     

基于局部能量比的空中红外弱小目标检测方法

提出了图像局部能量比的概念,并针对空中目标图像特点,给出了一种基于局部能量比的红外弱小目标检测方法。该方法基于单帧图像即可实现红外点目标检测,算法简单,耗时较短,可以实时检测;图像局部能量比对图像噪声不敏感,故该检测方法对图像信噪比要求较低,具有强抗干扰性,便于工程实现。文中给出了检测算法的具体实现过程,并用真实空中红外弱小目标图像进行了检测试验。试验结果表明该方法对空中红外弱小单目标和多目标均具有令人满意的检测效果。     

在轨地球同步卫星地球敏感器干扰及指向计算

从工程应用角度,基于太阳、月球位置和卫星轨道根数推导了太阳和月球对地球同步轨道卫星红外地球敏感器干扰的计算公式及预报方法,同时给出了安全模式下卫星Z轴跟踪太阳时星上天线指向变化的计算模型。计算结果和卫星下传遥测数据验证了方法的正确性,可用于实际卫星管理。     

利用奉献观测器诊断红外地球敏感器故障的新方法

卫星闭环控制系统中不同敏感器的故障定位是自主故障诊断的难点。基于双观测器的方法能够分离光学敏感器和惯性敏感器的故障,却仍不能确定红外地球敏感器是否发生故障。奉献观测器适用于敏感器系统的故障定位,但由于该方法要求的能观性条件在实际工程中有时难以满足,使其应用受到限制。本文提出了一种利用奉献观测器诊断敏感器故障的新方法,先对不完全能观系统进行能观性分解,再对能观子系统设计奉献观测器,克服能观性条件的限制,实现敏感器故障诊断。最后,将该方法用于卫星红外地球敏感器的故障定位,仿真结果表明,该方法可有效诊断地球敏感器的故障。     

红外地球敏感器的高截止度新型红外滤光片的设计

高截止度新型红外滤光片是三轴稳定卫星红外地球敏感器的关键件之一。文章介绍了用等效折射率概念设计这种滤光片的方法 ,讨论并给出了膜系设计和研制的结果 ,简介了镀膜的工艺技术 ,并与国内外同类滤光片的光学特性进行了比较 ,试验表明新型红外滤光片的膜系设计是成功的。