航天器磁环境试验研究进展

正1引言地球与星际空间的磁环境是影响航天器运行的重要环境之一,其影响程度与航天器自身的磁性大小有关。为满足各种性能要求,航天器需要使用一定量的磁性材料并存在一定的磁场。外界磁场的变化会引起航天器自身磁特性参数的改变,例如科学探测卫星,特别是进行磁场研究的卫星,要对卫星自身磁场加以限制,尤其是磁场监测器安装部位的磁场强度和稳定性的限制,才能保证探测数据的可靠性。对利用磁力矩器进行姿态控制和轨道定位的航天器,需要充     

空间引力波探测惯性传感器关键技术与进展

空间引力波探测任务中的核心科学载荷之一是惯性传感器，旨在探测极其微弱的空间引力波的波纹变化。首先介绍了空间惯性传感器的探测机理和工作原理；然后从电容位移传感、静电反馈控制、地面评价3个方面介绍了惯性传感器设计的关键技术；并且对国内外惯性传感器的发展研究现状进行了梳理，可以看到惯性传感器关键指标为残余加速度噪声，国外在该指标上达到3×10^-15m/s²/Hz^1/2,国内与国外存在着3个量级的差距，因此开展高精度空间惯性传感器研究与设计具有重大战略意义和科学意义，是中国有望赶超世界科技前沿或领跑世界科技研究的重要方向之一。面向中国未来空间引力波探测任务中的惯性传感器需求，可以聚焦于惯性传感器控制体制策略、交流执行机参数优化、多自由度解耦控制技术、低噪声技术这四个方面的研究。     

基于FEM的引力参考传感器自引力计算与补偿

空间引力波探测太极计划将利用激光干涉的方法,测量两个检验质量之间的距离变化反演引力波信息。在0.1 mHz处,要求检验质量在敏感轴方向的总残余加速度保持在■以下。由航天器载荷静引力、热形变和质量波动引起的自引力噪声是检验质量的残余加速度噪声主要来源之一,要求检验质量在敏感轴方向的自引力加速度小于1×10^-10m/s²,引力梯度小于5×10^-8s^-2。为了计算检验质量处的自引力大小和引力梯度,针对检验质量与引力源几何形状的不规则性,基于有限元法编写程序计算了引力参考传感器中的引力源作用在检验质量上的线加速度、角加速度和引力梯度。为了缩短计算时间,提出“类自适应”网格划分方法以减小网格数量,并设计了配重以补偿自引力。计算结果显示,经过补偿后的检验质量在敏感轴方向的自引力加速度为9.237 7×10^-12m/s²,引力梯度为-2.569 1×10^-8s^-2,满足设计要求。本研究能够为航天器和引力参考传感器的设计与引力补...     

基于矢量磁强计的磁场梯度张量仪误差校正方法

卫星在轨运行时，本体会产生一定的磁干扰，一般通过伸杆将传感器远离卫星本体安装，或者通过多个磁场传感器测量磁场梯度的方法来消除卫星本体的磁干扰.使用磁场梯度张量仪测量磁场梯度时，张量仪本身的构型会给测量带来误差.通过对5种主要的张量仪构型进行误差仿真，对比5种构型的张量测量误差，发现十字形构型张量仪的测量误差最小.除了构型带来的误差，张量仪的主要测量误差还包括组成张量仪的三轴磁强计本身的误差和非对准误差.本文使用椭球拟合算法对磁强计本身的误差进行校正，校正后磁强计测量总场的均方根误差为0.864nT.针对张量仪的非对准误差，提出了正交系间非对准误差的校正方法.仿真结果表明，校正后的非对准角度误差≤3.2×10-5 rad，能够很好地降低张量仪的非对准误差.      

相位差法测量磁传感器阵列的非平行度

随着磁传感器技术及磁测技术的发展,通过测量磁梯度张量进行磁探测及磁定位已成为磁探领域的新方法。但在磁梯度张量测量过程中,由于机械安装的误差导致的磁传感器阵列中各传感器的磁轴的不平行将会极大的降低磁定位的精度。本文提出了一种易于实现的磁传感器阵列非平行度测量方法--相位差法,并通过试验验证了其有效性。     

基于巨磁阻抗效应的微型磁传感器技术研究

从非晶丝的巨磁阻抗效应入手, 详细分析了非晶丝巨磁阻抗效应原理及其影响因素, 阐述了基于非晶丝巨磁阻抗效应的传感器工作原理, 并设计了传感器的信号调制电路. 该微型化、低功耗的磁传感器有望应用于空间磁场测量.      

一种用于磁场复现和屏蔽的磁干扰主动补偿技术

介绍了一种交变磁场复现系统和磁屏蔽装置中的环境磁干扰主动补偿方法,分别对主动补偿系统建模、控制参数优化、补偿参数修正、复合控制方法、电流反馈等关键问题进行了阐述,并进行了补偿试验,结果表明,该方法对典型的1Hz和50Hz环境扰动磁场具有显著的补偿效果,已在(10～100)μT/m梯度磁场标准装置、低剩磁低噪声磁屏蔽室等计量装置中得到了应用。     

大型铁磁性物体近场磁异常场数值仿真

磁异常探测是一种在地球物理领域有着广泛应用的探测方法,磁异常场的空间分布规律信息是磁异常探测的主要理论依据。对矩形铁磁性物体空间磁场模型进行了推导,利用ANSYS Maxwell分析了大型铁磁性物体近场的磁异常场空间分布规律。针对不同地磁场方向条件,得到了近场空间磁感应强度总量分布及矢量分布规律,揭示了在不同条件下磁感应强度模量场和矢量场都具有普遍的对称性和规律性。通过对仿真模型进行缩比试验,测量了类似条件下模型近场的磁感应强度模量场和矢量场信息,验证了仿真得到的磁异常场空间分布规律的一致性和正确性。      

用于GMA的新型永磁偏置闭合磁路

利用ANSYS有限元软件进行仿真模拟,对超磁致伸缩执行器(GMA,Giant Magnetostrictive Actuator)的磁路结构进行了分析和优化.根据磁致伸缩棒内磁场均匀性好,场外漏磁小的设计目标,利用极性相反的双永磁补偿原理,提出了一种新型的内置式永磁组合偏置结构,使得沿磁致伸缩棒长方向磁场分布均匀的同时,偏置磁场和激励磁场都形成良好的闭合磁路.ANSYS分析结果表明,棒中偏置磁场不均匀度为3.51%,激励磁场不均匀度为8.73%,均满足不均匀度小于10%的设计目标;在执行器指定位置(距离GMA 7 cm)的总漏磁场强度为30.4 A/m,符合实际应用的标准要求(<80 A/m).     

利用并联氙气瓶温差补偿航天器质心偏移的可行性研究

在以往航天器研制中,一般通过增加配重的方式对航天器质心偏移进行补偿.这种质心补偿方式占用了运载火箭承载能力资源,降低了航天器的有效承载能力.针对常规质心补偿方式的弱点,利用电推进航天器上氙气高密度填充的特点,提出了一种通过氙气瓶温度控制对航天器质心偏移进行补偿的方法,减少了航天器配重的使用需求.氙气瓶温差对航天器质心偏...     

磁通门磁强计校准装置研究

本文介绍了磁通门磁强计校准装置的系统组成，包括大开口大均匀区的三轴磁场线圈、磁场线圈非均匀性的补偿方法、三轴磁场线圈非正交性补偿方法、串并联组合磁场线圈分流电路等，分析了校准装置的测量不确定度主要来源，给出了验证结果。该装置可开展磁通门磁强计（含传感器）示值误差、线性度、正交度等参数的校准，其成果已应用于十多家单位的磁场测试系统和数十家单位的磁通门磁强计校准。     

On tethered sample and mooring systems near irregular asteroids

A tethered asteroid sample and mooring system is investigated in this paper. In this system the spacecraft is moored to the surface of an irregular asteroid such as 216 Kleopatra by using a rocket-propelled anchor with a cable. The rocket-propelled anchor is a kind of space penetrator, which can inject into asteroids at high speeds generated by its own rocket engine. It can be used to explore the interior structure of asteroids, and it can also be used as a sample collector. When the sampling mission is done, the sample can be pulled back to the spacecraft with the anchor. Using this method, the spacecraft can be kept in a safe region in which it cannot be trapped by the gravitational field of the asteroid. This work is concerned with the dynamics of the tethered system near irregular asteroids. First, a shape model and gravitational field model of irregular asteroids are built. Then, the configuration and the stability of the tethered system are investigated, and the quasi-periodic motion near the equilibrium point of the tethered system is analyzed. Finally, the non-uniform density distribution of the asteroids is considered. The deployment process and the oscillation of the tethered system in the uncertain asteroid gravity field are simulated using the Monte Carlo method. The feasibility of the tethered asteroid sample and mooring system is proved.     

Orientations of LASCO Halo CMEs and their connection to the flux rope structure of interplanetary CMEs

Coronal mass ejections (CMEs) observed near the Sun via LASCO coronographic imaging are the most important solar drivers of geomagnetic storms. ICMEs, their interplanetary, near-Earth counterparts, can be detected in situ, for example, by the Wind and ACE spacecraft. An ICME usually exhibits a complex structure that very often includes a magnetic cloud (MC). They can be commonly modelled as magnetic flux ropes and there is observational evidence to expect that the orientation of a halo CME elongation corresponds to the orientation of the flux rope. In this study, we compare orientations of elongated CME halos and the corresponding MCs, measured by Wind and ACE spacecraft. We characterize the MC structures by using the Grad–Shafranov reconstruction technique and three MC fitting methods to obtain their axis directions. The CME tilt angles and MC fitted axis angles were compared without taking into account handedness of the underlying flux rope field and the polarity of its axial field. We report that for about 64% of CME–MC events, we found a good correspondence between the orientation angles implying that for the majority of interplanetary ejecta their orientations do not change significantly (less than 45 deg rotation) while travelling from the Sun to the near-Earth environment.     

空间引力红移实验的原理与精度

通过对文献[4, 5]关于空间引力红移实验原理与精度的分析,根据爱因斯坦惯性力与引力等效的原理,提出在航天器内部,重力的大部分被惯性力抵消,因而其中的微重力比轨道重力小很多(失重).因此,应当把星载原子钟的重力势取为与微重力相当的有效重力势,而不能简单地将星载钟的重力势取为轨道重力势.另外,检验相对论红移需要将理论值与实验值进行对比,这两种数值均具有误差,而检验精度取决于误差较大者.因此,如果不提高地球重力模型(例如EGM2008)精度而只提高测量精度则不能提高检验精度.     

The determination for ideal release point of test masses in drag-free satellites for the detection of gravitational waves

Gravitational waves are ripples in space–time predicted by Albert Einstein's general relativity and provide a new way to understand the universe. Space-borne detectors of gravitational waves, extending to very large scales, can effectively detect the middle and low-frequency gravitational wave source with the frequency band of 0.1 mHz–1 Hz. The test masses are used to make an inertial reference point in the detection of gravitational waves. Currently, there are few studies concerning the ideal release position for the test masses in the detection of gravitational waves. In this study, we give a general solution for test mass release points to minimize the relative motion between the test mass and the satellite mass center. Moreover, we discuss the situation when the release point equation is not satisfied, and the ideal release point of the along-track. Finally, we report on simulations that verify the accuracy of the theoretical derivation.     

Gravitational waves from accreting neutron stars

The observational evidence for gravitational wave emission from accreting millisecond pulsars, specifically the spin frequency distribution of the population, is reviewed. These continuous wave sources are promising candidates for detection by LIGO. Four theoretical mechanisms are discussed for producing the mass quadrupole moments inferred from the spin frequency data: thermal mountains (formed by gradients in the electron capture rate), r-modes in the core, magnetic mountains (formed by polar magnetic burial), and superfluid circulation in the core. For magnetic mountains, it is shown that the gravitational wave strain is inversely proportional to the magnetic moment, and that the gravitational wave spectrum displays distinctive sidebands as the magnetically confined mountain wobbles around. (The compression of the magnetic field towards the equator also modifies the physics of thermonuclear type I X-ray bursts in these objects, e.g., by thermally insulating the two hemispheres and leading to burst pairs.) For superfluid circulation in the core, it is shown that the high-Reynolds-number flow is nonaxisymmetric and emits a distinctive gravitational wave spectrum with two broad peaks.     

基于脉冲星和紫外敏感器的自主定轨定姿授时研究

为提高深空探测器的自主导航能力, 利用脉冲星导航的脉冲到达时间和脉冲星 角位置测量值、紫外敏感器中心天体质心相对于探测器的方向矢量和距离测量 值以及紫外敏感器输出的航天器姿态角, 以探测器在惯性坐标系下的位置和速度、 探测器本体坐标系相对于惯性坐标系的姿态角、星载时钟钟差为系统状态变量, 通过联邦扩展卡尔曼滤波器估计组合导航系统的系统状态, 并利用火星环绕段 轨道数据进行仿真实验. 仿真结果表明, 该组合导航方法能够使火星轨道器 在环绕段飞行中同时进行定轨、定姿和授时, 且具有较高的导航精度和授时能力.