空间光学望远镜在轨建造中的结构机构技术

围绕空间光学望远镜在轨建造中的结构机构技术进行分析,重点包括结构机构相关的关键技术基本概念和技术特点,分别对大型望远镜空间结构拓扑构型优化及模块技术、光机结构机构的高精度展开调整及锁合技术、典型光机元件的在轨增材制造技术、机器人辅助自主精密装配及控制技术进行了技术内涵及先进技术途径分析.最后展望了在轨建造中结构机构技术...     

同波束干涉测量差分相时延观测模型研究及验证

针对月球轨道交会对接地面高精度引导需求,对同波束干涉测量差分相延观测模型进行分析验证。根据甚长基线干涉测量几何时延观测量同一波前的定义,推导出同波束差分时延观测量的观测模型。并提出一种精确的同波束干涉测量差分相时延闭合算法,同时结合SELENE任务实测的数据计算差分相时延闭合值,用于对观测模型进行验证。实测数据计算结果表明,采用本文提出的精确算法显著地消除同一波前差分相时延闭合值中的趋势项,差分相时延闭合值的精度在0.5ps~1ps范围内,验证了观测模型的正确性。该研究对于后续的月球交会对接地面高精度测定轨任务分析设计将具有一定的参考价值。     

轨姿控液体火箭发动机水击仿真模拟

以轨姿控液体火箭发动机为研究对象,根据模块化思想,利用AMESim建立了仿真平台,仿真计算了发动机系统工作中管路的水击压力。结果表明:轨控发动机的工作是引起大水击的主要因素。通过与理论计算和试验数据的对比表明,仿真模型较好地描述了管路水击的生成过程。介绍了减小系统水击量的措施。     

太阳帆航天器移位轨道设计

研究了太阳帆日心移位轨道的稳定性、控制律设计及轨道拼接。将柱坐标形式的太阳帆动力学方程在参考移位轨道附近线性化,得到线性变分方程。分析线性变分方程的特征值在复数平面上的位置就可以得到移位轨道的稳定性条件。设计了太阳帆日心移位轨道的控制律,并证明了控制律满足稳定性条件。该控制律仅要求太阳帆在移位轨道飞行时姿态角α保持不变。此外,太阳帆移位轨道可以与开普勒轨道相互转化,也可以与移位轨道之间相互拼接。     

Comparison of Antarctic riometer radio wave absorption and THEMIS mission energetic electron fluxes

Simultaneous observations of in situ plasma properties in the tail of the Earth’s magnetosphere and of ground based instruments, lying on the same geomagnetic field lines, have recently proved to yield significant new results. In most cases magnetosphere ionosphere interactions during the night-time northern hemisphere conditions are studied. Here, observations of energetic electrons in the tail of the Earth’s magnetosphere made by the THEMIS mission satellites are compared with auroral radio wave absorption determined by riometers in the Antarctic for sunlit conditions. Days for which satellites and riometers are connected by the same geomagnetic field line are selected using a geomagnetic field model. The six days analysed show clear associations between fluxes and absorptions in some cases. However, these do not necessarily correspond to conjugacy intervals. Hours of positive associations are 1.65 times those for negative associations, all hours and days considered (1.42–3.6 on five days and 0.58 on the other day). These computations are assumed appropriate since the footprints of the satellites used approximately follow corrected geomagnetic parallels for all six days studied. The use of a finer parameterization of geomagnetic models to determine conjugacy may be needed.     

Magnetospheric disturbances associated with the 13 December 2006 solar flare and their ionospheric effects over North-East Asia

We present an observational study of magnetospheric and ionospheric disturbances during the December 2006 intense magnetic storm associated with the 4В/Х3.4 class solar flare. To perform the study we utilize the ground data from North–East Asian ionospheric and magnetic observatories (60–72°N, 88–152°E) and in situ measurements from LANL, GOES, Geotail and ACE satellites. The comparative analysis of ionospheric, magnetospheric and heliospheric disturbances shows that the interaction of the magnetosphere with heavily compressed solar wind and interplanetary magnetic field caused the initial phase of the magnetic storm. It was accompanied by the intense sporadic E and F2 layers and the total black-out in the nocturnal subauroral ionosphere. During the storm main phase, LANL-97A, LANL 1994_084, LANL 1989-046 and GOES_11 satellites registered a compression of the dayside magnetosphere up to their orbits. In the morning–noon sector the compression was accompanied by an absence of reflections from ionosphere over subauroral ionospheric station Zhigansk (66.8°N, 123.3°E), and a drastic decrease in the F2 layer critical frequency (foF2) up to 54% of the quite one over subauroral Yakutsk station (62°N, 129.7°E). At the end of the main phase, these stations registered a sharp foF2 increase in the afternoon sector. At Yakutsk the peak foF2 was 1.9 time higher than the undisturbed one. The mentioned ionospheric disturbances occurred simultaneously with changes in the temperature, density and temperature anisotropy of particles at geosynchronous orbit, registered by the LANL-97A satellite nearby the meridian of ionospheric and magnetic measurements. The whole complex of disturbances may be caused by radial displacement of the main magnetospheric domains (magnetopause, cusp/cleft, plasma sheet) with respect to the observation points, caused by changes in the solar wind dynamic pressure, the field of magnetospheric convection, and rotation of the Earth.     

GNSS-R concept extended by a fine orbit tuning

Small changes in semimajor axis of the orbits selected for the GNSS-R [R as Reflectometry] satellites, so-called fine orbit tuning, known from the ESA’s Gravity and steady-state Ocean Circulation Explorer mission, can dramatically increase the number of nadir and off-nadir reflecting points and, in turn, can enhance the capability of the concept of bistatic altimetry (GNSS Reflectometry) without additional costs. The application of our suggestion is feasible for a satellite which will be equipped by thrusters for the orbit keeping. During the mission lifetime several orbit tunings are feasible, just to transfer from one to another orbit. Then we can study short-periodic or longer-periodic features, according to scientific goals defined for the mission. The shortest cycles (few days), corresponding to the required revisit time (defined by ESA), may be subcycles of much longer cycles (repeat periods).     

聚酰亚胺/无机氧化物复合薄膜的制备与耐原子氧性能

分别以锆酸四丁酯、钛酸四丁酯和正硅酸乙酯为氧化物前驱体,利用溶胶凝胶法制备了一系列聚酰亚胺/无机氧化物复合薄膜,在原子氧地面模拟设备中进行了原子氧暴露实验,原子氧累计通量约为3.1×10²⁰ atom/cm².分别考察了无机氧化物种类和含量对复合薄膜力学性能和耐原子氧性能的影响.结果表明,无机氧化物在聚酰亚胺基体中的分散形态对其力学性能影响很大;原子氧暴露后,聚酰亚胺薄膜表面分别形成了富锆、富钛和富硅的保护层,质量损失率减小,耐原子氧性能明显提高.     

“伽利略”卫星在轨任务控制系统高级规范综述

重点描述了＂伽利略＂卫星在轨任务控制系统高级规范的相关内容,其中包括系统规范和子系统规范,如系统监测和控制子系统、遥测监测子系统、遥控指令子系统和数据归档子系统等;就如何借鉴＂伽利略＂卫星在轨任务控制系统高级规范,提出了一些开展我国星座卫星在轨任务控制系统设计的策略和方法,如设计方法、实现途径、自动化和安全策略等。     

挠性充液航天器超近程逼近段动力学建模与控制

超近程逼近过程中,服务航天器为刚柔液耦合的复杂系统,单摆等液体晃动模型不再适用,对这种工况下的航天器进行了动力学建模与控制的研究。采用虚功率原理推导了一种新的适用于三轴推力作用下的液体晃动等效模型,通过引入相对位置导引矢量与相对位置误差矢量,建立了相对轨道误差动力学模型,结合相对姿态动力学模型,得到超近程逼近段的刚柔液耦合的相对轨道姿态动力学模型。针对模型存在的不确定性和未知干扰,设计了基于滑模估计器的相对姿轨耦合控制律。通过数学仿真验证了控制律的有效性,仿真中的晃动结果与Flow-3D结果能够吻合,验证了晃动模型的合理性。