Real-time GLE alert in the ANMODAP Center for December 13, 2006

Within the last years, a real-time system to monitor high energy cosmic rays for space weather use has been operated at Athens cosmic ray station. Neutron monitors and satellite high resolution data in real time are used, making it possible to observe cosmic rays in dual energy range observations. In large solar energetic particle (SEP) events, ground level enhancement (GLE) can provide the earliest alert for the onset of the SEP event. This system watches for count rate increases recorded in real time by 23 neutron monitors, which triggers an alarm if a ground level enhancement (GLE) of cosmic ray intensity is detected.     

Effects of space weather on the ionosphere and LEO satellites’ orbital trajectory in equatorial,low and middle latitude

We study the effects of space weather on the ionosphere and low Earth orbit (LEO) satellites’ orbital trajectory in equatorial, low- and mid-latitude (EQL, LLT and MLT) regions during (and around) the notable storms of October/November, 2003. We briefly review space weather effects on the thermosphere and ionosphere to demonstrate that such effects are also latitude-dependent and well established. Following the review we simulate the trend in variation of satellite’s orbital radius (r), mean height (h) and orbit decay rate (ODR) during 15 October–14 November 2003 in EQL, LLT and MLT. Nominal atmospheric drag on LEO satellite is usually enhanced by space weather or solar-induced variations in thermospheric temperature and density profile. To separate nominal orbit decay from solar-induced accelerated orbit decay, we compute $r\text{,}h$ and ODR in three regimes viz. (i) excluding solar indices (or effect), where $r=r_0\text{,}h=h_0$ and $\mathit{ODR}={\mathit{ODR}}_0$ (ii) with mean value of solar indices for the interval, where $r=r_m\text{,}h=h_m$ and $\mathit{ODR}={\mathit{ODR}}_m$ and (iii) with actual daily values of solar indices for the interval ($r\text{,}h$ and ODR). For a typical LEO satellite at h?=?450?km, we show that the total decay in r during the period is about 4.20?km, 3.90?km and 3.20?km in EQL, LLT and MLT respectively; the respective nominal decay ($r_0$) is 0.40?km, 0.34?km and 0.22?km, while solar-induced orbital decay ($r_m$) is about 3.80?km, 3.55?km and 2.95?km. h also varied in like manner. The respective nominal ${\mathit{ODR}}_0$ is about 13.5?m/day, 11.2?m/day and 7.2?m/day, while solar-induced ${\mathit{ODR}}_m$ is about 124.3?m/day, 116.9?m/day and 97.3?m/day. We also show that severe geomagnetic storms can increase ODR by up to 117% (from daily mean value). However, the extent of space weather effects on LEO Satellite’s trajectory significantly depends on the ballistic co-efficient and orbit of the satellite, and phase of solar cycles, intensity and duration of driving (or influencing) solar event.     

一种用于快速跟踪视线的空间拦截器姿态控制方法

以空间拦截器的纵轴在中、末制导段要求指向目标的视线，按最小空间角距旋转，作为跟踪目标的姿态定向的假想坐标系，形成本体坐标系相对假想坐标系的误差四元数。由拦截器的转动角速度分量与误差四元数作为状态反馈构造稳态姿态控制的数学模型。为了得到姿态控制所需的变控制力矩，运用PWPF调制器对常值推力姿控发动机的稳态和脉冲工作状态进行调制，构造所谓的“数字变力矩”控制器，实现对姿态的连续控制。仿真计算结果表明，该方法是实际可行的。     

铝热沉的焊接工艺选择及其实施

文章介绍了在新型空间环境模拟器中铝热沉的焊接工艺选择和实施过程。该热沉是用2千多根铝管和4千多条焊缝焊成的。它要求焊缝在长期冷热交变作用下仍具有高度的气密性。实践证明了这种工艺选择的正确性,并很好地满足了设计要求。     

时延下空间遥操作机器人系统工作模式研究

工作在人机交互方式下的遥操作机器人是实现空间作业的有力手段。首先介绍了空间遥操作机器人系统的构成与工作原理，然后提出了基于临场感遥控技术、虚拟现实技术与自主控制技术相结合的多种工作模式，用于实现在不同条件下时延空间遥操作机器人系统的作业任务，并讨论了工作模式选择的方法。最后经模拟实验系统验证了所提出的工作模式的有效性。     

光学遥感器光电信号处理系统的空间辐射效应研究

文章针对光学遥感器光电信号处理系统,描述了空间辐射效应研究的方法和途径。首先介绍了光学遥感器常用运行轨道的空间辐射环境,然后选择光学遥感器的光电信号处理系统作为分析模型,介绍了光电信号处理系统的电路组成和主要元器件,从器件级、电路级到系统级对空间辐射效应的危害性进行分析,并且结合元器件的抗辐射性能现状,归纳了辐射效应的薄弱环节及主要元器件需要进行的辐照试验。最后对空间辐射效应研究的方法和步骤进行了总结。     

空间相机温度解算方法的分析与研究

通过温度解算完成相机主体温度测量,是相机主体温控系统实现的关键环节之一.传统的温度解算方法存在数据存储量大、可移植性差、温度映射精度低等缺点.文章提出一种拟合温度解算法,针对不同的系统需求,给出两种改进方案,对拟合温度解算法及其改进方案的原理、性能及实现方式进行描述与分析.实践证明,该方法具有占用内存小、可移植性好、温...     

SpaceWire与SpaceFibre高速总线发展与研究

介绍SpaceWire总线和SpaceFibre网络的基本情况及其构成。分析了两者用于航天器时的优点。综述了两者在国内外发展和基础研究状况,给出了研究与应用中的高可靠SpaceWire-D信息组网和高速SpaceFibre网络传输等关键技术。     

海上航天测控系统领域本体的构建研究

随着我国航天事业的高速发展,对海上测控系统提出了越来越高的要求。测量船执行任务时涉及飞行器、船载设备、测量船工况等任务要素。本文根据任务要素的主要层次关系及它们之间的约束关系,构建了海上航天测控系统领域本体TTC_Onto,其实现和应用可以有效地提高任务分析的灵活性和准确性。并给出了TTC_Onto的构建过程及其评价机制。     

Estimation of ballistic coefficients of space debris using the ratios between different objects

This paper proposes a new method to estimate the ballistic coefficient (BC) of low earth orbit space debris.The data sources are the historical two-line elements (TLEs).Since the secular variation of semi-major axes is mainly caused by the drag perturbation for space objects with perigee altitude below 600 km,the ballistic coefficients are estimated based on variation of the mean semi-major axes derived from the TLEs.However,the approximate parameters used in the calcu lation have error,especially when the upper atmosphere densities are difficult to obtain and always estimated by empirical model.The proportional errors of the approximate parameters are cancelled out in the form of ratios,greatly mitigating the effects of model error.This method has been also been validated for space objects with perigee altitude higher than 600 km.The relative errors of esti mated BC values from the new method are significantly smaller than those from the direct estimation methods used in numerical experiments.The estimated BC values are used for the prediction of the semi-major axes,and good performance is obtained.This process is also a feasible method for prediction over a long period of time without an orbital propagator model.