Inversion of satellite gradiometry data using statistically modified integral formulas for local gravity field recovery

The satellite gravity gradiometric data can be used directly to recover the gravity anomaly at sea level using inversion of integral formulas. This approach suffers by the spatial truncation errors of the integrals, but these errors can be reduced by modifying the formulas. It allows us to consider smaller coverage of the satellite data over the region of recovery. In this study, we consider the second-order radial derivative (SORD) of disturbing potential (T_rr) and determine the gravity anomaly with a resolution of 1° × 1° at sea level by inverting the statistically modified version of SORD of extended Stokes’ formula. Also we investigate the effect of the spatial truncation error on the quality of inversion considering noise of T_rr. The numerical investigations show satisfactory results when the area of T_rr coverage is the same with that of the gravity anomaly and the integral formula is modified by the biased least-squares modification. The error of recovery will be about 6 mGal after removing the regularization bias in the presence of 1 mE noise in T_rr measured on the orbit.     

Characteristics of field line resonance type geomagnetic pulsations and variations of plasmaspheric plasma density distribution

The period of field line resonance (FLR) type geomagnetic pulsations depends on the length of the field line and on the plasma density in the inner magnetosphere (plasmasphere), where field lines are closed. Here as FLR period, the period belonging to the maximum occurrence frequency of the occurrence frequency spectrum (equivalent resonance curve) of pulsations has been considered. The resonance system may be replaced by an equivalent resonant circuit. The plasma density would correspond to the ohmic load. The plasma in the plasmasphere originates from the ionosphere, thus FLR period, occurrence frequency are also affected by the maximum electron density in the ionosphere. The FLR period has shown an enhancement with increasing F region electron density, while the occurrence frequency indicated diminishing trend (possible damping effect). Thus, the increased plasma density may be the cause of the decreased occurrence of FLR type pulsations in the winter months of solar activity maximum years (winter anomaly).     

CubeSail: A low cost CubeSat based solar sail demonstration mission

CubeSail is a nano-solar sail mission based on the 3U CubeSat standard, which is currently being designed and built at the Surrey Space Centre, University of Surrey. CubeSail will have a total mass of around 3 kg and will deploy a 5 × 5 m sail in low Earth orbit. The primary aim of the mission is to demonstrate the concept of solar sailing and end-of-life de-orbiting using the sail membrane as a drag-sail. The spacecraft will have a compact 3-axis stabilised attitude control system, which uses three magnetic torquers aligned with the spacecraft principle axis as well as a novel two-dimensional translation stage separating the spacecraft bus from the sail. CubeSail’s deployment mechanism consists of four novel booms and four-quadrant sail membranes. The proposed booms are made from tape-spring blades and will deploy the sail membrane from a 2U CubeSat standard structure. This paper presents a systems level overview of the CubeSat mission, focusing on the mission orbit and de-orbiting, in addition to the deployment, attitude control and the satellite bus.     

Dynamic orbit propagation in a gravitational field of an inhomogeneous attractive body using the Lagrange coefficients

The analytical methods have nearly been replaced by the numerical methods due to their higher accuracy and accessibility of computation facilities. The semi-analytical Lagrange method of orbit propagation using f and g series is a competitive alternative to the numerical integration technique if the Lagrange coefficients are derived in a full gravitational field. In this paper, a generalization of the Lagrange method of orbit propagation is introduced. In other words, we introduce a complete form of the Lagrange coefficients in all force fields developed in the spherical harmonics for example full gravitational field of the Earth. The method is numerically compared with the numerical integration technique. In order to show the numerical performance of the method, it has been implemented for orbit propagation of a GPS-like MEO and CHAMP-like LEO satellites. Discrepancy at centimeter level for CHAMP-like and sub-millimeter accuracy for GPS-like satellites shows relatively high performance of the developed algorithm. Compared to integration method, the proposed Lagrange method is nearly faster by a factor two for small Nmax and four for large Nmax.     

基于黑盒测试环境的交会对接软件时序分析技术及应用

航天器空间交会对接难度大,GNC软件对任务的完成起到重要作用.由于交会对接控制软件功能复杂,时序要求严格,这对软件测试提出了很高的要求.基于黑盒测试环境,利用FPGA设计方法和时序分析技术,实现了对交会对接软件重要数据运行时序的捕获和对上下行信号相位关系的跟踪,完善了故障触发和上行注入手段.该测试环境在交会对接软件研制过程中起到重要作用.     

树立高校思想政治工作新理念

新形势下高校思想政治工作挑战严峻,如何顺应形势发展培养出合格的建设者和可靠接班人,怎样加强和改进高校思想政治工作已成当务之急,树立传承、创新、开放和系统工作理念,成为开创高校思想政治工作新局面的重要途径。     

A310飞机扰流板系统故障分析及排除方法

通过对A310—300（空客310）飞机扰流板系统故障的分析及排除,使机务工作者对扰流板系统的工作原理有全面深入的了解,再遇到类似故障时能灵活处理,及时、有效地排查故障,节约维护成本,保障飞机安全、正点飞行。     

星箭锁紧装置黏滞摩擦系数的影响因素研究

星箭锁紧装置是卫星与火箭连接的关键机构。装置中的V形卡块在预紧力施加过程中,易发生偏斜,使得星箭分离配合面接触不均匀,产生应力集中,导致星箭分离面黏着磨损。研究了星箭锁紧装置中的V形卡块和上下端框的铝合金摩擦副在不同影响因素下摩擦系数的变化,探究了温度、正压力以及铝合金表面粗糙度对界面黏着和黏滞摩擦系数的影响。研究结果表明,硫酸阳极化处理的2A14T6-2A14T6比较适合作为摩擦副材料,在加工和锁紧过程中,应合理控制其粗糙度、温度和正压力,以避免黏着磨损。     

用于压力传感器校准的高低温试验箱设计

基于压力传感器在高低温环境下的校准需求,设计了一种专用高低温试验箱。其控制温度范围可达到-120℃[KG-*4]~[KG-*7]500℃。提出了高低温试验箱的总体方案,介绍了宽温区温度的实现方法以及高温和低温系统不兼容的解决方法和控制流程。试验验证结果显示,高低温试验箱达到了实现宽温区温度的目的,满足设计指标要求。     

环境严酷性指数腐蚀当量方法及其应用研究

 建立统一的腐蚀损伤环境变量——环境严酷性指数（ESI）,并研究其在飞机结构耐久性设计中的应用。在材料/结构腐蚀与单一环境类型/要素/强度关系基础上,按照《由电化学测量值计算腐蚀率和相关量的标准方法》(ASTM G102 89),引入并给出相应的ESI,并在一定工程假设下,给出在综合环境(由不同环境类型/要素/强度组成)作用下的ESI。同时,在腐蚀损伤等效原则下,用标准的环境类型/要素/强度及其作用时间当量化地表征综合环境及相应的作用时间(即环境谱),为环境加速试验环境当量提供依据并形成环境当量谱以应用于飞机结构耐久性设计中的腐蚀防护与控制(EEF),评估结构的检查周期/日历寿命。根据相关试验结果计算了典型金属材料在不同环境中的环境严酷性指数及环境当量化系数(EEF), 给出了环境简化或折算的算例。