Characterizing space debris longitude-dependent distribution based on RAAN perturbation rate

The space debris environment is one of the major threats against payloads. Space debris orbital distribution is of great importance for space debris environment modeling. Due to perturbation factors, the Right Ascension of Ascending Node (RAAN) of space objects changes consistently, causing regular rotation of the orbit plane around Earth’s axis. Based on the investigation of the RAAN perturbation rate of concerned objects, this paper proposes a RAAN discretization method in order to present the space debris longitude-dependent distribution. Combined with two line element (TLE) data provided by the US Space Surveillance Network, the estimated value from RAAN discretization method is compared with the real case. The results suggest that using only the initial orbital data at the beginning of the time interval of interest, the RAAN discretization method is able to provide reliable longitude distribution of concerned targets in the next following period. Furthermore, spacecraft cumulative flux against space debris is calculated in this paper. The results suggest that the relevance between spacecraft RAAN setup and flux output is much smaller for LEO targets than MEO targets, which corresponds with the theory analysis. Since the nonspherical perturbation is the major factor for RAAN variation, the RAAN perturbation rate has little connection with the size of orbital objects. In other words, the RAAN discretization method introduced in this paper also applies to space debris of different size range, proposing a possible suggestion for the improvement of space debris environment engineering models.     

宇航科学文献情报源初析

本文通过对《宇航学报》1981～1988年322篇论文中2466条参考文献的统计分析,得出以下结论,(a)宇航科学的文献情报源重在期刊类文献。(b)以《宇航学报》、《航空学报》、《AIAA,Jourual》等六种期刊类文献为重点文献。(c)中文的引文作者和论文作者相对集中。(d)期刊类文献的半衰期为8～10年。     

Pilots for space tourism

This article sheds light on the key player needed for any space tourism adventure: the pilot who flies the spacecraft. The paper addresses the potential benefits of including a pilot at the controls when designing a space tourism spacecraft. It examines the basic qualifications and advanced skills required of space tourism pilots and discusses key training requirements for selected pilots and space pilots' pay and benefits. In addition, the research concludes that, just as the pioneers of passenger transport in aviation entertained and captured the interest of their passengers, the space pilot should have the skills of a tour guide.     

Collision Risk Mitigation in Geostationary Orbit

The short- and long-term effects of spacecraft explosions, as a function of the end-of-life re-orbit altitude above the geostationary orbit (GEO), were analyzed in terms of their additional contribution to the debris flux in the GEO ring. The simulated debris clouds were propagated for 72yrs, taking into account all the relevant orbital perturbations.The results obtained show that 6–7 additional explosions in GEO would be sufficient, in the long term, to double the current collision risk with sizable objects in GEO. Unfortunately, even if spacecraft were to re-orbit between 300 and 500km above GEO, this would not significantly improve the situation. In fact, an altitude increase of at least 2000km would have to be adopted to reduce by one order of magnitude the long-term risk of collision among geostationary satellites and explosion fragments. The optimal debris mitigation strategy should be a compromise between the reliability and effectiveness of spacecraft end-of-life passivation, the re-orbit altitude and the acceptable debris background in the GEO ring. However, for as long as the re-orbit altitudes currently used are less than 500km above GEO, new spacecraft explosions must be avoided in order to preserve the geostationary environment over the long term.     

Modelling of Spall in an Anisotropic Aluminium Alloy

Spall caused by hypervelocity impacts at the lower range of velocities could result in significant damage to spacecraft. A number of polycrystalline alloys, used in spacecraft manufacturing, exhibit a pronounced anisotropy in their mechanical properties. The aluminium alloy AA 7010, whose orthotropy is a consequence of the meso-scale phase distribution or grain morphology, has been chosen for this investigation. The material failure observed in plate impact was simulated using a number of spall models. The Hugoniot elastic limit and spall strength have been studied as a function of orientation, and compared to experimental results.     

中国空间技术成就斐然——纪念东方红1号卫星发射成功30周年

从1970年至1999年,中国已用长征系列运载火箭进行了68次航天发射,累计发射了84颗人造地球卫星(其中国产卫星52颗、国外卫星32颗)和1艘无人状态的试验飞船,发射成功率约85％。现今,中国对空间技术体系的认识已得到深化,中国的航天器进入太空技术已位居世界前列,中国的航天信息应用技术已取得显著效益。     

首颗自主地月转移微卫星“龙江二号”

本文对世界首颗独立完成地月转移、近月制动、环月飞行的微卫星“龙江二号”进行了介绍。首先阐述了龙江二号的任务目标和总体方案;然后重点分析了轨道设计与控制、复杂电磁干扰的标定与抑制、宽视场三维基线干涉测量等关键技术难点;接着回顾了任务的实施过程;最后详细介绍了低频射电探测仪、沙特光学相机和VHF/UHF通信模块与学生微型CMOS相机等有效载荷,并展示了上述载荷获取的初步成果。     

轻型空间相机遮光罩组件的研制

文章介绍了空间遥感相机遮光罩的结构特点及其功能。重点介绍了一种用于可见-红外光谱仪上的轻型遮光罩,该仪器安装于2005年美国发射的火星勘测轨道飞行器(MRO)上。     

多飞行器测控技术的研究

提出了一种基于DBF和DMF-CDMA技术的多飞行器测控系统。首先描述了系统的工作原理，然后对DBF给出了全面和详细的计算机仿真，包括圆面阵DBF阵因子方向图仿真和DBF对多飞行器的搜索与跟踪仿真。最后对DMF-CDMA给出了实验结果。实验的硬软件巳达到实用水平。这些说明本文提出的多飞行器测控方案是可行的。     

20世纪中国的航天返回与遥感

介绍了中国在20世纪发射的返回式航天器和光学型对地观测类卫星、研制成功的航天光学遥感器和建成的卫星对地观测信息应用系统 ,展示了中国在航天返回与遥感领域取得的进展