Pakistan's space programme

Space research in Pakistan is conducted by the Pakistan Space and Upper Atmosphere Research Commission (Suparco). Suparco's programmes consist of the launching of sounding rockets and satellite applications, especially remote sensing and communications. Its long-term goals are to develop communications and remote sensing satellites and to launch lightweight scientific satellites in near-Earth orbits. To train its scientific staff at postgraduate level, Suparco is establishing an Aerospace Institute. The Commission is very active in international forums such as the UN COPUOS, Cospar, IAF and IUCN.     

长期贮存对卫星典型结构件的形变影响分析

某大型卫星经历了长期的地面贮存,从结构生产完成至卫星发射历时9年。文章提取此卫星承力筒、结构板的工程数据,与同类型其他卫星的数据进行对比分析,总结出长期贮存后卫星承力筒和典型结构板——对地板的形变规律,并探讨影响结构变形的原因。研究结果可为后续卫星的贮存设计、贮存试验以及贮存后影响分析提供指导和借鉴。     

Legal analysis of Sea Launch license: National security and environmental concerns

This paper analyzes the national security and environmental concerns surrounding the Sea Launch consortium's international license from a legal perspective. The growing market demand for a more affordable, reliable, and convenient commercial satellite launching service has led to the idea of Sea Launch—launching satellites from the sea near the Equator. However, this can pose potential conflicts between national security and foreign policy interests, and between environmental conservation and economic growth because of the international technology development issues around launching from the sea. This paper illustrates a case for balancing such multiple constraints via legal interpretation. The analysis is conducted in reference to 49 U.S.C. § 70101–70119 Commercial Space Launch Activities and 42 U.S.C. § 4321–4345 National Environmental Policy Act (NEPA) of 1969. The paper also examines weather the United Nations Convention on the Law of the Sea is binding on Sea Launch operations. Although the scope of this paper is limited mostly to the US law and the national security and environmental aspects of Sea Launch, it provides a useful example for policy making of an international collaborative technology development project.     

An inconvenient regulatory truth: Divergence in US and EU satellite export control policies on China

Since the early 1990s the USA has maintained export control sanctions against Chinese international commercial satellite launch services. In 1998 these sanctions were further strengthened, resulting in a de facto international embargo that is premised on ITAR export licenses. Since 1998 this de facto embargo has effectively prohibited China from launching Western commercial satellites of a sophisticated technological standard. Today, European commercial satellite manufacturers are positioned to fully benefit from ITAR-free technology investments, gaining access to Chinese launch services for the launch of commercial telecommunication satellites that are technologically comparable to US satellites. This article examines the policy implications for the USA in light of EU regulatory divergence and the impending return of China to the international commercial launch services market.     

面向微纳卫星应用的激光数传技术

针对遥感微纳卫星对地高速数传需求,开展面向微纳卫星的激光数传技术研究,突破微纳卫星激光通信终端星地快速捕获建链和协同高精度稳定跟踪、天基终端轻小型化、复合光电组件等关键技术。完成微纳卫星的天基激光终端和地面激光终端研制,并开展星地传输试验验证,实现 1 230 km、10/50/100 Mbps 的星地数据传输,验证了相关技术,为后续我国微纳卫星对地遥感应用提供了理想的星地数传手段。     

月球重力场环境对月球卫星轨道影响分析

文章分析了月球复杂的重力场环境对月球卫星轨道运行的影响。通过月球卫星冻结轨道与地球卫星冻结轨道的对比分析,结果表明月球重力场存在较大异常,并由此引起月球卫星轨道发生较大漂移。另外,月球冻结轨道在带谐项影响下还存在中等周期的漂移,仅简单考虑带谐项系数无法求得完美的月球冻结系数。由于月球重力场异常对绕月卫星的影响与地球轨道卫星情况相比存在很大差异,因此月球轨道卫星的长期运行与控制策略的设计必须充分考虑此影响。     

数据通信微小卫星星座系统的发展及应用

随着数据应用的发展,用户对数据传输的精确性、时效性、广域性提出了更高的要求.文章介绍了ORBC()MM、Argos、Aprize等几个国外典型数据微小卫星星座的发展情况,阐述了发展数据微小卫星系统的意义及必要性,从灾害监测、环境保护和商业应用等方面列举了系统的应用需求,分析了实时转发和储存转发两种业务发展模式,给出了系...     

一箭多星发射直接入轨的卫星构型研究

针对中、高轨道一箭多星发射直接入轨的需求,基于卫星与运载火箭的接口、环境条件、包络与操作要求等约束,对卫星构型形式进行了研究。比较了一箭多星发射的几种卫星构型方案（包括中心承力筒式、板筒式、板架式和桁架式构型）,研究了星箭接口选用包带式和点式爆炸螺栓两种连接分离装置的适用性,并据此提出优选桁架式卫星构型和点式爆炸螺栓星箭接口形式,可为卫星结构特性优化和卫星平台通用化奠定基础。     

在轨跟踪与数据中继卫星测控关键技术(上)

根据卫星轨道根数，研究了跟踪与数据中继卫星（TDRS）对用户星的精确跟踪规律，并据此分析了TDRS对卫星平台姿态和天线运动范围的要求。介绍了TDRS测控中的关键技术，如螺旋扫描算法在TDRS搜索用户星时的应用、TDRS对近地卫星的覆盖率、TDRS跟踪多用户星的资源分配准则、星蚀和日凌计算，以及轨道位置保持控制策略等。相关控制策略的正确性已在我国地球同步轨道卫星的在轨测控应用中得到了证实，可用于未来TDRS的工程测控和业务应用。     

Queuing theory application in imaging service analysis for small Earth observation satellites

The performance of Earth observation satellites is usually analyzed by real data or system simulation, which is accurate but not systematic. Modelling satellite service systems with queueing theory and analysing the performance statistics systematically will provide a useful guide in designing satellite systems. Earth observation satellites could be regarded as a two tandem server system with a finite buffer in between, providing two-stage service: image capture and image download service. In this paper, we introduce the queueing models for different service systems: the pure image capture service system, the two-stage service system with Poisson distribution download service, the pure download service system, and the two-stage system with general download service. Formulated solutions are given and some results are shown. From this work we can see queueing theory provides a good way to analyse the performance of small earth observation satellites, which is useful for system mission analysis and optimisation in design stage.     

Policy for robust space-based earth science,technology and applications

Satellite remote sensing technology has contributed to the transformation of multiple earth science domains, putting space observations at the forefront of innovation in earth science. With new satellite missions being launched every year, new types of earth science data are being incorporated into science models and decision-making systems in a broad array of organizations. Policy guidance can influence the degree to which user needs influence mission design and when, and ensure that satellite missions serve both the scientific and user communities without becoming unfocused and overly expensive. By considering the needs of the user community early on in the mission-design process, agencies can ensure that satellites meet the needs of multiple constituencies. This paper describes the mission development process in NASA and ESA and compares and contrasts the successes and challenges faced by these agencies as they try to balance science and applications within their missions.     

FY-1C/D极轨气象卫星姿控分系统及其在轨运行

简要介绍了风云一号(FY-1)C，D极轨气象卫星姿态控制分系统的主要任务、技术指标和系统构成。给出了两星发射后动量轮、红外地平仪、太阳敏感器和三轴磁强计等的运行情况。卫星姿态在轨测试结果表明，FY-1C，D星的姿态稳定，满足甚至优于技术指标要求。最后概述了姿控分系统在可靠性、长寿命和稳定性等方面的技术进步。     

卫星射频接收机电磁兼容防护设计方法

射频接收机是卫星测控、导航、有效载荷等分系统的重要组成设备,也是对电磁干扰最为敏感的设备,在对卫星进行电磁兼容性（EMC）设计时,必须充分考虑射频接收机的EMC防护,以保证其在卫星电测、发射和在轨运行时能够在其所处电磁环境中正常工作.文章描述了卫星射频接收机典型的EMC防护设计方法,从屏蔽、电磁泄露防护和天线耦合防护等方面进行了阐述.     

Iteration-based identification of faulty links in LEO/MEO satellite communication networks

Satellite systems are going to be an important part of the future personal communication infrastructure. The first-generation candidates for satellite personal communication networks (S-PCN) will rely on low earth orbiting (LEO) and medium earth orbiting (MEO) constellations. For LEO satellite systems employing intersatellite links (ISLs), we present a iteration-based algorithm to identify faulty links, which applies to a satellite network assuming a connection-oriented network structure, e.g., ATM or ATM-type switches on-board satellites. In the algorithm a management satellite can autonomously and real-time identify a ranked list of the most probable failed network links through building discrete-time dynamic virtual topology graph (DT-DVTG), then testing can be used to quickly pinpoint the actual faulty links. The performance of the algorithm is evaluated through simulations.     

Expanding global access to civilian and commercial remote sensing data: implications and policy issues

Current and planned developments in the field of civilian and commercial satellite imagery promise a major expansion in international accessibility to remote sensing data and technologies. This paper addresses the implications of the expanding global access to land remote sensing data and their derived products. While atmospheric, meteorological, and oceanographic data is also widely available at cost or free of charge, it is land remote sensing - specifically the unique systems with high-resolution and frequent revisit times - that are of primary concern for international and regional security issues. Military and intelligence satellites are not addressed in this discussion of expansion due to their inherently controlled access, unless such systems also provide commercially available imagery or products (as is the case with some Russian systems).     

Smaller states and the new balance of power in space

The number of states capable of building, launching and operating satellites has grown significantly over the years. This article discusses how going to space in an egalitarian fashion may influence the current state of affairs related to the militarization and weaponization of outer space, the security postures of the already established space powers, and the global balance of power in general. Potential changes in the relationship between old and new spacefarers may instigate an entire shift in the understanding of threats and opportunities for international cooperation in space.     

Prospects for commercial satellite services at Q- and V-bands

Some 16 proposed new satellite systems operating at 36 to 46 GHz (Q-band) and 46 to 56 GHz (V-band) have been proposed to the U.S. Federal Communications Commission by U.S. companies. Of these. 14 are intended to provide global, or nearly global, service. One is intended for U.S. domestic service, and one is a package to provide additional store-and-forward capability on an earlier proposed “Little LEO” system. This paper provides a brief summary of the 14 global systems, which for the most part are designed to exploit the wide band of frequencies available for services such as multimedia distribution and Internet access.

Systems are proposed that would use geostationary orbit, medium earth orbit, low earth orbit, and Molniya orbit satellites, and in some cases combinations of two of these orbits. Most of the new systems propose to employ new technologies such as multiple narrow spot-beam antennas, onboard demodulation and routing of traffic between beams, intersatellite links, and in some cases scanning beams to continuously illuminate the service area as the satellite flies by.

Some of the difficulties involved in fielding systems at these high frequencies arise from the propagation impairments that can be expected and the high cost of solid-state power devices for user terminals, which will drive up costs. It is concluded that, while the large amount of bandwidth (3 GHz) proposed by the FCC for these systems is attractive, few if any are likely to be built while spectrum remains available at Ka-band.     

链路状态感知的低轨卫星网络路由机制

低轨卫星的空间组网能够突破地形限制,实现全天候、高带宽、低时延、广覆盖的数据通信,弥补地面通信系统的不足,使通信服务全球化成为可能。但是,卫星节点的快速移动和能量受限使得空间链路面临高动态、不可靠、间歇性等问题。同时接入用户的分布不均容易导致卫星网络出现重载节点和局部拥塞的情况,这对空间组网和数据传输提出了新的挑战。传统的静态卫星组网模式可靠性差,可伸缩性低,难以适应空间动态组网的需求。针对低轨卫星网络拓扑变化快的特点,提出链路状态感知的路由机制,在降低卫星能耗的同时减轻网络的局部拥塞,使用树莓派搭建半实物仿真平台,并在该平台上进行实验,验证了该机制的有效性。     

Operational continuity of the global meteorological satellite network

The global network of meteorological satellites used different forms of international cooperation during its development, and some of these forms continue. Concern about continued operation of the global network led the WMO to study the issues and to adopt a long-term policy and strategy based on a shared meteorological satellite network. Nations need to consider how to combine their meteorological and space-related organizations in a partnership role, so they can directly contribute to a future global network of meteorological satellites. Some examples are cited to demonstrate that increased direct participation is a valid and feasible objective.     

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。