A parametric study of space transfer/upper propulsion stages

For Space Transportation System (i.e. Space Shuttle) launched satellites destined for a Geosynchronous Earth Orbit (GEO), there is a need for cost-effective, versatile propulsion systems to provide the perigee burn, i.e. to boost the satellite from Low Earth Orbit (LEO) to Geosynchronous Transfer Orbit (GTO). Surveys of commercial spacecraft activities and future GEO satellite requirements indicate that a spacecraft propulsion system that will provide the perigee burn for a broad range of future commercial satellites would have an excellent market potential.Parametric studies to investigate and define attractive perigee-burn upper propulsion systems (i.e. an Upper Propulsion Stage, or a UPS) are presented. The feasibility and payload capacilities that could be provided by a UPS assembled from essentially off-the-shelf components and subsystems, and the benefits that could be achieved by using major subsystems specifically tailored for the application are presented. The results indicate that attractive UPS configurations can be defined using either off-the-shelf or optimized major subsystems.     

中轨卫星移动通信系统小区驻留时间分布的研究

在中轨卫星移动通信系统中 ,确定小区驻留时间分布对于合理地规划切换策略具有十分重要的意义。文中指出了地球固定覆盖与卫星固定覆盖两种方式下小区驻留时间分布不同的原因。提出一种仿真计算卫星固定覆盖方式下小区驻留时间分布的方法 ,得出了数值结果 ,并与地球固定覆盖方式下的小区驻留时间分布作了比较     

天基照相跟踪空间碎片批处理轨道确定研究

随着国内外天基观测空间碎片研究的展开,文章提出了利用跟踪卫星的CCD(Charge
Coupled Device)相机对空间碎片进行轨道探测的方法,首先建立了CCD照相观测模型和基于 照相观测 的空间碎片批处理轨道确定模型。通过对CCD相机底片归算方法的分析可知,利用
CCD相机所获得的观测数据与跟踪卫星的姿态无关,且其精度只与测量和坐标转换计算的精 度有关,在测量和计算中可获得较高的精度。分别对分布密度较高的低轨道和地球同步 轨道区域的空间碎片进行了定轨分析。仿真结果表明,定轨时采用两个跟踪弧段的照相数据 定轨精度大大高于一个弧段照相数据的定轨精度;跟踪卫星距离空间碎片越近,定轨精度越 高;低轨道空间碎片的定轨精度高于地球同步轨道上的空间碎片定轨精度。
     

GEO移动通信卫星合成多波束天线仿真分析

针对地球静止轨道（GEO）移动通信卫星星上多波束天线波束成形技术,研究了合成多波束对地覆盖、点波束天线增益以及波束间干扰抑制技术。利用仿真分析软件进行多波束天线的波束成形仿真分析,优化了天线系统的设计参数,改善了波束间的隔离度指标,提高了系统通信性能和局部地区的信道容量,完成了地球静止轨道移动通信卫星系统合成多波束天线的设计。     

我国GEO航天器总体综合优化技术研究进展

总体综合优化设计是航天器研制持续追求的目标,多学科集成设计是有效途径之一。围绕航天器总体综合优化设计,总结了近年来我国在地球静止轨道(GEO)航天器系统与学科建模、多学科集成优化设计策略、寻优算法、软件工具开发及工程应用实施等方面研究进展,针对我国GEO航天器发展新需求以及现阶段综合优化设计技术发展的不足,结合系统工程技术发展新趋势,指出航天器综合优化设计后续应重点加强集成建模、工程化应用研究,为高轨航天器总体优化设计技术发展提供指导。     

一种基于反向探测的低轨星座路由算法

针对低轨卫星星座通信系统动态拓扑结构的特点,提出了一种基于反向探测的路由算法（Reverse Detection Based Routing,RDBR）,采用分布式实现且具有极低的运算复杂度,适合于星上实时计算,对于提高星座网络的自主运行能力具有重要意义。与快照序列（Sequent Snap Shots,SSS）算法的对比分析和仿真表明,RDBR算法以有限的信令开销取得的路由性能优于60s快照序列算法。
     

航天器空间碎片被动防护技术

文章介绍了航天器磁力矩器在低轨道等离子体环境中的一些效应。以某型号卫星为例,计算了某型号磁力矩器产生的磁场,分析了等离子体在磁力矩器产生的磁场中的运动状态。经过建模计算,磁力矩器周围等离子体中的电子将在磁力矩器两端往复运动,而距离磁力矩器较远的电子将聚集在磁力矩器的两端附近。     

北斗三号短报文低轨卫星测控应用研究

针对低轨卫星星座测控管理的全球覆盖需求和测控链路资源需求,分析北斗三号全球导航系统短报文用于低轨卫星测控的基本能力,描述应用北斗三号全球短报文进行卫星测控的系统组成、工作流程及各部分功能,识别用于卫星测控管理的相关关键技术,并提出关键技术的初步解决途径,给出测控应用模式建议.     

低轨卫星缺失时序数据的模式识别方法

在航天应用中，低轨卫星经常会由于原始数据缺失而影响卫星时序数据模式识别结果，降低准确率。针对该问题提出了一种新型MR-GRU模型，可有效处理缺失时序数据，并获得较好的模式识别准确率。区别于传统模型的补全缺失数据的方法，MR-GRU模型直接在缺失时序数据上运用循环神经网络进行训练，对传统门控循环单元结构进行了改进，增加了两个新变量：掩蔽项和衰减项。掩蔽项作用于输入，衰减项作用于输入和隐层单元输出。MR-GRU模型不仅能够保持时序数据固有的时间特性，还能有效提高模式识别精度。在卫星时序数据上的模式识别试验表明，MR-GRU模型准确率优于传统模型。     

The enigma of small satellites for earth observation

Small satellites have captured a continuously increasing share of the market in the fields of science, technology and recently also in the telecommunications and Earth observation areas. User requirements and market opportunities for space based satellite systems for Earth observation products have grown substantially in the past decade. Criteria for the utilization of different classes of satellite systems (small and large) and analogies to developments in other areas, e.g. the telecommunications field are discussed. The end to end character of service and product oriented systems as key criteria for market success in the scientific, applications and commercial areas is underlined. Recent developments in the global change, the Earth observation applications and commercial sectors are reviewed and compared. Opportunities for small satellites in the field are related to technology advancements, cost reduction options, and progress in the state of the art in system design.     

Earth observation from space – The issue of environmental sustainability

Remote sensing scientists work under assumptions that should not be taken for granted and should, therefore, be challenged. These assumptions include the following:1. Space, especially Low Earth Orbit (LEO), will always be available to governmental and commercial space entities that launch Earth remote sensing missions.2. Space launches are benign with respect to environmental impacts.3. Minimization of Type 1 error, which provides increased confidence in the experimental outcome, is the best way to assess the significance of environmental change.4. Large-area remote sensing investigations, i.e. national, continental, global studies, are best done from space.5. National space missions should trump international, cooperative space missions to ensure national control and distribution of the data products.At best, all of these points are arguable, and in some cases, they're wrong. Development of observational space systems that are compatible with sustainability principles should be a primary concern when Earth remote sensing space systems are envisioned, designed, and launched. The discussion is based on the hypothesis that reducing the environmental impacts of the data acquisition step, which is at the very beginning of the information stream leading to decision and action, will enhance coherence in the information stream and strengthen the capacity of measurement processes to meet their stated functional goal, i.e. sustainable management of Earth resources. We suggest that unconventional points of view should be adopted and when appropriate, remedial measures considered that could help to reduce the environmental footprint of space remote sensing and of Earth observation and monitoring systems in general. This article discusses these five assumptions in the context of sustainable management of Earth's resources. Taking each assumption in turn, we find the following:(1) Space debris may limit access to Low Earth Orbit over the next decades.(2) Relatively speaking, given that they're rare event, space launches may be benign, but study is merited on upper stratospheric and exospheric layers given the chemical activity associated with rocket combustion by-products.(3) Minimization of Type II error should be considered in situations where minimization of Type I error greatly hampers or precludes our ability to correct the environmental condition being studied.(4) In certain situations, airborne collects may be less expensive and more environmentally benign, and comparative studies should be done to determine which path is wisest.(5) International cooperation and data sharing will reduce instrument and launch costs and mission redundancy. Given fiscal concerns of most of the major space agencies – e.g. NASA, ESA, CNES – it seems prudent to combine resources.     

Activities of the COSPAR Panel on Exploration supporting the Global Exploration Roadmap

The Global Exploration Roadmap (GER) is driven by several goals and objectives that include space science, the search for life as well as preparatory science activities to enable human space exploration. The Committee on Space Research (COSPAR), through its Commissions and Panels provides an international forum that supports and promotes space exploration worldwide. COSPAR's Panel on Exploration (PEX) investigates a stepwise approach of preparatory research on Earth and in Low Earth Orbit (LEO) to facilitate a future global space exploration program. We summarize recent activities and workshops of PEX in support of the GER.     

A Delphi-Based Framework for systems architecting of in-orbit exploration infrastructure for human exploration beyond Low Earth Orbit

The current debate in the U.S. Human Spaceflight Program focuses on the development of the next generation of man-rated heavy lift launch vehicles. While launch vehicle systems are of critical importance for future exploration, a comprehensive analysis of the entire exploration infrastructure is required to avoid costly pitfalls at early stages of the design process. This paper addresses this need by presenting a Delphi-Based Systems Architecting Framework for integrated architectural analysis of future in-orbit infrastructure for human space exploration beyond Low Earth Orbit. The paper is structured in two parts.     

Inflatable antenna for cubesats: Motivation for development and antenna design

CubeSats and small satellites have potential to provide means to explore space and to perform science in a more affordable way. As the goals for these spacecraft become more ambitious in space exploration, moving from Low Earth Orbit (LEO) to Geostationary Earth Orbit (GEO) or further, the communication systems currently implemented will not be able to support those missions. One of the bottlenecks in small spacecraft communication systems is represented by antennas' size, due to the close relation between antenna gain and dimensions. Current antennas for CubeSats are mostly dipole or patch antennas with limited gain. Deployable (not inflatable) antennas for CubeSats are currently being investigated, but these solutions are affected by the challenge of packaging the whole deployable structure in a small spacecraft.The work that we propose represents the first attempt to develop an inflatable antenna for CubeSats. Inflatable structures and antennas can be packaged efficiently occupying a small amount of space, and they can provide, once deployed, large dish dimension and correspondent gain. Inflatable antennas have been previously tested in space (Inflatable Antenna Experiment, STS-77). However they have never been developed for small spacecraft such as CubeSats, where the packaging efficiency, the deployment, and the inflation represent a challenge.Our study explores for the first time the possibility of developing such antenna in a way compatible with CubeSat dimensions and constraints. The research provides answers on the possible dimensions for an inflatable antenna for small satellites, on the gain and resolution that can be achieved, and on the deployment and inflation mechanism compatible with CubeSat. Future work in the development of the antenna will include the test of the antenna in flight during a specific technical demonstration mission.The article is structured as follows: context and motivation for Cubesat inflatable antenna are described; then a study to design the antenna which achieves the required performance metrics, while respecting the constraints imposed by CubeSat structure, is presented.     

卫星姿轨控系统故障推演系统设计架构

研究了目前的卫星姿态轨道控制系统,针对其故障预测、诊断及对策提出了一套故障推演系统设计方案.该方案由故障动态注入系统、动态模拟系统、数据归档显示处理系统组成,完成了对在轨卫星的电性接口一致性仿真,通过计算仿真遥测数据与真实遥测数据的相关量获得异常指标,得出可能出现的故障模式;通过软故障、硬故障和真实部件故障注入方式复现...     

Success criteria for the next generation of space based multimedia systems

It has been almost three years since the great Geostationary Orbit Earth (GEO) Ka-band filing rush concluded at the FCC. The majority of filers have gone on to register their systems with the ITU, creating the most congested new Spectrum band at system startup that the world has ever seen. However, for all the hype, none of the GEO systems are thought yet to have begun to bend metal. All appear consumed with the requirement to find partners with whom to share the business risks, costs and rewards.

This Paper will examine the current state of progress of Kaband systems. Assessments will be made with respect to criteria such as: announced target markets and their appropriateness for the technology proposed; availability of desired technology to enable these systems to achieve their stated goals and a realistic assessment of when these technologies will be deployed; the availability of alternative terrestrial systems to address the same applications and their impact on the GEO Ka-band system target markets; and regulatory issues and paths to insure commercial access.     

航天器浮动电位的初步分析

为了研究表面充电引起的浮动电位情况,我们采用等效电容的方法分析了近赤道低轨道高度条件下航天器的等效电容及充电时间问题,初步总结了浮动电位对航天器可能产生的影响。根据计算结果可以认为在低轨道等离子体环境中航天器会达到浮动电位的平衡状态。
     

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.     

Analysis of satellite systems for the periodic survey of the Earth

Satellite systems for the periodic survey of a given range of the Earth’s latitudes have been analyzed. As a rule, the efficiency of the satellite systems is estimated based on the maximum interruption, i.e., the maximum time interval that appears when surveying. However, this performance cannot serve as a full criterion for the quality of the survey, since it does not reflect all survey interruptions with their frequencies. To adequately analyze the operation of the satellite system, it is necessary to use the frequency distribution function of the survey interruptions; its determination is a complex problem and has not yet been solved in the general case. In this paper, we propose a method for calculating the set of all interruptions and frequencies suitable for any multisatellite systems with an arbitrary structure. The method is based on the vector model of the Earth’s survey. To estimate the efficiency of the satellite system operation, a complex criterion has been recommended that takes into account all survey interruptions and their frequencies. Two examples of the application of the developed method have been presented.     

Analysis of Ballistic Structures of Multichannel Communication Satellite Systems on Precessing Elliptic Orbits

Two models of intersatellite communication channels in satellite systems on precessing elliptic orbits are considered. By assuming that these systems provide for a continuous survey of the Earth of the necessary multiplicity, algorithms of the analysis of ballistic system structures are constructed for these models in order to maintain multichannel global communication and organization of corresponding intersatellite channels. The algorithm operation is illustrated by numerical examples. This paper develops the results from [1–3], where a similar approach was advanced for the analysis of ballistic structures of satellite systems with simplified models of motion.