ERDSAT,a satellite concept for Earth observations with combined optical and microwave payload

The concept of a European remote sensing satellite (ERDSAT) launched by ARIANE is characterized by a model payload, consisting of a synthetic aperture radar (SAR) and an optical multispectral scanner with 9 channels, for land applications or coastal zone missions. The mission goal of ERDSAT is based on European user requrements where a strong need for optical and microwave sensor operation on board the same satellite in a simultaneous or sequential mode is expressed. A data collection system is included. The proposed spacecraft is three-axes-stabilized and has a Sun-synchronous, near polar circular orbit with 750 km altitude. The selected configuration separates payload module and bus module. A thermostable carbon fibre grating structure is the central framework of the satellite. Each major subsystem is housed in a separate compartment and can be integrated and tested individually. First mass estimates resulted in 450 kg for the payload and 880 kg for the bus. The maximum power needed is 1750 W (for 6 min three times a day), which will be provided by a 1330 W solar array and two batteries. A “low cost” model philosophy is defined; the time schedule envisages a program start in late 1980 and a launch possibility end of 1985.     

Multiobjective optimization applied to structural sizing of low cost university-class microsatellite projects

In recent years, there has been continuing interest in the participation of university research groups in space technology studies by means of their own microsatellites. The involvement in such projects has some inherent challenges, such as limited budget and facilities. Also, due to the fact that the main objective of these projects is for educational purposes, usually there are uncertainties regarding their in orbit mission and scientific payloads at the early phases of the project. On the other hand, there are predetermined limitations for their mass and volume budgets owing to the fact that most of them are launched as an auxiliary payload in which the launch cost is reduced considerably. The satellite structure subsystem is the one which is most affected by the launcher constraints. This can affect different aspects, including dimensions, strength and frequency requirements. In this paper, the main focus is on developing a structural design sizing tool containing not only the primary structures properties as variables but also the system level variables such as payload mass budget and satellite total mass and dimensions. This approach enables the design team to obtain better insight into the design in an extended design envelope. The structural design sizing tool is based on analytical structural design formulas and appropriate assumptions including both static and dynamic models of the satellite. Finally, a Genetic Algorithm (GA) multiobjective optimization is applied to the design space. The result is a Pareto-optimal based on two objectives, minimum satellite total mass and maximum payload mass budget, which gives a useful insight to the design team at the early phases of the design.     

安全约束下的空间翻滚目标涡流消旋稳定控制

针对空间翻滚目标涡流消旋任务执行效率低和抵近安全无保证的问题，首先基于椭球包络法给出了服务星机动轨迹的直接线性凸化安全约束，以确保机动过程的安全性和最优轨迹跟踪问题的有限时间可解性；设计了垂直构型下空间消旋任务的抵近期望轨迹以增强服务星消旋力矩的作用强度，缩短任务周期。在此基础上，提出了一种反馈线性化的收缩模型预测控制(FLC MPC)算法，有效跟踪所提出的期望轨迹，并严格保证安全约束及控制输入约束下受控系统的稳定性。最后，利用所提出的控制方法对阿丽亚娜 4火箭上面级进行消旋仿真，结果表明该方法能有效提高消旋效率，并保证服务星的安全稳定。     

遥感卫星在轨故障统计与分析

对遥感卫星1988年—2014年的在轨故障数据进行分类研究发现:控制、载荷、测控和数传是遥感卫星在轨故障发生比例最高的4个分系统;故障主要发生于在轨第1年;环境、设计和器件类故障为主要的在轨故障类型;大多数故障可以通过在轨自主诊断、地面操作等方式及时予以解决, 对遥感卫星完成任务的固有能力影响较小;各分系统的在轨故障特点各不相同。文章最后针对故障原因, 提出了增加遥感卫星的地面试验与测试、加强抗辐射加固设计和开展基于在轨故障规律的分系统技术状态控制等对策, 以降低卫星的在轨故障率, 保证卫星在轨可靠、安全运行。     

面向卫星通信系统的低成本超表面相控阵技术

低轨通信卫星系统因其传输延迟小、通信容量大、发射运营成本低等优势,受到了国内外的广泛关注。然而,低轨通信卫星技术的发展对星载天线系统提出了挑战。为提高卫星星座的通信容量以及实现对用户的跟踪覆盖,波束扫描、波束可重构及多波束覆盖不可或缺。在低成本建设运营的背景下,迫切地需要一种低成本的天线系统方案。作为一种低成本新型相控阵技术,综述了超表面相控阵天线技术及其在波束调控中的应用。首先对超表面天线波束形成的方法进行了简单的研究,之后介绍了超表面电磁调控的机理以及实现可重构的手段,最后介绍了超表面相控阵天线在波束形成、波束扫描、多波束产生中的应用。该技术相较于传统相控阵技术,大幅降低了成本,且在电磁波极化、频率调控中展现出巨大的灵活性。通过对该技术的综述,展望了超表面相控阵在低轨通信卫星中的应用。     

A survey and assessment of the capabilities of Cubesats for Earth observation

In less than a decade, Cubesats have evolved from purely educational tools to a standard platform for technology demonstration and scientific instrumentation. The use of COTS (Commercial-Off-The-Shelf) components and the ongoing miniaturization of several technologies have already led to scattered instances of missions with promising scientific value. Furthermore, advantages in terms of development cost and development time with respect to larger satellites, as well as the possibility of launching several dozens of Cubesats with a single rocket launch, have brought forth the potential for radically new mission architectures consisting of very large constellations or clusters of Cubesats. These architectures promise to combine the temporal resolution of GEO missions with the spatial resolution of LEO missions, thus breaking a traditional trade-off in Earth observation mission design. This paper assesses the current capabilities of Cubesats with respect to potential employment in Earth observation missions. A thorough review of Cubesat bus technology capabilities is performed, identifying potential limitations and their implications on 17 different Earth observation payload technologies. These results are matched to an exhaustive review of scientific requirements in the field of Earth observation, assessing the possibilities of Cubesats to cope with the requirements set for each one of 21 measurement categories. Based on this review, several Earth observation measurements are identified that can potentially be compatible with the current state-of-the-art of Cubesat technology although some of them have actually never been addressed by any Cubesat mission. Simultaneously, other measurements are identified which are unlikely to be performed by Cubesats in the next few years due to insuperable constraints. Ultimately, this paper is intended to supply a box of ideas for universities to design future Cubesat missions with high scientific payoff.     

同步串行总线在通信卫星转发器中的应用

提出了一种适用于通信卫星转发器分系统测控数据传输的5线制同步串行总线,支持30个终端同时接入,改变了通信卫星平台传统的点对点式的遥测遥控信息传输方式,大大减少了通信舱内电缆数量;并在某通信卫星载荷舱上进行了应用,使卫星载荷舱质量减少几十千克,提升了卫星平台的有效载荷能力。文章设计的串行总线提供标准的接口电路,有利于有效载荷设备的扩容,可以推广至更多的有效载荷设备,构成其之间的测控信息网络。     

基于Cubesat平台的874 GHz冰云探测仪设计

冰云探测对气候预测有重要价值,但因冰云粒子的影响,传统气象观测方法很难有效观测气候。太赫兹波的信号带宽较宽、波束较窄,在冰云探测上比使用微波毫米波更具优势。太赫兹冰云探测仪作为被动接收设备,具有体积小、功耗小的特点,与成本低、研发周期短、可以实现组网观测的Cubesat卫星平台有较高的契合度。以冰云探测为背景,分析太赫兹冰云探测仪系统指标,设计874GHz接收机系统的链路。在确保接收机系统性能的同时注重简化链路,减少体积功耗,以适应Cubesat平台,并结合工程经验在链路设计时采取预留增益余量、加入隔离器增强匹配等措施保证工程上的可实现性。最后对接收机链路进行ADS仿真,仿真结果能够满足冰云探测仪对接收机指标的需求。     

卫星结构中的非金属材料

介绍了各种复合材料、胶粘剂、高分子材料和工业陶瓷等非金属材料的性能及其在卫星结构中的应用情况。强调了非金属材料在提高卫星性能、减轻卫星结构质量，以及增大卫星有效栽荷方面的作用。最后指出了卫星结构材料高性能、多功能、复合化、智能化、低成本以及高环境相容性的发展趋势。     

Design and implementation of the GPS subsystem for the Radio Aurora eXplorer

This paper presents the design and implementation of the Global Positioning System (GPS) subsystem for the Radio Aurora eXplorer (RAX) CubeSat. The GPS subsystem provides accurate temporal and spatial information necessary to satisfy the science objectives of the RAX mission. There are many challenges in the successful design and implementation of a GPS subsystem for a CubeSat-based mission, including power, size, mass, and financial constraints. This paper presents an approach for selecting and testing the individual and integrated GPS subsystem components, including the receiver, antenna, low noise amplifier, and supporting circuitry. The procedures to numerically evaluate the GPS link budget and test the subsystem components at various stages of system integration are described. Performance results for simulated tests in the terrestrial and orbital environments are provided, including start-up times, carrier-to-noise ratios, and orbital position accuracy. Preliminary on-orbit GPS results from the RAX-1 and RAX-2 spacecraft are presented to validate the design process and pre-flight simulations. Overall, this paper provides a systematic approach to aid future satellite designers in implementing and verifying GPS subsystems for resource-constrained small satellites.     

带有柔性补偿的柔性关节空间机器人的增广自适应控制及关节振动抑制

The problems of joint motion control and flexible vibration suppression of a flexible joint space based robot for manipulating an unknown payload are studied. Based on the system linear momentum conservation and the Lagrange method, the under actuated dynamics model of the space robot is established. For convenience of the design of its control system, the system is divided into both fast and slow subsystems by using the joint flexibility compensation technique and the singular perturbation theory. A torque differential feedback controller is proposed for the fast subsystem to suppress the joints’ flexible vibration, meanwhile an adaptive control scheme based on the augmentation approach is designed for the slow subsystem to realize the joint trajectory asymptotic tracking under the condition of unknown payload parameters. Because of introduction of the flexibility compensation technique, the presented control scheme can equivalently increase the joint stiffness, and it is suitable to control the space robot systems with low joint stiffness. Moreover, the effect of unknown parameters is real time compensated by its adaptive controller, and then the specified joint motion task is achieved precisely. The effectiveness of the scheme is verified by the corresponding simulation results.     

A DLR small satellite mission for the investigation of hot spots, vegetation and clouds

Starting from their FIRES proposal [1]the DLR makes a new approach in the design of a small satellite mission dedicated to hot spot detection and evaluation: the BIRD mission. The new approach is characterized by a strict design-to-cost philosophy. A two-channel infrared sensor system in combination with a Wide-Angle Optoelectronic Stereo Scanner (WAOSS) shall be the payload of a small satellite (80kg) considered for piggyback launch. So the launch is not a main cost driver as for other small satellite missions with dedicated launchers. The paper describes the mission objectives, the scientific payload, the spacecraft bus, and the mission architecture of a small satellite mission dedicated to the investigation of hot spots (forest fires, volcanic activities, burning oil wells or coal seams), of vegetation condition and changes and of clouds. The paper represents some results of a phase A study and of the progressing phase B.     

FPGA-based operational concept and payload data processing for the Flying Laptop satellite

Flying Laptop is the first small satellite developed by the Institute of Space Systems at the Universität Stuttgart. It is a test bed for an on-board computer with a reconfigurable, redundant and self-controlling high computational ability based on the field programmable gate arrays (FPGAs). This Technical Note presents the operational concept and the on-board payload data processing of the satellite. The designed operational concept of Flying Laptop enables the achievement of mission goals such as technical demonstration, scientific Earth observation, and the payload data processing methods. All these capabilities expand its scientific usage and enable new possibilities for real-time applications. Its hierarchical architecture of the operational modes of subsystems and modules are developed in a state-machine diagram and tested by means of MathWorks Simulink-/Stateflow Toolbox. Furthermore, the concept of the on-board payload data processing and its implementation and possible applications are described.     

FPGA-based operational concept and payload data processing for the Flying Laptop satellite

Flying Laptop is the first small satellite developed by the Institute of Space Systems at the Universität Stuttgart. It is a test bed for an on-board computer with a reconfigurable, redundant and self-controlling high computational ability based on the field programmable gate arrays (FPGAs). This Technical Note presents the operational concept and the on-board payload data processing of the satellite. The designed operational concept of Flying Laptop enables the achievement of mission goals such as technical demonstration, scientific Earth observation, and the payload data processing methods. All these capabilities expand its scientific usage and enable new possibilities for real-time applications. Its hierarchical architecture of the operational modes of subsystems and modules are developed in a state-machine diagram and tested by means of MathWorks Simulink-/Stateflow Toolbox. Furthermore, the concept of the on-board payload data processing and its implementation and possible applications are described.     

SSETO—Small Satellite for Exoplanetary Transit Observation

SSETO is the result of a phase-A study in context of the small satellite program of the University of Stuttgart that demonstrates the capability of a university institute to build a small satellite with a budget of 5 million Euro. The satellite will be capable of observing exoplanets in a Neptune–Earth scale and obtaining data of interstellar dust. Due to a system failure of NASA?s Kepler mission, there is currently (October 2013) a lack of satellites searching for exoplanets. This paper details the design of subsystems and payload, as well as the required test tasks in accordance with the mission profile at a conceptional level. The costs for standard spacecraft testing and integration tasks are included, but not those of launch, ground support, operations and engineer working hours.     

用于热真空环境下整星微波无线测试的低PIM吸波热沉研制

随着通信卫星技术的发展,收发共用已成为通信卫星有效载荷常用的设计方法,在这种情况下,无源互调(passive intermodulation,PIM)问题就显得尤为突出。为了完成整星及转发器分系统在热真空环境下的PIM指标测试,利用碳化硅吸波材料研制了一种低PIM吸波热沉,并利用该吸波热沉建立了指标小于150 dBm的低PIM测试环境,同时兼具热流模拟功能和微波功率耐受能力。在热真空环境下圆满完成了国内首次有整星参与的微波载荷无线PIM测试试验。     

通信卫星灵活载荷技术综述

通信卫星逐步由高轨地球同步轨道卫星向高、中、低轨结合的全球覆盖卫星方向发展,多业务和多重覆盖的发展趋势对通信卫星的灵活性提出了更高的要求。通信卫星配备灵活载荷已经成为重要发展方向,对面向个人用户的高通量通信卫星及高、中、低轨结合的组网通信卫星来说尤为重要。配备灵活载荷的通信卫星能实现端到端业务,能灵活调整覆盖区,实现灵活组网,并提升资源利用率。分析了国内外通信卫星灵活载荷的发展动态,介绍了通信卫星灵活载荷的技术特点,并给出了有效载荷方案,最后阐述了通信卫星灵活载荷发展的关键技术及发展思路。     

VentureStar… reaping the benefits of the X-33 program

Major X-33 flight hardware has been delivered, and assembly of the vehicle is well underway in anticipation of its flight test program commencing in the summer of 1999. Attention has now turned to the operational VentureStar^TM, the first single-stage-to-orbit (SSTO) reusable launch vehicle. Activities are grouped under two broad categories: (1) vehicle development and (2) market/business planning, each of which is discussed. The mission concept is presented for direct payload delivery to the International Space Station and to low Earth orbit, as well as payload delivery with an upper stage to Geosynchronous Transfer Orbit (GTO) and other high energy orbits. System requirements include flight segment and ground segment. Vehicle system sizing and design status is provided including the application of X-33 traceability and lessons learned. Technology applications to the VentureStar^TM are described including the structure, propellant tanks, thermal protection system, aerodynamics, subsystems, payload bay and propulsion. Developing a market driven low cost launch services system for the 21st Century requires traditional and non-traditional ways of being able to forecast the evolution of the potential market. The challenge is balancing both the technical and financial assumptions of the market. This involves the need to provide a capability to meet market segments that in some cases are very speculative, while at the same time providing the financial community with a credible revenue stream. Furthermore, the market derived requirements need to be assessed so as not to impose unnecessary requirements on the vehicle design that add unreasonable cost to the development of the system, yet provides the right capabilities for new markets that could be triggered by dramatically lower space transportation prices.     

旋转失效卫星的运动观测及消旋接触方案设计

以旋转失效卫星的消旋为研究背景,提出一种双重光流约束的特征点运动跟踪识别方法。该方法利用双目视觉,可实现对非合作旋转失效卫星的运动观测,并为机械臂消旋操作提供接触方案。首先,跟踪识别序列图像中稳定存在的特征点并记录其轨迹,采用频域分析的方法检测特征点轨迹的变化频率,从而获取目标旋转角速度,通过地面物理实验,验证所提目标运动观测的有效性;随后,利用特征点轨迹分析目标的运动包络与适宜接触区域,并根据目标运动特性和接触消旋的时间约束,给出完成消旋的接触强度约束,继而得到机械臂的操作性能需求,为接触式消旋的工程实践提供参考。     

冗余空间机械臂抓捕自旋卫星后的消旋控制

旨在提出一种运动学冗余空间机器人抓捕自旋卫星后的消旋策略和协调控制方法。首先,给出运动学冗余空间机器人捕获目标后的动力学模型,作为协调控制器设计基础。然后,基于四阶Bézier曲线和满足特定约束的自适应微分进化(Differential Evolution, DE)算法提出抓捕后的最优消旋与路径规划策略,最优消旋策略中同时考虑对消旋时间和控制力矩进行优化。提出一种跟踪所设计参考轨迹的协调控制方法,调整基座的姿态达到期望值。所提方法有效地衰减了自旋卫星的初始角速度,同时实现对基座姿态的控制。文末给出利用7 DOF冗余空间机械臂消除目标自旋运动的仿真结果,表明所提方法的有效性。