Detection technique for artificially illuminated objects in the outer solar system and beyond

Existing and planned optical telescopes and surveys can detect artificially illuminated objects, comparable in total brightness to a major terrestrial city, at the outskirts of the Solar System. Orbital parameters of Kuiper belt objects (KBOs) are routinely measured to exquisite precisions of<10(-3). Here, we propose to measure the variation of the observed flux F from such objects as a function of their changing orbital distances D. Sunlight-illuminated objects will show a logarithmic slope α ≡ (d log F/d log D)=-4, whereas artificially illuminated objects should exhibit α=-2. The proposed Large Synoptic Survey Telescope (LSST) and other planned surveys will provide superb data and allow measurement of α for thousands of KBOs. If objects with α=-2 are found, follow-up observations could measure their spectra to determine whether they are illuminated by artificial lighting. The search can be extended beyond the Solar System with future generations of telescopes on the ground and in space that would have the capacity to detect phase modulation due to very strong artificial illumination on the nightside of planets as they orbit their parent stars.     

星载激光测高地面数据处理设计研究

星载激光测高技术是对地观测系统中最为核心和前沿的信息获取技术之一,因其具有探测方向性好、测距精度高等特点,在地球科学领域中体现出了巨大的应用潜力。在ICESat/GLAS测高地面数据处理系统的基础上,针对将于今年发射的高分七号卫星的载荷特点,设计了一套星载激光测高地面数据处理系统软件。该软件可实现对星载激光测高数据的地面处理并生成3级数据产品,包含激光能量计算、波形分解和激光脚点定位等,以及相应各级产品的数据质量控制处理。利用高分七号仿真数据对该软件进行相应的性能测试,测试结果表明:该系统软件基本满足需求,已初步具备星载激光测高地面数据处理能力。     

卫星遥感数据的浏览查询技术

遥感卫星图像数据的预处理包括数据编目、存档管理、浏览查询和产品生产等部分。其中，浏览查询是向遥感数据的用户提供查询和检索卫星原始数据各级产品数据的手段，浏览查询系统的功能和性能直接影响到遥感数据的使用效率。本文介绍了新一代高码速率遥感卫星地面数据处理中浏览查询系统研制的主要技术。本文所研究的浏览查询技术已成功的运用到资源二号遥感卫星地面站的数据处理系统中。本文论述的数据处理技术将为其它遥感卫星地面数据处理系统的研制提供重要的帮助。     

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。     

Design of a 40/50 GHz satellite ground station for fade mitigation experiments

Due to the increasing demand in satellite capacity, driven by applications such as high-definition television (HDTV), 3D-TV and interactive broadband services, higher frequency bands will have to be exploited. The capacity on Ku-band is already becoming scarce and Ka-band systems are more commonly used. It can be expected that 40 and 50 GHz (Q and V band) will have to be used in the future. At these frequencies the wave propagation effects have a significant impact on the performance. The traditional approach of implementing large fade margins in the system design is not suitable as it leads to expensive ground terminals. Fade mitigation by adaptive coding and modulation (ACM) is a cost-efficient method. To investigate the Q/V-band for future commercial exploitation, ESA's ALPHASAT satellite will provide experimental payloads for communications and wave propagation experiments. In Graz a Q/V-band ground station is currently under development. It will be equipped with a 3 m tracking antenna, a 50 W Klystron amplifier and a 290 K LNA. Fade mitigation experiments will be conducted, initially using DVB-S2 modems which allow to vary the modulation scheme, the Forward Error Correction code and the symbol rate under control of the ACM computer. In addition, uplink power control can be combined with the ACM methods. A specially developed signal analyser provides precise measurement of the signal/noise ratio. In addition, propagation data will be available from a beacon receiver, also developed by Joanneum Research. Important goals of the experiment are to investigate the reliability of links under realistic operating conditions using ACM and to develop efficient ACM and signal/noise ratio measurement algorithms which can be later implemented in optimised modems for Q/V-band.The paper describes the ground station design and addresses the planned fade mitigation experiments.     

星地动态双向时间同步与测距算法

针对卫星运动对星地距离和钟差测量的不利影响,提出一种基于最小二乘拟合的星地动态双向时间同步与测距算法。在建立星地可视模型基础上,仿真了MEO运动卫星与地面时间同步站之间星地距离的变化规律,分析了卫星运动对星地双向时间同步与测距的主要不利影响。该算法首先利用星地双向时间同步数据分别生成星地距离和钟差拟合多项式,然后联合求解出运动卫星误差最小的星地距离与钟差。实验结果表明了该算法的合理性和科学性,在包含仿真误差的条件下,其时间同步精度优于3ns,测距精度优于3m。将其应用到各种空天应用系统的星地时间同步与测距中,可以消除卫星运动对双向时间同步与测距的不利影响,提高时间同步与测距精度。     

两星一地时差定位方法性能分析

针对同轨多星定位系统以及高低轨联合定位系统需要卫星数量多的特点,设想地面站和卫星联合定位体制。考虑到时差定位体制对卫星运动不敏感的特征,提出一星三地和两星一地2种定位体制,从定位场景、定位原理、理论定位误差和误差分布4个方面对定位效能分析。重点论述了两星一地时差定位误差的地理分布、时间分布以及受高度的影响,对将来的工程化应用提供支撑。     

空间太阳望远镜高速数据传输系统设计

空间太阳望远镜(SST)是中国未来重要的太阳观测卫星，中国科学院国家天文台和航天部五院目前正在开展该卫星的研制工作。本文介绍高数据传输速率(60Mbps)的科学数据传输系统(DTS)，该系统将SST每天采集的超大容量科学数据传送到卫星地面站，其协议与国内卫星地面站现有协议兼容。文中分析SST对DTS的系统需求；计算DTS系统星地传输链路的系统余量；侧重描述DTS的信道编码卡(CEC)的详细设计，包括设计原理、方法和实验室基带测试系统，CEC格式化海量存储器中的科学数据，插入伪随机编码(PN)及帧同步信号，生成的数据流适应四相相移键控(QPSK)射频调制及地面数据恢复系统的需求。本文最后讨论DLS检错和纠错编、解码(EDEC)的实现方法，以及如何分别利用软件、硬件或可编程器件实现系统功能优化分配。我们已研制出CEC地面样机及其测试设备，并成功验证了CEC的全新设计方法，如使用较低的工作频率完成高数据速率的传送等。     

A compact, light-weight high data-rate antenna system for remote-sensing orbiters and space exploration

Upcoming space missions utilizing hyperspectral or other high-resolution sensors will generate a vast amount of data in orbit. The average communication duration between a spacecraft in low Earth orbit (LEO) to a dedicated ground station is short and in addition, due to the high amount of data to be transferred at link times, a high-performance communication system on board of the satellite is indispensable.A solution that provides longer acquisition times with the ground station is to employ a high data-rate inter-satellite link to a geostationary relay satellite, which requires a flat, compact, steerable, light-weight yet robust antenna. Such an antenna system (antenna module plus pointing module) was developed for S-Band at the Institute of Astronautics (Technische Universität München), in cooperation with German space companies, research institutes and the German Aerospace Center (DLR). Its successful operation via the geostationary relay satellite Artemis was demonstrated in cooperation with ESA in 2007.This paper describes the evaluation of an antenna system in the Ka-Band, as a successor to be developed in the next two years for high data rates and the various applications of such an antenna system.     

Space solar array reliability: A study and recommendations

Providing reliable power over the anticipated mission life is critical to all satellites; therefore solar arrays are one of the most vital links to satellite mission success. Furthermore, solar arrays are exposed to the harshest environment of virtually any satellite component. In the past 10 years 117 satellite solar array anomalies have been recorded with 12 resulting in total satellite failure. Through an in-depth analysis of satellite anomalies listed in the Airclaim's Ascend SpaceTrak database, it is clear that solar array reliability is a serious, industry-wide issue. Solar array reliability directly affects the cost of future satellites through increased insurance premiums and a lack of confidence by investors. Recommendations for improving reliability through careful ground testing, standardization of testing procedures such as the emerging AIAA standards, and data sharing across the industry will be discussed. The benefits of creating a certified module and array testing facility that would certify in-space reliability will also be briefly examined. Solar array reliability is an issue that must be addressed to both reduce costs and ensure continued viability of the commercial and government assets on orbit.     

基于SVM和"嫦娥一号"数据的月球表面亮温分布

月球表面的微波辐射亮度温度分布与月表物质的物理化学和地理分布特性密切相关.为了分析月球表面微波辐射亮温的分布特点,利用支持向量机(SVM)方法对嫦娥一号(CE-1)绕月卫星搭载的微波辐射计获得的2C级亮温数据建立回归分析模型,并利用粒子群算法优化SVM回归模型,建立了月球表面不同地理位置的4个频率通道(3GHz,7.8GHz,19.35GHz,37GHz)的微波辐射亮温与时间的关系,获得了这4个频率的微波辐射亮温在月表很窄时间段的全球分布,因而显示出了更多的细节特征.最后对这些特征进行了描述并对影响月球表面亮温的因素进行了讨论.     

Tracking and data relay satellite system: NASA's new spacecraft data acquisition system

The growth in NASA's ground network complexity and cost triggered a search for an alternative. Through a lease service contract, Western Union will provide to NASA 10 years of space communications services with a Tracking and Data Relay Satellite System (TDRSS). A constellation of four operating satellites in geostationary orbit and a single ground terminal will provide complete tracking, telemetry and command service for all of NASA's Earth orbital satellites below an altitude of 12,000 km. The system is shared: two satellites will be dedicated to NASA service; a third will provide backup as a shared spare; the fourth satellite will be dedicated to Western Union's Advanced Westar commercial service. Western Union will operate the ground terminal and provide operational satellite control. NASA's Network Control Center will provide the focal point for scheduling user services and controlling the interface between TDRSS and the rest of the NASA communications network, project control centers and data processing facilities. TDRSS single access user spacecraft data systems should be designed for efficient time shared data relay support. Reimbursement policy and rate structure for non-NASA users are currently being developed.     

Naval EarthMap Observer (NEMO) program and the Naval Space Science and Technology Program Office

In February 1997 the Chief of Naval Research chartered the Naval Space Science and Technology (S&T) Program Office, at the Office of Naval Research, to operate as the central point of contact for the Department of the Navy's (DON's) S&T activities in space. The Office was chartered to enhance the DON's space efforts through interdepartmental integration and linkage with external Department of Defense (DOD) commands and government agencies. The Office's goal is to optimize a plan for S&T coherency, synergy, and relevancy to effect technology transition to the DON's Systems Commands or Program Executive Offices (PEO's) while developing an investment strategy that accommodates and leverages the commonality of commercial and consumer thrust areas and products.

This paper will focus on the “Flagship” Naval Space S&T Program, the Naval EarthMap Observer (NEMO) Program, as one example of how the Office is executing its mission. It will discuss how, through NEMO, the Navy is able to leverage commercial industry and other US government agency requirements and resources to meet unique Naval needs. Finally, the paper will discuss the specifics of NEMO, the Navy's roles and responsibilities and how the Navy will use NEMO in its mission to characterize the littoral regions of the world.

Through the NEMO satellite system, the Navy will develop a large hyperspectral imagery database which will be used to characterize and model the littoral regions of the world. NEMO will provide images using its Coastal Ocean Imaging Spectrometer (COIS) Instrument along with a co-registered 5m Panchromatic Imager (PIC). With 210 spectral channels over a bandpass of 0.4 to 2.5μm and very high signal-to-noise ratio (SNR), the COIS instrument is optimized for the low reflectance environment of the littoral region. COIS will image over a 30km wide swath with a 60m Ground Sample Distance (GSD), and can image at a 30m GSD with ground motion compensation. A 10:30am, sun-synchronous circular orbit of 605km enables continuous repeat coverage of the whole earth. A unique aspect of the system is the spectral feature extraction and data compression software algorithm developed by the Naval Research Laboratory (NRL) called the Optical Real-Time Spectral Identification System (ORA-SIS). ORASIS employs a parallel, adaptive hyperspectral method for real-time scene characterization, data reduction, background suppression, and target recognition. The use of ORASIS is essential for management of the massive amounts of data expected from the NEMO HSI system, and for development of Naval products. Specific Naval products include bathymetry, water clarity, bottom type, atmospheric visibility, bioluminescence, beach characterization, under-water hazards, total column atmospheric water vapor, and detection and mapping of sub-visible cirrus. Demonstrations of timely downlinks of real-time hyperspectral imagery data to the Naval warfighter are also being developed. The NEMO satellite is planned for launch in mid-2000 followed by an operational period of 3 to 5 years.     

Space solar array reliability: A study and recommendations

Providing reliable power over the anticipated mission life is critical to all satellites; therefore solar arrays are one of the most vital links to satellite mission success. Furthermore, solar arrays are exposed to the harshest environment of virtually any satellite component. In the past 10 years 117 satellite solar array anomalies have been recorded with 12 resulting in total satellite failure. Through an in-depth analysis of satellite anomalies listed in the Airclaim's Ascend SpaceTrak database, it is clear that solar array reliability is a serious, industry-wide issue. Solar array reliability directly affects the cost of future satellites through increased insurance premiums and a lack of confidence by investors. Recommendations for improving reliability through careful ground testing, standardization of testing procedures such as the emerging AIAA standards, and data sharing across the industry will be discussed. The benefits of creating a certified module and array testing facility that would certify in-space reliability will also be briefly examined. Solar array reliability is an issue that must be addressed to both reduce costs and ensure continued viability of the commercial and government assets on orbit.     

The data compression problem for the “GAIA” astrometric satellite of ESA

Space-based astrometry has a great tradition at ESA. The first space-based astrometric satellite in history, “Hipparcos”, was launched by ESA in 1989 and, in spite of orbital problems, was able to accomplish almost all of its tasks until it was finally shut down in 1993. The results of the Hipparcos mission were published by ESA in 1997 in the form of six CD-ROMs: the Hipparcos Catalogue contains 118,218 entries with median astrometric precision of around 1 milliarcsec, and specific results for double and multiple systems. In practice, Hipparcos drew for the first time the three-dimensional “map” of the spherical region of the Galaxy surrounding the Sun and having a radius of roughly 1,000 light years.

Then, in 1995, ESA launched the study of a new astrometric satellite, named “GAIA” and about a hundred times more powerful than Hipparcos, i.e. with median astrometric precision of around 10 microarcsec. This new satellite is intended to measure the parallaxes of over 50 million stars in the Galaxy, at least for the brightest stars, and this would mean to “draw” the three-dimensional map of the whole Galaxy, reaching out even to the Magellanic Clouds, 180,000 light years away.

The team of European scientists and engineers now designing GAIA, however, is facing hard technological difficulties. One of these is the design and coding of radically new and ultra-powerful mathematical algorithms for the on-board compression of the 50-million-stars data that GAIA will send to Earth from its intended geostationary orbit. Preliminary estimates of the raw data rates from the GAIA focal plane, in fact, are of the order of a few Gigabits per second. To reduce the data stream to the envisaged telemetry link of 1 Megabit per second, on-board data compression with a 1 to 1,000 ratio is the target. Clearly, this is far beyond the capabilities of any lossless compression technique (enabling compression ratios of 1 to some tens), and so some “wise” lossy compression mathematical procedure must be adopted.

In this paper a GAIA-adapted lossy data compression technique is presented, based on the Karhunen-Loève Transform (KLT). The essence of this method was already used by NASA for the Galileo mission when the large antenna got stuck and the mission was rescued by re-programming the on-board computer in terms of the KLT. That transform was officially named ICT — “Integer Cosine Transform” — by the NASA-JPL team led by Dr. Kahr-Ming Cheung. But the KLT here described for GAIA will of course differ from the JPL one in many regards, owing to the advances in computer technology.

Finally, estimates are also given about the possibility of using the KLT for onboard data compression in case GAIA is going to be put into orbit around the Lagrangian point L2 of the Earth-Sun system, and, above all, in case the number of stars to be observed is actually raised from 50 millions to one billion, as ESA currently appears to be likely to pursue.     

The development of a Russian communication satellite of small class, operating in the geostationary and high-elliptical orbits

In 1994–1995 Lavochkin Association (Russia) together with the other enterprises in accordance with technical requirements of the Russian Space agency, developed a new Russian communication satellite of a small class that will operate in both the geostationary (GSO) and high-elliptical (HEO) orbits. This satellite may be injected into operational orbits using a SOYUZ-2 launch vehicle (LV) and a FREGAT upper stage (US) from Plesetsk and Baykonur space launch sites (SLS).The main reason for creating such a satellite was to decrease the cost of the support and development of the Russian communication geostationary satellites group.Russian satellites Horizont, Express, Ekran and Gals, which operate in GSO, are the basis of the space segment for communications, radio and TV broadcasting. All of these satellites are injected into GSO by the PROTON LV. PROTON is a launch vehicle of a heavy class. The use of a middle class LV instead of a heavy class will allow to reduce considerably the launch cost. The change of a heavy class LV to a LV of middle class determined one economic reason for this project. Besides, the opportunity to launch S/C into GSO from Russian Plesetsk SLS increases the independence of Russia in the domain of space communications, despite the presence of the contract with Kazachstan about the rent of Baykonur SLS. Finally, use of small satellites with a rather small number of transponders is more effective than the use of big satellites. It will allow also to increase a satellite group (by the launch of additional satellites) precisely in accordance to the development of the ground segment.     

FY-2C星地面应用分系统指令与数据获取站

介绍了风云二号(FY-2)C星地面应用分系统数据与指令接收站(CDAS)的主要技术指标、工作流程,以及与C星的星地接口与地面应用分系统其他部分的接口.说明了CDAS的天伺馈、信道、图像获取(IAS)、三点测距(TRRR)、数据收集(DCP)、遥测遥控(TT&C)、卫星模拟器、标校、时间统-、低速信息传输(LRIT)信息编码与发送等子系统的组成与功能.阐述了C星CDAS的设计原则,以及用群调技术实现DCP的数据解调、用扩频伪码进行TRRR定位、图像处理、TT&C增加图形化界面控制、正交相移键控(QPSK)解调器抗长连"1"功能等关键技术.在轨测试和试运行期间,C星的CDAS不仅解决暴露的问题,而且进行适应性调整.验收前测试结果表明,其功能及技术指标满足业务运行要求,设备工作正常、性能稳定.     

多体卫星地面物理仿真的一致性研究

三轴气浮台不能直接用于多体卫星的地面物理仿真实验,这是由于部件转动引起台体 的质心变化,进而产生重力静不平衡力矩,使仿真过程无法进行,因此需要质心补偿系统对 气浮台的重力静不平衡力矩进行补偿。本文通过对多体卫星动力学和气浮台动力学的比较, 分析了在重力场中的地面物理仿真系统与真实卫星的动力学特性的不同点,给出地面物理仿 真系统能完全模拟真实卫星运动的一致性条件,并进行了数学仿真。当转动附件的质心在转 动轴或转动中心上时,气浮台系统可以完全模拟卫星系统的质量特性和力学耦合特性,否则 ,多体气浮台系统和多体卫星系统的动力学耦合特性不完全一致,需要采取一定的方法进行 补偿。
     

一种航天器星光折射连续导航方法

针对星光折射航天器自主导航应用中观测缺失导航折射星造成误差上升甚至导航发散的情况，提出一种适用于航天器星光折射导航空白段的新方法。阐述了星光折射导航机理，给出了导航星观测窗口，进而设计基于神经网络的导航算法，该方法充分利用已有信息，有效预测并修正航天器状态信息，使星光空白段前后导航误差变化平稳，发挥星光折射间接敏感地平精度高的特点，保证了航天器高精度定位，且不需要添加硬件设备，算法简洁、实用。最后，通过计算机仿真校验了该导航方法的有效性。