The economics of large orbital communications systems

This paper examines the economics of a very large satellite in geostationary orbit. Present day charges for satellite transponders are used to show that the seemingly high cost of this type of platform is rapidly repaid. Several orbit locations are selected on the basis of current usages and a satellite is configured with the power and mass requirements identified. Costs for the total space segment of a large platform are extrapolated using established cost histories of both satellites and launch vehicles. It is shown that the original investment is repaid in less than three years. After this time, the platform continues to earn revenue.     

低轨星座对静止轨道卫星同频干扰指标研究

随着全球低轨星座系统的快速部署及应用,非静止轨道卫星对静止轨道卫星系统的同频干扰问题日益凸显。为保护静止轨道卫星系统不受有害干扰,国际电联现行无线电规则中规定了非静止轨道卫星系统应满足的等效功率通量密度限值或干扰噪声比限值,但所适用频段及限值标准仍在不断修订完善中。为了精确定量评估低轨星座对静止轨道卫星的同频干扰,通过对等效功率通量密度限值和干扰噪声比限值的确定方法及演进历程进行研究,分析了上述限值与静止轨道卫星实际被干扰的对应关系,并以典型倾斜轨道星座和极地轨道星座为例,分析了不同干扰指标对卫星系统间干扰判定结果的影响,当静止轨道卫星系统的实际被干扰门限低于国际电联制定等效功率通量密度限值选用的参考门限时,建议低轨星座选择干扰噪声比限值作为开展频率干扰分析与判定的依据。     

地球静止轨道卫星硅太阳电池在轨特性分析

空间辐照效应的影响,使太阳电池输出功率随其在轨时间的推移而逐渐衰减。文章以2颗在轨的地球静止轨道卫星为研究对象,对某类我国自主研发的硅太阳电池的在轨输出功率衰减率进行了分析。并针对所获得的相关遥测参数,通过数值统计与数学分析的方法,采用确定的计算公式得出太阳电池阵的总输出电流,用以表征其输出功率。文章提出了一种曲线平移...     

Technical and economical comparison between a modular geostationary space platform and a cluster of satellites

In recent years, the identification of a large number of telecommunication missions reflects a growing demand for the provision of a large variety of communications and data transmission services performed by a space segment.

At present, communication space segment use a single operational satellite per orbit position. However, the expected increase of communication channels per space segment will lead to a corresponding increase of satellite mass and size which could exceed the capabilities of existing launch vehicles in terms of mass and volume requirements. Those considerations, coupled with the threatening saturation of the geostationary orbit, lead to the conclusion that an optimal space segment concept must be defined on a technical as well as economical point of view.

Two main concepts may be envisaged: one is a large platform, which can be assembled either in geostationary orbit (resulting in several launches, rendez-vous and docking), or in low earth orbit by using the STS; the other concept is a cluster of satellites.

These candidate concepts are designed to meet the requirements of a reference mission. They are characterized by the required number of modules to be launched, the type of launcher, the new subsystems or equipments to be developed. The concepts are evaluated following technical criteria such as adaptability to other missions, flexibility, growth potential. A cost/benefit evaluation of each solution is presented. A comparison between the different concepts is then made on the basis of the technical/economical attractiveness of each solution.     

我国“风云”气象卫星及其应用的回顾与展望

气象卫星和卫星气象是气象现代化的重要标志。自1988年至今,我国已先后成功发射了4颗风云-1极轨气象卫星和4颗风云-2静止气象卫星,顺利完成了极轨和静止两个系列气象卫星从试验到业务卫星的跨越。由“风云”气象卫星获取的地球大气和地表信息已广泛应用于天气预报、气候预测、环境和自然灾害监测与分析等多个领域。文章介绍了我国“风云”系列气象卫星的发展历程、地面应用系统组成、“风云”卫星产品及应用,最后展望了“风云”系列气象卫星的发展。     

微波辐射计静止轨道遥感试验技术

在地球静止轨道上对大气进行微波遥感探测尚无先例。为验证静止轨道微波探测仪器关键技术,研究高轨微波辐射传输特性并积累遥感数据,研制了微波探测试验载荷,搭载于风云四号A星进行在轨试验。微波探测载荷采用真实孔径圆周扫描体系,配置双频段(183,425 GHz)五通道。载荷在轨试验中,各项指标正常,183GHz频段灵敏度优于0.5K,425GHz灵敏度优于1.9K,性能稳定并超过3个月考核寿命。对微波探测载荷183GHz与极轨载荷先进技术微波辐射计(advanced technology microwave sounder,ATMS)进行亮温交叉比对的结果显示,两者亮温相近,变化趋势一致,验证了探测数据的有效性。载荷还在静止轨道获取了极轨无法探知的3K/h量级亮温变化,并在风云四号A星姿态调整期间完成了静止轨道微波遥感成像。验证了在静止轨道上进行真实孔径体制微波遥感探测的有效性。     

Near-optimal geostationary transfer maneuvers with cooperative en-route inspection using hybrid optimal control

This research investigates the performance of bi-level hybrid optimal control algorithms in the solution of minimum delta-velocity geostationary transfer maneuvers with cooperative en-route inspection. The maneuvers, introduced here for the first time, are designed to populate a geostationary constellation of space situational awareness satellites while providing additional characterization of objects in lower-altitude orbit regimes. The maneuvering satellite, called the chaser, performs a transfer from low Earth orbit to geostationary orbit, during which it performs an inspection of one of several orbiting targets in conjunction with a ground site for the duration of the target?s line-of-site contact with that site. A three-target scenario is used to test the performance of multiple bi-level hybrid optimal control algorithms. A bi-level hybrid algorithm is then utilized to solve fifteen-, and thirty-target scenarios and shown to have increasing benefit to complete enumeration as the number of targets is increased. Results indicate that the en-route inspection can be accomplished for a small increase in the delta-velocity required for a simple transfer to geostationary orbit given the same initial conditions.     

地球静止轨道微波辐射计技术

静止轨道微波辐射计可实现全天时、全天候、高频次云雨大气观测,在台风、流域性强降水探测和预报方面发挥重要作用。但在波束扫描、多频复用、系统定标等方面的运用存在较大困难,世界上尚无在轨应用先例。现从探测需求出发,对静止轨道微波辐射计进行了系统方案设计。提出了卫星平台与辐射计部件快慢结合扫描的方法,以解决波束扫描和系统定标难题;提出了低频选入射角层叠式布局准光学频段分离方法,以解决多频段复用难题。研制了微波辐射计原理样机,通过实验室和外场试验验证了系统设计,为静止轨道微波探测卫星研制提供了一定指导。     

全球卫星搜索与救援系统的现状与未来

全球卫星搜救系统(COSPAS-SARSAT)在海事搜救和飞机救援等领域已经发挥了巨大的作用。文章旨在对已有的低轨道(LEO)和静止轨道(GEO)系统的工作原理进行分析,并与建设中的中轨道(MEO)系统比较,以得出中轨道系统的优势,并对全球卫星搜救系统的未来发展进行分析。     

同步轨道共位卫星差分CEI测量技术

同步轨道卫星共位是指在一个地球同步轨道±0．1°的窗口上放置2颗或2颗以上的卫星。文章介绍了同步轨道卫星多星共位的必要性和差分连接端站干涉测量的原理,对同步轨道共位卫星位置测量精度进行分析,得出结论：差分连接端站干涉测量技术能够满足同步轨道共位卫星位置测量的要求。     

Comparative economics of very high capacity communications satellites

Technology advances expected by the late 1980 or early 1990 time period will allow the construction of powerful and complex communications satellites with large multibeam antennas and very many transponders, and their operation and maintenance in geostationary orbit. The high sensitivity and effective radiated power of such satellites will enable the Earth stations using them to shrink dramatically in size and cost, thus becoming readily available to very large numbers of users as well as making possible new kinds and levels of communications services simply not possible with smaller satellites. This paper briefly describes three such new designs, concerning electronic mail transmission, educational TV distribution, and mass personal communications; it compares the users' service costs with those of terrestrial networks designed for the same performance.     

Space solar power vs space communications

To meet the future needs of energy on Earth, the transmission of solar power from space is being extensively studied. Since the power station will occupy a position in the geostationary orbit and will use radio frequency spectrum for transmission of energy to Earth, the relative benefits of space solar power and space communications should be considered. The resource allocation of orbit-spectrum to a power station requires a sacrifice from space communications as they both utilize similar limited resources. The power station is to energy what communication is to information. While the cost of energy is going up, the cost of information processing, storage, sharing and transmission is decreasing. Also, increased means of communication are used as a measure of energy conservation. With the advent of computer communication and the Large Scale Integrated (LSI) microprocessors, the technique of multiple access, message switching and satellite switching can be cost-effectively combined. The computer-satellite communication will allow information resource sharing among large numbers of users besides the conventional application of space communications. Since space communication means work effectively in many other areas where ultimate energy use and conservation is possible, the space solar power will not be able to compete or substitute on the basis of equality and social benefits. But, as the transmission technology is similar for both areas, the R & D effort for solar power will certainly increase efficiency and reduce cost for space communications.     

基于偏心率和倾角矢量的共位隔离策略

在同一个标准的位置保持窗口内并置多颗卫星,并且避免相互之间的碰撞、干扰和遮蔽,是充分利用地球静止轨道资源的一种比较好的办法。针对我国卫星共位隔离的工程需要,文章提出了一种基于偏心率矢量和倾角矢量实现共位隔离的方法,给出了基于偏心率矢量和倾角矢量联合隔离的基本方法、约束方程,以及工程实现时的位置保持策略。通过仿真计算和工程实际应用,验证了该方法的正确性。     

卫星双向时间频率传递中的Sagnac效应

 结合卫星双向时间频率传递技术,提出了在卫星运动情况下Sagnac效应解决方案。卫星双向时间频率传递技术是基于地球同步卫星进行的。地球同步卫星在各种摄动力的影响下,相对于地面上的某点不是绝对静止的,而是作小幅度日周期性运动。 Sagnac 效应与卫星和地面观测站的位置密切相关,卫星的运动直接导致了 Sagnac 效应也具有日周期变化的特征。使用高精度实测卫星轨道数据对 Sagnac 效应进行计算分析,结果表明：由卫星运动引起的Sagnac效应值具有与卫星运动一致的周日变化规律特征,大小达到几百皮秒的量级,与传统的将同步卫星作为静止点处理相比,提高了Sagnac效应误差的修正精度。该方案对于各种高精度卫星时间比对技术和卫星导航等领域具有重要的应用价值。     

基于低轨卫星增强的非差高精度导航定位技术与在轨试验验证

随着自动驾驶、精密农业等领域的发展,各领域对高精度导航定位的需求不断增加。在地基增强技术、高轨星基增强技术和传统非差精密单点定位技术的基础上,提出了一种基于低轨卫星增强的非差高精度导航定位技术,研制了基于低轨导航增强技术的低轨导航增强载荷,开发了基于低轨卫星增强的地面自适应卡尔曼滤波非差高精度定位软件,并进行了全球首次基于低轨卫星的信号信息一体化导航增强在轨试验。试验表明:经低轨卫星增强后,地面终端用户定位精度优于30 cm。最后,给出了该技术的后续研究方向,为未来低轨导航增强系统与其他增强系统协同工作,实现广泛应用奠定了基础。     

Developing a Low-Velocity Collision Model Based on the Nasa Standard Breakup Model

We have conducted a series of low-velocity impact experiments to understand the dispersion properties of fragments newly created by low-velocity impacts possible in space, especially in geostationary Earth orbit. The test results are utilized to establish a mathematical prediction model to be used in debris generation and propagation codes. Since the expected collision velocity between catalogued objects in geostationary Earth orbit shows a peak at a few hundreds meters per second, these impact experiments were conducted at a velocity range lower than 300m/s. As a typical structure of satellites in geostationary Earth orbit, thin aluminum honeycomb sandwich panels with carbon fiber reinforced plastics face sheets were prepared, while the projectile was a stainless steel ball of 9mm diameter. The data collected through these impact experiments have been re-analyzed based on the method used in the National Aeronautics and Space Administration (NASA) standard breakup model 1998 revision. The results indicate that the NASA standard breakup model derived from hypervelocity impacts could be applied to low-velocity collision possible in geostationary Earth orbit with some modifications.     

Connection between the discrete auroral structures drifting equatorward during the substorm expansion phase and the energetic particle injections at the geostationary orbit

The formation of an auroral bulge with a bright dynamical arc at its polar boundary is one of the main manifestations of the magnetospheric substorm expansion phase at the ionospheric level. At the same time, the region of discrete aurora broadens not only polewards but equatorwards as well. The discrete forms of auroras moving equatorwards form a dynamical equatorial boundary of the auroral bulge shifting together with them. The paper presents a spatial-time comparison of the drifting discrete auroras to the injection of energetic particles at the geostationary orbit. It is shown that bursts in the fluxes of energetic particles at the LANL geostationary satellites located in the same sector of MLT correspond to the majority of drifting discrete auroral structures observed by the all-sky camera. In the cases when the bursts in the fluxes are absent, the minimum latitude reached by the auroral structures at the equatorward drift is higher than the ionospheric projection of the geostationary orbit. A possible relation of the drifting discrete auroras to the plasma stream jets in the plasma sheet is discussed.     

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.     

大型空间电站在轨展开与组装动力学与控制

针对大型空间电站在轨展开与组装过程中复杂的动力学环境，将桁架类大型空间电站视为一个刚柔多体系统，采用自然坐标法对刚性构件建模，基于绝对节点坐标方法描述柔性桁架结构，编写了一套动力学仿真软件，实现了大型空间电站在轨展开与组装动力学的精确仿真。仿真结果表明，采用摆线运动插值函数作为控制方程有利于提高多级展开过程的稳定性；在结构组装过程中，减小组装速度，增大组装机构阻尼系数与劲度系数，有利于提高结构稳定性。最终集成了一套针对大型空间电站的动力学仿真平台搭建方法，为大型空间电站在轨展开与组装动力学预示提供了理论依据和方法指导。