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441.
442.
一种极化敏感反射器用的展开机构 总被引:1,自引:0,他引:1
极化敏感反射器用的展开机构由一对相同的展开铰链及一个调速器组成,每个铰链都有提供动力的扭转弹簧及闭锁装置;调速器通过一个绳轮和展开轴连接。调速器中以164倍于展开轴转速旋转的离心盘提出阻尼力矩,以稳定展开速度,防止冲击过大,并保证较高的展开重精度。机构通过了包括振动,真空热循环等鉴定试验。在真空中高温52.3℃下的展开速度比-20℃下高14%,常温常压下在模拟零重力试验设备上测得的展开重复精度优于 相似文献
443.
Anik Kern Judit Bartholy va E. Borbs Zoltn Barcza Rita Pongrcz Csaba Ferencz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(11):1933-1945
Information about the amount and spatial structure of atmospheric water vapor is essential in understanding meteorology and the Earth environment. Space-borne remote sensing offers a relatively inexpensive method to estimate atmospheric water vapor in the form of integrated water vapor (IWV). The research activity reported in the present paper is based on the data acquired by the HRPT/MODIS (High Resolution Picture Transmission, MODerate resolution Imaging Spectroradiometer) receiving station established in Budapest (Hungary) by the Space Research Group of the Eötvös Loránd University. Integrated water vapor is estimated by the remotely sensed data of the MODIS instrument with different methods and also by the operational numerical weather prediction model of the European Centre for Medium-Range Weather Forecasts (ECMWF). Radiosonde data are used to evaluate the accuracy of the different IWV fields though it has been pointed out that the in situ data also suffers from uncertainties. It was found that both the MODIS and the ECMWF based fields are of good accuracy. The satellite data represent finer scale spatial structures while the ECMWF data have a relatively poor spatial resolution. The high quality IWV fields have proved to be useful for radiative transfer studies such as the atmospheric correction of other satellite data from times different than the overpass times of satellites Terra/Aqua and the forecast times of the model data. For this purpose the temporal variability of IWV is scrutinized both using ECMWF and MODIS data. Taking advantage of Terra and Aqua overpasses, the mean rate of change of IWV estimated by the near infrared method was found to be 0.47 ± 0.45 kg m−2 h−1, while it was 0.13 ± 0.65 kg m−2 h−1 based on the infrared method. The numerical weather prediction model’s analysis data estimated −0.01 ± 0.13 kg m−2 h−1 for the mean growth rate, while using forecast data it was 0.24 ± 0.18 kg m−2 h−1. MODIS data should be used when available for the estimation of the IWV in other studies. If no satellite data are available, or available data are only from one overpass, ECMWF based IWV can be used. In this case the analysis fields (or the satellite field) should be used for temporal extrapolation but the rate of change should be calculated from the forecast data due to its higher temporal resolution. 相似文献
444.
基于数字微波通信系统的特点,介绍了多载波SD-CDMA(Multicarrier-DS-CDMA,即MC-DS-CDMA)调制技术的基本原理及其应用于数字微波通信系统中的具体实现方法。从理论上详细地分析了MC-CDMA工作方式的性能,并将其与传统的数字微波通信系统进行了比较,阐明了将MC-DS-CDMA工作方式应用于数字微波通信系统的必要性。 相似文献
445.
混沌测控的概念、特性与实现 总被引:1,自引:0,他引:1
概述了混沌测控的基本概念,归纳了混沌序列的主要特性并与m、Gold序列进行了比较,介绍了混沌序列的种类和截断码的码库生成,提出了截断混沌序列和无限混沌序列的测控通信系统方案设想。 相似文献
446.
447.
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. 相似文献
448.
为了有效地利用空间站资源,提出了遥科学的概念。利用空间站的微重力环境所做的各种科学实验,需要空地间交互地进行通信,空间数据系统咨询委员会(CCSDS)为这种通信键路制定了一系列标准。着重讨论了遥科学对通信链路的要求,适于遥科学实验的空间数据系统模型以及天基、地基通信系统框图。 相似文献
449.
包妙琴 《中国空间科学技术》1992,12(2):27-34
以国外自旋稳定通信卫星发展的技术途径为背景,比较了在“东方红二号甲”卫星技术的基础上进一步发展中国自旋稳定通信卫星的不同技术方案;说明方案的选择主要取决于对今后继续发展自旋稳定通信卫星的战略考虑。 相似文献
450.
陈志远 《中国空间科学技术》1990,10(4):36-43
叙述了为国内电信服务的机械消旋卫星天线系统.该天线系统包括三部分:全向遥测遥控天线组件,定向通信天线和三信道无接触旋转关节.遥测遥控天线为双圆盘天线,辐射全向性方向图,圆极化.通信天线是收发共用单喇叭馈源偏置椭圆抛物面天线,辐射一个5°×8°的椭圆波束,恰好覆盖中国本土.三信道无接触旋转关节是一个同心三同轴线结构,形成三路传输信道.各同轴线旋转连接处有扼流槽.各信道的插入损耗为0.6~0.8dB,信道之间隔离优于50dB. 相似文献