A model for calculating global illuminance from satellite data

A model for calculating global illuminance on horizontal surfaces from meteorological satellite data was developed. The data used for developing the model are global illuminance measured at four solar monitoring stations situated in different parts of Thailand and 8-bit digital data from visible channel of GMS-5 satellite covering the whole country for the period of 1–2 years. Values of normalized global illuminance defined as a ratio of global illuminance to clear sky global illuminance were calculated. These values were used to correlate with those of cloud index derived from the satellite data. From the correlation, a model relating the normalized global illuminance to cloud index was established. The performance of this model was investigated using an independent illuminance data set. It was found that the global illuminance calculated from the model agreed well with that obtained from the measurement, with a root mean square difference of 5.38 klux or 7.0% of the mean values.     

用于整星隔振效果评价的隔振器影响系数指标研究

对整星隔振系统的隔振效果评价指标（振动传递率、隔振器振级落差、功率流等）进行分析,通过实例证明采用隔振器底端到顶端的传递率来评价隔振效果是不充分的,而采用隔振器振级落差、功率流等指标也在实际应用中存在各自的局限性。在分析隔振器影响系数的基础上,提出一种改进的隔振器影响系数指标,并采用位移导纳表达改进的隔振器影响系数。以自行设计的新型整星隔振平台为例,采用改进的隔振器影响系数指标进行隔振效果预测,结果表明：改进的隔振器影响系数指标可以更加简单直观地表现出整星隔振平台的隔振性能。     

A User Range Accuracy Estimation Method of the Global Navigation Satellite System

An Analytic estimation method （AEM） which has less execution time is proposed to calculate the User range accuracy （URA） used by the user to detect the integrity potential risk. It shows that the most important thing of computing URA is to find the maximum error vector in the error vector space. By using the covariance matrix of the error vector, the searching of the maximum error vector is converted to an analytic geometry problem. The value of the maximum error vector can be obtained di- rectly by mathematical derivation. Experiments are made to compare the performance between the proposed AEM algorithm and the Exhaustive grid search （EGS） method. The related results show that the AEM algorithm can re- duce more than 92% of execution time. This algorithm is more suitable for computing URA at the Master control station （MCS） for the engineering applications.     

美国星基增强系统发展现状和未来

本文介绍了星基增强系统产生的背景以及美国的星基增强系统WAAS（广域增强系统）的系统架构,回顾了WAAS（广域增强系统）的发展历史,分析了WAAS（广域增强系统）的发展现状和未来的发展方向。     

A use of case-based reasoning technique in building expert systems

Matra Marconi Space France and Aramiihs (Action de Recherche et Application Matra Irit en Interaction Homme Système) laboratory have used and evaluated Case Based Reasoning (CBR) techniques in two projects:

• - The first project is about the development of a system dedicated to help satellites AIT/AIV (Assembly Integration and Test/Validation) test engineers to cope with incidents occurring during test activities. The project is funded by the EGSE System Section of ESTEC (European Space Research and Technology Centre.).

• - The second project is related to the building of a knowledge-based system for diagnosis assistance in AIT/AIV activities of Ariane4 Vehicle Equipment Bay (VEB). The project is financed by internal funding of MMS-F.

In the two projects, CBR technique is neither used the same way nor with the same purpose.

In the first project, CBR technique is used to find out or suggest the cause of an anomaly when an incident appears. Confronted with the occurrence of an incident, the system will refer to its characteristics (test context, symptoms…) that are considered as relevant to retrieve previous similar incidents.

In the second project, CBR technique is combined with Rule Based Reasoning and Model Based Reasoning ones to form the reasoning core of a Hybrid Knowledge Based System. When an incident occurs, the system proposes to test engineers a diagnosis approach based on the combination of different knowledge (coded into rule, cases and models).

Aramiihs is a research unit where engineers from MMS and researchers from the IRIT (Institut de Recherche en Informatique de Toulouse) CNRS (Centre National de la Recherche Scientifique) collaborate on problems concerning new types of man-system interaction.     

卫星测控站射频接收系统EMC设计与测试

本文以卫星测控站为例,介绍了卫星测控站和卫星通信地面站接收系统EMC的设计与测试方法,并给出了测试结果。     

Generalized satellite link model and its application to the transmission plan

A generalized model for the satellite link that includes non-linear effects is presented. The transponder is handled as a black box with nominal gain g_s. At a specific operating point each signal in the transponder has its own gain, g_sci, that may be different from g_s. The parameter g_sci depends on the operating point of the transponder, the power of the signal and the distribution of the residual transponder power among the other carriers. The intermodulation between the carriers and between them and the up-link noise is included in the model as well. The generalized model is represented by the conventional traditional equation, modified with correction factors which account for the nonlinear effects. Application of the model to typical transmission plans is given and comparison of the results to field experiments and transponder analysis program is included. Emphasis is placed on the use of the transponder with mixed TV and SCPC operation.     

基于跳频技术的卫星通信干扰分析与比较

简要分析了跳频通信的基本特点和优点，通过计算和比较卫星通信常见的几种干扰方式（宽带噪声干扰、窄带噪声干扰和脉冲干扰）的处理增益和误码率，得出了脉冲干扰对跳频技术下的卫星通信具有较好的干扰效果这一结论，并给出了与理论分析相一致的仿真结果。     

Asymptotic stabilization of the position of a rigid body with fixed point without velocity measurements

The problem of stabilization of a rigid body with a fixed point in reference to its velocity and position is considered. It is assumed that the rigid body is controlled by three external torques. The proposed controlling torques need neither the measurements of the velocity nor the information about the inertial parameters. Such a control may be realized by the on-line solution of the auxiliary differential equations.The stability of the closed loop nonlinear system is established by means of the Lyapunov function and Barbashin's theorem. The proposed control may be applied to stabilize the satellites controlled by the reactive jets.     

卫星通信系统对抗途径分析

本文在叙述了卫星通信系统组成的基础上，分析了卫星通信对抗系统的内容、应具有的功能和实现对抗的主要途径与方法，最后探讨了实现对抗所要解决的关键技术。