Quality Assessment of the IDS Contribution to ITRF2008

Doppler Orbitography Radiopositionning Integrated by Satellite (DORIS) is one of the four fundamental techniques contributing to the ITRF. The optimal coverage over the globe of the DORIS observing sites and sites co-located with GPS, allow a strong embedding of DORIS within the ITRF network. DORIS contributes to the access to ITRF through precise orbit determination of altimetric satellites with onboard DORIS receivers. The DORIS contribution to the ITRF2008 is enhanced by the fact that the solutions of seven analysis centers were included in the submitted combined time series of weekly station positions and daily polar motion. We evaluate the quality of the DORIS combined solution in terms of its agreement with the other techniques (VLBI, SLR, GPS) contributing to the ITRF2008 combination. We show in particular that the precisions of the current IDS products range between 1.5 to 2.6 mm for station positions (at the epochs of minimum variances); better than 1 mm/yr in velocities and between 170 and 260 micro-arc-seconds for polar motion, a significant improvement by a factor of three to five, compared to past data used in the ITRF2005 combination. This improvement is certainly due to improved analysis strategies employed by the seven IDS analysis centers that contributed to the combined weekly submitted solutions of station positions and polar motion. A spectral analysis of DORIS station height time series indicates that annual and semi-annual signals are dominant. However, TOPEX draconitic period of about 118 days is still detected in about 20% of the station position power spectra. DORIS height annual signals correlate well with GPS annual signal estimated at some co-located stations, which show that DORIS technique is able to detect loading signals.     

A320系列飞机大气数据系统的维护

大气数据系统是飞机重要的机载系统。本文结合系统原理、工程技术资料和自身维护经验,对A320系列飞机大气数据系统日常维护中的一些常见故障和特殊故障进行分析,给出维护建议,并对系统维护中的注意事项进行提示与强调。     

用于小型无人机的超声波低空测高系统实验研究

根据声波在空气中传播反射的原理,设计了一种基于超声波模块600和单片机C8051F121组成的小型无人机测高系统。主要针对当无人机起飞、降落时,提高高度测量的精度,详细介绍了超声波模块600的工作原理、软件设计及对实验数据的分析并得出结论。     

Wave disturbance influence on HF-propagation characteristics

This work studies the variations of HF characteristics and ionospheric parameters recorded over mid-latitude paths in the Russian East-Siberian region during magnetic storms on May 15, 1997, and September 24, 2006. The sharp wave-like changes in maximum observed frequencies (MOF) were recorded during the main phase of the investigated storms. Assuming that observed MOF variations can be produced by ionospheric disturbances propagating from the northern to the southern latitudes, a simulation of HF propagation conditions was carried out.     

A mars communication constellation for human exploration and network science

This paper analyses the possibility of exploiting a small spacecrafts constellation around Mars to ensure a complete and continuous coverage of the planet, for the purpose of supporting future human and robotic operations and taking advantage of optical transmission techniques. The study foresees such a communications mission to be implemented at least after 2020 and a high data-rate requirement is imposed for the return of huge scientific data from massive robotic exploration or to allow video transmissions from a possible human outpost.     

适用于DSP并行处理的高效PRI变换算法

PRI变换可以有效地用于以TOA参数为标准的PDW分选算法,然而该变换比较复杂,需要消耗大量时间,因此其应用受到限制.通过改变传统PRI变换的运算过程,提出了新的PRI变换算法,可以在很大程度上提高运算速度,而且适用于DSP并行处理,并且不影响其运算精度.通过理论分析和工程实践,验证了这种算法的高效性.     

Link11干扰试验效果评估技术研究

数据链已在近年来的历次战争中大显身手，取得很好的实战效果，因之数据链对抗成为通信对抗的重要研究方向。本文首先对干扰效果评估现状和Link11干扰方法进行了简单介绍，最后根据Link11的特点，提出了多层次、多方面的Link11干扰试验效果评估指标体系及干扰效果综合评估数据处理算法，为Link11数据链干扰设备的靶场试验提供技术参考。     

数字式外部电源监控器的设计与实现

传统的外部电源监控器采用模拟电路和继电器实现,控制的精度和灵活性差。数字式外部电源监控器以高性能的DSP芯片TMS320F240为核心,采用通用的嵌入式硬件软件设计方法,构建了一个高性能的控制系统平台,具有维护方便,控制精度高和系统灵活等优势。根据该原理研制的产品经过试验、联试和用户使用,结果表明该控制器工作可靠、性能良好。     

多线程机制应用于测控实时系统的关键技术研究

和传统的进程机制相比,多线程机制具有节省系统的存储资源,减少系统的控制、调度、通信和同步开销,以及内核并发的特征,这些特征能够提高实时系统的实时性能。本文以测控实时系统的开发为例,说明多线程机制应用于实时系统中的优势以及开发中需要解决的关键问题。     

基于智能Agent的卫星计划系统协作中间件研究

Agent技术是分布式系统领域未来发展的重要方向之一,计划协同系统是航天项目在现有基础条件下提高运作效率的关键所在。本文通过研究国内外的计划系统,提出了基于智能Agent技术的计划协同架构中间件CPSOM方案,并且给出一种实现途径。