排序方式: 共有29条查询结果,搜索用时 31 毫秒
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本文研究了利用L波段遥控专利方案实现基于GPS靶场的真正综合式靶场测量系统必须解决的问题。着重讨论硬件及从单音调制遥控系统变换成采用加密和扩频的数字系统需解决的问题。还将谈到将该系统纳入美国空军靶场标准化和自动化(RAS)结构作为一种可能的GPS靶场方案所需费用和时间安排的一些想法,并讨论如果采用该方法将带来比现用系统的优越之处。 相似文献
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最近,NASA的一项试验验证了一种实验型机载天线用于飞机和卫星问通信的能力。该试验为新一代小而轻的卫星天线提供了希望。 纽约州锡拉丘兹的马丁马塔电子实验室、西雅图的波音国防和航天组以及德克萨斯州麦金尼的德克萨斯仪器电子系统部研制了一种实验型相控阵天线。5月份,NASA刘易斯研究中心利用它们在一架小型喷气式飞机和NASA的ACTS(先进通信技术)卫星间进行了话音通信。 相似文献
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1998年11月,随着“国际空间站”(ISS)曙光号(Zarya)多功能舱的发射,休斯敦和莫斯科的“国际空间站”飞控人员和工程保障队开始联合行动,实施对“国际空间站”的飞行控制和测控通信支持。此后,“国际空间站”不断发展,参与的国家和组织逐渐增多,其飞行控制和测控通信基础设施也逐渐发展成为分属多个国家和组织、遍布世界各地的地基设施和天基设施组成的系统,支持多种接口协议和标准。本文介绍支持“国际空间站”飞行控制与测控通信的主要地基设施(7个控制中心和2个地面通信网)和天基设施(4个数据中继卫星系统),并在分析“国际空间站”飞行控制与测控通信支持能力现状的基础上,展望其未来的发展趋势。 相似文献
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M Peimbert LD Alcaraz G Bonilla-Rosso G Olmedo-Alvarez F García-Oliva L Segovia LE Eguiarte V Souza 《Astrobiology》2012,12(7):648-658
Abstract The Cuatro Ciénegas Basin (CCB) is an oasis in the desert of Mexico characterized by low phosphorus availability and by its great diversity of microbial mats. We compared the metagenomes of two aquatic microbial mats from the CCB with different nutrient limitations. We observed that the red mat was P-limited and dominated by Pseudomonas, while the green mat was N-limited and had higher species richness, with Proteobacteria and Cyanobacteria as the most abundant phyla. From their gene content, we deduced that both mats were very metabolically diverse despite their use of different strategies to cope with their respective environments. The red mat was found to be mostly heterotrophic, while the green mat was more autotrophic. The red mat had a higher number of transporters in general, including transporters of cellobiose and osmoprotectants. We suggest that generalists with plastic genomes dominate the red mat, while specialists with minimal genomes dominate the green mat. Nutrient limitation was a common scenario on the early planet; despite this, biogeochemical cycles were performed, and as a result the planet changed. The metagenomes of microbial mats from the CCB show the different strategies a community can use to cope with oligotrophy and persist. Key Words: Microbial mats-Metagenomics-Metabolism. Astrobiology 12, 648-658. 相似文献
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