采用二极管检波器的双六端口网络分析仪

介绍了一种采用二极管检波器的双六端口网络分析仪的性能,这种网络分析仪在2—18GHz频带内采用商品低势垒肖特基二极管。本文描述了校准偏离平方律特性的二极管的方法。给出的测量结果,揭示了六端口网络分析仪测量单端口和二端口器件的准确度和精密度。     

史密森天文物理观测台研制的冷氢激射器及有关装置

低温冷却激射器为测量频率偏移和存储壁涂敷材料的弛豫特性创造了有利条件。这种涂敷材料是从常态变为气态物质而被冻结在存储壁上的。我们对FEP—120聚四氟乙烯在77K至48K之间的原始测试结果作了报道,并把这些测量结果和法国de Saintfuscien在372K至77K之间的测试数据进行了比较。对激射器的某些设计性能作了说明。低溫激射器的氢分离器,完全密封在真空环境中,其温度77k。本文还介绍了在真空中工作的分离器和其它一些装置。这些装置已在常温激射器中被采用并进行了测试。它们既适合于太空环境又适合于在地面使用。     

俄卫星商业化给制造部门带来希望

１９９４年５月２０日，俄罗斯地平线－４２通信卫星用质子号火箭从拜科努尔成功发射，这对受资金困扰的俄罗斯卫星制造部门起到了重要的商业推动作用，并使美国ＷＪＲｉｍｓａｔ公司确立了竞争地位，它将用这颗定位于东经１４２．５”的卫星覆盖亚太地区。地平线一４２是Ｒｉｍｓａｔ公司使用的第３颗地平线卫星，第１颗是为原苏联完成主要任务后于１９９３年８月重新定位于东经１３４“位置的老卫星，并从１９９３年９月由Ｒｉｍｓａｔ公司开始其商业运营。第２颗地平线卫星是１９９３年１１月专为Ｒｉｍｓａｔ公司发射的，定位于东经１３…     

JIRAM, the image spectrometer in the near infrared on board the Juno mission to Jupiter

The Jovian InfraRed Auroral Mapper (JIRAM) has been accepted by NASA for inclusion in the New Frontiers mission "Juno," which will launch in August 2011. JIRAM will explore the dynamics and the chemistry of Jupiter's auroral regions by high-contrast imaging and spectroscopy. It will also analyze jovian hot spots to determine their vertical structure and infer possible mechanisms for their formation. JIRAM will sound the jovian meteorological layer to map moist convection and determine water abundance and other constituents at depths that correspond to several bars pressure. JIRAM is equipped with a single telescope that accommodates both an infrared camera and a spectrometer to facilitate a large observational flexibility in obtaining simultaneous images in the L and M bands with the spectral radiance over the central zone of the images. Moreover, JIRAM will be able to perform spectral imaging of the planet in the 2.0-5.0 microm interval of wavelengths with a spectral resolution better than 10 nm. Instrument design, modes, and observation strategy will be optimized for operations onboard a spinning satellite in polar orbit around Jupiter. The JIRAM heritage comes from Italian-made, visual-infrared imaging spectrometers dedicated to planetary exploration, such as VIMS-V on Cassini, VIRTIS on Rosetta and Venus Express, and VIR-MS on the Dawn mission.     

Testing the H2O2-H2O hypothesis for life on Mars with the TEGA instrument on the Phoenix lander

In the time since the Viking life-detection experiments were conducted on Mars, many missions have enhanced our knowledge about the environmental conditions on the Red Planet. However, the martian surface chemistry and the Viking lander results remain puzzling. Nonbiological explanations that favor a strong inorganic oxidant are currently favored (e.g., Mancinelli, 1989; Plumb et al., 1989; Quinn and Zent, 1999; Klein, 1999; Yen et al., 2000), but problems remain regarding the lifetime, source, and abundance of that oxidant to account for the Viking observations (Zent and McKay, 1994). Alternatively, a hypothesis that favors the biological origin of a strong oxidizer has recently been advanced (Houtkooper and Schulze-Makuch, 2007). Here, we report on laboratory experiments that simulate the experiments to be conducted by the Thermal and Evolved Gas Analyzer (TEGA) instrument of the Phoenix lander, which is to descend on Mars in May 2008. Our experiments provide a baseline for an unbiased test for chemical versus biological responses, which can be applied at the time the Phoenix lander transmits its first results from the martian surface.     

The astrobiology primer: an outline of general knowledge--version 1, 2006

The Astrobiology Primer has been created as a reference tool for those who are interested in the interdisciplinary field of astrobiology. The field incorporates many diverse research endeavors, but it is our hope that this slim volume will present the reader with all he or she needs to know to become involved and to understand, at least at a fundamental level, the state of the art. Each section includes a brief overview of a topic and a short list of readable and important literature for those interested in deeper knowledge. Because of the great diversity of material, each section was written by a different author with a different expertise. Contributors, authors, and editors are listed at the beginning, along with a list of those chapters and sections for which they were responsible. We are deeply indebted to the NASA Astrobiology Institute (NAI), in particular to Estelle Dodson, David Morrison, Ed Goolish, Krisstina Wilmoth, and Rose Grymes for their continued enthusiasm and support. The Primer came about in large part because of NAI support for graduate student research, collaboration, and inclusion as well as direct funding. We have entitled the Primer version 1 in hope that it will be only the first in a series, whose future volumes will be produced every 3-5 years. This way we can insure that the Primer keeps up with the current state of research. We hope that it will be a great resource for anyone trying to stay abreast of an ever-changing field.     

波音董事长兼CEO詹姆士·麦克纳尼谈创新

<正> 创新对于詹姆士·麦克纳尼来说是一个非常有兴趣的话题。在接受美国《航空周刊与空间技术》(AwsT)采访的过程中,他明确地阐述了自己对创新定义的理解,解释了创新能力远比技术能力重要得多的原因。 AWST:你认为创新的最主要意义是什么? 麦克纳尼:创新的最大意义在于提高你的用户或者消费者的竞争力。衡量创新的影响力,主要是衡量创新对于客户和经济体的快速成长或者生产力的提高所产生的影响力有多大。实际上,创新越多,成本就会越低。也就是说,创新能够让企业在提高员工工资、增加再投资和提高人们的生活水平方     

美国军用小卫星崭露头角

如今,对于军事作战来说,卫星已变得像战斗机和战舰一样的重要了。但像卫星这样的天基支援不能过于昂贵,美国空军和国防部认识到,军用航天方案不必都采用费用高、能力大的卫星来完成任务,多年来倍受争议的小卫星被提上了日程。     

未来小卫星的军事应用

小卫星的军事应用是一个一直有争论的题目。支持者认为几乎所有的军事航天任务都能由小卫星来完成。而反对这种观点的是传统的美国军界，他们认为卫星应具备很高的能力和有冗余度。美国空军的科学咨询委员会提出了一种未来的可联络的智能型小卫星星座。作为航天领先的空军，开始转向“航天和空军”领域，理解混合的航天系统对于最有效地和以负担得起的方式完成航天任务是重要的。本文将探讨小卫星的技术现状并把它与军用航天有关的任