Carbonaceous cherts in the Barberton greenstone belt and their significance for the study of early life in the Archean record

The 3.5-3.2 Ga old volcano-sedimentary succession of the Barberton greenstone belt (South Africa) is characterized by lithological units that are repeated in a regular manner. Komatiitic, basaltic, and dacitic volcanic and volcaniclastic sequences are capped by zones of silica enrichment, followed by bedded carbonaceous cherts. Stratiform and crosscutting carbonaceous chert veins are common in silica alteration zones and bedded cherts. A detailed field study of several chert horizons and chert veins that range in age from 3.47 to 3.30 Ga revealed the importance of syndepositional hydrothermal activity for their origin. Bedded cherts consist of silicified detrital and tuffaceous sediments that were deposited on the seafloor. Silicification took place at the sediment-water interface as a result of diffuse upflow of low-temperature hydrothermal fluids, which gave rise to the formation of impermeable chert caps. Fluid overpressure resulted in the breaching of the cap rocks at times. Chert veins contain angular host rock fragments, replace wall rocks, and show evidence of multiple vein fillings and in situ brecciation of earlier generations of vein fillings. They represent hydraulic fractures that were initiated by overpressuring of the hydrothermal system. The vein networks were infilled, partly by hydrothermal chert precipitates, and partly by still unconsolidated (not yet silicified) sedimentary material derived from overlying sedimentary horizons. Field, petrographic, isotopic, and trace element evidence indicate that most carbonaceous matter represents sedimentary material that originated by biogenic processes in the Archean oceans and not by hydrothermal processes in the subsurface.     

Lichens survive in space: results from the 2005 LICHENS experiment

This experiment was aimed at establishing, for the first time, the survival capability of lichens exposed to space conditions. In particular, the damaging effect of various wavelengths of extraterrestrial solar UV radiation was studied. The lichens used were the bipolar species Rhizocarpon geographicum and Xanthoria elegans, which were collected above 2000 m in the mountains of central Spain and as endolithic communities inhabiting granites in the Antarctic Dry Valleys. Lichens were exposed to space in the BIOPAN-5 facility of the European Space Agency; BIOPAN-5 is located on the outer shell of the Earth-orbiting FOTON-M2 Russian satellite. The lichen samples were launched from Baikonur by a Soyuz rocket on May 31, 2005, and were returned to Earth after 16 days in space, at which time they were tested for survival. Chlorophyll fluorescence was used for the measurement of photosynthetic parameters. Scanning electron microscopy in back-scattered mode, low temperature scanning electron microscopy, and transmission electron microscopy were used to study the organization and composition of both symbionts. Confocal laser scanning microscopy, in combination with the use of specific fluorescent probes, allowed for the assessment of the physiological state of the cells. All exposed lichens, regardless of the optical filters used, showed nearly the same photosynthetic activity after the flight as measured before the flight. Likewise, the multimicroscopy approach revealed no detectable ultrastructural changes in most of the algal and fungal cells of the lichen thalli, though a greater proportion of cells in the flight samples had compromised membranes, as revealed by the LIVE/DEAD BacLight Bacterial Viability Kit. These findings indicate that most lichenized fungal and algal cells can survive in space after full exposure to massive UV and cosmic radiation, conditions proven to be lethal to bacteria and other microorganisms. The lichen upper cortex seems to provide adequate protection against solar radiation. Moreover, after extreme dehydration induced by high vacuum, the lichens proved to be able to recover, in full, their metabolic activity within 24 hours.     

高码率可编程帧同步器

印度的第一颗遥感卫星在1988年3月17日从苏联航天站发射到904km的极地太阳同步轨道。从卫星发送的数据高码速率如下:在S波段是5.2Mbps,x波段是10.4Mbps,载荷数据格式是常用的8328字格式。在数据处理系统的各研制阶段,为测试数据已研制了一种独特的可编程通用帧同步器和分路部件。它可以工作到50Mbps,处理的帧码组长度达128位,每帧长度为2e~(20)位码。此设备可在前面板设置允许误码和码位滑动。本文描述了专为IRS飞行器研制的高码率帧同步器的设计和工作过程。简介指标,系统结构同步方法,码位滑动及测试情况,表明该同步器已获得广泛应用。本设备将大大改善系统的工作性能。     

Simulation by personal workstation for man-machine interface design

This paper presents a simulation tool which has been developed for Man-Machine interface (MMI) design study, in the context of the European EVA Space Suit System development, under contract of ESA/ESTEC. The main new point is that this simulation is based on a personal workstation, and not on a heavy real-time computer, as in most simulation centres. It will be used in ESTEC to perform low cost simulations of the front part of a manned system, to improve and develop MMI with efficiency.     

利用卫星实现与飞行中巡航导弹的通信

本文讨论了与飞行中远程巡航导弹通信的需求以及卫星作为中继平台的潜力。国防卫星通信系统Ⅲ(DSCSⅢ)和舰队卫星通信(FLTSATCOM)星至少能够同时为70枚巡航导弹向水面舰只和陆基指挥中心传送200bit的状态信息。DSCSⅢ还可以同时为至少70枚巡航导弹提供准实时有人末制导支持(只要巡航导弹装有共形天线阵)。FLTSATCOM可以为2枚装有全向天线阵的巡航导弹提供相同的能力。这种能力包括传输末段敏感器图象数据,该图象数据的速率为每枚每秒40kbits,取决于可实现的图象数据压缩比。本文还论述了指挥员利用这些系统重新瞄准新目标,允许一枚巡航导弹向地面传送一路末段敏感器图象。     

跟踪与数据中继卫星系统的性能

一、引言 自60年代初,NASA就组建和操作一个为近地轨道卫星服务的跟踪和数据获取网。TDRSS是一个新测控网,为目前和直到2000年的预期卫星任务服务。该网利用了已经验证的空间和地面系统有关技术构成一个全新的测控站,只是其前端设备置于地球同步轨道上。尽量采用了自动化技术,使系统设置到数据采集以及整个跟踪期间的通信几乎都不需要人操作。     

自聚焦与超分辨率合成孔径雷达成像

构想了一种基于快速傅立叶变换（FFT）的用于合成孔径雷达（SAR）成像横向距离相位误差补偿的参量算法，称做MCCLEAN。这种算法可用做大范围场景SAR成像的一种单独的自聚焦方法。本文作者同时还给出了一种具有类似结构的算法，该算法可对大范围场景中感兴趣的小场景或小区域（ROI）同时进行自聚焦与超分辨率SAR成像，并给出了一些例子以说明这两种算法的性能。     

Training astronauts using three-dimensional visualisations of the International Space Station

Recent advances in personal computer technology have led to the development of relatively low-cost software to generate high-resolution three-dimensional images. The capability both to rotate and zoom in on these images superposed on appropriate background images enables high-quality movies to be created. These developments have been used to produce realistic simulations of the International Space Station on CD-ROM. This product is described and its potentialities demonstrated. With successive launches, the ISS is gradually built up, and visualised over a rotating Earth against the star background. It is anticipated that this product's capability will be useful when training astronauts to carry out EVAs around the ISS. Simulations inside the ISS are also very realistic. These should prove invaluable when familiarising the ISS crew with their future workplace and home. Operating procedures can be taught and perfected. "What if" scenario models can be explored and this facility should be useful when training the crew to deal with emergency situations which might arise. This CD-ROM product will also be used to make the general public more aware of, and hence enthusiastic about, the International Space Station programme.     

欧洲空间操作中心的精密轨道确定

目前,欧洲空间操作中心正在进行着一项需4年时间的开发计划,以支持未来的需要高精度轨道确定的ESA近地飞行任务。该工作是围绕着欧洲空间操作中心已开发的供轨道确定和误差分析用的一个软件系统进行的,该软件含有适合于各种轨道摄动和测量类型的先进模型。除了卫星轨道参数外,它还能对地球物理参数和测地参数进行估计和误差分析。     

天线系统的计算机辅助设计（CAD）

介绍了解决天线问题的计算机方法，讨论了这些方法的利与弊，没有一种计算机程序能解决所有的天线问题，这就需要用户用经验来判断选用哪种方法适于解决遇到的问题，虽然计算机的配置越好，就能解决复杂程度越深的问题，但是，所有电磁（CEM）计算软件在主要物理特性上却丰在一些根本限制，在易于使用和用户友好方面也还存在不足。