用于地表和亚地表探测的多频极化合成孔径雷达

本文介绍了用于地表和亚地表观测的机载多频极化SAR“IMARC”。改进的SAR系统包括了4个频段（X、L、P和VHF）,相应的波长分别为4cm、23cm、68cm和254cm。这种SAR能以不同线性的极化（VV、HH、VH和HV）从飞机的左右两侧进行测量。空间分辨率在X波段为1．5～3m,L波段为4～6m,P波段为6～8m和VHF波段为8～16m。该系统采集并处理雷达数据以获得实时图像。这种SAR系统将用于测定土壤水文表面,调查植被、雪、冰层和冻土的特征,对人造目标和自然目标以及各种自然界异常现象进行定位亚地表探测。     

New results for the space radiation environment of MIR space station obtained by Liulin dosimeter-radiometer. Comparison with LET spectrometer NAUSICAA

Since 1988 high sensitivity semiconductor dosimeter-radiometer “Liulin” worked on board of MIR space station. Device measured the absorbed dose rate and the flux of penetrating particles. The analysis of the data hows the following new results:

In October 1989 and after March 24, 1991, two additional stable maximums in flux channel were observed in the southern-eastern part of South Atlantic Anomaly (SAA). These two maximums existed at least several months and seem to be due to trapped high energy electron and proton fluxes. In April 1991 additional maximums were localized in the following geographical coordinates regions: LATITUDE = (−35 °)–(−50 °) LONGITUDE = 332 ° − 16 ° and lat.(−46 °)–(−52 °) long. 360 ° − 60 °. Additional maximums diffusion occurs inside radiation belt. Appearance of these maximums seems to be closely connected with preceding powerful solar proton events and associated geomagnetic dynamics of new belt disturbances. After the series of solar proton events in June 1991 we observed significant enhancement of this new radiation belt formation. To achieve sufficient accuracy of dose rate predictions in low Earth orbits the structure and dynamics of new belt should be carefully analyzed to be included in a new environment model.

From the inter comparison of the data from “Liulin” and French developed tissue equivalent LET spectrometer NAUSICAA in the time period August–November 1992 we come to the following conclusions: Mainly there is good agreement between both data sets for absorbed dose in the region of SAA; Different situation of the instruments on the station can explain the cases when differences up to 2 times are observed; At high latitudes usually the tissue equivalent absorbed dose observations are 2 times larger than “Liulin” doses.     

UV photochemistry of DNA in vitro and in Bacillus subtilis spores at earth-ambient and low atmospheric pressure: implications for spore survival on other planets or moons in the solar system

Two major parameters influencing the survival of Bacillus subtilis spores in space and on bodies within the Solar System are UV radiation and vacuum, both of which induce inactivating damage to DNA. To date, however, spore survival and DNA photochemistry have been explored only at the extremes of Earth-normal atmospheric pressure (101.3 kPa) and at simulated space vacuum (10(-3)-10(-6) Pa). In this study, wild-type spores, mutant spores lacking alpha/beta-type small, acid-soluble spore proteins (SASP), naked DNA, and complexes between SASP SspC and DNA were exposed simultaneously to UV (254 nm) at intermediate pressure (1-2 Pa), and the UV photoproducts cis,syn-thymine-thymine cyclobutane dimer (c,sTT), trans,syn-thymine-thymine cyclobutane dimer (t,sTT), and "spore photoproduct" (SP) were quantified. At 101.3 kPa, UV-treated wild-type spores accumulated only SP, but spores treated with UV radiation at 1-2 Pa exhibited a spectrum of DNA damage similar to that of spores treated at 10(-6) Pa, with accumulation of SP, c,sTT, and t,sTT. The presence or absence of alpha/beta-type SASP in spores was partly responsible for the shift observed between levels of SP and c,sTT, but not t,sTT. The changes observed in spore DNA photochemistry at 1-2 Pa in vivo were not reproduced by irradiation of naked DNA or SspC:DNA complexes in vitro, suggesting that factors other than SASP are involved in spore DNA photochemistry at low pressure.     

低成本航天任务保障设想

本文提出了一种新的端－端地面系统的结构,目的是减少总的航天任务任务地面支持费用。喷气推进实验室（ＪＰＬ）现用地面系统的操作、维护、部署、再生产和文件资料费用很大。在ＮＡＳＡ预算被削减这样一种气氛下,本文提出的结构由于能大幅度降低上述各项费用,从而更有现实意义。目前,地面支持功能（即接收机、跟踪、测距、遥测、遥控、监视和控制）分布在不同机柜中的几个分系统中。利用现有的多芯片模块（ＭＣＭ）封装技术,这     

X波段数据就地接收对改善用户服务及降低EO系统成本的重要性

通过一个大型地区性地面站系统很难满足大量潜在EO(对地观测)用户对廉价、及时获取数据的需求。由于大多数用户只需要当地数据(高仰角的),BURS公司设计建造了一个廉价X波段接收机系统,利用不到3米的天线可采集90°弧段范围内卫星(ERS-SAR,SPOT和JERS)发射的信号,其关键性部件是一个4贴片天线接收机系统。该系统锁定到S波段信标信号上,为闭环反馈跟踪系统产生位置误差信号。该系统采用了新颖液压驱动装置控制轻便型抛物面天线的俯仰,运动。接收到的X波段数据随后被送入一台或多台PC机。开发这种设备对未来EO系统的设计及运行操作具有深远意义。一种可能性就是多颗低价格/低功率小卫星配合当地自筹资金服务网建立的众多地面接收机构成EO系统。     

下一代数字式GPS接收机

讨论由 collins 公司制造的下一代(NGR)数字化 GPS 接收机的结构和技术特点。该计划的目的是开发一种具有较高抗干扰能力的高级 GPS 接收机单片设备(chipset)。计划始于1985年,为不载人和载人飞行器提供小型化接收机技术。目前用于战术导弹的两通道接收机的研制工作已全面开展,用来替换标准高动态接收机 RCVR-3A 型的五通道接收机正在测试和评估中。NGR 设计是从国防高级研究计划机构(DARPA)开发手提式 GPS 接收机使用的数字信号处理体系结构入手的,改进后可提高抗干扰和信号捕获性能。使用可生产、合格及便宜的硅单片微波集成电路(MMIC)和半商品化的数字技术开发 GPS 核心单片设备。另外,所采用的系统设计方法允许重复使用成熟的和确认过的 GPS 软件。     

低成本卫星地面控制设施的设计

该设计方法的核心是:卫星操作中的公共部分,即遥控、跟踪、子系统分析(包括遥测处理)、系统规划和调度、轨道确定和保持、数据传送和控制。特殊卫星任务的应用和操作另行考虑,以保证本设计方法可应用于许多种卫星系统。关于特殊卫星任务的讨论将限制在了解支持航天任务的地面控制设施总规模和业务范围。分离出“通用”卫星操作功能,可研究出一种低成本通用设计方法,该方法允许对系统作阶段性改进,而对在轨设施和测控性能影响极小。该方法的目标是提高卫星系统的可扩展性、可维护性和可操作性。     

OPTICAL TELEPHONE CORD PASSING THROUGH LONG PIPE WITH SPIRAL FLOW

A new effective technique, useful in telecommunications industry for passing an optical telephone cord attached to a connector through pipeline,has been developed using the spiral flow. Using this technique, the cord could be passed through a straight pipeline 150 meters long and a roll of vinyl tube 50 meters long. However, under the same condition, the cord could not pass through when using the turbulent flow. To obtain a high speed stable spiral flow, a nozzle with an annular slit connected to a conical cylinder was used. A pressurized fluid with no tangential flow was supplied through this slit and the fluid, passing through the conical cylinder, was deformed into spiral flow with the steeper axial velocity distribution compared to that of turbulence pipe flow due to Coanda effect and instability. As a result, the cord was attracted to the axis area of the pipe, which effectively increased the ability for the work of cord passing. This high ability for cord passing is attributed mainly to the reduct