一种新型综合性靶场安全系统及其检验测试结果

本文首先简要介绍战略导弹发射场和航天发射场靶场安全系统的作用、特点、主要技术要求,接着介绍按美国空军航天司令部要求,由空军研究所开发的基于GPS弹道测量技术,外测、遥测、遥控综合为一体的机动型靶场安全系统——BMRST的构成及其经多种检验测试的结果。     

Detecting tree-like multicellular life on extrasolar planets

Over the next two decades, NASA and ESA are planning a series of space-based observatories to find Earth-like planets and determine whether life exists on these planets. Previous studies have assessed the likelihood of detecting life through signs of biogenic gases in the atmosphere or a red edge. Biogenic gases and the red edge could be signs of either single-celled or multicellular life. In this study, we propose a technique with which to determine whether tree-like multicellular life exists on extrasolar planets. For multicellular photosynthetic organisms on Earth, competition for light and the need to transport water and nutrients has led to a tree-like body plan characterized by hierarchical branching networks. This design results in a distinct bidirectional reflectance distribution function (BRDF) that causes differing reflectance at different sun/view geometries. BRDF arises from the changing visibility of the shadows cast by objects, and the presence of tree-like structures is clearly distinguishable from flat ground with the same reflectance spectrum. We examined whether the BRDF could detect the existence of tree-like structures on an extrasolar planet by using changes in planetary albedo as a planet orbits its star. We used a semi-empirical BRDF model to simulate vegetation reflectance at different planetary phase angles and both simulated and real cloud cover to calculate disk and rotation-averaged planetary albedo for a vegetated and non-vegetated planet with abundant liquid water. We found that even if the entire planetary albedo were rendered to a single pixel, the rate of increase of albedo as a planet approaches full illumination would be comparatively greater on a vegetated planet than on a non-vegetated planet. Depending on how accurately planetary cloud cover can be resolved and the capabilities of the coronagraph to resolve exoplanets, this technique could theoretically detect tree-like multicellular life on exoplanets in 50 stellar systems.     

Adsorption of amino acids (ALA, CYS, HIS, MET) on zeolites: fourier transform infrared and Raman spectroscopy investigations

Minerals adsorb more amino acids with charged R-groups than amino acids with uncharged R-groups. Thus, the peptides that form from the condensation of amino acids on the surface of minerals should be composed of amino acid residues that are more charged than uncharged. However, most of the amino acids (74%) in today's proteins have an uncharged R-group. One mechanism with which to solve this paradox is the use of organophilic minerals such as zeolites. Over the range of pH (pH 2.66-4.50) used in these experiments, the R-group of histidine (His) is positively charged and neutral for alanine (Ala), cysteine (Cys), and methionine (Met). In acidic hydrothermal environments, the pH could be even lower than those used in this study. For the pH range studied, the zeolites were negatively charged, and the overall charge of all amino acids was positive. The conditions used here approximate those of prebiotic Earth. The most important finding of this work is that the relative concentrations of each amino acid (X=His, Met, Cys) to alanine (X/Ala) are close to 1.00. This is an important result with regard to prebiotic chemistry because it could be a solution for the paradox stated above. Pore size did not affect the adsorption of Cys and Met on zeolites, and the Si/Al ratio did not affect the adsorption of Cys, His, and Met. ZSM-5 could be used for the purification of Cys from other amino acids (Student-Newman-Keuls test, p<0.05), and mordenite could be used for separation of amino acids from each other (Student-Newman-Keuls test, p<0.05). As shown by Fourier transform infrared (FT-IR) spectra, Ala interacts with zeolites through the [Formula: see text] group, and methionine-zeolite interactions involve the COO, [Formula: see text], and CH(3) groups. FT-IR spectra show that the interaction between the zeolites and His is weak. Cys showed higher adsorption on all zeolites; however, the hydrophobic Van der Waals interaction between zeolites and Cys is too weak to produce any structural changes in the Cys groups (amine, carboxylic, sulfhydryl, etc.); thus, the FT-IR and Raman spectra are the same as those of solid Cys.     

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。     

数字滤波器的一般原理和靶场现用滤波器的述评

本文阐述了靶场司令委员会成员靶场广泛采用的几种数字滤波器，介绍了这些滤波器的基本原理，以及用于某些数据处理的滤波器设计技术。     

现有技术在航天发射场的重用

制订了一项靶场标准化和自动化(RSA)计划,以彻底改造美国空军司令部的靶场:佛罗里达州卡纳维拉尔角空军站的东靶场和加利福尼亚州范登堡空军基地的西靶场。作为该现代化计划的一部分,现在正研究几项新技术,旨在提高性能,降低操作和维护费用。其中几项技术有望减少这些靶场发射运载火箭的费用,改变靶场外测的格局。 RSA计划准备分三个阶段进行。第一阶段于1993年由空间和导弹系统中心与哈里斯     

SCL语言：一个现成的航天器控制产品

在紧缩军事、民用和商业航天预算的时代，需要一种解决多星控制的现成方法。适用于多种航天器的标准操作接口允许地面和航天器操作采取同一种手段。许多航天工程的一个共同趋势是使航天器和地面站自主化，从而减少操作人员。接口和控制系统公司（ＩＣＳ）开发的“航天器控制语言”（ＳＣＬ）系统为航天器操作提供了一种现成的手段。ＳＣＬ系统提供了一种超描述接口，该接口对各航天工程都是标准的。它撇开航天器和地面站的硬件特性，     

一种高灵敏度全天候初始段安全监视系统——电子天空屏

本文首先分析我国航天发射场对初始段安全监视系统的迫切需求,接着介绍国外发射场所用天空屏的发展情况,电子天空屏的基本工作原理,电子天空屏的优缺点,最后给出电子天空屏实时数据处理的基本原理。     

美国TDRSS的发展及其新应用

本文将以1996年第二届TDRSS专题研讨会的内容为主,介绍美国TDRSS的现状,新研制星TDRS—H,I,J的主要技术指标改进,高精度定轨技术,TDRSS工作频段向Ka波段的过渡,几代用户转发器的发展情况,并较全面地介绍近几年来试验成功的若干TDRSS新应用,例如用于极区数据采集站高速数据中继,长期气球、无人飞行器和海上浮标的数据采集,运载火箭全程遥测数据的转发,遥感飞机高速图象数据和前向信息的传递以及正在研究的利用TDRSS对运载火箭发送靶场安全指令,为小卫星服务的按需接址业务等。     

NASA深空网（DSN）的现状及发展趋势

详细介绍了美国深空网的发展过程、目前的状况以及未来的主要发展计划。