利用GPS射频多普勒确定低轨地球卫星的轨道

本文研究了使用这样一种GPS测量值——双差分GPS射频多普勒确定低轨地球卫星的轨道。该测量值很容易获得,而且不受时钟误差的影响,还可对用户卫星连续定轨。分析表明:使用18颗GPS卫星的星座和13个地面站,在两小时跟踪后,可使1300km高度用户星(TOPEX)的定轨精度达5cm。考察了使用少于13个地面站的影响,不同求解方法的影响以及引入虚假推力参数以减小重力模型误差(主要误差源之一)的影响。     

ICAO已不再要求必须安装MLS

国际民航组织(ICAO)已取消在所有国际机场都必须在1998年1月1日以前安装微波着陆系统(MLS),来代替目前的仪表着陆系统(ILS)的要求.这一灵活的新政策是认识到将在2000年转向采用全球导航卫星系统(GNSS),如美国的GPS系统和俄罗斯的Glonass系统进行1类着陆而制定的,在蒙特利尔召开的ICAO的“专门的通信/营运部会议”上受到广泛赞同.这次通信/营运会议推荐的     

帧转移电荷耦合装置用于高速成象

固态成象装置正在越来越多地取代许多领域中的传统摄影技术。本文介绍一种高速摄象机,它利用帧转移CCD成象器的两个特点,也就是同时完成积累过程以及随后的电荷分布向存贮器的转移。本文给出该系统的详细说明及其在研究液流分解工作中的应用。     

Spacelab concept and its utilization for science

The first part of the paper is devoted to the presentation of the Spacelab concepts, for which detailed design studies are at present being carried out by ESRO. The second part concentrates on the utilization of the Spacelab for the various fields of science, namely: (1) Atmospheric and space plasma physics, (2) Astronomy and astrophysics, (3) Material science and (4) Life sciences. The advantages of using the Spacelab for observations in these fields as compared to conventional automated satellites are highlighted.     

强迫振荡理论

本文给出了基于基本守恒方程的一维轴向稳定分析。分析方法与经典方法不同,区别在于利用一些显式关系项来说明在固体推进剂火箭发动机中声学系统与各种结构、燃烧和呈现的流动现象之间的相互作用。此外,本文处理控制方程的方式也与经典的方法不同,即得到声学系统正态模型的稳定性余量和固有频率的方法与经典方法不一样。本文给出了用这种分析方法研究相互作用的一个例子。这就是试验台轴向振动与声学系统压力振荡之间的相互作用。结果表明,如果振荡频率和振幅需要精确地确定的话,各单个系统即声学和试验台结构不能再单独地考虑。     

Planetary quarantine in the solar system. Survival rates of some terrestrial organisms under simulated space conditions by proton irradiation

We have been studying the survival rates of some species of terrestrial unicellular and multicellular organism (viruses, bacteria, yeasts, fungi, algae, etc.) under simulated interstellar conditions, in connection with planetary quarantine. The interstellar environment in the solar system has been simulated by low temperature, high vacuum (77 K, 4 x 10(-8) torr), and proton irradiation from a Van de Graaff generator. After exposure to a barrage of protons corresponding to about 250 years of irradiation in solar space, tobacco mosaic virus, Bacillus subtilis spores, Staphylococcus aureus, Micrococcus flavus, Aspergillus niger spores, and Clostridium mangenoti spores showed survival rates of 82, 45, 74, 13, 28, and 25%, respectively.     

Ground-based simulations of cosmic ray heavy ion interactions in spacecraft and planetary habitat shielding materials

This paper surveys some recent accelerator-based measurements of the nuclear fragmentation of high energy nuclei in shielding and tissue-equivalent materials. These data are needed to make accurate predictions of the radiation field produced at depth in spacecraft and planetary habitat shielding materials and in the human body by heavy charged particles in the galactic cosmic radiation. Projectile-target combinations include 1 GeV/nucleon 56Fe incident on aluminum and graphite and 600 MeV/nucleon 56Fe and 290 MeV/nucleon 12C on polyethylene. We present examples of the dependence of fragmentation on material type and thickness, of a comparison between data and a fragmentation model, and of multiple fragments produced along the beam axis.     

Analysis of the pre-flight and post-flight calibration procedures performed on the Liulin space radiation dosimeter

Liulin, a dosimetry-radiometry system, was developed to satisfy the requirements for active flux and dose rate measurements for the flight of the second Bulgarian cosmonaut in 1988. The system consists of a compact battery-operated silicon solid state detector unit and a read/write microcomputer and telemetry unit. We describe the pre-flight calibrations with charged particles, using radioactive sources and accelerated 170 MeV/nucleon proton and alpha particles at the Dubna, Russia cyclotron. We discuss comparisons with data obtained on Mir with the French-built tissue equivalent LET spectrometer NAUSICAA. Lastly, we describe post-flight calibrations performed with 1 GeV/nucleon 56Fe ions at the Brookhaven National Laboratory AGS accelerator, where the instrument was mounted in tandem with several thin position-sensitive silicon detectors behind a stopping target. The silicon detectors provided an energy spectrum for the surviving charged nuclear fragments for which the flux and absorbed dose were recorded by Liulin.