美国空军东靶场的改造计划

美国空军东靶场的发射支持服务包括军方、NASA和商业性的航天飞机、大力神、德尔它、阿特拉斯—人马座、潜艇发射的三叉戟和其它小型运载工具的发射,是世界上业务种类最多也是最忙的一个靶场。其主要设备包括计算机、跟踪雷达、摄象机、遥测系统、安控设备和其它设备。该靶场还在大西洋和印度洋区设有远方跟踪站,保障入轨段。     

采用GPS对铷原子频标进行校频

在精密定时中普遍采用铷原子频标，虽然铷原子频标的频率稳定度要远优于晶体振荡器，但仍属于二级频率标准，需要用一级频标对其定时校准，比较麻烦。若能采用新的技术对其进行在线自动校准，不仅可以降低运营成本，也可以提高设备的利用率。本文介绍了一种简便的采用GPS对铷原子频标自动校准的方法，供大家参考。     

Life and light: exotic photosynthesis in binary and multiple-star systems

The potential for Earth-like planets within binary/multiple-star systems to host photosynthetic life was evaluated by modeling the levels of photosynthetically active radiation (PAR) such planets receive. Combinations of M and G stars in (i) close-binary systems; (ii) wide-binary systems, and (iii) three-star systems were investigated, and a range of stable radiation environments were found to be possible. These environmental conditions allow for the possibility of familiar, but also more exotic, forms of photosynthetic life, such as IR photosynthesizers and organisms that are specialized for specific spectral niches.     

美国“扩展空间传感器体系结构”研发及应用分析

正用于空间监视的传感器水平十分重要,因其决定着所获取空间态势感知数据的多少。空间态势感知数据的传输与共享技术在空间作战中也同样扮演着重要角色,受限时也会导致数据无法充分利用。由于空间资产在国家安全中的重要性日益提升,美国对空间态势感知越来越重视。为了保护美国的空间资产免于自然灾害和人为     

小卫星及其测控

本文扼要介绍了目前世界各国小卫星的发展现状,分析了小卫星的特点、发展机遇及潜在应用。接着介绍了小卫星的发射,并对小卫星作了评价。最后,较深入地分析了小卫星测控特点,及其对通用航天测控网的影响。     

Exposure of Arabidopsis thaliana to hypobaric environments: implications for low-pressure bioregenerative life support systems for human exploration missions and terraforming on Mars

Understanding how hypobaria can affect net photosynthetic (P (net)) and net evapotranspiration rates of plants is important for the Mars Exploration Program because low-pressured environments may be used to reduce the equivalent system mass of near-term plant biology experiments on landers or future bioregenerative advanced life support systems. Furthermore, introductions of plants to the surface of a partially terraformed Mars will be constrained by the limits of sustainable growth and reproduction of plants to hypobaric conditions. To explore the effects of hypobaria on plant physiology, a low-pressure growth chamber (LPGC) was constructed that maintained hypobaric environments capable of supporting short-term plant physiological studies. Experiments were conducted on Arabidopsis thaliana maintained in the LPGC with total atmospheric pressures set at 101 (Earth sea-level control), 75, 50, 25 or 10 kPa. Plants were grown in a separate incubator at 101 kPa for 6 weeks, transferred to the LPGC, and acclimated to low-pressure atmospheres for either 1 or 16 h. After 1 or 16 h of acclimation, CO(2) levels were allowed to drawdown from 0.1 kPa to CO(2) compensation points to assess P (net) rates under different hypobaric conditions. Results showed that P (net) increased as the pressures decreased from 101 to 10 kPa when CO(2) partial pressure (pp) values were below 0.04 kPa (i.e., when ppCO2 was considered limiting). In contrast, when ppCO(2) was in the nonlimiting range from 0.10 to 0.07 kPa, the P (net) rates were insensitive to decreasing pressures. Thus, if CO(2 )concentrations can be kept elevated in hypobaric plant growth modules or on the surface of a partially terraformed Mars, P (net) rates may be relatively unaffected by hypobaria. Results support the conclusions that (i) hypobaric plant growth modules might be operated around 10 kPa without undue inhibition of photosynthesis and (ii) terraforming efforts on Mars might require a surface pressure of at least 10 kPa (100 mb) for normal growth of deployed plant species.     

国际海事卫星组织将成立附属公司筹建中高度卫星系统

国际海事卫星组织(INMARSAT)将在94年底或95年初成立一个附属公司来负责投资高达24亿美元的INMARSAT—P计划,以在蓬勃发展的移动通信市场上和摩托罗拉公司的“铱”全球个人通信系统等展开竞争。该系统将提供全球性的话音、传真和数据传输服务,空间段由12至15颗中高度轨道卫星组成,轨道倾角为55°,和目前的全球定位系统卫星很相似。所用的手持电话机不大于目前的蜂窝移动电话机。     

空间用GPS测位测姿设备

劳拉航天系统公司和天宝导航公司将开发一种适于空间应用的全球定位系统姿态确定设备,该设备可取代目前用于姿态控制的一整套笨重传感器。这种称为GPS Tensor的新型低功率全固态设备有望减小卫星尺寸和重量并降低测姿设备的成本。 通常,卫星是利用一个太阳和地球敏感器及陀螺仪的组件来测定姿态的,而GPS Tensor