Survival of spores of the UV-resistant Bacillus subtilis strain MW01 after exposure to low-earth orbit and simulated martian conditions: data from the space experiment ADAPT on EXPOSE-E

In the space experiment "Molecular adaptation strategies of microorganisms to different space and planetary UV climate conditions" (ADAPT), bacterial endospores of the highly UV-resistant Bacillus subtilis strain MW01 were exposed to low-Earth orbit (LEO) and simulated martian surface conditions for 559 days on board the European Space Agency's exposure facility EXPOSE-E, mounted outside the International Space Station. The survival of B. subtilis MW01 spores from both assays (LEO and simulated martian conditions) was determined by a colony-formation assay after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110?nm) as well as the martian UV spectrum (λ≥200?nm) was the most deleterious factor applied; in some samples only a few spore survivors were recovered from B. subtilis MW01 spores exposed in monolayers. However, if shielded from solar irradiation, about 8% of MW01 spores survived in LEO conditions, and 100% survived in simulated martian conditions, compared to the laboratory controls. The results demonstrate the effect of shielding against the high inactivation potential of extraterrestrial solar UV radiation, which limits the chances of survival of even the highly UV-resistant strain of B. subtilis MW01 in the harsh environments of outer space and the martian surface.     

Olivine-respiring bacteria isolated from the rock-ice interface in a lava-tube cave, a Mars analog environment

The boundary between ice and basalt on Earth is an analogue for some near-surface environments of Mars. We investigated neutrophilic iron-oxidizing microorganisms from the basalt-ice interface in a lava tube from the Oregon Cascades with perennial ice. One of the isolates (Pseudomonas sp. HerB) can use ferrous iron Fe(II) from the igneous mineral olivine as an electron donor and O(2) as an electron acceptor. The optimum growth temperature is ～12-14°C, but growth also occurs at 5°C. Bicarbonate is a facultative source of carbon. Growth of Pseudomonas sp. HerB as a chemolithotrophic iron oxidizer with olivine as the source of energy is favored in low O(2) conditions (e.g., 1.6% O(2)). Most likely, microbial oxidation of olivine near pH 7 requires low O(2) to offset the abiotic oxidation of iron. The metabolic capabilities of this bacterium would allow it to live in near-surface, icy, volcanic environments of Mars in the present or recent geological past and make this type of physiology a prime candidate in the search for life on Mars.     

EXPOSE-E: an ESA astrobiology mission 1.5 years in space

The multi-user facility EXPOSE-E was designed by the European Space Agency to enable astrobiology research in space (low-Earth orbit). On 7 February 2008, EXPOSE-E was carried to the International Space Station (ISS) on the European Technology Exposure Facility (EuTEF) platform in the cargo bay of Space Shuttle STS-122 Atlantis. The facility was installed at the starboard cone of the Columbus module by extravehicular activity, where it remained in space for 1.5 years. EXPOSE-E was returned to Earth with STS-128 Discovery on 12 September 2009 for subsequent sample analysis. EXPOSE-E provided accommodation in three exposure trays for a variety of astrobiological test samples that were exposed to selected space conditions: either to space vacuum, solar electromagnetic radiation at >110?nm and cosmic radiation (trays 1 and 3) or to simulated martian surface conditions (tray 2). Data on UV radiation, cosmic radiation, and temperature were measured every 10?s and downlinked by telemetry. A parallel mission ground reference (MGR) experiment was performed on ground with a parallel set of hardware and samples under simulated space conditions. EXPOSE-E performed a successful 1.5-year mission in space.     

R3DE: Radiation Risk Radiometer-Dosimeter on the International Space Station--optical radiation data recorded during 18 months of EXPOSE-E exposure to open space

Radiation Risk Radiometer-Dosimeter E (R3DE) served as a device for measuring ionizing and non-ionizing radiation as well as cosmic radiation reaching biological samples located on the EXPOSE platform EXPOSE-E. The duration of the mission was almost 1.5 years (2008-2009). With four channels, R3DE detected the wavelength ranges of photosynthetically active radiation (PAR, 400-700?nm), UVA (315-400?nm), UVB (280-315?nm), and UVC (<280?nm). In addition, the temperature was recorded. Cosmic ionizing radiation was assessed with a 256-channel spectrometer dosimeter (see separate report in this issue). The light and UV sensors of the device were calibrated with spectral measurement data obtained by the Solar Radiation and Climate Experiment (SORCE) satellite as standard. The data were corrected with respect to the cosine error of the diodes. Measurement frequency was 0.1?Hz. Due to errors in data transmission or temporary termination of EXPOSE power, not all data could be acquired. Radiation was not constant during the mission. At regular intervals of about 2 months, low or almost no radiation was encountered. The radiation dose during the mission was 1823.98 MJ m(-2) for PAR, 269.03 MJ m(-2) for UVA, 45.73 MJ m(-2) for UVB, or 18.28 MJ m(-2) for UVC. Registered sunshine duration during the mission was about 152 days (about 27% of mission time).The surface of EXPOSE was most likely turned away from the Sun for considerably longer. R3DE played a crucial role on EXPOSE-EuTEF (EuTEF, European Technology Exposure Facility), because evaluation of the astrobiology experiments depended on reliability of the data collected by the device. Observed effects in the samples were weighted by radiation doses measured by R3DE.     

火箭方程的“暴政”

“暴政”这个词语有时被用来形容君主的统治,也有时被人用来形容大自然的魔力。大自然的规律有些是我们无法控制的,就好比一个封建帝王一样,对于他的旨意,我们只能遵守,抗拒则死。因此,规律就代表了人类对这些无法控制的力量的理性认识。在人类试图制造出机械,让人类挣脱地球的束缚,走向太空的时候,亦是如此。如果我们想进入太阳系,我们也必须认识到这些规律,并想出办法来利用规律。     

一种简单可靠的昆虫扑翼运动图像序列自动分析方法

目前高速摄影相机和多相机系统广泛地用于记录昆虫奇妙的飞行运动,然而分析这些运动图像序列的方法却不能让人满意.提出并测试了一种简单可靠的昆虫飞行图像的自动分析方法.该方法充分地利用了图像序列中相邻两帧间的差别,可自动提取出昆虫的特征点(翼尖点,翼根点,头部端点,腹部端点)和轮廓线(翼前缘轮廓,翼后缘轮廓).采用MATLAB实现并使用虚拟昆虫和真实昆虫运动图像序列测试了该方法.测试结果表明,该方法简单可靠,无需人工干预,不针对特定昆虫,运算量也较小,且能够提供较好的识别结果,甚至在处理昆虫的身体和翅膀部分重叠或者昆虫的翅膀图像呈现明显的透明的图像序列时候结果依然不错.该方法给昆虫图像的形态学特征自动识别难题提供了一个切实可行的解决方法,节省了昆虫扑翼运动图像的分析时间.     

基于双闭环速度控制的捕获轨迹系统

中国现有高速风洞捕获轨迹（CTS）试验采用闭环形式的位置控制方式,外挂物模型处于间歇式运动模式,导致试验效率较低和可能出现“假碰撞”。鉴于此,提出了一种双闭环速度控制策略,通过建立外挂物模型的气动力/力矩误差控制环,动态产生最优速度变换尺度,在试验过程中始终以外挂物模型运动速度为控制目标,实现了CTS试验速度控制方式。地面仿真和风洞试验结果表明：双闭环速度控制策略原理正确,获得的轨迹与位置控制方式具有较好的一致性,而且克服了可能出现的“假碰撞”现象,试验时间缩短一半,数据重复性好,获得的轨迹数据信息大幅增加。证明该双闭环速度控制策略具有广阔的应用前景。     

Magnetospheric Boundary Layer Structure and Dynamics as Seen From Cluster and Double Star Measurements

In this review, we discuss the structure and dynamics of the magnetospheric Low-Latitude Boundary Layer (LLBL) based on recent results from multi-satellite missions Cluster and Double Star. This boundary layer, adjacent to the magnetopause on the magnetospheric side, usually consists of a mixture of plasma of magnetospheric and magnetosheath origins, and plays an important role in the transfer of mass and energy from the solar wind into the magnetosphere and subsequent magnetospheric dynamics. During southward Interplanetary Magnetic Field (IMF) conditions, this boundary layer is generally considered to be formed as a result of the reconnection process between the IMF and magnetospheric magnetic field lines at the dayside magnetopause, and the structure and plasma properties inside the LLBL can be understood in terms of the time history since the reconnection process. During northward IMF conditions, the LLBL is usually thicker, and has more complex structure and topology. Recent observations confirm that the LLBL observed at the dayside can be formed by single lobe reconnection, dual lobe reconnection, or by sequential dual lobe reconnection, as well as partially by localized cross-field diffusion. The LLBL magnetic topology and plasma signatures inside the different sub-layers formed by these processes are discussed in this review. The role of the Kelvin-Helmholtz instability in the formation of the LLBL at the flank magnetopause is also discussed. Overall, we conclude that the LLBL observed at the flanks can be formed by the combination of processes, (dual) lobe reconnection and plasma mixing due to non-linear Kelvin-Helmholtz waves.      

2.4犿跨声速风洞连续变迎角试验关键技术研究

在2.4m跨声速风洞开展连续变迎角试验技术研究中,遇到了3个难题:跨声速流场被持续扰动,快速精确补偿困难;试验有用信号频率与干扰信号频率产生重叠,降噪处理困难;信号间不同步对试验数据的影响增大,信号精确同步困难。采用总静压滤波优化和PID(Proportional Integral Differential)调节优化等方法提高流场快速跟随性,硬件+软件+小波等复合滤波方式进行降噪处理,并利用互相关函数实现各信号的精确同步,建立了2.4m跨声速风洞连续变迎角试验技术。使用J7等标模对该项技术进行了验证,结果表明,上述问题均得到有效解决,连续变迎角试验流场犕犪数稳定在±0.002范围内,数据的精准度达到阶梯测力试验水平。     

Exploring the Dynamic X-ray Universe:Scientific Opportunities for the Einstein Probe Mission

Time-domain astrophysics will enter a golden era towards the end of this decade with the advent of major facilities across the electromagnetic spectrum and in the multi-messenger realms of gravitational wave and neutrino. In the soft X-ray regime, the novel micro-pore lobster-eye optics provides a promising technology to realise, for the first time, focusing X-ray optics for wide-angle monitors to achieve a good combination of sensitivity and wide field of view. In this context Einstein Probe, a soft X-ray all-sky monitor mission, was proposed and selected as a candidate mission of priority in the space science programme of the Chinese Academy of Sciences. This paper reviews the most important science developments and key questions in this field towards 2020 and beyond, and how to achieve them technologically. It also introduces the Einstein Probe mission, including its key science goals and mission definition, as well as some of the key technological issues.