The biological clock of Neurospora in a microgravity environment.

The circadian rhythm of conidiation in Neurospora crassa is thought to be an endogenously derived circadian oscillation; however, several investigators have suggested that circadian rhythms may, instead, be driven by some geophysical time cue(s). An experiment was conducted on space shuttle flight STS-9 in order to test this hypothesis; during the first 7-8 cycles in space, there were several minor alterations observed in the conidiation rhythm, including an increase in the period of the oscillation, an increase in the variability of the growth rate and a diminished rhythm amplitude, which eventually damped out in 25% of the flight tubes. On day seven of flight, the tubes were exposed to light while their growth fronts were marked. Some aspect of the marking process reinstated a robust rhythm in all the tubes which continued throughout the remainder of the flight. These results from the last 86 hours of flight demonstrated that the rhythm can persist in space. Since the aberrant rhythmicity occurred prior to the marking procedure, but not after, it was hypothesized that the damping on STS-9 may have resulted from the hypergravity pulse of launch. To test this hypothesis, we conducted investigations into the effects of altered gravitational forces on conidiation. Exposure to hypergravity (via centrifugation), simulated microgravity (via the use of a clinostat) and altered orientations (via alterations in the vector of a 1 g force) were used to examine the effects of gravity upon the circadian rhythm of conidiation.     

Development and growth of potato tubers in microgravity.

A potato explant consisting of a leaf, its axillary bud, and a small segment of stem will develop a tuber in 10-14 days when grown on earth. The tubers develop from the axillary buds and accumulate starch derived from sugars produced through photosynthesis and/or mobilized from leaf tissue. Potato explants were harvested and maintained in the Astroculture (TM) unit, a plant growth chamber designed for spaceflight. The unit provides an environment with controlled temperature, humidity, CO2 level, light intensity, and a nutrient delivery system. The hardware was loaded onto the space shuttle Columbia 24 hours prior to the launch of the STS-73 mission. Explant leaf tissue appeared turgid and green for the first 11 days of flight, but then became chlorotic and eventually necrotic by the end of the mission. The same events occurred to ground control explants with approximately the same timing. At the end of the 16-day mission, tubers were present on each explant. The size and shape of the space-grown tubers were similar to the ground-control tubers. The arrangement of cells in the tuber interior and at the exterior in the periderm was similar in both environments. Starch and protein were present in the tubers grown in space and on the ground. The range in starch grain size was similar in tubers from both environments, but the distribution of grains into size classes differed somewhat, with the space-grown tubers having more small grains than the ground control tubers. Proteinaceous crystals were found in tubers formed in each condition.     

Expression of p53-regulated genes in human cultured lymphoblastoid TSCE5 and WTK1 cell lines after spaceflight in a frozen state

The 53 kDa tumor suppressor protein p53 is generally thought to contribute to the genetic stability of cells and to protect cells from DNA damage through the activity of p53-centered signal transduction pathways. To clarify the effect of space radiation on the expression of p53-dependent regulated genes, gene expression profiles were compared between two human cultured lymphoblastoid cell lines: one line (TSCE5) has a wild-type p53 gene status, and the other line (WTK1) has a mutated p53 gene status. Frozen human lymphoblastoid cells were stored in a freezer in the International Space Station (ISS) for 133 days. Gene expression was analyzed using DNA chips after culturing the space samples for 6 h on the ground after their return from space. Ground control samples were also cultured for 6 h after being stored in a frozen state on the ground for the same time period that the frozen cells were in space. p53-Dependent gene expression was calculated from the ratio of the gene expression values in wild-type p53 cells and in mutated p53 cells. The expression of 50 p53-dependent genes was up-regulated, and the expression of 94 p53-dependent genes was down-regulated after spaceflight. These expression data identified genes which could be useful in advancing studies in basic space radiation biology. The biological meaning of these results is discussed from the aspect of gene functions in the up- and down-regulated genes after exposure to low doses of space radiation.     

Performance of a simple Closed Aquatic Ecosystem (CAES) in space.

A simple Closed Aquatic Ecosystem (CAES) consisting of single-celled green algae (Chlorella pyrenoidosa, producer), a spiral snail (Bulinus australianus, consumer) and a data acquisition and control unit was flown on the Chinese Spacecraft SHENZHOU-II in January 2001 for 7 days. In order to study the effect of microgravity on the operation of CAES, a 1 g centrifuge reference group in space, a ground 1 g reference group and a ground 1 g centrifuge reference group (1.4 g group) were run concurrently. Real-time data about algae biomass (calculated from transmission light intensity), temperature, light and centrifugation of the CAES were logged at minute intervals. It was found that algae biomass of both the microgravity group and the ground 1 g-centrifuge reference group (1.4 g) fluctuated during the experiment, but the algae biomass of the 1 g centrifuge reference group in space and the ground 1 g reference group increased during the experiment. The results may be attributable to influences of microgravity and 1.4 g gravity on the algae and snails metabolisms. Microgravity is the main factor to affect the operation of CAES in space and the contribution of microgravity to the effect was also estimated. These data may be valuable for the establishment of a complex CELSS in the future.     

Sweetpotato vine management for confined food production in a space life-support system

Sweetpotato (Ipomea batatas L.) ‘Whatley–Loretan’ was developed for space life support by researchers at Tuskegee University for its highly productive, nutritious storage roots. This promising candidate space life-support crop has a sprawling habit and aggressive growth rate in favorable environments that demands substantial growing area. Shoot pruning is not a viable option for vine control because removal of the main shoot apex drastically inhibits storage-root initiation and development, and chemical growth retardants typically are not cleared for use with food crops. As part of a large effort by the NASA Specialized Center of Research and Training in Advanced Life Support to reduce equivalent system mass (ESM) for food production in space, the dilemma of vine management for sweetpotato was addressed in effort to conserve growth area without compromising root yield. Root yields from unbranched vines trained spirally around wire frames configured either in the shapes of cones or cylinders were similar to those from vines trained horizontally along the bench, but occupying only a small fraction of the bench area. This finding indicates that sweetpotato is highly adaptable to a variety of vine-training architectures. Planting a second plant in the growth container and training the two vines in opposite directions around frames enhanced root yield and number, but had little effect on average length of each vine or bench area occupied. Once again, root yields were similar for both configurations of wire support frames. The 3–4-month crop-production cycles for sweetpotato in the greenhouse spanned all seasons of multiple years during the course of the study, and although electric lighting was used for photoperiod control and to supplement photosynthetic light during low-light seasons, there still were differences in total light available across seasons. Light variations and other environmental differences among experiments in the greenhouse had more effects on vine length than on root yield. Average vine length correlated positively with total hours of daylight received across seasons, and responses for one plant per container were higher above a threshold duration of solar exposure, suggesting that the vines of two plants per container compete for available light. In addition to the adaptability of sweetpotato to various vine-training architectures and across seasons in terms of maintaining root productivity, the open, interior volumes of the support frames tested in this study will provide future opportunity to enhance sweetpotato root yield in space by adding novel interior lighting, such as from intracanopy arrays of light-emitting diodes. This work was sponsored by NASA grant NAG 5 1286.     

Early development of fern gametophytes in microgravity.

Dormant spores of the fern Ceratopteris richardii were flown on Shuttle mission STS-93 to evaluate the effects of micro-g on their development and on their pattern of gene expression. Prior to flight the spores were sterilized and sown into one of two environments: (1) Microscope slides in a video-microscopy module; and (2) Petri dishes. All spores were then stored in darkness until use. Spore germination was initiated on orbit after exposure to light. For the spores on microscope slides, cell level changes were recorded through the clear spore coat of the spores by video microscopy. After their exposure to light, spores in petri dishes were frozen in orbit at four different time points during which on earth gravity fixes the polarity of their development. Spores were then stored frozen in Biological Research in Canister units until recovery on earth. The RNAs from these cells and from 1-g control cells were extracted and analyzed on earth after flight to assay changes in gene expression. Video microscopy results revealed that the germinated spores developed normally in microgravity, although the polarity of their development, which is guided by gravity on earth, was random in space. Differential Display-PCR analyses of RNA extracted from space-flown cells showed that there was about a 5% change in the pattern of gene expression between cells developing in micro-g compared to those developing on earth.     

深空通信中利用GEO卫星的双跳下行链路特性研究

利用现有的地球静止轨道(GEO)卫星资源,构建深空通信中深空探测器到GEO卫星、再到地面站的双跳链路系统。在自由空间链路段载波宜采用较高频率以获得链路增益;在GEO卫星到地面站链路段宜采用10GHz左右的卫星通信窗口以规避大气的相关影响。与传统一跳链路相比,双跳链路系统可以获得更大的信噪比和信道容量,以及更小的误码率。采用现有的GEO地面天线完全能够满足深空通信的要求,提高了系统的可靠性。     

Mid-latitude thermospheric zonal winds during the equinoxes

The diurnal variation of the mid-latitude upper thermosphere zonal winds during equinoxes has been studied using data recently generated from CHAMP measurements from 2002 to 2004 using an iterative algorithm. The wind data was separated into two geomagnetic activity levels, representing high geomagnetic activity level (Ap > 8) and low geomagnetic activity level (Ap ? 8). The data were further separated into two solar flux levels; with F10.7 > 140 for high and F10.7 ? 140 for low. Geomagnetic activity is a correlator just as significant as solar activity. The response of mid-latitude thermospheric zonal winds to increases in geomagnetic disturbances and solar flux is evident. With increase in geomagnetic activity, midday to midnight winds are generally less eastward and generally more westward after the about midnight transitions. The results show that east west transitions generally occurred about midnight hours for all the situations analyzed. The west to east transition occurs from 1400–1500 MLT. Enhanced westward averaged zonal wind speeds going above 150 ms⁻¹ are observed in the north hemisphere mid-latitude about sunrise hours (∼0700–1100 MLT). Nighttime winds in the north hemisphere are in good agreement with previous single station ground observations over Millstone Hill. Improved ground observations and multi satellite observations from space will greatly improve temporal coverage of the Earth’s thermosphere.     

Quantitative interpretation of heavy ions effects: models for the biological effects of heavy ions.

Heavy ions are an important part of space radiation. Although they contribute only about 1 percent in number the fraction in terms of energy deposited is much higher. Also the quality of radiation is different from the other components since the LET is generally quite high. This poses the problem of Relative Biological Effectiveness (RBE). It is considerably more important in space than on earth because shielding measures are costly and sometimes not even feasible. Radiation hazards appear to be the limiting factor In long term space flights and their evaluation constitutes a major task. There is still no general agreement about RBE of earthbound radiation, and even less concerning the biological weighting of very heavy and very energetic ions in space. Because of the lack of experimental data--particularly for risk estimates in humans-- theoretical approaches may be very helpful in this respect and provide the only means to judge the radiation protection situation in outer space. In order to be useful careful checks of their consistency are necessary. This paper summarizes some of the more common approaches in a critical manner. The unhappy conclusion at the end will be that at present it is not possible to understand even heavy ion action on survival quantitatively with an acceptable precision.     

Preliminary results of space experiment: Implications for the effects of space radiation and microgravity on survival and mutation induction in human cells

In view of the concern for the health of astronauts that may one day journey to Mars or the Moon, we investigated the effect that space radiation and microgravity might have on DNA damage and repair. We sent frozen human lymphoblastoid TK6 cells to the International Space Station where they were maintained under frozen conditions during a 134-day mission (14 November 2008 to 28 March 2009) except for an incubation period of 8 days under 1G or μG conditions in a CO₂ incubator. The incubation period started after 100 days during which the cells had been exposed to 54 mSv of space radiation. The incubated cells were then refrozen, returned to Earth, and compared to ground control samples for the determination of the influence of microgravity on cell survival and mutation induction. The results for both varied from experiment to experiment, yielding a large SD, but the μG sample results differed significantly from the 1G sample results for each of 2 experiments, with the mean ratio of μG to 1G being 0.55 for the concentration of viable cells and 0.59 for the fraction of thymidine kinase deficient (TK⁻) mutants. Among the mutants, non-loss of zygosity events (point mutations) were less frequent (31%) after μG incubation than after 1G incubation, which might be explained by the influence of μG on cellular metabolic or physiological function. Additional experiments are needed to clarify the effect of μG interferes on DNA repair.     

Radiation biology in space: a critical review.

A short summary of the results of radiobiological studies in space or on respective particles on ground will be given. Among the various types of radiation in space, the effect of heavy ions with high energy (HZE-particles) are most essential. Thus, radiobiology in space concerns mostly to the effect of these particles, in cells and in whole organism. Cell death, mutation and malignant transformation are the relevant endpoints, with can be studied on ground with heavy ions of different energy with suitable accelerators or in space, especially by the BIOSTACK concept. In space, however, the effect of microgravity has to be considered as well and there are hints, that under weightlessness the biological effect of radiation may be enhanced. There are still open questions to be answered concerning radioprotection of man in space. Further experiments are necessary.     

离轴反射式星敏感器地面标定设备光学系统设计

在星敏感器随航天器升空完成姿态测量任务之前,需在地面对其进行标定试验.为满足星敏感器更高精度标定要求,针对常规地面标定设备光学结构在应对大口径、长焦距、宽光谱需求时存在的弊端,设计了一种离轴光管作为准直光学系统,研究了离轴光管装调方法,并对像质进行了评价.重点研究了一套照明系统对星点亮度进行精确控制,采用LED阵列式背光板为光源,并利用照度计对光源亮度进行多次测试,测得的数据表明可对7个连续星等进行模拟,相邻星等间亮度模拟误差小于0.8%.所设计的光学系统可为研制深空探测星敏感器提供地面标定基础.      

地面姿态模拟光源控制系统研究

太阳敏感器和红外地球敏感器是卫星升空以后进行姿态控制的两个重要部件, 地面姿态模拟光源作为地面测试设备, 用来在地面上给这两个部件提供太阳模 拟信号和红外地球模拟信号. 本文设计了一套由4条光缝组成的模拟卫星自旋转 动的小型太阳模拟光源及针对地球同步轨道高度模拟15.6°张角的南 (北)红外两个地球模拟光源, 并为南北地球敏感器太阳保护探头提供了模拟 的太阳保护光源. 根据地面姿态模拟光源控制系统的组成和总体结构, 通 过分析计算给出各模拟光源之间严格的时序关系, 并对各模拟光源之间的时序 进行了实验测试, 结果表明模拟转速锁相误差不大于1ms, 各模拟光源时序 之间的角度误差小于0.5°.      

用于卫星入轨段测控的箭载天基测控中继系统

为满足卫星入轨段关键遥测参数下传和遥控指令上传的需求,设计了一种用于卫星入轨段测控的中继系统,方案主要基于火箭现成天基测控终端和卫星现成测控设备。介绍了中继系统的组成、工作原理和工作流程,研究了天基测控相控阵天线波束指向算法,设计了一种卫星遥测、遥控信号中继功能的地面测试系统。该箭载中继系统在快舟一号甲火箭上完成了两次飞行试验验证,两次飞行试验中继转发的卫星遥测数据完整,箭载卫星通信终端接收用户卫星遥测数据的载噪比大于20dB;地面测控中心接收天基遥测返向信号比特信噪比相对接收门限有3dB以上的余量。试验表明,该箭载天基测控中继系统通信链路余量充足,工作可靠,相比通过地面测控资源保障或卫星自身使用天基测控可节省一半以上成本。     

Pc5 Oscillation Analysis by the Satellite and Ground-Based Data

Large amplitude Pc5 event was observed in the space and on ground on August 3, 2001, about three hours after contact of the strong discontinuity in the solar wind with the magnetosphere according to data from ACE and Wind satellites. The Pc5 amplitude was as high as 15 nT in the tail of magnetosphere and about 5 nT at the ground based stations. In the magnetosphere Pc5 waves were observed by Cluster and Polar satellites, which occupied positions in the morning part of the near tail at the close field lines but were parted by distance of 11.5 Re, mainly along the x-axis of the GSM coordinate system. Both compressional and transverse components of the Pc5 wave activity were observed in the space, with the transverse component having the larger amplitude. Time delay between the Cluster and Polar satellites was about 8 minutes, which could be interpreted as a wave propagation from the geomagnetic tail to the Earth with the 150 km/s group velocity. The ground-based Pc5 activity was analysed by using data from the Image magnetometer network. Doubtless demonstrations of a field line resonant structure were found in variations of amplitude and polarization with latitude. Finnish chain of search coil magnetometers observed modulated Pc1 emission simultaneously with the Pc5 wave train. A possibility of non-linear impact of Pc5 wave energy on the plasma and waves in the magnetosphere is discussed.     

空间小鼠实验有效载荷研究进展

啮齿动物是空间研究中常见的模型对象,已开展的空间生物实验中,小鼠表现出对飞行条件的有效适应.通过空间培养,研究者可对失重环境下小鼠的生理行为、骨骼和神经系统变化做进一步研究分析.本文对空间小鼠实验有效载荷的研究进展及其空间飞行实验进行了概述,为中国空间站上的小鼠培养箱设计提供参考.概述了地面小鼠培养技术和装置,为空间小...     

Differentiation of Dictyostelium discoideum vegetative cells into spores during Earth orbit in space.

We reported previously that emerged amoebae of Dictyostelium (D.) discoideum grew, aggregated and differentiated to fruiting bodies with normal morphology in space. Here, we investigated the effects of space radiation and/or microgravity on the number, viability, kinetics of germination, growth rate and mutation frequency of spores formed in space in a radiation-sensitive strain, gamma s13, and the parental strain, NC4. In gamma s13, there were hardly spores in the fruiting bodies formed in space. In NC4, we found a decrease in the number of spores, a delay in germination of the spores and delayed start of cell growth of the spores formed in space when compared to the ground control. However, the mutation frequency of the NC4 spores formed in space was similar to that of the ground control. We conclude that the depression of spore formation might be induced by microgravity and/or space radiation through the depression of some stage(s) of DNA repair during cell differentiation in the slime mold.     

伴随磁层稳态对流的磁暴及磁暴期间环电流的特征

参考活跃的磁层稳态对流标准,选取了2001-2017年12个伴随磁层稳态对流的磁暴,研究发现这些磁暴存在以下共性:有长达约10h的漫长主相;其SYM-H存在一个最小值的平台期,约持续3～10h;这些磁暴发生时,部分环电流持续位于昏侧,其持续时间和行星际磁场分量Bz的稳定南向驱动时间相等.此外,这些磁暴发生时,其平台期的...     

LED光谱对模拟空间培养箱中植物生长发育的影响

通过研究在空间植物培养箱中利用LED作为光源对植物生长发育的作用, 并以荧光灯作为对照, 评估LED光源在空间植物培养中的优缺点, 可为中国即将在空间实验室天宫二 号和空间站中开展的高等植物生长实验提供参考. 利用不同比例的红光与白光LED组合光源, 研究光谱组成(红蓝光比例)、光照强度、光周期和气体流通等条件对于模拟空间 植物培养箱中拟南芥和水稻生长发育的影响. 结果表明, 与荧光灯相比, 红蓝光比例高的LED会导致拟南芥提早开花和水稻叶片的早衰. 红蓝光峰值比在3.9左右时, 拟南芥 和水稻生长最为有利; 红蓝光峰值比超过16则明显抑制拟南芥和水稻的生长, 导致叶片早衰. 另外, 在密闭培养箱中, 光强小于150μmol·m-2·s-1时, 增加光照强度可以部分抵消气体流通不足导致拟南芥植物生长的抑制, 而光照强度大 于150μmol·m-2·s-1时, 光强越大拟南芥的生长发育受到抑制越严重. 水稻对密闭培养环境中高光强的耐受性明显好于拟南芥. 因此, 在设计空间植物培养箱的LED光照系统时, 红蓝光的比例选择是关键, 此外还需综合考虑空间微重力条件下气体对流变化影响植物对光的反应.      

天宫二号碲化锌晶体生长

在天宫二号飞船综合材料实验炉六工位采用碲熔剂法生长了碲化锌晶体,生长时最高温度为800℃,以0.5mm·h-1的提拉速度向炉膛内部提拉生长晶体.飞行实验后,用相同实验参数在地面进行了对比实验.结果发现,空间样品尾部有一个非常大的橙色结晶区域（约10mm×6mm×2mm）,而地面生长样品中碲化锌晶体尺寸仅为约3mm×3mm×1mm,空间生长的碲化锌晶粒尺寸明显优于地面.空间微重力环境下,由于毛细作用,空间样品的塞子处有Te和ZnTe的外延膜生成.而地面生长的锭条在塞子处只有零星点状气相生产物.因此微重力条件有利于碲化锌晶体材料的生长.