Toward optimizing lighting as a countermeasure to sleep and circadian disruption in space flight

Light is being used as a pre-launch countermeasure to circadian and sleep disruption in astronauts. The effect of light on the circadian system is readily monitored by measurement of plasma melatonin. Our group has established an action spectrum for human melatonin regulation and determined the region of 446-477 nm to be the most potent for suppressing plasma melatonin. The aim of this study was to compare the efficacy of 460 and 555 nm for suppressing melatonin using a within-subjects design. Subjects (N=12) were exposed to equal photon densities (7.18 x 10(12) photons/cm2/s) at 460 and 555 nm. Melatonin suppression was significantly stronger at 460 nm (p<0.02). An extension to the action spectrum showed that 420 nm light at 16 and 32 microW/cm2 significantly suppressed melatonin (p<0.04 and p<0.002). These studies will help optimize lighting countermeasures to circadian and sleep disruption during spaceflight.     

Initial characterization of the microgravity environment of the international space station: increments 2 through 4

The primary objective of the International Space Station (ISS) is to provide a long-term quiescent environment for the conduct of scientific research for a variety of microgravity science disciplines. This paper reports to the microgravity scientific community the results of an initial characterization of the microgravity environment on the International Space Station for increments 2 through 4. During that period almost 70,000 hours of station operations and scientific experiments were conducted. 720 hours of crew research time were logged aboard the orbiting laboratory and over half a terabyte of acceleration data were recorded and much of that was analyzed. The results discussed in this paper cover both the quasi-steady and vibratory acceleration environment of the station during its first year of scientific operation. For the quasi-steady environment, results are presented and discussed for the following: the space station attitudes Torque Equilibrium Attitude and the X-Axis Perpendicular to the Orbital Plane; station docking attitude maneuvers; Space Shuttle joint operation with the station; cabin de-pressurizations and the station water dumps. For the vibratory environment, results are presented for the following: crew exercise, docking events, and the activation/de-activation of both station life support system hardware and experiment hardware. Finally, a grand summary of all the data collected aboard the station during the 1-year period is presented showing where the overall quasi-steady and vibratory acceleration magnitude levels fall over that period of time using a 95th percentile benchmark.     

Readaptation of the vestibuloocular reflex to 1g-condition in immature lower vertebrates (Xenopus laevis) after micro- or hypergravity exposure

The effects of altered gravitational conditions (AGC) on the development of the static vestibulo-ocular reflex (VOR) and readaptation to 1g were investigated in the amphibian Xenopus laevis. Tadpoles were exposed to microgravity (μg) during the German Space Mission D-2 for 10 days, using the STATEX closed survival system, or to 3g for 9 days during earth-bound experiments. At the beginning of AGC, the tadpoles had not yet developed the static VOR.

The main results were: (i) Tadpoles with ug- or 3g-experience had a lower gain of the static VOR than the 1g-controls during the 2nd and 5th post-AGC days, (ii) Readaptation to response levels of 1g-reared controls usually occurred during the following weeks, except in slowly developing tadpoles with 3g-experience. Readaptation was less pronounced if, during the acute VOR test, tadpoles were rolled from the inclined to the normal posture than in the opposite test situation.

It is postulated that (i) gravity is necessarily involved in the development of the static VOR, but only during a period including the time before onset of the first behavioural response; and (ii) readaptation which is superimposed by the processes of VOR development depends on many factors including the velocity of development, the actual excitation level of the vestibular systems and the neuroplastic properties of its specific pathways.     

Recent results of the joint ESA-DARA/IBMP experiments Biokosmos "Seeds"

Comparison of experimental data obtained from short (SDEF) and long duration exposure flights (LDEF) have recently led to results which will be significant for longer and/or repeated sojourn of man in space. Under orbital conditions biological stress and damage are induced in test subjects by cosmic radiation, especially the high energetic, densely ionizing component of heavy ions. Plant seeds were successful model systems for a biotest in studying the physiological damages and mutagenic effect caused by ionizing cosmic radiation in particular stem cells. Dosimetrically, the subdivision into charge- and Let-groups reveals the contribution of the intermediate group (LET = 350-1000 MeV/cm) due to the medium heavy ions (Z = 6-10). Their relative contribution increases with the lower inclination of the orbit of LDEF-1; on the other hand, the total fluence becomes higher with longer duration of the flight. The observed endpoints of the biological radiation damage hint at a correlation with particle dose rate rather than with the dose; additionally, data on shielding effects inside and outside the space craft and its exposure were gained from the different SDEF- and LDEF-missions.     

非地球同步轨道的应用潜力

最近的一项研究详细论述了在通信业务高峰期,利用非地球同步轨道卫星通信系统所具有的巨大优势。     

圆柱体上的印刷振子阵列天线

该文给出了两种小半径(r=1.5λo)圆柱体共形印刷振子阵列天线的设计和测试结果。这两种阵列天线的单元振子有不同的取向:一种取为轴线方向;另一种取为圆弧方向。首先将单元振予印刷在一柔软薄基片的两侧,然后将其包裹在金属圆柱体的蜂窝状绝缘层(ε_r=1.1,h=0.15λo)上。该结果具有较宽的频率、较弱的表面波以及较低的寄生辐射损耗的特点。所得结果表明,圆柱体共形印刷振子阵列天线具有与平面阵列天线相近的辐射效率,且实验结果与理论分析结果符合良好。     

固体火箭发动机点火器热通量的测量

使用箔式铂热通量计,对两种几何形状不同的点火器进行瞬间和轴向热通量分布的测量。所用的参数是不同的点火药量,管子长度和喷管喉径。对烟火剂燃烧产生的粒状物质的粒度分布作了研究,并且推论了这种粒子分布对总热量的影响。辐射在总热量传递过程中相对来说是不重要的,而在点火器作用期间,业径发现,由于粒子传热引起的“点”的热通量是热传递的最重要方式之一,事实上,这种传热方式可能是固体火箭发动机中点火火焰最初出现的原因。     

航天飞机尾部服务塔的设计和研制

航天飞机的成功发射取决于两个尾部服务塔的正常工作。通过完整的设计、研制和试验计划保证了尾部服务塔工作的可靠性。在前一篇文章(参考文献1)中，已叙述了尾部服务塔的方案验证试验。本文提出了方案验证试验的结果和对尾部服务塔样机设计所带来的影响。简述了设计准则，对所提出的尾部服务塔样机试验作了阐述。     

Proposal for a new radiation dose control system for future manned space flights

Radiation risk on a future long-duration manned space mission appears to be one of the basic factors in planning and designing the mission. Since 1988 different active dosimetric investigations has been performed on board the MIR space station by the Bulgarian-Russian dosimeter-radiometer LIULIN and French tissue-equivalent proportional counters CIRCE and NAUSICAA. A joint French-Bulgarian-Russian dosimetry experiment and the dosimetry-radiometry system RADIUS-MD have been developed for the future MARS-96 mission. On the base of the results and experience of these investigations a conception for a new radiation dose control system for the future orbital stations, lunar bases and interplanetary space ships is proposed. The proposed system which consists of different instruments will allow personal radiation control for crew members, radiation monitoring inside and outside each habitat, analysis and forecasting of the situation and will suggest procedures to minimize the radiation risk.     

低截获概率雷达的特征和机载系统

1 低截获概率雷达的特征 许多组合特性有助于防止低截获概率（LPI）雷达被现代截获接收机探测到。这些特性集中在天线（天线方向图和扫描图形）和发射机（辐射波形）中。