The PROCESS experiment: amino and carboxylic acids under Mars-like surface UV radiation conditions in low-earth orbit

The search for organic molecules at the surface of Mars is a top priority of the next Mars exploration space missions: Mars Science Laboratory (NASA) and ExoMars (ESA). The detection of organic matter could provide information about the presence of a prebiotic chemistry or even biological activity on this planet. Therefore, a key step in interpretation of future data collected by these missions is to understand the preservation of organic matter in the martian environment. Several laboratory experiments have been devoted to quantifying and qualifying the evolution of organic molecules under simulated environmental conditions of Mars. However, these laboratory simulations are limited, and one major constraint is the reproduction of the UV spectrum that reaches the surface of Mars. As part of the PROCESS experiment of the European EXPOSE-E mission on board the International Space Station, a study was performed on the photodegradation of organics under filtered extraterrestrial solar electromagnetic radiation that mimics Mars-like surface UV radiation conditions. Glycine, serine, phthalic acid, phthalic acid in the presence of a mineral phase, and mellitic acid were exposed to these conditions for 1.5 years, and their evolution was determined by Fourier transform infrared spectroscopy after their retrieval. The results were compared with data from laboratory experiments. A 1.5-year exposure to Mars-like surface UV radiation conditions in space resulted in complete degradation of the organic compounds. Half-lives between 50 and 150?h for martian surface conditions were calculated from both laboratory and low-Earth orbit experiments. The results highlight that none of those organics are stable under low-Earth orbit solar UV radiation conditions.     

The PROCESS experiment: exposure of amino acids in the EXPOSE-E experiment on the international space station and in laboratory simulations

To understand the chemical behavior of organic molecules in the space environment, amino acids and a dipeptide in pure form and embedded in meteorite powder were exposed in the PROCESS experiment in the EXPOSE-E facility mounted on the European Technology Exposure Facility (EuTEF) platform on board the International Space Station (ISS). After exposure to space conditions for 18 months, the samples were returned to Earth and analyzed in the laboratory for reactions caused by solar UV and cosmic radiation. Chemical degradation and possible racemization and oligomerization, the main reactions caused by photochemistry in the vacuum ultraviolet domain (VUV, wavelength range 100-200?nm for photon energy from 6.2 to 12.4?eV) were examined in particular. The molecules were extracted and derivatized by silylation and analyzed by gas chromatograph coupled to a mass spectrometer (GC-MS) to quantify the rate of the degradation of the compounds. Laboratory exposure in several wavelength ranges from UV to VUV was carried out in parallel in the Cologne Deutsches Zentrum für Luft- und Raumfahrt (DLR) Center and Centre de biophysique moléculaire (CBM) laboratories. The results show that resistance to irradiation is a function of the chemical nature of the exposed molecules and the wavelengths of the UV light. The most altered compounds were the dipeptide, aspartic acid, and aminobutyric acid. The most resistant were alanine, valine, glycine, and aminoisobutyric acid. Our results also demonstrate the protective effect of meteorite powder, which reemphasizes the importance of exogenic contribution to the inventory of prebiotic organics on early Earth.     

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.     

The Urey instrument: an advanced in situ organic and oxidant detector for Mars exploration

The Urey organic and oxidant detector consists of a suite of instruments designed to search for several classes of organic molecules in the martian regolith and ascertain whether these compounds were produced by biotic or abiotic processes using chirality measurements. These experiments will also determine the chemical stability of organic molecules within the host regolith based on the presence and chemical reactivity of surface and atmospheric oxidants. Urey has been selected for the Pasteur payload on the European Space Agency's (ESA's) upcoming 2013 ExoMars rover mission. The diverse and effective capabilities of Urey make it an integral part of the payload and will help to achieve a large portion of the mission's primary scientific objective: "to search for signs of past and present life on Mars." This instrument is named in honor of Harold Urey for his seminal contributions to the fields of cosmochemistry and the origin of life.     

The effectiveness of end-of-life re-orbiting for debris mitigation in geostationary orbit

The effect of satellite breakups over 72 years, as a function of the end-of-life re-orbiting altitude (0–2000km), was analyzed in terms of fragment contribution to the object density in the geostationary orbit (GEO) ring, both in the short- and long-term. In the short-term, the explosions in GEO are the most detrimental for the GEO ring environment, though the average fragment density in the ring is never higher than 1/5 of the background, decreasing to less than 1/100 of the existing environment after 4 years (apart from a density rebound 5 decades later, due to luni-solar perturbations). Spacecraft end-of-life re-orbiting is a possible mitigation solution. But the re-orbiting altitude is critical if explosions continue to occur. In order to reduce the post-event average density by 1 order of magnitude with respect to an explosion occurring in GEO, more than 500km of re-orbiting is needed. Concerning the long-term environmental impact, the re-orbiting strategy supported by Inter-Agency Space Debris Coordination Committee (IADC) seems adequate to guarantee, after 2–3 years, a long-term average density of fragments in the GEO ring of at least 2 orders of magnitude below the existing background. But at least 1000km of re-orbiting are needed to stay below that threshold in the short-term too. In conclusion, the re-orbiting strategy recommended by IADC is totally adequate in the long-term, but only if satellite passivation is extensively carried out.     

CROCODILE: an automated apparatus for organic crystal growth from solution

CROCODILE (CROissance de Cristaux Organiques par DIffusion Liquide dans l'Espace) is a space instrument dedicated to crystal growth from solution. The selected material N (4 nitrophenyl) (L) prolinol (NPP) is the result of studies on organic crystal in the frame of an extended program initiated by CNES for many years. The apparatus was flown aboard PHOTON, an automatic satellite, in April 1990, for a flight duration of more than 15 days. This paper describes the instrument design, with emphasis on specific and original technology well adapted to crystal growth from solution, and extendable to any space experiment on fluids. Preliminary details of the flight campaign will also be discussed.     

基于在轨运行状态的卫星稳定性与可靠性研究

为解决卫星在轨运行故障率较高的问题,文章分析了卫星在轨运行的特点,定义了卫星在轨工作状态及其与系统稳定性变化的关系。研究表明:对在轨运行安全稳定状态进行控制,能使状态保持或向高级跃迁,可提升卫星稳态及可靠性。文章最后提出了提高卫星在轨运行稳定性与可靠性的在轨运行策略与技术方向。     

Astromedicine and astrolaw: Emerging issues for advanced missions beyond Earth orbit

It is generally agreed within the scientific community that provision of appropriate medical facilities and administration of quality health care to astronauts are of great importance. However, for the more complex and remote missions envisaged for the future, issues of liability, responsibility and damage relating to medical practice may take on a greater significance and will need to be addressed. The author briefly reviews potential issues which may arise in the context of medical emergencies, crew autonomy and environmentally altered physiological status which characterize some projected advanced space missions and argues that the law of outer space will need to be expanded to take account of them.     

Fourth-order theories for orbit predictions for low- and high-eccentricity orbits in an oblate atmosphere with scale height dependent on altitude

Two new fourth-order non-singular analytical theories for the motion of near-Earth satellite orbits with air drag are developed for low- and high-eccentricity orbits in an oblate atmosphere with variation of density scale height with altitude. Uniformly regular Kustaanheimo–Stiefel (KS) canonical elements are utilized for low-eccentricity orbits and KS element equations are employed for high-eccentricity orbits. Only two of the nine equations are solved analytically to compute the state vector and change in energy at the end of each revolution, due to symmetry in the equations of motion. The analytical solutions are compared with the numerically integrated values up to 100 revolutions, and found to be quite accurate over a wide range of eccentricity, perigee height and inclination.     

LARES successfully launched in orbit: Satellite and mission description

On February 13th 2012, the LARES satellite of the Italian Space Agency (ASI) was launched into orbit with the qualification flight of the new VEGA launcher of the European Space Agency (ESA). The payload was released very accurately in the nominal orbit. The name LARES means LAser RElativity Satellite and summarises the objective of the mission and some characteristics of the satellite. It is, in fact, a mission designed to test Einstein's General Relativity Theory (specifically ‘frame-dragging' and Lense-Thirring effect). The satellite is passive and covered with optical retroreflectors that send back laser pulses to the emitting ground station. This allows accurate positioning of the satellite, which is important for measuring the very small deviations from Galilei–Newton's laws. In 2008, ASI selected the prime industrial contractor for the LARES system with a heavy involvement of the universities in all phases of the programme, from the design to the construction and testing of the satellite and separation system. The data exploitation phase started immediately after the launch under a new contract between ASI and those universities. Tracking of the satellite is provided by the International Laser Ranging Service. Due to its particular design, LARES is the orbiting object with the highest known mean density in the solar system. In this paper, it is shown that this peculiarity makes it the best proof particle ever manufactured. Design aspects, mission objectives and preliminary data analysis will be also presented.     

New methods for microbial contamination monitoring: an experiment on board the MIR orbital station

Experiment T2, carried out during the Euromir'95 mission, was an important step toward innovative methods for spacecraft microbial contamination monitoring. A new standard sampling technique permitted samples to be analysed by different means. On board, two analysis methods were tested in parallel: Bioluminescence and Miniculture. In turn, downloaded samples are being analysed by polymerase chain reaction (PCR), a powerful and promising method for the rapid detection, identification and quantification of pathogens and biofouling agents in closed manned habitats.     

The Skylab sleep monitoring experiment: methodology and initial results

The sleep monitoring experiment permitted an objective evaluation of sleep characteristics during the first two manned Skylab flights. Hardware located onboard the spacecraft accomplished data acquisition, analysis, and preservation, thereby permitting near-real-time evaluation of sleep during the flights and more detailed postmission analysis. The crewman studied during the 28-Day Mission showed some decrease in total sleep time an increase in the percentage of Stage 4 sleep, while the subject in the 59-Day Mission exhibited little change in total sleep time and a small decrease in Stage 4 and REM sleep. Some disruption of sleep characteristics was seen in the final days of both missions, and both subjects exhibited decreases in REM-onset latency in the immediate postflight period. The relatively minor changes seen were not of the type nor magnitude which might be expected to be associated with significant degradation of performance capability.     

The formation of sulfate and elemental sulfur aerosols under varying laboratory conditions: implications for early earth

The presence of sulfur mass-independent fractionation (S-MIF) in sediments more than 2.45?×?10(9) years old is thought to be evidence for an early anoxic atmosphere. Photolysis of sulfur dioxide (SO(2)) by UV light with λ?相似文献   

航天器密封管路的气态工质与示漏气体 漏率等效关系研究

利用多种气体分析仪,采取四级质谱定量分析技术,分别测定He、N₂、N_e、CF₄、Kr等气体在不同入口压力下通过不同的人造漏孔的漏率;经过对同工况下气体间漏率比对,研究气体间漏率等效关系。试验结果表明:气体在不同工况下处于不同的流动领域,且其漏率与入口压力存在着不同的数值关系,经分析试验结果得出适用于气体全流域的漏率经验公式;气体间漏率的等效关系在低漏率及高漏率端始终呈平滑的线性关系,而在中间的过渡区域呈四或五次多项式关系;但是CF₄与H_e的漏率等效性呈线性关系,显示出多原子分子与单、双原子分子在粒子输运过程中存在着差异。试验结果为示漏工质漏率指标的制定提供了基础数据。     

From Earth's orbit to the outer planets and beyond: Psychological issues in space

Current planning for the first interplanetary expedition to Mars envisions a crew of 6 or 7 people and a mission duration of around 2.5 years. However, this time frame is much less than that expected on expeditions to the outer solar system, where total mission durations of 10 years or more are likely. Although future technological breakthroughs in propulsion systems and space vehicle construction may speed up transit times, for now we must realistically consider the psychological impact of missions lasting for one or more decades.Available information largely deals with on-orbit missions. In research that involved Mir and ISS missions lasting up to 7 months, our group and others have studied the effects of psychological and interpersonal issues on crewmembers and on the crew-ground relationship. We also studied the positive effects of being in space. However, human expeditions to the outer planets and beyond will introduce a number of new psychological and interpersonal stressors that have not been experienced before. There will be unprecedented levels of isolation and monotony, real-time communication with the Earth will not be possible, the crew will have to work autonomously, there will be great dependence on computers and other technical resources located on board, and the Earth will become an insignificant dot in space or will even disappear from view entirely.Strategies for dealing with psychological issues involving missions to the outer solar system and beyond will be considered and discussed, including those related to new technologies being considered for interstellar missions, such as traveling at a significant fraction of the speed of light, putting crewmembers in suspended animation, or creating giant self-contained generation ships of colonists who will not return to Earth.     

等质量立体五星库仑编队飞行的分析与控制

分析了立体五星编队在静电力和万有引力作用下的静态构型。分别讨论了五星编队在共线和平面情况下的静态构型,着重研究了五星构成立体双直角六棱锥构型时各个卫星所带的静电荷量。由于地球同步轨道的卫星所受到的作用力不仅是万有引力与静电库仑力,还有空气阻力等摄动力,因此只有对其施加控制,卫星才能在静态平衡点保持编队构型的稳定性。本文采用线性二次型最优控制方法来保持编队的静态构型稳定,并通过Matlab实现了五星立体库伦编队飞行控制仿真。     

卫星在轨主要故障模式、原因分析及措施建议

分析国内外近10多年来的卫星在轨故障情况,总结6类灾难性及严重在轨故障模式;提炼出星上典型设备/部件的主要在轨故障模式。在此基础上,从新技术及新状态的地面验证充分性、复杂工艺的稳定性、元器件及电装质量、空间环境影响、软件设计、地面操作等方面分析在轨故障的主要原因,并给出措施建议,旨在为卫星系统可靠性设计、主要设备/部件的薄弱环节识别及可靠性设计提供参考。     

地球静止轨道卫星SADA热设计及高温工况温度分布研究

针对地球静止轨道卫星SADA轴系周向或轴向温度梯度过大导致卡死的故障情况,开展某卫星SADA热设计、热仿真及太阳模拟器光照试验研究。采用挡光板及均温措施等热设计减小SADA温度梯度及外热流影响。试验外热流模拟冬至工况,舱内边界温度25℃,通过在其内部和外部布置88个温度测点,得出SADA内部的电缆束、功率盘片及电刷温度较高。轴系两端面周向最大温差分别为1.2℃和8℃,轴系两端面最大温差6.8℃。在此温度环境下,SADA工作正常,证明了其本身及热控设计的合理性。热仿真计算结果与试验结果一致性较好。研究结果还得到了在轨数据的验证。SADA数学模型、试验方法和结果可为后续型号不同工况条件工作的SADA提供热设计指导。