Radiation protection in space

Radiation environment, basic concepts of radiation protection, and specific aspects of the space radiation field are reviewed. The discussion of physico-chemical and subcellular radiation effects includes mechanisms of radiation action and cellular consequences. The discussion of radiobiological effects includes unique aspects of HZE particle effects, space flight findings, terrestrial findings, analysis of somatic radiation effects and effects on critical organs, and early and delayed effects. Other topics include the impact of the space flight environment, measurement of radiation exposure, establishing radiation protection limits, limitations in establishing space-based radiation exposure limits, radiation protection measures, and recommendations.     

星载光纤陀螺的最优调制深度

为了选取合适的调制深度以提高星载光纤陀螺在空间辐射环境下的工作性能,通过对闭环光纤陀螺输出信号的信噪比分析建立了光纤陀螺随机游走系数与调制深度的关系的模型。根据该模型对光纤辐射致衰减、光纤长度、光源光功率对最优调制深度的影响进行了仿真研究。结果表明：光纤辐射致衰减越小、光源光功率越大,则光纤陀螺的最优调制深度越大,且相应的随机游走系数越小。增加光纤长度将降低光纤陀螺的最优调制深度,当光纤衰减较大且光纤较长时,过调制技术可能会使光纤陀螺性能恶化。因此,在星载光纤陀螺的设计过程中应根据实际情况对调制深度进行优化,以保证陀螺获得最优的工作性能。理论分析和仿真结果为星载光纤陀螺最优调制深度的选取提供了依据。     

Observations of March 29, 2006 solar eclipse in the radio range at wavelengths of 3.2 and 4.9 cm

We present observations and processing of the March 29, 2006 solar eclipse data at the radio telescopes RT-3 (λ = 4.9 cm) and RT-2 (λ = 3.2 cm) of the Kislovodsk Solar Station of the Pulkovo Astronomical Observatory of RAS. Registration of the emission flux was conducted by electron method with a time resolution of 0.5 s. Compact sources on the solar disk are identified, and the contribution of coronal holes into the integral flux is determined. Comparisons to observations in the optical and X-ray ranges are performed. The intensity of sources behind the solar limb is estimated. The ratio of the intensity of residual radiation in the maximum phase to the solar emission before the eclipse was equal to 3.7 and 5.9% for 3.2 and 4.9 cm, respectively.     

Radiation protection guidelines for space activities

At the beginning of the space age the dangers of hurtling into space were considerable. Despite this fact, radiation risks were examined in the U.S.S.R. and the U.S.A. and recommendations were made to limit the exposure of the crews to radiation. To date the radiation exposures of crews on missions in low-Earth orbits have been low. Now that missions in low-Earth orbit are becoming longer in duration and new missions into deep space are being considered, radiation protection guidelines become more important. Recently the estimates of the risks of radiation-induced cancer have been increased and new guidelines on radiation exposure limits for crew members must be developed. For deep space missions the guidelines take into account the risks posed by heavy ions. Unfortunately, knowledge about these risks is insufficient. If the new risk estimates are applied, current career dose limits may have to be reduced by a factor of two.     

Feasibility study of astronaut standardized career dose limits in LEO and the outlook for BLEO

Cosmic Study Group SG 3.19/1.10 was established in February 2013 under the aegis of the International Academy of Astronautics to consider and compare the dose limits adopted by various space agencies for astronauts in Low Earth Orbit. A preliminary definition of the limits that might later be adopted by crews exploring Beyond Low Earth Orbit was, in addition, to be made. The present paper presents preliminary results of the study reported at a Symposium held in Turin by the Academy in July 2013. First, an account is provided of exposure limits assigned by various partner space agencies to those of their astronauts that work aboard the International Space Station. Then, gaps in the scientific and technical information required to safely implement human missions beyond the shielding provided by the geomagnetic field (to the Moon, Mars and beyond) are identified. Among many recommendations for actions to mitigate the health risks potentially posed to personnel Beyond Low Earth Orbit is the development of a preliminary concept for a Human Space Awareness System to: provide for crewed missions the means of prompt onboard detection of the ambient arrival of hazardous particles; develop a strategy for the implementation of onboard responses to hazardous radiation levels; support modeling/model validation that would enable reliable predictions to be made of the arrival of hazardous radiation at a distant spacecraft; provide for the timely transmission of particle alerts to a distant crewed vehicle at an emergency frequency using suitably located support spacecraft. Implementation of the various recommendations of the study can be realized based on a two pronged strategy whereby Space Agencies/Space Companies/Private Entrepreneurial Organizations etc. address the mastering of required key technologies (e.g. fast transportation; customized spacecraft design) while the International Academy of Astronautics, in a role of handling global international co-operation, organizes complementary studies aimed at harnessing the strengths and facilities of emerging nations in investigating/solving related problems (e.g. advanced space radiation modeling/model validation; predicting the arrivals of Solar Energetic Particles and shocks at a distant spacecraft). Ongoing progress in pursuing these complementary parallel programs could be jointly reviewed bi-annually by the Space Agencies and the International Academy of Astronautics so as to maintain momentum and direction in globally progressing towards feasible human exploration of interplanetary space.     

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.     

光学遥感器光电信号处理系统的空间辐射效应研究

文章针对光学遥感器光电信号处理系统,描述了空间辐射效应研究的方法和途径。首先介绍了光学遥感器常用运行轨道的空间辐射环境,然后选择光学遥感器的光电信号处理系统作为分析模型,介绍了光电信号处理系统的电路组成和主要元器件,从器件级、电路级到系统级对空间辐射效应的危害性进行分析,并且结合元器件的抗辐射性能现状,归纳了辐射效应的薄弱环节及主要元器件需要进行的辐照试验。最后对空间辐射效应研究的方法和步骤进行了总结。     

A Method to Measure Absorptivity and Emissivity of Temperature-Controlling Coatings of Spacecraft Using Radiation Flux of Variable Intensity

A new method of determining the absorptivity and emissivity of surfaces with the use of a radiation flux of variable intensity is described. It is expedient to use this method in order to control the variations of integral optical coefficients of temperature-controlling coatings in the course of a long-term spacecraft flight. The method is developed on the basis of solving the inverse problem for a mathematical model of thermal balance for a thin metal plate. The stability of the algorithm of processing the results of measurements is analyzed for various levels of random errors. Some recommendations concerning the technical implementation of the method in the laboratory and space conditions are given. The method suggested has a number of advantages in comparison with methods used before, especially if it is used in space conditions. The main advantage is the possibility of varying the radiation flux incident on the surface of a specimen under study from an external source according to any smooth law.     

Radiation protection of astronauts in LEO

Radiological protection for space flights is often perceived as a technico-scientific problem. All this is the result of the effects of radiation encountered in space and manned flight conditions. The main characteristics of this radiation come from its complex composition and its large energy spectrum which must be taken into account as well as flux variations by both solar activity and the vehicle position on orbit. Inside a vehicle, structures constitute irregularly distributed shields and lead to a specific dose at each location. To be able to protect the crew, it is first necessary to understand the threat and therefore to identify the radiation environment: extraterrestrial and orbital. As the environment varies with both the orbit position and time, the dose received in each critical organ during missions must be determined and compared with acceptable limits. To counter the threat, which may exceed acceptable limits, a strategy is required, including the complementary aspects of prevention, detection, protection and possibly treatment.     

Method and Results of Direct Measurement of the Interstellar Neutral Helium Abundance and Isotopic Composition

One of the important astrophysical problems is the determination of the abundance of helium isotopes ³He and ⁴He in different regions of the Universe, because this abundance can reflect its history by pointing to the intensity of various possible processes of the creation and decay of light elements. This paper describes the method and results of the determination (for the first time performed by a direct method) of the helium isotopic abundance in the local interstellar medium surrounding the Solar system. The experiment was carried out on the manned Mir space station by long-term space exposure of samples of metal foil with their subsequent recovery to the Earth and detailed laboratory mass-spectrometric analysis. As a result, we succeeded in obtaining an estimation of the ⁴He concentration (about 7.5 × 10^–3 cm^–3) and the isotopic ratio ³He/⁴He (about1.7 × 10^–4) for the local interstellar medium.     

Probabilistic assessment of radiation risk for astronauts in space missions

Accurate estimations of the health risks to astronauts due to space radiation exposure are necessary for future lunar and Mars missions. Space radiation consists of solar particle events (SPEs), comprised largely of medium energy protons (less than several hundred MeV); and galactic cosmic rays (GCR), which include high-energy protons and heavy ions. While the frequency distribution of SPEs depends strongly upon the phase within the solar activity cycle, the individual SPE occurrences themselves are random in nature. A solar modulation model has been developed for the temporal characterization of the GCR environment, which is represented by the deceleration potential, ?. The risk of radiation exposure to astronauts as well as to hardware from SPEs during extra-vehicular activities (EVAs) or in lightly shielded vehicles is a major concern for radiation protection. To support the probabilistic risk assessment for EVAs, which could be up to 15% of crew time² on lunar missions, we estimated the probability of SPE occurrence as a function of solar cycle phase using a non-homogeneous Poisson model [1] to fit the historical database of measurements of protons with energy>30 MeV, Φ₃₀. The resultant organ doses and dose equivalents, as well as effective whole body doses, for acute and cancer risk estimations are analyzed for a conceptual habitat module and for a lunar rover during space missions of defined durations. This probabilistic approach to radiation risk assessment from SPE and GCR is in support of mission design and operational planning for future manned space exploration missions.     

γ射线辐射对空间光学玻璃透射率的影响

利用60Co γ-射线对钡冕玻璃（BaK3）、镧冕玻璃（LaK3）、火石玻璃（F10）、镧火石玻璃（LaF3）、轻火石玻璃（QF3）和重火石玻璃（ZF4）进行辐照,研究不同辐照剂量对光学透射率的影响及这些玻璃在空间光学系统中的适应性。光学透射率测试范围为400~1 100 nm。结果表明所有玻璃在辐照后可见光透射率都下降了,而在近红外波段下降不明显（除了QF3和LaF3）。尽管F10和QF3光学透射率在辐照前相似,但是辐照后F10衰减是所有玻璃中最小的,而QF3衰减最为严重。研究发现,当达到一定辐照剂量后,玻璃材料的透射率不再继续衰减,而是趋于稳定。这些结果为空间光学系统针对辐射进行冗余设计提供了依据。     

红蓝光敏探测器空间环境效应探测数据分析

红蓝光敏太阳电池空间环境效应探测器利用镓铟磷和三结砷化镓太阳电池来探测空间污染、原子氧和辐射环境及效应,搭载在中国空间技术研究院自主研制的“新技术验证一号”卫星上。文章通过分析红蓝光敏探测器在轨1年时间的探测数据,得到如下结论：红蓝光敏探测器污染电池板功率下降2.7%,等效污染累积增加量2.23×10^-5 g/cm^2,日均6×10^-8 g/cm^2;原子氧探测器在轨道高度499.226 km运行11个月,原子氧积分通量探测数据为9.7×10^20 AO/cm^2;辐射效应探测器（三结砷化镓太阳电池）在轨1年后累计接受辐射剂量（等效1 MeV电子注量）5.49×10^11 e/cm^2。     

航天员空间活动接受辐射剂量限值的研究

空间生物学辐射效应是由空间辐射环境引起的,空间辐射环境的变化受太阳活动性影响。空间辐射水平比地表面水平高,航天员在空间所接受剂量比地面人员接受的吸收剂量高出100倍甚至更高,并且高能重离子的生物效应显著。文章简要阐述了空间辐射环境、空间辐射生物学效应与航天员的辐射剂量限值等问题。     

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.     

Mutagenesis in bacterial spores exposed to space and simulated martian conditions: data from the EXPOSE-E spaceflight experiment PROTECT

As part of the PROTECT experiment of the EXPOSE-E mission on board the International Space Station (ISS), the mutagenic efficiency of space was studied in spores of Bacillus subtilis 168. After 1.5 years' exposure to selected parameters of outer space or simulated martian conditions, the rates of induced mutations to rifampicin resistance (Rif(R)) and sporulation deficiency (Spo(-)) were quantified. In all flight samples, both mutations, Rif(R) and Spo(-), were induced and their rates increased by several orders of magnitude. Extraterrestrial solar UV radiation (>110?nm) as well as simulated martian UV radiation (>200?nm) led to the most pronounced increase (up to nearly 4 orders of magnitude); however, mutations were also induced in flight samples shielded from insolation, which were exposed to the same conditions except solar irradiation. Nucleotide sequencing located the Rif(R) mutations in the rpoB gene encoding the β-subunit of RNA polymerase. Mutations isolated from flight and parallel mission ground reference (MGR) samples were exclusively localized to Cluster I. The 21 Rif(R) mutations isolated from the flight experiment showed all a C to T transition and were all localized to one hotspot: H482Y. In mutants isolated from the MGR, the spectrum was wider with predicted amino acid changes at residues Q469K/L/R, H482D/P/R/Y, and S487L. The data show the unique mutagenic power of space and martian surface conditions as a consequence of DNA injuries induced by solar UV radiation and space vacuum or the low pressure of Mars.     

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.     

Radiation engineering analysis of shielding materials to assess their ability to protect astronauts in deep space from energetic particle radiation

An analysis is performed on four typical materials (aluminum, liquid hydrogen, polyethylene, and water) to assess their impact on the length of time an astronaut can stay in deep space and not exceed a design basis radiation exposure of 150 mSv. A large number of heavy lift launches of pure shielding mass are needed to enable long duration, deep space missions to keep astronauts at or below the exposure value with shielding provided by the vehicle. Therefore, vehicle mass using the assumptions in the paper cannot be the sole shielding mechanism for long duration, deep space missions. As an example, to enable the Mars Design Reference Mission 5.0 with a 400 day transit to and from Mars, not including the 500 day stay on the surface, a minimum of 24 heavy lift launches of polyethylene at 89,375 lbm (40.54 tonnes) each are needed for the 1977 galactic cosmic ray environment. With the assumptions used in this paper, a single heavy lift launch of water or polyethylene can protect astronauts for a 130 day mission before exceeding the exposure value. Liquid hydrogen can only protect the astronauts for 160 days. Even a single launch of pure shielding material cannot protect an astronaut in deep space for more than 180 days using the assumptions adopted in the analysis. It is shown that liquid hydrogen is not the best shielding material for the same mass as polyethylene for missions that last longer than 225 days.     

OLTARIS: On-line tool for the assessment of radiation in space

OLTARIS (On-Line Tool for the Assessment of Radiation In Space) is a space radiation analysis tool available on the World Wide Web. It can be used to study the effects of space radiation for various spacecraft and mission scenarios involving humans and electronics. The transport is based on the HZETRN transport code and the input nuclear physics model is NUCFRG. This paper describes the tools behind the web interface and the types of inputs required to obtain results. Typical inputs are mission parameters and slab definitions or vehicle thickness distributions. Radiation environments can be chosen by the user. This paper describes these inputs as well as the output response functions including dose, dose equivalent, whole body effective dose equivalent, LET spectra and detector response models.     

极远紫外成像光谱仪在空间科学中的应用与展望

极远紫外成像光谱仪是空间科学研究中重要的数据获取工具,通过对不同天体目标极远紫外辐射的观测,可以反演出天体中主要物质的含量和变化规律,从而为空间天气、宇宙起源等许多前沿科学提供研究资料。文章分析了极远紫外成像光谱仪在空间科学研究中的优势,介绍了国际发展概况．列举了日地空间环境观测、地外行星体观测和宇宙空间观测3个应用领...