空间科学战略性先导科技专项引领中国空间科学发展

<正>空间科学战略性先导科技专项(以下简称空间科学先导专项)旨在加深对宇宙和地球的理解,通过自主和国际合作科学卫星计划,寻找空间科学领域新发现,并取得新突破。在"十二五"期间,空间科学先导专项部署了以下项目:"硬X射线调制望远镜"(HXMT)、"量子科学实验卫星"(QUESS)、"暗物质粒子探测"(DAMPE)卫星、实践-10(SJ-10)返回式科学实验卫星、"夸父"(KUAFU)计划、空间科学背景型号项目和空间科学预先研究项目。     

自动测试技术在备件研制中的应用

主要阐述了自动测斌技术住数字电路板备件研制方面的应用。通过对某型引俄设备数字电路板研制的验证事例,探索了ATE和LASAR仿真软件用于备件电路板研制与测试验证的方法。结合装备实验,证明了将仿真技术作为高效的电路设计验证手段,并将ATE作为通用测试验证平台的可行性和先进性。     

Testing baseline stability of some neutron monitors in Europe,Africa, and Asia

For six decades, the global network of neutron monitors (NMs) has provided a continuous stream of very valuable data to the heliophysics community, leading to many insights into the myriad modes of charged particle transport in the tangled magnetic fields that permeate the 3D heliosphere. Earlier, Ahluwalia and Ygbuhay (2012) reported on the drifts in some high latitude NM counting rates in the American zone. We continue our enquiry by testing the stability of the counting rate baselines of some NMs operating in Europe, Africa, and Asia. The data from these detectors have been extremely valuable for the short-term time variation studies, but caution is advised in using the data for long-term studies from NMs with baselines that are drifting for cause(s) unknown.     

Heterogeneous solid/gas chemistry of organic compounds related to comets,meteorites, Titan,and Mars: Laboratory and in lower Earth orbit experiments

To understand the evolution of organic molecules involved in extraterrestrial environments and with exobiological implications, many experimental programs in the laboratory are devoted to photochemical studies in the gaseous phase as well as in the solid state. The validity of such studies and their applications to extraterrestrial environments can be questioned as long as experiments conducted in space conditions, with the full solar spectrum, especially in the short wavelength domain, have not been implemented. The experiments that are described here will be carried out on a FOTON capsule, using the BIOPAN facility, and on the International Space Station, using the EXPOSE facility. Vented and sealed exposition cells will be used, which will allow us to study the chemical evolution in the gaseous phase as well as heterogeneous processes, such as the degradation of solid compounds and the release of gaseous fragments.     

Space law education in China: Status quo,shortcomings and possible ways out

Space law education has an essential role in the space capacity building of a country because of its importance for human resources development in space law. Comparisons between Canada and China, the European Union and China and the United States of America (USA) and China in space law degree education, course, teaching methodology, institute and practice and communication platform are provided in an attempt to review some issues which exist within the Chinese space law educational system and to seek a better choice for China’s space law education reform. Chinese space law education has achieved noticeable progress over the past two decades. However, it is still limited in comparison to its counterparts in Europe and Northern America. The range of the space law degree education programmes and space-law-related courses is comparatively limited. A gap remains between space law education and practice in China. Chinese space law classes are still dominated by the teacher-centred teaching methodology, although several universities have some new teaching practices. The establishment of seven space law-related research institutes plays an increasingly important role in Chinese space law education, space law and policy research and legal advisory services for the Chinese government and non-governmental sectors. However, these institutes still have a long way to go in comparison with their counterparts in Europe and Northern America. While China has established domestic research platforms for space law communication through international cooperation, it does not provide space law practice platforms for space law education. While international space law does not provide a direct legal foundation for space law education in China, Chinese educational laws can lay a profound legal foundation for Chinese space law education. To promote its national expertise and capacity in space law, based on the three-pillar model and the experiences of its counterparts in North America and Europe, China should adopt a systematic and sustainable regime for its space law education.     

Uncertainties in gravity wave parameters,momentum fluxes,and flux divergences estimated from multi-layer measurements of mesospheric nightglow layers

Measurements of dynamic parameters of atmospheric gravity waves, mainly the vertical wavelength, the momentum flux and the momentum flux divergence, are affected by large uncertainties crudely documented in the scientific literature. By using methods of error analysis, we have quantified these uncertainties for frequently observed temporal and spatial wave scales. The results show uncertainties of ～10%, ～35%, and ～65%, at least, in the vertical wavelength, momentum flux, and flux divergence, respectively. The large uncertainties in the momentum flux and flux divergence are dominated by uncertainties in the Brunt-Väisälä frequency and in spatial separation of the nightglow layers, respectively. The measured uncertainties in fundamental wave parameters such as the wave amplitude, intrinsic period, horizontal wavelength, and wave orientation are ～10% or less and estimated directly from our nightglow image data set. Other key environmental quantities such as the scale height and the Brunt-Väisälä frequency, frequently considered as constants in gravity wave parameter estimations schemes, are actually quite variable, presenting uncertainties of ～4% and ～9%, respectively, according to the several solar activity and seasonal atmosphere scenarios from the NRLMSISE-00 model simulated here.     

Comparison of Landsat OLI,ASTER, and Sentinel 2A data in lithological mapping : A Case study of Rich area (Central High Atlas,Morocco)

The eastern part of the Rich area consists of the massive Paleozoic and Meso-Cenozoic cover formations that present the geodynamic development of the study area, where is characterized by various carbonate facies of Jurassic age. The geographical characteristic of the study area leaves the zone difficult to map by conventional methods. The objective of this work focuses on the mapping of the constituent lithological units of the study area using multispectral data of Landsat OLI, ASTER, and Sentinel 2A MSI. The processing of these data is based on a precise methodology that distinguishs and highlights the limits of the different lithological units that have an approximate similarity of spectral signature. Three techniques were used to enhance the image including Principal Component Analysis (PCA), Minimum Noise Fraction (MNF), and Independent Component Analysis (ICA). Lithological mapping was performed using two types of supervised classification : Maximum likelihood classifier (MLC) and Support Vector Machine (SVM).The results of processing data show the effectiveness of Sentinel 2A data in mapping of lithological units than the ASTER and Landsat OLI data. The classification evaluation of two methods of the Sentinel 2A MSI image showed that the SVM method give a better classification with an overall accuracy of 93,93% and a Kappa coefficient of 0.93, while the MLC method present an overall accuracy of 82,86% and a Kappa coefficient of 0.80. The results of mapping obtained show a good correlation with the geological map of the study area as well as the efficiency of remote sensing in identification of different lithological units in the Central High Atlas.     

Establishment criteria,routing algorithms and probability of use of inter-satellite links in mixed navigation constellations

In this paper, the establishment criteria, routing algorithm and the probability of use of ISLs (inter-satellite links) in the mixed navigation constellation of GEO satellites, IGSO satellites and MEO satellites are analyzed. Firstly, the general criteria of ISL establishment in mixed navigation constellation are proposed from the perspective of geometry, and the influences of these criteria on routing algorithms and the probability of use of ISLs are discussed. Then, from the perspective of autonomous orbit determination, the routing algorithm in mixed navigation constellation is designed. Thirdly, a stochastic study of ISLs load in mixed navigation constellation is proposed, and the formulae of probability of use of ISLs are given. Finally, in the simulation, the establishment criteria, routing algorithm and the probability of use of ISLs in a specific mixed navigation constellation of 3GEO + 3IGSO + 24MEO are discussed in detail. The findings of this paper provide a basis for the ISL establishment and routing algorithm, and offer the quantitative indicators for the use of ISL in the mixed navigation constellation.     

Planetary protection issues of private endeavours in research,exploration, and human access to space: An environmental economics approach to forward contamination

In light of the rapidly growing New Space Economy, the landscape of space exploration and development activities will certainly become much more complicated year by year. Relevant commercial space actors have already emerged, pushing the boundaries of entrepreneurial space ventures beyond the Earth-oriented upstream and downstream market segments and opening up the path towards the novel segments of space exploration, space resources utilization, and space research. Planetary protection is usually defined as a set of guidelines concerning the avoidance of bidirectional biological material exchange between the Earth and other celestial bodies. Recent success stories of established and new-entrant NewSpace actors, although posing no realistic planetary protection threat at present, clearly indicate that serious work needs to be done in order for the relevant guidelines to keep up with the rapid advances of the technology development cycles that occur within NewSpace companies. This need may become even more urgent, as space entrepreneurs acquire and develop the resources and competencies to target the currently underserved market segments of space research, exploration, and utilization. As of now, these capabilities were maintained solely by public space agencies; thus, all planetary protection priorities, strategies, and responsibilities were discussed, agreed-upon, and delegated for implementation among national and international working groups of public stakeholders. Although top-down regulations can be effective in controlling the quality and conformity of the deliverables of private subcontractors to public contractors, international planetary protection frameworks might need to evolve even beyond such unmet public-private interaction and partnership models. For this reason, this study did not focus on the legal and political issues of mandating NewSpace actors to adhere to planetary protection guidelines; rather, drawing from the field of sustainable development on Earth, an environmental economics approach was followed, with the goal of viewing the relationship between planetary protection and private space exploration and development as another “tragedy of the commons” problem that must be settled accordingly. After the problem’s framing, i.e. the conceptual presentation and synthesis of four extraterrestrial non-excludable goods, the initial approach of their total economic value, and the negative externalities of their exploitation, a discussion of the forward contamination mitigation costs was conducted. Drawing from the literature and using examples from both the terrestrial and aerospace sectors, a pre-emptive move was suggested: the establishment of a global industry consortium for the pre-competitive collaboration in forward contamination mitigation technologies, centered on an international planetary protection analogue program and its respective testbed facility.     

Ballooning perturbations in the inner magnetosphere of the Earth: Spectrum,stability and eigenmode analysis

We investigate the generation of ballooning perturbations in the inner magnetosphere of the Earth in the dipole model of the geomagnetic field taking into account ionospheric boundary conditions. The ionosphere is considered as a thin layer with finite conductivity. The eigenmode spectrum is discrete and consists of Alfvén, slow magnetosonic, flute and incompressible modes. Their interaction depends on ionospheric conductivity. The decay rate is small in noon and night sectors and large in dawn and dusk sectors. The lowest stability threshold α/γ ≈ 4.25 is determined by flute modes.     

Effects of space flight exposure on cell growth,tumorigenicity and gene expression in cancer cells

It is well recognized that harsh outer space environment, consisting of microgravity and radiation, poses significant health risks for human cells. To investigate potential effects of the space environment exposure on cancer cells we examined the biological changes in Caski cells carried by the “Shen Zhou IV” spaceship. After exposure for 7 days in spaceflight, 1440 survival subclonal cell lines were established and 4 cell lines were screened. 44F10 and 17E3 were selected because of their increased cell proliferation and tumorigenesis, while 48A9 and 31F2 had slower cytological events. Experiments with cell proliferation assay, flow cytometry, soft agar assay, tumorigenesis assay and DNA microarray analysis have shown that selected cell lines presented multiple biological changes in cell morphology, cell growth, tumorigenicity and gene expression. These results suggest that space environment exposure can make significant biological impact on cancer cells and provide an entry point to find the immunological target of tumorigenesis.     

Low light intensity effects on the growth,photosynthetic characteristics,antioxidant capacity,yield and quality of wheat (Triticum aestivum L.) at different growth stages in BLSS

Minimizing energy consumption and maximizing crop productivity are major challenges to growing plants in Bioregenerative Life Support System (BLSS) for future long-term space mission. As a primary source of energy, light is one of the most important environmental factors for plant growth. The purpose of this study is to investigate the effects of low light intensity at different stages on growth, pigment composition, photosynthetic efficiency, biological production and antioxidant defence systems of wheat (Triticum aestivum L.) cultivars during ontogenesis. Experiments were divided into 3 intensity-controlled stages according to growth period (a total of 65 days): seedling stage (first 20 days), heading and flowering stage (middle 30 days) and grain filling stage (last 15 days). Initial light condition of the control was 420 μmol m⁻² s⁻¹ and the light intensity increased with the growth of wheat plants. The light intensities of group I and II at the first stage and the last stage were adjusted to the half level of the control respectively. For group III, the first and the last stage were both adjusted to half level of the control. During the middle 30 days, all treatments were kept the same intensity. The results indicated that low-light treatment at seedling stage, biomass, nutritional contents, components of inedible biomass and healthy index (including peroxidase (POD) activity, malondialdehyde (MDA) and proline content) of wheat plants have no significant difference to the control. Furthermore, unit kilojoule yield of group I reached 0.591 × 10⁻³ g/kJ and induced the highest energy efficiency. However, low-light treatment at grain filling stage affected the final production significantly.     

Coronal spectroscopy: Probing sources of slow solar wind in active regions,and the early phases of solar flares

Coronal spectroscopy has pushed forward the understanding of physical processes in all phenomena on the Sun. In this review we concentrate specifically on plasma parameters measured in sources of the slow solar wind in active regions and the early phases of solar flares. These topics are a key part of the science goals of the Solar Orbiter mission (Müller et al., 2020) which has been designed to probe what drives the solar wind and solar transients that fill the heliosphere.Active regions, outside of flaring, have general characteristics that include closed loops showing red-shifted (down-flowing plasma), and the edges of the active regions showing blue-shifted (upflowing plasma). Constraining and understanding the evolution, behaviour and cause of the flows has been developed in the past years and are summarised. Of particular importance is the upflowing plasma which, in some cases, can contribute to the slow solar wind, and this review concentrates on recent results on this topic.The early phases of solar flares and their energy sources are not yet fully understood. For decades, there has been a huge interest in pin-pointing the trigger of a solar flare. Coronal spectroscopy has revealed small-scale dynamics that occurs tens of minutes before the flare begins. The understanding of the trigger is key to improving flare predictions in the future, as well as understanding the physical processes.Finally we look to the future of coronal spectroscopy, with new instruments and methodologies being developed that build on the current knowledge, and will improve significantly our physical understanding of processes at all scales on the Sun.     

Symmetry,reduction and relative equilibria of a rigid body in the J2 problem

The J₂ problem is an important problem in celestial mechanics, orbital dynamics and orbital design of spacecraft, as non-spherical mass distribution of the celestial body is taken into account. In this paper, the J₂ problem is generalized to the motion of a rigid body in a J₂ gravitational field. The relative equilibria are studied by using geometric mechanics. A Poisson reduction process is carried out by means of the symmetry. Non-canonical Hamiltonian structure and equations of motion of the reduced system are obtained. The basic geometrical properties of the relative equilibria are given through some analyses on the equilibrium conditions. Then we restrict to the zeroth and second-order approximations of the gravitational potential. Under these approximations, the existence and detailed properties of the relative equilibria are investigated. The orbit–rotation coupling of the rigid body is discussed. It is found that under the second-order approximation, there exists a classical type of relative equilibria except when the rigid body is near the surface of the central body and the central body is very elongated. Another non-classical type of relative equilibria can exist when the central body is elongated enough and has a low average density. The non-classical type of relative equilibria in our paper is distinct from the non-Lagrangian relative equilibria in the spherically-simplified Full Two Body Problem, which cannot exist under the second-order approximation. Our results also extend the previous results on the classical type of relative equilibria in the spherically-simplified Full Two Body Problem by taking into account the oblateness of the primary body. The results on relative equilibria are useful for studies on the motion of many natural satellites, whose motion are close to the relative equilibria.     

Using vegetation indices and texture measures to estimate vegetation fractional coverage (VFC) of planted and natural forests in Nanjing city,China

Vegetation fractional coverage (VFC) is an important vegetation parameter affecting exchanges of carbon, water, energy between the atmosphere and surface. In this study, the applicability of tonal and texture measures calculated using an IKONOS_2 image in retrieving VFC of forests was investigated in the urban area of Nanjing city, China. Four spectral vegetation indices (VI) and six texture measures (TEX) were related to VFCs acquired from in situ measurements. Models for estimating VFC based on VIs or/and TEXs were established and validated for planted low broad-leaf forest plots (PLB), planted mature forest plots (PMF), natural broad-leaf forest plots (NBF), and all forest plots (ALLv), respectively. The results show that high spatial resolution remote sensing data is applicable to estimate VFC in urban areas, and TEXs may act as effective supplements of vegetation indices (VIs) for the retrieval of VFC. VIs are suitable for VFC estimation of mature forests (such as NBF and PMF) with high vegetation density, and TEXs can yield a more accurate estimate for planted forests (such as PLB and PMF) with regular spatial distribution if they are calculated with proper parameters, such as window size. The combination of VIs and TEXs improve the estimation of VFC if forest types are not previously differentiated. The results can be used as a reference for determining effective spectral or texture parameters in VFC estimation under similar environmental conditions according to vegetation maturity and regularity.     

Feasibility study of LEO,GEO and Molniya orbit based satellite solar power station for some identified sites in India

The analysis of satellite solar power station (SSPS) is carried out for some specified locations (Delhi, Mumbai, Kolkata and Bengaluru) in India and consequently the performance of the system is evaluated for geostationary earth orbit (GEO) based SSPS, low earth orbit (LEO) based SSPS and Molniya (quasi geostationary) orbit based SSPS for sites located at different latitudes. The analysis of power; received energy over a year and weight of the rectenna array for the same beam intensity showed varied results for Molniya orbit based SSPS, LEO based SSPS and GEO based SSPS. The power delivered by the LEO SSPS was highest which indicated that this SSPS may be efficient for the short term power requirement. However, it is observed from the results of the energy received over a year that the GEO based system is suitable for base load power plant as it is capable of delivering constant energy through out a year. Further, the weight of the rectenna and hence the space required for ground station for same power output is smallest for Molniya orbit based system for a range of rectenna array radius considered. It is thus envisaged that the Molniya orbit based system would be a better choice for commercial use of SSPS. These findings may help for judicious selection of satellite orbit and ground station location for placing the satellite for SSPS for various applications.     

Evaluation of SARAL/AltiKa performance using GNSS/IMU equipped buoy in Sajafi,Imam Hassan and Kangan Ports

Performance of SARAL/AltiKa mission has been evaluated within 2016 altimeter calibration/validation framework in Persian Gulf through three campaigns conducted in the offshore waters of Sajafi, Imam Hassan and Kangan Ports, while the altimeter overflew the passes 470, 111 and 25 on 13 Feb, 7 March and 17 June 2016, respectively. As the preparation, a lightweight buoy was equipped with a GNSS receiver/choke-ring antenna and a MEMS-based IMU to measure independent datasets in the field operations. To obtain accurate sea surface height (SSH) time series, the offset of the onboard antenna from the equilibrium sea level was predetermined through surveying operations as the buoy was deploying in the onshore waters of Kangan Port. Accordingly, the double-difference carrier phase observations have been processed via the Bernese GPS Software v. 5.0 so as to provide the GNSS-derived time series at the comparison points of the calibration campaigns, once the disturbing effects due to the platform tilt and heave have been eliminated. Owing to comparing of the SSH time series and the associating altimetry 1?Hz GDR-T datasets, the calibration/validation of the SARAL/AltiKa has been performed in the both cases of radiometer and ECMWF wet troposphere corrections so as to identify potential land contamination. An agreement of the present findings in comparison with those attained in other international calibrations sites confirms the promising feasibility of Persian Gulf as a new dedicated site for calibration/validation of ongoing and future altimetry missions.     

Improvements in and actual performance of the Plant Experiment Unit onboard Kibo,the Japanese experiment module on the international space station

In 2004, Japan Aerospace Exploration Agency developed the engineered model of the Plant Experiment Unit and the Cell Biology Experiment Facility. The Plant Experiment Unit was designed to be installed in the Cell Biology Experiment Facility and to support the seed-to-seed life cycle experiment of Arabidopsis plants in space in the project named Space Seed. Ground-based experiments to test the Plant Experiment Unit showed that the unit needed further improvement of a system to control the water content of a seedbed using an infrared moisture analyzer and that it was difficult to keep the relative humidity inside the Plant Experiment Unit between 70 and 80% because the Cell Biology Experiment Facility had neither a ventilation system nor a dehumidifying system. Therefore, excess moisture inside the Cell Biology Experiment Facility was removed with desiccant bags containing calcium chloride. Eight flight models of the Plant Experiment Unit in which dry Arabidopsis seeds were fixed to the seedbed with gum arabic were launched to the International Space Station in the space shuttle STS-128 (17A) on August 28, 2009. Plant Experiment Unit were installed in the Cell Biology Experiment Facility with desiccant boxes, and then the Space Seed experiment was started in the Japanese Experiment Module, named Kibo, which was part of the International Space Station, on September 10, 2009 by watering the seedbed and terminated 2 months later on November 11, 2009. On April 19, 2010, the Arabidopsis plants harvested in Kibo were retrieved and brought back to Earth by the space shuttle mission STS-131 (19A). The present paper describes the Space Seed experiment with particular reference to the development of the Plant Experiment Unit and its actual performance in Kibo onboard the International Space Station. Downlinked images from Kibo showed that the seeds had started germinating 3 days after the initial watering. The plants continued growing, producing rosette leaves, inflorescence stems, flowers, and fruits in the Plant Experiment Unit. In addition, the senescence of rosette leaves was found to be delayed in microgravity.     

Langley method applied in study of aerosol optical depth in the Brazilian semiarid region using 500, 670 and 870 nm bands for sun photometer calibration

Due to the high costs of commercial monitoring instruments, a portable sun photometer was developed at INPE/CRN laboratories, operating in four bands, with two bands in the visible spectrum and two in near infrared. The instrument calibration process is performed by applying the classical Langley method. Application of the Langley’s methodology requires a site with high optical stability during the measurements, which is usually found in high altitudes. However, far from being an ideal site, Harrison et al. (1994) report success with applying the Langley method to some data for a site in Boulder, Colorado. Recently, Liu et al. (2011) show that low elevation sites, far away from urban and industrial centers can provide a stable optical depth, similar to high altitudes. In this study we investigated the feasibility of applying the methodology in the semiarid region of northeastern Brazil, far away from pollution areas with low altitudes, for sun photometer calibration. We investigated optical depth stability using two periods of measurements in the year during dry season in austral summer. The first one was in December when the native vegetation naturally dries, losing all its leaves and the second one was in September in the middle of the dry season when the vegetation is still with leaves. The data were distributed during four days in December 2012 and four days in September 2013 totaling eleven half days of collections between mornings and afternoons and by means of fitted line to the data V₀ values were found. Despite the high correlation between the collected data and the fitted line, the study showed a variation between the values of V₀ greater than allowed for sun photometer calibration. The lowest V₀ variation reached in this experiment with values lower than 3% for the bands 500, 670 and 870 nm are displayed in tables. The results indicate that the site needs to be better characterized with studies in more favorable periods, soon after the rainy season.     

Thermal properties of molten InSb,GaSb, and InxGa1−xSb alloy semiconductor materials in preparation for crystal growth experiments on the international space station

The thermal properties of InSb, GaSb and In_xGa_1−xSb, such as the viscosity, wetting property, and evaporation rate, were investigated in preparation for the crystal growth experiment on the International Space Station (ISS). The viscosity of InGaSb, which is an essential property for numerical modeling of crystal growth, was evaluated. In addition, the wetting properties between molten In_xGa_1−xSb and quartz, BN, graphite, and C-103 materials were investigated. The evaporation rate of molten In_xGa_1−xSb was measured to determine the affinity of different sample configurations. From the measurements, it was found that the viscosity of In_xGa_1−xSb was between that of InSb and GaSb. The degree of wetting reaction between molten In_xGa_1−xSb and the C-103 substrate was very high, whereas that between molten In_xGa_1−xSb and quartz, BN, and graphite substrates was very low. The results suggest that BN and graphite can be used as materials to cover InSb and GaSb samples inside a quartz ampoule during the microgravity experiments. In addition, the difference of the evaporation rate of molten In_xGa_1−xSb, GaSb, and InSb was small at low, and large at high temperature.