共查询到20条相似文献，搜索用时 15 毫秒
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Öpik's analytical expressions relate in a simple way the semimajor axis, eccentricity and inclination of the projectile orbit to the magnitude and direction of the relative velocity vector at impact on a given target on circular orbit. These interesting quantities, along with the impact probability of any given projectile, can be all represented on a suitable projection giving a comprehensive picture of the impact risk on the selected target. By means of this theory a complete analysis of the impact risk on the International Space Station (ISS) is performed. It is found that the large majority of the debris population is on orbits such that a correlation exists between their impact velocity on the ISS and the angle between the velocity vector of the impactor and that of the ISS. The impactor population also is separated in terms of nature of the projectiles, with most of the low-medium velocity ones being particles related to solid rocket motor slag condensates. On the other hand, the highest velocity projectiles are composed mainly by fragments of past in-orbit explosions.The flux of projectiles on the ISS has been calculated for the planned operative lifetime of the Station, by assuming a realistic scenario of the future debris environment evolution and the actual planned altitude profile for the ISS mission. There is a factor 2-3 variation of the flux due to the changing ISS altitude. The most dangerous part of the mission appears to be the central one, when the ISS will orbit at about 450 km above the Earth. 相似文献
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Yan-Chuan Cai Jun Pan Purple Mountain Observatory Chinese Academy of Sciences Nanjing National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2007,7(1):51-62
1 INTRODUCTION Large redshift surveys of galaxies provide us with distances estimated from measured redshifts to complete our three-dimensional topography of the visible universe. However, due to the peculiar velocities of galax- ies, the inferred redshif… 相似文献
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空间碎片光学观测中若干问题研究 总被引：2，自引：0，他引：2
<正>地基光学观测是探测空间碎片的重要手段.本文从目标搜索方案的制定、目标质心提取、目标精密定位以及目标关联4方面入手,研究提升设备探测能力、提高目标观测精度的方法.首先,为了满足对GEO(Geosynchronous Orbit,地球同步轨道)空间碎片探测的要求,克服长时间曝光CCD像元饱和溢出的问题,使用多帧连续曝光图像叠加的方法,增加图像的宽容度,同时保证系统的探测能力.实验表明,叠加10帧连续图像,有效消除了像元饱和的情况,提升目标信噪比约3.2倍,提升探测能力约2.5 mag,使用底片常数的均值计算目标位置,精度符合要求.使用星像几何形态检测 相似文献
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Life In Space: An Introduction To Space Life Sciences And The International Space Station 总被引：1，自引：0，他引：1
The impact of the space environment upon living organisms is profound. Its effects range from alterations in sub-cellular
processes to changes in the structure and function of whole organ systems. As the number of astronaut and cosmonaut crews
flown in space has grown, so to has our understanding of the effects of the space environment upon biological systems. There
are many parallels between the physiology of space flight and terrestrial disease processes, and the response of astronaut
crews themselves to long-duration space deployment is therefore of central interest.
In the next 15 years the International Space Station (ISS) will serve as a permanently manned dedicated life and physical
sciences platform for the further investigation of these phenomena. The European Space Agency's Columbus module will hold
the bulk of the ISS life science capability and, in combination with NASA's Human Research Facility (HRF) will accommodate
the rack mounted experimental apparatus. The programme of experimentation will include efforts in fundamental biology, human
physiology, behavioural science and space biomedical research.
In the four decades since Yuri Gagarin first orbited the Earth, space life science has emerged as a field of study in its
own right. The ISS takes us into the next era of human space exploration, and it is hoped that its programme of research will
yield new insights, novel therapeutic interventions, and improved biotechnology for terrestrial application.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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C. Plainaki A. Milillo A. Mura A.M. Di Lellis M.E. Palumbo 《Planetary and Space Science》2009,57(3):384-392
The ion-sputtering (IS) process is active in many planetary environments in the solar system where plasma precipitates directly on the surface (for instance, Mercury, Moon and Europa). In particular, solar wind sputtering is one of the most important agents for the surface erosion of a near-Earth object (NEO), acting together with other surface release processes, such as photon stimulated desorption (PSD), thermal desorption (TD) and micrometeoroid impact vaporization (MIV). The energy distribution of the IS-released neutrals peaks at a few eVs and extends up to hundreds of eVs. Since all other release processes produce particles of lower energies, the presence of neutral atoms in the energy range above 10 eV and below a few keVs (sputtered high-energy atoms (SHEA)) identifies the IS process. SHEA easily escape from the NEO, due to NEO's extremely weak gravity. Detection and analysis of SHEA will give important information on surface-loss processes as well as on surface elemental composition. The investigation of the active release processes, as a function of the external conditions and the NEO surface properties, is crucial for obtaining a clear view of the body's present loss rate as well as for getting clues on its evolution, which depends significantly on space weather.In this work, an attempt to analyze processes that take place on the surface of these small airless bodies, as a result of their exposure to the space environment, has been realized. For this reason, a new space weathering model (space weathering on NEO-SPAWN) is presented. Moreover, an instrument concept of a neutral-particle analyzer specifically designed for the measurement of neutral density and the detection of SHEA from a NEO is proposed. 相似文献
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By applying our understanding of lunar space weathering processes, we can predict how space weathering will effect the soil properties on Mercury. In particular, the extreme temperature range on Mercury may result in latitudinal variations in the size distribution of npFe0, and therefore the spectral properties of the soil. 相似文献
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The effects of changes in the space environment on the ISOPHOT photoconductivedetectors over the whole ISO mission were studied using the complete setof responsivity check measurements taken after the curing of the detectors.We found that the responsivity of the Ge-based, low bias voltage far-infrared detectors (P3, C100, and C200) is sensitive to the conditions of the Space Weather.We present evidence that an increased responsivity level (20% – 50%) after curing of the detectors is linked to the onset of geomagnetic storms. TheSi-based, high bias voltage detectors P1, P2 and PHT–SS show only small changesin their responsivity. An exception is the PHT–SL array which shows a similar,but less pronounced behaviour as the FIR detectors. While these relationshave been demonstrated by our study, a detailed physical understanding is still outstanding. The Space Weather dependent scatter of the responsivity,being the photometric scaling factor (conversion from measured photo currentto inband power on the detector), justifies the observing mode design to include frequent monitoring of its actual level. 相似文献
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The frequency at which a large space telescope's (e.g. JWST's) detector chips are read, or the sample rate, is tightly coupled
to many hardware and operational aspects of the telescope's instrument and data handling elements. In this paper we discuss
many of the drivers and important implications of the sample rate: the data rate to the ground; onboard computer storage,
bandwidth, and speed; the number of A→D chips, and therefore the overall size and power requirements of the analog electronics;
cryocabling requirements; and detector noise and power. We discuss and parametrize these and other elements related to sample
rate. Finally, we discuss the implications of sample rate in the context of achieving the most important science goals under
the constraint of limited cost.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Minoru Oda 《Astrophysics and Space Science》1986,118(1-2):67-70
Japan's two X-ray astronomy satellites, HAKUCHO and TENMA, have been actively in operation leading to deeper understandings of the neutron star physics. Other satellite and balloon projects have been performed under international collaborators.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
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A. Heske 《Astrophysics and Space Science》1997,258(1-2):77-87
The first true infrared observatory in space, ESA's Infrared Space Observatory (ISO), was launched 17 November 1995. Since
one and a half years, it has made more than 15,000 observations with its four versatile instruments: a camera, a photo-polarimeter
and two spectrometers. This paper presents an overview of the satellite, its payload, the operations of the observatory and
gives an outlook of the events to come.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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The design of detector systems for flight applications requires the consideration of a number of issues unique to space instrumentation. Flight detectors must endure hostile radiation environments and thermal extremes. Paramount importance is given to reliability since inflight replacement is at best difficult and usually impossible. Flight detectors are also significant cost and design drivers since they often determine key requirements for flight instruments such as volume, mass, power consumption, heat dissipation and communications budgets. In this paper we describe the primary concerns in developing flight detector systems, and review the challenges posed by future NASA and ESA space science missions for detector development. 相似文献
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以我国嫦娥工程、萤火计划等深空探测计划为背景,通过理论分析、方法研究、软件研发、仿真检验和实测资料解析等,完成了基于VLBI、USB跟踪对欧空局Smart-1环月卫星和火星快车(MEX)卫星,以及我国嫦娥一号(CE-1)、嫦娥二号(CE-2)等卫星的定位归算;在理论模型研究、误差方程建立、法方程条件分析、约束方程选取、仿真数据检验、观测野值规避、参数解算稳定性的保障、实用软件编制和实测资料处理等方面均获得了进展,主要工作包括如下方面: 相似文献