Numerical Simulation of Ionospheric Disturbances Generated by the Chelyabinsk and Tunguska Space Body Impacts

Numerical simulation of atmospheric disturbances during the first hours after the Chelyabinsk and Tunguska space body impacts has been carried out. The results of detailed calculations, including the stages of destruction, evaporation and deceleration of the cosmic body, the generation of atmospheric disturbances and their propagation over distances of thousands of kilometers, have been compared with the results of spherical explosions with energy equal to the kinetic energy of meteoroids. It has been shown that in the case of the Chelyabinsk meteorite, an explosive analogy provides acceptable dimensions of the perturbed region and the perturbation amplitude. With a more powerful Tunguska fall, the resulting atmospheric flow is very different from the explosive one; an atmospheric plume emerges that releases matter from the meteoric trace to an altitude of the order of a thousand kilometers.     

Analysis of the Space Debris Impacts Risk on the International Space Station

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.     

The Impact Effect Callculator of Celestial Body Impacts to the Earth: The Constructor of Hazardous Orbits

Quick assessment of hazardous effects from impacts of large celestial bodies is achieved through the development of a new consequence calculator. A distinctive feature of this calculator is a new block, the Hazardous-Orbit Constructor, which simulates the conditions of entry of a celestial body into the Earth’s atmosphere and determines the orbital parameters of the body based on given atmospheric entry conditions. This block is used to simulate the atmospheric entry conditions of known asteroids and meteoroids and to determine the orbital parameters of known bolides leading to meteorite fall events. For the case of asteroid 2008 TC3 and the P?ibram meteorite, it is shown that within the potential impact area of the celestial body, the atmospheric entry angle may vary considerably.     

空间飞行器远尾区内等离子体与场的相互作用

从理论上得到一组在考虑非静态极限下描述空间飞行器远尾区内等离子体与场之间的非稳态非线性相互作用耦合方程，并对其进行数值解，通过来用数值模拟计算方法，表明由于高频包络场的调制不稳定性，会产生密度空腔和电磁孤波，这对探测隐身飞行器有很重要的意义．     

The Infrared Space Observatory

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.     

NEOs and Impacts: The Galactic Connection

The orbit of the solar system within the Galaxy is subject both to adiabatic tidal forces and to irregular buffeting caused by encounters with molecular clouds and spiral arms, while the long-period comet flux varies with the differential of these forces. Quasi-periodic episodes of Earth bombardment by Oort cloud comets are expected, with the half-period of the solar vertical oscillations being prominent. Various terrestrial datasets are examined and show evidence of a periodicity ∼27±1 Myr at a confidence level ≳ 99.5%, consistently with the expectations. Bombardment episodes thus appear to exert a controlling influence on global terrestrial processes. Conversely, the long-term terrestrial record provides an empirical constraint on the source regions of NEOs as well as on the dark matter content of the Galactic disc. During such episodes, climatic effects due to stratospheric dusting by very large comets are likely to be a major factor in geological and biological change. This revised version was published online in July 2006 with corrections to the Cover Date.     

Satellite Orbital Precessions Caused by the Octupolar Mass Moment of a Non-Spherical Body Arbitrarily Oriented in Space

I consider a satellite moving around a non-spherical body of mass M and equatorial radius R, and calculate its orbital precessions caused by the body’s octupolar mass moment J ₄. I consider only the effects averaged over one orbital period T of the satellite. I give exact formulas, not restricted to any special values of either the eccentricity e or the inclination i of the satellite’s orbit. I do not assume any preferential orientation for the body’s spin axis ${\boldsymbol{\hat{{\mathbf{k}}}}}$ because in many cases of potential interest (exoplanets, neutron stars, black holes) it is poorly known or unknown at all.     

Life In Space: An Introduction To Space Life Sciences And The International Space Station

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.     

The Next Generation Space Telescope

The design life time of the Hubble Space Telescope will nominally end in 2005. Even though it might be possible to extend the operational life beyond that date it is evident that a successor to Hubble must be planned for now. Based on the report ‘HST and Beyond’ (Dressler 1996)) and aligned with the NASA ‘Origins’ program a study has been initiated to explore options for a telescope with an aperture of larger than 4 meters and possibly as large as 8 meters, optimized for the near infrared (≈ 1-5 micron) to be placed in an orbit far from Earth. The study started in December 1995 and has been proceeding with considerable momentum. At the current time three studies have been completed (NASA in-house, TRW, and Lockheed), which are being used to explore technological and programmatic challenges. The studies are to be merged. It is impressive to see what can be done with existing technology and within the capabilities of existing organizational arrangements. The goal is to complete the study within one year with the goal of entering into phase A as soon as possible. Formal agreements between ESA and NASA will have to be negotiated if Europe is to play a meaningful role in this exercise. Without such agreements, it is clear that European astronomers will not have access to the NGST in the way that they currently enjoy the opportunities provided by the HST. This revised version was published online in July 2006 with corrections to the Cover Date.     

高能粒子流对地震活动的可能调制

把地球作为一个开放系统，本文分析了不同地域范围的地震活动和太阳活动的关系，发现不同地域的地震活动也存在着一个大约１１年的周期，这个周期可能与太阳活动的１１年左右周期有关，但地震周期的峰值对应于太阳活动的下降段。它们的关系是负相关关系。本文进一步着重分析了地震活动与高速太阳风粒子流和宇宙线高能粒子流的关系，发现它们之间存在着一个信度水平很高的正相关。这样，我们可以推测太阳活动可能是通过调制到达地球的高能粒子流进而调制地震活动的。     

苏梅克－利维9号彗星撞击木星事件的光学观测

本文给出了１９９４年７月１７日至２２日，彗星碰撞期间，福州和乌鲁木齐两个观测点所取得的部分光学观测资料。     

空间VLBI研究的现状和未来

空间ＶＬＢＩ卫星ＶＳＯＰ／ＨＡＬＣＡ是日本宇航科学研究所（ＩＳＡＳ）的飞行任务,已经在１９９７年２月升空。它拥有８ｍ直径的射电望远镜,远地点达２２０００ｋｍ。和地面的射电望远镜联合观测（干涉观测）,其最高分辨率比地面ＶＬＢＩ提高了３倍。该项空间ＶＬＢＩ观测由ＮＳＡＳ的地面跟踪站支持。第一批ＶＬＢＩ图像已经在因特网上发表。ＲａｄｉｏＡｓｔｒｏｎ项目由俄罗斯科学院列别捷夫物理研究所天文空间中心（ＡＳＣ     

Reduction of The Stellar Three – Body Problem

The stellar problem of three bodies is studied. A Lie transform is used to eliminate the short and intermediate periodic terms from Harrington's Hamiltonian. The resulting system is a one of two degrees of freedom whose further reduction requires recourse to numerical procedures. This revised version was published online in July 2006 with corrections to the Cover Date.     

High-Energy Astronomy From The International Space Station

The European Space Agency, ESA, is currently studying 3 high-energy astronomy missions that use the International Space Station (ISS). These are Lobster-ISS, an all-sky imaging X-ray monitor, the Extreme Universe Space Observatory (EUSO) which will study the highest energy cosmic rays by using the Earth's atmosphere as a giant detector and XEUS — the X-ray Evolving Universe Spectroscopy Mission, a potential successor to ESA's XMM-Newton X-ray observatory. These first 2 missions will he attached to the external platforms on the Columbus module, while XEUS will visit the ISS to attach additional X-ray mirrors to enlarge the original 4.5 m diameter mirrors to the 10 m diameter required to observed redshifted iron lines from massive black holes in the early Universe. This revised version was published online in July 2006 with corrections to the Cover Date.     

Physics and Chemistry of Impacts

Earth, Moon, and Planets -     

电离层延时对低轨卫星频率传递的影响分析

利用低轨卫星,对受干扰区域的卫星导航接收机进行频率传递,是提升其性能的一种有效手段.而电离层延时误差是影响传递效果的重要因素.对基于低轨卫星的频率传递应用背景进行了介绍,分析了其基本原理,并着重分析了电离层延时的存在对频率传递的影响,提出利用站间差历元差的方法对电离层延时进行修正.最后,通过仿真对理论分析进行了验证.结果表明,通过站间差历元差的手段,对当前电离层变化值进行求解与预测,可以将电离层延时误差的变化控制在一定范围,满足频率传递的要求.     

银河系中球状星团的空间运动

球状星团是银河系中最古老的天体类型之一,其累积光度很大,是银晕中重要的示踪天体。已以发现的银河系球状星团有１４０多个,其中１２０个银心距Ｒ〈４０Ｋｐｃ的星团已被准确地测定了视向速度。根据结数据以及球状星团金属度的统计分析,可以把球状星团次系再进一步分成某些不同的族群。目前已经测定过绝对自行的球状星团只有３８个,尽管这些自行的精度比视向速度和距离的精度差很多,然而,由此可以得出三维的空间速度,在统计     

The Efficiency of the Magnetic Acceleration in Relativistic Jets

Using steady, axisymmetric, ideal magnetohydrodynamics (MHD) we analyze relativistic outflows by means of examining the momentum equation along the flow and in the transfield direction. We argue that the asymptotic Lorentz factor is γ_∞ ～ μ ? σ _M , and the asymptotic value of the Poynting-to-matter energy flux ratio—the so-called σ function—is given by σ_∞/(1 + σ_∞) ～ σ _M /μ, where σ _M is the Michel's magnetization parameter and μc ² the total energy-to-mass flux ratio. We discuss how these values depend on the conditions near the origin of the flow. By employing self-similar solutions we verify the above result, and show that a Poynting-dominated flow near the source reaches equipartition between Poynting and matter energy fluxes, or even becomes matter-dominated, depending on the value of σ _M /μ.