Rocket berthing to an asteroid: Design problems

The results of research in a process of a probe rocket berthing to an asteroid are presented. Control laws were obtained as solutions of three problems, namely berthing considering transient processes in a rocket engine, fastest berthing with regard to fuel consumption and berthing in a scheduled time considering fuel consumption. A program trajectory obtained at solving of the first problem is suitable for mathematical modeling of berthing with the feedback control law and stabilization of angular motion. The solutions of the problems are reduced to simple formulas for controlling parameters calculation in the corresponding structures of control laws. The results can be applied in designing promising space vehicles intended for berthing to other space objects.     

Spherical accretion of massive black holes: A model for galactic nuclei

The possibility of explaining the continuous emission of active galactic nuclei in the frame of a model of spherical accretion onto a massive black hole is discussed. Cool inhomogeneities (T 10⁴°K) within the accretion flow could be responsible for the broad line emission if half of the accreting matter is in the dense phase. A crucial test of this hypothesis is the expected correlation between the ratio of the luminosity in lines to the total luminosity and the hardness of the continuous spectrum.     

改进PASTd算法在大型自适应阵中的应用

矩阵特征分解算法中紧缩近似投影子空间跟踪(PASTd)算法在自适应阵波束形成中得到了广泛应用.在对其仿真中发现仅在信噪比较低时该算法才能得到较好的结果.针对这一缺陷,正交近似投影子空间跟踪(OPAST)算法被引伸到PASTd中.改进算法可在不知道信号维数的情况下估算信号的特征向量与特征值,并保证特征向量的正交性,因此具有更好的收敛性能,而算法复杂度基本不变.改进算法与多重信号分类(MUSIC)算法相结合应用于大型自适应阵,可对主瓣及其附近区域的干扰进行抑制,并大大降低MUSIC算法的计算量,对其干扰零点的形成有很强实用价值.     

Space experiments aboard the Lomonosov MSU satellite

At present, the Institute of Nuclear Physics of Moscow State University, in cooperation with other organizations, is preparing space experiments onboard the Lomonosov satellite. The main goal of this mission is to study extreme astrophysical phenomena such as cosmic gamma-ray bursts and ultra-high-energy cosmic rays. These phenomena are associated with the processes occurring in the early universe in very distant astrophysical objects, therefore, they can provide information on the first stages of the evolution of the universe. This paper considers the main characteristics of the scientific equipment aboard the Lomonosov satellite.     

Influence of Trapped Plasma on the Structure of Collisionless Thin Current Sheets

Using both analytical and numerical models of the collisionless anisotropic current sheet generated by the impinging flows of transient ions, we have studied the self-consistent solutions taking the plasma trapped in the sheet into account. It is demonstrated that there exists a limited window in the space of system parameters where self-consistent solutions can exist. When the density of the quasi-trapped plasma is sufficiently large, a redistribution of the total current can be a cause of the sheet decay, when the local current of the trapped particles compensate (totally or in part) the main current in the center and at the edges of the sheet, while the total current generated by ions on the trapped trajectories vanishes.     

Preservation of martian organic and environmental records: final report of the Mars biosignature working group

The Mars Science Laboratory (MSL) has an instrument package capable of making measurements of past and present environmental conditions. The data generated may tell us if Mars is, or ever was, able to support life. However, the knowledge of Mars' past history and the geological processes most likely to preserve a record of that history remain sparse and, in some instances, ambiguous. Physical, chemical, and geological processes relevant to biosignature preservation on Earth, especially under conditions early in its history when microbial life predominated, are also imperfectly known. Here, we present the report of a working group chartered by the Co-Chairs of NASA's MSL Project Science Group, John P. Grotzinger and Michael A. Meyer, to review and evaluate potential for biosignature formation and preservation on Mars. Orbital images confirm that layered rocks achieved kilometer-scale thicknesses in some regions of ancient Mars. Clearly, interplays of sedimentation and erosional processes govern present-day exposures, and our understanding of these processes is incomplete. MSL can document and evaluate patterns of stratigraphic development as well as the sources of layered materials and their subsequent diagenesis. It can also document other potential biosignature repositories such as hydrothermal environments. These capabilities offer an unprecedented opportunity to decipher key aspects of the environmental evolution of Mars' early surface and aspects of the diagenetic processes that have operated since that time. Considering the MSL instrument payload package, we identified the following classes of biosignatures as within the MSL detection window: organism morphologies (cells, body fossils, casts), biofabrics (including microbial mats), diagnostic organic molecules, isotopic signatures, evidence of biomineralization and bioalteration, spatial patterns in chemistry, and biogenic gases. Of these, biogenic organic molecules and biogenic atmospheric gases are considered the most definitive and most readily detectable by MSL.     

火星磁层顶形成和变化的理论研究

考虑太阳风动压与行星电离层中的带电粒子热压及磁压之和平衡,建立了有大气（电离层）的行星磁层顶形成的理论模型,结合卫星对火星的观测数据,对子午面内向日侧火星磁层顶位形进行了数值计算和分析,研究了火星磁层顶位形及其与太阳风动压之间的变化关系．结果认为,火星磁层顶位形与地球磁层顶相似．太阳风动压越大,火星磁层顶越靠近火星;太阳风动压越弱,火星磁层顶越远离火星．根据火星内秉磁矩从古到今逐渐减小的观点,探索了大尺度磁场（内禀磁矩）对火星磁层顶的贡献作用,结果认为大尺度磁场越强,火星磁层顶越远离行星．这对于进一步研究火星磁层的长期演化以及其他行星磁层的位形变化都具有重要的意义．