Improved interpretation of solar wind ion measurements via high-resolution magnetic field data

The Wind   spacecraft’s Faraday cups (FC) continue to produce high-quality, in situ observations of thermal protons (i.e., ionized hydrogen) and α$\alpha$-particles (i.e., fully ionized helium) in the solar wind. By fitting a Wind/FC ion spectrum with a model velocity distribution function (VDF) for each particle species, values for density, bulk velocity, and temperature can be inferred. Incorporating measurements of the background magnetic field from the Wind Magnetic Field Investigation (MFI) allows perpendicular and parallel temperature components to be separated. Prior implementations of this analysis averaged the higher-cadence Wind/MFI measurements to match that of the Wind/FC ion spectra. However, this article summarizes recent and extensive revisions to the analysis software that, among other things, eliminate such averaging and thereby account for variations in the direction of the magnetic field over the time taken to measure the ions. A statistical comparison reveals that the old version consistently underestimates the temperature anisotropy of ion VDF’s: averaging over fluctuations in the magnetic field essentially blurs the perpendicular and parallel temperature components, which makes the plasma seem artificially more isotropic. The new version not only provides a more accurate dataset of ion parameters (which is well suited to the study of microkinetic phenomena), it also demonstrates a novel technique for jointly processing particle and field data. Such methods are crucial to heliophysics as wave-particle interactions are increasingly seen as playing an important role in the dynamics of the solar wind and similar space plasmas.     

航空航天复合材料应用的最新进展

文章介绍了先进复合材料的最新进展情况,内容包括用于最新复合材料体系的各种增强纤维、树脂基体,及复合材料结构设计的一些新概念。重点介绍了低成本和高效的制造技术。复合材料重要结构件的制造技术在不断改进,制造出的部件不仅精度和强度更高,而且更显成本效益。文章还介绍了航空航天领域一些新研发的复合材料结构件。     

Investigation of the motion of (99942) apophis asteroid using the SKIF cyberia multiprocessor computing system

We present the results of investigation of the dynamics of (99942) Apophis asteroid, which will undergo a very close encounter with the Earth on April 13, 2029. The region of possible motions of the asteroid is considered on the time interval (2004, 2040). In addition, it is shown that an increase of the observational interval (2004, 2006) until 2008 allowed us to reduce significantly the area of possible motions. All investigations were performed by numerical methods with the help of algorithms and software developed by us in the environment of parallel programming using the SKIF Cyberia multiprocessor computer of the Tomsk State University.     

Optimization of Low-Thrust Interplanetary Transfers

A method for approximate analytical optimization of low-thrust transfers, described in [1] and based on linearization of the equations of motion, is considered. A more precise method of reducing the errors due to linearization is suggested. The method of optimization is generalized for the case of a mission to several celestial bodies.     

Collision Risk Mitigation in Geostationary Orbit

The short- and long-term effects of spacecraft explosions, as a function of the end-of-life re-orbit altitude above the geostationary orbit (GEO), were analyzed in terms of their additional contribution to the debris flux in the GEO ring. The simulated debris clouds were propagated for 72yrs, taking into account all the relevant orbital perturbations.The results obtained show that 6–7 additional explosions in GEO would be sufficient, in the long term, to double the current collision risk with sizable objects in GEO. Unfortunately, even if spacecraft were to re-orbit between 300 and 500km above GEO, this would not significantly improve the situation. In fact, an altitude increase of at least 2000km would have to be adopted to reduce by one order of magnitude the long-term risk of collision among geostationary satellites and explosion fragments. The optimal debris mitigation strategy should be a compromise between the reliability and effectiveness of spacecraft end-of-life passivation, the re-orbit altitude and the acceptable debris background in the GEO ring. However, for as long as the re-orbit altitudes currently used are less than 500km above GEO, new spacecraft explosions must be avoided in order to preserve the geostationary environment over the long term.     

Physical Calibrations of the FREND Instrument Installed Onboard TGO Martian Orbiter

Cosmic Research - The article presents results of ground calibrations of the FREND neutron telescope installed onboard the TGO spacecraft of the Russian-European ExoMars project. The main goal of...     

Spectral Characteristics of Self-Emission from Electric Thrusters with Closed Electron Drift in the Radio-Frequency Band for Various Propellants

Cosmic Research - We have considered procedure and results of the experimental study for spectral characteristics of self emission from laboratory models of electric thrusters with closed electron...     

SSA: Where does Europe stand now?

With the growing need for monitoring and awareness of all the objects in space (including debris) now recognized, the types of effort required towards this end are discussed, with the emphasis on European activities. A number of European documents acknowledging the problem are cited and initiatives to promote space situational awareness (SSA) are examined. While there is currently no provision in the EU budget beyond 2013 for protecting ground and space assets from space environmental threats, an encouraging degree of bilateral cooperation between member states suggests that an SSA capability is emerging in Europe.     

The CPR approach to space sustainability: Commentaries on Weeden and Chow

Space sustainability is emerging as a core element of national policy and international initiatives. At this time, however, a coherent strategy and supporting policies have not been developed. To initiate a conversation to develop such a strategy, the authors have applied the principles developed by Elinor Ostrom for terrestrial common-pool resource (CPR) governance to near-Earth orbit in space. A concern arises as to whether Ostrom's eight principles are a good “fit” for application to space CPR because of the unique physical characteristics of space and the legal underpinnings of our presence there. This commentary will address selected issues raised by Weeden and Chow, and suggest alternative ways to approach near-Earth orbit sustainability.     

Economic methods of improving efficient use of the orbit/spectrum resource by satellite systems

Satellite systems continue to play an important role in the booming market for communication and broadcasting services, driving up demand for use of the orbit/spectrum resource. Studies are required to address the problem of orbit capacity and find ways of making more efficient use of it, to avoid a situation in which there is not enough orbit/spectrum resource to cater for the development of future satellite networks. It is argued that, as far as satellite networks are concerned, the current international regulatory regime governing the use of the spectrum has significant shortcomings, which have a cost, in terms of resources and time, and make investment in satellite projects less attractive. An approach is proposed for improving efficiency of the use of the orbit/spectrum through the introduction of economic methods, to supplement the existing technical and regulatory regime. A spectrum pricing method is proposed for satellite communication systems.