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61.
Linear and circular structures of the Bohemian Massif — Comparison of satellite and geophysical data
J. Dornič N. Šťovíčková 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(11):115-121
Two structural schemes of the Bohemian Massif are presented and compared. The first one is a result of interpretation of various geophysical data and the second one is compiled on the basis of decoding of space imagery from different sources (Kosmos, Landsat etc.). Both schemes have many structural features in common, but there are diversities namely in the hierarchy of directions and regional distribution of linear structures. These problems are discussed in detail. For example, the most impressive system of structures is the NW-SE system in both schemes, whereas the NE-SW is more remarkable in the geophysical scheme; the N-S and the E-W systems are best expressed in the scheme of photolineaments. These facts are due to the genesis, age, development and dynamic characteristics of respective structural systems. The circular structural features namely those of large size are mostly remarkable in space imagery. At present, they are not distinguished genetically but only described regionally. 相似文献
62.
F. Rákóczi E. Kovács 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(4):133-137
A method for the determination of cloud motion vectors is proposed by calculating from METEOSAT images the displacement of characteristic formations in the brightness field. The claculations are made for a sector of the Atlantic Ocean (ψ = 48°?38°N, λ = 24°?12°W). The adaptability of the Soebel operator for such calculations is also shown. The calculated wind vectors are in a good agreement with wind data at 850 mb surface. 相似文献
63.
Since more than 20 years reorbiting of geostationary satellites at the end of their mission is recommended and partially performed to protect the GEO environment. Now a worldwide accepted reorbiting altitude was defined by the Inter-Agency Space Debris Coordination Committee (IADC). Still only one-third of the aging satellites follow this IADC rule. Based on orbital data in the DISCOS database, the situation in the geostationary ring is analyzed. From 878 known objects, 305 are controlled inside their longitude slots, 353 are drifting above, below or through GEO, and 125 are in a libration orbit (status of January 2001). In the last four years (1997–2000) 58 spacecraft reached end-of-life. Twenty of them were reorbited in compliance with the IADC recommendations, 16 were reorbited below this recommendation and 22 were abandoned without any end-of-life disposal manoeuvre. 相似文献
64.
Meteoroids as One of the Sources for Exosphere Formation on Airless Bodies in the Inner Solar System
Janches Diego Berezhnoy Alexey A. Christou Apostolos A. Cremonese Gabriele Hirai Takayuki Horányi Mihály Jasinski Jamie M. Sarantos Menelaos 《Space Science Reviews》2021,217(4):1-4
Space Science Reviews - 相似文献
65.
N. Labrosse P. Heinzel J.-C. Vial T. Kucera S. Parenti S. Gunár B. Schmieder G. Kilper 《Space Science Reviews》2010,151(4):243-332
This review paper outlines background information and covers recent advances made via the analysis of spectra and images of
prominence plasma and the increased sophistication of non-LTE (i.e. when there is a departure from Local Thermodynamic Equilibrium) radiative transfer models. We first describe the spectral
inversion techniques that have been used to infer the plasma parameters important for the general properties of the prominence
plasma in both its cool core and the hotter prominence-corona transition region. We also review studies devoted to the observation
of bulk motions of the prominence plasma and to the determination of prominence mass. However, a simple inversion of spectroscopic
data usually fails when the lines become optically thick at certain wavelengths. Therefore, complex non-LTE models become
necessary. We thus present the basics of non-LTE radiative transfer theory and the associated multi-level radiative transfer
problems. The main results of one- and two-dimensional models of the prominences and their fine-structures are presented.
We then discuss the energy balance in various prominence models. Finally, we outline the outstanding observational and theoretical
questions, and the directions for future progress in our understanding of solar prominences. 相似文献
66.
R.G. Ezquer L.A. Scidá Y. Migoya Orué B. Nava M.A. Cabrera C. Brunini 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(7):1803-1818
Using vertical total electron content (VTEC) measurements obtained from GPS satellite signals the capability of the NeQuick 2 and IRI Plas models to predict VTEC over the low latitude and South American sector is analyzed. In the present work both models were used to calculate VTEC up to the height of GPS satellites. Also, comparisons between the performance of IRI Plas and IRI 2007 have been done. The data correspond to June solstice and September equinox 1999 (high solar activity) and they were obtained at nine stations. The considered latitude range extends from 18.4°N to ?64.7°N and the longitude ranges from 281.3°E to 295.9°E in the South American sector. The greatest discrepancies among model predictions and the measured VTEC are obtained at low latitudes stations placed in the equatorial anomaly region. Underestimations as strong as 40?TECU [1?TECU?=?1016?m?2] can be observed at BOGT station for September equinox, when NeQuick2 model is used. The obtained results also show that: (a) for June solstice, in general the performance of IRI Plas for low latitude stations is better than that of NeQuick2 and, vice versa, for highest latitudes the performance of NeQuick2 is better than that of IRI Plas. For the stations TUCU and SANT both models have good performance; (b) for September equinox the performances of the models do not follow a clearly defined pattern as in the other season. However, it can be seen that for the region placed between the Northern peak and the valley of the equatorial anomaly, in general, the performance of IRI Plas is better than that of NeQuick2 for hours of maximum ionization. From TUCU to the South, the best TEC predictions are given by NeQuick2.The source of the observed deviations of the models has been explored in terms of CCIR foF2 determination in the available ionosonde stations in the region. Discrepancies can be also related to an unrealistic shape of the vertical electron density profile and or an erroneous prediction of the plasmaspheric contribution to the vertical total electron content. Moreover, the results of this study could be suggesting that in the case of NeQuick, the underestimation trend could be due to the lack of a proper plasmaspheric model in its topside representation. In contrast, the plasmaspheric model included in IRI, leads to clear overestimations of GPS derived TEC. 相似文献
67.
Michael C.F. Bazzocchi Juan Miguel Sánchez-Lozano Houman Hakima 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(3):1155-1173
As private companies and government space agencies begin to seriously consider the task of active space debris removal, it is becoming increasingly more important to determine the highest priority objects to deorbit. This work sets forth an approach for prioritization of space debris through the utilization of Multi-Criteria Decision-Making methodologies and fuzzy logic, as well as both quantitative and qualitative criteria. The proposed debris prioritization approach considers various criteria including the orbit, size, mass, pairwise and total collision probabilities, and decay timeframe of each debris object. The means of assigning attributes to each assessment criterion is discussed in detail. To determine the weighting scheme for the criteria, a questionnaire was prepared and shared with experts in the field of space situational awareness. The work examines over two thousand critical debris objects selected from the existing debris catalog with respect to these criteria. The quantified attributes for each debris object are then aggregated through the fuzzy versions of the Analytic Hierarchy Process and the Technique for Order Preference by Similarity to Ideal Solution. The results of the analysis identify high-priority debris objects for removal from Earth-bound orbits. 相似文献
68.
Jan Jurčák Manuel Collados Jorrit Leenaarts Michiel van Noort Rolf Schlichenmaier 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(4):1389-1395
The European Solar Telescope (EST) is a project of a new-generation solar telescope. It has a large aperture of 4?m, which is necessary for achieving high spatial and temporal resolution. The high polarimetric sensitivity of the EST will allow to measure the magnetic field in the solar atmosphere with unprecedented precision. Here, we summarise the recent advancements in the realisation of the EST project regarding the hardware development and the refinement of the science requirements. 相似文献
69.
This paper lists all geostationary and near-geostationary objects contained in ESA's DISCOS database. 相似文献
70.
Anthony R. Yeates Tahar Amari Ioannis Contopoulos Xueshang Feng Duncan H. Mackay Zoran Mikić Thomas Wiegelmann Joseph Hutton Christopher A. Lowder Huw Morgan Gordon Petrie Laurel A. Rachmeler Lisa A. Upton Aurelien Canou Pierre Chopin Cooper Downs Miloslav Druckmüller Jon A. Linker Daniel B. Seaton Tibor Török 《Space Science Reviews》2018,214(5):99
Seven different models are applied to the same problem of simulating the Sun’s coronal magnetic field during the solar eclipse on 2015 March 20. All of the models are non-potential, allowing for free magnetic energy, but the associated electric currents are developed in significantly different ways. This is not a direct comparison of the coronal modelling techniques, in that the different models also use different photospheric boundary conditions, reflecting the range of approaches currently used in the community. Despite the significant differences, the results show broad agreement in the overall magnetic topology. Among those models with significant volume currents in much of the corona, there is general agreement that the ratio of total to potential magnetic energy should be approximately 1.4. However, there are significant differences in the electric current distributions; while static extrapolations are best able to reproduce active regions, they are unable to recover sheared magnetic fields in filament channels using currently available vector magnetogram data. By contrast, time-evolving simulations can recover the filament channel fields at the expense of not matching the observed vector magnetic fields within active regions. We suggest that, at present, the best approach may be a hybrid model using static extrapolations but with additional energization informed by simplified evolution models. This is demonstrated by one of the models. 相似文献