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141.
P. A. J. de Korte J. A. M. Bleeker A. J. F. den Boggende G. Branduardi-Raymont A. C. Brinkman J. L. Culhane E. H. B. M. Gronenschild I. Mason S. P. McKechnie 《Space Science Reviews》1981,30(1-4):495-511
The instrument configuration and performance characteristics of the X-ray imaging telescopes on EXOSAT are described. The instrument comprises two fully independent Wolter I imaging telescopes. Each telescope can be used in either of two principal modes: (i) an imaging mode with either a position sensitive proportional counter or a channel multiplier array plate in the focal plane, (ii) a spectrometer mode which features a 500 lines/mm and/or a 1000 lines/mm transmission grating as dispersive element.Preliminary results from the calibration of the fully integrated experiment indicate an ultimate angular resolution of 8.5 arc sec full width at half maximum or 17.5 arc sec half-power beam width. The ultimate wavelength resolution in the spectrometer mode ranges from 1Å for wavelengths below 50Å, to 5Å at wavelengths near 300Å.A method for estimating the telescope performance is given which reasonably accounts for the influence of the X-ray source spectrum and the degree of interstellar absorption on the counting statistics.A comparison between EXOSAT and the EINSTEIN telescope in terms of band width/resolution and minimum source detectability shows an enhanced potential for EXOSAT relative to EINSTEIN for sources with T 107K and low column densities (< 4 × 1020cm–2) and a reduced potential for sources with hard, or heavily cut-off, spectra. 相似文献
142.
de Jager C. Hartle James B. Drawin H. W. Giovanelli R. G. Freudenthal Hans Wittenberg H. Tobias Cornelius A. Van Der Laan H. Smit J. A. 《Space Science Reviews》1974,15(5):741-746
Space Science Reviews - 相似文献
143.
144.
通常用实验方法测定园柱螺旋弹簧残余应力。本文提出了切割法对比测试技术,为确定高应力、高疲劳强度的弹簧制造工艺提供了依据。 相似文献
145.
压缩机的设计与制造性能尚不能充分适应风洞的运行范围 ,安全、可靠的防喘振措施是保证风洞安全运行的重要条件之一。作者讨论了旁路调节作为风洞中防喘振措施的可行性。在考虑跨声速风洞中气体压缩性的基础上 ,给出了风洞中旁路调节的估算方法 ,分析和讨论了旁路对风洞性能的影响。结果表明 :旁路的增加 ,使风洞工作点向大流量、低压缩比方向移动 ,达到有效、可靠防喘振的目的 相似文献
146.
I. Zaets O. Podolich O. Kukharenko G. Reshetnyak S. Shpylova M. Sosnin L. Khirunenko N. Kozyrovska J.-P. de Vera 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Bacterial cellulose (BC) is a matrix for a biofilm formation, which is critical for survival and persistence of microbes in harsh environments. BC could play a significant role in the formation of microbial mats in pristine ecosystems on Earth. The prime objective of this study was to measure to what extent spectral and other characteristics of BC were changed under the performance of BC interaction with the earthly rock – anorthosite – via microorganisms. The spectral analyses (Fourier Transform Infrared FT-IR, spectroscopy, and atomic absorption spectroscopy) showed unprecedented accumulation of chemical elements in the BC-based biofilm. The absorption capacity of IR by BC was shielded a little by mineral crust formed by microorganisms on the BC-based biofilm surface, especially clearly seen in the range of 1200–900 cm−1 in FT-IR spectra. Confocal scanning laser microscopy analysis revealed that elements bioleached from anorthosite created surface coats on the BC nanofibril web. At the same time, the vibrational spectra bands showed the presence of the characteristic region of anomeric carbons (960–730 cm−1), wherein a band at 897 cm−1 confirmed the presence of β-1, 4-linkages, which may serve as the cellulose fingerprint region. Results show that BC may be a biosignature for search signs of living organisms in rock records. 相似文献
147.
148.
Traditionally, space systems have been built for fixed requirements and optimized for highest performance. Future systems for human exploration of Moon and Mars, however, require focus on new architectural strategies geared towards increased affordability and survivability in addition to performance. Reconfigurability is a new paradigm in system design that enhances these qualities. Reconfigurable systems can attain different states with new or modified capabilities, as required with changing needs, over time. Such systems can lower mission costs through mass savings by efficient use of a fixed set of hardware for multiple functions. Their survivability is improved through their ability to reconfigure into different states so that some level of over-all functionality is retained. This study, with a focus on planetary surface vehicles, presents a methodology for determining optimal designs of reconfigurable systems. It also proposes metrics for assessing the impact of reconfigurability. It is found that for the specific scenario considered, the mass utilization efficiency in a fleet of reconfigurable vehicles is increased by 27% while the survivability can be increased by a factor of 3. 相似文献
149.
First Results of the THEMIS Search Coil Magnetometers 总被引:1,自引:0,他引:1
O. Le Contel A. Roux P. Robert C. Coillot A. Bouabdellah B. de la Porte D. Alison S. Ruocco V. Angelopoulos K. Bromund C. C. Chaston C. Cully H. U. Auster K. H. Glassmeier W. Baumjohann C. W. Carlson J. P. McFadden D. Larson 《Space Science Reviews》2008,141(1-4):509-534
We present the first data from the THEMIS Search Coil Magnetometers (SCM), taken between March and June 2007 while the THEMIS constellation apogee moved from the duskside toward the dawnside. Data reduction, especially the SCM calibration method and spurious noise reduction process, is described. The signatures of magnetic fluctuations in key magnetospheric regions such as the bow shock, the magnetopause and the magnetotail during a substorm, are described. We also discuss the role that magnetic fluctuations could play in plasma transport, acceleration and heating. 相似文献
150.
M.A. Abdu C.G.M. BrumI.S. Batista J.H.A. SobralE.R. de Paula J.R. Souza 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The F layer critical frequency (foF2) as measured by Digisondes in the equatorial and low latitude locations in Brazil is analyzed to investigate the seasonal and solar flux controls of the intensity of the equatorial ionization anomaly (EIA) in the equinoctial month of March. The analysis also included the total electron content (TEC) as measured by a GPS receiver operated at the EIA crest location. The foF2 data set covered a period of large solar flux variation from 1996 to 2003, while the GPS TEC data was for a period in 2002–2003 when the solar flux parameter F10.7 underwent large variations, permitting in both cases an examination of the solar flux effects on these parameters. The seasonal variation pattern in TEC shows a maximum in equinoctial months and a minimum in June solstice, with similar variations for foF2. The solar flux dependence of the TEC is a maximum during equinoxes, especially for post-sunset TEC values at times when the latitudinal distribution is controlled by the equatorial evening plasma fountain processes. Significant variations with local time are found in the degree of solar flux dependence for both the TEC and EIA. The EIA intensity shows large dependence on F10.7 during post-sunset to midnight hours. These results are discussed in comparison with their corresponding IRI representations. 相似文献