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排序方式: 共有293条查询结果,搜索用时 31 毫秒
261.
Martin M. Sirk Eric J. Korpela Yuzo Ishikawa Jerry Edelstein Edward H. Wishnow Christopher Smith Jeremy McCauley Jason B. McPhate James Curtis Travis Curtis Steven R. Gibson Sharon Jelinsky Jeffrey A. Lynn Mario Marckwordt Nathan Miller Michael Raffanti William Van Shourt Andrew W. Stephan Thomas J. Immel 《Space Science Reviews》2017,212(1-2):631-643
We present the design, implementation, and on-ground performance measurements of the Ionospheric Connection Explorer EUV spectrometer, ICON EUV, a wide field (\(17^{\circ}\times 12^{\circ}\)) extreme ultraviolet (EUV) imaging spectrograph designed to observe the lower ionosphere at tangent altitudes between 100 and 500 km. The primary targets of the spectrometer, which has a spectral range of 54–88 nm, are the Oii emission lines at 61.6 nm and 83.4 nm. Its design, using a single optical element, permits a imaging resolution perpendicular to the spectral dispersion direction with a large (\(12^{\circ} \)) acceptance parallel to the dispersion direction while providing a slit-width dominated spectral resolution of \(R\sim25\) at 58.4 nm. Pre-flight calibration shows that the instrument has met all of the science performance requirements. 相似文献
262.
G. Randall Gladstone S. Alan Stern Kurt D. Retherford Ronald K. Black David C. Slater Michael W. Davis Maarten H. Versteeg Kristian B. Persson Joel W. Parker David E. Kaufmann Anthony F. Egan Thomas K. Greathouse Paul D. Feldman Dana Hurley Wayne R. Pryor Amanda R. Hendrix 《Space Science Reviews》2010,150(1-4):161-181
263.
Michael Ovchinnikov Georgi V. Smirnov Irina Zaramenskikh 《Acta Astronautica》2009,65(11-12):1826-1830
This paper examines the possibility of regular orbital corrections for a satellite controlled by an impulsive force applied along the induction vector of the local geomagnetic field. The main purpose of the correcting considered in the paper is to eliminate the drift in secular variation of the relative orbital parameters over the orbital period. The obtained results are applied to the formation flying problem. The developed method is tested using numerical simulation. 相似文献
264.
Tarter JC Backus PR Mancinelli RL Aurnou JM Backman DE Basri GS Boss AP Clarke A Deming D Doyle LR Feigelson ED Freund F Grinspoon DH Haberle RM Hauck SA Heath MJ Henry TJ Hollingsworth JL Joshi MM Kilston S Liu MC Meikle E Reid IN Rothschild LJ Scalo J Segura A Tang CM Tiedje JM Turnbull MC Walkowicz LM Weber AL Young RE 《Astrobiology》2007,7(1):30-65
Stable, hydrogen-burning, M dwarf stars make up about 75% of all stars in the Galaxy. They are extremely long-lived, and because they are much smaller in mass than the Sun (between 0.5 and 0.08 M(Sun)), their temperature and stellar luminosity are low and peaked in the red. We have re-examined what is known at present about the potential for a terrestrial planet forming within, or migrating into, the classic liquid-surface-water habitable zone close to an M dwarf star. Observations of protoplanetary disks suggest that planet-building materials are common around M dwarfs, but N-body simulations differ in their estimations of the likelihood of potentially habitable, wet planets that reside within their habitable zones, which are only about one-fifth to 1/50th of the width of that for a G star. Particularly in light of the claimed detection of the planets with masses as small as 5.5 and 7.5 M(Earth) orbiting M stars, there seems no reason to exclude the possibility of terrestrial planets. Tidally locked synchronous rotation within the narrow habitable zone does not necessarily lead to atmospheric collapse, and active stellar flaring may not be as much of an evolutionarily disadvantageous factor as has previously been supposed. We conclude that M dwarf stars may indeed be viable hosts for planets on which the origin and evolution of life can occur. A number of planetary processes such as cessation of geothermal activity or thermal and nonthermal atmospheric loss processes may limit the duration of planetary habitability to periods far shorter than the extreme lifetime of the M dwarf star. Nevertheless, it makes sense to include M dwarf stars in programs that seek to find habitable worlds and evidence of life. This paper presents the summary conclusions of an interdisciplinary workshop (http://mstars.seti.org) sponsored by the NASA Astrobiology Institute and convened at the SETI Institute. 相似文献
265.
Lorna M. Small Michael J. Rycroft Shaun Quegan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(4):41-46
The realistic model of Quegan et al. has been used to investigate the convection paths of ionospheric plasma at 300 km altitude, for different polar cap radii and in both hemispheres. Taking the Northern magnetic dip pole to be at a co-latitude of 11° and the Southern magnetic dip pole at a co-latitude of 23°, these paths are presented in a Sun-Earth frame, with the position of the Earth's axis fixed as it is on 21 March, as polar plots centred on the magnetic pole. There are marked hemispheric differences between 13 and 23 L.T., particularly near the stagnation region at 18 to 21 L.T., but only minor differences between 00 and 12 L.T., when the radius of the polar cap exceeds 12°. For a smaller polar cap, the differences between the hemispheres are small at all local times. The time taken to perform a complete circuit is most dependent on the polar cap radius, and most variable - between 15 and 36 h - for convection paths starting near 60° latitude. The time that plasma convecting from noon to near midnight across the Northern polar cap spends within the 10° co-latitude circle increases from 6 h, for a polar cap radius of 10°, to 11.5 h at 17°. These results are compared and contrasted with other model calculation results and with some ground-based and satellite observations of plasma densities at high latitudes. 相似文献
266.
Stelios Charalambides Garry E. Hunt Michael J. Rycroft Robert J. Murgatroyd David W.S. Limbert 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(6):127-132
We present the results of a study of anomalies, which are defined as differences of seasonal means from the data set seasonal means, in the Earth's radiation budget from the analysis of nine years of ten day mean observations derived from the NOAA polar orbiter satellites for the period, 1974–1983. We estimate that the standard deviation in the outgoing longwave flux for this period is less than 12 Wm?2 and typically 7 Wm?2. The results show that there are several geographical areas for which the standard deviation is in excess of 20 Wm?2; in such regions the radiation budget anomalies exceeded these due to natural atmospheric variability. In this paper we discuss the relationship of these anomalies with climatic change. 相似文献
267.
Michael Schulz 《Space Science Reviews》1975,17(2-4):481-536
This review covers the major developments in radiation-belt phenomenology of the past four years (1970–1973). This has been a period characterized by consolidation and refinement of ideas and measurements related to geomagnetically trapped particles. Significant progress has been made in understanding ion and electron pitch-angle distributions within the context of radial diffusion and pitch-angle diffusion, respectively. Comparison of alpha-particle and proton distributions has helped to clarify the relative strengths of known radial-diffusion mechanisms. Careful measurements have indicated the directional flux of cosmic-ray-albedo neutrons, which constitute (through beta decay) a major source of high-energy ( 20 MeV) inner-belt protons. Inclusion of radial-diffusion and geomagnetic-secular effects has brought the theory of the inner proton belt into reasonable agreement with observation. At very lowL values (L 1.2) atmospheric collisions have been found to facilitate the radial transport of 40 keV protons and 2 MeV electrons. The plasmapause has been identified as an important boundary for plasma instabilities (wave-particle interactions) that lead to particle precipitation and red-arc excitation. Suggestions have followed for artificially simulating such plasmaspheric effects by magnetospheric injection of cold barium or lithium plasma. 相似文献
268.
269.
As part of the DOD Logistics Research and Development Program, the Navy is embarking on the development of an Integrated Diagnostics Support System. This System is composed of a number of diagnostic design tools, which are aimed at automating the diagnostic design process. When completed, the tools will be utilized in a comprehensive integrated diagnostic demonstration project applied to a Naval weapon system. The last three years have been characterized by increasing attention given to the definition, implementation, and evaluation of integrated diagnostics concepts. Integrated diagnostics is a structured process which maximizes the effectiveness of diagnostics by integrating pertinent elements, such as testability, automatic and manual testing, training, maintenance aiding, personnel and computer-aided engineering as a means for providing a cost-effective capability to detect and unambiguously isolate all faults known or expected to occur in weapon systems and equipment, and to satisfy weapon system mission requirements. 相似文献
270.
Michael Paluszek 《Acta Astronautica》1983,10(4):163-178
The Space Shuttle Orbiter will be used as an orbital base for near-term space operations. Its payloads will range from compact satellites to large, flexible antennas. This paper addresses the problem of the dynamics and control of the Orbiter with a flexible payload. Two different cases are presented as examples. The first is a long, slender beam which might be used as an element in a large orbiting structure. The second is a compact satellite mounted on a spin table in the Orbiter payload bay. The closed loop limit cycles are determined for the first payload and the open loop eigenvalues are calculated for the second. Models of both payloads are mechanized in a simulation with the Shuttle on-orbit autopilot. The vehicle is put through a series of representative maneuvers and its behavior analyzed. The degree of interaction for each payload is determined and strategies are discussed for its reduction. 相似文献