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971.
Medium energy neutral atom (MENA) imager for the IMAGE mission   总被引:1,自引:0,他引:1  
Pollock  C.J.  Asamura  K.  Baldonado  J.  Balkey  M.M.  Barker  P.  Burch  J.L.  Korpela  E.J.  Cravens  J.  Dirks  G.  Fok  M.-C.  Funsten  H.O.  Grande  M.  Gruntman  M.  Hanley  J.  Jahn  J.-M.  Jenkins  M.  Lampton  M.  Marckwordt  M.  McComas  D.J.  Mukai  T.  Penegor  G.  Pope  S.  Ritzau  S.  Schattenburg  M.L.  Scime  E.  Skoug  R.  Spurgeon  W.  Stecklein  T.  Storms  S.  Urdiales  C.  Valek  P.  van Beek  J.T.M.  Weidner  S.E.  Wüest  M.  Young  M.K.  Zinsmeyer  C. 《Space Science Reviews》2000,91(1-2):113-154
The Medium Energy Neutral Atom (MENA) imager was developed in response to the Imaging from the Magnetopause to the Aurora for Global Exploration (IMAGE) requirement to produce images of energetic neutral atoms (ENAs) in the energy range from 1 to 30 keV. These images will be used to infer characteristics of magnetospheric ion distributions. The MENA imager is a slit camera that images incident ENAs in the polar angle (based on a conventional spherical coordinate system defined by the spacecraft spin axis) and utilizes the spacecraft spin to image in azimuth. The speed of incident ENAs is determined by measuring the time-of-flight (TOF) from the entrance aperture to the detector. A carbon foil in the entrance aperture yields secondary electrons, which are imaged using a position-sensitive Start detector segment. This provides both the one-dimensional (1D) position at which the ENA passed through the aperture and a Start time for the TOF system. Impact of the incident ENA on the 1D position-sensitive Stop detector segment provides both a Stop-timing signal and the location that the ENA impacts the detector. The ENA incident polar angle is derived from the measured Stop and Start positions. Species identification (H vs. O) is based on variation in secondary electron yield with mass for a fixed ENA speed. The MENA imager is designed to produce images with 8°×4° angular resolution over a field of view 140°×360°, over an energy range from 1 keV to 30 keV. Thus, the MENA imager is well suited to conduct measurements relevant to the Earth's ring current, plasma sheet, and (at times) magnetosheath and cusp.  相似文献   
972.
Influence of stack structure on porosity of composite materials at different modes of autoclave molding was studied. To reduce porosity of composite materials, specific stack structure and molding mode are recommended.  相似文献   
973.
A new neural network (NN) based global empirical model for the foF2 parameter, which represents the peak ionospheric electron density, has been developed using extended temporal and spatial geophysical relevant inputs. It has been proposed that this new model be considered as a suitable replacement for the International Union of Radio Science (URSI) and International Radio Consultative Committee (CCIR) model options currently used within the International Reference Ionosphere (IRI) model for the purpose of F2 peak electron density predictions. The most recent version of the model has incorporated data from 135 global ionospheric stations including a number of equatorial stations.  相似文献   
974.
Microorganisms may be a key element in a precursory scenario of growing pioneer plants for extraterrestrial exploration. They can be used for plant inoculation to leach nutritional elements from regolith, to alleviate lunar stressors, as well as to decompose both lunar rocks and the plant straw in order to form a protosoil. Bioleaching capacities of both French marigold (Tagetes patula L.) and the associated bacteria in contact with a lunar rock simulant (terrestrial anorthosite) were examined using the model plant-bacteria microcosms under controlled conditions. Marigold accumulated K, Na, Fe, Zn, Ni, and Cr at higher concentrations in anorthosite compared to the podzol soil. Plants inoculated with the consortium of well-defined species of bacteria accumulated higher levels of K, Mg, and Mn, but lower levels of Ni, Cr, Zn, Na, Ca, Fe, which exist at higher levels in anorthosite. Bacteria also affected the Са/Mg and Fe/Mn ratios in the biomass of marigold grown on anorthosite. Despite their growth retardation, the inoculated plants had 15% higher weight on anorthosite than noninoculated plants. The data suggest that the bacteria supplied basic macro-and microelements to the model plant.  相似文献   
975.
The Japanese lunar explorer SELENE (SElenological and Engineering Explorer), to be launched in 2007, will for the first time utilize VLBI observations in lunar gravimetry investigations. This will particularly improve the accuracy to which the low degree gravitational harmonics and the gravity field near the limb can be measured, and when combined with Doppler measurements will enable three-dimensional information to be extracted. Differential VLBI Radio sources called VRAD experiment involves two on-board sub-satellites, Rstar and Vstar. These will be observed using differential VLBI to measure the trajectories of the satellites with the Japanese network named VERA (VLBI Exploration of Radio Astrometry) and an international VLBI network.  相似文献   
976.
The results of a detailed study of large (by 20% and more) and sharp (faster than ten minutes) changes of the ion flux in the solar wind are presented. The data are provided by regular measurements onboard the INTERBALL-1 satellite in the period 1996–1999. Using statistical analysis, we obtained the distribution of these changes in their absolute and relative strength. It is shown that, for a considerable proportion of the events, such sharp and large changes of the ion flux (density) take place under conditions of fairly constant values of the solar wind velocity and of both the magnitude and components of the interplanetary magnetic field.  相似文献   
977.
Results of the comparative analysis of the dynamics of SCR fluxes with energies of 1–100 MeV in the interplanetary environment according to the data of the ACE and Wind spacecraft and within the Earth’s magnetosphere according to the data of the GOES-15 and Electro-L satellites in the region of geostationary orbits, and POES-19 and Meteor-M1 in the region of polar caps during two increases in SCR of January 19–31, 2012, are presented. It is shown that the decrease in the efficiency of SCR penetration into the Earth’s magnetosphere in the region of the orbits under study on January 28, 2012, is related to the passage of the Earth’s magnetosphere through the interplanetary environment structure with a quasi-radial interplanetary magnetic field and a small pressure of the solar wind.  相似文献   
978.
The results of comparison of the characteristics of sharp boundaries of small-scale and medium-scale solar wind structures in the case of their simultaneous observation on widely spaced spacecraft are described. It is shown that even very sharp boundaries, with duration of several seconds or fractions of a second, retain their amplitude and remain very sharp during solar wind propagation to distances of up to a million kilometers.  相似文献   
979.
980.
Fearing that mistaken decisions may be made, the author offers his comments to clarify the future possibilities for Ariane, Hermes and Columbus. The decisions soon to be taken on the manned spaceflight programme will affect the future of the entire European space programme. The possibilities for air-breathing propulsion are also reviewed.  相似文献   
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