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411.
Kim N.P. Stanbery B.J. Burgess R.M. Mickelsen R.A. McClelland R.W. King B.D. Gale R.P. 《Aerospace and Electronic Systems Magazine, IEEE》1989,4(11):23-32
Mechanically stacked tandem cells consisting of GaAs thin-film upper cells and CuInSe2 thin-film lower cells have been developed to meet the increasing power needs projected for future spacecraft. The authors report the fabrication of the first highly efficient lightweight GaAs/CuInSe2 tandem cell on a 2-mil thick substrate, update recent performance improvements in thin-film GaAs/CuInSe2 tandem cells, and discuss their application to space power systems. The efficiency of 4-cm2 cells has improved to 21.6% AM0, the highest ever reported for a thin-film photovoltaic cell. Lightweight 4-cm2 tandem cells have been successfully fabricated with efficiencies as high as 20.8%. These cells weighed about 180 mg without optimized substrate trimming. Radiation and operating temperature effects on GaAs/CuInSe2 tandem cells are also discussed, and an interconnect scheme to form a voltage-matched string is described 相似文献
412.
B. Nebeling K. Roessler G. Schmitz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1986,6(12):207-210
The redox properties of irradiated liquid and frozen H2O, NH3 and H2O/NH3 mixtures at 298 K and 77 K, resp., towards some simple organic molecules have been checked by injecting carrierfree 11C atoms and analyzing their chemical state by means of radiochromatography. The reactions and the stability of organic products versus radiation dose (in this study by MeV protons) depend on temperature, phase state, mobility of radicals, their concentration and reactivity. Especially dangerous are the reactive OH and O2H radicals which oxidize organic material to inorganic CO2. Highest stability has been found at low temperatures (solid state, reduced mobility of radicals) and for systems containing H-donors (H2O/NH3 mixtures), which reduce the concentration of oxidizing radicals. The fact that many bodies in space consist of H2O-ice with NH3 and CH4 additives at temperatures between 10 and 150 K is promising in view of the survival of organic matter under high doses of radiation. 相似文献
413.
The problem of estimating the time difference of arrival of a signal with unknown spectrum to two receivers is treated. A signal model containing both spectral and delay parameters is derived. The model parameters are computed by a two-step procedure: (1) the modified Yule-Walker equations are used to estimate the autoregressive spectrum of the source signal, and (2) a frequency domain squared error criterion is minimized to provide the delay estimate. The performance of the proposed technique is illustrated by simulation results. 相似文献
414.
S B Curtis W Atwell R Beever A Hardy 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1986,6(11):269-274
In order to make an assessment of radiation risk during manned missions in space, it is necessary first to have as accurate an estimation as possible of the radiation environment within the spacecraft to which the astronauts will be exposed. Then, with this knowledge and the inclusion of body self-shielding, estimations can be made of absorbed doses for various body organs (skin, eye, blood-forming organs, etc.). A review is presented of our present knowledge of the radiation environments and absorbed doses expected for several space mission scenarios selected for our development of the new radiation protection guidelines. The scenarios selected are a 90-day mission at an altitude (450 km) and orbital inclinations (28.5 degrees, 57 degrees and 90 degrees) appropriate for NASA's Space Station, a 15-day sortie to geosynchronous orbit and a 90-day lunar mission. All scenarios chosen yielded dose equivalents between five and ten rem to the blood forming organs if no large solar particle event were encountered. Such particle events could add considerable exposure particularly to the skin and eye for all scenarios except the one at 28.5 degrees orbital inclination. 相似文献
415.
B.N. Swanenburg 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(4):71
The NASA Gamma-Ray Observatory, GRO, will carry two instruments for low energy gamma-ray astronomy. The ‘Oriented Scintillation Spectrometer Experiment - OSSE’ represents the latest step in the evolution of collimated detectors. A large detection area, simultaneous source and background observation and rigorous control over systematic errors yield significant improvements in sensitivity over earlier instruments. The ‘Imaging Compton Telescope - COMPTEL’ brings the proven concept of the Compton telescope to the state of the art level. Position sensitive scintillation detectors make it possible to generate sky images with a resolution of about 2° over a f.o.v. of about 1 sr. The complementary nature of these two experiments promises a first in-depth exploration of the sky in a wavelength range which covers the transition from the X-ray sky to the apparently unrelated high energy gamma-ray sky. Possible directions of further evolution of these experiments will be discussed. 相似文献
416.
Shats S. Bobrovsky B.Z. Shaked U. 《IEEE transactions on aerospace and electronic systems》1988,24(6):670-677
The problem of minimum variance discrete-time state estimation of a continuous-time double integrator via noisy continuous-time measurements is considered. The error covariance matrices of this estimation are calculated and analyzed. The relations between these covariance matrices and the error covariance matrix of the optimal continuous-time filter are obtained, and a way for determining the required sampling period is proposed. A commonly used approximated model is investigated; it is shown to be inappropriate unless a specific improvement is introduced in the model 相似文献
417.
Bhat A.K.S. Biswas A. Iyengar B.S.R. 《IEEE transactions on aerospace and electronic systems》1995,31(3):1186-1193
A series-parallel resonant converter employing (LC)(LC)-type tank circuit operating in lagging power factor (PF) mode is presented and analyzed using complex ac circuit analysis. Design curves are obtained and the converter is optimized under certain constraints. Detailed Space Integrated Control Experiment (SPICE) simulation results are presented to evaluate the performance of the designed converter under varying load conditions. Results obtained from an experimental converter are also presented. The results obtained from the theory, SPICE simulation, and the experimental converter are compared. The proposed converter has high efficiency from full load to very light load (<10%). Switching frequency variation required for a wide change in the load (near load open circuit to full load) is narrow compared with the series resonant converter (SRC) 相似文献
418.
Robert B. Decker 《Space Science Reviews》1988,48(3-4):195-262
We review the basic techniques and results of numerical codes used to model the acceleration of charged particles at oblique, fast-mode, collisionless shocks. The emphasis is upon models in which accelerated particles (ions) are treated as test particles, and particle dynamics is calculated by numerically integrating along exact phase-space orbits. We first review the case where ions are sufficiently energetic so that the shock can be approximated by a planar discontinuity, and where the electromagnetic fields on both sides of the shock are defined at the outset of each computer run. When the fields are uniform and static, particles are accelerated by the scatter-free drift acceleration process at a single shock encounter. We review the characteristics of scatter-free drift acceleration by considering how an incident particle distribution is modified by interacting with a shock. Next we discuss drift acceleration when magnetic fluctuations are introduced on both sides of the shock, and compare these results with those obtained under scatter-free conditions. We describe the modeling of multiple shock encounters, discuss specific applications, and compare the model predictions with theory. Finally, we review some recent numerical simulations that illustrate the importance of shock structure to both the ion injection process and to the acceleration of ions to high energies at quasi-perpendicular shocks. 相似文献
419.
B Wiegel W Heinrich E V Benton A Frank 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1992,12(2-3):349-353
We present measurements of LET spectra for near earth orbits with various inclinations and altitudes. A comparison with calculated LET spectra shows that the contribution from direct ionizing galactic cosmic rays is well described by the models. An additional contribution to the spectra originates from stopping protons and from nuclear interactions of particles with material. In the case of an interaction a large amount of energy is deposited in a small volume by target recoils or target fragments. These events will be called short range (SR) events. For a low inclination orbit radiation belt protons are the main source of these events while galactic protons become more important when increasing the inclination to near polar orbits. We show that the contribution of SR events for orbits with low altitude (324 km) and 57 degrees inclination is comparable to that for an orbit with 28 degrees inclination at a high altitude (510 km). 相似文献
420.
This paper presents the results of medical investigations performed in the Salyut-7 8-month mission in which a professional physician took part. The paper contains anthropometric measurements, results of investigating the vestibular function, cardiovascular function at rest and in response to multi-step tests (with emphasis on echocardiographic measurements), metabolic parameters and hormonal status. It also discusses medical aspects of the extravehicular activity. The medical investigations, although some new methods were applied, provided the continuity of methodical approaches and data accumulated in previous missions. 相似文献