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481.
Kinsey G.S. King R.R. Edmondson K.M. Stavrides A.P. Hojun Yoon Fetzer C.M. Colter P.C. Ermer J.H. Gillanders M.S. Hebert P. Granata J.E. Karam N.H. 《Aerospace and Electronic Systems Magazine, IEEE》2003,18(3):8-10
Solar cells suitable for the space environment must combine high-efficiency, high energy density, and radiation hardness in a manufacturable design. As improvement in one performance parameter usually results in degradation in one or more of the remaining parameters, careful optimization is required to enhance overall performance. The ultra triple-junction cell developed builds upon the established success of the fully qualified improved triple-junction cell currently in production. In the ultra triple-junction cell configuration, improved robustness and efficiency after radiation exposure augment a cell design expected to deliver 28% beginning-of-life efficiency in production. 相似文献
482.
Moschopoulos G. Mei Qiu Pinheiro H. Jain P. 《IEEE transactions on aerospace and electronic systems》2003,39(2):660-674
A pulsewidth modulated (PWM) full-bridge converter that simultaneously performs input power factor correction (PFC) and DC-DC conversion is proposed. The converter is the same as the standard voltage-fed PWM full-bridge converter with a diode-bridge low-pass filter front end, but with a slight modification that results in an improvement in power factor that is sufficient to satisfy the EN61000-3-2 requirements for electrical equipment. The operation of the converter is explained and analyzed, and the results of the analysis are used to determine the converter's steady-state characteristics, which are discussed in detail. A design procedure for the selection of components is then derived and demonstrated with an example. The feasibility of the converter and its ability to satisfy EN61000-3-2 requirements on electrical equipment is shown with results obtained from an experimental prototype. 相似文献
483.
Icheln C. Ollikainen J. Vainikainen P. 《Aerospace and Electronic Systems Magazine, IEEE》2001,16(11):17-20
In this work, the influence of resistive absorbers in the vicinity of small antennas was investigated, in order to define a lower limit for the size of a small anechoic chamber for antenna calibration and radiation pattern measurements, with respect to the distance between the antenna under test (AUT) and the RF absorbers lining the walls. Furthermore, the influence of a relatively narrow transmission channel, formed by the absorbers on the side walls between the measurement antenna and the AUT was investigated. It was found by measurements that absorbers with the length of 610 mm do not have a measurable effect on the radiation characteristics of a small antenna at around 1.8 GHz, as long as they are kept more than 100 mm from the AUT, and the transmission channel formed by the absorbers between the antennas is wider than 100 mm 相似文献
484.
Kovar P. Vejrazka F. Seidl L. Kacmarik P. 《Aerospace and Electronic Systems Magazine, IEEE》2005,20(12):21-23
This paper deals with the latest version of Experimental GNSS receiver built at the Czech Technical University and describes integration of GLONASS signal processing to the receiver. The new FPGA platform Virtex-D Pro by Xilinx is used and enables integration of whole digital signal processing of GNSS receiver into the single chip. The RE unit of the receiver is capable of processing all GLONASS frequency of the Li and L2 bands in two independent RE channels; each channel can process one band. The frequency selection of the appropriate satellite is accomplished in a digital correlator. The development flow of the GLONASS correlator is discussed herein. The complexity of the GLONASS correlator with complexity of GPS correlator is compared. The developed GLONASS correlator was tested in Simuelink tool during development. The next test was carried out using GLONASS simulator and real GLONASS satellite signal. 相似文献
485.
W F Blakely A C Miller M B Grace C B McLeland L Luo J M Muderhwa V L Miner P G Prasanna 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,31(6):1487-1493
The multiparametric dosimetry system that we are developing for medical radiological defense applications could be adapted for spaceflight environments. The system complements the internationally accepted personnel dosimeters and cytogenetic analysis of chromosome aberrations, considered the best means of documenting radiation doses for health records. Our system consists of a portable hematology analyzer, molecular biodosimetry using nucleic acid and antigen-based diagnostic equipment, and a dose assessment management software application. A dry-capillary tube reagent-based centrifuge blood cell counter (QBC Autoread Plus, Becton [correction of Beckon] Dickinson Bioscience) measures peripheral blood lymphocytes and monocytes, which could determine radiation dose based on the kinetics of blood cell depletion. Molecular biomarkers for ionizing radiation exposure (gene expression changes, blood proteins) can be measured in real time using such diagnostic detection technologies as miniaturized nucleic acid sequences and antigen-based biosensors, but they require validation of dose-dependent targets and development of optimized protocols and analysis systems. The Biodosimetry Assessment Tool, a software application, calculates radiation dose based on a patient's physical signs and symptoms and blood cell count analysis. It also annotates location of personnel dosimeters, displays a summary of a patient's dosimetric information to healthcare professionals, and archives the data for further use. These radiation assessment diagnostic technologies can have dual-use applications supporting general medical-related care. 相似文献
486.
In radar systems, extended Kalman-Bucy filters (EKBFs) are used to estimate state vectors of objects in track. Filter models accounting for fundamental aerodynamic forces on reentry vehicles are well known. A general model structure accommodating the dynamics of reentry vehicles in both exoatmospheric and endoatmospheric flight is presented. The associated EKBFs for these various models are described and the resulting associated parameter estimation and identification problems are discussed. The effects of position, velocity, drag, and aerodynamic lift are described within a nested set of EKBF models 相似文献
487.
488.
The enhancements of solar protons with an energy of more than 30 MeV, originating from flares in one active region and observed simultaneously aboard three spacecraft Vega-1, 2 and Prognoz-10 in July 1985, are analyzed and approximated in this work by using the reflection model [2]. The numerical values of several physical parameters (the parameters of distribution of solar cosmic ray (SCR) particles inside heliosphere traps, the coefficients of trap transparency) that are not observed by direct measurements are estimated. 相似文献
489.
Angle glint can be explained as distortions in the radar echo signal phase front, or alternatively, deviations of the direction of power flow from the radial direction. Here we show that these two theories yield identical results when the polarization of the scattered waves and the receiving antenna are considered. 相似文献
490.
D. V. Titov H. Svedhem D. McCoy J. -P. Lebreton S. Barabash J. -L. Bertaux P. Drossart V. Formisano B. Haeusler O. I. Korablev W. Markiewicz D. Neveance M. Petzold G. Piccioni T. L. Zhang F. W. Taylor E. Lellouch D. Koschny O. Witasse M. Warhaut A. Acomazzo J. Rodrigues-Cannabal J. Fabrega T. Schirmann A. Clochet M. Coradini 《Cosmic Research》2006,44(4):334-348
The first European mission to Venus (Venus Express) is described. It is based on a repeated use of the Mars Express design with minor modifications dictated in the main by more severe thermal environment at Venus. The main scientific task of the mission is global exploration of the Venusian atmosphere, circumplanetary plasma, and the planet surface from an orbiting spacecraft. The Venus Express payload includes seven instruments, five of which are inherited from the missions Mars Express and Rosetta. Two instruments were specially designed for Venus Express. The advantages of Venus Express in comparison with previous missions are in using advanced instrumentation and methods of remote sounding, as well as a spacecraft with a broad spectrum of capabilities of orbital observations. 相似文献