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731.
An onboard astronomical system is suggested, based on the developed method using virtual measurements of zenith distances
of stars. Two algorithms of the method are described, their theory is given, and statistical results of the system’s simulation
are presented. 相似文献
732.
The actual topic of optimization of multi-orbit low-thrust spacecraft inter-orbital transfers is considered. We have developed
an original approach to solving this problem, and it is described. 相似文献
733.
Bezrukikh V. V. Kotova G. A. Lezhen L. A. Lemaire J. Pierrard V. Venediktov Yu. I. 《Cosmic Research》2003,41(4):392-402
We present the results of temperature and density measurement of plasmaspheric protons under quiet and disturbed conditions in the night and dayside sectors of the plasmasphere obtained with the Auroral Probe/Alpha-3 instrument during September 1996 and January 1997. According to the experimental data, the proton temperature in the night sector of the plasmasphere depends on the level of geomagnetic disturbance: it is found that at night hours the values of temperatures inside the plasmasphere at 2.4 < L < 3.5 decreased considerably after the commencement of a geomagnetic storm. The temperature decrease, as a rule, was accompanied by the formation of a flat plateau on the density distribution n(L) at 2.4 < L < 3.5. The above experimental facts (decreasing proton temperature and formation of a flat part on the n(L) distribution) allow us to conclude that the decrease in the proton temperature in the night sector of the plasmasphere connected with magnetic disturbances is caused by the filling of field tubes (depleted after the commencement of the storm) with colder ionospheric plasma. The proton temperature in the dayside sector of the plasmasphere virtually does not depend on the level of the geomagnetic disturbance. 相似文献
734.
S I Bartsev V V Mezhevikin V A Okhonin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,31(7):1823-1832
This paper is devoted to the consideration of possible viewpoint on CELSS development and design. If the aim to create practically applicable CELSS is accepted then the task to optimize the process of CELSS research and development in terms of minimum cost, hours, maximum applicability, scientific contribution, etc. becomes actual. Requirements of applicability and scientific significance are synergetic since understanding of general properties of CELSS gives an ability to create CELSS for different applications. To accomplish the task three main groups of parameters have to be optimized: i) configuration and operating parameters of developing CELSS itself; ii) organizational management of research and development of CELSS; iii) features of an area where CELSS is planned to be used (space missions, terrestrial applications, or biosphere investigation) and where requirements to CELSS characteristic come from. Given paper is a brief review presented some attempts to arrange mentioned above into some set of formalized and interacting criteria, and some progression of research stages derived from these criteria. 相似文献
735.
Agzamov A.M. Kulakovskij V.V. Klufas S.I. Muraviev V.V. Vorovjev Y.P. Veretennikov I.V. 《Aerospace and Electronic Systems Magazine, IEEE》2003,18(11):17-20
This article represents the research results of the television space surveillance system, or, in other words, the optical surveillance system. The purpose of the work is the design of a specialized optical surveillance system, stabilization and surveillance equipment, and a television unit. The system's simplified structural and functional scheme is described, as well as its justification and operation principle. The application prospects are estimated. 相似文献
736.
The effect of cycle slips of the carrier recovery phase-locked loop (PLL) on the performance of coherent M-ary phase-shift keyed (MPSK) systems is dealt with. It is shown that each cycle slip causes a 1 bit error in a differentially encoded and Gray encoded signal stream. Different situations are investigated and compared with regard to the effect of these errors. 相似文献
737.
A Pavy-Le Traon A Maillet P Vasseur Clausen M A Custaud I Alferova C Gharib J O Fortrat 《Acta Astronautica》2001,49(3-10):145-151
Thigh cuffs are used by Russian cosmonauts to limit the fluid shift induced by space flight. A ground simulation using the head-down bed rest (HDBR) model was performed to assess the effects of thigh cuffs on clinical tolerance and orthostatic adaptation. 8 male healthy volunteers (32.4 +/- 1.9 years) participated twice in a 7-day HDBR--one time with thigh cuffs (worn daily from 9 am to 7 pm) (TC) and one time without (WTC). Orthostatic tolerance was assessed by a 10 minute stand test and by a LBNP test (5 min at -15, -30, -45 mmHg) before (BDC-1) and at the end of the HDBR period (R+1). Plasma volume was measured before and at the end of HDBR by the Evans blue dye dilution technique. Thigh cuffs limits headache due to fluid shift, as well as the loss in plasma volume (TC: -5.85 +/- 0.95%; WTC: -9.09 +/- 0.82%, p<0.05). The mean duration of the stand test (R+1) did not differ in the two group (TC 7.1 +/- 1.3 min; WTC 7.0 +/- 1.0 min). The increase in HR and decrease in diastolic blood pressure were slightly but significantly larger without thigh cuffs. Duration of the LBNP tests did not differ with thigh cuffs. Thigh cuffs limit the symptoms due to fluid shift and the loss in plasma volume. They partly reduced the increase in HR during orthostatic stress but had no effect on duration of orthostatic stress tests. 相似文献
738.
Yamamoto H. Sugita K. Kanzaki N. Johja I. Hiraki Y. Kuwahara M. 《Aerospace and Electronic Systems Magazine, IEEE》1990,5(6):31-35
A method for enhancing the boundaries of magnetic resonance images (MRIs) using a V-filter (a spatial nonlinear filter) is presented. By iterated V-filtering the signal-to-noise ratio of the MRI can be increased while preserving edge sharpness. A simulation experiment was carried out to evaluate the filter, using clinical brain images. The boundaries of the brain tumor and edematous region were precisely extracted by the region segmentation techniques 相似文献
739.
B. Kneiß el I. Mann 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1991,11(12):123-126
The out-of-ecliptic distribution of interplanetary dust, i.e. its number density, mainly has been subject to optical or infrared remote sensing techniques. As the population in interplanetary space is made up of orbiting particles which will cross the ecliptic plane, determination of their orbital properties there gives a possibility also to derive their out-of-ecliptic distribution. Determination of orbital elements is provided by advanced detectors capable of measuring the vector of impact velocity. In a simple model, which applies for advanced detectors in near earth orbit, the feasibility of the method to determine the out-of-ecliptic spatial distribution of dust has been tested. 相似文献
740.
The instrumental and applied problems related to the design of a passive magnetic attitude control system for the Munin nanosatellite are considered. The system is constructed from a strong permanent magnet and a set of hysteresis rods. These rods are made of magnetically soft material using a special technology, and they allow us to support the satellite orientation with respect to the local magnetic field vector with a given accuracy and time response. By using asymptotic and numerical methods, we investigate the satellite dynamics for different models of hysteresis. The issues concerning the arrangement of the rods and their interaction with the fields of permanent magnets mounted onboard the satellite are discussed. 相似文献