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- The Korean Space Science Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-052x (ISSN : 1225-052x)
1225-052x
- DB구축현황 : 1,253건 (DB Construction : 1,253 Articles)
총 게시글 1,253건
페이지 43/126
421
- Kanjanascul, Chanisa
- Journal of astronomy and space sciences
- 29, n.2
- pp.131-140
- 2012
- 원문 바로보기
We presented fundamental stellar parameters and evolutionary statuses of six solar type detached eclipsing binaries whose masses are in the range of 0.97-1.43 <TEX>$M_{\odot}$</TEX>. EK Cep and FL Lyr belong to the zero age main sequence. HS Hya, IT Cas and CD Tau are on the main sequence. Their ages are 1.3, 1.9 and 2.2 Gyr, respectively. Both component stars of AI Phe evolved to sub giants and its age is 4.0 Gyr. Those ages of the detached binary systems show good agreement with the time scale for synchronization and circularization of the binary systems.
422
- Oh, Eun-Song
- Journal of astronomy and space sciences
- 29, n.2
- pp.199-208
- 2012
- 원문 바로보기
The world's first geostationary ocean color imager (GOCI) is a three-mirror anastigmat optical system 140 mm in diameter. Designed for 500 m ground sampling distance, this paper deals with on-orbit modulation transfer function (MTF)measurement and analysis for GOCI. First, the knife-edge and point source methods were applied to the 8th band (865 nm) image measured April 5th, 2011. The target details used are the coastlines of the Korean peninsula and of Japan, and an island 400 meters in diameter. The resulting MTFs are 0.35 and 0.34 for the Korean East Coastline and Japanese West Coastline edge targets, respectively, and 0.38 for the island target. The daily and seasonal MTF variations at the Nyquist frequency were also checked, and the result is <TEX>$0.32{\pm}0.04$</TEX> on average. From these results, we confirm that the GOCI on-orbit MTF performance satisfies the design requirements of 0.32 for 865 nm wavelength.
423
- Seo, Haingja
- Journal of astronomy and space sciences
- 29, n.4
- pp.375-380
- 2012
- 원문 바로보기
It is a crucial matter to select a landing site for landers or rovers in planning the Mars exploration. The landing site must have not only a scientific value as a landing site, but also geographical features to lead a safe landing for Mars probes. In this regard, this study analyzed landing site of Mars probes and rovers in previous studies and discussed the adequacy of the landing site to scientific missions. Moreover, this study also examined domestic studies on the Mars. The frameworks of these studies will guide the selection of exploration sites and a landing site when sending Mars probe to the Mars through our own efforts. Additionally, this paper will be used as the preliminary data for selection of exploration site and a landing site.
424
- Nha, Il-Seong
- Journal of astronomy and space sciences
- 29, n.2
- pp.209-220
- 2012
- 원문 바로보기
This paper will introduce and overview in general the <TEX>$Seongbyeon$</TEX> <TEX>$Deungrok$</TEX> issued by the Gwansang-gam, the Astronomical Board in the Joseon Dynasty of Korea. All the Chinese characters in the 1668 <TEX>$Seongbyeon$</TEX> <TEX>$Deungrok$</TEX> was deciphered at first and these were translated into Korean and English. With these translations and the word 'white vapor' in particular we discuss the nature of the main object in this <TEX>$Deungrok$</TEX>. Lastly, names of observers who engaged in the observations of this 1668 celestial, which are made as a by-product of this research, are introduced.
425
- Eggleton, Peter P.
- Journal of astronomy and space sciences
- 29, n.2
- pp.145-149
- 2012
- 원문 바로보기
I describe a series of processes, including hierarchical fragmentation, gravitational scattering, Kozai cycles within triple systems, tidal friction and magnetic braking, that I believe are responsible for producing the modest but significant fraction of stars that are observed as contact binaries. I also discuss further processes, namely heat transport, mass transport, nuclear evolution, thermal relaxation oscillations, and further magnetic braking with tidal friction, that influence the evolution during contact. The endpoint, for contact, is that the two components merge into a single star, as recently was observed in the remarkable system V1309 Sco. The single star probably throws off some mass and rotates rapidly at first, and then slows by magnetic braking to become a rather inconspicuous but normal dwarf or subgiant. If however the contact binary was part of a triple system originally-as I suggested above was rather likely-then the result could be a <TEX>$widish$</TEX> binary with apparently non-coeval components. There are several such known.
426
- Chang, Heon-Young
- Journal of astronomy and space sciences
- 29, n.2
- pp.97-101
- 2012
- 원문 바로보기
Monitoring sunspots consistently is the most basic step required to study various aspects of solar activity. To achieve this goal, the observers must regularly calculate their own correction factor <TEX>$k$</TEX> and keep it stable. Relatively recently, two observing teams in South Korea have presented interesting papers which claim that revisions that take the yearly-basis <TEX>$k$</TEX> into account lead to a better agreement with the international relative sunspot number <TEX>$R_i$</TEX>, and that yearly <TEX>$k$</TEX> apparently varies with the solar cycle. In this paper, using artificial data sets we have modeled the sunspot numbers as a superposition of random noise and a slowly varying background function, and attempted to investigate whether the variation in the correction factor is coupled with the solar cycle. Regardless of the statistical distributions of the random noise, we have found the correction factor increases as sunspot numbers increase, as claimed in the reports mentioned above. The degree of dependence of correction factor <TEX>$k$</TEX> on the sunspot number is subject to the signal-to-noise ratio. Therefore, we conclude that apparent dependence of the value of the correction factor <TEX>$k$</TEX> on the phase of the solar cycle is not due to a physical property, but a statistical property of the data.
427
- Elias, Nicholas M. II
- Journal of astronomy and space sciences
- 29, n.1
- pp.85-91
- 2012
- 원문 바로보기
Optical interferometry and polarimetry have separately provided new insights into stellar astronomy, especially in the fields of fundamental parameters and atmospheric models. We present: scientific justifications for 'full-Stokes' optical interferometric polarimetry (OIP); updated instrument requirements; preliminary beam combiner designs; polarimeter design; end-to-end OIP data reduction; and realistic reimaged full-Stokes models of Be stars with a suitable number of telescopes plus noise sources. All of this work represents preliminary research to construct an OIP beam combiner.
428
- Chang, Heon-Young
- Journal of astronomy and space sciences
- 29, n.3
- pp.253-258
- 2012
- 원문 바로보기
We revisit the relation between the peak luminosity <TEX>$L_{iso}$</TEX> and the spectral time lag in the source frame. Since gamma-ray bursts (GRBs) are generally thought to be beamed, it is natural to expect that the collimation-corrected peak luminosity may well correlate with the spectral time lag in the source frame if the lag-luminosity relation in the GRB source frame exists. With 12 long GRBs detected by the Swift satellite, whose redshift and spectral lags in the source frame are known, we computed <TEX>$L_{0,H}$</TEX> and <TEX>$L_{0,W}$</TEX> using bulk Lorentz factors <TEX>${\Gamma}_{0,H}$</TEX> and <TEX>${\Gamma}_{0,W}$</TEX> archived in the published literature, where the subscripts H and W represent homogeneous and wind-like circumburst environments, respectively. We have confirmed that the isotropic peak luminosity correlates with the spectral time lag in the source frame. We have also confirmed that there is an anti-correlation between the source-frame spectral lag and the peak energy, <TEX>$E_{peak}$</TEX> (1 + z) in the source frame. We have found that the collimation-corrected luminosity correlates in a similar way with the spectral lag, except that the correlations are somewhat less tight. The correlation in the wind density profile seems to agree with the isotropic peak luminosity case better than in the homogeneous case. Finally we conclude by briefly discussing its implications.
429
- Kim, Chun-Hwey
- Journal of astronomy and space sciences
- 29, n.2
- pp.151-161
- 2012
- 원문 바로보기
An intensive analysis of 148 timings of V700 Cyg was performed, including our new timings and 59 timings calculated from the super wide angle search for planets (SWASP) observations, and the dynamical evidence of the W UMa W subtype binary was examined. It was found that the orbital period of the system has varied over approximately <TEX>$66^y$</TEX> in two complicated cyclical components superposed on a weak upward parabolic path. The orbital period secularly increased at a rate of <TEX>$+8.7({\pm}3.4){\times}10^{-9}$</TEX> day/year, which is one order of magnitude lower than those obtained by previous investigators. The small secular period increase is interpreted as a combination of both angular momentum loss (due to magnetic braking) and mass-transfer from the less massive component to the more massive component. One cyclical component had a <TEX>$20.^y3$</TEX> period with an amplitude of <TEX>$0.^d0037$</TEX>, and the other had a <TEX>$62.^y8$</TEX> period with an amplitude of <TEX>$0.^d0258$</TEX>. The components had an approximate 1:3 relation between their periods and a 1:7 ratio between their amplitudes. Two plausible mechanisms (i.e., the light-time effects [LTEs] caused by the presence of additional bodies and the Applegate model) were considered as possible explanations for the cyclical components. Based on the LTE interpretation, the minimum masses of 0.29 <TEX>$M_{\odot}$</TEX> for the shorter period and 0.50 <TEX>$M_{\odot}$</TEX> for the longer one were calculated. The total light contributions were within 5%, which was in agreement with the 3% third-light obtained from the light curve synthesis performed by Yang & Dai (2009). The Applegate model parameters show that the root mean square luminosity variations (relative to the luminosities of the eclipsing components) are 3 times smaller than the nominal value (<TEX>${\Delta}L/L_{p,s}{\approx}0.1$</TEX>), indicating that the variations are hardly detectable from the light curves. Presently, the LTE interpretation (due to the third and fourth stars) is preferred as the possible cause of the two cycling period changes. A possible evolutionary implication for the V700 Cyg system is discussed.
430
- Kim, Younkyu
- Journal of astronomy and space sciences
- 29, n.4
- pp.413-422
- 2012
- 원문 바로보기
In recent years, a number of missions have been planned and conducted worldwide on the planets such as Mars, which involves the unmanned robotic exploration with the use of rover. The rover is an important system for unmanned planetary exploration, performing the locomotion and sample collection and analysis at the exploration target of the planetary surface designated by the operator. This study investigates the development of mobility system for the rover ground model necessary to the planetary surface exploration for the benefit of future planetary exploration mission in Korea. First, the requirements for the rover mobility system are summarized and a new mechanism is proposed for a stable performance on rough terrain which consists of the passive suspension system with 8 wheeled double 4-bar linkage (DFBL), followed by the performance evaluation for the mechanism of the mobility system based on the shape design and simulation. The proposed mobility system DFBL was compared with the Rocker-Bogie suspension system of US space agency National Aeronautics and Space Administration and 8 wheeled mobility system CRAB8 developed in Switzerland, using the simulation to demonstrate the superiority with respect to the stability of locomotion. On the basis of the simulation results, a general system configuration was proposed and designed for the rover manufacture.