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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Astronomy and Space Sciences
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The Korean Space Science Society
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Volume & Issues
Volume 25, Issue 4 - Dec 2008
Volume 25, Issue 3 - Sep 2008
Volume 25, Issue 2 - Jun 2008
Volume 25, Issue 1 - Mar 2008
Selecting the target year
Cepstrum Analysis of Terrestrial Impact Crater Records
Chang, Heon-Young ; Han, Cheong-Ho ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 71~76
DOI : 10.5140/JASS.2008.25.2.071
Study of terrestrial impact craters is important not only in the field of the solar system formation and evolution but also of the Galactic astronomy. The terrestrial impact cratering record recently has been examined, providing short- and intermediate-term periodicities, such as,
Myrs. The existence of such a periodicity has an implication in the Galactic dynamics, since the terrestrial impact cratering is usually interpreted as a result of the environmental variation during solar orbiting in the Galactic plane. The aim of this paper is to search for a long-term periodicity with a novel method since no attempt has been made so far in searching a long-term periodicity in this research field in spite of its great importance. We apply the cepstrum analysis method to the terrestrial impact cratering record for the first time. As a result of the analysis we have found noticeable peaks in the Fourier power spectrum appear ing at periods of
Myrs, which seem in a simple resonance with the revolution period of the Sun around the Galactic center. Finally we briefly discuss its implications and suggest theoretical study be pursued to explain such a long-term periodicity.
Light Curve Analyses of the Eclipsing Binaries in the Small Magellan Cloud
Kang, Young-Woon ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 77~86
DOI : 10.5140/JASS.2008.25.2.077
Large survey observations such as the EROS, the MACHO and the OGLE projects have discovered a large number of eclipsing binaries in the extra galaxies and published their light curves. The light curves of the eclipsing binaries provide fundamental stellar parameters so that accumulation of the light curves will be very useful for the research of the stellar astronomy. However it requires a lot of time to analyze the light curves. Therefore we developed new method to analyze the large number of light curves in the relatively short time period and found the photometric solution by analyzing the light curves of 20 eclipsing binaries, whose mass ratio can be determined by photometic method, in the Small Magellan Cloud.
BVRI Standardization of the CCD Photometric System of Sobaeksan Optical Astronomy Observatory
Jeong, Jang-Hae ; Kim, Chun-Hwey ; Lee, Yong-Sam ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 87~100
DOI : 10.5140/JASS.2008.25.2.087
A total of 792 CCD images of V523 Cas were obtained on four nights of Jan. 2003 with the bvri CCD photometric system attached to a 61cm reflector of Sobaeksan Optical Astronomy Observatory (SOAO). The 17 standard stars in the images were used to establish transformation relations between our bvri system and the standard Johnson-Cousins BVRI system. We derived the tentative equations of transformation between two photometric systems as follows; V
Seasonal and Yearly Variations of Atmospheric Extinction Coefficient at Campus Station of Chungbuk National University Observatory from 2005 to 2007
Kim, Chun-Hwey ; Cha, Sang-Mok ; Choi, Young-Jae ; Song, Mi-Hwa ; Park, Jang-Ho ; Won, Jang-Hee ; Yim, Jin-Sun ; Cho, Myung-Shin ; Park, Eun-Mi ; Jeong, Jang-Hae ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 101~112
DOI : 10.5140/JASS.2008.25.2.101
Systematic CCD observations of times of minimum lights for eclipsing binaries has been carried out from 2002 to 2007 at Campus Station of Chungbuk National University Observatory which is located in Cheongju city, Korea. As a by-product of our observations, photometric data for stars in CCD images taken from 2005 to 2007 were used to determine 1st order atmospheric extinction coefficient (hereafter AEC) and seasonal and yearly variations of the AECs were studied. Total nights used for determination of AECs were 57 days in 2005, 51 days in 2006, and 63 days in 2007. As a result the annual mean value of the AECs per air mass is calculated as
for 2006, and
for 2007. These values show that the AECs and their standard deviations are two and four times, respectively, larger than those of normal observatories which are not located near large cities. Annual comparison between concentration of atmospheric fine dust and coefficient of atmospheric extinction show strong correlation between two quantities of which time variations show similar patterns. The AECs for the east sky show larger than those for the west sky. It can be easily understood by the reasonable possibility that air pollutants remain more in the east sky than in the west because the east area of Cheongju city has been more developed than the west one. In conclusion the atmospheric extinction of the night sky of Cheongju city has an annual trend of increase of
implying that it may take only about 13 years for Cheongju city to have 2 times brighter night sky than the present one. Our study highlights that variations of AEC can be used as an important indicator of air pollution to monitor night skies.
Statistical Characteristics of Solar Wind Dynamic Pressure Enhancements During Geomagnetic Storms
Choi, C.R. ; Kim, K.C. ; Lee, D.Y. ; Kim, J.H. ; Lee, E. ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 113~128
DOI : 10.5140/JASS.2008.25.2.113
Solar wind dynamic pressure enhancements are known to cause various types of disturbances to the magnetosphere. In particular, dynamic pressure enhancements may affect the evolution of magnetic storms when they occur during storm times. In this paper, we have investigated the statistical significance and features of dynamic pressure enhancements during magnetic storm times. For the investigation, we have used a total of 91 geomagnetic storms for 2001-2003, for which the Dst minimum
is below -50 nT. Also, we have imposed a set of selection criteria for a pressure enhancement to be considered an event: The main selection criterion is that the pressure increases by
within 30 min and remains to be elevated for 10 min or longer. For our statistical analysis, we define the storm time to be the interval from the main Dst decrease, through
, to the point where the Dst index recovers by 50%. Our main results are summarized as follows.
81% of the studied storms indicate at least one event of pressure enhancements. When averaged over all the 91 storms, the occurrence rate is
4.5 pressure enhancement events per storm and
0.15 pressure enhancement events per hour. (ii) The occurrence rate of the pressure enhancements is about three times higher for CME-driven storm times than for CIR-driven storm times. (iii) Only 21.1% of the pressure enhancements show a clear association with an interplanetary shock. (iv) A large number of the pressure enhancement events are accompanied with a simultaneous change of IMF
: For example, 73.5% of the pressure enhancement events are associated with an IMF change of either
. This last finding suggests that one should consider possible interplay effects between the simultaneous pressure and IMF changes in many situations.
Response of the Geomagnetic Activity Indices to the Solar Wind Parameters
Ahn, Byung-Ho ; Park, Yoon-Kyung ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 129~138
DOI : 10.5140/JASS.2008.25.2.129
This study attempts to show how the geomagnetic indices, AU, AL and Dst, respond to the interplanetary parameters, more specifically, the solar wind electric field VBz during southward interplanetary magnetic field (IMF) period. The AU index does not seem to respond linearly to the variation of southward IMF. Only a noticeable correlation between the AU and VBz is shown during summer, when the ionospheric conductivity associated with the solar EUV radiation is high. It is highly likely that the effect of electric field on the eastward electrojet intensification is only noticeable whenever the ionospheric conductivity is significantly enhanced during summer. Thus, one should be very cautious in employing the AU as a convection index during other seasons. The AL index shows a significantly high correlation with VBz regardless of season. Considering that the auroral electrojet is the combined result of electric field and ionospheric conductivity, the intensification of these two quantities seems to occur concurrently during southward IMF period. This suggests that the AL index behaves more like a convection index rather than a substorm index as far as hourly mean AL index is concerned. Contrary to the AU index, the AL index does not register the maximum value during summer for a given level of VBz. It has something to do with the findings that discrete auroras are suppressed in sunlight hemisphere (Newell et al. 1996), thus reducing the ionospheric conductivity during summer. As expected, the Dst index tends to become more negative as VBz gets intensified. However, the Dst index (nT) is less than or equal to 15VBz(mV/m) + 50(Bz < 0). It indicates that VBz determines the lower limit of the storm size, while another factor(s), possibly substorm, seems to get further involved in intensifying storms. Although it has not been examined in this study, the duration of southward IMF would also be a factor to be considered in determining the size of a storm.
Quantitative Evaluation of Energy Coupling between Quasi-Periodic Substorms and High-Speed Coronal Streams
Park, M.Y. ; Lee, D.Y. ; Kim, K.C. ; Choi, C.R. ; Park, K.S. ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 139~148
DOI : 10.5140/JASS.2008.25.2.139
It has been known that high-speed solar wind streams associated with coronal holes lead to quasi-periodic substorms that occur approximately every
hours. In this paper we examined 222 repetitive substorms that occurred during high-speed stream periods in July through December in 2003 to quantitatively determine a range of energy input from the solar wind into the magnetosphere between two consecutive substorms. For this study, we have used the Akasofu
-parameter to time-integrate it for the interval between two consecutive substorms, and have applied this method to the 222 substorms. We find that the average amount of solar wind input energy between two adjacent substorms is
and about 85% out of the 222 substorms occur after an energy input of
. Based on these results, we suggest that it is not practical to predict when a sub storm will occur after a previous one occurs purely based on the solar wind-magnetosphere energy coupling. We provide discussion on several possible factors that may affect determining substorm onset times during high-speed streams.
Magnetic Cloud and its Interplanetary Shock Sheath as a Modulator of the Cosmic Ray Intensity
Oh, Su-Yeon ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 149~156
DOI : 10.5140/JASS.2008.25.2.149
Forbush Decreases (FDs) are representative events of abrupt decrease in galactic cosmic ray intensity. They are known to be strongly associated with solar wind events such as interplanetary shock (IP shock) and magnetic cloud (MC). In order to examine effectiveness of the MC on FDs, I studied the 44 MCs that occurred during the 2 years from 1998 to 1999 and investigated the properties of interplanetary magnetic field (IMF) and solar wind. As a result, I found that 11 out of 44 MCs are associated with the FDs. In particularly, it is noted that the FDs are driven by the IP shock sheaths which are associated with over 13 nT of IMF magnitude, 3 nT of IMF turbulence, and 550km/s of solar wind speed. This result indicates that magnetic cloud and its interplanetary shock sheath work as a modulator of the cosmic ray intensity.
Statistical Relationship between Sawtooth Oscillations and Geomagnetic Storms
Kim, Jae-Hun ; Lee, Dae-Young ; Choi, Cheong-Rim ; Her, Young-Tae ; Han, Jin-Wook ; Hong, Sun-Hak ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 157~166
DOI : 10.5140/JASS.2008.25.2.157
We have investigated a statistical relationship between sawtooth oscillations and geomagnetic storms during 2000-2004. First of all we selected a total of 154 geomagnetic storms based on the Dst index, and distinguished between different drivers such as Coronal Mass Ejection (CME) and Co-rotating Interaction Region (CIR). Also, we identified a total of 48 sawtooth oscillation events based on geosynchronous energetic particle data for the same 2000-2004 period. We found that out of the 154 storms identified, 47 storms indicated the presence of sawtooth oscillations. Also, all but one sawtooth event identified occurred during a geomagnetic storm interval. It was also found that sawtooth oscillation events occur more frequently for storms driven by CME
than for storms driven by CIR
. In addition, sawtooth oscillations occurred mainly
in the main phase of storms for CME-driven storms while they occurred mostly
during the storm recovery phase for CIR-driven storms. Next we have examined the average characteristics of the Bz component of IMF, and solar wind speed, which were the main components for driving geomagnetic storm. We found that for most of the sawtooth events, the IMF Bz corresponds to -15 to 0 nT and the solar wind speed was in the range of
. We found that there was a weak tendency that the number of teeth for a given sawtooth event interval was proportional to the southward IMF Bz magnitude.
Fuel Optimization for Low Earth Orbit Maintenance
Park, Yong-Jae ; Park, Sang-Young ; Kim, Young-Rok ; Choi, Kyu-Hong ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 167~180
DOI : 10.5140/JASS.2008.25.2.167
The resolution of Earth images taken from a satellite has close relation with satellite`s altitude. If a satellite has lower altitude, it gets a picture having better resolution. However the satellite will be exposed to heavier air drag and will spend more fuel to maintain its altitude for a desired mission. Therefore, in this study, the required fuel to maintain very low earth orbit(LEO) with severe air drag is analyzed using optimization method such as collocation method. The required fuel to maintain the low altitude has significantly increased as the mission altitude is lowered and the solar activity is maximized. This study also shows that the fuel reduced by increasing the period of the satellite maneuver is very small, and that slightly increasing the satellite`s mission altitude is much effective in reducing the amount of fuel to maintain its altitude. The calculated fuel to maintain very low earth orbit in this study would give useful information in planning the budget of fuel and cost for LEO satellites.
Optimal Design of Satellite Constellation Korean Peninsula Regions
Kim, Nam-Kyun ; Park, Sang-Young ; Kim, Young-Rok ; Choi, Kyu-Hong ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 181~198
DOI : 10.5140/JASS.2008.25.2.181
Designing satellite constellations providing partial coverage of certain regions becomes more important as small low-altitude satellites receives an increasing attention due to its cost-effectiveness analysis. Generally, Walker`s method is a standard constellation method for global coverage but not effective for partial coverage. The purpose of this study is to design optimal constellation of satellites for effective observation in Korean peninsula regions. In this study, a new constellation design method is presented for partial coverage, using direct control of satellites` orbital elements. And also, a ground repeating circular orbit is considered for each satellite`s orbit with the Earth oblateness effect. As the results, at least four satellites are required to observe the Korean peninsula regions effectively when minimum elevation angle is assumed as 12 degrees. The results from new method are better than those from the best Walker method. The proposed algorithm will be useful to design satellite constellation missions of Korea in future.
Astronomical Books and Charts in the Book of Bibliographie Coreenne
Lee, Ki-Won ; Yang, Hong-Jin ; Park, Myeong-Gu ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 199~226
DOI : 10.5140/JASS.2008.25.2.199
We investigate astronomical materials listed in the book of Bibliographie Coreenne written by Maurice Courant. He classified ancient Korean books into nine Divisions (部) and thirty six Classes (類), and published them as three volumes (ranging from 1894 to 1896) and one supplement (in 1901). In total, 3,821 books including astronomical ones are listed together with information on physical size, possessional place, bibliographical note, and so forth. Although this book is an essential one in the field of Korea bibliography and contains many astronomical materials such as Cheon-Mun-Ryu-Cho 天文類抄, Si-Heon-Seo 時憲書, and Cheon-Sang-Yeol-Cha-Bun-Ya-Ji-Do 天象列次分野之圖, it has not been well known to the public nor to astronomical society. Of 3,821 catalogues, we found that about 50 Items (種) are related to astronomy or astrology, and verified that most of them are located in the Kyujanggak Royal Library 奎章閣. We also found an unknown astronomical chart, Hon-Cheon-Chong-Seong-Yeol-Cha-Bun-Ya-Ji-Do 渾天總星列次分野之圖. Because those astronomical materials are not well known to international astronomical community and there have been few studies on the materials in Korea, we here introduce and review them, particularly with the astronomical viewpoint.
Preliminary Design of Monitoring and Control Subsystem for GNSS Ground Station
Jeong, Seong-Kyun ; Lee, Jae-Eun ; Park, Han-Earl ; Lee, Sang-Uk ; Kim, Jae-Hoon ;
Journal of Astronomy and Space Sciences, volume 25, issue 2, 2008, Pages 227~238
DOI : 10.5140/JASS.2008.25.2.227
GNSS (Global Navigation Satellite System) Ground Station monitors navigation satellite signal, analyzes navigation result, and uploads correction information to satellite. GNSS Ground Station is considered as a main object for constructing GNSS infra-structure and applied in various fields. ETRI (Electronics and Telecommunications Research Institute) is developing Monitoring and Control subsystem, which is subsystem of GNSS Ground Station. Monitoring and Control subsystem acquires GPS and Galileo satellite signal and provides signal monitoring data to GNSS control center. In this paper, the configurations of GNSS Ground Station and Monitoring and Control subsystem are introduced and the preliminary design of Monitoring and Control subsystem is performed. Monitoring and Control subsystem consists of data acquisition module, data formatting and archiving module, data error correction module, navigation solution determination module, independent quality monitoring module, and system operation and maintenance module. The design process uses UML (Unified Modeling Language) method which is a standard for developing software and consists of use-case modeling, domain design, software structure design, and user interface structure design. The preliminary design of Monitoring and Control subsystem enhances operation capability of GNSS Ground Station and is used as basic material for detail design of Monitoring and Control subsystem.