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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 28, Issue 4 - Dec 2011
Volume 28, Issue 3 - Sep 2011
Volume 28, Issue 2 - Jun 2011
Volume 28, Issue 1 - Mar 2011
Selecting the target year
Latitudinal Distribution of Sunspots Revisited
Cho, Il-Hyun ; Chang, Heon-Young ;
Journal of Astronomy and Space Sciences, volume 28, issue 1, 2011, Pages 1~7
DOI : 10.5140/JASS.2011.28.1.001
Characteristics of latitude variations of sunspots in the northern and southern hemispheres are investigated using the daily sunspot area and its latitude during the period from 1874 to 2009. Solar magnetic activity is portrayed in the form of sunspot, regions of concentrated fresh magnetic fields observed on the surface of the Sun. By defining center-of-latitude (COL) as an area-weighted latitude, we find that COL is not monotonically decreasing as commonly assumed. In fact, small humps (or short plateaus) between solar minima can be seen around every solar maxima. We also find that when the northern (southern) hemisphere is magnetically dominant, COL is positive (negative), except the solar cycle 23, which may give a hint that these two phenomena are consistently regulated by one single mechanism. As a result of periodicity analysis, we find that several significant periodicities, such as, of ~5.5, ~11, ~49, and ~167 years.
Long-Term Variation of the Spin Period of a Magnetic Cataclysmic Variable, MU Camelopardalis
Yun, A-Mi ; Kim, Yong-Gi ; Choi, Chul-Sung ;
Journal of Astronomy and Space Sciences, volume 28, issue 1, 2011, Pages 9~12
DOI : 10.5140/JASS.2011.28.1.009
Results of an analysis of 11 nights of R-filter CCD photometry data of an intermediate polar MU Camelopardalis (MU Cam) obtained at the Korean 1.0 m telescope at Mt. Lemmon are reported. After checking the spin period with our data,
, we compiled the reported data of maxima timing and an O-C diagram analysis has been carried out to understand the spin period variation. A significant spin period variation was detected, and fitting the O-C points to a cubic parabola led to an ephemeris of
. The torque experienced by the magnetic compact star accreting in a disk is estimated as
in a simple approximation in order to show how important monitoring the period variation is. Thus we conclude that monitoring the long-term spin period variation will help to understand the physical condition of magnetic compact stars.
Observations of the CH
E Line Toward the Sgr B2 Region
Minh, Young-Chol ; Kim, Sang-Joon ;
Journal of Astronomy and Space Sciences, volume 28, issue 1, 2011, Pages 13~16
DOI : 10.5140/JASS.2011.28.1.013
E transition was observed toward the Sgr B2 region, including the Principal Cloud and its surroundings. This methanol transition shows an extended emission along the 2'N cloud, which is believed to be colliding with the Principal Cloud and may trigger the massive star formation in this cloud. This extended methanol emission may also suggest that the 2'N cloud is under shocks. We derive total methanol column density
toward the peak position of the extended emission. The fractional abundance of methanol is about 10.9, relative to the estimated total
abundance, which is similar to the methanol abundances in quiet gas phase.
Martian Bow Shock and Magnetic Pile-Up Barrier Formation Due to the Exosphere Ion Mass-Loading
Kim, Eo-Jin ; Sohn, Jong-Dae ; Yi, Yu ; Ogino, Tatsuki ; Lee, Joo-Hee ; Park, Jae-Woo ; Song, Young-Joo ;
Journal of Astronomy and Space Sciences, volume 28, issue 1, 2011, Pages 17~26
DOI : 10.5140/JASS.2011.28.1.017
Bow shock, formed by the interaction between the solar wind and a planet, is generated in different patterns depending on the conditions of the planet. In the case of the earth, its own strong magnetic field plays a critical role in determining the position of the bow shock. However, in the case of Mars of which has very a small intrinsic magnetic field, the bow shock is formed by the direct interaction between the solar wind and the Martian ionosphere. It is known that the position of the Martian bow shock is affected by the mass loading-effect by which the supersonic solar wind velocity becomes subsonic as the heavy ions originating from the planet are loaded on the solar wind. We simulated the Martian magnetosphere depending on the changes of the density and velocity of the solar wind by using the three-dimensional magnetohydrodynamic model built by modifying the comet code that includes the mass loading effect. The Martian exosphere model of was employed as the Martian atmosphere model, and only the photoionization by the solar radiation was considered in the ionization process of the neutral atmosphere. In the simulation result under the normal solar wind conditions, the Martian bow shock position in the subsolar point direction was consistent with the result of the previous studies. The three-dimensional simulation results produced by varying the solar wind density and velocity were all included in the range of the Martian bow shock position observed by Mariner 4, Mars 2, 3, 5, and Phobos 2. Additionally, the simulation result also showed that the change of the solar wind density had a greater effect on the Martian bow shock position than the change of the solar wind velocity. Our result may be useful in analyzing the future observation data by Martian probes.
Geosynchronous Magnetic Field Response to Solar Wind Dynamic Pressure
Park, Jong-Sun ; Kim, Khan-Hyuk ; Lee, Dong-Hun ; Lee, En-Sang ; Jin, Ho ;
Journal of Astronomy and Space Sciences, volume 28, issue 1, 2011, Pages 27~36
DOI : 10.5140/JASS.2011.28.1.027
The present study examines the morning-afternoon asymmetry of the geosynchronous magnetic field strength on the dayside (magnetic local time [MLT] = 06:00~18:00) using observations by the Geostationary Operational Environmental Satellites (GOES) over a period of 9 years from February 1998 to January 2007. During geomagnetically quiet time (Kp < 3), we observed that a peak of the magnetic field strength is skewed toward the earlier local times (11:07~11:37 MLT) with respect to local noon and that the geosynchronous field strength is larger in the morning sector than in the afternoon sector. That is, there is the morning-afternoon asymmetry of the geosynchronous magnetic field strength. Using solar wind data, it is confirmed that the morning-afternoon asymmetry is not associated with the aberration effect due to the orbital motion of the Earth about the Sun. We found that the peak location of the magnetic field strength is shifted toward the earlier local times as the ratio of the magnetic field strength at MLT = 18 (B-dusk) to the magnetic field strength at MLT = 06 (B-dawn) is decreasing. It is also found that the dawn-dusk magnetic field median ratio, B-dusk/B-dawn, is decreasing as the solar wind dynamic pressure is increasing. The morning-afternoon asymmetry of the magnetic field strength appears in Tsyganenko geomagnetic field model (TS-04 model) when the partial ring current is included in TS-04 model. Unlike our observations, however, TS-04 model shows that the peak location of the magnetic field strength is shifted toward local noon as the solar wind dynamic pressure grows in magnitude. This may be due to that the symmetric magnetic field associated with the magnetopause current, strongly affected by the solar wind dynamic pressure, increases. However, the partial ring current is not affected as much as the magnetopause current by the solar wind dynamic pressure in TS-04 model. Thus, our observations suggest that the contribution of the partial ring current at geosynchronous orbit is much larger than that expected from TS-04 model as the solar wind dynamic pressure increases.
The Comparison of the Classical Keplerian Orbit Elements, Non-Singular Orbital Elements (Equinoctial Elements), and the Cartesian State Variables in Lagrange Planetary Equations with J
Perturbation: Part I
Jo, Jung-Hyun ; Park, In-Kwan ; Choe, Nam-Mi ; Choi, Man-Soo ;
Journal of Astronomy and Space Sciences, volume 28, issue 1, 2011, Pages 37~54
DOI : 10.5140/JASS.2011.28.1.037
Two semi-analytic solutions for a perturbed two-body problem known as Lagrange planetary equations (LPE) were compared to a numerical integration of the equation of motion with same perturbation force. To avoid the critical conditions inherited from the configuration of LPE, non-singular orbital elements (EOE) had been introduced. In this study, two types of orbital elements, classical Keplerian orbital elements (COE) and EOE were used for the solution of the LPE. The effectiveness of EOE and the discrepancy between EOE and COE were investigated by using several near critical conditions. The near one revolution, one day, and seven days evolutions of each orbital element described in LPE with COE and EOE were analyzed by comparing it with the directly converted orbital elements from the numerically integrated state vector in Cartesian coordinate. As a result, LPE with EOE has an advantage in long term calculation over LPE with COE in case of relatively small eccentricity.
Precision Assessment of Near Real Time Precise Orbit Determination for Low Earth Orbiter
Choi, Jong-Yeoun ; Lee, Sang-Jeong ;
Journal of Astronomy and Space Sciences, volume 28, issue 1, 2011, Pages 55~62
DOI : 10.5140/JASS.2011.28.1.055
The precise orbit determination (POD) of low earth orbiter (LEO) has complied with its required positioning accuracy by the double-differencing of observations between International GNSS Service (IGS) and LEO to eliminate the common clock error of the global positioning system (GPS) satellites and receiver. Using this method, we also have achieved the 1 m positioning accuracy of Korea Multi-Purpose Satellite (KOMPSAT)-2. However double-differencing POD has huge load of processing the global network of lots of ground stations because LEO turns around the Earth with rapid velocity. And both the centimeter accuracy and the near real time (NRT) processing have been needed in the LEO POD applications--atmospheric sounding or urgent image processing--as well as the surveying. An alternative to differential GPS for high accuracy NRT POD is precise point positioning (PPP) to use measurements from one satellite receiver only, to replace the broadcast navigation message with precise post processed values from IGS, and to have phase measurements of dual frequency GPS receiver. PPP can obtain positioning accuracy comparable to that of differential positioning. KOMPSAT-5 has a precise dual frequency GPS flight receiver (integrated GPS and occultation receiver, IGOR) to satisfy the accuracy requirements of 20 cm positioning accuracy for highly precise synthetic aperture radar image processing and to collect GPS radio occultation measurements for atmospheric sounding. In this paper we obtained about 3-5 cm positioning accuracies using the real GPS data of the Gravity Recover and Climate Experiment (GRACE) satellites loaded the Blackjack receiver, a predecessor of IGOR. And it is important to reduce the latency of orbit determination processing in the NRT POD. This latency is determined as the volume of GPS measurements. Thus changing the sampling intervals, we show their latency to able to reduce without the precision degradation as the assessment of their precision.
The Precision Validation of the Precise Baseline Determination for Satellite Formation
Choi, Jong-Yeoun ; Lee, Sang-Jeong ;
Journal of Astronomy and Space Sciences, volume 28, issue 1, 2011, Pages 63~70
DOI : 10.5140/JASS.2011.28.1.063
The needs for satellite formation flying are gradually increasing to perform the advanced space missions in remote sensing and observation of the space or Earth. Formation flying in low Earth orbit can perform the scientific missions that cannot be realized with a single spacecraft. One of the various techniques of satellite formation flying is the determination of the precise baselines between the satellites within the formation, which has to be in company with the precision validation. In this paper, the baseline of Gravity Recovery and Climate Experiment (GRACE) A and B was determined with the real global positioning system (GPS) measurements of GRACE satellites. And baseline precision was validated with the batch and sequential processing methods using K/Ka-band ranging system (KBR) biased range measurements. Because the proposed sequential method validate the baseline precision, removing the KBR bias with the epoch difference instead of its estimation, the validating data (KBR biased range) are independent of the data validated (GPS-baseline) and this method can be applied to the real-time precision validation. The result of sequential precision validation was 1.5~3.0 mm which is similar to the batch precision validation.
Generation of Klobuchar Ionospheric Error Model Coefficients Using Fourier Series and Accuracy Analysis
Lee, Chang-Moon ; Park, Kwan-Dong ;
Journal of Astronomy and Space Sciences, volume 28, issue 1, 2011, Pages 71~77
DOI : 10.5140/JASS.2011.28.1.071
Ionospheric error modeling is necessary to create reliable global navigation satellite system (GNSS) signals using a GNSS simulator. In this paper we developed algorithms to generate Klobuchar coefficients
(n = 1, 2, 3, 4) for a GNSS simulator and verified accuracy of the algorithm. The eight Klobuchar coefficients were extracted from three years of global positioning system broadcast (BRDC) messages provided by International GNSS service from 2006 through 2008 and were fitted with Fourier series. The generated coefficients from our developed algorithms are referred to as Fourier Klobuchar model (FOKM) coefficients, while those coefficients from BRDC massages are named as BRDC coefficients. The correlation coefficient values between FOKM and BRDC were higher than 0.97. We estimated total electron content using the Klobuchar model with FOKM coefficients and compared the result with that from the BRDC model. As a result, the maximum root mean square was 1.6 total electron content unit.
A Study on the Operation Mechanism of Ongnu, the Astronomical Clock in Sejong Era
Kim, Sang-Hyuk ; Lee, Yong-Sam ; Lee, Min-Soo ;
Journal of Astronomy and Space Sciences, volume 28, issue 1, 2011, Pages 79~91
DOI : 10.5140/JASS.2011.28.1.079
Ongnu (Jade Clepsydra; also called Heumgyeonggaknu) is a water clock was made by Jang Yeong-sil in 1438. It is not only an automatic water clock that makes the sound at every hour on the hour by striking bell, drum and gong, but also an astronomical clock that shows the sun's movement over time. Ongnu's power mechanism used is a water-hammering method applied to automatic time-signal device. The appearance of Ongnu is modeled by Gasan (pasted-paper imitation mountain) and Binpungdo (landscape of farming work scene) is drawn at the foot of the mountain. The structure of Ongnu is divided into the top of the mountain, the foot of the mountain and the flatland. There located are sun-movement device, Ongnyeo (jade female immortal; I) and Four gods (shaped of animal-like immortals) at the top of the mountain, Sasin (jack hour) and Musa (warrior) at the foot of the mountain, and Twelve gods, Ongnyeo (II) and Gwanin on the flatland. In this study, we clearly and systematically understood the time-announcing mechanism of each puppet. Also, we showed the working mechanism of the sun-movement device. Finally, we completely established the 3D model of Ongnu based on this study.
The Design Concept of the First Mobile Satellite Laser Ranging System (ARGO-M) in Korea
Jo, Jung-Hyun ; Park, In-Kwan ; Lim, Hyung-Chul ; Seo, Yoon-Kyoung ; Yim, Hong-Seo ; Lee, Jin-Young ; Bang, Seung-Cheol ; Nah, Ja-Kyoung ; Kim, Kwang-Dong ; Jang, Jeong-Gyun ; Jang, Bi-Ho ; Park, Jang-Hyun ; Park, Jong-Uk ;
Journal of Astronomy and Space Sciences, volume 28, issue 1, 2011, Pages 93~102
DOI : 10.5140/JASS.2011.28.1.093
Korea Astronomy and Space Science Institute (KASI) launched the development project of two satellite laser ranging (SLR) systems in early 2008 after the government fund approval of the SLR systems in 2007. One mobile SLR system and one permanent SLR station will be developed with the completion of the project. The main objectives of these systems will be focused on the Space Geodetic researches. A system requirement review was held in the second half of the same year. Through the following system design review meeting and other design reviews, many unsolved technical and engineering issues would be discussed and resolved. However, the design of the mobile SLR system is a corner stone of whole project. The noticeable characteristics of Korea's first SLR system are 1) use of light weight main mirror, 2) design of compact optical assembly, 3) use of KHz laser pulse, 4) use of commercial laser generator, 5) remote operation capability, 6) automatic tracking, 7) state of art operation system, etc. In this paper, the major user requirement and pre-defined specification are presented and discussed.