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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 21, Issue 4 - Dec 2004
Volume 21, Issue 3 - Sep 2004
Volume 21, Issue 2 - Jun 2004
Volume 21, Issue 1 - Mar 2004
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DETERMINATIONS OF ITS ABSOLUTE DIMENSIONS AND DISTANCE BY THE ANALYSES OF LIGHT AND RADIAL-VELOCITY CURVES OF THE CONTACT BINARY - I. V417 Aquilae
Journal of Astronomy and Space Sciences, volume 21, issue 2, 2004, Pages 73~82
DOI : 10.5140/JASS.2004.21.2.073
New photometric and spectroscopic solutions of W-type overcontact binary V 417 Aql were obtained by solving the UBV light curves of Samec et al. (1997) and radial-velocity ones of Lu ＆ Rucinski (1999) with the 2003 version of the Wilson-Devinney binary code. In the light curve synthesis the light of a third-body, which Qian (2003) proposed, was considered and obtained about 2.7%, 2.2%, and 0.4% for U, B, and V bandpasses, respectively. The model with third-light is better fitted to eclipse parts than that with no third-light. Absolute dimensions of V417 Aql are determined from our solution as
, and the distance to it is deduced as about 216pc. Our distance is well consistent with that (204pc) derived from Rucinski ＆ Duerbeck's (1997) relation,
(log P, B-V), but is more distant than that (131
40pc) determined by the Hipparcos trigonometric parallax. The difference may result from the relatively large error of Hipparcos parallax for V 417 Aql.l.
SMALL MASS RATIO CONTACT BINARY GR Vir AND HV Aqr
Journal of Astronomy and Space Sciences, volume 21, issue 2, 2004, Pages 83~92
DOI : 10.5140/JASS.2004.21.2.083
The absolute dimensions of low mass contact binary, GR Vir and HV Aqr were obtained using WD program from the published spectroscopic and photometric observational data. The evolutionary status of this type of system including GR Vir and HV Aqr has been considered. The primary stars of low mass contact binary system were located on the Terminal Age Main-sequence and secondary stars were located under the Zero Age Main-sequence in H-R diagram.
CHARACTERISTIC SOLAR WIND DYNAMICS ASSOCIATED WITH GEOSYNCHRONOUS RELATIVISTIC ELECTRON EVENTS
Kim, Hee-Jeong ; Lee, Dae-Young ;
Journal of Astronomy and Space Sciences, volume 21, issue 2, 2004, Pages 93~100
DOI : 10.5140/JASS.2004.21.2.093
We have investigated characteristic solar wind dynamics associated with relativistic electron events at geosynchronous orbit. Most of the events for April, 1999 through December, 2002 are found to be accompanied by a prolonged solar quiet period which is characterized as low solar wind density, weak interplanetary magnetic field (IMF), and fast alfvenic fluctuations in IMF
. In a typical relativistic event, electron fluxes begin to increase by orders of magnitude when solar wind parameters drop to low values (e.g.,
∼5 nT) after sharp peaks. Then the elevated electron fluxes stay at the high level during the solar quiet period. This observation may suggest the following scenario for the occurrence of a geosynchronous relativistic event: (ⅰ) Quiet solar winds can yield a stable and more dipole-like magnetospheric configurations in which the geosynchronous orbit locates well inside the trapping boundary of the energetic electrons. (ⅱ) If a large population of MeV electrons are generated (by whatever acceleration process(es)) in the inner magnetosphere, they can be trapped and effectively accumulated to a high intensity. (ⅲ) The high electron flux can persist for a number of days in the geosynchronous region as long as the solar wind dynamics stays quiet. Therefore the scenario indicates that the occurrence of a relativistic event would be a result of a delicate balance between the effects of electron acceleration and loss. In addition, the sensitive dependence of a relativistic event on the solar wind conditions makes the prediction of solar wind variability as important as understanding of electron acceleration processes in the forecast of a relativistic event.
CHARACTERISTICS OF ATMOSPHERIC WAVES OBSERVED FROM AIRGLOW MEASUREMENTS IN THE NORTHERN HIGH-LATITUDE
Won, Yong-In ; Lee, Bang-Yong ; Kwon, Soon-Chul ;
Journal of Astronomy and Space Sciences, volume 21, issue 2, 2004, Pages 101~108
DOI : 10.5140/JASS.2004.21.2.101
The terrestrial nightglow emission in near infrared region were obtained using a Fourier Transform Spectrometer(FTS) at Esrange, Sweden (
E) and the OH(4- 2) bands were used to derive temperature and airglow emission rate of the upper mesosphere. For this study, we analyzed data taken during winter of 2001/2002 and performed spectral analysis to retrieve wave information. From the Lomb-Scargle spectral analysis to the measured temperatures, dominant oscillations at various periods near tidal frequency are found. Most commonly observed waves are 4, 6, and 8 hour oscillations. Because of periods and persistence, the observed oscillations are most likely of tidal origin, i.e. zonally symmetric tides which are known to have their maximum amplitudes at the pole.
TIME SYNCHRONIZATION STRATEGY BETWEEN ON-BOARD COMPUTER AND FIMS ON STSAT-1
Journal of Astronomy and Space Sciences, volume 21, issue 2, 2004, Pages 109~120
DOI : 10.5140/JASS.2004.21.2.109
STSAT-1 was launched on sep. 2003 with the main payload of Far Ultra-violet Imaging Spectrograph(FIMS). The mission of FIMS is to observe universe and aurora. In this paper, we suggest a simple and reliable strategy adopted in STSAT-1 to synchronize time between On-board Computer(OBC) and FIMS. For the characteristics of STSAT-1, this strategy is devised to maintain reliability of satellite system and to reduce implementation cost by using minimized electronic circuits. We suggested two methods with different synchronization resolutions to cope with unexpected faults in space. The backup method with low resolution can be activated when the main has some problems.
A CONSTRUCTION OF THE REAL TIME MONITORING SYSTEM OF THE SOLAR RADIO DISTURBANCE 1. THE CONTROL SYSTEM OF THE RADIO TELESCOPE
Journal of Astronomy and Space Sciences, volume 21, issue 2, 2004, Pages 121~128
DOI : 10.5140/JASS.2004.21.2.121
As the first step of the real time monitoring system of the solar radio disturbance, we constructed the control system of the solar radio telescope. An 1.8m antenna built by Korean Astronomy Observatory has been used, and the observed radio flux is transformed to the digital signal by the powermeter. We have also developed a computer program CBNUART in order to control the telescope system and the powermeter. As the sun rises, the telescope begins to observe the sun, and ends the observation automatically at sunset. The CBNUART enables the telescope automatically to go to the position of the sunrise for the beginning the observation and come back to the setposition after the ending the observation at the sunset. An active tracking routine is adopted in order to improve the tracking accuracy of the control system, and we used an optical telescope equipped in front of the antenna for control test. The tracking test shows that our control system can track with the accuracy of arc seconds, and the 50 minute pointing test shows that the pointing accuracy of right ascension and declination are 1.12 and 0.08 arc minutes respectively.
A STUDY ON THE IMPROVEMENT OF NEAR-REAL TIME GPS PHASE DATA PROCESSING ALGORITHM
Journal of Astronomy and Space Sciences, volume 21, issue 2, 2004, Pages 129~140
DOI : 10.5140/JASS.2004.21.2.129
KAO(Korea Astronomy Observatory) GPS group has developed an iRTK system as a near-real time positioning system using GPS carrier phase data. We focused on improving the accuracy of positioning through the updated capability of data processing of KAO's iRTK system using low-cost L1 carrier phase receiver. The accuracy of a positioning was demonstrated by Extended Kalman filter. Experiments were accomplished using from 30m to 20km baselines. Within 10km, the positioning accuracy was improved by approximately 50-70% to the previous study using one minute observable data. However, it took two minutes to obtain 1m level positioning accuracy at 20km point. We expect that the developed iRTK system can be applied to the various fields of GPS in near-real time positioning.
NOVEL CNC GRINDING PROCESS CONTROL FOR NANOMETRIC SURFACE ROUGHNESS FOR ASPHERIC SPACE OPTICAL SURFACES
Journal of Astronomy and Space Sciences, volume 21, issue 2, 2004, Pages 141~152
DOI : 10.5140/JASS.2004.21.2.141
Optics fabrication process for precision space optical parts includes bound abrasive grinding, loose abrasive lapping and polishing. The traditional bound abrasive grinding with bronze bond cupped diamond wheel leaves the machine marks of about
rms in height and the subsurface damage of about 1
rms in height to be removed by subsequent loose abrasive lapping. We explored an efficient quantitative control of precision CNC grinding. The machining parameters such as grain size, work-piece rotation speed and feed rate were altered while grinding the work-piece surfaces of 20-100 mm in diameter. The input grinding variables and the resulting surface quality data were used to build grinding prediction models using empirical and multi-variable regression analysis. The effectiveness of such grinding prediction models was then examined by running a series of precision CNC grinding operation with a set of controlled input variables and predicted output surface quality indicators. The experiment achieved the predictability down to
nm in height and the surface roughness down to 36 nm in height. This study contributed to improvement of the process efficiency reaching directly the polishing and figuring process without the need for the loose abrasive lapping stage.
LAUNCH OPPORTUNITIES FOR JUPITER MISSIONS USING THE GRAVITY ASSIST
Journal of Astronomy and Space Sciences, volume 21, issue 2, 2004, Pages 153~166
DOI : 10.5140/JASS.2004.21.2.153
Interplanetary trajectories using the gravity assists are studied for future Korean interplanetary missions. Verifications of the developed softwares and results were performed by comparing data from ESA's Mars Express mission and previous results. Among the Jupiter exploration mission scenarios, multi-planet gravity assist mission to Jupiter (Earth-Mars-Earth-Jupiter Gravity Assist, EMEJGA trajectory) requires minimum launch energy (
) of 29.231
with 4.6 years flight times. Others, such as direct mission and single-planet(Mars) gravity assist mission, requires launch energy (
) of 75.656
with 2.98 years flight times and 63.590
with 2.33 years flight times, respectively. These results show that the planetary gravity assists can reduce launch energy, while EMEJGA trajectory requires the longer flight time than the other missions.