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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 19, Issue 4 - Dec 2002
Volume 19, Issue 3 - Sep 2002
Volume 19, Issue 2 - Jun 2002
Volume 19, Issue 1 - Mar 2002
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HALO EMISSION OF THE CAT’S EYE NEBULA, NGC 6543: SHOCK EXCITATION BY FAST STELLAR WINDS
Hyung, Siek ; Lee, Seong-Jae ;
Journal of Astronomy and Space Sciences, volume 19, issue 3, 2002, Pages 173~180
DOI : 10.5140/JASS.2002.19.3.173
Images taken with the Chandra X-ray telescope have for the the first time revealed the central, wind-driven, hot bubble (Chu et al. 2001), while Hubble Space Telescope (HST) WFPC2 images of the Cat's Eye nebula, NGC 6543, show that the temperature of the halo region of angular radius ~ 20", is much higher than that of the inner bright H II region. With the coupling of a photoionization calculation to a hydrodynamic simulation, we predict the observed 〔O III〕 line intensities of the halo region with the same O abundance as in the core H II region: oxygen abundance gradient does not appear to exist in the NGC 6543 inner halo. An interaction between a (leaky) fast stellar wind and halo gas may cause the higher excitation temperatures in the halo region and the inner hot bubble region observed with the Chandra X-ray telescope.
A ROLE OF PROTO-ACCRETION DISK: HEATING PROTO-PLANETS TO EVAPORATION
Chang, Heon-Young ; Choi, Chul-Sung ;
Journal of Astronomy and Space Sciences, volume 19, issue 3, 2002, Pages 181~186
DOI : 10.5140/JASS.2002.19.3.181
We study a role of the proto-accretion disk during the formation of the planetary system, which is motivated with recent X-ray observations. There is an observational correlation of the mass of extrasolar planets with their orbital period, which also shows the minimum orbital period. This is insufficiently accounted for by the selection effect alone. Besides, most of planetary formation theories predict the lower limit of semimajor axes of the planetary orbits around 0.01 AU. While the migration theory involving the accretion disk is the most favorable theory, it causes too fast migration and requires the braking mechanism to halt the planet~0.01 AU. The induced gap in the accretion disk due to the planet and/or the truncated disk are desperately required to stop the planet. We explore the planetary evaporation in the accretion disk as another possible scenario to explain the observational lack of massive close-in planets. We calculate the location where the planet is evaporated when the mass and the radius of the planet are given, and find that the evaporation location is approximately proportional to the mass of the planet as
and the radius of the planet as
. Therefore, we conclude that even the standard cool accretion disk becomes marginally hot to make the small planet evaporate at~0.01 AU. We discuss other auxiliary mechanisms which may provide the accretion disk with extra heats other than the viscous friction, which may consequently make a larger planet evaporate.
ROCHE MODEL AND ABSOLUTE DIMENSIONS OF THE ECLIPSING BINARY Y CAM WITH A PULSATING COMPONENT
Lee, J.W. ; Kim, C.H. ; Kim, S.L. ; Youn, J.H. ; Kwon, S.G. ;
Journal of Astronomy and Space Sciences, volume 19, issue 3, 2002, Pages 187~196
DOI : 10.5140/JASS.2002.19.3.187
We performed CCD photometric observations of the eclipsing binary Y Cam with a pulsating component, for 16 nights from November 2000 to May 2001 using a V filter attached to the 61-cm reflector at Sobaeksan Optical Astronomy Observatory. Our V light curve and Broglia & Marin's (1974) BV ones were analyzed with Mode 2 for a detached Roche model as well as Model 5 for a semi-detached one in the Wilson-Devinney code. From the analysis, we found the following results: 1) It is hardly discernible from only light curve synthesis which model between the detached and semi-detached ones is a real Roche model of Y Cam. 2) There exist the third light of about 2% and 3% in B and V light curves of Y Cam, respectively. 3) The light curve solution is immune from the light variation due to the pulsation of the primary component of Y cam. However, the detached model rather than the semi-detached one has slightly better fitted to the observations which were get rid of the pulsation effect. 4) The absolute dimensions of Y Cam were calculated for two Roche models.
NORAD TLE TYPE ORBIT DETERMINATION OF LEO SATELLITES USING GPS NAVIGATION SOLUTIONS
Cho, Chang-Hwa ; Lee, Byoung-Sun ; Lee, Jeong-Sook ; Kim, Jae-Hoon ; Choi, Kyu-Hong ;
Journal of Astronomy and Space Sciences, volume 19, issue 3, 2002, Pages 197~206
DOI : 10.5140/JASS.2002.19.3.197
NORAD Two Line Elements (TLE) are widely used for the increasing number of small satellite mission operations and analysis. However, due to the irregular periodicity of generation of the NORAD TLE, a new TLE that is independent of NORAD is required. A TLE type Orbit Determination (TLEOD) has been developed for the generation of a new TLE. Thus, the TLEOD system can provide an Antenna Control Unit (ACU) with the orbit determination result in the type of a TLE, which provides a simple interface for the commercialized ACU system. For the TLEOD system, NORAD SGP4 was used to make a new orbit determination system. In addition, a least squares method was implemented for the TLEOD system with the GPS navigation solutions of the KOMPSAT-1. Considering both the Orbit Propagation (OP) difference and the tendency of
value, the preferable span of the day in the observation data was selected to be 3 days. Through the OD with 3 days observation data, the OP difference was derived and compared with that of Mission Analysis and Planning (MAPS) for the KOMPSAT-1. It has the extent from 2 km after sit days to 4 km after seven days. This is qualified enough for the efficiency of an ACU in image reception and processing center of the KOMPSAT-2.
A STUDY ON THE PRESSURE BEHAVIOR INSIDE PROPELLANT LINE OF SATELLITE
Choi, Jin-Chul ; Kim, Jeong-Soo ;
Journal of Astronomy and Space Sciences, volume 19, issue 3, 2002, Pages 207~214
DOI : 10.5140/JASS.2002.19.3.207
One of the way to derive design parameters of the fuel feeding system in satellite propulsion system is to analyze unsteady flow of liquid propellant (hydrazine). During steady thruster firing the flow rate is constant: if a thruster valve is abruptly shut down among a set of thrusters, pressure spikes much higher than the initial tank pressure occur. This renders the fuel flow unsteady, and the fluid pressure and flow rate to oscillate. If the pressure spikes are high enough, there are possibilities that propellant explosively decomposes, thruster valves we damaged, and adiabatic detonation of the hydrazine propellant is potentially incurred. Reflected shockwaves could also affect the calibration and operation of the pressure transducers. These necessitate the analysis of unsteady flow in the propulsion system design, and pressure behavior inside the propellant line obtained through some governing parameter variation is presented in this work.
ELECTRICAL GROUND SUPPORT EQUIPMENT (EGSE) DESIGN FOR SMALL SATELLITE
Park, Jong-Oh ; Choi, Jong-Yoen ; Lim, Seong-Bin ; Kwon, Jae-Wook ; Youn, Young-Su ; Chun, Yong-Sik ; Lee, Sang-Seol ;
Journal of Astronomy and Space Sciences, volume 19, issue 3, 2002, Pages 215~224
DOI : 10.5140/JASS.2002.19.3.215
This paper describes EGSE design for the small satellite such like KOMPSAT-2 satellite. Recent design trend of small satellite and EGSE is to take short development time and less cost. For this purpose, the design for KOMPSAT-2 satellite and EGSE are not much modified from KOMPSAT-1 heritage. It means that it is able to be accommodated the verified hardware and software modules used in KOMPSAT-1 satellite program if possible. The objective of EGSE is to provide hardware and software for efficient electrical testing of integrated KOMPSAT-2 satellite in three general categories. (1) Simulators for ground testing (e.g. solar-simulation power, earth scenes, horizons and sun sensor). (2) Ground station type satellite data acquisition and processing test sets. (3) Overall control of satellite using hardline datum. In KOMPSAT (KOrea Multi-Purpose SATellite) program, KOMPSAT-2 EGSE was developed to support satellite integration and test activities. The KOMPSAT-2 EGSE was designed in parallel with satellite design. Consequently, the KOMPSAT-2 EGSE was based on the KOMPSAT-1 heritage since the spacecraft design followed the heritage. The KOMPSAT-2 baseline was elaborated by taking advantage of experience from KOMPSAT-1 program. The EGSE of KOMPSAT-2 design concept is generic modular design with preference in part selection with commercial off-the-shelf which were proven from KOMPSAT-1 programs, flexible/user friendly operational environment (graphical interface preferred), minimized new design and self test capability.
FEASIBILITY STUDY OF SYNTHETIC APERTURE RADAR - ADAPTABILITY OF THE PAYLOAD TO KOMPSAT PLATFORM
Kim, Young-Soo ; Lee, Sang-Ryool ;
Journal of Astronomy and Space Sciences, volume 19, issue 3, 2002, Pages 225~230
DOI : 10.5140/JASS.2002.19.3.225
Synthetic Aperture Radar (SAR) has been used for mapping the surface geomorphology of cloudy planets like Venus as well as the Earth. The cloud-free Mars is also going to be scanned by SAR in order to detect buried water channels and other features under the very shallow subsurface af the ground. According to the 'Mid and Long-term National Space Development Plan' of Korea, SAR satellites, in addition to the EO (Electro-Optical) satellites, are supposed to be developed in the frame of the KOMPSAT (Korean Multi-Purpose Satellite) program. Feasibility of utilizing a SAR payload on KOMPSAT platform has been studied by KARI in collaboration with Astrium U.K. The purpose of the ShR program is Scientific and Civil applications on the Earth. The study showed that KOMPSAT-2 platform can accommodate a small SAR like Astrium’s MicroSAR. In this paper, system aspects of the satellite design are presented, such as mission scenario, operation concept, and capabilities. The spacecraft design is also discussed and conclusion is followed.
THE ASTRONOMICAL INSTRUMENT, SO-GANUI INVENTED DURING KING SEJONG PERIOD
Journal of Astronomy and Space Sciences, volume 19, issue 3, 2002, Pages 231~242
DOI : 10.5140/JASS.2002.19.3.231
So-ganui, namely small simplified armillary sphere, was invented as an astronomical instrument by Lee Cheon, Jeong Cho, Jung In-Ji under 16 years’ rule of King Sejong. We collect records and observed data on So-ganui. It is designed to measure position of celestial sphere and to determine time. It also can be transformed equatorial to horizontal, and horizontal to equatorial coordinate. It can measure the right ascension, declination, altitude and azimuth. It is composed of Sayu-hwan (Four displacements), Jeokdo-hwan (Equato.ial dial), Baekgak-hwan (Ring with one hundred-interval quarters), Gyuhyeong (Sighting aliadade), Yongju (Dragon-pillar) and Bu (Stand). So-ganui was used conveniently portable surveying as well as astronomical instrument and possible to determine time during day and night.