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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 17, Issue 2 - Dec 2000
Volume 17, Issue 1 - Jun 2000
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METALLICITIES OF GLOBULAR CLUSTRES M3 AND M5 FROM VI CCD PHOTOMETRY
Sohn, Young-Jong ; Lee, Hyun-Chul ;
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 1~10
To derive the metallicities of M3 and M5, we used the shape of red giant branch, horizontal branch magnitude, and red giant branch bump on the (V-I)-V color magnitude diagrams. [Fe/H] values ranging -1.46 ∼ -1.69 for M3, and -1.00 ∼ -1.49 for M5 are estimated. These values are in good agreements with the previously determined ones. This result leads the morphologies of red giant and horizontal branches on the (V-I)-V color magnitude diagrams can be good indirect metallicity indicators of galactic globular clusters.
DUST SHELL MODELS FOR THE YOUNG STELLAR OBJECTS IN GIANT MOLECULAR CLOUDS
Song, In-Ok ; Suh, Kyung-Won ;
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 11~18
We have modeled the observed spectral energy distributions(SEDs) of young stellar objects (YSOs) in giant molecular clouds (GMCs). We propose the theoretical modles for the dust envelopes around YSOs. The YSOs in a GMC may share the same initial chemical composition. In this paper, we compare the model SEDs with the observations of the YSOs. Dust shells of the YSOs are composed of a mixture of astronomical silicate and graphite grains. We propose the models for the evolution of the GMCs comparing the shape of the SEDs on the IRAS 2-color diagram with the age.
PHOTOMETRIC OBSERVATIONS AND ANALYSIS OF THE W UMa TYPE ECLOPSING BINARY VW Cep
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 19~32
A total of 1,018 observations (509 in B, 509 in V) of the eclipsing binary VW Cep was made during 7 nights from April through May in 1999 at Sobaeksan Optical Astronomy Observatory, using the CCD camera attached to the 61cm telescope. A time of minimum light of HJD2451327.2282 was determined from our data, and we constructed BV light curves with the data. Using, Wilson-Devinney’s binary model, we analized the light curves. The absolute dimension of
of the VW Cep system were derived from our light curve solution and Kaszas et al. (1998) spectroscopic results.
CORRELATION IN THE GALACTIC PLANE
Kim, Yong-Gi ;
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 33~38
Synchrotron emission at 408 MHz and HI column density have been used to find an evidence for the relationship between the Galactic magnetic field and the gas density. The observational data of the brightness temperature and HI column density,
, near the galactic plane between galactic longitudes
show a clear linear correlation of
, where A(l, b)is a background and forground radiation at the galactic coordinate. We found
for the slope B, which describes the strength of the syncrotron radiation from the HI cloud, and agrees with the value for the MIlky Way obtained by Beuermann et al. (1985). We conclude therefore that a well defined nonthermal corelates with the HI column density originating from this HI cloud.
UV LINE EMISSIONS OF W UMa STARS
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 39~44
We reinvestigate UV line emissions of 44i Boo, W UMa, AW UMa and VW Cep, which are indicaters of chromospheric activity of these stars. C I, C II, C IV, Si IV lines show significant variation in orbital phase. Among those lines, the Line of C IV showed the strongest line flux. while other Si IV and N V lines showed relative low line intensities. 44i Boo emitted the strongest flux than other stars. UV light curves of target stars shoed UV maximum at phase around 0.2 an 0.8 Such UV emissions are generally believed to be observed at the active regions and contacting parts of the two stars due to the clear visibility at the phase 0.2 and 0.8. Total emissivity of four transitions lines lead to conclude that the activity of this region is 40 times larger than the quiet sun. It is obvious that the activity decrease according to increase period. We obtained also Mg II light curve of AW UMA and VW Cep. These stars showed more clearly phase-dependent light curves. We estimated effective temperature of two star, AW UMa and VW Cep, using by Mg II flux.
THE MEASUREMENT AND CORRECTION OF THE PERIODIC ERROR OF THE LX200-16 TELESCOPE DRIVING SYSTEM
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 45~52
We examined and corrected the periodic error of the LX200-16 Telescope driving system of Chungbuk National University Campus Observatory. Before correcting, the standard deviation of the periodic error in the direction of East-West was
=7."2. After correcting, we found that the periodic error was reduced to
DEVELOPMENT OF CCD IMAGING SYSTEM USING THERMOELECTRIC COOLING METHOD
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 53~66
We developed low light CCD imaging system using thermoelectric cooling method collaboration with a company to design a commercial model. It consists of Kodak KAF-0401E(768
512 pixels) CCD chip, thermoelectric module manufactured by Thermotek. This TEC system can reach an operative temperature of
. We employed an Uniblitz VS25s shutter and it has capability a minimum exposure time 80ms. The system components are an interface card using a Korea Astronomy Observatory (hereafter KAO) ISA bus controller, image acquisition with AD9816 chip, that is 12bit video processor. The performance test with this imaging system showed good operation within the initial specification of our design. It shows a dark current less than 0.4e-/pixel/sec at a temperature of
, a linearity 99.9
0.1%, gain 4.24e-/adu, and system noise is 25.3e-(rms). For low temperature CCD operation, we designed a TEC, which uses a one-stage peltier module and forced air heat exchanger. This TEC imaging system enables accurate photometry(
0.01mag) even though the CCD is not at 'conventional' cryogenic temperatures(140k). The system can be a useful instrument for any other imaging applications. Finally, with this system, we obtained several images of astronomical objects for system performance tests.
TOLERANCE ANALYSIS OF FIMS OPTICAL SYSTEM
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 67~76
Far-ultraviolet IMaging Spectrograph(FIMS) is the main payload of the first Korean scientific satellite, KAISTSTA-4, which will be launched in 2002. The optical system of FIMS consists of parabolic cylinder mirror, slit, ellipsoidal reflection grating, and MCP to get spatial information as well as spectral information. Allowed ranges of manufacturing and positioning error are derived for each optical components to achieve the astronomical goals. In the procedure, graphical simplification is dedicated to understand sensitivity table and to derive range and precision of manipulation for each optical component. The result shows that precision of
for linear and of 2' for angular manipulation fulfills optical requirements.
OVI EMISSION LINE DETECTION LIMIT OF FAR-ULTAVIOLET IMAGING SPECTROGRAPH
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 77~86
There have been a few attempts to measure diffuse line emission between 900
, and only in a limited number of sight lines has it been detected. The main contributions to the equilibrium radiative cooling curve between
are from the doublet of Ovi
in the FUV spectral region. There are several bright airglow lines which could interfere with attempts to observe the OVI lines. The nearest lines HI 1025
, OI 1027
have a combined intensity of about
/sr. In the present study, the detectability simulation of OVI doublet is performed using a Monte-Carlo technique and chi-square statistics. The analysis results are compared with the previous observations and with the predictions of several interstellar medium models, and are used to limit manufacturing and alignment errors of FIMS optical system.
THE RELATIVE CONTRIBUTIONS OF ELECTRIC FIELD AND IONOSPHERIC CONDUCTANCE TO THE AURORAL ELECTROJETS
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 87~98
We examine the relative contributions of the electric field and ionospheric conductance to the auroral electrojets. For this purpose we used magnetometer data obtained from the International Magnetospheric Study (IMS) meridian chains of observatories for March 17, 18, and 19, 1978. Based on the study by Allen & Kroehl (1975), we redefine the AU and AL indices by utilizing the magnetic disturbance data obtained from the AE stations located within limited magnetic local time (MLT) sectors; i.e.,
, respectively. The current densities of the eastward and westward electrojets are calculated based on the AU and AL indices thus defined. Under the assumption that the Hall conductance at the dusk sector is mainly caused by the solar EUV radiation, we estimate the electric field contributin to the AU index. Assuming further that electric field distributins at dawn and dusk sectors are comparable, it is also possible to estimate the contribution of the Hall conductance associated at the dusk sector is mainly caused by the solar EUV radiation, we estimate the electric field contribution to the AU index. Assuming further that electric field distributions at dawn and dusk sectors are comparable, it is also possible to estimate the contribution of the Hall conductance associated with auroral particle precipitation to the AL index. From this study it is noted that the electric fields and Hall conductances thus estimated show significant correlations with the AU and AL indices, respectively, suggesting that the AU and AL indices are closely associated with the directly driven and loading-unloading processes of substorms.
CIRCUIT MODEL SIMULATION FOR IONOSPHERIC PLASMA RESPONSE TO HIGH POTENTIAL SYSTEM
Rhee, Hwang-Jae ; Raitt, W.-John ;
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 99~106
When a deployed probe is biased by a high positive potential during a space experiment, the payload is induced to a negative voltage in order to balance the total current in the whole system. The return currents are due to the responding ions and secondary electrons on the payload surface. In order to understand the current collection mechanism, the process was simulated with a combination of resistor, inductor, and capacitor in SPICE program which was equivalent to the background plasma sheath. The simulation results were compared with experimental results from SPEAR-3 (Space Power Experiment Aboard Rocket-3). The return current curve in the simulation was compatible to the experimental result, and the simulation helped to predict the transient plasma response to a high voltage during the plasma sheath formation.
DEVELOPMENT OF SIMULATION TOOL FOR ORBITAL MOTION OF METEOROID STREAM PARTICLES
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 107~116
This paper presents the preliminary survey and simulation results of the prediction of Leonid stream's orbital motion. Based on the model survey on eject velocity and perturbation of meteoroid particles, a simulation program was developed and applied to orbital motion of Leonid stream. The Jones ejection distribution model was used to describe the particle's eject velocity and the orbital dynamic model includes perturbations of major planet's gravity. DE405 ephemeris file generated by Solar System Dynamics Group at Jet Propulsion Laboratory in NASA was used for the planet's ephemeris calculations. Solar radiation pressure were also considered in the simulation and 8th order Runge-Kutta algorithm was used a numerical integration method.
TELEMETRY TIMING ANALYSIS FOR IMAGE RECONSTRUCTION OF KOMPSAT SPACECRAFT
Lee, Jin-Ho ; Chang, Young-Keun ;
Journal of Astronomy and Space Sciences, volume 17, issue 1, 2000, Pages 117~122
The KOMPSAT(Korea Multi-Purpose SATellite) has two optical imaging instruments called EOC(Electro-Optical Camera) and OSMI (Ocean Scanning Multispectral Imager). The image data of these instruments are transmitted to ground station and restored correctly after post-processing with the telemetry data transfeered from KOMPSAT spacecraft. The major timing information of the KOMPSAT is OBT (On-Board Time) which is formatted by the on-board computer of the spacecraft, based on 1Hz sync. pulse coming from the GPS receiver involved. The OBT is transmitted to ground station with the house-keeping telemetry data of the spacecraft while it is distributed to the instruments via 1553B data bus for synchronization during imaging and formatting. The timing information contained in the spacecraft telemetry data would have direct relation to the image data of the instruments, which should be well explained to get a more accurate image. This paper addresses the timing analysis of the KOMPSAT spacecraft and instruments, including the gyro data timing analysis for the correct restoration of the EOC and OSMI image data at ground station.